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National Solar Observatory Predicts Shape of Solar Corona For August Eclipse (phys.org)
bsharma shares a report from Phys.Org: August 21st will bring a history-making opportunity for the entire United States. On that day, every person in the country, including Hawaii and Alaska, will have an opportunity to witness at least a partial solar eclipse as the moon moves in front of the Sun. If you have the good fortune to be along the path of totality, stretching from Oregon to South Carolina, you will get to witness one of the most awe-inspiring views in nature -- the wispy wonders of the solar corona. But there is more to the corona than one might initially realize.
Dr. Gordon Petrie from the National Solar Observatory (NSO) explains: "The corona might look like it's a fuzzy halo around the Sun, but it actually has quite a lot of structure to it. The Sun has a magnetic field that, at first glance, might remind us of the middle-school experiment where you sprinkle iron filings over a bar magnet to get a butterfly shape. However, on closer inspection, it is far more complicated than that. Since we are exactly one solar rotation away from the solar eclipse, we're able to use today's observations to predict the structure of the corona on Aug. 21st," says Petrie. "The corona is not likely to change too much between now and the eclipse, unless we get lucky and a large active region appears! We expect to see faint, straight structures protruding from the north and south poles of the Sun -- these are the polar plumes. We will be able to see brighter bulbs of material closer to the equator -- these are called helmet streamers."
Dr. Gordon Petrie from the National Solar Observatory (NSO) explains: "The corona might look like it's a fuzzy halo around the Sun, but it actually has quite a lot of structure to it. The Sun has a magnetic field that, at first glance, might remind us of the middle-school experiment where you sprinkle iron filings over a bar magnet to get a butterfly shape. However, on closer inspection, it is far more complicated than that. Since we are exactly one solar rotation away from the solar eclipse, we're able to use today's observations to predict the structure of the corona on Aug. 21st," says Petrie. "The corona is not likely to change too much between now and the eclipse, unless we get lucky and a large active region appears! We expect to see faint, straight structures protruding from the north and south poles of the Sun -- these are the polar plumes. We will be able to see brighter bulbs of material closer to the equator -- these are called helmet streamers."
Not so nice for those who have to settle for annular eclipses when the moon is too far away. We need a bigger moon, time to crash some asteroids into it.
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I was going to make a joke about the moon's small size being due to evaporation caused by anthropogenic global warming; but I was worried some people here would think I was being serious.
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...for a narrow time window. The moon gets a bit more than 3 cm farther from the earth every year due to rotational energy coupling through the tides. We are in the comparatively narrow time window (geologically speaking) where the moon and the sun have roughly the same angular width as seen from the earth (depending on just where the moon is in its elliptical orbit and where the earth is in ITS elliptical orbit). Wait a million years or so and the moon will produce only annular eclipses.
It's like Polaris as the North Star. Fiction writers like to portray Jesus or Moses or Caesar looking north and waxing poetic about the Nort Star, but a couple of thousand years ago Polaris wasn't the North Star, we had no North Star. Even a few hundred years from now it is going to be making circles instead of behaving like a fixed point on time lapse photographs. Sigh.
Even when the experts all agree, they may well be mistaken. --- Bertrand Russell.