Observations of the Velocity Distribution of Pickup Ions
- Alan Johnstone
Published Online: 26 MAR 2013
Copyright 1991 by the American Geophysical Union.
Cometary Plasma Processes
How to Cite
Coates, A. J. (1991) Observations of the Velocity Distribution of Pickup Ions, in Cometary Plasma Processes (ed A. Johnstone), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM061p0301
- Published Online: 26 MAR 2013
- Published Print: 1 JAN 1991
Print ISBN: 9780875900278
Online ISBN: 9781118663660
- Space plasmas;
Ion pick-up is well-established as the process whereby comets interact with the solar wind. Although this mechanism was postulated as such over 30 years ago it was not until the 1985–6 cometary armada reached their goals that direct measurements of the process in the cometary environment could be performed. Here we review the measurements of pickup ion distributions from the various spacecraft, concentrating on the observed pitch angle and energy scattering in the turbulent solar wind upstream of comets. Comparison with simulation and with theory is attempted by way of the inferred timescales for pitch angle and energy diffusion. Measurements of the bulk velocity of the picked-up ions are compared with the guiding centre approximation far upstream of the comet and with the wave phase velocity nearer in.