Distribution of Interstellar Hydrogen Atoms in the Heliosphere and Backscattered Solar Lyman-α

Vladislav V. Izmodenov (1, 2) , Olga Katushkina (1, 2) , Eric Quémerais (3) , Maciej Bzowski (4)

1 MSU - Lomonosov Moscow State University
2 IKI - Space Research Institute of the Russian Academy of Sciences
3 HELIOS - LATMOS
4 CBK - Space Research Centre of Polish Academy of Sciences

We review the modern concepts of penetration of interstellar atoms of hydrogen into the heliosphere up to 1 AU. Before entering into the heliosphere the atoms penetrate through the region of the solar wind (SW) interaction with the local interstellar medium (LISM). In the interaction region the atoms can exchange charge with both solar wind and interstellar protons disturbed in the SW/LISM interaction region. Charge exchange results in a disturbance of the pristine interstellar atom flow in the interaction region, and, therefore, the parameters of interstellar gas inside the heliosphere are different from their interstellar values. This makes it more difficult to determine local interstellar parameters from measurements of the interstellar atoms inside the heliosphere, but, on the other side, opens possibilities to study the SW/LISM interaction region remotely. This paper overviews the main physical phenomena and modern models of the SW/LISM interaction and presents a state-of-art 3D kinetic model of the interstellar hydrogen gas inside the heliosphere. The distributions of the gas parameters are compared with the distributions obtained in the context of the classical hot model. Quantitative and qualitative differences are discussed. The state-of-art model is employed to calculate spectra of the backscattered Lyman- α radiation as they would be measured at 1 AU and the zero, first and second moments of the spectra. It is shown that the SW/LISM interaction imprints in the spatial and velocity distribution of the interstellar atoms are revealed in the intensities, line-shifts, and line-widths of the distribution functions. A qualitative comparison of the model results with SOHO/SWAN data are presented.

Domaines: Astrophysique stellaire et solaire [astro-ph.SR]; Astrophysique stellaire et solaire [astro-ph.SR]

Vladislav V. Izmodenov, Olga Katushkina, Eric Quémerais, Maciej Bzowski. Distribution of Interstellar Hydrogen Atoms in the Heliosphere and Backscattered Solar Lyman-α. Quémerais, Eric; Snow, Martin; Bonnet, Roger-Maurice. Cross-Calibration of Far UV Spectra of Solar System Objects and the Heliosphere, Springer, pp.7-65, 2013, ISSI Scientific Report Series, Vol. 13, 978-1-4614-6383-2. ⟨10.1007/978-1-4614-6384-9_2⟩. ⟨hal-00870080⟩