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 H+ 3 ν2 Q(1, 0−) line at 3.953 μm using the IRTF, the line-of-sight velocities of the H+ 3 ions were derived in the planetary reference frame and found to be 0.091 ± 0.25 km s−1, 0.0082 ± 0.30 km s−1 and 0.31 ± 0.51 km s−1 in 1998, 2007 and 2013 respectively. These zero velocities represent corotation at the midto-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 H+ 3 emission layer (∼550 km above the 1 bar level), and we assert that the H+ 3 ions in Jupiter’s mid-to-low latitude are rigidly corotating.