There has been a lot of buzz about the large solar flare that was observed on March 7th (this is one of the strongest flares observed - read about this specific flare here). Most of the interest in this, other than it is an awesome thing to see, is that the material that was ejected from the Sun can interfere with satellites (like the GPS satellites you need to find your way around unfamiliar locales), power grids, and electromagnetic communications (like radio). Before I get started, below is a great video of the solar flare using different kinds of light (the Å symbol, called an angstrom, on the left side of some segments of this video is a unit of wavelength equal to 10-10 meters):
While this is truly an event to behold, there is more to it than just its beauty. Below is a short video on what you are seeing in this video and how the flare may affect us here on Earth:
The effects of astronomical events interacting with the Earth is called space weather. (NOAA even studies space weather and you can check the current space weather conditions anytime at NOAA Space Weather Prediction Center.) If you live north (or south) enough above the Equator (about 70o or so in latitude) , you may have seen the aurora (known as the aurora borealis [northern lights] if you are north of the Equator or the aurora australis [southern lights] if you are south). This light display is caused by charged particles from space interacting with the Earth's magnetic field (called the magnetosphere). This interaction directs the charged particles towards the north and south poles of the Earth. When the particles strike atoms of our atmosphere, they excite electrons in atoms that make up our air; light is produced when these excited electrons release this excess energy. Since our atmosphere is made up primarily of nitrogen and oxygen, the colors of this light are usually red (from nitrogen) or green (from oxygen). This recent solar flare is starting to interact with the Earth now and brilliant aurorae are expected. Since I am posting videos today, below is a spectacular time lapse video of the aurora borealis by National Geographic (there may be a short advertisement before it starts - sorry!):
I bring all of this up, not only because it is timely and interesting, but also because space weather affects LIGO. Space weather often produces particles that shower down on the Earth's surface called cosmic rays (even though most of the particles are not from space but are produced when very high energy particles from space smash into the atmosphere and produce showers of new particles from this interaction). Of particular concern to us is what would happen if a shower of particles are produced near or within one of our mirrors. Could this cause a vibration big enough for the detector to be sensitive to? If so, could the motion look like a gravitational wave signal? A paper published in 2008 investigated this (which you can read here if you are REALLY interested). It was determined that a strong shower could indeed move our mirrors enough for us to notice, but a strong shower like this is rare.
Even though the effect is rare, so is detecting a gravitational wave (at least until Advanced LIGO is completed). For the "Big Dog" event - when we last thought that we may have really detected a gravitational wave but it was later shown to be a blind test of our detection methods - the possibility that space weather could have affected our results was thoroughly investigated (along with many other things like one of us turning to the dark side and fraudulently adding this signal to the detector). As it turned out, it was a "clear" space weather day for that event.
Remember to check the NOAA Space Weather Prediction Center for updates on the effects of this recent solar flare here on Earth!