DIAGNOSTICS OF ELECTRICAL CURRENTS IN CORONAL MAGNETIC LOOPS

A method for estimating the electric currents in coronal magnetic loop s is proposed. The method is based on representing a current-carrying arch by an equivalent LRC circuit and analyzing high-Q modulations of the mm-wavelength emission during solar flares. The electric current i s assumed to be generated by converging streams of photospheric materi al and to flow along the coronal part of the loop from one Foot to the other, closing in the subphotospheric layers. An equation for the equ ivalent LRC circuit is obtained, in which the capacitance and resistan ce depend on the current. Analysis of the mm-wavelength data for sixte en flares recorded at the Metsahovi Radio Observatory reveals modulati on periods from 0.7-17 s, which imply current values I = 6 x 10(10)-1. 4 x 10(12) A. Comparison of the current energy stored in the circuit w ith the thermal energy for two flare events indicates that only about 5% of the energy of the electric circuit is released in the flare. Thi s suggests that the influence of the flare energy release on the coron al magnetic structure is small. The events studied showed a tendency f or the energy release to decrease when the current is increased. This can be understood in terms of the plasma parameter beta, which decreas es when the current grows, lowering the probability that the instabili ties responsible for flares will develop.