Jupiter's polar auroral emissions (original) (raw)
Related papers
Variation of different components of Jupiter's auroral emission
Journal of Geophysical Research, 2009
1] The Hubble Space Telescope (HST) data set obtained over two campaigns in 2007 is used to determine the long-term variability of the different components of Jupiter's auroras. Three regions on the planet's disc are defined: the main oval, the low-latitude auroras, and the high-latitude auroras. The UV auroral power emitted from these regions is extracted and compared to estimated solar wind conditions projected to Jupiter's orbit from Earth. In the first campaign the emitted power originated mainly from the main oval and the high-latitude regions, and in the second campaign the high-latitude and main oval auroras were dimmer and less variable, while the low-latitude region exhibited bright, patchy emission. We show that, apart from during specific enhancement events, the power emitted from the poleward auroras is generally uncorrelated with that of the main oval. The exception events are dawn storms and compression region enhancements. It is shown that the former events, typically associated with intense dawnside main oval auroras, also result in the brightening of the high-latitude auroras. The latter events associated with compression regions exhibit a particular auroral morphology; that is, where it is narrow and well defined, the main oval is bright and located $1°poleward of its previous location, and elsewhere it is faint. Instead there is bright emission in the poleward region in the postnoon sector where distinct, bright, sometimes multiple arcs form.
Hubble observations of Jupiter’s north–south conjugate ultraviolet aurora
Icarus, 2013
Comparisons of the northern and southern far ultraviolet (UV) auroral emissions of Jupiter from the Hubble Space Telescope (HST) or any other ultraviolet imager have mostly been made so far on a statistical basis or were not obtained with high sensitivity and resolution. Such observations are important to discriminate between different mechanisms responsible for the electron acceleration of the different components of the aurora such as the satellite footprints, the «main oval» or the polar emissions. The field of view of the ACS and STIS cameras on board HST is not wide enough to provide images of the full jovian disk. We thus compare the morphology of the north and south aurora observed 55 min apart and we point out similarities and differences. On one occasion HST pointed successively the two polar regions and auroral images were seen separated by only 3 min. This makes it possible to compare the emission structure and the emitted FUV power of corresponding regions. We find that most morphological features identified in one hemisphere have a conjugate counterpart in the other hemisphere. However, the power associated with conjugate regions of the main oval, diffuse or discrete equatoward emission observed quasi-simultaneously may be different in the two hemispheres. It is not directly nor inversely proportional to the strength of the B-field as one might expect for diffuse precipitation or field-aligned acceleration with equal ionospheric electron density in both hemispheres. Finally, the lack of symmetry of some polar emissions suggests that some of them could be located on open magnetic field lines.
Journal of Geophysical Research: Space Physics, 2021
Jupiter's polar auroral region hosts UV auroral emissions that relate to the magnetospheric dynamics from the outer magnetosphere. Juno‐UVS has discovered intriguing features characterized by expanding emission circles of UV‐brightness <140 kR. These events are located at the border of the previously defined swirl region, nearby the polar dark region. The features expand into a circular shape up to ∼1,000 km in radius, at expansion velocities from 3.3 ± 1.7 up to 7.7 ± 3.5 km/s, as measured over the four best observed cases. Using color ratio measurements as a proxy for the depth of the recorded features, the mean electron energy responsible for these emissions is 80–160 keV. Events occurring in the outer magnetosphere at distances >100 RJ are likely causing for these features. Dayside magnetopause reconnection and Kelvin‐Helmholtz instabilities resulting from the shear flows near the magnetopause are expected to generate field‐aligned currents that could potentially be th...
The far-ultraviolet main auroral emission at Jupiter – Part 2: Vertical emission profile
Annales Geophysicae, 2015
The aurorae at Jupiter are made up of many different features associated with a variety of generation mechanisms. The main auroral emission, also known as the main oval, is the most prominent of them as it accounts for approximately half of the total power emitted by the aurorae in the ultraviolet range. The energy of the precipitating electrons is a crucial parameter to characterize the processes at play which give rise to these auroral emissions, and the altitude of the emissions directly depends on this energy. Here we make use of far-UV (FUV) images acquired with the Advanced Camera for Surveys on board the Hubble Space Telescope and spectra acquired with the Space Telescope Imaging Spectrograph to measure the vertical profile of the main emissions. The altitude of the brightness peak as seen above the limb is ~ 400 km, which is significantly higher than the 250 km measured in the post-dusk sector by Galileo in the visible domain. However, a detailed analysis of the effect of hy...
A Remarkable Auroral Event on Jupiter Observed in the Ultraviolet with the Hubble Space Telescope
Science, 1994
Two sets of ultraviolet images of the Jovian north aurora were obtained with the Faint Object Camera on board the Hubble Space Telescope. The first series shows an intense discrete arc in near corotation with the planet. The maximum apparent molecular hydrogen emission rate corresponds to an electron precipitation of -1 watt per square meter, which is about 30,000 times larger than the solar heating by extreme ultraviolet radiation. Such a particle heating rate of the auroral upper atmosphere of Jupiter should cause a large transient temperature increase and generate strong thermospheric winds. Twenty hours after initial observation, the discrete arc had decreased in brightness by more than one order of magnitude. The time scale and magnitude of the change in the ultraviolet aurora leads us to suggest that the discrete Jovian auroral precipitation is related to large-scale variations in the current system, as is the case for Earth's discrete aurorae.
