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

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.
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Journal of Geophysical Research : Space Physics, American Geophysical Union/Wiley, A Paraître, 122 (11), pp.10,921-10,937. 〈10.1002/2017JA024205〉
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Contributeur : Catherine Cardon <>
Soumis le : vendredi 20 octobre 2017 - 17:31:01
Dernière modification le : jeudi 11 janvier 2018 - 06:27:17

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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, A Paraître, 122 (11), pp.10,921-10,937. 〈10.1002/2017JA024205〉. 〈insu-01620612〉

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