Solar-Terrestrial Sciences
Athanasios Papaioannou

Athanasios Papaioannou

Athanasios Papaioannou is an Associate Researcher at the National Observatory of Athens (NOA). He works on low energy cosmic rays (CRs) of both galactic (GCRs) and solar (SCRs) origin and uses in-situ plasma measurements to identify the evolution of large scale structures (Interplanetary Coronal Mass Ejections - ICMEs) within the heliosphere, their interaction with GCRs and the resulting Forbush decreases (FDs). Additionally, he analyses and interprets Solar Energetic Particle (SEP) events using both spacecraft and ground based observations. He develops forecasting systems focused on Space Storms and Space Weather with an emphasis on data driven models.

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

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

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 !

Cosmic rays – messengers from space

Cosmic rays – messengers from space

Cosmic rays (CRs), are not actually rays, but highly energetic charged particles of extraterrestrial origin. The life cycle of a cosmic ray particle starts with its birth at some point in the Universe, its travel at nearly the speed of light and finally with its death ( e.g. at a detector). These highly energetic particles strike our planet from all directions and thus provide a constant background. In practice, this means that thousands of cosmic ray particles pass through our bodies every minute, but the resulting radiation imprint is relatively low if we compare this to the natural background radiation.

Sources of CRs, encompass the Sun, our Galaxy and beyond. As a result, these charged particles span almost ~35 orders of magnitude in flux and ~14 orders of magnitude in energy. This, means that we need many different experimental devices (e.g. spacecraft data, neutron monitors, muon telescopes, AMS02, PAMELA, TRACER, IceTop, Pierre Auger Observatory and many more) to capture the entire spectrum of CRs and at the same time this offers many opportunities to evolve our experimental/detection set ups and our understanding.  We measure the energy of CRs in eV (electron-Volt: it corresponds to the energy gained when an electron is accelerated through a potential difference of 1 volt). Based on the energy of CRs, we can identify the origin and map different parts in the spectrum. For example, above a few GeV/nucleon, the energy spectrum of CRs follows a power law proportional to E−2.7. At 1015 eV there is a break in the spectrum, which is typically referred to as the “knee”, below this energy CRs are of Galactic origin. From the “knee” up to 1018 eV the power law falls as E−3.1. A second break in the spectrum occurs at 1018 eV, usually called the “ankle”, where the spectrum flattens. At this energy it is possible that the particles can be of extragalactic origin. The CR spectrum continues up to 1020 eV, which is the current high-energy limit for CR observations.

The spectrum of CRs, denoting the different components and sources (Credit: A. Papaioannou, adopted from the CR spectrum by S. Swordy).

Low energy (up to ~1015eV) Galactic CRs (GCRs) are most likely accelerated in supernovae (SN) shock waves which occur approximately once every 50 years in our Galaxy. GCRs are the only matter originating from outside our solar system that can be studied directly. Thereby, their composition and energy spectra can be used to determine their sources, acceleration mechanisms and transport processes in the Galaxy. However, since CRs are charged particles those are deflected by magnetic fields. This, in turn, obscures the identification of their actual source, since their travel paths have been randomized.

At the same time the Sun is an additional sporadic source of energetic particles, often termed as solar CRs (SCRs) and/or Solar Energetic Particles (SEPs).  These particles are accelerated by shock waves driven by coronal mass ejections (CMEs) traveling through the corona, and by the magnetic energy that is released in solar flares. When a CME occurs 100 million tons of hot coronal gas is suddenly ejected into space at speeds of 1.6 million km per hour. SFs are observed in white light, UV, soft and hard x-rays, gamma-rays, neutrons and radio waves and hence cover the entire electromagnetic spectrum. When CRs penetrate into our solar system, those are affected by the interplanetary magnetic field (IMF), which is  embedded in the solar wind blowing from the Sun. Therefore CRs have difficulty reaching the inner solar system and Earth. Solar activity (and the rate of CMEs and SFs) varies over the 11 year solar cycle, leading to a variation in the intensity of CRs at Earth, in anti-correlation with the solar activity (as represented by the sunspot number). Furthermore, the interplanetary counterparts of propagating CMEs reduce the GCRs flux, leading to a decrease known as the Forbush decrease.

The heliospheric enviroment. Inserts include, an artistic representation of the Sun-Earth relations (Credit: NASA), a solar flare (SoHO/EIT), a coronal mass ejection (SoHO/LASCO), the recent Solar Energetic Particle (SEP) event from 10 September 2017 and the corresponding recordings from spacecraft (GOES) and neutron monitors on the ground (Ground Level Enhancement – GLE; NMDB) (Credit: A. Papaioannou)

If CRs are energetic enough and reach the Earth’s atmosphere, undergo collisions with its atoms and produce a cascade of secondary CR particles that shower down through the atmosphere to the Earth’s surface. These secondary CRs include pions, electrons and positrons. The number of particles that reach the Earth’s surface is related to the energy of the primary CRs that made it to the upper atmosphere. The deeper the particles penetrate into the atmosphere, the more energy they lose.  A SF and/or a CME may result to an intense flux of SCRs, which gives ground to an SEP and when recorded on the Earth’s surface, to a Ground Level Enhancement (GLE).

