Collisions of highly-charged solar-wind ions with CO

Date of Completion

January 2008


Physics, Astronomy and Astrophysics




In 1996 the ROSAT satellite detected x-ray emissions from the atmosphere of comet Hyukatake [1]. Since then Cravens [2] explained these emissions as being the result of highly-charged heavy solar wind ions colliding with cometary gas molecules and undergoing charge-exchange interactions. Electrons are captured by the incoming ions into excited states. The consequent decays result in photon emission in the x-ray/vuv range. To study these reactions, ion beams are created in the laboratory and passed through CO, an important constituent gas of comet atmospheres. The resulting emissions are studied both the x-ray/vuv (1-70 nm) and the optical (400–800 nm) ranges. Ion beams of different charge states of O, N, C, S, Fe, and Si were used. The data shows that the dominant reaction creating the x-ray emissions is single electron capture and agrees very well with the predictions of the Classical Over-the-Barrier Model [3]. The dominant reaction creating optical emissions is target ionization and excitation, and single electron capture may play an important role here, too. ^