Weakening of Jupiter's main auroral emission during January 2014

Bonfond, Bertrand; Fujimoto, M.; Gray, R.J.; Kasaba, Yasumasa; Kasahara, Satoshi; Kimura, Tomoki; Melin, Henrik; Nichols, J. D.; Steffl, A. J.; Tao, Chihiro; Tsuchiya, F.; Yamazaki, Atsushi; Yoneda, Mizuki; Yoshikawa, Ichiro; Yoshioka, Kazuo

doi:10.1002/2015gl067366

Cited by 37 publications

(45 citation statements)

References 55 publications

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“…The image taken on DOY140 is shown as a representative for the quiet period (Figure b). Between 02:17:42 and 03:02:12 (DOY142.10–142.13) on DOY142 (Figures c–e), a dawn storm, which is suggestive of dawnside tail reconnection and planetward return flow [ Cowley et al , ; Clarke et al , ], was evident at System III longitude of 180°–260° less than in the main oval (Figures c–e) as observed during the 2014 HST campaign [ Kimura et al , ; Badman et al , ; Gray et al , ]. This exposure time corresponds to the onset timing of the transient aurora in the Hisaki data.…”

Section: Resultsmentioning

confidence: 91%

“…The simultaneous imaging by the Hubble Space Telescope (HST) with Hisaki indicated that the three structures introduced above, the main oval, poleward emissions, and outer emission, were enhanced simultaneously around the transient aurora [ Kimura et al , ; Badman et al , ; Gray et al , ]. However, the temporal and spatial evolutions of the transient aurora and energetic events were not resolved by these previous observations because of the lack of continuous monitoring that spans the typical duration of the transient aurora.…”

Section: Introductionmentioning

confidence: 99%

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Transient brightening of Jupiter's aurora observed by the Hisaki satellite and Hubble Space Telescope during approach phase of the Juno spacecraft

Kimura

Nichols

Gray

et al. 2017

Geophysical Research Letters

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In early 2014, continuous monitoring with the Hisaki satellite discovered transient auroral emission at Jupiter during a period when the solar wind was relatively quiet for a few days. Simultaneous imaging made by the Hubble Space Telescope (HST) suggested that the transient aurora is associated with a global magnetospheric disturbance that spans from the inner to outer magnetosphere. However, the temporal and spatial evolutions of the magnetospheric disturbance were not resolved because of the lack of continuous monitoring of the transient aurora simultaneously with the imaging. Here we report the coordinated observation of the aurora and plasma torus made by Hisaki and HST during the approach phase of the Juno spacecraft in mid‐2016. On day 142, Hisaki detected a transient aurora with a maximum total H2 emission power of ~8.5 TW. The simultaneous HST imaging was indicative of a large “dawn storm,” which is associated with tail reconnection, at the onset of the transient aurora. The outer emission, which is associated with hot plasma injection in the inner magnetosphere, followed the dawn storm within less than two Jupiter rotations. The monitoring of the torus with Hisaki indicated that the hot plasma population increased in the torus during the transient aurora. These results imply that the magnetospheric disturbance is initiated via the tail reconnection and rapidly expands toward the inner magnetosphere, followed by the hot plasma injection reaching the plasma torus. This corresponds to the radially inward transport of the plasma and/or energy from the outer to the inner magnetosphere.

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Section: Resultsmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Transient brightening of Jupiter's aurora observed by the Hisaki satellite and Hubble Space Telescope during approach phase of the Juno spacecraft

Kimura

Nichols

Gray

et al. 2017

Geophysical Research Letters

Self Cite

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“…The dataset of the previous Jupiter observation campaign from December 2013 to January 2014 includes short-term (not longer than one Jovian planetary rotation) aurora intensifications under quiet SW conditions Badman et al 2016). These shortduration events were regarded as internally driven compared with intensifications lasting for more than 2 days under high SW pressure conditions, which were defined as externally driven .…”

Section: Discussionmentioning

confidence: 99%

Volcanic activity on Io and its influence on the dynamics of the Jovian magnetosphere observed by EXCEED/Hisaki in 2015