GCRs, being messengers from space, hold a key for the greater understanding of our universe, since the most exciting frontiers of astrophysics involve physical processes and environments that are not reproducible in the laboratory. In addition, CRs carry information from their interaction with the magnetic irregularities they encounter en route to the Earth and help us track our heliospheric environment. They also quantify the radiation levels encountered by air crews on flight altitudes and by astronauts in space.  

A synthesis of different figures showing the RAD on MSL on the surface of Mars; RAD’s field-of-view and the corresponding parts of the detector, as well as , the historical photo of Victor Hess in a ballon en route to the discovery of cosmic rays (Credit: A. Papaioannou, using figures from this presentation)

In August 2012, 100 years since the discovery of CRs from Victor Hess, the Radiation Assessment Detector (RAD) onboard the Mars Science Laboratory (MSL) measures for the first time CRs on the surface of another planet.

A thrilling new era has already began !


Miho Janvier – The Quest for Solar Storms

Miho Janvier – The Quest for Solar Storms

In this month’s (first ever for our blog) Life of a Scientist interview, we are very happy to talk to Dr Miho Janvier, a Researcher at the Institut d’Astrophysique Spatiale in Orsay (France), whose work has shed some light on the understanding of solar eruptions and coronal mass ejections  (or solar storms) from their birth in the Sun’s corona to their evolution in interplanetary space. Additionally, Miho has actively taken part in Educational & Public Outreach efforts and has co-created an outreach project on Solar Storms using Virtual Reality technology.


Miho, can you please say a few words about yourself?

Miho Janvier (Credit: Miho Janvier)

I am currently working as an associate astronomer at the Institut d’Astrophysique Spatiale in Orsay (France). My main research interests are the understanding of the fundamental mechanisms of how solar flares occur, and how to better characterize the solar storms they send in space. My research work is quite varied, as I get to work with computer simulations as well as space mission data, and for the analytical part, it’s back to pen and paper! I am also involved in the next European Space Agency mission to the Sun called Solar Orbiter: with the team at my institute, we are responsible for the operations that will be carried by one instrument (SPICE) onboard the spacecraft. I also teach at the University and am involved in outreach projects.

What is a “typical” day in the life of a scientist? Describe one of your “usual” days.

It is difficult to describe a usual day because every day happens to be completely different from another! When I am not at a conference, I generally check and answer the most pressing emails in the morning, while my favorite tea is brewing. I would generally dedicate a few hours for research before heading to lunch with my colleagues. I love these moments of socializing, as the rest of the day can be spent alone in front of a computer! Depending on the days, I may have a meeting in the afternoon, either to discuss the preparation of operations on our instrument for the Solar Orbiter mission, or to discuss new outreach projects, or to dedicate some time for the lab communication team, in which I am involved. This is also the time I answer emails that need a longer thinking time.

What do you want to achieve with your research?

First of all, satisfy my inner curiosity about the universe! This is the one reason I wanted to become an astrophysicist in the first place. Funnily, the more research I do, the more questions I have. It is a never-ending process. On a more practical level, I want my research to matter for different reasons. First, to better understand what it means to live in the neighborhood of an active star that is the Sun. Secondly, not only will this help us to build the tools for space weather forecasting that are important for human societies, it will also help us understand how planets in the solar system react to the Sun’s activity. And ultimately, this research will help assess the conditions of life in other star systems too.

Why did you become a scientist and what drew you to this field?

As a child, I was always fascinated by the night sky. But it is not until I turned 9 and discovered the TV show X-files that I became a big fan of aliens. It may sound weird, but that was my first motivation for becoming an astrophysicist! Of course, the word “aliens” may sound like a joke, but in the bigger picture, what I mean is that questioning the existence of life in the universe is, to me, one of the most fascinating questions in life.
Later in my studies, I really liked the aspect of plasma physics, where the behavior of an ionized “fluid” is affected by an electromagnetic field (and I did like working with Maxwell’s equations). I finished my PhD in plasma physics as the space telescope Solar Dynamics Observatory was in its first mission years, sending us extremely detailed images of the Sun and its beautiful eruptions.  It just seemed natural to turn to solar physics!


What advice would you give to your younger self?

To be more confident about yourself, and for this, to build a support network along your career. A few years ago, I came across the expression “impostor syndrome” and realized that the pressure we have, as young scientists, can be daunting. As a woman in science, I also realized along the years that there are still a lot of stigmas and unconscious biases in science that can make you feel like you don’t belong to the field. Creating a network of colleagues, friends (and the two can intersect!) and self-care routines will help you go through the times when you have doubts.

What do you consider as the most surprising result in your research so far?

