Resumen
Jupiter's polar aurora can be observed in several wavelength regions as
bright ovals off-center from the geographical poles of the planet and
co-rotating with the magnetic field (System III). Enhanced regions of
auroral activity are observed at selected longitudes. The north auroral
hot spot in particular is very strong and can be found between
165o}-200{o longitudes, while the less conspicuous
south auroral hot spot generally is found between
330o}-90{o longitudes. Recent UV and X-ray
observations of the northern aurora have shown that it varies in
intensity within minutes. IR spectral line intensity changes have also
been reported, but these observations have been sporadic and no
periodicity has been identified. Romani et al. (see related
presentation) recently observed a large decrease in
C2H4 emission from the north auroral hot spot
during a 48-hr period.
We report observation of changes in infrared line intensities during the
Cassini encounter with Jupiter. The thermal-IR spectroscopic
observations were performed by the Composite Infrared Spectrometer
(CIRS) at 0.3 cm-1 spectral resolution in the range 580
cm-1 - 1100 cm-1. The spectra were averaged on
two-week bins during Oct. 2000 - Mar. 2001 to increase S/N and were
restricted in longitude and latitude to cover both the auroral hot spot
and non-hot spot regions. We observed temporal variations in the
strength of the emission lines from important hydrocarbon species
(C2H2, C2H6,
C2H4, C6H6) on the hot spots
peaking in late January 2001. Non-hot spot longitudes of the aurora saw
little change during this same time interval. We compare the CIRS
results with our ground-based observations from the same period. The
line emission increments can be interpreted as due to temperature
enhancements in the stratosphere of the planet where these spectral
lines are formed. We characterize these variations and present
preliminary models that address the nature of these changes and may help
constrain auroral models.
Idioma original | English |
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Publicación | American Astronomical Society, DPS meeting #50 |
Volumen | 35 |
Estado | Published - 1 may 2003 |