Jovian Mid-Infrared Aurora: Retrospective Analysis of Variability and Cassini Flyby Measurements in Preparation for Juno
Abstract
With the approaching arrival of the Juno mission at Jupiter it is important to look at the current knowledge of Jovian phenomena that can or cannot be further studied from orbital spacecraft. It is also important to retrospectively investigate previously acquired data using current improved methods and capabilities. The thermal (mid-) infrared aurora from Jupiter’s polar regions has been studied extensively from ground-based observatories as well as by Voyager IRIS and Cassini CIRS during Jupiter flybys. We report on a reexamination and re-analysis of hydrocarbon emission spectra from the polar regions of Jupiter obtained using ground based infrared heterodyne spectroscopy (IRHS) and Cassini CIRS Fourier transform spectroscopy (FTS) during the flyby of Jupiter in 2000-2001. Measurements with IRHS have been made over 30 years, primarily of ethane near 12 micrometer wavelength. IRHS provides fully resolved individual spectral lines whose shape yields unique information on variability of temperature and abundance. CIRS data, at lower spectral resolution, explores extended spatial distributions and covers a broad spectral region that includes auroral response of ethane as well as several other hydrocarbons in the 8-13 micrometer wavelength region (methane, ethylene, and acetylene). These spectra are radiometrically calibrated and can serve as a sensitive thermometer of the Jovian atmosphere. Recently improved analysis techniques show detailed spatial enhancements of the primary hydrocarbons in northern latitudes. Temporal changes of the ethane line emission over three solar cycles and comparison of retrievals from ethane data taken contemporaneously during the Cassini flyby by both techniques will be compared and results discussed. Juno does not have instrumentation in this spectral region and this work provides complementary information and diagnostics for studying Jovian aurora and magnetosphere in a spectral region and altitude range not directly probed by Juno.
- Publication:
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AAS/Division for Planetary Sciences Meeting Abstracts #46
- Pub Date:
- November 2014
- Bibcode:
- 2014DPS....4651106K