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Vertical emissivity profiles of Jupiter's northern H-3(+) and H-2 infrared auroras observed by Subaru/IRCS

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  • T. Uno
  • Y. Kasaba
  • C. Tao
  • T. Sakanoi
  • M. Kagitani
  • S. Fujisawa
  • H. Kita
  • S. V. Badman
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<mark>Journal publication date</mark>12/2014
<mark>Journal</mark>Journal of Geophysical Research: Space Physics
Issue number12
Volume119
Number of pages23
Pages (from-to)10219-10241
<mark>State</mark>Published
Early online date3/12/14
<mark>Original language</mark>English

Abstract

We resolved the vertical emissivity profiles of H-3(+) overtone, H-3(+) hot overtone, and H-2 emission lines of the Jovian northern auroras in K band obtained in December 2011 observed by the IR Camera and Spectrograph of the Subaru 8.2m telescope with the adaptive optics system (AO188). The spatial resolution achieved was similar to 0.2 arcsec, corresponding to similar to 600 km at Jupiter. We derived the vertical emissivity profiles at three polar regions close to the Jovian limb. The H-3(+) overtone and H-3(+) hot overtone lines had similar peak altitudes of 700-900 km and 680-950 km above the 1 bar level, which were 100-300 km and 150-420 km lower, respectively, than the model values. On the contrary, the H-2 peak emission altitude was high, 590-720 km above the 1 bar level. It was consistent with the value expected for precipitation of similar to 1 keV electron, which favors a higher-altitude emissivity profile. We concluded that the lower peak altitudes of H-3(+) overtone and hot overtone lines were caused by the nonlocal thermodynamic equilibrium effect stronger than the model assumption. We could reproduce the observational emissivity profiles from the model by including this effect. It has been proposed that neutral H-2 and ionized H-3(+) emissions can have different source altitudes because of their different morphologies and velocities; however, our observed results with a general circulation model show that the peak emission altitudes of H-3(+) and H-2 can be similar even with different velocities.

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