Mapping H-3(+) Temperatures in Jupiter's Northern Auroral Ionosphere Using VLT-CRIRES

摘要

We present a detailed study of the H-3(+) auroral emissions at Jupiter, using data taken on 31 December 2012 with the long-slit Echelle spectrometer CRIRES (ESO-VLT). From this data set the rotational temperature of the H-3(+) ions in Jupiter's upper atmosphere was calculated using the ratio of the nu(2) Q(1,0(-)) and nu(2) Q(3,0(-)) fundamental emission lines. The entire northern auroral region was observed, providing a highly detailed view of ionospheric temperatures, which were mapped onto polar projections. The temperature range we derive in the northern auroral region is similar to 750-1000 K, which is consistent with past studies, although the temperature structure differs. We identify two broad regions which exhibit temperature changes over a short period of time (similar to 80 minutes). We propose that the changes in temperature could be due to a local time change in particle precipitation energy, or they could be caused by dynamic temperature changes generated in the neutral thermosphere due to the magnetospheric response to a transient enhancement of solar wind dynamic pressure, as predicted by models. By comparing the H-3(+) temperature, column density, total emission, and line-of-sight velocity, we were unable to identify a single dominant mechanism responsible for the energetics in Jupiter's northern auroral region. The comparison reveals that there is complex interplay between heating by impact from particle precipitation and Joule heating, as well as cooling by the H-3(+) thermostat effect. Plain Language Summary This study focuses on Jupiter's northern lights (aurora) and the temperature of the molecules which create them. A charged molecule, H-3(+), which exists in Jupiter's upper atmosphere, emits at infrared wavelengths. Using the Very Large Telescope, situated in Chile, we can observe Jupiter's infrared aurora. The telescope has an instrument that splits up the wavelengths of the aurora, creating spectra from which we can calculate the temperature, column density, and total emission ofJupiter's upper atmosphere. The whole polar region is observed, and maps of these parameters were created. By comparing these parameters, as well as the velocity of the charged molecules, which were calculated in our previous study, we can investigate the heating and cooling processes of Jupiter's upper atmosphere. This study is the first to measure temperature differences in Jupiter's aurora over short periods of time. These temperature changes could be caused by variations that happen during Jupiter's day or they could be caused by the response of Jupiter's magnetic field to a process external to the Jupiter system.