This has been an interesting week. We’ve had two solar storm predictions of note. The first was the promise of a huge, potentially devastating event slated to arrive on March 18th. The second is far less newsworthy: a high-speed stream is scheduled to drive activity at Earth between today and tomorrow. What are we left with between these two reports? A case study of both good and bad space science reporting. Let’s break these down in reverse order:
Haley’s Comet is making a return of sorts. Bits of the famous comet will be hitting Earth’s atmosphere and lighting up from Oct. 20 to Oct. 23. It should be a beautiful sight for amateur astronomers.
While this type of event isn’t frequently associated with space weather, ballistic hazards do pose a threat to spacecraft. Small objects, including meteoroids and “space junk” (bits of old spacecraft) pose a huge threat to our space-borne communications. Even grain-sized objects are moving so fast that they can pierce solar panels, insulation, and other parts. Large objects can obliterate spacecraft, creating a new wave of space junk, which can cause a cascade of destruction around the Earth. Space junk is serious business.
Here’s hoping your Halloween is extra scary.
If the skies are clear, go outside- you just might see the aurora! Over the past 24 hours, NOAA SWPC has been warning that we may see a geomagnetic storm. Because the intensities of such storms are hard to predict, and because the recent spate of storms has been so weak, I have been very skeptical that we would see a “good one”, but right now, we’re seeing all the earmarks of a “real” space weather storm- one worth paying attention to! The storm has reached “G4” on NOAA’s geomagnetic storm scale, which is the 2nd most severe category. Here’s a quick summary of the last few hours:
|KP||8||Very high activity, 9 is the highest that the Kp index can get!|
|DST||-150nT||More negative is stronger; watch to see if we hit -300nT|
|Solar Wind Speed||~700km/s||Almost twice as fast as usual.|
|Solar Magnetic Field||BZ ~= -30nT||Strength of magnetic field in solar wind, more negative means more energy delivered to the Earth & aurora.|
So far, these are the kinds of numbers you associate with strong, possibly damaging storms. It will be interesting to watch the DST number; if it drops to -300nT, we’ve hit “super storm” status.
Watch the skies this evening!
There is an excellent article at fivethirtyeight.com summarizing how the upcoming solar eclipse is huge opportunity for space weather researchers. During this time, the Moon will eclipse the Sun, and the solar corona will be observable. The corona is the Sun’s atmosphere, which extends far away from the Sun’s surface. It is where many interesting space weather phenomena originate- including the acceleration of the fast solar wind. The short eclipse period will give researches a short but critical window over which to learn more about how the corona behaves.
The corona is not easy to observe. Under normal conditions, it is completely washed out by the light of the sun- it’s like trying to see the distant light of a cell phone screen which is directly adjacent to a headlight. In research, tools known as coronagraphs are used. These are telescopes with fixed occulting disks to block out the light of the Sun, allowing us to observe the corona. An example is the LASCO coronagraph aboard the SOHO satellite. You’ll notice that the occulting disk is very large- much larger than the radius of the Sun. This is to prevent visual artifacts that would otherwise ruin the image. During the eclipse, the Moon covers up much less of the corona than an occulting disk but does not suffer from light artifacts because the moon is very distant compared to the observer. Therefore, the eclipse gives us perfect conditions to see the solar atmosphere.
While I won’t be making observations of the corona, I will be on a short trip to make sure that I don’t miss the eclipse. I’ll share pictures and video here when I return!