Friday, November 27, 2009

"Solar Tsunamis" - Cool Name for Fast-Mode Magnetohydrodynamical Waves

"" (November 25, 2009)

"Incredibly powerful waves of plasma rippling across the surface of the sun and dubbed "solar tsunamis" were first observed years ago, but were thought to be an optical illusion. Scientists have now confirmed, though, that they are really real.

"When scientists first saw the phenomenon, it was hard to believe that a towering wave of hot plasma was actually racing along the sun's surface. One of the waves rose up higher than the diameter of Earth and rippled out from a central point in a circular pattern millions of miles wide, like a gargantuan pattern of waves created by a pebble dropped in a pond.

"Skeptical observers suggested it might be a shadow of some kind – a trick of the eye. But new observations from NASA's STEREO (Solar Terrestrial Relations Observatory) spacecraft are telling researchers that this controversial phenomenon isn't an illusion.

"This week, NASA released a remarkable video of a solar tsunami...."

The "solar tsunamis" discussed by the article aren't the sort of oversize water waves we have on Earth, of course - and they're not called "solar tsunamis" either. The waves are called "fast-mode magnetohydrodynamical waves" – or "MHD waves."

The idea that MHD waves were a sort of shadow wasn't as silly as it might seem. The waves were observed in 1997, and that one was associated with a coronal mass ejection - or "CME." Thinking that the wave was associated with - and possibly a sort of optical illusion generated by the CME - wasn't beyond imagination.

On the other hand, it looks like MHD waves now join the ranks of phenomena like ball lightning and thunderstorm sprites: that were "known" to be hallucinations suffered by credulous, unreliable people like airline pilots and soldiers; and now are the subject of learned papers.

I think video cameras helped: Even an acknowledged scientific expert might hesitate before saying that a video camera had been having a hallucination.

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