On the Origin of Persistent Radio and X-ray Emission from Brown Dwarf TVLM 513-46546

Abstract

We study the origin of unusually persistent microwave and X-ray radiation from the ultracool dwarf TVLM 513-46546. It is shown that the source of ≈1 keV X-ray emission is not the entire corona of the brown dwarf, but a population of several hundreds of coronal magnetic loops, with 10 MK plasma heated upon dissipation of the electric current generated by the photospheric convection. Unlike models, which assume a large-scale magnetic structure of the microwave source, our model suggests that the microwave radiation comes from hundreds of magnetic loops quasi-uniformly distributed over the dwarf’s surface. We propose a long-term operating mechanism of acceleration of electrons generating gyrosynchrotron radio emission caused by oscillations of electric current in the magnetic loops as an equivalent RLC circuit. The second population of magnetic loops—the sources of microwave radiation, is at the same time a source of softer (≈0.2 keV) X-ray emission.

Cowling resistivity and Joule dissipation in solar atmosphere

“…It was shown in a number of studies that the neutral component of the plasma plays an important role in the Joule dissipation both in the stellar atmospheres and in the magnetospheres and ionospheres of planets (see, e.g., [2][3][4]). A number of phenomena on the Sun and stars are associated with the dissipation of the electric currents, for example, flare precursors ( [5] and references therein), flare energy release [6][7][8], heating of magnetic loops up to 10-15 MK [9], heating of the stellar coronae [10,11]. The flare energy release in the partially ionized plasma of the solar photosphere and chromosphere has been repeatedly considered (see, e.g., [2,3,12]).…”

Editorial to the Special Issue “Advances in the Physics of Stars—In Memory of Prof. Yuri N. Gnedin”

“…Article [6] investigates unusual microwave and X-ray radiation from the ultracool dwarf TVLM 513-46546. According to the proposed model, the microwave radiation of this source comes from hundreds of magnetic loops quasi-uniformly distributed over its surface.…”