Global Forces in Eruptive Solar Flares: The Lorentz Force Acting on the Solar Atmosphere and the Solar Interior |
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| Authors: | G H Fisher D J Bercik B T Welsch H S Hudson |
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| Institution: | (1) Homer, IL, USA |
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| Abstract: | 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 (Astron. Soc. Pac. CS-383, 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 (toward 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. |
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