Details

Autor(en) / Beteiligte

• Tao, Chihiro
• Kimura, Tomoki
• Badman, Sarah V.
• André, Nicolas
• Tsuchiya, Fuminori
• Murakami, Go
• Yoshioka, Kazuo
• Yoshikawa, Ichiro
• Yamazaki, Atsushi
• Fujimoto, Masaki

Titel

Variation of Jupiter's aurora observed by Hisaki/EXCEED: 2. Estimations of auroral parameters and magnetospheric dynamics

Ist Teil von

• Journal of geophysical research. Space physics, 2016-05, Vol.121 (5), p.4055-4071

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2016

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Jupiter's auroral parameters are estimated from observations by a spectrometer EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) on board Japanese Aerospace Exploration Agency's Earth‐orbiting planetary space telescope Hisaki. EXCEED provides continuous auroral spectra covering the wavelength range over 80–148 nm from the whole northern polar region. The auroral electron energy is estimated using a hydrocarbon color ratio adopted for the wavelength range of EXCEED, and the emission power in the long wavelength range 138.5–144.8 nm is used as an indicator of total emitted power before hydrocarbon absorption and auroral electron energy flux. The quasi‐continuous observations by Hisaki provide the auroral electron parameters and their relation under different auroral activity levels. Short‐ (within < one planetary rotation) and long‐term (> one planetary rotation) enhancements of auroral power accompany increases of the electron number flux rather than the electron energy variations. The relationships between the auroral electron energy (~70–400 keV) and flux (1026–1027/s, 0.08–0.9 μA/m2) estimated from the observations over a 40 day interval are in agreement with field‐aligned acceleration theory when incorporating probable magnetospheric parameters. Applying the electron acceleration theory to each observation point, we explore the magnetospheric source plasma variation during these power‐enhanced events. Possible scenarios to explain the derived variations are (i) an adiabatic variation of the magnetospheric plasma under a magnetospheric compression and/or plasma injection, and (ii) a change of the dominant auroral component from the main emission (main aurora) to the emission at the open‐closed boundary. Key Points Auroral electron energy and flux are estimated from Hisaki/EXCEED observations Aurora power enhancements are mainly due to increased electron flux, not energy Possible explanations for variations of estimated parameters are discussed