Solar-Terrestrial Sciences

Solar-Terrestrial Sciences

New insights to the north-south asymmetries of auroral features

New insights to the north-south asymmetries of auroral features

Recent research on the simultaneous displays of aurora in both hemispheres have lead to new knowledge of how large-scale asymmetries in the global magnetic field configuration can arise and be mitigated. This new understanding is contrary to what has been the consensus in the field, and was recently highlighted in a press release from the American Geophysical Union, followed by attention from numerous newspapers and magazines world wide.

These new results, published in a series of papers since 2015 [1,2,3,4,5,6], represents a paradigm shift in the explanation of the processes controlling how the magnetosphere twists around the Sun-Earth line. It has been known since the 1980’s that when the Interplanetary Magnetic Field (IMF) has a dawn-dusk component (By), the closed field lines inside the magnetosphere also develop a By in the same direction as the IMF. This has usually been explained by means of tail reconnection, a process that would allow field lines from each hemisphere to meet and produce new closed field lines, now being asymmetric. However, the new results show that the asymmetry of closed field lines, as highlighted by the aurora in one hemisphere being longitudinally displaced to its counterpart in the opposite hemisphere, start to emerge within 10 minutes. This is a much shorter response time than what can be explained by the the tail reconnection scenario. Furthermore, the highlighted studies also show that the process of tail reconnection actually act to reduce the longitudinal displacement of the northern and southern aurora. This is exactly opposite to the understanding that has been the consensus in the community, hence the importance of these results. In the AGU press release, editor-in-chief of JGR-Space Physics, Mike Liemohn, says: “This study explains both how asymmetries are created and how it is removed and it is exactly opposite of what I and many researchers have thought. Therefore, this result is kind of big deal.”

Director of the Birkeland Centre for Space Science and leader for the research group presenting the new findings, Nikolai Østgaard, says: “We are very satisfied with how the AGU Press Release turned out for us. As we speak, 104 newspapers and magazines worldwide has picked up the story. We could not have hoped for a wider impact among the public about our results.”

Along with the press release, the research group at the Birkeland Centre for Space Science  prepared an animation of the processes leading to the longitudinal displacement of the aurora between the two hemispheres. This can be seen in the video below.


A more in-depth explanation of the mechanism can be seen in the video below where PhD candidate Anders Ohma, lead author of the JGR paper highlighted in the AGU press release, explains the physics behind the longitudinal displacement of the aurora between the two hemispheres.



[1] Tenfjord, P., Østgaard, N., Snekvik, K., Laundal, K. M., Reistad, J. P., Haaland, S., & Milan, S. E. (2015). How the IMF By induces a By component in the closed magnetosphere and how it leads to asymmetric currents and convection patterns in the two hemispheres. Journal of Geophysical Research: Space Physics, 120.

[2] Reistad, J. P., Østgaard, N., Tenfjord, P., Laundal, K. M., Snekvik, K., Haaland, S., … Grocott, A. (2016). Dynamic effects of restoring footpoint symmetry on closed magnetic field-lines. Journal of Geophysical Research: Space Physics, 121, 1–14.

[3] Tenfjord, P., Østgaard, N., Strangeway, R., Haaland, S., Snekvik, K., Laundal, K. M., … Milan, S. E. (2017). Magnetospheric response and reconfiguration times following IMF By reversals. Journal of Geophysical Research: Space Physics, 122(1), 417–431.

[4] Reistad, J. P., Østgaard, N., Laundal, K. M., Ohma, A., Snekvik, K., Tenfjord, P., … Haaland, S. E. (2018). Observations of asymmetries in ionospheric return flow during different levels of geomagnetic activity. Journal of Geophysical Research: Space Physics.

[5] Østgaard, N., Reistad, J. P., Tenfjord, P., Laundal, K. M., Rexer, T., Haaland, S. E., … Ohma, A. (2018). The asymmetric geospace as displayed during the geomagnetic storm on 17 August 2001. Annales Geophysicae, 36, 1577–1596.

[6] Ohma, A., Østgaard, N., Reistad, J. P., Tenfjord, P., Laundal, K. M., Snekvik, K., … Fillingim, M. O. (2018). Evolution of Asymmetrically Displaced Footpoints During Substorms. Journal of Geophysical Research: Space Physics, 123.

Web-based Tools for Forecasting Solar Particle Events and Flares

Web-based Tools for Forecasting Solar Particle Events and Flares

The presence of Solar Energetic Particles (SEPs) poses a serious health risk to humans in space, can result in increased radiation doses for high-latitude aircraft flights and constitutes a serious hazard for the micro-electronics and other hardware elements of satellites, aircraft and launchers. These groups of end users need reliable forecasts of possible enhancements in the radiation flux level, days beforehand, in order to plan flights, operations and EVAs (extra-vehicular activities).

Enhancements of SEP fluxes result from explosive phenomena in the solar corona; these enhancements are known as Solar Particle Events (SPEs). There are two phenomena known to contribute to SPEs namely, Solar Flares and Coronal Mass Ejections. CME-driven shocks might be the key driver but Solar Flare forecasting is much more advanced and SPEs driven by shocks normally have associated flares.

The last five years the Space Research and Technology Group of the Institute for Astronomy, Astrophysics, Space Applications & Remote Sensing (IAASARS), of the National Observatory of Athens (NOA), has been involved in the development of new techniques and in the operation of web based tools, to provide reliable Solar Particle Events and Flares predictions.


The FORSPEF (FORecasting Solar Particle Events and Flares) tool was developed with funding from ESA’s Technology Research Programme (ESA Contract No. 4000109641/13/NL/AK).  In Figure 1 a summary of the operation capabilities of the FORSPEF tool is presented (for more details see Anastasiadis et al., 2017).

Figure 1: A summary of the operational capabilities of the FORSPEF Tool


The FORSPEF tool is a prototype system that consists of three modules that aim to forecast i) the likelihood of upcoming solar flare eruptions, ii) the occurrence of Solar Energetic Particle (SEP) events by making a prediction of the time before onset, and iii) the SEP characteristics for an upcoming event, respectively. Additionally, FORSPEF incorporates two operational modes, the forecasting and the nowcasting mode. The former is understood as the pre-event mode, since no actual solar event (i.e. SF or CME) has yet taken place. The only available information is the identification of an AR on the Sun and its calculated Beff metric (see Georgoulis and Rust 2007). The latter corresponds to the post-event mode, in which a solar event has actually taken place and its characteristics (for solar flares the longitude and the magnitude, and for CMEs the width and the velocity) are available.

