The role of H+3 in planetary atmospheres

Steven Miller, Nick Achilleos, Gilda E. Ballester, Thomas R. Geballe, Robert D. Joseph, Renée Prangé, Daniel Rego, Tom Stallard, Jonathan Tennyson, Laurence M. Trafton, J. Hunter Waite

Research output: Contribution to journalArticlepeer-review

94 Scopus citations


Spectroscopic studies of the upper atmospheres of the giant planets using infrared wavelengths sensitive to the H+3 molecular ion show that this species plays a critical role in determining the physical conditions there. For Jupiter, we propose that the recently detected H+3 electrojet holds the key to the mechanism by which the equatorial plasma sheet is kept in (partial) co-rotation with the planet, and that this mechanism also provides a previously unconsidered source of energy that helps explain why the jovian thermosphere is considerably hotter than expected. For Saturn, we show that the H+3 auroral emission is ca. 1% of that of Jupiter because of the lower ionospheric/thermospheric temperature and the lower flux of ionizing particles precipitated there; it is probably unnecessary to invoke additional chemistry in the auroral/polar regions. For Uranus, we report further evidence that its emission intensity is controlled by the cycle of solar activity. And we propose that H+3 emission may just be detectable using current technology from some of the giant extra-solar planets that have been detected orbiting nearby stars, such as Tau Bootes.

Original languageEnglish (US)
Pages (from-to)2485-2502
Number of pages18
JournalPhilosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Issue number1774
StatePublished - 2000
Externally publishedYes


  • Atmospheres
  • Aurorae
  • Exoplanets
  • Giant planets
  • Ionospheres
  • Thermospheres

ASJC Scopus subject areas

  • Mathematics(all)
  • Engineering(all)
  • Physics and Astronomy(all)


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