Generation of magnetic-field aligned currents, parallel electric fields, and inverted-V structures by plasma pressure inhomogeneities in the magnetosphere

Abstract

Magnetic-field aligned currents driven by plasma pressure inhomogeneities (plasma clouds) in the distant magnetosphere are analyzed quantitatively. A parallel potential drop is found to be established in the upward current region whenever a spatial scale D 0 for the pressure gradient in the equatorial magnetosphere is smaller than ≈ 3g 0 B i B 0 , where g 0 is a hot electron gyroradius in the equatorial magnetic field B 0 ( B i denotes the magnetic induction in the ionosphere). A theoretical derivation is given for the experimentally observed linear relation T = AE p + T 0 between the characteristic energy T of precipitating magnetospheric electrons and the peak energy E p in inverted-V electron spectra. Three-dimensional potential structures accelerating electrons earthward are shown to be established beneath some model clouds which could correspond to a large scale inverted-V structure and to a thin (~ 1 km) auroral arc.