Physics
Scientific paper
May 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011spd....42.1704g&link_type=abstract
American Astronomical Society, SPD meeting #42, #17.04; Bulletin of the American Astronomical Society, Vol. 43, 2011
Physics
Scientific paper
An MHD model that includes a complete electrical conductivity tensor is used to estimate conditions for photospherically driven, linear, non-plane Alfvenic oscillations extending from the photosphere to the lower corona to drive a chromospheric heating rate due to Pedersen current dissipation that is comparable to the observed net chromospheric radiative loss of 107 ergs-cm-2-sec-1. The heating rates due to electron current dissipation in the photosphere and corona are also computed. The wave amplitudes are computed self-consistently as functions of an inhomogeneous background atmosphere. The effects of the conductivity tensor are resolved numerically using a resolution of 3.33 m. The oscillations drive a chromospheric heating flux FCh 107-108 ergs-cm-2-sec-1 at frequencies nu 102 - 103 mHz for background magnetic field strengths B > 700 G, and magnetic field perturbation amplitudes 0.01-0.1 B. The total resistive heating flux increases with nu. Most heating occurs in the photosphere. Thermalization of Poynting flux in the photosphere due to electron current dissipation regulates the Poynting flux into the chromosphere, limiting FCh. FCh initially increases with nu, reaches a maximum, and then decreases with increasing nu due to increasing electron current dissipation in the photosphere. The resolution needed to resolve the oscillations increases from 10 m in the photosphere to 10 km in the upper chromosphere, and is proportional to nu-1/2. Estimates suggest these oscillations are normal modes of photospheric flux tubes with diameters 10-20 km, excited by magnetic reconnection in current sheets with thicknesses 0.1 km.
This work was supported by the NSF Solar Terrestrial Physics Program. It is described in detail in a paper in submission to ApJ.
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