The Cassini Ultraviolet Imaging Spectrograph Investigation

Esposito, L. W.; Barth, C. A.; Colwell, Joshua; Lawrence, G. M.; McClintock, W. E.; Stewart, A. I A N F.; Keller, H. U.; Korth, A.; Lauche, H.; Festou, M. C.; Lane, A. L.; Hansen, C. J.; Maki, J. N.; West, Robert A.; Jahn, Herbert; Reulke, Ralf; Warlich, K.; Shemansky, D. E.; Yung, Yuk L.

doi:10.1007/1-4020-3874-7_5

Cited by 41 publications

(44 citation statements)

References 136 publications

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“…The present work is based on auroral images taken with the UVIS instrument onboard Cassini. The narrow low‐resolution slit of the FUV channel (11.5–191.2 nm) of the UVIS spectrometer provides 64 spatial pixels of 1 by 1.5 mrad along and across the slit [ Esposito et al , 2004]. All projections assume that the auroral emission peaks at 1100 km above the surface, in agreement with [ Gérard et al , 2009].…”

Section: Bifurcations Of the Main Auroral Emissionmentioning

confidence: 80%

Bifurcations of the main auroral ring at Saturn: ionospheric signatures of consecutive reconnection events at the magnetopause

et al. 2011

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[1] This work reports for the first time on bifurcations of the main auroral ring at Saturn observed with the UVIS instrument onboard Cassini. The observation sequence starts with an intensification on the main oval, close to noon, which is possibly associated with dayside reconnection. Consecutive bifurcations appear with the onset of dayside reconnection, between 11 and 18 magnetic local time, while the area poleward of the main emission expands to lower latitudes. The bifurcations depart with time from the main ring of emission, which is related to the open-closed field line boundary. The augmentation of the area poleward of the main emission following its expansion is balanced by the area occupied by the bifurcations, suggesting that these auroral features represent the amount of newly open flux and could be related to consecutive reconnection events at the flank of the magnetopause. The observations show that the open flux along the sequence increases when bifurcations appear. Magnetopause reconnection can lead to significant augmentation of the open flux within a couple of days and each reconnection event opens ∼10% of the flux contained within the polar cap. Additionally, the observations imply an overall length of the reconnection line of ∼4 hours of local time and suggest that dayside reconnection at Saturn can occur at several positions on the magnetopause consecutively or simultaneously.

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Section: Bifurcations Of the Main Auroral Emissionmentioning

confidence: 80%

Bifurcations of the main auroral ring at Saturn: ionospheric signatures of consecutive reconnection events at the magnetopause

et al. 2011

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“…From these stellar observations we estimate the UVIS calibration uncertainty to be 15% or better for all wavelengths. A discussion of the UVIS instrument characteristics can be found in the work of Esposito et al [2004] and a discussion of the first EUV and FUV observations of Titan's disk from 13 December 2004 (Cassini Orbit TB) may be found in the work of Ajello et al [2007, 2008].…”

Section: The Uvis Limb Observationsmentioning

confidence: 99%

The production of Titan's ultraviolet nitrogen airglow

et al. 2011

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[1] The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed Titan's dayside limb in the extreme ultraviolet (EUV) and far ultraviolet (FUV) on 22 June 2009 from a mean distance of 23 Titan radii. These high-quality observations reveal the same EUV and FUV emissions arising from photoelectron excitation and photofragmentation of molecular nitrogen (N 2 ) as found on Earth. We investigate both of these solar driven processes with a terrestrial airglow model adapted to Titan and find that total predicted radiances for the two brightest N 2 band systems agree with the observed peak radiances to within 5%. Using N 2 densities constrained from in situ observations by the Ion Neutral Mass Spectrometer on Cassini, the altitude of the observed limb peak of the EUV and FUV emission bands is between 840 and 1060 km and generally consistent with model predictions. We find no evidence for carbon emissions in Titan's FUV airglow in contrast to previous Titan airglow studies using UVIS data. In their place, we identify several vibrational bands from the N 2 Vegard-Kaplan system arising from photoelectron impact with predicted peak radiances in agreement with observations. These Titan UV airglow observations are therefore comprised of emissions arising only from solar processes on N 2 with no detectable magnetospheric contribution. Weaker EUV Carroll-Yoshino N 2 bands within the v′ = 3, 4, and 6 progressions between 870 and 1020 Å are underpredicted by about a factor of five while the (0,1) band near 980 Å is overpredicted by about a factor of three.

