Friction Layer in Comet Halley's Ionosheath
- Alan Johnstone
Published Online: 26 MAR 2013
Copyright 1991 by the American Geophysical Union.
Cometary Plasma Processes
How to Cite
Pérez-de-Tejada, H. (1991) Friction Layer in Comet Halley's Ionosheath, in Cometary Plasma Processes (ed A. Johnstone), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM061p0117
- Published Online: 26 MAR 2013
- Published Print: 1 JAN 1991
Print ISBN: 9780875900278
Online ISBN: 9781118663660
- Space plasmas;
The properties of the mass-loaded shocked solar wind in the region between the intermediate transition and the cometopause in comet Halley's outer plasma environment are examined. It is argued that the flow behavior within that region is consistent with the effects of friction phenomena between the external plasma flow and the bulk of cometary material at the cometopause. In particular, the low-energy branch of cometary ions detected at, and downstream from, the intermediate transition represents a population of particles initially dragged-off from the cometopause and gradually accelerated viscously into the streaming flow. It is argued that the local convective electric field of the mass-loaded shocked solar wind is not sufficient to propel that population of cometary particles, and that a non-local source of momentum is required to explain their motion. The scattering of the particles' momentum, induced by their interaction with turbulent wave fields in the presence of a velocity shear, is assumed to be the underlying process responsible for the momentum exchange among them. The overall character of the plasma between the intermediate transition and the cometopause can be described in terms of a friction layer formed along the flanks of the cometopause. It is further noted that the kinematic viscosity coefficient derived from the geometric aspect of this layer implies that the momentum exchange mean free path of the cometary ions is of the order of their gyroradius.