When Earth's magnetic field is null during the coming pole reversal, will solar wind blow away the ionosphere?

Question

The poles reverse (S becomes N and vice versa) every 200,000 years. The next reversal is long overdue. When it happens, there will be a brief phase of the Earth's magnetic fields being weak and, within that phase, the field will be effectively null.

The magnetic field holds the ionosphere in place. When the field diminishes, particles from the solar wind will be able to push the ions in the ionosphere away from Earth, as evidenced by how large the ion cloud is on the "nighttime" or lee side of the Earth.

The ionosphere protects the Earth from some kinds of solar radiation, so we could expect an increase when the magnetic field is at its nadir. That could have profound effects on climate, flora and fauna.

I'm wondering whether the loss of magnetic field will last long enough for the Earth to feel serious effects.

Thanks!

Answer 1

No, the magnetic field does NOT become "effectively null". It becomes mixed up, with several weak north and south magnetic poles. The overall field remains at least at 20% of today's strength, which is more than enough to hold the ionosphere shielding in place. The UV radiation at the surface will not even double. The growing area for some plants and crops might move a few 100 miles away from the equator.



The effect lasts for only a few 1000 years.

Answer 2

No one knows exactly what happens to the magnetic field during a reversal. It is unlikely however that it disappears altogether, it is believed that it reduces to approximately 10% of full value and becomes erratic and possibly quadropolar. As for the effects, yes there probably would be a drop in the protection offered by the magnetic field and the atmosphere. However the effects are likely to be limited to a more widespread view of the Northern and Southern lights and increased cancer risk. The latter of these is unfortunate but would not likely be on a significant enough scale for long enough to cause major problems. As for climate, the net radiation flux to the surface wouldn't change, at least not enough to seriously affect climate.

Answer 3

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Not exactly. This has occurred about sixty times over the past 65 million years or so. (The end of the Cretaceous is part of a zone named polarity subchron 29R, with the 'R' standing for 'reverse' meaning the opposite polarity to today. It's the 29th counting back from today.) As well as typically happening over five times slower than your figure suggests, this is also irregular.



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It isn't. As said, this is an irregular occurrance. The most recent flip took place around 780,000 years.



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It could do. I haven't been following that sort of discussion closely, so can't go into any worthwhile details.

Answer 4

Actually, Venus does have a magnetic field, though it is much weaker than the one Earth has. But it takes more than solar wind to blow away an atmosphere. A planet's gravity plays a large part in holding the atmosphere in place. Here's a quote from Wikipedia: "An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body."