The altitude of the FUV main auroral emissions at Jupiter B. BONFOND, J. GUSTIN, J.-C. GRARD, D....
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Transcript of The altitude of the FUV main auroral emissions at Jupiter B. BONFOND, J. GUSTIN, J.-C. GRARD, D....
The altitude of the FUV main auroral emissions at Jupiter
B. BONFOND, J. GUSTIN, J.-C. GÉRARD, D. GRODENT, A. RADIOTI, B. PALMAERTS, S. V. BADMAN, K. K. KHURANA AND C. TAO
Altitude above the limbBo
nfon
d et
al.,
200
9Va
sava
da e
t al.,
199
9
Main emissionVisible250 km
Io footprint tailFar-UV900 km
What about the altitude of the main emission in the far-UV?Is it the same as the visible one?
ME curtain above the limb
Bonf
ond
et a
l., a
ccep
ted
Peak altitude
Mean peak altitude: 400 km Higher than the 250 km
observed by Galileo
Bonf
ond
et a
l., a
ccep
ted
Fit of the brightness profile as a function of the electron energy distribution
MonoenergeticMaxwellianKappa
Bonfond et al., accepted
Hydrocarbon absorption
The peak altitude is strangely close to the methane homopauseTwo distributions peaking at different altitudes lead to similar observed profiles
Bonf
ond
et a
l., a
ccep
ted
Color ratio above the limb
Gérard et al., 2014
Color ratio above the limb
Because of the slit width, its inclination relative to the limb and C2H2 absorption, the color ratio remains low.
Bonf
ond
et a
l., a
ccep
ted
Peak shift in the spectra
15 spectral observationsMean shift: 90 km
Significant absorptionBonf
ond
et a
l., a
ccep
ted
Yet, two possibilities
Brightness
Altit
ude
400 km250 km
400 km400 km
ObservedObserved Emitted Emitted
Auroral curtain in the limb plane Auroral curtain behind the limb plane
Conclusions
The apparent brightness peak is at 400 km BUT CH4 absorption could explain such a profile BUT the color ratio is weak at the limb BUT C2H2 absorption + geometry can explain it
Spectra show an absorption signature nevertheless BUT the location of the spectral slit is uncertain
400 km represents an upper limit, but our observations are compatible with an peak altitude of 250 km.