Hot electron component in the Io plasma torus confirmed through EUV spectral analysis

Yoshioka, Kazuo; Yoshikawa, Ichiro; Tsuchiya, F.; Kagitani, Masato; Murakami, Go

doi:10.1029/2011ja016583

Cited by 16 publications

(23 citation statements)

References 41 publications

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“…[], while a value of 4.7 Å was used by Yoshioka et al . []. We found 3 Å to be too narrow and that a FWHM of 4.47 Å produced the best fit to the spectrum.…”

Section: Resultsmentioning

confidence: 68%

Io plasma torus ion composition: Voyager, Galileo, and Cassini

2017

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The Io torus produces ultraviolet emissions diagnostic of plasma conditions. We revisit data sets obtained by the Voyager 1, Galileo, and Cassini missions at Jupiter. With the latest version (8.0) of the CHIANTI atomic database we analyze UV spectra to determine ion composition. We compare ion composition obtained from observations from these three missions with a theoretical model of the physical chemistry of the torus by Delamere et al. (2005). We find ion abundances from the Voyager data similar to the Cassini epoch, consistent with the dissociation and ionization of SO2, but with a slightly higher average ionization state for sulfur, consistent with the higher electron temperature measured by Voyager. This reanalysis of the Voyager data produces a much lower oxygen:sulfur ratio than earlier analysis by Shemansky (1988), which was also reported by Bagenal (1994). We derive fractional ion compositions in the center of the torus to be S+/Ne ~ 5%, S++/Ne ~ 20%, S+++/Ne ~ 5%, O+/Ne ~ 20%, O++/Ne ~ 3%, and Σ(On+)/Σ(Sn+) ~ 0.8, leaving about 10–15% of the charge as protons. The radial profile of ion composition indicates a slightly higher average ionization state, a modest loss of sulfur relative to oxygen, and Σ(On+)/Σ(Sn+) ~ 1.2 at about 8 RJ, beyond which the composition is basically frozen in. The Galileo observations of UV emissions from the torus suggest that the composition in June 1996 may have comprised a lower abundance of oxygen than usual, consistent with observations made at the same time by the EUVE satellite.

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“…[], while a value of 4.7 Å was used by Yoshioka et al . []. We found 3 Å to be too narrow and that a FWHM of 4.47 Å produced the best fit to the spectrum.…”

Section: Resultsmentioning

confidence: 68%

Io plasma torus ion composition: Voyager, Galileo, and Cassini

2017

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“…Figure d shows the 40 min and 20 h running spatially averaged IPT radiations (at jovicentric distance between 7.8 R J and 2.2 R J at both ansas) in the spectral range of 65–78 nm, where strong emission lines of S IV (65.7 nm), S III (68.0 nm), and S II (76.5 nm) exist. These lines are indicators for hot electron density [ Yoshioka et al ., ]. Due to the relatively large statistics error and existence of inherent periodic brightness variations of the IPT [ Tsuchiya et al ., ], the enhancements of the IPT radiation do not seem clear in 40 min exposures (red dots) but are visible in the 20 h averaged curve (black).…”

Section: Resultsmentioning

confidence: 99%

Properties of hot electrons in the Jovian inner magnetosphere deduced from extended observations of the Io Plasma Torus

Yoshikawa

Yoshioka

Murakami

et al. 2016

Geophysical Research Letters

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One of the focal points of interest in Jovian magnetospheric physics is the transport of energy and particles into the inner region. While an explosive energy release event in the midmagnetosphere is manifested as an aurora transient, its connection to the inner part has not been investigated due to sparsity of observations. Here we take the advantage of long‐term and quasi‐continuous simultaneous monitoring of the polar aurora and the Io Plasma Torus (IPT) located in the inner magnetosphere by Extreme Ultraviolet Spectroscope for Exospheric Dynamics/Hisaki. Studies on temporal characteristics over hours enable us to see slow (~10 h) coupling between the middle and inner magnetosphere as well as to quantify the temperature of hot electrons in the IPT. We derive parameters that characterize the strong particle acceleration process.

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“…Model spectra were calculated with the atomic database CHIANTI version 7.1.4 [ Dere et al ., ; Landi et al ., ] with a similar method described by Yoshioka et al [, ]. The model spectra take into account four ion species (S + , S 2+ , S 3+ , and O + ) and two electron temperatures (thermal and hot components).…”

Section: Resultsmentioning

confidence: 99%

Local electron heating in the Io plasma torus associated with Io from HISAKI satellite observation

et al. 2015

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Io‐correlated brightness change in the Io plasma torus (IPT) was discovered by the Voyager spacecraft, showing evidence of local electron heating around Io. However, its detailed properties and the cause of electron heating are still open issues. The extreme ultraviolet spectrograph on board the HISAKI satellite continuously observed the IPT from the end of December 2013 to the middle of January 2014. The variation in the IPT brightness showed that clear periodicity associated with Io's orbital period (42 h) and that the bright region was located downstream of Io. The amplitude of the periodic variation was larger at short wavelengths than at long wavelengths. From spectral analyses, we found that Io‐correlated brightening is caused by the increase in the hot electron population in the region downstream of Io. We also found that the brightness depends on the system III longitude and found primary and secondary peaks in the longitude ranges of 100–130° and 250–340°, respectively. Io's orbit crosses the center of the IPT around these longitudes. This longitude dependence suggests that the electron heating process is related to the plasma density around Io. The total radiated power from the IPT in January 2014 was estimated to be 1.4 TW in the wavelength range from 60 to 145 nm. The Io‐correlated component produced 10% of this total radiated power. The interaction between Io and the IPT continuously produces a large amount of energy around Io, and 140 GW of that energy is immediately converted to hot electron production in the IPT.

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Hot electron component in the Io plasma torus confirmed through EUV spectral analysis

Cited by 16 publications

References 41 publications

Io plasma torus ion composition: Voyager, Galileo, and Cassini

Io plasma torus ion composition: Voyager, Galileo, and Cassini

Properties of hot electrons in the Jovian inner magnetosphere deduced from extended observations of the Io Plasma Torus

Local electron heating in the Io plasma torus associated with Io from HISAKI satellite observation

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