The solar flare forecasting module delivers conditional flare probabilities complemented by information on CME probabilities and expected CME speeds. The prediction of SFs relies on the effective connected magnetic field strength (Beff) metric, which is based on an assessment of potentially flaring AR magnetic configurations, and it uses a sophisticated statistical analysis of a large number of AR magnetograms. CME probabilities and projected speeds are based on the peer-reviewed published flare-to-CME association rates (Yashiro et al., 2005) and on the statistical correlation between Beff-values and recorded near-Sun CME velocities (Georgoulis, 2008), respectively. For each identified solar AR, the output of the FORSPEF flare forecasting module is a structure containing the AR NOAA number, its location, the corresponding Beff value, the 24-hour cumulative flare probabilities for each of the 28 GOES flare classes (from C1.0 to X10.0) and their peak photon fluxes (PPFs), the respective eruptive-flare or CME likelihoods, and the projected CME velocity. The SF forecasting produces histogram curves of the cumulative flare probabilities and CME likelihoods versus the flare PPF. The cumulative forecast probabilities for flares and CME likelihood for a sample AR are shown in Figure 2.

Figure 2: Pictorial output of the FORSPEF solar flare forecasting and likelihood of CME

For the prediction of SEP events, new statistical methods have been developed. These are based on a comprehensive database of SFs, CMEs and SEP events (Papaioannou et al., 2016). In the forecasting scheme, the FORSPEF tool provides the probability of SEP occurrence based on the information delivered by the solar flare forecasting. The kernel of the SEP prediction is based on the probability of SEP occurrence per solar flare magnitude which is derived from a historical sample of 4000 flares. These probability values are used to implement a local SEP statistical model via distribution functions. The FORSPEF tool in this forecasting scheme provides a weighted forecast for the expected occurrence of an SEP event per AR, calculated as the product of the local SEP module and the cumulative SF probabilities. The output of the SEP forecasting scheme is the maximum probability for each of the considered ARs (Papaioannou et al., 2015; Anastasiadis et al., 2017).

Figure 3: Pictorial output of the FORSPEF of the probability of SEP occurrence as a function of Solar flare flux and longitude

FORSPEF’s nowcasting scheme can be considered as the short-term forecasting that is triggered by a solar eruptive even. FORSPEF has developed two operational nowcasting modules –one that is based on near real-time solar flare information (longitude, magnitude) and another module that makes use of near-real time coronal mass ejection – CME data (width, velocity). For the first operational module the inputs of the FORSPEF nowcasting work-scheme are in practice the maximum flare flux and its position (longitude) on the visible part of the solar disk. FORSPEF makes use of all ≥C1.0 flares. For the second operational module the nowcasting scheme uses the near real-time outputs provided online through the computer-aided CME tracking software (CACtus), operated by ROB. Further details on this module are presented in the recent work of Papaioannou et al. (2018).

The FORSPEF tool has been released on April 06, 2015 and has been in continuous operation ever since. The FORSPEF system is registered to the SEP Scoreboard Challenge of the Community Coordinated Modeling Center (CCMC) of NASA. It is available online at and provides continuous forecasts and nowcasts of SFs and SEP events. All outputs can be freely accessed and used by the scientific community.

The ASPECS activity

The ASPECS (Advanced Solar Particle Event Casting System) tool is currently under development by a consortium headed by the Space Research and Technology Group of the IAASARS/NOA, with funding through the ESA Contract No 4000120480/17/NL/LF/hh “Solar Energetic Particle (SEP) Advanced Warning System (SAWS)”. The consortium consists of an SME, SPARC (Greece); the University of Turku (Finland); the Universitat de Barcelona (UdB) and the Belgian Institute for Space Aeronomy (BIRA-IASB).

Figure 4: The ASPECS logo

ASPECS will collate and combine outputs from different modules providing forecasts of solar phenomena, solar proton event occurrence and solar proton flux and duration characteristics; tailored to the needs of different spacecraft and launch operators, as well as the aviation sector. The predictions shall start with the solar flare forecasting and will continuously evolve through updates based on near-real time inputs (e.g. solar flare and coronal mass ejections data/characteristics) received by the system. User requirements include a derivation of energies and thresholds important for different user-groups and warning levels. In addition, for the first time the complete time profile of the SEP event at respective energies shall be provided in near real-time, utilizing both simulations and observations.  More info and updates on the current activity can be found at


This post is written by:

Dr. Anastasios Anastasiadis

Research Director

National Observatory of Athens

Institute for Astronomy, Astrophysics, Space Applications & Remote Sensing

FOXSI: The NASA mission that combines rockets, flares, and X-rays

FOXSI: The NASA mission that combines rockets, flares, and X-rays

For decades, high-energy aspects of the Sun have been studied using indirect imaging and spectroscopy in hard X-rays (HXR) by the pioneering RHESSI spacecraft. However, advanced understanding of small-scale energy releases and particle acceleration in the outermost layer of the Sun require better sensitivity and dynamic range, which can be achieved by using direct focusing X-ray optics. Almost six years ago, in 2012, the Focusing Optics X-ray Solar Imager (FOXSI) rocket experiment first imaged the Sun in hard X-rays (4 – 20 keV) using direct focusing optics, from an altitude of about 300km. The second flight in 2014 made striking observations such as the evidence for the existence of solar nanoflares from a non-flaring active region [1] and plasma temperature distribution of microflares.

The Terrier/Black Brant IX rocket successfully launched FOXSI-3 to observe the X-ray Sun, Sep. 7, 2018 from Launch Complex 36 at White Sands Missile Range, New Mexico.

On 7 September 2018, team FOXSI launched its third successful flight from White Sands Missile Range (WSMR), New Mexico. FOXSI-3 flight also served as a test bed for advanced space instrumentation such as
(i) ‘3D printed collimator’ to block X-rays coming off the coverage area,
(ii) fine pitch CdTe strip detectors, and
(iii) Soft X-ray (SXR) capability to our telescope using CMOS sensors.

