Volume 589, May 2016
|Number of page(s)||5|
|Section||Planets and planetary systems|
|Published online||14 April 2016|
Detection of H3+ auroral emission in Jupiter’s 5-micron window
1 Atmospheric, Oceanic & Planetary Physics, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK
2 Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
Received: 21 January 2016
Accepted: 11 March 2016
We use high-resolution ground-based observations from the VLT CRIRES instrument in November 2012 to identify sixteen previously undetected H3+ emission lines from Jupiter’s ionosphere. These emission lines are located in Jupiter’s 5-micron window (4.5−5.2 μm), an optically-thin region of the planet’s spectrum where the radiation mostly originates from the deep troposphere. The H3+ emission lines are so strong that they are visible even against this bright background. We measure the Doppler broadening of the H3+ emission lines in order to evaluate the kinetic temperature of the molecules, and we obtain a value of 1390 ± 160 K. We also measure the relative intensities of lines in the ν2 fundamental in order to calculate the rotational temperature, obtaining a value of 960 ± 40 K. Finally, we use the detection of an emission line from the 2ν2(2)-ν2 overtone to measure a vibrational temperature of 925 ± 25 K. We use these three independent temperature estimates to discuss the thermodynamic equilibrium of Jupiter’s ionosphere.
Key words: planets and satellites: gaseous planets / planets and satellites: aurorae / planets and satellites: atmospheres
© ESO, 2016
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