Relation between the short-term variation of the Jovian radiation belt and thermosphere derived from radio and infrared observations

Hajime Kita, Hiroaki Misawa, Anil Bhardwaj, Fuminori Tsuchiya, Takeshi Sakanoi, Yasumasa Kasaba, Chihiro Tao, Yoshizumi Miyoshi, Akira Morioka

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

We report the first comprehensive observations of Jovian synchrotron radiation (JSR) and H3+ emission from the Jovian thermosphere to investigate the generation process of short-term (days to weeks) variations in the Jovian radiation belt. The observations were made by the Giant Metrewave Radio Telescope and NASA Infrared Telescope Facility during November 2011. The total flux density of JSR increased by approximately 5% between 6-9 November and 12-17 November, associated with the increased solar UV/EUV flux. From 7 to 14 November, a possible rise in the infrared H3+ emission was observed in the middle-latitude region, corresponding to a temperature variation of approximately 10 K. These results are consistent with the scenario that the solar UV/EUV heating causes variations in the thermospheric temperature and JSR. Radio images along the equatorial region showed that the JSR intensity decreased inside 1.5 Jovian radii (RJ) and the peak position shifted outward. This implies that energetic electrons are attenuated by some internal loss process, despite the simultaneous increase in radial diffusion. A physical model for the radiation belt shows that such an internal loss process can explain the observed variation of brightness distribution. Typical loss time scale is longer than strong diffusion limit, which suggests the existence of some pitch angle diffusion process such as wave-particle interaction. Thus, variations of the total JSR flux density and thermospheric temperature seem consistent with the scenario, and the brightness distribution of JSR can be explained by the increase in radial diffusion accompanied by internal loss processes. Key Points First comprehensive study to reveal short-term changes in Jovian radiation belt Intensity of Jovian synchrotron radiation and H3+ varied with solar UV/EUV flux Increase in radial diffusion and internal loss process can explain radio image

Original languageEnglish
Pages (from-to)6614-6623
Number of pages10
JournalJournal of Geophysical Research: Space Physics
Volume120
Issue number8
DOIs
Publication statusPublished - 2015 Aug 1

Keywords

  • H3+ emission
  • Jovian radiation belt
  • Jovian thermosphere
  • synchrotron radiation

ASJC Scopus subject areas

  • Space and Planetary Science
  • Geophysics

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