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

Kita, Hidetoshi; Kimura, Tomoki; Tao, Chihiro; Tsuchiya, F.; Misawa, Hiroaki; Sakanoi, Takeshi; Kasaba, Yasumasa; Murakami, Go; Yoshioka, Kazuo; Yamazaki, Atsushi; Yoshikawa, Ichiro; Fujimoto, M.

doi:10.1002/2016gl069481

Cited by 34 publications

(45 citation statements)

References 36 publications

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“…Superposed epoch analysis might be effective. Kita et al (2016) reported positive correlation between the auroral power and duration of the quiescent interval of SW during the period of DOY −10 to DOY 50. After DOY 50, two cases on DOY 66 and 87 are predicted with quiescent intervals longer than 5 days.…”

Section: +mentioning

confidence: 96%

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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Section: +mentioning

confidence: 96%

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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“…Uncertainty in the arrival time of the solar wind shock structures, the Corotating Interaction Region and Coronal Mass Ejections, at Jupiter is dependent on the Earth‐Sun‐Jupiter angle, which was 82°–180° for the present analysis period. The arrival time uncertainty is estimated to be approximately a few days or more, as discussed in Kimura et al (, ), Kita et al (), and Tao et al (, ).…”

Section: Data Setmentioning

confidence: 97%

Response of Jupiter's Aurora to Plasma Mass Loading Rate Monitored by the Hisaki Satellite During Volcanic Eruptions at Io

et al. 2018

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The production and transport of plasma mass are essential processes in the dynamics of planetary magnetospheres. At Jupiter, it is hypothesized that Io's volcanic plasma carried out of the plasma torus is transported radially outward in the rotating magnetosphere and is recurrently ejected as plasmoid via tail reconnection. The plasmoid ejection is likely associated with particle energization, radial plasma flow, and transient auroral emissions. However, it has not been demonstrated that plasmoid ejection is sensitive to mass loading because of the lack of simultaneous observations of both processes. We report the response of plasmoid ejection to mass loading during large volcanic eruptions at Io in 2015. Response of the transient aurora to the mass loading rate was investigated based on a combination of Hisaki satellite monitoring and a newly developed analytic model. We found that the transient aurora frequently recurred at a 2–6 day period in response to a mass loading increase from 0.3 to 0.5 t/s. In general, the recurrence of the transient aurora was not significantly correlated with the solar wind, although there was an exceptional event with a maximum emission power of ~10 TW after the solar wind shock arrival. The recurrence of plasmoid ejection requires the precondition that an amount comparable to the total mass of magnetosphere, ~1.5 Mt, is accumulated in the magnetosphere. A plasmoid mass of more than 0.1 Mt is necessary in case that the plasmoid ejection is the only process for mass release.

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“…Uncertainties in propagated parameters for both models increase with Earth‐Sun‐Jupiter angle. Here this angle is between 17° (on 14 April) and 24° (on 24 April), so that solar wind extrapolations from this period should have a relatively high accuracy for both models (i.e., better than 20 h for shock arrival predictions and uncertainties <38% in maximum pressure values) [ Tao et al , ; Kita et al , ].…”

Section: Datamentioning

confidence: 99%

Variability of Jupiter's IR H₃⁺ aurorae during Juno approach

Moore

O’Donoghue

Melin

et al. 2017

Geophysical Research Letters

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We present ground‐based observations of Jupiter's H3+ aurorae over four nights in April 2016 while the Juno spacecraft was monitoring the upstream interplanetary magnetic field. High‐precision maps of auroral H3+ densities, temperatures, and radiances reveal significant variabilities in those parameters, with regions of enhanced density and emission accompanied by reduced temperature. Juno magnetometer data, combined with solar wind propagation models, suggest that a shock may have impacted Jupiter in the days preceding the observation interval but that the solar wind was quiescent thereafter. Auroral H3+ temperatures reveal a downward temporal trend, consistent with a slowly cooling upper atmosphere, such as might follow a period of shock recovery. The brightest H3+ emissions are from the end of the period, 23 April. A lack of definitive signatures in the upstream interplanetary magnetic field lends supporting evidence to the possibility that this brightening event may have been driven by internal magnetospheric processes.

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

Cited by 34 publications

References 36 publications

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

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

Response of Jupiter's Aurora to Plasma Mass Loading Rate Monitored by the Hisaki Satellite During Volcanic Eruptions at Io

Variability of Jupiter's IR H₃⁺ aurorae during Juno approach

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

Cited by 34 publications

References 36 publications

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

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

Response of Jupiter's Aurora to Plasma Mass Loading Rate Monitored by the Hisaki Satellite During Volcanic Eruptions at Io

Variability of Jupiter's IR H3+ aurorae during Juno approach

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Variability of Jupiter's IR H₃⁺ aurorae during Juno approach