Plasma conductivity in a cometary ionosphere

A. I. Ershkovich*, P. L. Israelevich

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

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-Harm formula for a binary gas: σ0 ≈ 2 × 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).

Original languageEnglish
Pages (from-to)959-964
Number of pages6
JournalAstrophysical Journal
Volume464
Issue number2 PART I
DOIs
StatePublished - 1996

Keywords

  • Comets: general
  • Comets: individual (Halley)
  • Plasmas

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