The time variation of atomic oxygen emission around Io during a volcanic event observed with Hisaki/EXCEED

Koga, Ryoichi; Tsuchiya, F.; Kagitani, Masato; Sakanoi, Takeshi; Yoneda, Mizuki; Yoshioka, Kazuo; Kimura, Tomoki; Murakami, Go; Yamazaki, Atsushi; Yoshikawa, Ichiro; Smith, H. T.

doi:10.1016/j.icarus.2017.07.024

Cited by 25 publications

(43 citation statements)

References 38 publications

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“…This suggests an increase in the neutral particle density in the plasma torus. However, there is no evidence for an increased volcanic activity on Io: both the sodium nebula and the oxygen neutral cloud emissions were almost stable during this period (Koga et al, ; Yoneda et al, ) and the ion brightnesses and the line ratios do not show significant time variations (Figures a–c).…”

Section: Resultsmentioning

confidence: 95%

“…In this paper, the data set of the Io plasma torus emissions obtained by the extreme ultraviolet spectrograph EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics), onboard the Hisaki satellite, is used (section ). Hisaki has conducted long‐term monitoring of the Io plasma torus since December 2013 and captured responses of the Jovian magnetosphere to the increase in neutrals from Io in early 2015 (Kimura et al, ; Koga et al, ; Tao et al, ; Tsuchiya et al, ; Yoshikawa et al, ; Yoshioka et al, ). The purpose of this study is to survey azimuthal variations in the torus using the large Hisaki data set obtained from December 2013 to August 2016.…”

Section: Introductionmentioning

confidence: 99%

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Azimuthal Variation in the Io Plasma Torus Observed by the Hisaki Satellite From 2013 to 2016

et al. 2019

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In the Jovian magnetosphere, sulfur and oxygen ions supplied by the satellite Io are distributed in the so‐called Io plasma torus. The plasma torus is located in the inner area of the magnetosphere and the plasma in the torus corotates with the planet. The density and the temperature of the plasma in the torus have significant azimuthal variations. In this study, data from three‐year observations obtained by the Hisaki satellite, from December 2013 to August 2016, were used to investigate statistically the azimuthal variations and to find out whether the variations were influenced by the increase in neutral particles from Io. The azimuthal variation was obtained from a time series of sulfur ion line ratios, which were sensitive to the electron temperature and the sulfur ion mixing ratio S3+/S+. The major characteristics of the azimuthal variation in the plasma parameters were consistent with the dual hot electron model, proposed to explain previous observations. On the other hand, the Hisaki data showed that the peak System III longitude in the S3+/S+ ratio was located not only around 0°–90°, as in previous observations, but also around 180°–270°. The rotation period, the System IV periodicity, was sometimes close to the Jovian rotation period. Persistent input of energy to electrons in a limited longitude range of the torus is associated with the shortening of the System IV period.

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Section: Resultsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Azimuthal Variation in the Io Plasma Torus Observed by the Hisaki Satellite From 2013 to 2016

et al. 2019

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“…Yoshikawa et al (2017) indicated an enhancement in the EUV line emissions of sulfur and oxygen ions in multiple charge states. Based on the difference in the temporal evolution between each ion species and charge state, they concluded that neutral gases erupted from Io's volcanoes on DOY 20-125, as actually detected by Hisaki during this time (Koga et al, 2017), underwent charge exchange and electron impact, and were finally picked up as the ions in the torus. The mass loading rate in the present study shows that picked-up ions provide plasma mass to the magnetosphere during the volcanic event at a relatively higher rate (0.5 t/s) than usual (0.3 t/s).…”

Section: Response Of Transient Aurora To Mass Loading Ratementioning

confidence: 94%

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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“…Section 5 summarizes and concludes the paper. Koga et al (2017). The ground-based observation of sodium emissions reported by Yoneda et al (2015) is shown in Figure 1a.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of the Jovian Magnetospheric Plasma Circulation Caused by the Change in Plasma Supply From the Satellite Io

et al. 2018

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The innermost Galilean satellite, Io, supplies a large amount of volcanic gasses to the Jovian magnetosphere. The fast rotation of Jupiter and the outward transport of ionized gasses are responsible for forming a huge and rotationally dominant magnetosphere. The plasma supply from the satellite has a key role in the characterization of the Jovian magnetosphere. In fact, significant variations of the plasma population in the inner magnetosphere caused by the volcanic eruptions in Io were found in early 2015, using a continuous data set of the Io plasma torus obtained from an extreme ultraviolet spectroscope onboard the Hisaki satellite. The time evolution of the Io plasma torus radial distribution showed that the outward transport of plasma through 8 RJ from Jupiter was enhanced for approximately 2 months (from the end of January to the beginning of April 2015). Intense short‐lived auroral brightenings––which represent transient energy releases in the outer part of the magnetosphere—occurred frequently during this period. The short‐lived auroral brightenings accompanied well‐defined sporadic enhancements of the ion brightness in the plasma torus, indicating a rapid inward transport of energy from the outer part of the magnetosphere and the resultant enhancement of hot electron population in the inner magnetosphere. This evidently shows that the change in a plasma source in the inner magnetosphere affects a large‐scale radial circulation of mass and energy in a rotationally dominant magnetosphere.

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The time variation of atomic oxygen emission around Io during a volcanic event observed with Hisaki/EXCEED

Cited by 25 publications

References 38 publications

Azimuthal Variation in the Io Plasma Torus Observed by the Hisaki Satellite From 2013 to 2016

Azimuthal Variation in the Io Plasma Torus Observed by the Hisaki Satellite From 2013 to 2016

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

Enhancement of the Jovian Magnetospheric Plasma Circulation Caused by the Change in Plasma Supply From the Satellite Io

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