George H. Fisher, David J. Bercik, Brian T. Welsch, Hugh S. Hudson
We compute the change in the Lorentz force integrated over the outer solar
atmosphere implied by observed changes in vector magnetograms that occur during
large, eruptive solar flares. This force perturbation should be balanced by an
equal and opposite force perturbation acting on the solar photosphere and solar
interior. The resulting expression for the estimated force change in the solar
interior generalizes the earlier expression presented by Hudson, Fisher and
Welsch (CS-383, ASP, 221, 2008), providing horizontal as well as vertical force
components, and provides a more accurate result for the vertical component of
the perturbed force. We show that magnetic eruptions should result in the
magnetic field at the photosphere becoming more horizontal, and hence should
result in a downward (towards the solar interior) force change acting on the
photosphere and solar interior, as recently argued from an analysis of
magnetogram data by Wang and Liu (Astrophys. J. Lett. 716, L195, 2010). We
suggest the existence of an observational relationship between the force change
computed from changes in the vector magnetograms, the outward momentum carried
by the ejecta from the flare, and the properties of the helioseismic
disturbance driven by the downward force change. We use the impulse driven by
the Lorentz-force change in the outer solar atmosphere to derive an upper limit
to the mass of erupting plasma that can escape from the Sun. Finally, we
compare the expected Lorentz-force change at the photosphere with simple
estimates from flare-driven gasdynamic disturbances and from an estimate of the
perturbed pressure from radiative backwarming of the photosphere in flaring
conditions.
View original:
http://arxiv.org/abs/1006.5247
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