Observations of the Interplanetary Hydrogen during Solar Cycles 23 and 24. What can We Deduce about the Local Interstellar Medium?

Frédéric Vincent (1, 2) , Olga Katushkina (3) , Lotfi Ben-Jaffel (2) , Walter M. Harris (4) , Vladislav Izmodenov (5, 3) , Eric Quémerais (1) , Dimitra Koutroumpa (1) , John Clarke (6)

1 HELIOS - LATMOS
2 IAP - Institut d'Astrophysique de Paris
3 IKI - Space Research Institute of the Russian Academy of Sciences
4 LPL - Lunar and Planetary Laboratory [Tucson]
5 institute for Problems in Mechanics [Moscow]
6 CSP - Center for Space Physics [Boston]

Observations of interstellar helium atoms by the Interstellar Boundary Explorer (IBEX) spacecraft in 2009 reported a local interstellar medium (LISM) velocity vector different from the results of the Ulysses spacecraft between 1991 and 2002. The interplanetary hydrogen (IPH), a population of neutrals that fills the space between planets inside the heliosphere, carries the signatures of the LISM and its interaction with the solar wind. More than 40 yr of space-based studies of the backscattered solar Lyα emission from the IPH provided limited access to the velocity distribution, with the first temporal evolution map of the IPH line-shift during solar cycle 23. This work presents the results of the latest IPH observations made by the Hubble Space Telescope's Space Telescope Imaging Spectrograph during solar cycle 24. These results have been compiled with previous measurements, including data from the Solar Wind Anisotropies instrument on the Solar and Heliospheric Observatory. The whole set has been compared to physically realistic models to test both sets of LISM physical parameters as measured by Ulysses and IBEX, respectively. This comparison shows that the LISM velocity vector has not changed significantly since Ulysses measurements.

Mots clés: solar wind; Sun: activity; Sun: heliosphere; local interstellar matter; solar neighborhood; Sun: UV radiation

Domaines: Astrophysique stellaire et solaire [astro-ph.SR]; Astrophysique stellaire et solaire [astro-ph.SR]; Physique Atmosphérique et Océanique [physics.ao-ph]

Frédéric Vincent, Olga Katushkina, Lotfi Ben-Jaffel, Walter M. Harris, Vladislav Izmodenov, et al.. Observations of the Interplanetary Hydrogen during Solar Cycles 23 and 24. What can We Deduce about the Local Interstellar Medium?. The Astrophysical journal letters, 2014, 788 (2), pp.L25. ⟨10.1088/2041-8205/788/2/L25⟩. ⟨hal-00998272⟩