To focus X-rays, the team uses extremely polished surfaces called ‘X-ray mirrors’, fabricated and calibrated at NASA Marshall. FOXSI uses 7 optic modules, with each containing nested X-ray mirrors, coated with Iridium. Photons hitting at grazing angles (less than 0.5°) get reflected to a focal point from where they are imaged using photon counting energy sensitive semiconductor detectors made of Si and CdTe. The flight optic modules were calibrated using the Stray Light Facility at NASA Marshall. The blocking performance of 3D printed collimator and blockers were well tested and duly validated with ray tracing simulations. The HXR detectors were calibrated at the University of Minnesota, while operating at -10°C using a well tailored temperature controller that met all the requirements for a controlled cooling and warming up. Our Japanese collaborators provided the PhoEnIX (Photon Energy Imager in X-rays) instrument, which added soft X-ray capability to the FOXSI-3 experiment by observing in the 0.5 – 5 keV using CMOS sensors. The solar alignment aspect system was developed and tested at NASA Goddard.

Happy FOXSI-3 team after passing all the required tests and got a nod to go ahead for launch!

Mechanical fit checks and optics alignment tests were conducted at SSL, Berkeley before shipped to WSMR. We spent weeks of tireless teamwork and carried out all necessary checks, with proper breaks for outing and cooking! We started our launch day at 2.30AM by kicking our cooler to ramp down to -20°C, while we rejoiced yummy donuts, cookies and coffee. Watched the impressive launch, steered our telescope for ~ 6 minutes and observed the X-ray Sun!

Simultaneous imaging and spectroscopy of the Sun in SXR and HXRs using direct focusing optics and photon counting detectors have never been done before! FOXSI-3 demonstrates the technology readiness and robustness available for a future dedicated solar HXR space observatory to study the high-energy phenomena with intricate details. This will unavoidably broaden the horizons of the solar and heliospheric community. Preliminary results from FOXSI-3 will be discussed in the American Geophysical Union Fall Meeting in December 2018.

[1] Detection of nanoflare-heated plasma in the solar corona by the FOXSI-2 sounding rocket, S. Ishikawa, L. Glesener, S. Krucker, S. Christe, C. Buitrago-Casas, N. Narukage, J. Vievering, Nature Astronomy, 2017



This post is written by Subramania Athiray Panchapakesan
from the FOXSI team working in the University of Minnesota

EGU for Early Career Scientists

EGU for Early Career Scientists

Theresa Rexer

This months post is written by the ST Divisions Early Career Scientist representative, Theresa Rexer.

Are you ready for the EGU general assembly 2019? Got your abstract ready and submitted? No, what? Too early you say? No funds? As your Early Career Scientist Representative, let me tell you why now is the perfect time to start planning your trip to Vienna in April next year. Especially if you are an Early Career Scientist!

EGU2019 aka the best meeting for Early Career Scientist in geosciences
At the general assembly (GA) more than half the participants are actually early career scientist  which is defined as students at all stages or scientist who have finished their MSc or PhD within the past 7 years. Because of this, a large effort is made every year to make the meeting especially relevant for ECSs. There are numerous Short Courses that are specifically organised for ECSs. Want to know how others find their way around the huge conference site? Or how you can get the most out of you next poster or PICO presentations? The short courses are sessions or workshops that are complementary to the scientific talks at the GA , ranging from a host of general topics like visualising your research, how to navigate the GA or How to get your next job or research grant in academia that are relevant to all ECSs, to division specific topics where you can get an introduction to topics and technics specific to a field of research. 
In the Short course of the Solar-Terrestrial division, SC3.7/ST4.11: Meet the experts: The future of Solar terrestrial Research, you will get a unique chance to discuss the future challenges and opportunities with experienced and renown scientists in our field. You have heard of them. You might have read their papers. Now is your chance to talk to them and ask: What’s next for us
You can also meet your fellow ECSs, your future friends and colleagues, at one of the many social events like the Early career Scientists reception, the ECS forum meeting or in the ECS Lounge area, where free coffee and soft drinks are served and a series of pop-events for ECSs are held during the week. 
Still unsure and none of your colleagues are going? Consider signing up for the mentoring programme where ECSs are matched with a senior scientist to help you navigate the conference, network with other conference attendees, and exchange feedback and ideas on professional activities and your career development.
“So why plan now? The deadline isn’t until January…”
Did you know that, as an ECS, you can apply for travel support? If you submit your abstract by December 1st 2018, you registration fee and travel expenses for up to 300 Euro could be covered for you. All you have to do is write and submit your abstract before December 1st and apply for the Early Career Scientist Travel Support. This is a great opportunity and December is closer than you think, so don’t wait. Submit your abstract, apply for support and get ready for next years best early career scientist conference. 
Not an ECS? The early bird still catches the bird….or the medal! The Vienna City Marathon (also includes a half-marathon and 10k runs) is held the weekend just before the GA and tickets are sold fast. You are correct in thinking that a number of your fellow ST division scientists and ECSs are participating, so join us!
If you have any questions, suggestions, ideas or if you wish to join the Solar-Terresrial ECS Team, do not hesitate to contact me at
See you in April!
– Theresa

A close-up journey to the Sun: The Parker Solar Probe Mission

A close-up journey to the Sun: The Parker Solar Probe Mission

Almost two months ago, in August 12, 2018 Parker Solar Probe (PSP) launched by NASA on a Delta IV Heavy rocket from Cape Canaveral, Florida. This is a long-awaited mission from the Heliospheric community. The first to explore the Sun within distances of ~0.167 AU (or 25 million kilometers) at its perihelia. Its ancestors were the successful Helios -A and -B spacecraft, a pair of probes launched into heliocentric orbit for the purpose of studying solar processes, that orbited our star as close as 0.29 AU (or 43.432 million kilometers). However, PSP is a truly historic mission since it will scan – for the first time  – the actual atmosphere of the Sun, the corona. In turn, this will unavoidably broaden the horizons of the solar and heliospheric community, for the simple reason that we will go where we have never been before: to our home star. Thereby, all studies and concepts; all debates and different points of view will be validated and cross-compared giving ground to new knowledge !

The United Launch Alliance Delta IV Heavy rocket launches NASA’s Parker Solar Probe to touch the Sun, Sunday, Aug. 12, 2018 from Launch Complex 37 at Cape Canaveral Air Force Station, Florida.
Credit: NASA / Bill Ingalls

NASA named this mission after Eugene Parker, in order to honor his radical and at the same time fundamental contributions that revolutionized our understanding of how the Sun’s emissions affect our solar system through the solar wind.

