TY - JOUR
T1 - Uranian H Ly‐α emission
T2 - The interstellar wind source
AU - Yelle, R. V.
AU - Sandel, B. R.
PY - 1986/2
Y1 - 1986/2
N2 - IUE observation of Uranian emissions in hydrogen Lyman alpha (H Ly‐α over, the past four years have recently been summarized by Clarke et al. [1985]. Over this time period they find an average H Ly‐α brightness of 1260 R which they estimate is composed of 200 R of solar scattered radiation and 1060 R from a collisional source. A third component, not considered by previous authors, is the reflection of H Ly‐α emissions from the interstellar wind. Hydrogen in the interstellar wind forms an extended source of H Ly‐α whose importance relative to the solar flux increases with distance from the sun. We demonstrate that scattering of interstellar H Ly‐α is more important than scattering of solar H Ly‐α for reasonable values of H column abundance and, in fact, may make up 10 ‐ 40% of the observed signal. Large H column abundances are still required to explain the H Ly‐α brightness solely on the basis of resonant scattering; therefore it is likely that the emissions are due in part to collisional sources and in part to the scattering of interstellar H Ly‐α with solar scattering playing a minor role.
AB - IUE observation of Uranian emissions in hydrogen Lyman alpha (H Ly‐α over, the past four years have recently been summarized by Clarke et al. [1985]. Over this time period they find an average H Ly‐α brightness of 1260 R which they estimate is composed of 200 R of solar scattered radiation and 1060 R from a collisional source. A third component, not considered by previous authors, is the reflection of H Ly‐α emissions from the interstellar wind. Hydrogen in the interstellar wind forms an extended source of H Ly‐α whose importance relative to the solar flux increases with distance from the sun. We demonstrate that scattering of interstellar H Ly‐α is more important than scattering of solar H Ly‐α for reasonable values of H column abundance and, in fact, may make up 10 ‐ 40% of the observed signal. Large H column abundances are still required to explain the H Ly‐α brightness solely on the basis of resonant scattering; therefore it is likely that the emissions are due in part to collisional sources and in part to the scattering of interstellar H Ly‐α with solar scattering playing a minor role.
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U2 - 10.1029/GL013i002p00089
DO - 10.1029/GL013i002p00089
M3 - Article
AN - SCOPUS:0022661049
VL - 13
SP - 89
EP - 92
JO - Geophysical Research Letters
JF - Geophysical Research Letters
SN - 0094-8276
IS - 2
ER -