A pulsating auroral X-ray hot spot on Jupiter (original) (raw)
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X-ray Emissions from the Jovian System
Bulletin of the Astronomical Society of India
X-ray emissions from Jupiter, discovered by Eisnsten observatory and followed up by ROSAT, have been thought to be excited by energetic and highly charged sulphur and oxygen ions precipitating from the inner magnetosphere into the planet's polar regions. However, recent observations by Chandra telescope have revealed surprising new results, including mysterious pulsating (period -45 minutes) x-ray hot spot in the northern polar regions of Jupiter, that have called into question our understainding of Jovian auroral x-rays. Further, x-rays from the moons of Jupiter -10, Europea, and probably Ganymede and from the 10 plasma torus have been discovered by the Chandra observatory. This paper presents a brief review of the x-ray emissions from the Jupiter, the Galilean satellites and the 10 plasma torus.
Low to middle-latitude X-ray emission from Jupiter
Journal of Geophysical Research, 2006
1] The Chandra X-ray Observatory (CXO) observed Jupiter during the period 24-26 February 2003 for 40hours(4Jupiterrotations),usingboththespectroscopyarrayoftheAdvancedCCDImagingSpectrometer(ACIS−S)andtheimagingarrayoftheHigh−ResolutionCamera(HRC−I).TwoACIS−Sexposures,each40 hours (4 Jupiter rotations), using both the spectroscopy array of the Advanced CCD Imaging Spectrometer (ACIS-S) and the imaging array of the High-Resolution Camera (HRC-I). Two ACIS-S exposures, each 40hours(4Jupiterrotations),usingboththespectroscopyarrayoftheAdvancedCCDImagingSpectrometer(ACIS−S)andtheimagingarrayoftheHigh−ResolutionCamera(HRC−I).TwoACIS−Sexposures,each8.5 hours long, were separated by an HRC-I exposure of 20hours.Thelow−tomiddle−latitudenonauroraldiskX−rayemissionismuchmorespatiallyuniformthantheauroralemission.However,thelow−tomiddle−latitudeX−raycountrateshowsasmallbutstatisticallysignificanthourangledependenceanddependsonsurfacemagneticfieldstrength.Inaddition,theX−rayspectrafromregionscorrespondingto3−5gaussand5−7gausssurfacefieldsshowsignificantdifferencesintheenergyband1.26−1.38keV,perhapspartlyduetolineemissionoccurringinthe3−5gaussregionbutnotthe5−7gaussregion.Asimilarcorrelationofsurfacemagneticfieldstrengthwithcountrateisfoundforthe18December2000HRC−Idata,atatimewhensolaractivitywashigh.Thelow−tomiddle−latitudediskX−raycountrateobservedbytheHRC−IintheFebruary2003observationisabout5020 hours. The low-to middle-latitude nonauroral disk X-ray emission is much more spatially uniform than the auroral emission. However, the low-to middle-latitude X-ray count rate shows a small but statistically significant hour angle dependence and depends on surface magnetic field strength. In addition, the X-ray spectra from regions corresponding to 3-5 gauss and 5-7 gauss surface fields show significant differences in the energy band 1.26-1.38 keV, perhaps partly due to line emission occurring in the 3-5 gauss region but not the 5-7 gauss region. A similar correlation of surface magnetic field strength with count rate is found for the 18 December 2000 HRC-I data, at a time when solar activity was high. The low-to middle-latitude disk X-ray count rate observed by the HRC-I in the February 2003 observation is about 50% of that observed in December 2000, roughly consistent with a decrease in the solar activity index (F10.7 cm flux) by a similar amount over the same time period. The low-to middle-latitude X-ray emission does not show any oscillations similar to the 20hours.Thelow−tomiddle−latitudenonauroraldiskX−rayemissionismuchmorespatiallyuniformthantheauroralemission.However,thelow−tomiddle−latitudeX−raycountrateshowsasmallbutstatisticallysignificanthourangledependenceanddependsonsurfacemagneticfieldstrength.Inaddition,theX−rayspectrafromregionscorrespondingto3−5gaussand5−7gausssurfacefieldsshowsignificantdifferencesintheenergyband1.26−1.38keV,perhapspartlyduetolineemissionoccurringinthe3−5gaussregionbutnotthe5−7gaussregion.Asimilarcorrelationofsurfacemagneticfieldstrengthwithcountrateisfoundforthe18December2000HRC−Idata,atatimewhensolaractivitywashigh.Thelow−tomiddle−latitudediskX−raycountrateobservedbytheHRC−IintheFebruary2003observationisabout5045 min oscillations sometimes seen from the northern auroral zone. The temporal variation in Jupiter's nonauroral X-ray emission exhibits similarities to variations in solar X-ray flux observed by GOES and TIMED/SEE. The two ACIS-S 0.3-2.0 keV low-to middle-latitude X-ray spectra are harder than the auroral spectrum and are different from each other at energies above 0.7 keV, showing variability in Jupiter's nonauroral X-ray emission on a timescale of a day. The 0.3-2.0 keV X-ray power emitted at low to middle latitudes is 0.21 GW and 0.39 GW for the first and second ACIS-S exposures, respectively. We suggest that X-ray emission from Jupiter's disk may be largely generated by the scattering and fluorescence of solar X rays in its upper atmosphere, especially at times of high incident solar X-ray flux. However, the dependence of count rate on surface magnetic-field strength may indicate the presence of some secondary component, possibly ion precipitation from radiation belts close to the planet.
