P41B-2073
Long-term Observations of Jovian Mid-Infrared Aurora, Hydrocarbon Abundances, and Temperature: Ground-based and Space-based Comparison and Preparation for Juno
Thursday, 17 December 2015
Poster Hall (Moscone South)
Theodor Kostiuk1, Tilak Hewagama1,2, Timothy A Livengood1,3, Kelly Elizabeth Fast4, Gordon L Bjoraker5, Ronald C. Carlson6 and Frank Schmuelling7, (1)NASA Goddard SFC, Greenbelt, MD, United States, (2)University of Maryland College Park, Greenbelt, MD, United States, (3)University of Maryland College Park, College Park, MD, United States, (4)NASA Headquarters, Washington, DC, United States, (5)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (6)Catholic University of America, Washington, DC, United States, (7)German Aerospace Center DLR Bonn, Bonn, Germany
Abstract:
With Juno’s approach to Jupiter in 2016 nearing, we report on long term measurements of Jupiter’s thermal infrared aurora covering spectral and altitude regions that will complement Juno observational capabilities. Previously acquired spectral data from ground-based observatories as well as by Voyager IRIS and Cassini CIRS during Jupiter flybys will be investigated using current methods and capabilities. The thermal (mid-) IR aurora from Jupiter’s polar regions, hydrocarbon abundances, and thermal structure retrieved from the ground and from space-based investigations will be compared and used to illustrate the different capabilities and complementarity of the measurement platforms. We report on the reexamination and re-analysis of hydrocarbon emission spectra from Jupiter obtained using ground-based ultra-high spectral resolution infrared heterodyne spectroscopy (IRHS) and Fourier transform spectroscopy (FTS) from Cassini CIRS during its flyby of Jupiter in 2000-2001 and Voyager IRIS data obtained during flybys in 1979. Measurements with IRHS have been made over 30 years, primarily of ethane near 12 micrometer wavelength. These measurements yield fully resolved individual spectral lines whose shape provides unique information on variability of temperature and abundance. CIRS and IRIS data at coarser spectral resolution provide extended spatial distributions covering a broad spectral region, including abundances and auroral response of hydrocarbon constituents in the 8–13 micrometer spectral region (ethane, methane, ethylene, and acetylene). Analysis shows detailed spatial variability 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. From these analyses, the expectation is that the thermal IR auroral emission may be low during the Juno tour at Jupiter Results will be useful for the Juno mission, since it does not have instrumentation in this spectral region and this work provides complementary information and diagnostics to study Jupiter in a spectral region and altitude range not directly probed by Juno.
