期刊
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
卷 121, 期 5, 页码 4055-4071出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/2015JA021272
关键词
Jupiter; aurora; Hisaki; EXCEED; Hubble Space Telescope
资金
- ISSI International Team on Coordinated Numerical Modeling of the Global Jovian and Saturnian Systems [ID324]
- JSPS KAKENHI [15K17769]
- Royal Astronomical Society Research Fellowship
- Grants-in-Aid for Scientific Research [15K17769, 26400476] Funding Source: KAKEN
- Science and Technology Facilities Council [ST/M005534/1] Funding Source: researchfish
- STFC [ST/M005534/1] Funding Source: UKRI
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 80-148nm 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 138.5-144.8nm 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 (70-400keV) and flux (10(26)-10(27)/s, 0.08-0.9A/m(2)) estimated from the observations over a 40day 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.
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