Bibliography

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Found 7 entries in the Bibliography.

Showing entries from 1 through 7

2022

Transpolar Arcs: Seasonal Dependence Identified by an Automated Detection Algorithm

Transpolar arcs (TPAs) are auroral features that occur polewards of the main auroral oval suggesting that the magnetosphere has acquired a complicated magnetic topology. They are primarily a northward interplanetary magnetic field (IMF) auroral phenomenon, and their formation and evolution have no single explanation that is unanimously agreed upon. An automated detection algorithm has been developed to detect the occurrence of TPAs in UV images captured from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instrument onboard the Defense Meteorological Satellite Program (DMSP) spacecraft, in order to further study their occurrence. Via this detection algorithm TPAs are identified as a peak in the average radiance intensity poleward of 12.5° colatitude, in two or more of the wavelengths/bands sensed by SSUSI. Using the detection algorithm for the years 2010 to 2016, over 5000 images containing TPAs are identified. The occurrence of these TPAs shows a seasonal dependence, with more arcs being visible in the winter hemisphere. The orbital plane of DMSP has been investigated as a possible explanation of the dependences in the results of the detection algorithm. For the spacecraft of interest this leads to a preferential observation of the northern hemisphere with the detection algorithm missing TPAs in the southern hemisphere around 01–06 UT. No seasonal bias has been found for these spacecraft. We discuss the ramifications of these findings in terms of proposed TPA generation mechanisms and suggest reasons for the seasonal dependence including it being a reflection of probability of seeing TPAs due to visibility.

Bower, G.; Milan, S.; Paxton, L.; Imber, S.;

Published by: Journal of Geophysical Research: Space Physics Published on:

YEAR: 2022 DOI: 10.1029/2021JA029743

auroras; magnetosphere; transpolar arc

Occurrence statistics of horse collar aurora

Bower, Gemma; Milan, Stephen; Paxton, Larry; Anderson, Brian;

Published by: Journal of Geophysical Research: Space Physics Published on:

YEAR: 2022 DOI:

Statistics of transpolar arcs identified by an automated detection algorithm

Bower, Gemma; Milan, Steve; Paxton, Larry; Imber, Suzie;

Published by: Published on:

YEAR: 2022 DOI:

Lobe Reconnection and Cusp-Aligned Auroral Arcs

Abstract Following the St. Patrick s Day (17 March) geomagnetic storm of 2013, the interplanetary magnetic field had near-zero clock angle for almost two days. Throughout this period multiple cusp-aligned auroral arcs formed in the polar regions; we present observations of, and provide a new explanation for, this poorly understood phenomenon. The arcs were observed by auroral imagers onboard satellites of the Defense Meteorological Satellite Program. Ionospheric flow measurements and observations of energetic particles from the same satellites show that the arcs were produced by inverted-V precipitation associated with upward field-aligned currents (FACs) at shears in the convection pattern. The large-scale convection pattern revealed by the Super Dual Auroral Radar Network and the corresponding FAC pattern observed by the Active Magnetosphere and Planetary Electrodynamics Response Experiment suggest that dual-lobe reconnection was ongoing to produce significant closure of the magnetosphere. However, we propose that once the magnetosphere became nearly closed complicated lobe reconnection geometries arose that produced interleaving of regions of open and closed magnetic flux and spatial and temporal structure in the convection pattern that evolved on timescales shorter than the orbital period of the DMSP spacecraft. This new model naturally explains many features of cusp-aligned arcs, including why they focus in from the nightside toward the cusp region.

Milan, S.; Bower, G.; Carter, J.; Paxton, L.; Anderson, B.; Hairston, M.;

Published by: Journal of Geophysical Research: Space Physics Published on:

YEAR: 2022 DOI: https://doi.org/10.1029/2021JA030089

2021

Transpolar arcs: Seasonal dependence identified by an automated detection algorithm

Bower, Gemma; Milan, Stephen; Paxton, Larry;

Published by: Earth and Space Science Open Archive ESSOAr Published on:

YEAR: 2021 DOI:

Dual-lobe reconnection and cusp-aligned auroral arcs

Milan, Stephen; Bower, Gemma; Carter, Jennifer; Paxton, Larry; Anderson, Brian; Hairston, Marc;

Published by: Published on:

YEAR: 2021 DOI: