KINETIC ALFVÉN WAVE INSTABILITY DRIVEN BY FIELD-ALIGNED CURRENTS IN SOLAR CORONAL LOOPS

Magneto-plasma loops, which trace closed solar magnetic field lines, are the primary structural elements of the solar corona. Kinetic Alfvén wave (KAW) can play an important role in inhomogeneous heating of these magneto-plasma structures in the corona. By the use of a low-frequency kinetic dispersion equation, which is presented in this paper and is valid in a finite-β plasma with Q < β < 1 plasma (where β is the kinetic to magnetic pressure ratio and Q = me /mi is the mass ratio of electrons to ions), KAW instability driven by a field-aligned current in the current-carrying loops in the solar corona is investigated. The results show that the KAW instability can occur in wave number regimes 0 < kz < kcz and 0 < k < kc , and that the critical wave numbers kcz and kc and the growth rate both considerably increase as the drift velocity VD of the current-carrying electrons increases in the loops. In particular, for typical parameters of the current-carrying loops in the solar corona this instability mechanism results in a high growth rate of KAWs, ωi ∼ 0.01-0.1ωci ∼ 103-104 s–1. The results are of importance in understanding the physics of the electric current dissipation and plasma heating of the current-carrying loops in the solar corona.