Measurements of the rotation rate of the jovian mid-to-low latitude ionosphere

Previous studies of Jupiter's upper atmosphere often assume that the mid-to-low latitude ionosphere is corotating, but a model describing an observed asymmetry in hydrogen Lyman-α emission (∼1000 km above the 1 bar level) disagrees with this assumption. From measurements of the Doppler shifted H3+ν2Q(1,0−) line at 3.953 μm using the IRTF, the line-of-sight velocities of the H3+ ions were derived in the planetary reference frame and found to be 0.091 ± 0.250.33em0exkm0.33em0exs−1, 0.0082 ± 0.300.33em0exkm0.33em0exs−1 and 0.31 ± 0.510.33em0exkm0.33em0exs−10.33em0exin 1998, 2007 and 2013 respectively. These zero velocities represent corotation at the mid-to-low latitude region of Jupiter's ionosphere. There is no evidence of flows associated with the hydrogen Lyman-α emission asymmetries detected in the peak H3+ emission layer (∼550 km above the 1 bar level), and we assert that the H3+ ions in Jupiter's mid-to-low latitude are rigidly corotating.