The PSP mission exhibits a unique orbit. It utilizes the gravitational assist from Venus flyby for 7 times within a six-years duration (2025), leading to 24 perihelia. Each pass leads to a gradual “walking in” toward the Sun. The first flyby from Venus took place earlier this month (October 03, 2018) and the first perihelion will take place in less than two weeks time (November 06, 2018) making the Heliophysics community being in alertness, tuning in for the first ever close-up of the Sun’s surface !

Last month, in early September, each of PSP’s instrument suites powered on and returned their first observations on the spacecraft’s journey to the Sun. Although the data are not representative examples of the key science observations that shall be delivered by PSP, once the spacecraft is closer to the Sun, they demonstrated that all instruments are working well and that everything is properly set for the first rendezvous with our star !

The right side of this image — from WISPR’s inner telescope shows Jupiter in the distance (the bright object on the right). The left side of the image is from WISPR’s outer telescope that captured the Milky Way. Credit: NASA/Naval Research Laboratory/Parker Solar Probe

Following PSP, ESA is scheduling the launch of Solar Orbiter (SolO), currently foreseen for 2020. SolO will use gravity assists from Venus and Earth in order to get into a 168-day-long orbit around the Sun. SolO will get, up until a distance of 0.28 AU from the Sun, every five months. In the course of the mission, additional Venus gravity assist manoeuvres will be used to increase the inclination of SolO’s orbit, helping scientists to view for the first time the polar regions of the Sun clearly from an angle higher than 30 degrees. Thereby, the coordinated science objectives and the conjunction periods of SolO with PSP promote them to natural alleys working on the exploration of the Sun.

It seems that we are living in a golden age for the Heliospheric physics !

Cosmogenic Radionuclides – The quest of studying the solar activity of thousands of years

Cosmogenic Radionuclides – The quest of studying the solar activity of thousands of years

Thanks to the invention of the Neutron Monitor in 1948 and multiple spacecraft which monitor the cosmic ray environment since 1970’s we now have a constant record of the solar activity over almost 70 years. Information prior to this space era, however, are rare and take us back in time only to the late 1930s, when ionization chambers have been introduced. This of course allows us only a narrow view on the solar behaviour compared to the age of the Sun and our solar system and big scientific questions concerning, e.g., the current solar cycle can not be answered as easily. However, because galactic cosmic rays interact with the surrounding atmospheric constituents once they enter the atmosphere they are also able to induce the production of so-called cosmogenic radionuclides such as 10Be, 14C and 36Cl, with half-life times of up to 1.39 million years. Luckily, once mixed in the Stratosphere and Troposphere, these radionuclides get attached to aerosols and therewith transported to the surface. Here they are deposited in natural archives like ice sheets, tree rings or sediments, where the information of the solar activity is stored. Thus, cosmogenic radionuclides offer the unique possibility of obtaining a solar activity record over thousands of years. However, although cosmogenic radionuclide measurements can, thus, in principle be used to reconstruct solar activity back in time, in order to understand the underlying physical processes as detailed as possible the production of the cosmogenic radionuclides has to be studied numerically. As shown in Fig. 1, thereby a variety of complex physical processes has to be addressed, starting with the particle population of galactic cosmic rays in the local interstellar medium, their modulation within the heliosphere, their transport in the Earth’s magnetosphere as well as their interaction within the terrestrial atmosphere.

Prior to the end of 2012 the unmodulated galactic cosmic ray (GCR) flux, also known as the local interstellar spectrum (LIS), had not been measured in-situ. But with Voyager I crossing the outer heliosphere at around 122 AU for the first time measurements of the low energy LIS (below ~500 MeV) became available and the existing models on the production of cosmogenic radionuclides had to be revised.

Once GCR particles enter the heliosphere they encounter the heliospheric magnetic field (HMF) which is carried outwards by the solar wind. Thereby, the lower energy GCRs are modulated as they traverse the HMF. This transport can be described by the Parker transport equation, taking into account five important terms: the outward convection by the solar wind, gradient and curvature drifts in the global HMF, the diffusion through the irregular HMF, adiabatic energy changes due to the divergence of the expanding solar wind, as well as local sources (e.g., particles accelerated at the Sun). However, most often the much simpler analytical force-field approximation, which depends only on the solar modulation parameter Φ, is used in the literature. Furthermore, nowadays instruments like, e.g., PAMELA and AMS02 measure the high-energy GCR component above 10 GeV in the Earth’s vicinity, which is not influenced by the modulation due to the HMF. The energy spectrum of the energy range most important for the production of the cosmogenic radionuclides (0.4 – 8 GeV), however, is still unknown.

Figure 2: Upper panel: Annual variations computed with the IGRF model. Shown is the difference between the cutoff rigidities as they were present in 1900 and the ones of 2016. Lower panel: Comparison of the paleo-geomagnetic field reconstructions by different groups relative to present magnetic field strengths. Courtesy: K. Herbst

The HMF, however, is not the only magnetic filter that CRs encounter on their way to the Earth’s atmosphere. The Earth’s magnetic field also plays a major role when it comes to the modulation of the CR spectrum on top of the atmosphere. Although low- as well as high energy particles can enter the atmosphere at polar regions only high energy CRs can do so at equatorial regions. There is, however, not only a spatial but also temporal variation that has to be addressed. These changes can be of short term, e.g. due to a strong solar particle events, on the basis of annual variations (see upper panel of Fig. 2) but also centennial time scales (see lower panel of Fig. 2). Thus, such changes influence the primary particle spectrum on top of the atmosphere, and therewith the production of 10Be, 14C and 36Cl.

The main motor for the production of 10Be, 14C and 36Cl are galactic cosmic rays (GCRs) consisting of ∼87% protons, ∼12% alpha particles and ∼1% heavier particles (see e.g. Simpson, 2000). Once inside the Earth’s atmosphere CR induce the evolution secondary particle cascades of  muonic, electromagnetic as well as hadronic origin. In particular the high energy secondaries of the latter are able to further interact with the atmospheric Nitrogen, Oxygen and Argon atoms due to spallation reactions as well as thermal neutron capture producing the terrestrial 10Be, 14C and 36Cl isotopes. Thus, there is a clear anti-correlation to the solar activity. As a consequence, during high solar activity the production of cosmogenic radionuclides is low, and vice versa.