Yoshikawa

Suzuki

Hikida

et al. 2017

Earth Planets Space

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Jupiter's moon Io, which orbits deep inside the magnetosphere, is the most geologically active object in the solar system. Kurdalagon Patera, a volcano on Io, erupted in 2015 and became a substantial source of Jovian magnetospheric plasma. Based on Earth-orbiting spacecraft observations, Io plasma torus (IPT) exhibited the peak intensity (nearly double) of ionic sulfur emissions roughly 2 month later, followed by a decay phase. This environmental change provides a unique opportunity to determine how the more heavily loaded magnetosphere behaves. Indeed, the extreme ultraviolet spectroscope for exospheric dynamics onboard the Earth-orbiting spacecraft Hisaki witnessed the whole interval via aurora and IPT observations. A simple-minded idea would be that the centrifugal force acting on fast co-rotating magnetic flux tubes loaded with heavier contents intensifies their outward transport. At the same time, there must be increased inward convection to conserve the magnetic flux. The latter could be accompanied by (1) increased inward velocity of field lines, (2) increased frequency of inward transport events, (3) increased inward flux carried per event, or (4) combinations of them. The Hisaki observations showed that the densities of major ions in the IPT increased and roughly doubled compared with pre-eruption values. The hot electron fraction, which sustains the EUV radiation from the IPT, gradually increased on a timescale of days. Pairs of intensified aurora and IPT brightening due to the enhanced supply of hot electrons from the mid-magnetosphere to the IPT upon aurora explosions observed during both quiet and active times, enabled the study of the mid-magnetosphere/IPT relationship. Hisaki observations under active Io conditions showed that: (1) the hot electron fraction in the torus gradually increased; (2) brightening pairs were more intense; (3) the energy supplied by the largest event maintained enhanced torus emission for less than a day; (4) the time delay of a torus brightening from a corresponding aurora intensification was roughly 11 h, that is, the same as during quiet times, suggesting that the inward convection speed of high-energy electrons does not change significantly.

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“…An example of the main oval dominated control of the total auroral power can be found in the HST observation in Badman et al [2016], in which decreasing trend in the total auroral power was mainly caused by dimming of the main oval, possibly due to an expansion of the magnetosphere under decreasing solar wind dynamic pressure. That is, the main oval is assumed to be the main contributor to the auroral power enhancement in response to the elevated solar wind dynamic pressure.…”

Section: Discussionmentioning

confidence: 99%

Characteristics of solar wind control on Jovian UV auroral activity deciphered by long‐term Hisaki EXCEED observations: Evidence of preconditioning of the magnetosphere?

Kita

Kimura

Tao

et al. 2016

Geophysical Research Letters

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While the Jovian magnetosphere is known to have the internal source for its activity, it is reported to be under the influence of the solar wind as well. Here we report the statistical relationship between the total power of the Jovian ultraviolet aurora and the solar wind properties found from long‐term monitoring by the spectrometer EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) on board the Hisaki satellite. Superposed epoch analysis indicates that auroral total power increases when an enhanced solar wind dynamic pressure hits the magnetosphere. Furthermore, the auroral total power shows a positive correlation with the duration of a quiescent interval of the solar wind that is present before a rise in the dynamic pressure, more than with the amplitude of dynamic pressure increase. These statistical characteristics define the next step to unveil the physical mechanism of the solar wind control on the Jovian magnetospheric dynamics.

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Weakening of Jupiter's main auroral emission during January 2014

Cited by 37 publications

References 55 publications

Transient brightening of Jupiter's aurora observed by the Hisaki satellite and Hubble Space Telescope during approach phase of the Juno spacecraft

Transient brightening of Jupiter's aurora observed by the Hisaki satellite and Hubble Space Telescope during approach phase of the Juno spacecraft

Volcanic activity on Io and its influence on the dynamics of the Jovian magnetosphere observed by EXCEED/Hisaki in 2015

Characteristics of solar wind control on Jovian UV auroral activity deciphered by long‐term Hisaki EXCEED observations: Evidence of preconditioning of the magnetosphere?

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