TY - JOUR
T1 - On the green isolated proton auroras during Canada thanksgiving geomagnetic storm
AU - Liang, Jun
AU - Gillies, D.
AU - Donovan, E.
AU - Parry, H.
AU - Mann, I.
AU - Connors, M.
AU - Spanswick, E.
N1 - Funding Information:
The study is supported by the Canadian Space Agency (CSA). TREx is jointly funded by the Canada Foundation for Innovation (CFI), Alberta Economic Development and Trade, and the University of Calgary. FESO is supported by CFI and CSA. AUGSO is supported by the CFI. AUGSO, TREx, and FESO data are publicly available at http://data.phys.ucalgary.ca/sort_by_project/other/publication_datasets/fspas.2022.0908 . CARISMA is operated by the University of Alberta and funded by CSA. CARISMA data can be downloaded at https://carisma.ca/ . Swarm mission is supported by the European Space Agency; Swarm data can be accessed at http://earth.esa.int/swarm . DMSP SSJ data are downloaded from http://cedar.openmadrigal.org/ . GOES data used in this study are from https://ngdc.noaa.gov/stp/satellite/goes-r.html .
Publisher Copyright:
Copyright © 2022 Liang, Gillies, Donovan, Parry, Mann, Connors and Spanswick.
PY - 2022/10/13
Y1 - 2022/10/13
N2 - The existence of detached/isolated auroral structures in the subauroral ionosphere has been recognized and studied for decades. One major subset of such detached auroras is the so-called “isolated proton aurora” (IPA). IPA is characterized by substantial hydrogen emissions and thus inferred to be proton aurora, but is also accompanied by other emission lines. In particular, IPA is usually dominated by 557.7 nm green-line emissions in optical luminosity. To date, there is still a lack of dedicated spectrographic study and detailed comparison among structures in different emission lines of IPA. The intensity ratios between the 557.7 nm and hydrogen emissions in IPA have not been well established from concurrent observations or theoretical models. In this study, we report an IPA event during ∼0245–0345 UT on 12 October 2021, the Canada Thanksgiving storm night. Using multi-station, multi-wavelength optical instruments, including the Transition Region Explorer (TREx) spectrograph, we investigate the evolution and spectrographic properties of the IPA. In-situ and ground magnetometer data show evidence of electromagnetic ion cyclotron (EMIC) waves associated with the passage of IPA, supporting a causal link between the EMIC wave and the proton precipitation. The precipitating proton energies are estimated to range between a few keV and a few tens of keV according to the IPA emission heights inferred from triangulation analyses. Via careful examination of the spectral intensities and the elevation-angle profiles of the 557.7, 427.8, and 486.1 nm emissions based on the spectrograph data, we conclude that the 557.7 nm emissions contained in the IPA were unlikely to owe their source to energetic electron precipitation from the magnetosphere, but were the byproduct of the proton precipitation. The intensity ratio between the 557.7 nm (427.8 nm) and the 486.1 nm emissions of the IPA are confined within a relatively narrow range around ∼26 (∼4), which may serve as validation tests for existing and developing proton transport models.
AB - The existence of detached/isolated auroral structures in the subauroral ionosphere has been recognized and studied for decades. One major subset of such detached auroras is the so-called “isolated proton aurora” (IPA). IPA is characterized by substantial hydrogen emissions and thus inferred to be proton aurora, but is also accompanied by other emission lines. In particular, IPA is usually dominated by 557.7 nm green-line emissions in optical luminosity. To date, there is still a lack of dedicated spectrographic study and detailed comparison among structures in different emission lines of IPA. The intensity ratios between the 557.7 nm and hydrogen emissions in IPA have not been well established from concurrent observations or theoretical models. In this study, we report an IPA event during ∼0245–0345 UT on 12 October 2021, the Canada Thanksgiving storm night. Using multi-station, multi-wavelength optical instruments, including the Transition Region Explorer (TREx) spectrograph, we investigate the evolution and spectrographic properties of the IPA. In-situ and ground magnetometer data show evidence of electromagnetic ion cyclotron (EMIC) waves associated with the passage of IPA, supporting a causal link between the EMIC wave and the proton precipitation. The precipitating proton energies are estimated to range between a few keV and a few tens of keV according to the IPA emission heights inferred from triangulation analyses. Via careful examination of the spectral intensities and the elevation-angle profiles of the 557.7, 427.8, and 486.1 nm emissions based on the spectrograph data, we conclude that the 557.7 nm emissions contained in the IPA were unlikely to owe their source to energetic electron precipitation from the magnetosphere, but were the byproduct of the proton precipitation. The intensity ratio between the 557.7 nm (427.8 nm) and the 486.1 nm emissions of the IPA are confined within a relatively narrow range around ∼26 (∼4), which may serve as validation tests for existing and developing proton transport models.
KW - EMIC wave
KW - green-line emission
KW - hydrogen emission
KW - isolated proton aurora
KW - TREX
UR - http://www.scopus.com/inward/record.url?scp=85140750195&partnerID=8YFLogxK
U2 - 10.3389/fspas.2022.1040092
DO - 10.3389/fspas.2022.1040092
M3 - Journal Article
AN - SCOPUS:85140750195
VL - 9
JO - Frontiers in Astronomy and Space Sciences
JF - Frontiers in Astronomy and Space Sciences
M1 - 1040092
ER -