Understanding the Sun-Earth Connection

Solar activity has been in the news a lot the past few months. So, unless you’ve been hiding under a rock with a tinfoil hat wrapped around your head, you’ve probably noticed numerous stories about solar flares and coronal mass ejections (CMEs) from the Sun and how they can cause everything from northern lights to power grid failures if they happen to send blasts of energized particles directly at Earth and our magnetic field.

Well, all that’s true.  And, the chances of solar activity affecting us and our technology are pretty high when the Sun is more active, as it is right now.  To be more precise, the Sun is going through a period called solar maximum, where it is more active.  Thus, we see more flares and mass ejections than during periods when the Sun is more quiescent.

This solar activity affects something called “space weather”, which refers to conditions and processes that occur in space that have the potential to affect Earth and its atmosphere.  Solar activity such as coronal mass ejections, solar flares, and the constant action of solar wind bring energy and particles from the Sun across space to Earth. Once they get here, they can disrupt Earth’s magnetic field, and they can cause radiation damage to spacecraft, and interrupt telecommunications, and affect global positioning satellite systems.  On the ground, disruptions to our magnetic field can interrupt power grids.

So, it makes sense that NASA and other space agencies are interested in studying the Sun’s influence on Earth’s radiation belts.  They’d like to be able to predict and understand solar outbursts, with an eye toward protecting us and our technology. And so, they are focusing some special attention on the near-Earth radiation environment.

You may have heard of the Van Allen belts. They were discovered and characterized in 1958 by James Van Allen, and surround our planet in a set of two torus-shaped nested belts that ranges from a thousand to 60,000 kilometers above Earth’s surface. Most of the particles that zip around in the Van Allen Belts come from the Sun, carried there by the solar wind.

Now, the interesting thing about the Van Allen Belts is that it is pretty dangerous to fly spacecraft through this region because of the intense radiation environment they contain. Anything that we want to send up to space either has to cross the belt quickly or stays pretty well away from it.  So, there haven’t been many spacecraft sent specifically to hang around IN the belt and study it for any length of time. One of the reasons is that a probe designed to spend time in the belt would need to have much of its electronics package shielded from the heavy radiation in the belt.

All that’s changing with the launch last week of the NASA Radiation Belt Storm Probes (RBSP).  These two heavily-shielded spacecraft will study the Van Allen Belts to figure out how particles get INTO the belts, what happens to them when they’re there, and where they go when they leave the belts.  The probes will also give solar physicists some insight into how such events as coronal mass ejections and solar flares affect the Van Allen Belts.

I think it’s pretty cool that we have a pair of spacecraft that are deliberately and carefully designed to survive in the Van Allen Radiation Belts for at least two years and possibly four years (when the mission is extended) in constant contact with high-energy particles.  They’lll give scientists the most in-depth look at just what’s happening in these dangerous radiation environments.

What I also find interesting about this mission is that the  probes aren’t acting alone.  There is a very important ground-based portion of the RBSP mission that involves my friends over at MIT’s Haystack Observatory.

In about 60 days, when the spacecraft have gone through their commissioning period (that is, when they are tested and calibrated), then the prime science mission begins. At that time, the Millstone Hill installation at Haystack will make collaborative electric field measurements on the same magnetic field line that the RBSP is experiencing during its orbit through the inner and outer belts.  This will give scientists more than one point of view on activity in the radiation belts and help them understand the activities occurring in the belts in response to activity on the Sun.

The current solar maximum is, I think, one of THE most studied maximums in recent history.  Not only do we have spacecraft such as the RBSP probes, the Solar Dynamics Observatory, the Solar Heliospheric Observatory, STEREO and many other missions focused on the Sun and its activity, but places like Haystack Observatory are uniquely positioned to give the ground-based, almost “3-dimensional” view of what’s happening as the Sun sends its fury our way.

If you want to learn more about space weather, the RBSP mission, and others, here are a few links to help you out.  And, by all means, check it all out.  Living with a star like the Sun gives us a great chance to understand other stars and their environments, too.

Space Weather FX podcast series, MIT Haystack Observatory/Loch Ness Productions

MIT Haystack Observatory Atmospheric Physics page

Radiation Belt Storm Probes, NASA Mission to study solar effects on Earth’s radiation belts

Solar Dynamics Observatory, a NASA/JHU mission to study the Sun

STEREO, a twin-probe NASA mission to study the Sun in stereo

SOHO (Solar Heliospheric Observatory), a NASA mission to study the Sun