The morphology of the X-ray emission above 2 keV from Jupiter's aurorae

Conference (2007, June 25)

Preliminary Results from Recent Simultaneous Chandra/HST Observations of Jupiter Auroral Zones

Poster (2003)

Jupiter was observed by the Chandra X-ray Observatory in late February, 2003, for 144 ks, using both the ACIS-S and HRC-I imaging x-ray cameras. Five orbits of HST STIS observations of the planet's ... [more ▼]

Jupiter was observed by the Chandra X-ray Observatory in late February, 2003, for 144 ks, using both the ACIS-S and HRC-I imaging x-ray cameras. Five orbits of HST STIS observations of the planet's northern auroral zone were obtained during the ACIS-S observations. These data are providing a wealth of information about Jupiter's auroral activity, including the first x-ray spectra from the x-ray hot spots inside the auroral ovals. We will also discuss time variability in the auroral x-ray emission and a possible phase relation between the emission from the northern and southern x-ray aurora. [less ▲]

Cassini UVIS Auroral Observations of Jupiter

Conference (2002, July 29)

Chandra X-ray Observations of the Jovian System

Conference (2002)

High-spatial resolution Chandra x-ray obsrvations have demonstrated that most of Jupiter's northern auroral x-rays come from a hot spot located significantly poleward of the latitudes connected to the ... [more ▼]

High-spatial resolution Chandra x-ray obsrvations have demonstrated that most of Jupiter's northern auroral x-rays come from a hot spot located significantly poleward of the latitudes connected to the inner magnetosphere. This hot spot appears fixed in magnetic latitude and longitude and coincides with a region exhibiting anomalous ultraviolet and infrared emissions. The hot spot also exhibited approximately 45 minute quasi-periodic oscillations, a period similar to those reported for high-latitude radio and energetic electron bursts observed by near-Jupiter spacecraft. These results invalidate the idea that jovian auroral x-ray emissions are mainly excited by steady precipitation of energetic heavy ions from the inner magnetosphere. Instead, the x-rays appear to result from currently unexplained processes in the outer magnetosphere that produce highly localized and highly variable emissions over an extremely wide range of wavelengths. The Chandra observations also revealed for the first time x-ray emission (about 0.1 GW) from the Io Plasma Torus, as well as very faint x-ray emission (about 1-2 MW) from the Galilean moons Io, Europa, and possibly Ganymede. The emission from the moons is almost certainly due to Kalpha emission of surface atoms (and possibly impact atoms) excited by the impact of highly energetic protons, oxygen, and sulfur atoms and ions from the Torus. The Torus emission is less well understood at present, although bremsstrahlung from the non-thermal tail of the electron distribution may provide a significant fraction. In any case, further observations, already accepted and in the process of being planned, with Chandra, some with the moderate energy resolution of the CCD camera, together with simultaneous Hubble Space Telescope observations and hopefully ground-based IRTF observations should soon provide greater insight into these various processes. [less ▲]

Cassini UVIS Observations of Jupiter's Auroral Variability

Poster (2001, October 27)

In the December 2000 Cassini flyby of the Jupiter system, the Cassini Ultraviolet Imaging Spectrograph (UVIS) monitored Jupiter's auroral emissions from day 275 of 2000 to day 81 of 2001. Much of the ... [more ▼]

In the December 2000 Cassini flyby of the Jupiter system, the Cassini Ultraviolet Imaging Spectrograph (UVIS) monitored Jupiter's auroral emissions from day 275 of 2000 to day 81 of 2001. Much of the auroral variability can be explained simply in terms of the rotation of Jupiter's auroral arcs (measured by Hubble Space Telescope) with the planet. However, several brightening events were seen in which the global auroral output increased by a factor of 2-4. These events persisted over a number of hours and are tied to large solar coronal mass ejection events. The auroral UV emissions from these bursts also correspond to hectometric radio emission increases reported by the Galileo and Cassini Radio and Plasma Wave experiments. The 2 largest events were on 2000 day 280 and on 2000 day 325-326. We will look at these events in some detail, and compare them with corresponding information on the interplanetary magnetic field, solar wind conditions, and energetic particle environment to try to understand the cause of these auroral brightness increases. [less ▲]

Jupiter's Thermospheric General Circulation Model (JTGCM): Equatorial thermal structure in comparison with Galileo probe measurements

Poster (2001, June 25)

Overview of Ionospheric-Magnetospheric Coupling at Jupiter: The Jovian Aurora

Conference (2001, June 25)

