Morphological evolution and spatial profile changes of poleward moving auroral forms
We investigated the morphology of poleward moving auroral forms (PMAFs) qualitatively by visual inspection of all-sky camera (ASC) images and quantitatively using the arciness index. The PMAFs in this study were initially identified with a meridian scanning photometer (MSP) located at the Kjell Henr...
Published in: | Annales Geophysicae |
---|---|
Main Authors: | , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Copernicus Publications
2023
|
Subjects: | |
Online Access: | https://doi.org/10.5194/angeo-41-115-2023 https://doaj.org/article/dcc7ba3f3382470187d1133d40431fac |
id |
ftdoajarticles:oai:doaj.org/article:dcc7ba3f3382470187d1133d40431fac |
---|---|
record_format |
openpolar |
spelling |
ftdoajarticles:oai:doaj.org/article:dcc7ba3f3382470187d1133d40431fac 2023-05-15T17:48:28+02:00 Morphological evolution and spatial profile changes of poleward moving auroral forms A. Goertz N. Partamies D. Whiter L. Baddeley 2023-03-01T00:00:00Z https://doi.org/10.5194/angeo-41-115-2023 https://doaj.org/article/dcc7ba3f3382470187d1133d40431fac EN eng Copernicus Publications https://angeo.copernicus.org/articles/41/115/2023/angeo-41-115-2023.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-41-115-2023 0992-7689 1432-0576 https://doaj.org/article/dcc7ba3f3382470187d1133d40431fac Annales Geophysicae, Vol 41, Pp 115-128 (2023) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 2023 ftdoajarticles https://doi.org/10.5194/angeo-41-115-2023 2023-03-26T01:35:40Z We investigated the morphology of poleward moving auroral forms (PMAFs) qualitatively by visual inspection of all-sky camera (ASC) images and quantitatively using the arciness index. The PMAFs in this study were initially identified with a meridian scanning photometer (MSP) located at the Kjell Henriksen Observatory (KHO), Svalbard, and analyzed using ASC images taken by cameras at the KHO and in Ny-Ålesund, Svalbard. We present a detailed six-step evolution of PMAF morphology in two dimensions. This evolution includes (1) an equatorward expansion of the auroral oval and an intensification of auroral brightness at the open–closed boundary (OCB), (2) the appearance of an arc-like structure in the oval, (3) poleward and possible west/eastward propagation, (4) azimuthal expansion events, (5) re-brightening of the PMAF and eventual (6) fading away. This is the first work dedicated to the morphological evolution of PMAFs and it includes more detailed discussion and novel aspects, such as the observation of initial merging of 557.7 nm auroral patches to form a PMAF. Moreover, the morphology of PMAFs is quantified using the arciness index, which is a number describing how arc-like auroral forms appear in ASC images. This allows an unbiased statistical investigation of auroral morphology. We present the results of a superposed epoch analysis of arciness in relation to PMAF occurrence. This analysis uncovered that arciness increases suddenly during the onset of a PMAF event and decreases over the PMAF lifetime to return to its baseline value once the event has concluded. This behavior may be understood based on changes in the morphology of PMAFs and validates our understanding of PMAF morphology. Furthermore, our findings relating to arciness may enable automatic identification of PMAFs, which has been found to be notoriously difficult. Article in Journal/Newspaper Ny Ålesund Ny-Ålesund Svalbard Directory of Open Access Journals: DOAJ Articles Ny-Ålesund Svalbard Annales Geophysicae 41 1 115 128 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
spellingShingle |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 A. Goertz N. Partamies D. Whiter L. Baddeley Morphological evolution and spatial profile changes of poleward moving auroral forms |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
We investigated the morphology of poleward moving auroral forms (PMAFs) qualitatively by visual inspection of all-sky camera (ASC) images and quantitatively using the arciness index. The PMAFs in this study were initially identified with a meridian scanning photometer (MSP) located at the Kjell Henriksen Observatory (KHO), Svalbard, and analyzed using ASC images taken by cameras at the KHO and in Ny-Ålesund, Svalbard. We present a detailed six-step evolution of PMAF morphology in two dimensions. This evolution includes (1) an equatorward expansion of the auroral oval and an intensification of auroral brightness at the open–closed boundary (OCB), (2) the appearance of an arc-like structure in the oval, (3) poleward and possible west/eastward propagation, (4) azimuthal expansion events, (5) re-brightening of the PMAF and eventual (6) fading away. This is the first work dedicated to the morphological evolution of PMAFs and it includes more detailed discussion and novel aspects, such as the observation of initial merging of 557.7 nm auroral patches to form a PMAF. Moreover, the morphology of PMAFs is quantified using the arciness index, which is a number describing how arc-like auroral forms appear in ASC images. This allows an unbiased statistical investigation of auroral morphology. We present the results of a superposed epoch analysis of arciness in relation to PMAF occurrence. This analysis uncovered that arciness increases suddenly during the onset of a PMAF event and decreases over the PMAF lifetime to return to its baseline value once the event has concluded. This behavior may be understood based on changes in the morphology of PMAFs and validates our understanding of PMAF morphology. Furthermore, our findings relating to arciness may enable automatic identification of PMAFs, which has been found to be notoriously difficult. |
format |
Article in Journal/Newspaper |
author |
A. Goertz N. Partamies D. Whiter L. Baddeley |
author_facet |
A. Goertz N. Partamies D. Whiter L. Baddeley |
author_sort |
A. Goertz |
title |
Morphological evolution and spatial profile changes of poleward moving auroral forms |
title_short |
Morphological evolution and spatial profile changes of poleward moving auroral forms |
title_full |
Morphological evolution and spatial profile changes of poleward moving auroral forms |
title_fullStr |
Morphological evolution and spatial profile changes of poleward moving auroral forms |
title_full_unstemmed |
Morphological evolution and spatial profile changes of poleward moving auroral forms |
title_sort |
morphological evolution and spatial profile changes of poleward moving auroral forms |
publisher |
Copernicus Publications |
publishDate |
2023 |
url |
https://doi.org/10.5194/angeo-41-115-2023 https://doaj.org/article/dcc7ba3f3382470187d1133d40431fac |
geographic |
Ny-Ålesund Svalbard |
geographic_facet |
Ny-Ålesund Svalbard |
genre |
Ny Ålesund Ny-Ålesund Svalbard |
genre_facet |
Ny Ålesund Ny-Ålesund Svalbard |
op_source |
Annales Geophysicae, Vol 41, Pp 115-128 (2023) |
op_relation |
https://angeo.copernicus.org/articles/41/115/2023/angeo-41-115-2023.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-41-115-2023 0992-7689 1432-0576 https://doaj.org/article/dcc7ba3f3382470187d1133d40431fac |
op_doi |
https://doi.org/10.5194/angeo-41-115-2023 |
container_title |
Annales Geophysicae |
container_volume |
41 |
container_issue |
1 |
container_start_page |
115 |
op_container_end_page |
128 |
_version_ |
1766154554567557120 |