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

We use high-resolution ground-based observations from the VLT CRIRES instrument in November 2012 to identify sixteen previously undetected H-3(+) 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 H-3(+) emission lines are so strong that they are visible even against this bright background. We measure the Doppler broadening of the H-3(+) 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 nu(2) 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 2 nu(2)(2)-nu(2) 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.