Abstract
We use high-resolution ground-based observations from the VLT CRIRES instrument in December 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 {\mu}m), 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$\pm$160 K. We also measure the relative intensities of lines in the {\nu}2 fundamental in order to calculate the rotational temperature, obtaining a value of 960$\pm$40 K. Finally, we use the detection of an emission line from the 2{\nu}2(2)-{\nu}2 overtone to measure a vibrational temperature of 925$\pm$25 K. We use these three independent temperature estimates to discuss the thermodynamic equilibrium of Jupiter's ionosphere.
Highlights
Observations of H+3 lines are a valuable tool in studying Jupiter’s upper atmosphere
The first spectroscopic detection of H+3 emission from Jupiter’s ionosphere was made by Drossart et al (1989) in the 2ν2(l = 2) overtone band at 2 μm in the K-band. This was almost immediately followed by detections of the ν2 fundamental at 4 μm in the L-band (e.g. Oka & Geballe 1990), and more recently by detection of the 2ν2(0)-ν2 (4 μm) and 3ν2(3)ν2 (2 μm) overtones (Stallard et al 2002; Raynaud et al 2004)
We use high-resolution ground-based observations to identify previously undetected H+3 emission lines in the 4.5−5.2 μm range, which belong to the ν2 fundamental and to the 2ν2(2)-ν2 overtone
Summary
Observations of H+3 lines are a valuable tool in studying Jupiter’s upper atmosphere. Studying the H+3 emission lines can provide us with several different types of temperature measurements for Jupiter’s ionosphere. We use high-resolution ground-based observations to identify previously undetected H+3 emission lines in the 4.5−5.2 μm range, which belong to the ν2 fundamental and to the 2ν2(2)-ν2 overtone. These emission lines are located in Jupiter’s 5-micron atmospheric window; at these wavelengths, Jupiter’s atmosphere is optically thin, allowing us to view bright radiation from deep in the planet’s troposphere. We compare the fundamental and overtone lines to evaluate T vib This is first time that all three temperatures have been measured simultaneously
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