This week we have a guest post from Torger Reppen. Please enjoy.
* * *
From Space Watch:
January 19, 2012 - CHANCE OF AURORAS: NOAA forecasters estimate a 15% to 20% chance of polar geomagnetic storms during the next 24 hours in response to a possible glancing blow from a CME (coronal mass ejection.) High-latitude sky watchers should be alert for auroras. Earth's atmosphere has been puffing up in response to increasing levels of UV radiation from sunspots. This is good news for satellite operators, because a puffed up atmosphere helps clean up low-Earth orbit. Meanwhile, sunspot 1401 poses a threat for some M-class solar flares.
* * *I read the information above on January 19th. I didn't quite understand it all but I found it extremely interesting. An event as large as the one described above is not rare, occurring perhaps a few times a year.
The sun has solar storms much like the gaseous planets have regular storms, and these storms are often called sunspots. Sunspots produce incredible amounts of energy and are as bright as a welder's arc, but appear dark compared to the rest of the Sun. Sunspots sometimes cause solar flares and coronal mass ejections (CME).
Solar flares are like the Balrog's flaming whip (from Tolkien's Lord of the Rings) grounded in the internal layers of the sun, and they exert some ionic and magnetic influence on our atmosphere, whereas CMEs fling huge hunks of plasma into space. This plasma can be very large and hit several planets at the same time. Some scientists estimate the CME event on January 19th may have ripped away 2-5% of Mercury's atmosphere.
So a big piece of plasma may be hurling towards Earth while I'm watching sitcoms--completely unaware that the human race will be fried any minute. Not looking good for the last of the Miller's grizzled langurs either. Fortunately, our magnetosphere repels most of it and channels a tiny bit of it to the polar regions, causing aurora borealis.
But I was perplexed by the sentence, "This is good news for satellite operators, because a puffed up atmosphere helps clean up low-Earth orbit." So many questions in that one sentence. I thought this was bad bad bad for satellites. And it is, for a few minutes or hours.
In 2007 China used an old satellite as a missile target, and created 3,000 pieces of space junk large enough to be tracked. The satellite was orbiting more than 500 miles out, and the debris that settled into orbit went everywhere from 100 miles up to farther out. The International Space Station is around 220 miles out. This debris is really bad for every nation that has satellites. In ten seconds, China increased the amount of space junk by 15%.
So space debris is bad for satellites because it can wreck them if they collide, and the debris lasts not just for a few minutes but for years or decades or possibly forever. But when the Sun's CME plasma hits the thermosphere (which is almost pure space, but has a few molecules) it heats up. This causes expansion from its usual 50 to 300 mile range out to a 50 to 500 mile range.
The increased range of this extremely thin atmosphere is enough to slow down many pieces of debris enough that they now have a decaying orbit and spiral down into Earth. Interestingly, one article I read stated that they generally aren't going fast enough to burn up like a meteor. At any rate, the atmosphere puffs up and "grabs" some space debris, thereby cleaning an orbital area of space that is popular for satellites.
A bit more about our ever vigilant and protective Mother Earth; Earth has a magnetic field. It is quite strong and deflects nearly everything. It is likely impossible for life to thrive on Earth without it because we would be subjected to far greater radiation and our atmosphere would be ripped away from time to time due to solar CMEs.
Mercury has a weak magnetic field, so if a large CME hits this planet it may scour the planet's surface. Geologic evidence in Martian rocks show that Mars used to have a magnetic field. No one knows why the magnetic field on Mars went away. Also, more and more evidence points to the position that Mars actually had a much denser atmosphere a billion years ago, complete with huge oceans. Without a magnetosphere the atmosphere would be eventually be stripped away due to solar activity. Mars currently has an atmosphere about 1/200th the density of ours. Earth is a special place.
(The picture is from: NASA SolarDynamics Observatory)