After stratospheric- and tropospheric mixing on time-scales in the order of around two (10Be) up to twelve years (14C) cosmogenic radionuclides are being attached to aerosols and finally deposited in natural archives like ice sheets, tree rings or sediments, where the information of the solar activity of thousands of years is stored. Existing radionuclide records thereby showed that GCRs most likely are not the only CRs contributing to the production of cosmogenic radionuclides. Recently, unexpected production rate increases around 774/5 AD and 993/4 AD in all three records were observed. This started a fruitful scientific debate about the causes of such strong increases. With a multi-radionuclide approach of highly resolved 10Be records combined with 36Cl ice core data, in 2015 different scientific groups independently could infer that enormous solar eruptions were the most likely causes behind the observations.

By combining numerical modelling and observations it is possible to reconstruct the solar activity (in form of the solar modulation parameter Φ) back in time. A reconstruction based on 10Be records by Muscheler et al. (2007) is shown in Fig. 3. Amongst others, thereby the reconstruction strongly depends on the LIS model the numerical simulations are based on.

Figure 3: Reconstruction of the solar modulation parameter from 10Be measurements based on Muscheler et al. (2007). Courtesy K. Herbst

Nevertheless, one feature can be seen in all records: the so-called Grand Solar Minima, in which the Sun showed unusually long solar minimum activity over tens of years. Shown here are the reconstructions between AD1000 and AD2005, where six of these minima have occured: Gleisberg (1880-1914), Dalton (1790-1820), Maunder (1645-1715), Spörer (1450-1550), Wolf (1280-1350) and Oort (1040-1080). This immediately implies that the low solar activity observed in the current solar activity cycle is not that uncommon, and that we are well within another small Grand Solar Minimum (referred to as Eddy Minimum).

Figure 4: Comparison of the 14C – based solar-modulation parameter with the revised sunspot (light blue) and group sunspot (blue) numbers. All records show an running 11-year average. The red curve shows the 4C (neutron monitor)-based results of the numerical production calculations. Courtesy K. Herbst


In order to test the results a comparison of the reconstructed solar modulation parameter values with the sunspot number, which is a direct measure of the solar activity, can be performed. As can be seen in Fig. 4, a reasonably good agreement can be found. Furthermore, because the solar modulation parameter mathematically can also be linked to the HMF it is also possible to reconstruct the heliospheric magnetic field strength back in time and compare actual observations with geomagnetic-, sunspot number- as well as 10Be-/14C- based reconstructions. As can be seen in Fig. 5 an impressive correlation between the different records has been found.

Figure 5: Composite plot of the reconstructed heliospheric magnetic field strength from 1390–2016 based on cosmogenic 10Be (McCracken and Beer 2015; 1391–1748), 14C (Muscheler et al. 2016; 1390–1748), the sunspot number (Owens et al. 2016a; 1749–1844), geomagnetic data (Owens et al. 2016a; 1845–1964), and from near-Earth observations in space (1965–2016). Courtesy K. Herbst


For more background information the reader is referred to the publications by: 

Beer, McCracken and von Steiger, Springer Business & Media (2012),

Muscheler et al. (2016), Solar Phys.,

Cliver and Herbst (2018), Space Sci Rev, 214:56,


This post was writtend by Dr Konstantin Herbst

Dr Konstantin Herbst from the Christian-Albrechts-Universität zu Kiel, Germany

SunPy: a Python solar data analysis environment

SunPy: a Python solar data analysis environment


For many years now we know that our star the Sun influences the Earth in many different ways, via the total solar irradiance, solar energetic particles and coronal mass ejections. Understanding the influence of the Sun on the Earth requires many different types of measurements. For example, NASA’s Solar Dynamics Observatory (SDO) spacecraft, produces over 1 terabyte of data per day (Pesnell et al., 2012), the bulk of it in the form of 4096 by 4096 pixel images in multiple bandpasses. The Parker Solar Probe (launched 12 August 2018) will fly closer to the Sun than any previous spacecraft, exploring the Sun’s corona, the solar wind and source and transport of space weather phenomena, by taking both in situ and remote measurements. Understanding the underlying physics requires sophisticated data analysis and modelling of multiple differing physical domains.

Managing and analyzing these heterogeneous data to answer evolving scientific needs and questions requires increasingly sophisticated software tools. These tools should be robust, easy to use and modify, have a transparent development history, and conform to modern software-engineering standards. The SunPy Project (SunPy Community et al., 2015) aims to provide a free and open source software package with these qualities for the analysis and visualisation of solar data. SunPy is built on Python, a free, general-purpose, powerful, and easy-to-learn programming  language. Python is widely used in many scientific fields, and has found applications in data analytics, machine learning and educational environments. SunPy brings solar physics in to the scientific Python ecosystem.

Organization and description of the code

Figure 1: SunPy is used to overlay two maps of data taken at the same time during the total solar eclipse of August 21, 2017: a ground-based photograph of the corona (black/white image), and an extreme ultraviolet image of the disk of the Sun (yellow image) taken by the SDO Atmospheric Imaging Assembly. Courtesy of S. Christe.

SunPy focuses on providing access to online repositories of solar physics data, and objects that make it easy to manipulate and display those data. SunPy is built using other open source Python projects, notably Astropy, numpy, SciPy, pandas and matplotlib. For example, many solar datasets are two-dimensional images, represented in SunPy by a Map object. Maps use SunPy’s coordinate transformation framework, an extension of Astropy’s powerful coordinates package, thereby enabling support for transforming between all Astropy and SunPy coordinate systems. SunPy was used to overlay ground based images of the solar corona taken during the total solar eclipse of August 21, 2017, and space based-images taken by SDO (Figure 1)


Figure 2: SunPy’s example gallery.

Figure 3: Simulated coronal loop emission generated using SunPy. Courtesy W. T. Barnes.