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“…In this section we discuss the interplanetary data obtained by Cassini during the 2000–2001 flyby of Jupiter, which provides the context for the HST images. We consider data from the magnetic field instrument MAG [ Dougherty et al , 2004] and the CAPS plasma instrument [ Young et al , 2004], along with UVIS observations of UV aurora [ Esposito et al , 2004]. As an introduction to the data, and to provide a suitable background to this investigation, in Figure 1 we show data from days 275–342 of 2000, i.e., that studied by Pryor et al [2005] which immediately precedes the flyby interval covered by the HST campaign.…”

Section: Interplanetary Datamentioning

confidence: 99%

Response of Jupiter's UV auroras to interplanetary conditions as observed by the Hubble Space Telescope during the Cassini flyby campaign

et al. 2007

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[1] We provide a first detailed discussion of the relation between the set of Jovian UV auroral images observed by the Hubble Space Telescope (HST) in December 2000 to January 2001 and simultaneous interplanetary data obtained by Cassini during its Jupiter flyby. Examination of the interplanetary data surrounding all seven HST observation intervals shows that by chance six of them correspond to solar wind rarefaction regions, which follow compressions by periods of $2 to $6 days. Only one imaging interval, on 13 January 2001, corresponds to a compression region of generally elevated, but highly variable, solar wind dynamic pressure and interplanetary field strength. We have thus first examined the images corresponding to rarefaction regions in order to establish the range of behaviors that occur under these known conditions, which then act as a benchmark against which the compression region images can be compared. The rarefaction region images show relatively consistent properties of the main oval auroras, though differing in detail from interval to interval. The polar auroras show more variability, with the patchy (''swirl'') auroras in the central region sometimes forming a diffuse ring structure and at other times being more uniformly distributed, while the ''active region'' auroras at dusk vary markedly from weak emissions to bright arc-like forms, the latter possibly being associated with intervals within $2-3 days of a previous solar wind compression. The two images obtained in the compression region on 13 January 2001 then show remarkably different properties in all the auroral components. The main oval is found to be brighter over its whole length by factors of two to three compared with the rarefaction region images, while its position remains essentially unchanged, close to the usual reference oval. However, bright contiguous ''active region'' auroras in the postnoon and dusk sector then widen the overall auroral distribution in that sector by up to $5°in the poleward direction. The region of patchy polar auroras is also found to expand to cover essentially the whole of the remaining area of the polar cap, with a much-narrowed darker zone just poleward of the main oval in the dawn and prenoon sector. We discuss whether these enhanced emissions are characteristic of the few-day compression region as a whole or of more localized conditions occurring within the compression region and conclude that the latter is more likely. Examination of the relevant interplanetary data then shows that the brightened images are associated with an interval of significant magnetospheric dynamics, involving a modest compression of the magnetosphere followed by an extended major expansion.

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The Cassini Ultraviolet Imaging Spectrograph Investigation

Cited by 41 publications

References 136 publications

Bifurcations of the main auroral ring at Saturn: ionospheric signatures of consecutive reconnection events at the magnetopause

Bifurcations of the main auroral ring at Saturn: ionospheric signatures of consecutive reconnection events at the magnetopause

The production of Titan's ultraviolet nitrogen airglow

Response of Jupiter's UV auroras to interplanetary conditions as observed by the Hubble Space Telescope during the Cassini flyby campaign

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