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Session 7E - Space and Basic.
ORAL session, Thursday morning, November 14
Majestic Ballroom, Adam's Mark

[7E.02] Generation of X-Rays From Comet Hyakutake

R. Bingham (Rutherford Appleton Laboratory, Chilton, Dideot, Oxon, OX1100X), J.M. Dawson (Physics Department, University of California, Los Angeles, CA 90029), V.D. Shapiro, D.A. Mendis (Depts of Physics and Electrical Computer Engineering, University of California, San Diego, La Jolla, CA 92093), B.J. Kellet (Rutherford Appleton Laboratory)

An explanation of recent observations of a strong X-ray emission from comet Hyakutake (Science, 272, 194, 1996) is proposed. It is based on an idea that interaction between solar wind and photoionized cometary plasma produces strong plasma turbulence in the lower hybrid frequency range which is responsible for the acceleration of suprathermal electrons with the energies up to several keV. Estimations for the lower hybrid electric field, typical energies and fluxes of suprathermal electrons are obtained in the framework of quasilinear theory of the corresponding instability. Proposed scenario is compared with in-situ observations of wave and electron energy spectra during the encounter in 1986 of armada of spacecrafts with HalleyUs comet. Two possible mechanisms of producing X-Rays by energetic keV electrons are analyzed-bremsstrahlung and cometary gas (oxygen) K-shell radiation of X-Rays. It is shown that for conditions under investigation line K-shell radiation is dominant resulting in total comet luminosity in X-ray equal to 10^14 erg/s in agreement with Rossat observations.

Part 7 of program listing