SunPy’s also provides the TimeSeries object for manipulating and displaying time-ordered scalar data.  Also, all public-facing SunPy functionality is unit-aware, meaning that physical units must be specified as required.  SunPy provides code snippets to get users started (Figure 2), and project members are active in teaching the community about SunPy.  SunPy is used by researchers working at NASA, European Space Agency (ESA), and the US National Solar Observatory Daniel K. Inouye Solar Telescope.  SunPy can also be used for modelling work: Figure 3 shows an example of using SunPy’s coordinate and mapping abilities to model the emission from an arcade of solar coronal loops.


Governance and development model

SunPy was born at the 2010 Solar Image Processing Workshop in Les Diablerets, Switzerland.  It is run by a small volunteer board of scientists that sets SunPy’s goals.  The Lead Developer (currently Dr. Stuart Mumford) is responsible for the implementation of SunPy’s goals. Contributions can be made by anyone. The project is managed at, and unit testing, continuous integration, and community review of contributions are implemented to reduce bugs and maintain quality.  Students supported by the Google Summer of Code and the ESA Summer of Code in Space programs have made substantial contributions to SunPy.  The SunPy project is also a member of NumFOCUS, a US-based nonprofit organization that promotes sustainable high-level programming languages, open code development, and reproducible scientific research.


SunPy gives users access to the ever widening scientific Python ecosystem. SunPy 1.0 is under development for release later on this year. This version will use Astropy’s representation of time, bringing improved precision and leap second support to SunPy.  The usability of SunPy’s data acquisition infrastructure will also be improved.  SunPy 1.0 will also drop support for the Python 2 series and require Python 3.6 or higher.  SunPy is also developing NDCube, a multi-dimensional, physically aware data object that can represent more complex multi-dimensional datasets, such as that from NASA’s Interface Region Imaging Spectrometer (IRIS) and other spectrometer instruments.  Finally, SunPy’s affiliated package program encourages the development of SunPy-based code that performs specific scientific tasks such as analyzing solar radio spectra.


SunPy Community, S.J. Mumford, S. Christe, et al. 2015, Computational Science and Discovery, 8, 014009.

D. Pesnell, B. J. Thompson, and P. C. Chamberlin. The solar dynamics observatory (SDO). Solar Physics, 275:3–15, Ja

Jack Ireland, lead support scientist at NASA/GSFC and Communications Officer for SunPy Project

nuary 2012.


This blogpost is written by Jack Ireland from the SunPy Community

Jaime de la Cruz Rodriguez – ERC success in the field of solar physics

Jaime de la Cruz Rodriguez – ERC success in the field of solar physics

Coronal Heating Problem is one of the Sun’s unsolved mysteries where the corona is heated to over a million degrees and scientists have not figured out where the energy is coming from. Dr Jaime de la Cruz Rodriguez is tackling this 70 year old puzzle by first understanding the layer of the Sun below the corona – the chromosphere. He is awarded the prestigious starting grant by the European Research Council for his project SUNMAG: Understanding magnetic-field regulated heating and explosive events in the solar chromosphere.


Congratulations on your ERC fellowship! Tell us about the man behind the grant?

Thanks! I am a solar physicist from Spain now established at Stockholm University. I moved to Sweden from the Canary Islands in 2006 as a PhD student, that was quite a life change! I chose solar physics as a PhD topic because our proximity to the Sun allows us to apply very advanced techniques that are usually not possible with more distant astrophysical objects. I got the chance to move to Sweden in a moment when they had the largest solar telescope in the world, and it was a very attractive option. At a more personal level, I wanted to leave from Tenerife for some time, and Sweden looked like an exotic adventure at the time. But it turned out to be a new life for me: there I met my wife and we have two kids. After my PhD studies I had postdoc positions at University of Oslo and Uppsala University, where I worked with brilliant colleagues. Since 2014 I have worked in Stockholm University and nowadays I supervise 3 PhD students and 4 postdocs (including those from the ERC project).

Who/what do you give biggest credit for your success with the ERC grant and why?

ERC grants are awarded to scientists that have a very good idea to attempt making progress in a research field. Finding that idea and motivating why it is unique is not always an easy task. In summer 2016 our Institute installed a new instrument (CHROMIS) at the Swedish 1-m Solar Telescope, which allows observing the upper layers of the solar chromosphere with unprecedented spatial resolution (~75 km on the surface of the Sun). Back then, I realized how much potential these new data had. I wrote the proposal around this new instrument and the development of new analysis tools that will allow us to carry out very exciting science in the chromosphere.

Can you briefly describe the SUNMAG project for which you are awarded the prestigious ERC grant in 2017?

The heating of the solar chromosphere remains one of the foremost question in solar and stellar physics: how is energy transported and deposited in this thin layer of the Sun located about the visible surface (the photosphere) and the million-degree corona?
The main obstacle to study this elusive layer of the Sun is that it requires very complex physics to model the observed intensities (spectral lines): it is very challenging to convert the intensities to the underlying physical state of the plasma.

The SUNMAG project will study how the chromosphere is heated in regions with strong concentrations of magnetic field. To do so I have developed a technique that allows to reconstruct a 3D model from our observations. These models contain the stratification of gas temperature, density, velocities and the magnetic field vector with height. I will use these models to study and characterize how the chromosphere is heated in active regions and explosive events like flares. In this region, the magnetic field is expected to play a fundamental role in the structuring and energy transport of the chromosphere.

The reason why this project is finally possible is twofold:
• A new analysis tool that allows reconstructing models from spectroscopic observations (described above) of the chromosphere. While these techniques already existed, for the first time our code allows for the inclusion of spectral lines that are sensitive to the middle and upper chromosphere.
• New instrumentation that allows to spatially resolve the scales at which energy is expected to be released in the solar chromosphere. The CHROMIS instrument at the Swedish 1-m Solar Telescope basically doubles the spatial resolution of previous instrumentation, while also providing rich spectral information.
I believe that with this project I can help to take steps towards solving the chromospheric heating problem.
Just to provide some context, the image illustrates a co-temporal observation of the solar photosphere and chromosphere (top panels), acquired at the Swedish 1-m Solar Telescope. The photosphere (left panel) is dominated by convective cells (granules) and strong concentrations of magnetic field (sunspots). In the chromosphere this convective panel is lost and we start to observe elongated structures that are usually aligned with the magnetic field. We know that in magnetically active regions the magnetic field intensity (generally) decreases as we move upwards. We also know that the magnetic field is highly confined in the photosphere whereas it expands forming magnetic canopies in the chromosphere. These differences are illustrated in the lower panels of the image, where the left panel shows many sharp red structures in comparison with the right panel. In the right panel however, we can discern a green halo in the central part of the image that traces the presence of these magnetic canopies. In the image the red color indicates regions where the magnetic field is aligned with the line of sight of the observer (vertical fields), whereas the green color indicates regions where the magnetic field is contained in the plane of the surface (horizontal fields).

