Plasma Conductivity in a Cometary Ionosphere

Abstract

view Abstract Citations (3) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Plasma Conductivity in a Cometary Ionosphere Ershkovich, A. I. ; Israelevich, P. L. Abstract The one-dimensional spherically symmetric model of Buti & Eviatar results in very low plasma conductivity value in the inner coma of comet Halley. Anomalous resistivity cannot account for this result, as the electric current in the comet Halley ionosphere is shown to be too small. On the other hand, replacement of the one-dimensional model by the axisymmetric model using the same (Giotto) data does not result in contradiction with the frozen-in magnetic field approximation. Thus, we arrive at the conclusion that three-dimensional character of the plasma flow around a comet is crucial, and the one-dimensional model of Buti & Eviatar becomes defective on approaching the diamagnetic cavity. The conductivity σ0 (which governs the magnetic field diffusion) in the magnetic barrier of comet Halley is almost coincident with that given by the classical Spitzer-Härm formula for a binary gas: σ0 ≍ 2 x 1011 esu. With this value, the magnetic Reynolds number Rem ≫ 1, which means that the frozen-in magnetic field approximation is justified almost throughout the cometary ionosphere (cf. the results of Cravens). Publication: The Astrophysical Journal Pub Date: June 1996 DOI: 10.1086/177383 Bibcode: 1996ApJ...464..959E Keywords: COMETS: GENERAL; COMETS: INDIVIDUAL NAME: HALLEY; PLASMAS full text sources ADS |