Even though FOC images did not reveal a hot spot in the aurora, Trafton et
al., (1994) observed H
emission with the GHRS.
Individual rotational-vibrational lines of H
Lyman and Werner bands of the
northern aurora were resolved and yielded a rotational-vibrational temperature
of 530
100 K. This value is less than the H
value of 850-1100 K.
The proposed mechanism of exciting these cooler emissions is electron impact
excitation of H
from secondary particles which are generated when primary
particles precipitate into the atmosphere from the magnetosphere. Similar
results have been obtained by Clarke et al. (submitted to Astrophys.
J. Let., 1994).
Waite et al. (1994) and Gerard et al. (1994) obtained ultraviolet images of the southern and northern auroral zones in February 1992 during the Ulysses encounter. These data showed longitudinal variations in the intensity of the aurora. Although similar phenomena have been observed with IUE, the ultraviolet imaging capability of the WFPC-2 and the FOS, combined with the enhanced spatial and frequency resolution of the GHRS, provide an improved situation for ongoing investigation of the magnetosphere-ionosphere interactions.