Simultaneous Cassini VIMS and UVIS observations of Saturn's southern aurora

Conference (2012)

Multi‐spectral simultaneous observations of Saturn's aurorae in Jan. 2009

Conference (2012)

Cassini UVIS Observations of Varying Auroral Emissions on Saturn's Night Side

Poster (2011, July 11)

Bifurcations of the main auroral ring at Saturn: ionospheric signature of flux transfer events?

Conference (2011, April)

Saturn's radio, UV and IR aurorae observed simultaneously by Cassini

in European Planetary Science Congress 2010 (2010, September 01)

Not Available

Saturn's polar auroral emissions

Conference (2010)

Not Available

Response of Jupiter's and Saturn's auroral activity to the solar wind

in Journal of Geophysical Research. Space Physics (2009), 114

While the terrestrial aurorae are known to be driven primarily by the interaction of the Earth's magnetosphere with the solar wind, there is considerable evidence that auroral emissions on Jupiter and ... [more ▼]

While the terrestrial aurorae are known to be driven primarily by the interaction of the Earth's magnetosphere with the solar wind, there is considerable evidence that auroral emissions on Jupiter and Saturn are driven primarily by internal processes, with the main energy source being the planets' rapid rotation. Prior observations have suggested there might be some influence of the solar wind on Jupiter's aurorae and indicated that auroral storms on Saturn can occur at times of solar wind pressure increases. To investigate in detail the dependence of auroral processes on solar wind conditions, a large campaign of observations of these planets has been undertaken using the Hubble Space Telescope, in association with measurements from planetary spacecraft and solar wind conditions both propagated from 1 AU and measured near each planet. The data indicate a brightening of both the auroral emissions and Saturn kilometric radiation at Saturn close in time to the arrival of solar wind shocks and pressure increases, consistent with a direct physical relationship between Saturnian auroral processes and solar wind conditions. At Jupiter the correlation is less strong, with increases in total auroral power seen near the arrival of solar wind forward shocks but little increase observed near reverse shocks. In addition, auroral dawn storms have been observed when there was little change in solar wind conditions. The data are consistent with some solar wind influence on some Jovian auroral processes, while the auroral activity also varies independently of the solar wind. This extensive data set will serve to constrain theoretical models for the interaction of the solar wind with the magnetospheres of Jupiter and Saturn. [less ▲]

Characteristics of Saturn's polar atmosphere and auroral electrons derived from HST/STIS, FUSE and Cassini/UVIS spectra

Poster (2008, December 01)

Ultraviolet spectra of Saturn's aurora obtained with the Hubble Space Telescope Imaging Spectrograph (STIS), the Cassini Ultraviolet Imaging Spectrograph (UVIS) and the Far Ultraviolet Spectroscopic ... [more ▼]

Ultraviolet spectra of Saturn's aurora obtained with the Hubble Space Telescope Imaging Spectrograph (STIS), the Cassini Ultraviolet Imaging Spectrograph (UVIS) and the Far Ultraviolet Spectroscopic Explorer (FUSE) have been compared to synthetic spectra of electron-excited H2 in order to derive various auroral characteristics, such as the energy of the primary precipitating electrons and the H2 temperature at the altitude of the aurora. Two physical processes have been exploited: the absorption by hydrocarbons in the FUV and H2 self-absorption in the EUV. We find energies in the range 10-18 keV, which locates Saturns's aurora between 0.1 and 0.3 μ bar. We also determined that the auroral H2 emission is characterized by a temperature of ~400K, consistent with temperatures measured in the infrared, but much higher than what is expected from equatorial atmospheric models. These new results bring valuable constraints on both polar atmospheric models and theoretical studies of the ionosphere-magnetosphere coupling. [less ▲]

Titan Airglow Spectra from Cassini UVIS

Conference (2007, December 01)

We present the first UV airglow observations of Titan's atmosphere by the Ultraviolet Imaging Spectrograph (UVIS) on Cassini. The known UV emissions of Titan have been examined with higher spectral ... [more ▼]

We present the first UV airglow observations of Titan's atmosphere by the Ultraviolet Imaging Spectrograph (UVIS) on Cassini. The known UV emissions of Titan have been examined with higher spectral resolution (0.4 nm FWHM) by the Cassini UVIS than in the past by the Voyager Ultraviolet Spectrometer (UVS) (3.0 nm FWHM). The UVIS observations, confirming Voyager UVS results, have shown that molecular nitrogen is the major constituent of the upper atmosphere of Titan. Using one spectral channel in the EUV from 56--118 nm and one in the FUV from 112--191 nm, the UVIS observed the disk on 13 December, 2004. The combined EUV and FUV spectral region is a probe of the stratosphere-mesosphere-thermosphere-exosphere region from about 300--2000 km. The EUV spectrum consists of three band systems of N2 (b {1}Πu, b' {1}Σu+, c{4'} {1}Σ{u+}--X {1}Σ{g+}), while the FUV spectrum consists of one N2 (a {1}Πg--X {1}Σ{g+}). The UVIS observations reveal that the c{4'}(0)--X(0) vibrational band near 95.8 nm is suppressed, and that N \sc{i} multiplets near 95.32 and 96.45 nm are present instead. Magnetospheric particle excitation is weak on this orbit, since the nightside EUV spectrum shows no observable N2 emission features and only H Lyman-β. The absence of significant darkside emission demonstrates that nitrogen emissions are predominantly excited on this orbit by photoelectrons near 900 km in the thermosphere. Above 145 nm most of the observed signal is due to sunlight reflected by N2 in the Titan mesosphere-stratosphere and modified by aerosol and hydrocarbon absorption. Mixing ratios of C2H2, C4H2, C2H4 and tholins have been derived from the reflected sunlight emission between 145 and 190 nm, using a Rayleigh scattering model. Assuming that the energy deposition at these wavelengths occurs near 300 km, these mixing ratios are in good agreement with recent photochemical models and previous Voyager observations in the IR. We also present the first geometric albedo measurement of Titan from 150--190 nm. [less ▲]

HST UV Imaging of Saturn's Southern Aurora during Simultaneous Cassini Imaging of the Northern Aurora

Conference (2005, May 01)

On 17 Feb. 2005, one week after the AGU abstract deadline, Hubble Space Telescope (HST) observations are scheduled with the Advanced Camera for Surverys (ACS) to image Saturn's UV aurora for a period of 5 ... [more ▼]

On 17 Feb. 2005, one week after the AGU abstract deadline, Hubble Space Telescope (HST) observations are scheduled with the Advanced Camera for Surverys (ACS) to image Saturn's UV aurora for a period of 5 HST orbits, or 8 hours, corresponding to 0.7 of one Saturn rotation. In the present epoch, observations from the Earth can observe nearly the entire southern auroral oval in sunlight, but none of the northern oval, due to the tilt of Saturn's axis. Over the same period, a Cassini imaging sequence will scan across the northern nightside auroral emission region from the nightside of the planet. This presents a unique opportunity to determine the relationship between the conjugate points in the auroral emission regions, along with charged particle and magnetic field measurements in the nightside Saturn magnetosphere. This campaign of observations will be presented in this paper, with a concentration on the HST images, along with scientific conclusions as appropriate. [less ▲]