Photospheric response to a flare

Abstract

Flares produce sudden and permanent changes in the horizontal photospheric magnetic field. In particular flares generally produce increased magnetic shear in the photospheric field along the neutral line. Recent observations show also that flares can produce sudden photospheric motion. We present a model for the observed changes as the response of the photosphere to a large-amplitude shear Alfvén wave propagating down from the corona on either side of the neutral line. The Alfvénic front is assumed to impact the photosphere close to the neutral line first, and then successively further away with time, such that the line of impact coincides with the flare ribbon. The wave introduces magnetic shear and velocity shear. The magnetic shear introduced at the photosphere has the same sign on either side of the neutral line, while the velocity shear has the opposite sign. We discuss the possibility that this process is responsible for particle acceleration in flares.

10 pages, 6 figures, accepted for publication in ApJ

References in corpus (9)

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• Flare reconnection-driven magnetic field and Lorentz force variations at the Sun's surface
• Comparative study of electric currents and energetic particle fluxes in a solar flare and Earth magnetospheric substorm
• On the nature of photospheric horizontal magnetic field increase in major solar flares
• High-resolution Observations of a C9.3 White-light Flare and Its Impact on the Solar Photosphere
• Photospheric Lorentz force changes in eruptive and confined solar flares