April 9, 2024 11:00 - 12:00 EDT
The Ever-changing Ionosphere of Uranus
Webinar Zoom Link
Presenter: Dr. Henrik Melin (University of Leicester)
Abstract: The upper atmosphere of the giant planets has two principal components, the neutral thermosphere and the charged particle ionosphere, with the latter acting as an important interface between the magnetosphere and the underlying atmosphere. Emissions from the ionospheric ion H3+ can be observed in the near-infrared, and via spectral analysis we can determine the temperature of the upper atmosphere and the density of the ions. H3+ was first detected at Uranus in 1992, and it has been observed using a variety of ground-based telescopes since. Analysis of all available observations have shown that the upper atmosphere has been slowly cooling on time-scales of decades, at a rate of about 8 K/year, and the reason for this remains largely unknown, and is not seen at either Jupiter or Saturn. As the upper atmosphere cools, H3+ emissions are becoming weaker, and the observations require longer and longer exposure times. Luckily, however, we have recent observations from the James Webb Space Telescope which greatly help our understanding of this enigmatic planet. In this seminar, I will discuss our current understanding of the ionosphere of Uranus, and explore opportunities for future missions to investigate the processes that occur in the upper atmosphere.