[Previous] | [Session 33] | [Next]
L. M. Trafton, D. F. Lester (U. Texas at Austin)
Jupiter's auroral cascade causes H2 emission in the near-IR quadrupole lines, in addition to the FUV emission. Unlike the FUV aurora, the near-IR aurora can be observed from ground-based observatories; and has in fact been observed as emission in the H2 (1-0) band in the spectra of Jupiter and Uranus (NASA SP-494, 229, 1989; ApJ 524, 1059, 1999). Unlike the near-IR H3+ aurora, which is formed by the reaction of H2 ionized by the cascade reacting with neutral H2, the H2 aurora can emit from atmospheric levels below the homopause, where H3+ would be destroyed by chemical reaction with hydrocarbons. H2 thus probes the auroral energy input at deeper levels. We present ground-based observations of Jupiter's auroral H2 emission from the (1-0) Q-branch taken from McDonald Observatory using the CoolSpec Cassegrain IR spectrometer at the 2.7m telescope. We discuss the rotational temperature and excited H2 column in the auroral arc for various extracted System III longitudes and compare the results to previous FUV H2 and near-IR H3+ observations of Jupiter and Uranus. Significant overpopulation of the v=1 vibrational level is found, compared to thermal equilibrium, due to the auroral cascade.
The author(s) of this abstract have provided an email address for comments about the abstract: lmt@astro.as.utexas.edu