Voyager 1/UVS Lyman α measurements at the distant heliosphere (90-130 AU): unknown source of additional emission

Olga A. Katushkina 1 Eric Quémerais 2 Vladislav V. Izmodenov 1, 3, 4 Rosine Lallement 5 Bill R. Sandel 6
1 IKI - Space Research Institute of the Russian Academy of Sciences
2 HEPPI - LATMOS
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
3 Faculty of Mechanics and Mathematics [Moscow]
4 institute for Problems in Mechanics [Moscow]
5 GEPI - Galaxies, Etoiles, Physique, Instrumentation
6 LPL - Lunar and Planetary Laboratory [Tucson]
Abstract : In this work, we present for the first time the Lyman α intensities measured by Voyager 1/UVS in 2003-2014 (at 90-130 AU from the Sun). During this period Voyager 1 measured the Lyman α emission in the outer heliosphere at an almost fixed direction close to the upwind (that is towards the interstellar flow). The data show an unexpected behavior in 2003-2009: the ratio of observed intensity to the solar Lyman α flux is almost constant. Numerical modelling of these data is performed in the frame of a state-of-art self-consistent kinetic-MHD model of the heliospheric interface (Izmodenov & Alexashov, 2015). The model results, for various interstellar parameters, predict a monotonic decrease of intensity not seen in the data. We propose two possible scenarios that explain the data qualitatively. The first is the formation of a dense layer of hydrogen atoms near the heliopause. Such a layer would provide an additional backscattered Doppler shifted Lyman α emission, which is not absorbed inside the heliosphere and may be observed by Voyager. About 35 R of intensity from the layer is needed. The second scenario is an external non-heliospheric Lyman α component, which could be galactic or extragalactic. Our parametric study shows that ∼25 R of additional emission leads to a good qualitative agreement between the Voyager 1 data and the model results.
Keywords : Heliopause Backscattered lyman alpha Radiation transfer Heliosphere Interstellar hydrogen
Document type :
Journal articles
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https://hal-insu.archives-ouvertes.fr/insu-01620612
Contributor : Catherine Cardon <>
Submitted on : Friday, October 20, 2017 - 5:31:01 PM
Last modification on : Friday, January 10, 2020 - 3:42:33 PM

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Olga A. Katushkina, Eric Quémerais, Vladislav V. Izmodenov, Rosine Lallement, Bill R. Sandel. Voyager 1/UVS Lyman α measurements at the distant heliosphere (90-130 AU): unknown source of additional emission. Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2017, 122 (11), pp.10,921-10,937. ⟨10.1002/2017JA024205⟩. ⟨insu-01620612⟩

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