Category Archives: solar physics

aurora borealis, solar flares, solar physics, space weather, space weather FX

Surviving the Radiation Belts

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Understanding the Sun-Earth Connection

A Solar Dynamics Observatory (SDO) view of a dark prominence crossing beneath a coronal loop on the active surface of the Sun. This is part of a sequence of events that took place August 26-28th. Prominences are long strands of cooler gases that float above the solar surface. The loops are seen in extreme ultraviolet light by SDO. These are magnetic field lines being traced by spiraling particles above active regions of the Sun. Courtesy SDO.

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.

Two identical Radiation Storm Belt Probes will pass through the inner and outer radiation belts that surround our planet. Courtesy JHU/APL/NASA.

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.

The Millstone Hill Radar installation at MIT's Haystack Observatory is part of the ground-based component of the RBSP mission. Courtesy MIT/Haystack Observatory.

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

 

 

comet elenin, solar flares, solar physics

Killer Solar Flares and Rogue Comets, Oh My

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They Aren’t Going to Be Harming Us

Earth is NOT doomed. Yeah, I know this is going to come as a complete disappointment to the folks who insist the universe is out to get us via the auspices of giant killer solar flares and rogue comets. It ain’t gonna happen. Lucky for all of us, the universe is sticking to the laws of physics.

The Valentine's Day 2011 solar flare. Courtesy NASA/SDO/SOHO

Let’s start with the so-called giant killer solar flares. Yes, increased solar activity, including flares and coronal mass ejections (outbursts from the Sun), is a concern. This is because we’re heading into a period of maximum solar activity (something the Sun goes through periodically), and we are expecting more solar flares and coronal mass ejections.

This is pretty much normal for the Sun, despite some of the screaming headlines on conspiracy theory Web sites about “mysterious” solar flares and what they supposedly mean for mankind.

In reality, solar activity is not mysterious. It’s not confusing scientists, nor is it being directed by aliens (yes, I saw that on a Web site). Solar activity is part of what our star does.  Solar physicists (the experts on solar activity) are really starting to understand some of the mechanisms of solar flares, for example, thanks to solar-observing satellites such as SDO, STEREO, and SOHO.  But, giant killer solar flares? Those are a product of overworked imaginations of people who don’t understand the basic principles of physics and the Sun.  For one thing, there isn’t enough energy in the Sun to power a monster fireball that could hang together long enough to travel 150 million kilometers between the Sun and Earth.

Sure, solar flares can be strong enough to create space weather disturbances that can stimulate auroral displays above our poles. All that means is that the energy transfer from Sun to Earth is strong enough to excite gases in our upper atmosphere, which causes them to glow. This happens a lot, and not just on Earth. Aurorae have been seen on such planets as Jupiter and Saturn, for example. Same principle at work there, too.

In some cases, the space weather can mess a bit more with our upper atmosphere, which affects some of our technology—such as telecommunications and GPS signals. (For more information about space weather, visit the Space Weather FX Web site at MIT. It contains a series of very nicely produced videos (if I do say so myself) about the effects of space weather. Very timely and very educational.) Studying solar flares is an important step in understanding the whole Sun and the cycles it goes through, and I, for one, look forward to seeing what astronomers learn about our star during this next solar cycle.

The other great story that’s been making the rounds among the “we’re gonna die” crowd is about Comet Elenin. It is (or was, actually) a perfectly harmless comet making a swing past the Sun (as many comets do). A few folks got all hot and bothered by their own misconceptions about the comet’s orbit and they worried that all kinds of disasters would occur on or to Earth, all caused by the comet. I read some of these…ummm… pseudo-scientific rants. To be honest, I never could figure out what the fuss was about. And some of the uneducated hyperbole was… laughable.

Comet Elenin as seen by HI1-B on Aug. 6, 2011. As Comet Elenin passed to within just 7 million kilometers of the STEREO (Behind) spacecraft, NASA rolled the spacecraft to take a look at it (Aug. 1, 2011) with its wide angle HI-2 instrument. Though the observation lasted only a little over an hour, the fuzzy looking comet can be seen moving across a small portion of the sky. STEREO will be taking these one-hour observations every day through August 12. The comet is seen by the HI-2 telescope between August 1-5, and by the higher resolution HI-1 telescope between August 6-12. From August 15 onward, the comet enters the HI-1 telescope's nominal field of view, at which time we should enjoy continuous viewing of the comet. Over time, we expect the comet to be visible in the SOHO C3 coronagraph on September 23 for six days and possibly STEREO's COR2 coronagraph as well between August 20 and September 1. Courtesy NASA/STEREO mission.

As it turns out, there never was anything to be worried about. Comet Elenin came as close as 72 million kilometers to the Sun and never got closer than about 34 million kilometers to Earth. For reference, the Sun and Earth are 150 million kilometers apart; Venus and Earth are close as about 38 million kilometers apart when they are closest to each other in their orbits. So, Elenin was never in any danger of smacking into us.  It faced far more danger from its close approach to the Sun.

As it passed near the Sun, Elenin broke up into a traveling collection of ice chunks and bits of dust. It’s now scattered along its former orbit.  According to Don Yeomans, the comet expert at the Near-Earth Objects Program Office at Jet Propulsion Lab in California, about two percent of new comets passing by the Sun break up like this. This is because most comets are made up of ice, rock, dust and other stuff that are all held together in a loosely bound conglomeration that can be easily disturbed by the pull of gravity from a nearby planet or the Sun. This is all perfectly natural and nothing to be worried about.And, trust me, comets can’t screw with Earth’s axis or change our magnetic fields or do any of the stuff that they’ve been accused of by some of these pseudo-scientists.

Look, the solar system is an interesting place scientifically. We continue to explore it and learn more about it. Everything we learn is from observations and the applications of basic scientific laws. The more we look, the more we discover, quite simply because we keep creating better and better tools with which to study the cosmos. This is great, and it’s what science is all about: figuring stuff out from the evidence in front of us, using scientific principles to do so.

Science doesn’t make the solar system weird or mysterious or frightening or alien. People with a vested interest in having you believe (and the operative word here is “believe”) their untested, unscientific assumptions about things they don’t quite seem to understand may drive a few folks to read ranting Web sites. I’m sure it feeds the egos of those people who have books to sell or tales to tell. But, it’s really not the way that sane, rational people view the cosmos. And, it’s certainly not the way science works.  The universe is grand and wonderful enough without making up inane stuff about it.