Intervals of Intense Energetic Electron Beams Over Jupiter's Poles

Paranicas, C.; Mauk, B. H.; Haggerty, D. K.; Clark, G.; Kollmann, P.; Rymer, A. M.; Bonfond, Bertrand; Dunn, W. R.; Ebert, R. W.; Gladstone, G. R.; Roussos, E.; Krupp, N.; Bagenal, F.; Levin, S. M.; Connerney, J. E. P.; Bolton, S. J.

doi:10.1002/2017ja025106

Cited by 45 publications

(57 citation statements)

References 25 publications

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“…Prior to the arrival of NASA's Juno spacecraft at Jupiter, the wave-particle interaction processes responsible for auroral acceleration at the giant planets were nevertheless assumed to be similar to what is observed in the terrestrial magnetosphere. Contrary to the initial lack of such observations, later spacecraft passes indicated the presence of strong parallel electric fields, coherent particle acceleration, and inverted-V structures Mauk et al, 2018;Paranicas et al, 2018). Juno also observed ion conics on auroral field lines , which may be the result of field-aligned electron beams and the associated broadband whistler waves (Tetrick et al, 2017) similar to the those observed at Earth although at much higher energies.…”

Section: 1029/2019ja027403mentioning

confidence: 82%

Energetic Particle Signatures Above Saturn's Aurorae

et al. 2020

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Near the end of its mission, NASA's Cassini spacecraft performed several low-altitude passes across Saturn's auroral region. We present ultraviolet auroral imagery and various coincident particle and field measurements of two such passes, providing important information about the structure and dynamics of Saturn's auroral acceleration region. In upward field-aligned current regions, upward proton beams are observed to reach energies of several tens of keV; the associated precipitating electron populations are found to have mean energies of about 10 keV. With no significant wave activity being apparent, these findings indicate strong parallel potentials responsible for auroral acceleration, about 100 times stronger than at Earth. This is further supported by observations of proton conics in downward field-aligned current regions above the acceleration region, which feature a lower energy cutoff above ∼50 keV-indicating energetic proton populations trapped by strong parallel potentials while being transversely energized until they can overcome the trapping potential, likely through wave-particle interactions. A spacecraft pass through a downward current region at an altitude near the acceleration region reveals plasma wave features, which may be driving the transverse proton acceleration generating the conics. Overall, the signatures observed resemble those related to the terrestrial and Jovian aurorae, the particle energies and potentials at Saturn appearing to be significantly higher than at Earth and comparable to those at Jupiter.Plain Language Summary NASA's Cassini spacecraft orbited closer to Saturn than ever before during the last stage of its mission, the "Grand Finale". This allowed the onboard instruments to measure charged particles and plasma waves directly above the auroral region while simultaneously providing high-resolution imagery of the ultraviolet aurorae. Based on observations of highly energetic ions streaming away from the planet in regions of low plasma wave activity, we infer the existence of strong electric fields which act to accelerate electrons down into the atmosphere, driving the bright auroral emissions. Our estimates of the average energy of the precipitating electrons support this finding. Charged ions sometimes seem to be energized by plasma waves above the aurorae before they can escape, but the exact process in which this happens is not fully understood. Most signatures presented here resemble those observed in relation to Earth's aurorae, suggesting that the mechanisms acting at both planets are quite similar although Saturn's acceleration mechanism is significantly stronger.

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Section: 1029/2019ja027403mentioning

confidence: 82%

Energetic Particle Signatures Above Saturn's Aurorae

et al. 2020

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“…The downward flux remained less than the FUV with the exception of two spikes at 13:27 and 13:32. A high energy component ("penetrating radiation") is observed as described by Paranicas et al (2018) and Mauk et al (2018). We note that the magnetic mapping in this region may be less accurate than in other sectors.…”

Section: Journal Of Geophysical Research: Space Physicsmentioning

confidence: 85%

Contemporaneous Observations of Jovian Energetic Auroral Electrons and Ultraviolet Emissions by the Juno Spacecraft

et al. 2019

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We present comparisons of precipitating electron flux and auroral brightness measurements made during several Juno transits over Jupiter's auroral regions in both hemispheres. We extract from the ultraviolet spectrograph (UVS) spectral imager H 2 emission intensities at locations magnetically conjugate to the spacecraft using the JRM09 model. We use UVS images as close in time as possible to the electron measurements by the Jupiter Energetic Particle Detector Instrument (JEDI) instrument. The upward electron flux generally exceeds the downward component and shows a broadband energy distribution. Auroral intensity is related to total precipitated electron flux and compared with the energy-integrated JEDI flux inside the loss cone. The far ultraviolet color ratio along the spacecraft footprint maps variations of the mean energy of the auroral electron precipitation. A wide diversity of situations has been observed. The intensity of the diffuse emission equatorward of the main oval is generally in fair agreement with the JEDI downward energy flux. The intensity of the ME matches exceeds or remains below the value expected from the JEDI electron energy flux. The polar emission may be more than an order of magnitude brighter than associated with the JEDI electron flux in association with high values of the color ratio. We tentatively explain these observations by the location of the electron energization region relative to Juno's orbit as it transits the auroral region. Current models predict that the extent and the altitude of electron acceleration along the magnetic field lines are consistent with this assumption.The main auroral emission (ME) or "auroral oval" is a zone of emission encircling, sometimes only partially, Jupiter's magnetic poles. This "ring" of emission is rather stable on time scales of minutes to hours (Grodent,

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“…We believe the counts in this plot are due to electrons that come in through the JEDI collimator and then fully penetrate the SSD; this can occur for any electrons with energies >420 keV Paranicas et al, 2018). These electrons deposit only a fraction of their energy in the SSD.…”

Section: Io Flyby Datamentioning

confidence: 96%

“…We compare the data with findings of previous modeling that attempted to reproduce radial flux profiles of energetic charged particles measured by other spacecraft. We believe the counts in this plot are due to electrons that come in through the JEDI collimator and then fully penetrate the SSD; this can occur for any electrons with energies >420 keV Paranicas et al, 2018). Since JEDI was not designed to study Jupiter's radiation belts, we first discuss some features of the signal in the radiation belts.…”

Section: 1029/2019gl085393mentioning

confidence: 99%

Io's Effect on Energetic Charged Particles as Seen in Juno Data

Paranicas

Mauk

Haggerty

et al. 2019

Geophysical Research Letters

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On 12 February 2019, the Juno spacecraft crossed the particle drift shells (L shells) of the moon Io. The energetic particle detector, Jupiter Energetic Particle Detector Instrument (JEDI), found very low fluxes of energetic protons when the spacecraft was inward of about L~6.5. Recent modeling suggests wave-particle interactions may explain why energetic proton fluxes measured at these radial distances are low. JEDI also measured both a wide and a narrow decrease in the energetic electron count rate in Io's wake. At the time of this decrease, the JEDI detectors were dominated by 0.42 to 10-MeV electrons. The dimensions of the narrow count rate decrease are about three Io diameters and are unlikely to be caused by absorption by moon itself.

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Intervals of Intense Energetic Electron Beams Over Jupiter's Poles

Cited by 45 publications

References 25 publications

Energetic Particle Signatures Above Saturn's Aurorae

Energetic Particle Signatures Above Saturn's Aurorae

Contemporaneous Observations of Jovian Energetic Auroral Electrons and Ultraviolet Emissions by the Juno Spacecraft

Io's Effect on Energetic Charged Particles as Seen in Juno Data

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