A few years ago, with the team I was working with at Paris Observatory, we analyzed the mechanisms happening during flares (what we call magnetic reconnection, in three dimensions). We expected a specific behavior of the Sun’s magnetic field in flaring regions from our numerical simulations. This was later confirmed with observations from the Solar Dynamics Observatory space telescope by one of our colleagues, who is indeed a keen observer!

What is it that you like to do when you aren’t working on research

Away from my desk, I love travelling. As a kid, I had the incredible chance to live in several countries on 3 different continents. So I get itchy feet when I am staying too long in the same place. I am just back from Tanzania, where I was lucky to walk with giraffes and bathe in turquoise waters: that definitely made me forget the Sun for a few days! Fortunately, as a scientist, I get to travel a lot for conferences and collaborations, so I get the best of both worlds. I love doing sport (from snowboarding to a more quiet yoga sessions), music (we have a secret band with some other astrophysicists friends, but I can’t tell you about it as it is secret!) and especially dancing.


Solar Storm logo (Credit: Miho Janvier)

Can you please explain the SolarStormVR project in more detail?

SolarStorm VR is a project I started when as I was living in Scotland. It started with me meeting a talented moviemaker and talking about doing a project together. I was interested in bringing storytelling as a way to communicate about the science we do, and we thought of using Virtual Reality to excite the young audience. We obtained some funding and spent countless nights working on the project. I keep a lot of good memories from it although it was quite strenuous! As I moved to Paris for my current position, I had to juggle my new science career with touring in science festivals to present our project, which meant a lot of sleepless nights. But the smiles on our visitors’ faces were totally worth it. The project is still alive throughout the website ( where anyone can either download the video or watch it on YouTube 360.


How important is science outreach to your career?

For me, it is very important for several reasons. First of all, I have a passion for what I do and I feel lucky to have a job that is more a passion than a work. In that respect, I want to share this passion because I find space awesome!  Many times however I hear that “science is too complicated” or “I was bad in physics/maths”: for some, science seems like an obscure, incomprehensible field that is secretly kept away from the public in an ivory tower. I want to change that. Giving the chance to anyone to understand how science is being done, to make them participate, is allowing anyone to have critical thinking, which is even more important nowadays with unlimited access to real or fake facts on the Internet. And finally, in astrophysics, the majority our funding is public money. It is our duty as researchers to give back to the society that allows us to do the job we do.

Do you have any words of advice for students that would like to follow the scientist’s path

For young students: science literacy you already have, it is a skill you build. It requires hard work but I believe anyone can become a scientist. Don’t give up if it is your dream.For older students starting a scientific career (PhD students), same advice as my younger self: build a support network; don’t hesitate to ask people to mentor you if you feel you need it. You are in for the long run, so better work with people you trust, who can help you through tough times, and who you will be sharing a drink (or many) at conferences! Some of my best friends are in the field, and they make the job even better!


Welcome to the ST division blog!

The Solar-Terrestrial (ST) Division of European Geosciences Union (EGU) is starting its own blog! The blog is an initiative by a group of enthusiasts who met during the EGU’s General Assembly in April 2017. We are thrilled to set up this blog that will keep our readers informed about a range of topics relevant to the science of the division.

A CME from the Sun heading towards the Earth. Thanks to the magnetic field enveloping the Earth, we stay protected from the wrath of the Sun.
Credit: Adapted from NASA/Steele Hill

The influence of the Sun on the Earth and our planetary system have shaped a dynamic, constantly evolving scientific area. The Earth’s atmosphere, ionosphere and magnetosphere are strongly moulded by the Sun, solar wind and galactic cosmic rays. We have an armada of spacecrafts and detectors on the ground to record solar eruptive events and their in-situ manifestations. This helps us study the ST sciences.

The Sun fosters life on Earth and acts as the vitalizer of our very existence. However, it spews large amounts of plasma and energy towards the Earth that can hinder day-to-day life in modern society.

Space weather and terrestrial weather are continually influenced by small changes in solar output, which not only varies from day to day but also through longer timescales throughout its lifetime. Studying the Sun and its effects on the near-Earth environment can facilitate more accurate predictions of space and terrestrial weather. Such forecasting can in turn help keep life on this planet safe by having early warning systems.

Research in the ST sciences is very stimulating for us and we wish to share our enthusiasm with our readers. Bringing science to the public is the intent of this blog. Students as well as early career scientists (ECS) will greatly benefit from the broad nature of topics that will be discussed here. Getting everyone excited about science in general and ST studies in particular is our aim. We will discuss papers in the “spotlight” to look at the recent breakthroughs in this field. There will be articles and interviews of featured scientists to discuss post-doc life, career path or alternative careers.

As well as  exciting scientific topics we will also provide informative general highlights and timely deadlines for conferences. From time-to-time our own EGU-ST ECS representative (Jone Reistad) will discuss ECS related opportunities and problems. All in all, this will be a voice for scientists to reach out to the community.

We have planned an extensive series of blogs from our team of experts and other scientists (especially ECSs and students). We encourage guest bloggers to contact the editor. Come back every month for a new and informative blog post.


This text was prepared by Kamalam Vanninathan and Athanasios Papaioannou