Detection of H3+ auroral emission in Jupiter's 5-micron window

TL;DR

This study reports the detection of sixteen H3+ emission lines in Jupiter's 5-micron window using high-resolution ground-based observations, providing insights into the ionosphere's temperature and thermodynamic state.

Contribution

First detection of multiple H3+ emission lines in Jupiter's 5-micron window, enabling detailed temperature analysis of the planet's ionosphere.

Findings

Measured kinetic temperature of 1390±160 K

Determined rotational temperature of 960±40 K

Estimated vibrational temperature of 925±25 K

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.