Dartmouth Events

Physics & Astronomy Colloquium - Claire Gasque '19, UC Berkeley

Title:"It's Not Easy Being Green: Unveiling an Imposter Aurora with Quantitative Modeling of Emissions Driven by Local Parallel Electric Fields"

Friday, January 5, 2024
3:30pm – 4:30pm
Wilder 104 & Zoom
Intended Audience(s): Public
Categories: Arts and Sciences, Lectures & Seminars

Abstract: The vibrant green streaks of the 'picket fence' typically appear below a STEVE arc in the subauroral sky, at lower latitudes than the auroral oval. Recent studies suggest that, despite its aurora-like appearance, the picket fence may not be driven by magnetospheric particle precipitation but instead by local electric fields parallel to Earth's magnetic field. We investigated this hypothesis by quantitatively comparing observed picket fence spectra with emissions generated in a kinetic model driven by parallel electric fields in a realistic neutral atmosphere. We find that sufficiently large parallel electric fields can reproduce the observed ratio of N2 first positive to oxygen green line emissions, without producing N2+ first negative emissions. At a typical picket fence altitude of 110 km, parallel electric fields between 40 and 70 Td (~80 to 150 mV/m at 110 km) result in calculated spectral features consistent with observed ones, providing a benchmark for future observational and modeling studies. Additionally, we review studies which have identified similar features to the picket fence in the aurora, suggesting that a similar mechanism may be at work there. Since visible and ultraviolet auroral emissions are increasingly used to infer magnetospheric activity, it is important to better understand and quantify potential sources of emission beyond particle precipitation.

***Join before the Colloquium at 3:00 pm for coffee, cookies and brownies from Lou's in Wilder 103!***

Hosted by Professor Robyn Millan & the Colloquium Committee

Please click the link below to join the webinar:
Email physics.department@dartmouth.edu for passcode


For more information, contact:
Tressena Manning

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