From Elizabeth Howell, offering 25 facts about our solar system that elude ready explanation: at Space.com:
Earth’s Van Allen belts are more bizarre than expected
Earth has bands of radiation belts surrounding our planet, known as the Van Allen belts (named after the discoverer of this phenomenon.) While we’ve known about the belts since the dawn of the space age, the Van Allen Probes (launched in 2012) have provided our best-ever view of them. They’ve uncovered quite a few surprises along the way.
We now know that the belts expand and contract according to solar activity. Sometimes the belts are very distinct, and sometimes they swell into one massive belt. An extra radiation belt (beyond the known two) was spotted in 2013. Understanding these belts helps scientists make better predictions about space weather, or solar storms. More.
Elewhere, Van Allen belts “stop high-energy particles in their tracks, a new study reveals.”
The new information gathered by the Van Allen Probes reveals that the inner edge of the outer belt is very sharply defined. Under normal circumstances, the fastest, highest-energy electrons cannot cross over the boundary, researchers said.
“When you look at really energetic electrons, they can only come to within a certain distance from Earth,” said study co-author and Van Allen Probes mission deputy scientist Shri Kanekal, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “This is completely new. We certainly didn’t expect that.” More. (Space.com)
You didn’t expect that?
The Van Allen belts, buried in the 25 Weird Facts at p. 19 of 27, are by far the most significant of the “weird” facts of our solar system if they help shield life—especially if they do so in an apparently complex way. As noted, at p. 7, there is water ice all over the solar system, as well as organic molecules (p. 23), but no sign of life anywhere else so far (p. 9).
Astronomers believe, we are informed at p. 9, that there could be life out there despite the fact that “So far, scientists have found no evidence that life exists elsewhere in the solar system.”(p. 9).
The implications of this problem are often missed: It seems that no evidence that Earth is an unusual planet can be taken seriously in principle. Not compared with the discovery, for example, that “Uranus has a very battered moon” (p. 20) and “Saturn has a two-tone moon” (p. 21). Why does this sound so much like copy for hair salon mags? Call it trivia creep, if you will.
See also: Ethan Siegel tackles fine-tuning at Forbes
Copernicus, you are not going to believe who is using your name. Or how.
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3 Replies to “Fine tuning: Van Allen belts more “bizarre” than expected”
of related note:
Clearly a multi-layer magnetic shield equivalent to the van Allen Belts is an ESSENTIAL requirement for any heavenly body that hopes to host Life.
Apparently neither Venus nor Mars EVER had quite the right massive iron core needed to generate such belts. And the gas giants are the exact OPPOSITE: in addition to the deadly electrons stream from Sol, the planets themselves generate HUGE amounts of deadly radiation, sterilizing EVERYTHING that comes near them.
So, what does this do to the estimates of the chances of habitable planets elsewhere? I think we’re close to “damn near impossible”.
Sol’s family of planets was VERY carefully crafted. And the jewel of Sol’s children is Earth, which was also VERY carefully crafted. And upon this artificially perfect world, humans were VERY carefully crafted. We can look for Earth 2 if we want, but we’ll never find it.
Having cut my teeth on radiation belt physics–NASA/AMPTE (launched in 1984) was the topic of my PhD–and also having known Shri since he was a graduate student, I can honestly say we’ve known these things about the radiation belts since at least 1932 when Carl Stoermer calculated charged particle orbits by hand, without the benefit of a computer. It took him 20 years.
We rediscovered Stoermer in 1955 (before Sputnik) when electron whistlers were explained as plasma ducts.
We rediscovered Stoermer yet again in 1958 when Explorer 1 returned saturated Geiger tube measurements and James Van Allen had the genius to hire Carl McIlwain as a grad student who explained it.
We rediscovered Stoermer yet again in 1966 when McIlwain invented the L-shell to explain the 3rd adiabatic invariant and its variation with solar activity. That was the famous paper where he explains all this and then withdrew it from publication when some referee wanted to be referenced as having discovered it first.
We rediscovered Stoermer yet again in 1992 when NASA launched a SAMPEX “small” satellite to probe the radiation belts and they found two of them. That was Shri’s satellite, and marks perhaps the fourth rediscovery of Stoermer.
So no, there is nothing bizarre about the radiation belts that we haven’t known for some 80 years.
Now where the particles in the radiation belts come from, is an open mystery that hasn’t been solved since 1932 when Stoermer declared them “forbidden orbits” with no access to solar wind. It was, on paper at least, the justification for the 2012 radiation belt probe mission, though to my knowledge, they still haven’t found the origin of the outer radiation belts.
If you’re dying of curiosity, I can direct you to a few papers I’ve written.