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Session 36 - Solar Activity.
Display session, Tuesday, June 11
Tripp Commons,
A two dimensional, steady state, resistive MHD model with flow is used to support the proposition that a major source of heating for the solar middle chromosphere is the resistive dissipation of large scale electric currents driven by a convection electric field. The currents are large scale in the sense that their scale heights range from hundreds of kilometers in the network to thousands of kilometers in the internetwork. The current is carried by protons, and flows orthogonal to the magnetic field which is embedded in a weakly ionized, strongly magnetized hydrogen plasma. The resistive dissipation is determined by the Pedersen resistivity. The flow velocity is mainly parallel to the magnetic field, but the relatively small component of flow velocity orthogonal to the magnetic field generates a convection electric field which drives the current. The magnetic field is the sum of a loop shaped field, and a much stronger, larger scale potential field. The heating takes place in the region occupied by the loop field which is only a few gauss while the potential field is close to 200 G. Hence magnetometer observations may suggest that the total field is potential while radiation intensity observations indicate the presence of mechanical heating. Solutions to the model indicate that magnetic elements with horizontal spatial extents of \sim 1 - 5 thousand kilometers may be confined to, and heat, the middle chromospheric network. Solutions to the model also indicate that magnetic elements with horizontal spatial extents of \sim 10 - 30 thousand kilometers may span and heat the middle chromospheric internetwork region over the interior of supergranules, and may be the building blocks of the chromospheric magnetic canopy.
