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Solar-Terrestrial Sciences

Sun

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 !

The 2017 solar eclipse and scientific discoveries

The 2017 solar eclipse and scientific discoveries

The next solar eclipse is upon us. On August 21 the moon will pass between the Sun and an observer’s point of view in America and block out daylight, creating an eerie gloom in the sky. The transit of the moon between the Earth and Sun occurs about every 18 months, but for your particular city it can take several hundreds of years before a new eclipse occurs. The figure below shows the paths of all solar eclipses that occurred or will occur during the 2001 to 2020 period. Few eclipses happen around the North or South pole due to the orbital geometry of the heavenly bodies, so proportionally the odds are higher to experience midday darkness if you live at low or mid latitudes. However, since about 71% of the Earth’s surface is covered with water, most of these eclipses occur at places where no one lives and go by unnoticed. Unless you travel to them!

People have long been fascinated by solar eclipses and records in history have been found as early as 2000 B.C. Throughout history researchers and science enthousiasts have travelled the world to watch eclipses, endeavours which were much more difficult in the early days than with nowadays commercial flights. Maybe you are travelling as well to watch this eclipse.

Paths of total and annular solar eclipses during the 2001-2020 period. Credit: Fred Espenak, NASA/GSFC Emeritus

By studying the sun and the eclipses, scientists can look at features of the solar atmosphere that are otherwise hard to observe from the ground due to the intense brightness of the Sun. Discoveries made during eclipses include observations of the outer parts of the solar atmosphere (solar corona), flames of fire from the sun (prominences, jets), radiation other than visible light (infrared, UV) and otherwise invisible comets travelling around the Sun. During the 1868 eclipse a yellow spectral line was discovered by J. Lockyer in the solar chromosphere from a yet unknown chemical element that turned out to be one of the most abundant chemical species in our universe. He named it after the Greek word for the sun (helios) and it took until 1895 before helium was discovered on Earth.

Even today, scientific knowledge is being advanced by studying the solar eclipse and the effects on our nearby space environment and Earth’s atmosphere. When the moon eclipses the Sun, the illumination over a localised region will change rapidly and Earth’s atmosphere will react to this decrease in solar energy. One such reaction that occurs is in the ionosphere, the higher most reaches of the atmosphere. Solar ultraviolet radiation creates a dynamic layer of charged particles that reflect telecommunication transmissions at very low frequencies around the world. Understanding how this layer reacts to changes in solar radiation can enhance our understanding of the ionosphere and hopefully improve the region’s dynamics in model simulations. The direct blocking of radiation will also have a profound effect on the total amount of radiation that is received by the surface as well on the amount that is reflected back to space by the oceans, clouds and atmosphere. Changes in this radiation budget can in a unique way be investigated during the solar eclipse. Studying these variations, in for example temperature or radiation, during an eclipse are useful to test our current understanding of the Sun’s effect on the atmosphere.

Not only academics, but also citizens can contribute to advances in solar-terrestrial science. The Megamovie project aims to create an open-source archive of nearly 1.5 hours continuous solar eclipse. With this dataset new features in the solar corona on long and short time scales will hopefully be discovered.

So, what will you do on 21 August 2017? Watching the eclipse from your hometown, travelling to the path of totality from across the world or take part in any scientific contribution as citizen or researcher? Hopefully you will enjoy the magical moment and experience something new!

For more information: 

http://www.mreclipse.com/Totality2/TotalityApH.html

https://eclipse2017.nasa.gov/science-ground

https://eclipse.gsfc.nasa.gov/solar.html

Capturing a Whole Total Eclipse of the Sun: Megamovie

Capturing a Whole Total Eclipse of the Sun: Megamovie

by Hugh S Hudson (U. of Glasgow and UC Berkeley)

Normally solar eclipses give an observer only a fleeting moment (minutes at most) to enjoy the solar corona. We aim to amplify that considerably in the August 21 eclipse across North America. The plan is simple: Megamovie will capture everybody’s images, especially those from a group of 1,000 photographc volunteers, and compile them into an open-source archive that (weather permitting) will span an hour and a half of the corona’s life. One can find this program at the URL “eclipsemega.movie“, and in the  smartphone app “Eclipse Megamovie Mobile“.

The path of totality crosses the entire continent of North America, well-populated with eager observers equipped with the latest things in consumer electronics – marvelous cameras plus GPS and the Internet. The previous occurrence, in 1918, had none of that.  The program is thus a citizen-science project, embracing all levels of experience and capability among the observers, and at the same time it will produce a systematic record that we believe will be the first of its kind, and certainly can be the largest. We intend to follow up with citizen-science analysis projects, along the lines of SETI@Home and Zooniverse, to make sense of the very complicated records.

Megamovie does new and original things that will create real science. For the corona, the existence of the archive itself is unique.  Here we will have vast oversampling in the time domain, with access to disturbance modes on short time scales seldom observed with such resolution. Here we expect to see waves and flows in the low corona, by following the intensity variations of discrete features. Of course the Megamovie archive can extend to time scales of tens of minutes, where we know that large-scale structures will show perceptible and dynamically interesting motions. How much does a streamer wobble, and in what mode?

A CME and other structures captured in eclipse observations by Hanaoka et al. (2013); the left panel is an edge-enhanced view of one stacked image at 12-Nov-2012 20:39 UT. The right panel is a difference against observations from a different site at 21:14 (this is a cropped version of Figure 1 of the manuscript used by permission from Dr Y. Hanaoka)

The uniqueness of the August 21 eclipse continues with the coincidental presence of the bright star Regulus. This reference point will show up in all of the deep coronal images. In addition we have recently achieved precise astrometric information about the Moon, derived from the Kaguya and Lunar Reconaissance Orbiter missions; this eclipse will be the first major opportunity to apply this new information to eclipse data and the Sun.

The star field at the time of the August 21, 2017 eclipse,showing the position of the Sun as it moves during totality, and also the nearby bright star Regulus. (Figure provided by H. Hudson)

These advantages should make it possible to analyze and correct many images at a precision  rivaling that of the famous Eddington observations in 1919. We note that this historically important confirmation of general relativity has been repeated with modern detectors such as those found in everyday consumer electronics now. The Megamovie Mobile app (free) provides many resources for smartphone users; the mere timing of Baily’s Beads will make a systematic recording of the shadow path and thereby the local instantaneous radius of the Sun. The app does this automatically, and even without a cheap telephoto attachment, a smartphone camera can get wonderful timing information with precise GPS metadata.