What aspects of the project are you most excited about and what aspects are least exciting?

I am most excited about flare studies. It is a real challenge to understand the observations, but I think we can help a lot as our techniques have not been applied in many studies to this kind of data. This part also has an interdisciplinary component. For example, our code provides estimates of the magnetic field in the chromosphere and that information could be used in other fields like space weather. I am less excited about some programing parts of the project that I will need to undertake. That part is usually less regarding and very time consuming.

In 2017 Stockholm University has bagged 7 ERC grants, including yourself. What does the University do to achieve such success?

Stockholm University is an excellent place to work and perhaps having successful applicants starts by having competitive research groups where those young researchers can develop their ideas and settle with their own groups. Research is very competitive at the moment, but competition used in a constructive way can be a very powerful tool. More pragmatically, I got excellent support during the application process and for the interview in Brussels.

What was the most difficult part of the application process and how did you overcome it?

I personally found the interview part is particularly difficult. I never have had issues with managing my nerves, but that day I didn’t have a steady hand when I entered the room. The panel did a very good job digging out the weaknesses of the project. I managed to overcome this difficult part by not trying to fiercely defend every criticism that I got during the interview. There are always limitations and it is better to be aware of them and to have them somewhat under control.

Apart from your accomplished research, what other duties do you perform? Do you think any of these duties gave you an edge over other applicants during the ERC decision?

Teaching and supervision. The latter is an important asset, especially if the project involves PhD students. I suspect that having zero supervision experience can be problematic in that case.

What are your other interests? How have they been affected since your award?

Professionally I am working in my prime scientific interest, which is great! The award has affected other aspects of my life, including my employment at Stockholm University which is now permanent. Outside science, sports have always been an important part of my life, but that part remains unaffected.

Lots of tips from Jaime for aspiring ERC applicants. Wishing him the very best for this project.

The average magnetic field and polar current system (AMPS) model

The average magnetic field and polar current system (AMPS) model

Karl Magnus Laundal. Credit: BCSS

In this month’s post, Karl Magnus Laundal explains a newly developed empirical model for the full high latitude current system of the Earth’s ionosphere, AMPS (Average Magnetic field and Polar Current System). The model is available and documented in python code, published under the acronym pyAMPS. The community is invited to download and explore the electric currents and magentic field disturbances described by the model.



The average magnetic field and polar current system (AMPS) model

At about 10 times airline cruising altitude, at the boundary to space, the atmosphere is so thin that charged particles, electrons and ions, are not immediately neutralized in collisions. This inner edge of space, which extends from about 100 to 1000 km altitude, is called the ionosphere. In contrast to the neutral atmosphere, the charged particles feel the forces of electromagnetism. These forces depend strongly on the interaction between the solar wind and the Earth’s magnetic field, which happens much further out, at about 10 Earth radii (roughly twice as distant as geostationary satellites, but well inside lunar orbit). The result of this interaction is communicated to the upper atmosphere along magnetic field lines, and as a result, a 3-dimensional current system is generated in the ionosphere. This current system can change very rapidly, partly because of changes in the solar wind and in the interplanetary magnetic field.

Field aligned currents (red/blue) and divergence free horizontal currents (contours) from AMPS, during the course of a day. Credit: K.M. Laundal

The AMPS model describes the average ionospheric magnetic field and current system for a given solar wind speed, interplanetary magnetic field vector, orientation of the Earth’s magnetic dipole axis, and the value of a solar flux index (F10.7). The model is empirical, which means that it is derived from measurements. We use measurements of the magnetic field, from the CHAMP and Swarm satellites, in low Earth orbit. For each measurement, model estimates of Earth’s own magnetic field, and the magnetic field associated with large-scale magnetospheric currents, have been subtracted. The remaining magnetic field is assumed to be related to ionospheric currents. Millions of measured magnetic field vectors are used to fit several thousand unknown parameters in an intricate mathematical function that describes the ionospheric magnetic field at any point in time and space. Electric currents are calculated from the magnetic field.

Model values of AMPS magnetic fields and currents can be calculated with the Python library pyAMPS, which is located here: (documentation here:

This is not the first empirical model of ionospheric currents and magnetic fields, but there are a couple of important characteristics that sets the AMPS model apart from others: First, we have corrected for variations in Earth’s own magnetic field, which strongly distorts the ionospheric currents. This allows us to make precise comparisons between hemispheres. We have not imposed any symmetries between hemispheres; for example seasonal variations are not necessarily the same in the north and south in the AMPS model. Finally, this is the first empirical model to describe the full ionospheric current system, and not only the field-aligned part or the parts which circulates horizontally. This allows us to calculate full horizontal ionospheric current vectors without any assumptions about conductivity.

These unique features are made possible by the dataset provided by the CHAMP and Swarm missions, of very accurate magnetic field measurements from low orbit. The CHAMP satellite reentered Earth’s atmosphere in 2010, after 10 years of operation. In 2013, ESA’s Swarm satellites were launched, three satellites that carry even more precise magnetometers than CHAMP. So far, two of the Swarm satellites have flown side-by-side, near 450 km altitude, while the third satellite is a little higher. Swarm is expected to stay in space for many years, and we plan to release updated versions of the AMPS model as the data set grows. The production and publication of the AMPS model is supported by ESA through Swarm DISC.

A paper describing the model has been published in Journal of Geophysical Research – Space Physics: (open access)

For more background on the technique, see an earlier paper in a special Swarm issue of Earth, Planets, and Space: (open access)

Prof. Ilya Usoskin – A discussion with an inquiry mind

Prof. Ilya Usoskin – A discussion with an inquiry mind

In the May issue of the Life of a Scientist we have the pleasure to talk to Prof. Ilya Usoskin from the Univeristy of Oulu, Finland. Among numerous things, he is the head of the Oulu Cosmic Ray station and receipent of this year’s Julius Bartels EGU Medal; a decision that was based:  “on his contributions to the understanding of the heliosphere, long-term changes in the solar activity and solar-terrestrial relations”.

