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

Poster (2011, July 11)

Mapping Jupiter's auroral features to magnetospheric sources: Comparing results from three different models for Jupiter's ionospheric magnetic field

Conference (2011, July 11)

Inside the Jupiter Main Auroral Emissions: Flares, Spots, Arc...and Satellite Footprints?

Conference (2011, July 11)

Grapes from Saturn : Focus on Saturn's main ring of emission with Cassini-UVIS

Conference (2011, July 11)

Improved mapping of Jupiter’s auroral features to magnetospheric sources

in Journal of Geophysical Research. Space Physics (2011), 116

The magnetospheric mapping of Jupiter's polar auroral emissions is highly uncertain because global Jovian field models are known to be inaccurate beyond ∼30 RJ. Furthermore, the boundary between open and ... [more ▼]

The magnetospheric mapping of Jupiter's polar auroral emissions is highly uncertain because global Jovian field models are known to be inaccurate beyond ∼30 RJ. Furthermore, the boundary between open and closed flux in the ionosphere is not well defined because, unlike the Earth, the main auroral oval emissions at Jupiter are likely associated with the breakdown of plasma corotation and not the open/closed flux boundary in the polar cap. We have mapped contours of constant radial distance from the magnetic equator to the ionosphere in order to understand how auroral features relate to magnetospheric sources. Instead of following model field lines, we map equatorial regions to the ionosphere by requiring that the magnetic flux in some specified region at the equator equals the magnetic flux in the area to which it maps in the ionosphere. Equating the fluxes in this way allows us to link a given position in the magnetosphere to a position in the ionosphere. We find that the polar auroral active region maps to field lines beyond the dayside magnetopause that can be interpreted as Jupiter's polar cusp; the swirl region maps to lobe field lines on the night side and can be interpreted as Jupiter's polar cap; the dark region spans both open and closed field lines and must be explained by multiple processes. Additionally, we conclude that the flux through most of the area inside the main oval matches the magnetic flux contained in the magnetotail lobes and is probably open to the solar wind. [less ▲]

Comparative magnetotail flapping: Overview of observations at Earth, Jupiter and Saturn

Conference (2011)

An overview of the aims and plans of an ISSI Team: Investigating the Dynamics of Planetary Magnetotails

Poster (2011)

Comparative Planetary Magnetotails

Poster (2011)

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

in Journal of Geophysical Research. Space Physics (2011), 116

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 ... [more ▼]

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. [less ▲]

Nightside reconnection at Jupiter: Auroral and magnetic field observations from 26 July 1998

in Journal of Geophysical Research. Space Physics (2011), 116

In this study we present ultraviolet and infrared auroral data from 26 July 1998, and we show the presence of transient auroral polar spots observed throughout the postdusk to predawn local time sector ... [more ▼]

In this study we present ultraviolet and infrared auroral data from 26 July 1998, and we show the presence of transient auroral polar spots observed throughout the postdusk to predawn local time sector. The polar dawn spots, which are transient polar features observed in the dawn sector poleward of the main emission, were previously associated with the inward moving flow resulting from tail reconnection. In the present study we suggest that nightside spots, which are polar features observed close to the midnight sector, are related to inward moving flow, like the polar dawn spots. We base our conclusions on the near-simultaneous set of Hubble Space Telescope (HST) and Galileo observations of 26 July 1998, during which HST observed a nightside spot magnetically mapped close to the location of an inward moving flow detected by Galileo on the same day. We derive the emitted power from magnetic field measurements along the observed plasma flow bubble, and we show that it matches the emitted power inferred from HST. Additionally, this study reports for the first time a bright polar spot in the infrared, which could be a possible signature of tail reconnection. The spot appears within an interval of 30 min from the ultraviolet, poleward of the main emission on the ionosphere and in the postdusk sector planetward of the tail reconnection x line on the equatorial plane. Finally, the present work demonstrates that ionospheric signatures of flow bursts released during tail reconnection are instantaneously detected over a wide local time sector. [less ▲]