Jupiter’s auroral-related stratospheric heating and chemistry II: Analysis of IRTF-TEXES spectra measured in December 2014

Abstract

We present a retrieval analysis of TEXES (Texas Echelon Cross Echelle Spectrograph (Lacy et al., 2002)) spectra of Jupiter's high latitudes obtained on NASA's Infrared Telescope Facility on December 10-11th 2014. The vertical temperature profile and vertical profiles of C 2 H 2 , C 2 H 4 and C 2 H 6 were retrieved at both high-northern and high-southern latitudes and results were compared in 'quiescent' regions and regions known to be affected by Jupiter's aurora in order to highlight how auroral processes modify the thermal structure and hydrocarbon chemistry of the stratosphere. In qualitative agreement with Sinclair et al. (2017a), we find temperatures in auroral regions to be elevated with respect to quiescent regions at two discrete pressures levels at approximately 1 mbar and 0.01 mbar. For example, in comparing retrieved temperatures at 70• N, 60• W (a representative quiescent region) and 70• N, 180• W (centred on the northern auroral oval), temperatures increase by 19.0 ± 4.2 K at 0.98 mbar, 20.8 ± 3.9 K at 0.01 mbar but only by 8.3 ± 4.9 K at the intermediate level of 0.1 mbar. We conclude that elevated temperatures at 0.01 mbar result from heating by joule resistance of the atmosphere and the energy imparted by electron and ion precipitation. However, temperatures at 1 mbar are considered to result either from heating by shortwave radiation of aurorally-produced haze particulates or precipitation of higher energy population of charged particles. Our former conclusion would be consistent with results of auroral-chemistry models, that predict the highest number densities of aurorally-produced haze particles at this pressure level (Wong et al., 2000(Wong et al., , 2003. C 2 H 2 and C 2 H 4 exhibit enrichments but C 2 H 6 remains constant within uncertainty when comparing retrieved concentrations in the northern auroral region with quiescent longitudes in the same latitude band. At 1 mbar, C 2 H 2 increases from 278.4 ± 40.3 ppbv at 70• N, 60• W to 564.4 ± 72.0 ppbv at 70• N, 180• W and at 0.01 mbar, over the same longitude range at 70• N, C 2 H 4 increases from 0.669 ± 0.129 ppmv to 6.509 ± 0.811 ppmv. However, we note that non-LTE (local thermodynamic equilibrium) emission may affect the cores of the strongest C 2 H 2 and C 2 H 4 lines on the northern auroral region, which may be a possible source of error in our derived concentrations. We retrieved concentrations of C 2 H 6 at 1 mbar of 9.03 ± 0.98 ppmv at 70• N, 60• W and 7.66 ± 0.70 ppmv at 70• N, 180• W. Thus, C 2 H 6 's concentration appears constant (within uncertainty) as a function of longitude at 70• N.

A brightening of Jupiter’s auroral 7.8-μm CH4 emission during a solar-wind compression

“…This feature was not present less than 24 hours later ( Figure 2b) and we have ruled out variable atmospheric seeing conditions between these two nights as the source of this intermittent morphology (see Supplementary Figure 2). A similar morphology of the ultraviolet auroral emission, described as the 'duskside active region', has also been observed during periods of enhanced solar-wind pressures and has been attributed to duskside/nightside reconnection associated with the Vasyliunas or Dungey cycles or velocity shears caused by changing flows on the nightside magnetospheric flank 4,5,10 . Indeed, ionosphere-magnetosphere mapping calculations map 73 • N, 155 • W (an example location covered by the duskside feature) to ∼100R J at a local time of 19.0 hr.…”

A hexagon in Saturn’s northern stratosphere surrounding the emerging summertime polar vortex

“…On Jupiter, stratospheric temperatures are elevated within the auroral oval both by Joule heating and particulate absorption 57 . Future work could address whether the processes heating the atmosphere at nanobar pressures could also influence the temperatures of Saturn’s polar stratosphere at millibar levels but would require a close coupling of thermospheric and stratospheric circulation, chemistry and radiative models that include the influences of aerosols.…”

Jovian Auroral Ion Precipitation: X‐Ray Production From Oxygen and Sulfur Precipitation

“…The same atmosphere is used here, only we have extended the depth from 200 to 88 km, where 0 km is set to where the pressure is equal to 1 bar (Figure ). The atmosphere below 200 km has been generated using temperature‐pressure profiles retrieved from National Aeronautics and Space Administration's Infrared Telescope Facility and the Texas Echelon Cross Echelle Spectrograph Instrument (Sinclair et al, ). Using the temperature and pressure, the ideal gas law is then solved to obtain the total number density.…”

“…Atmospheric density profiles of H , He, CH , and H based on data shown in Maurellis and Cravens () and Sinclair et al (). Also shown is the neutral temperature profile as a function of altitude and pressure.…”

“…We follow up on the promise made in Houston et al (2018) to include energetic sulfur precipitation and oxygen improvements, with proton precipitation being left to a future and very necessary publication. Maurellis and Cravens (2001) and Sinclair et al (2018). Also shown is the neutral temperature profile as a function of altitude and pressure.…”