Jovian thermal structure inferred from the energy degradation of auroral electrons

in Bulletin of the American Astronomical Society (1999, October 10)

A one--dimensional model has been developed to investigate the links between auroral heat input and the atmospheric temperature and composition structure of Jupiter. Different energy distributions are ... [more ▼]

A one--dimensional model has been developed to investigate the links between auroral heat input and the atmospheric temperature and composition structure of Jupiter. Different energy distributions are used to evaluate the importance of the energy spectrum of the incident electrons for the thermal balance of Jupiter's auroral thermosphere. Radiative cooling by H_3(+) and hydrocarbon (CH_4, C_2H_2) and downward conduction are calculated to solve the heat conduction equation. The values of observable quantities such as the altitude of the H_2 emission peak, infrared (IR) and ultraviolet (UV) emissions and temperatures associated with H_2 and H_3(+) optical signatures are used to constrain the parameters of the auroral electron energy distributions. From these simulations, it appears that the precipitated auroral energy is not able to directly provide the necessary heat to balance the hydrocarbon cooling below the homopause. It is suggested however that the auroral upper stratosphere is warmer than the equatorial upper stratosphere measured by Galileo. A Maxwellian energy distribution with a total flux of 20 ergs cm(-2) s(-1) and a characteristic energy of 22 keV added to a soft Maxwellian component of 1 erg cm(-2) s(-1) and 350 eV produces results in good agreement with thermospheric observations. [less ▲]

Far ultraviolet Observations of Jovian low latitude regions with HST/STIS

in Bulletin of the American Astronomical Society (1999, September 01), 30(11),

Far ultraviolet observations of the Jovian disk were made at low and mid-latitudes with FUV MAMA/STIS on board HST in January 1999 both in the imaging and spectroscopic modes. An image was obtained with ... [more ▼]

Far ultraviolet observations of the Jovian disk were made at low and mid-latitudes with FUV MAMA/STIS on board HST in January 1999 both in the imaging and spectroscopic modes. An image was obtained with the Lyalpha filter in the hydrogen bulge region for comparison with the expected Lyman-alpha brightness distribution for Ly-alpha resonance scattering. Other images in the 1200-1700 { Angstroms} region show band structures parallel to the equator with fading contrast toward the center and the limb. Spectroscopic observations were made in the 1200-1700 { Angstroms} (G140L) and 1245-1298 { Angstroms} (G140M) regions at ~ 5 { Angstroms} resolution to map the H_2 airglow and the UV absorbents along the STIS slit. Preliminary results indicate that a C_2H_2 absorption signature is clearly observed in the solar ultraviolet reflected spectrum. The ethylene absorption may be mapped to derive variations of the acetylene abundance. The H_2 FUV airglow shows both the fluorescence and the electron impact components. Its spatial variation is described and compared with the expected airglow distribution. We acknowledge funding by NASA and by the PRODEX program of the European space agency. [less ▲]

HST-STIS Observations of Jupiter's Aurora

in Bulletin of the American Astronomical Society (1998, September 01)

HST observations of the UV emissions from Jupiter's aurora have been obtained with the new Space Telescope Imaging Spectrograph (STIS) since July 1997. UV images of the aurora are now possible with an ... [more ▼]

HST observations of the UV emissions from Jupiter's aurora have been obtained with the new Space Telescope Imaging Spectrograph (STIS) since July 1997. UV images of the aurora are now possible with an order of magnitude higher sensitivity than possible with earlier cameras, and improved angular resolution from shorter exposures. Images have been obtained at 4 epochs since Sept. 1997, and reveal several new features of the auroral emission pattern. These include i) faint auroral emissions extending roughly 60 deg. in the wake or plasma flow direction beyond Io's magnetic footprint, ii) systematic motions of the main auroral oval both toward the pole and toward the equator at different local times and longitudes, and iii) clear identification of an auroral emission feature with Ganymede's magnetic footprint, from the relative motion of the feature remaining underneath Ganymede in a time series of images. Preliminary interpretations of these features will be presented. Spectra have also been obtained of auroral emission features including the northern and southern main ovals, the diffuse emission poleward of the main oval, and the northern and southern Io footprints. These spectra will be presented with estimates of the overlying hydrocarbon columns, the energy of the exciting electrons, the rotational temperature of the emitting hydrogen, and the overlying column of atomic hydrogen. This work was supported by NASA under grants GO-6743.01-95A and GO-7308.01-96A to the University of Michigan. [less ▲]