By Gareth Chisham (British Antarctic Survey)
Measurements of ionospheric plasma flow vorticity can be used for studying ionospheric plasma transport processes, such as convection and turbulence, over a wide range of spatial scales. This study presents an analysis of probability density functions (PDFs) of ionospheric vorticity for selected regions of the northern hemisphere high-latitude ionosphere as measured by the Super Dual Auroral Radar Network (SuperDARN) over a 6-year interval (2000-2005 inclusive). Making certain assumptions, the observed asymmetric vorticity PDFs can be decomposed into two separate components: (1) A single-sided function that results from the large-scale vorticity inherent in the ionospheric convection pattern, driven by magnetic reconnection; (2) A symmetric double-sided function that results from meso-scale vorticity that derives from fluid processes such as turbulence, and from measurement uncertainties.
Being able to model ionospheric vorticity in this way will help to improve models of ionospheric plasma flow that are often used in larger-scale system models. At the present time, these plasma flow models typically only consider the larger-scale convection flow. Our observation of a significant meso-scale flow vorticity component due to turbulence will have implications for the fidelity of these models.
See paper for further details: Chisham, G. and Freeman, M. P. (2023). Separating contributions to plasma vorticity in the high-latitude ionosphere from large-scale convection and meso-scale turbulence. Journal of Geophysical Research: Space Physics, 128, e2023JA031885, https://doi.org/10.1029/2023JA031885.
This resource is a collation of PhD student adverts from the MIST Community.
Please note that the list is not exhaustive and is not intended to be an accurate capture of all studentships in the MIST community.
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By Emma Thomas (University of Leicester)
Three decades of searching for the infrared aurorae finally come to a successful conclusion as portions of the northern (IAU southern) aurorae have been confirmed at Uranus. The icy planet represents an enigma within our solar system, with the first and only visit by Voyager II in 1986, it remains one of the least documented planets in our solar system. This is exceptionally apparent with the planet’s history of auroral observations, where the UV aurorae have been observed a handful of times but no infrared (IR) counterpart has been confirmed, despite both aurorae appearing at Jupiter and Saturn. Analysis of IR aurorae at both Jupiter and Saturn have challenged what we know about magnetosphere-ionosphere coupling, highlighting a need for IR analysis at Uranus to uncover its mysteries. Since 2020 our team has meticulously analysed archived data of Uranus during 2006 from the Keck II telescope on Mauna Kea in Hawai’i. The timing of these observations was key, close to equinox, as it provided an optimal view of the predicted locations of the northern and southern aurorae. By examining the emission lines from these aurorae (the emitting ion being H3+) between 3.94 to 4.01 μm, we carried out a full spectrum best fit across 5 fundamental lines for each spatial pixel across the planet’s disk. By comparing these lines at specific locations, we were able to identify an average 88% increase in column ion densities with no significant temperature changes localised close to or at expected auroral locations for the northern aurora. With this confirmation at Uranus, we look forward to a new age of auroral investigations at both ice giant planets.
Thomas, E.M., Melin, H., Stallard, T.S. et al. Detection of the infrared aurora at Uranus with Keck-NIRSPEC. Nat Astron (2023). https://doi.org/10.1038/s41550-023-02096-5