Dynamics of Jovian Infrared Auroral Ionosphere and Thermosphere

This thesis presents a spectroscopic analysis of near-infrared spectra acquired from simultaneously observed H+3 and H2 emission lines from Jupiter’s northern aurora using Keck-NIRSPEC on 02 June 2017. From the high spatial resolution spectra, physical quantities were derived to investigate dynamics, heating, and energetics within Jupiter’s upper atmosphere, as well as the coupling between the ionosphere, the thermosphere, and the surrounding magnetosphere.

Line-of-sight velocities were measured from the Doppler shift of the H+3 overtone, H+3 hot overtone, and H2 quadrupole emission lines. The ion velocities vary from subcorotation to supercorotation relative to Jupiter’s rotation rate at different morphological regions, highly comparable to the results previously reported. Measurements of the neutral winds revealed a symmetric anticyclonic vortex that significantly subcorotates within the auroral region, resolving Jupiter’s thermospheric dynamics for the first time.

Considering that the H+3 and H2 emissions of interest have been shown to peak at the same altitude, the relative motions between the ions and the neutrals were determined to produce the effective ion drift, showing the ion winds in the reference frame of the neutral flows. The effective ion drift measured directly from Jupiter’s upper ionosphere is dominated by two sunward blue-shifted jets associated with the dawn and dusk main auroral regions, with each jet offset to the dusk side of the main auroral emission. Along with recent discoveries during Juno flybys, such asymmetric jets may provide an alternative explanation to the driving mechanism of the main aurora on Jupiter.

The spatial distribution of emission intensity, rotational temperature, and column density was also studied using the same data. Analyzing the correlations within these parameters and between the effective ion drift suggested a complex heating mechanism of the Jovian auroral thermosphere. It is speculated that the heating source may originate from an altitude above the stratosphere but below the peak altitude of H+3 overtone and H2 quadrupole emissions.