Ionization of Interstellar Hydrogen Beyond the Termination Shock

[摘要] Models of solar wind interaction with the surrounding interstellar medium usually disregard ionization of interstellar hydrogen atoms beyond the solar wind termination shock. If and when included, the effects of ionization in the heliospheric interface region are often obscured by complexities of the interaction. This work assesses the importance of interstellar hydrogen ionization in the heliosheath. Photoionization could be accounted for in a straightforward way. In contrast, electron impact ionization is largely unknown because of poorly understood energy transfer to electrons at the termination shock and beyond. We first estimate the effect of photoionization and then use it as a yardstick to assess the role of electron impact ionization. The physical estimates show that ionization of interstellar hydrogen may lead to significant mass loading in the inner heliosheath which would slow down plasma flowing toward the heliotail and deplete populations of nonthermal protons, with the corresponding effect on heliospheric fluxes of energetic neutral atoms.

[发布机构] Department of Astronautical Engineering, University of Southern California, Los Angeles; CA; 90089-1192, United States^1

[效力级别] 天文学 [学科分类] 天文学(综合)

[关键词] Electron impact-ionization;Energetic neutral atoms;Heliospheric interfaces;Hydrogen atoms;Hydrogen ionization;Interstellar mediums;Solar wind interactions;Termination shocks