Weekly Science Update

Wednesday, July 30, 2008
The Sun's Magnetic Field
Solar flares, prominences, and so-called coronal mass ejections are three different manifestations of stored magnetic energy near the sun's surface being released in sudden eruptions. The energy for these dramatic events comes ultimately from the motions of the charged particles in the hot gas. There is considerable interest in understanding these events because of their potentially disruptive effects on earth via the solar wind.

In the traditional explanation, called the "storage model," the stressed magnetic field is suddenly realigned, something like a rubber band snapping, but remains in tact. The problem with this explanation is that it predicts that the magnetic field strength following eruptive events should (to a substantial degree) remain unchanged, while a recent series of observations implies a much more complex picture with magnetic field changes that have seriously challenged the storage model. SAO astronomer Jun Lin and his student have published a new paper showing that these objections can be resolved with a more sophisticated understanding of the processes at work in the sun. They calculate that previously uncorrected line-of-sight effects can seriously distort the observations and must be removed, and that key processes originate from a series of layers in the solar surface, not a single shell. Together, these and some other effects can successfully explain the observations in the context of the storage model. The work strengthens the case for the storage model, but the understanding of solar magnetic eruptions is still a work in progress.

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