Journal of Geophysical Research A: Space Physics, 2013
1] We compare Jupiter's northern auroral emissions in infrared (IR) and ultraviolet (UV) using ground-based IR observations from the NASA Infrared Telescope Facility and UV observations from Hubble Space Telescope on 16 December 2000, the only date for which simultaneous observations in the two wavelength regions exist. We use polar projections and longitudinal brightness cuts to compare the IR (H + 3 ions) and UV (H 2 , H, and Lyman-alpha) aurorae, consisting of the main auroral emission, emission regions both poleward and equatorward of the main emission, and those associated with the Io footprint and its extended tail. We demonstrate that (1) the IR main emission and the equatorward diffuse emissions are generally good proxies for the UV and vice versa, (2) the spatial distribution and temporal behavior of UV and IR emissions within the main emission, at high magnetic latitudes, differ substantially, (3) UV and IR emissions associated with the Io interaction appear at the Io footprint and along an extended (downstream) tail but differ in relative brightness. While the UV aurora is excited directly, the IR aurora is a thermal emission, its intensity depends on both the number density of the H + 3 ions and the temperature. Three main factors may contribute to the observed morphological differences of the simultaneous emissions in the two wavelengths, namely ion transport, local heating, and the energy of the precipitating electrons. We estimate the H + 3 ion transport distances, based on the ion lifetime and suggest that ion transport cannot account for large-scale morphological differences between the UV and IR emissions. We propose that neutral gas heating by particle precipitation and Joule heating locally enhances the H + 3 emission with no UV counterpart. Additionally, we estimate that local temperature variations are reflected in the IR emission with a time lag of several hours with respect to the UV. Finally, high precipitating electron energies exceeding a certain value might lead to chemical loss of the low altitude H + 3 ions, suppress the lower IR emitting layers, and contribute to the observed differences of the emissions between the two wavelength regimes. Citation: Radioti, A., M. Lystrup, B. Bonfond, D. Grodent, and J.-C. Gérard (2013), Jupiter's aurora in ultraviolet and infrared: Simultaneous observations with the Hubble Space Telescope and the NASA Infrared Telescope Facility,
Multispectral observations of Jupiter's aurora
Advances in Space Research, 2000
Remote sensing of Jupiter's aurora from x-ray to radio wavelengths has revealed much about the nature of the jovian aurora and about the impact of ionosphere-magnetosphere coupling on the upper atmosphere of Jupiter. As indicated by the combination of x-ray and ultraviolet observations, both energetic heavy ions and electrons energized in the outer magnetosphere contribute to aurora1 excitation. Imaging with the Hubble Space Telescope in the ultraviolet and with the InfraRed Telescope Facility at infrared wavelengths shows several distinct regions of interaction: 1) a dusk sector where turbulent aurora1 patterns extend well into the polar cap; 2) a morning sector generally characterized by a single spatially confined aurora1 arc originating in the outer or middle magnetosphere of Jupiter; 3) diffuse emissions associated with the lo plasma -spectroscopy has provided important information about the thermal structure of Jupiter's aurora1 atmosphere and the altitude distribution of aurora1 particle energy deposition, while Lyman alpha line profiles yield clues to the nature of thermospheric dynamical effects. Galileo observations at visible wavelengths on the nightside offer a new view of the jovian aurora with unprecedented spatial information.
Models of Jupiter's Polar Aurora
Proquest Dissertations and Theses Thesis University of Kansas 2012 Publication Number Aat 3541830 Isbn 9781267686121 Source Dissertation Abstracts International Volume 74 03 Section B 446 P, 2012
Auroral emissions from Jupiter have been observed across the photon spectrum including ultraviolet and x-ray wavelengths. UV observations suggest an input flux power of 10 13 − 10 14 W for the aurora in each hemisphere. X-ray emissions with a total power of about 1 GW were observed by the Einstein Observatory, the Roentgen satellite, Chandra x-ray Observatory (CXO), and XMM-Newton. Previous theoretical studies have shown that precipitating energetic sulfur and oxygen ions can produce the observed xrays. This study focuses on the ion precipitation of the polar region and its effects in I would like to acknowledge and thank my advisor T. E. Cravens for his guidance during my graduate studies. I would like to thank D. R. Schultz for calculating the cross sections that made our models possible. I would also like to thank Tizby Hunt-Ward for all her help with my work. I would also like to acknowledge and thank my family and my husband for all the help and support they provided that allowed me to complete this work.
Journal of Geophysical Research, 2007
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 Dec 2000-Jan 2001 and simultaneous interplanetary data obtained by Cassini during its Jupiter fly-by. Examination of the interplanetary 35 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 Jan 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 40 behaviours 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.