[RightWhale]

Last night Art Bell claimed that the strong sun flare decreases the earth's magnetic field, weakens it momentarily and substantially. Is he hallucinating?

[Davea]

Here's somm good info....http://science.nasa.gov/ssl/pad/sppb/edu/magnetosphere/bullets.html

[_Jim]

the earth's magnetic field, weakens it momentarily and substantially.

No more so than forcing two bar magnetes South pole to South pole and likewise with the North; momentarily the normal fields are displaced but 'weaken' is not a term I would use ...

[Barnacle]

If Art Bell says so, it must be true. ?;^T

[Axenolith]

I don't know about the weakening part but the pressure of the solar wind does deflect the field closer to Earth and as the wind is composed of particles, and a CME is a boatload of them, it stands to reason that the deflection increases during them.