Radiating Current Sheets in the Solar Chromosphere
Abstract
An MHD model of a hydrogen plasma with flow, an energy equation, NLTE ionization and radiative cooling, and an Ohm's law with anisotropic electrical conduction and thermoelectric effects is used to selfconsistently generate atmospheric layers over a 50 km height range. A subset of these solutions contains current sheets and has properties similar to those of the lower and middle chromosphere. The magnetic field profiles are found to be close to Harris sheet profiles, with maximum field strengths ~25150 G. The radiative flux F_{R} emitted by individual sheets is ~4.9 × 10^{5}4.5 × 10^{6} erg cm^{2} s^{1}, to be compared with the observed chromospheric emission rate of ~10^{7} erg cm^{2} s^{1}. Essentially all emission is from regions with thicknesses ~0.513 km containing the neutral sheet. About half of F_{R} comes from subregions with thicknesses 10 times smaller. A resolution <~ 5130 m is needed to resolve the properties of the sheets. The sheets have total H densities ~10^{13}10^{15} cm^{3}. The ionization fraction in the sheets is ~220 times larger, and the temperature is ~20003000 K higher than in the surrounding plasma. The Joule heating flux F_{J} exceeds F_{R} by ~4%34%, the difference being balanced in the energy equation mainly by a negative compressive heating flux. Proton Pedersen current dissipation generates ~62%77% of the positive contribution to F_{J} . The remainder of this contribution is due to electron current dissipation near the neutral sheet where the plasma is weakly magnetized.
 Publication:

The Astrophysical Journal
 Pub Date:
 May 2012
 DOI:
 10.1088/0004637X/751/1/75
 arXiv:
 arXiv:1406.1211
 Bibcode:
 2012ApJ...751...75G
 Keywords:

 magnetic fields;
 magnetic reconnection;
 magnetohydrodynamics: MHD;
 plasmas;
 stars: chromospheres;
 Sun: chromosphere;
 Astrophysics  Solar and Stellar Astrophysics;
 Physics  Plasma Physics;
 Physics  Space Physics
 EPrint:
 29 pages, 11 figures