Journal of Geophysical Research, 2005
1] Observations of Jupiter carried out by the Chandra Advanced CCD Imaging Spectrometer (ACIS-S) instrument over 24-26 February 2003 show that the auroral X-ray spectrum consists of line emission consistent with high-charge states of precipitating ions, and not a continuum as might be expected from bremsstrahlung. The part of the spectrum due to oxygen peaks around 650 eV, which indicates a high fraction of fully stripped oxygen in the precipitating ion flux. A combination of the OVIII emission lines at 653 eV and 774 eV, as well as the OVII emission lines at 561 eV and 666 eV, are evident in the measure auroral spectrum. There is also line emission at lower energies in the spectral region extending from 250 to 350 eV, which could be from sulfur and/or carbon. The Jovian auroral X-ray spectra are significantly different from the X-ray spectra of comets. The charge state distribution of the oxygen ions implied by the measured auroral X-ray spectra strongly suggests that independent of the source of the energetic ions, magnetospheric or solar wind, the ions have undergone additional acceleration. This spectral evidence for ion acceleration is also consistent with the relatively high intensities of the X rays compared with the available phase space density of the (unaccelerated) source populations of solar wind or magnetospheric ions at Jupiter, which are orders of magnitude too small to explain the observed emissions. The Chandra X-ray observations were executed simultaneously with observations at ultraviolet wavelengths by the Hubble Space Telescope and at radio wavelengths by the Ulysses spacecraft. These additional data sets suggest that the source of the X rays is magnetospheric in origin and that the precipitating particles are accelerated by strong field-aligned electric fields, which simultaneously create both the several-MeV energetic ion population and the relativistic electrons observed in situ by Ulysses that are correlated with $40 min quasi-periodic radio outbursts.
Jupiter's X‐ray Emission During the 2007 Solar Minimum
Journal of Geophysical Research: Space Physics, 2020
• Jupiter's equatorial X-ray emission varies in accordance with solar cycle 24 but auroral power can be comparably bright at solar min & max • Charge Exchange models provide good fits to aurora spectra retrieving S:O ratios of 0.4-1.3 agreeing with in-situ magnetosphere measurements • We report systematic differences between Chandra ACIS and XMM-Newton EPICpn Jovian spectra and the impact of these on opacity and quenching
Spectral morphology of the X-ray emission from Jupiter's aurorae
Journal of Geophysical Research, 2008
1] Simultaneous Chandra X-ray and Hubble Space Telescope FUV observations of Jupiter's aurorae carried out in February 2003 have been re-examined to investigate the spatial morphology of the X-ray events in different energy bands. The data clearly show that in the Northern auroral region (in the main auroral oval and the polar cap) events with energy > 2 keV are located at the periphery of those with energy < 2 keV and coincide with FUV bright features. In addition, X-ray spectra extracted from the areas where the two event distributions are concentrated possess different shapes. We associate the > 2 keV events ($45 MW emitted power) with the electron bremsstrahlung component recently revealed by XMM-Newton in the spectra of Jupiter's aurorae, and the < 2 keV emission ($230 MW) with the product of ion charge exchange, now established as the likely mechanism responsible for the soft X-ray Jovian aurora. We suggest that the same population of energetic electrons may be responsible for both, the X-ray bremsstrahlung and the FUV emission of Jupiter's aurorae. Comparison of the > 2 keV X-ray and FUV (340 GW) powers measured during the observations shows that they are broadly consistent with the predicted emissions from a population of energetic electrons precipitating in the planet's atmosphere, thus supporting our interpretation.