Prof. Usoskin, can you please introduce yourself ?

I am a Russian-born and -educated scientist living and working in a quiet and charming city of Oulu in Northern Finland. In my research I combine both experiment and theory.

Prof. Ilya Usoskin (Credit: Ilya Usoskin)

As an experimentalist, I am the head of a cosmic ray station and operate a ground-based neutron monitor of Oulu, which is recognized as one of the most stable long-running neutron monitors in the world, a muon telescope, and, since 2015, the world’s most sensitive to low-energy cosmic rays neutron monitor on the Antarctic plateau, thanks to hospitality of the Franko-Italian Antarctic station Concordia. As a theoretician, I am focused on cosmic-ray induced effects in the Earth’s atmosphere, including the firstly developed full numerical model of cosmic-ray induced atmospheric ionization. Of course, as rooted in both experiment and theory, I work actively on data analysis and interpretation, with emphasis upon long-term solar and cosmic-ray variability.

You are a recognized expert in cosmic rays, solar-terrestrial relations, neutron monitors and space weather. What got you motivated, in the beginning of your carrier?

If you expect a nice story of a strongly motivated fellow who was developing according to a well elaborated plan, this is not my case. Earlier part of my career was more like a random walk. No focused motivation or conscious choices. Eventually I migrated to the field where there was a large gap, viz. sensitivity of a neutron monitor to solar energetic particles, and I explored this deeper. Then a new gap in the knowledge was found, and another one…

Do you have any analogies to help us understand what you do ?

There is a remote analogy. Imagine, you permanently reside in your homeland and grow crops. Of course, you want to know about the weather – can you thresh the grain today or better wait until tomorrow? You may know some weather lores, e.g., that the red sunset implies a windy day tomorrow, or from the shape and color of clouds you can predict that rain will start soon, and you start stacking the hay… That’s what Space weather does. We study Space climate. Keeping the same analogy, we try to understand the overall long-scale processes driving the everyday weather. We try to estimate the probability of a cold or warm winter to occur this year or a decade ahead. Of course, the exact weather for each particular day next summer cannot be predicted, but a probability of a cold and wet summer to occur can be evaluated.

At the General Assembly in 2018 you have been awarded the prestigious Julius Bartels Medal. Can you please briefly share with us your discoveries that have lead up to this point?

I am not very sure what were the discoveries which lead to the point. In fact, I haven’t made any discovery, but some results are interesting, at least for me. In particular, we were the first who applied a full Monte-Carlo simulation of the nucleonic-muon-electromagnetic cascade, initiated by cosmic ray in the Earth’s atmosphere, to assess the cosmic-ray related effects. Applying this method to cosmogenic isotopes 14C and 10Be, we were able to perform the first quantitative physics-based reconstruction of solar activity on the multi-millennial timescale. We have shown that solar activity was unusually high during the second half of the 20th century, corresponding to a special case of a Grand maximum, but I would not call it a “discovery”. Generally, IMHO, a systematic study leading to a breakthrough in the long-term solar variability was appreciated rather than “discoveries”.

You are considered as a co-founder of Space Climate, can you please explain what that means in greater detail?

Space Climate implies long-term systematic changes in the near-Earth environment. It is more complex than just a temporal average of Space Weather, because in the latter you cannot see slow trend, tendencies. I would rather say that Space Weather is a snap-shot, instant projections of Space Climate. As a long term we mean everything longer than interannual variability (phases of the 11-year solar cycle) and up to millennia.

I would not agree to be regarded as a founder of the Space Climate discipline. The real father of it is Kalevi Mursula, with whom we discussed 15 years ago that the newly emerging concept of Space Weather is missing an important component, viz. long-term variability. To fill the gap, we organized the first International Symposium on Space Climate in Oulu in 2004, which has become the main Space Climate forum. In February 2019, we will conduct, in Canada, the seventh Symposium of the series, which collects ~150 scientists from all over World. We also regularly convene the related sections at COSPAR, EGU and AGU Assemblies.  As an oversimplified analogy, you can study details of summer weather, but then you will be totally surprised during the winter, if you are not aware of different seasons. Most of Space-era data were based during the period of the Modern grand maximum of solar activity, in the second half of 20th century. You can often hear that the Sun is abnormally quiet nowadays. But this is not correct – the Sun is now at its normal moderate level of activity, while it was abnormally active during the previous decades.

Does the future of your research field lie in interdisciplinary synergies and how important is the unrestricted access to data, today?

Exactly ! The future is in inter- and mutli-disciplinary research conducted by teams of experts. This implies the use of different types of data, and free access to level 1-3 data with full metadata is crucial for that. Data of level 0 can be, of course, kept for internal use, but shall be provided to anyone upon request. Unfortunately, the experience shows that errors may occur at any step even with best datasets, and reproducibility of the result is one of the basic principles of doing sciences.

Based on your experience, what scientific questions in your field could be solved in the near-future and why?

We are now approaching the stage when solar variability can be “absolutelyreconstructed from cosmogenic isotopes on the multi-millennial time scale, including individual solar cycles. Previously, only averaged evolution was possible to assess with somewhat “shaky” calibrations. Another very promising idea is to study extreme solar events. Just 6 years ago we could not imagine that a full analysis of strong solar events in the past, before 19th century, is possible. Now we know three such events, and there will be found more, I am sure.

Overall, we will have a quantitative (with higher quality that the sunspot number record on 400 years) record of solar activity over millennia.

What current idea you consider as the most potential ?

Personally, I am most interested now in the extreme solar events. We are close to defining the limit of our Sun in producing such events, and to assessing the probability of their occurrence, which is crucially important for both science, by providing new unique data on solar activity, and space technology and exploration. You would definitely want to know what “worst-case scenario” you may expect from the Sun and what is the probability of this scenario to be played by the Sun during, e.g., a manned mission to Mars. There is a focused research community attacking this problem from different points of view (precise measurements, realistic modelling, sophisticated data analysis), and we will meet in October this year for a dedicated workshop in Japan (supported by Nagoya University)

What would you like to convey to young researchers who want to work in your field?

My message is very simple: Do what you like in the best possible way ! Try to read state-of-the-art works by best scientists and to say “Hey, it’s good, but I can do it better !” – and then just try to do it better !