X-ray emission from comets and nonmagnetic planets. Theory and comparison with CHANDRA observations

Mass loading of the solar wind by newly created cometary photoions as well as counterstreaming fluxes of protons in the mantle regions (at the ionospheric boundaries) of nonmagnetic planets (Mars, Venus) result in the modified two stream instability (MTSI) and excitation of the intense lower hybrid wave turbulence. Electrons are efficiently energized by these waves in the magnetic field aligned direction up to KeV energies (confirmed by in situ observations) and interacting with cometary or planetary atmospheres producing X-Ray emission by combination of Bremsstrahlung and line K-shell radiation. Analytical study of the nonlinear evolution of MTSI as well as numerical simulations of instability development in the mantle regions of nonmagnetic planets has been performed and it basically confirms the scenario of electron acceleration. Using the above described mechanism of X-ray emission produced in impacts of energetic electrons with ions and neutrals we employed ADAS-atomic data code to analyze X-ray spectrum emitted by comet Linear and obtained a good fit with recent CHANDRA observations. The theoretical model also predicts strong X-ray emission from nonmagnetic planets such as Mars and Venus.