Thermal and Non-Thermal Components of the X-Ray Emission from Jupiter
Progress of Theoretical Physics Supplement, 2007
Recent XMM-Newton and Chandra observations have revealed that Jupiter's X-ray emission comprises both, thermal and non-thermal spectral components. While the emission from the low-latitude planetary disk has the properties of scattered solar X-rays, with a thermal spectrum and typical coronal emission lines, the auroral soft (< 2 keV) X-rays are thought to be produced by ion charge exchange; very recently, a higher energy auroral component has been revealed by XMM-Newton: this is attributed to energetic electron bremsstrahlung, is dominant above 2 keV, and is variable, displaying both thermal and non-thermal characteristics. The disk and soft X-ray auroral components are separated spectroscopically in the high resolution data provided by the XMM-Newton Reflection Grating Spectrometer. Our results on the morphology, dynamics and energetics of the aurorae support current models developed to explain Jupiter's complex magnetosphere.
Journal of Geophysical Research, 2010
1] Expanding upon recent work, a more comprehensive spectral model based on charge exchange induced X-ray emission by ions precipitating into the Jovian atmosphere is used to provide new understanding of the polar auroras. In conjunction with the Xspec spectral fitting software, the model is applied to analyze observations from both Chandra and XMM-Newton by systematically varying the initial precipitating ion parameters to obtain the best fit model for the observed spectra. In addition to the oxygen and sulfur ions considered previously, carbon is included to discriminate between solar wind and Jovian magnetospheric ion origins, enabled by the use of extensive databases of both atomic collision cross sections and radiative transitions. On the basis of fits to all the Chandra observations, we find that carbon contributes negligibly to the observed polar X-ray emission suggesting that the highly accelerated precipitating ions are of magnetospheric origin. Most of the XMM-Newton fits also favor this conclusion with one exception that implies a possible carbon contribution. Comparison among all the spectra from these two observatories in light of the inferred initial energies and relative abundances of precipitating ions from the modeling show that they are significantly variable in time (observation date) and space (north and south polar X-ray auroras).
Solar Control on Jupiter's Equatorial X-ray Emissions: 26-29 November 2003 XMM-Newton Observation
Geophysical Research Letters, 2005
1] During Nov. [26][27][28][29] 2003 XMM-Newton observed soft (0.2 -2 keV) X-ray emission from Jupiter for 69 hours. The low-latitude X-ray disk emission of Jupiter is observed to be almost uniform in intensity with brightness that is consistent with a solar-photon driven process. The simultaneous light curves of Jovian equatorial X rays and solar X rays (measured by the TIMED/SEE and GOES satellites) show similar day-to-day variability. A large solar X-ray flare occurring on the Jupiter-facing side of the Sun is found to have a corresponding feature in the Jovian X rays. These results support the hypothesis that X-ray emission from Jovian low-latitudes are solar X rays scattered from the planet's upper atmosphere, and suggest that the Sun directly controls the non-auroral X rays from Jupiter's disk. Our study also suggests that Jovian equatorial X rays can be used to monitor the solar X-ray flare activity on the hemisphere of the Sun that is invisible to space weather satellites.
X-Ray Emission from Jupiter, Saturn and Earth: A Short Review
2006
Jupiter, Saturn, and Earth -the three planets having dense atmosphere and a well developed magnetosphere -are known to emit X-rays. Recently, Chandra X-ray Observatory has observed X-rays from these planets, and XMM-Newton has observed them from Jupiter and Saturn. These observations have provided improved morphological, temporal, and spectral characteristics of X-rays from these planets. Both auroral and non-auroral (low-latitude) 'disk' X-ray emissions have been observed on Earth and Jupiter. X-rays have been detected from Saturn's disk, but no convincing evidence for X-ray aurora on Saturn has been observed. The non-auroral disk X-ray emissions from Jupiter, Saturn, and Earth, are mostly produced due to scattering of solar X-rays. X-ray aurora on Earth is mainly generated via bremsstrahlung from precipitating electrons and on Jupiter via charge exchange of highlyionized energetic heavy ions precipitating into the polar atmosphere. Recent unpublished work suggests that at higher (>2 keV) energies electron bremsstrahlung also plays a role in Jupiter's X-ray aurora. This paper summarizes the recent results of X-ray observations on Jupiter, Saturn, and Earth mainly in the soft energy (~0.1-2.0 keV) band and provides a comparative overview.