Production of X-rays by comet Hyakutake

An explanation of recent observations of a strong X-ray emission from comet Hyakutake (Science , 194, 1996) is proposed. It is based on an idea that the interaction of the 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 energies in the range 100eV up to several keV. A nonlinear theory of the instability responsible for the generation of lower-hybrid electric field, typical energies and flux of suprathermal electrons are obtained. Two possible mechanisms of X-ray production by non-thermal energetic keV electrons are analyized; bremsstrahlung and cometary gas (mostly oxygen) K-shell line radiation. It is shown that for conditions under investigation line radiation is dominant resulting in total X-ray luminosity of 2.5 × 1015erg/sec in excellent agreement with ROSAT observed emission of 3.0 × 1015erg/sec.