DE/EICS investigations of H/O energy ratio

The discovery and explanation of a solar cycle variation of the relative energies of escaping H+ and O+ ions.

Illustration of the solar cycle variation in the relative energies of H+ and O+ beams observed flowing up auroral magnetic field lines. Adapted from Collin et al (1987).

Upper left: Monthly average solar flux index F10.7 for the last solar cycle. The cross-hatched areas identify the three time intervals for which the energy of upflowing H+ and O+ beams have been compared.

The other three panels present the O+ vs. H+ mean energies for observed upflowing ion beams at low (right two panels) and high (left panel) levels of the F10.7 index.

The cause of the variance is now understood to arise from the sensitivity of the two stream instability to the relative concentrations of H+ and O+ ions as they flow up auroral field lines.

At low levels of solar activity the ratio of H+ to O+ in upflowing beams is large. (Yau et al.). Under these conditions the transfer of energy from H+ to O+ proceeds rapidly. Energy transfer from H+ to O+ is slower when the fluxes of the two ions are more equal near solar maximum. See the papers listed below for the theoretical and simulation results supporting this conclusion.

References, alphabetical by first author.

Bergmann, R., H+ - 0+ Two stream interaction on auroral field lines, Submitted to Physics of Space Plasmas, SPI Conference Proceedings and Reprint Series, No. 9, ed. T. Chang, G.B. Crew, and J.R. Jasperse, Scientific Publishers, Cambridge, MA, 1990, P.229
Collin, H. L., W. K. Peterson, and E. G. Shelley, Solar cycle variation of some mass dependent characteristics of upflowing beams of terrestrial ions, J. Geophys. Res., 92, 4757, 1987.
Kaufmann, R. L., and G. R. Ludlow, Interaction of H+ and O+ beams: Observations at 2 and 3 Re, Proceedings of the Chapman Conference on Ion Acceleration in the Ionosphere and Magnetosphere, Amer. Geophys. Union, Washington, D.C., Pg-92, 1986.
Peterson, W.K., Auroral Zone Ion Composition, in Modeling Magnetospheric Plasma, Geophysical Monograph 44, T.E. Moore and J.H. Waite, Jr. Eds, Amer. Geophys. U., Washington, D.C. p145, 1988.
Roth, I., M.K. Hudson, and R. Bergmann, Effects of ion two-stream instability on auroral ion heating, J. Geophys. Res., 94, 348-358, Jan. 1989.
Schriver, D., M. Ashour-Abdalla, H. L. Collin, and N. Lallande, Ion beam heating in the auroral zone, J. Geophys. Res., 95, 1015, 1990.
Winglee, R. M., P. L. Prictchett, P. B. Dusenbery, A. M. Persoon, J. H. Waite, Jr., T. E. Moore, J. L. Burch, H. L. Collin, J. A. Slavin, and M. Sugiura, Particle acceleration and wave emissions associated with the formation of auroral cavities and enhancements, J. Geophys. Res., 93, 14567, 1988.
Winglee, R.M., P.B. Dusenbery, H.L. Collin, A.M. Persoon, C.S. Lin and T.E. Moore, Simulations and observations of heating of auroral ion beams, J. Geophys. Res., 94, 8943, 1989.

Last updated October, 1995 by W.K. Peterson