Physics and Astronomy Thesis Defense - Robert Clayton, Dartmouth

Dartmouth Events

Physics and Astronomy Thesis Defense - Robert Clayton, Dartmouth

Title: "Modeling and Reconstruction of in Situ Ionospheric Plasma Flow Data Near Auroral Arcs Utilizing Auroral Imagery"

Monday, March 4, 2019
2:00pm-4:00pm
Wilder 202
Intended Audience(s): Public
Categories: Lectures & Seminars
Abstract: Some existing auroral data products are insufficient for ionospheric simulation input on sub kilometer spatial scales and high (second) time resolution near the boundaries of arc structures. Ideally, two-dimensional data maps of the relevant parameters over these small scales would provide models with constraining inputs.  Available in situ data have the time and spatial resolution for small scale features, but only provide a 1-d cut through the structure.  Groundbased data can provide 2-d maps, but are typically much lower resolution in time and space than is required to accurately interpret the small scale structure near an arc.  We provide a method to construct two-dimensional maps of auroral parameters from the combination of one-dimensional in situ data cuts with groundbased (2-d and time) camera imagery.  Arc boundaries for each image are defined and the available 1-d ionospheric flow data are replicated into many 1-d cuts at different points along the arc, yielding an irregularly sampled 2-d flow map.  These mapped data are fitted to a regular grid via a divergence minimization routine to generate a regularly sampled flow field that is enforced as divergence free.  Comparison of the generated 2-d data maps to available information from camera inversions and other data products are shown, as are assumptions made through the replication process and alternative strategies.  Reconstructed flow maps are shown to maintain the small scale features near arc boundaries while increasing the dimensionality to 2-d, and to follow the time evolution of the arc structure by comparisons to imagery.  We use the GEMINI 3-d model to create 3-d and time simulations of auroral ionospheric parameters in the localized several hundred kilometer region surrounding an auroral arc.  Using reconstructed higher density spatial and temporal maps over the full 2-d auroral region, the GEMINI 3d model can now resolve few kilometer fine-scale flow structures in the vicinity of an auroral arc.  Comparisons of model results (driven with various combinations of the mapped ground based and in situ data) to radar density profiles and in situ current and particle observations are presented.   The predominant source of field aligned current closure for these slow time variation events is seen to be from the conductivity gradients, in contrast to another more rapidly changing event where the divergence of the electric field can be the dominant driver.
 
For more information, contact:
Tressena Manning
603-646-2854

Events are free and open to the public unless otherwise noted.