Circulating currents in magnetic flux tubes

Abstract

There are several phenomena which require the application of a force in the axial direction of a magnetic flux tube, for example: solar plasma loops, where support of the plasma mass against gravity is required within those sections of the flux tube that have vertical components, the observed upward acceleration of the plasma in flux tubes forming the legs of quiescent prominences, and the acceleration of the fast solar wind. In this paper, we show that the origin of such axial forces is the magnetic pressure of an azimuthal magnetic field Bθ generated by currents flowing in circuits passing inside and outside the flux tube, and that the source of the EMF driving this circulating current is the difference between the temperature gradients inside and outside the flux tube, which generates a thermoelectric potential.