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Identification of Extreme Ultraviolet Emission Lines of the Io Plasma Torus Observed by Hisaki/EXCEED
Author(s) -
Hikida R.,
Yoshioka K.,
Murakami G.,
Kimura T.,
Tsuchiya F.,
Yamazaki A.,
Yoshikawa I.,
Iwagami N.
Publication year - 2018
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1029/2018je005629
Subject(s) - ultraviolet , extreme ultraviolet , wavelength , emission spectrum , excited state , plasma , torus , atomic physics , spectral line , radiative transfer , jupiter (rocket family) , physics , optics , astronomy , laser , geometry , mathematics , space shuttle , quantum mechanics
The sulfur and oxygen ions in the Io plasma torus (IPT), which is located at a distance of ~6 R J from Jupiter, emit light in various wavelength regions. In particular, radiative cooling in the ultraviolet wavelength range plays an important role in the energy balance of the Io torus, and it is important to explore the detailed spectral structure in the ultraviolet region. The ultraviolet spectrum of the IPT in the wavelength range 52.0–148.0 nm with a resolution of 0.3–0.4 nm was obtained by Extreme Ultraviolet Spectroscope for Exospheric Dynamics on the Hisaki satellite. Owing to its instrument performance and long integration time, 10 emission lines from the IPT were detected for the first time. By summarizing previous observations and using the results obtained by Extreme Ultraviolet Spectroscope for Exospheric Dynamics, we updated the term diagrams for S II, S III, and S IV emissions from the IPT. Four excited levels in the IPT were detected for the first time. Detection of the emission lines may improve the estimation accuracy of the fraction of hot electron density using the atomic data.