A detailed study of auroral fragments
Aurora occurs in various shapes, one of which is the hitherto unreported phenomenon of auroral fragments. For three periods of occurrence of these fragments their properties were studied in detail during this master’s thesis, using mainly ground-based instrumentation located near Longyearbyen on Sva...
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Uppsala universitet, Institutionen för fysik och astronomi
2019
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ftuppsalauniv:oai:DiVA.org:uu-388546 2023-05-15T16:04:41+02:00 A detailed study of auroral fragments Dreyer, Joshua 2019 application/pdf http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388546 eng eng Uppsala universitet, Institutionen för fysik och astronomi Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen The University Centre in Svalbard FYSAST FYSMAS1098 http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388546 info:eu-repo/semantics/openAccess aurora fragments Svalbard all-sky camera MSP ASK EISCAT Fusion Plasma and Space Physics plasma och rymdfysik Student thesis info:eu-repo/semantics/bachelorThesis text 2019 ftuppsalauniv 2023-02-23T21:50:34Z Aurora occurs in various shapes, one of which is the hitherto unreported phenomenon of auroral fragments. For three periods of occurrence of these fragments their properties were studied in detail during this master’s thesis, using mainly ground-based instrumentation located near Longyearbyen on Svalbard, Norway. A base dataset was constructed from 103 all-sky camera images, manually marking 305 fragments for further analysis. This thesis reports and describes the fragment observations during the observed events, including the auroral and geomagnetic context. Fragments generally seem to fall into two categories, the first being singular, apparently randomly distributed fragments, and the second being periodic fragments that occur in groups with a regular spacing close to auroral arcs. A typical fragment has a small horizontal size below 20 km, a short lifetime of less than a minute and shows no field-aligned extent in the emission. The fragments appear mainly west of zenith (73%) during the three observation nights, whereas their north-south distribution is symmetric around the zenith. Almost all of them exhibit westward drift, the estimated speed for one of the fragments passing the field of view of ASK is ∼1 km/s. A spectral signature can be seen in the green auroral wavelength of O at 557.7 nm and red emission line of N2 at 673.0 nm, but no emission enhancement was observed in the blue wavelengths. One fragment passing the EISCAT Svalbard radar’s field of view shows a local ion temperature increase in a small altitude range of ∼15 km, whereas there is no visible increase in electron density. This could be explained by fragment generation due to locally strong horizontal electric fields. A potential mechanism for this might be electric fields of atmospheric waves superposing with the converging electric fields of auroral arcs created by particle precipitation and the corresponding field-aligned currents. The resulting field would be perpendicular to the magnetic field and the auroral arcs, leading to wave-like ... Bachelor Thesis EISCAT Longyearbyen Svalbard Uppsala University: Publications (DiVA) Longyearbyen Norway Svalbard |
institution |
Open Polar |
collection |
Uppsala University: Publications (DiVA) |
op_collection_id |
ftuppsalauniv |
language |
English |
topic |
aurora fragments Svalbard all-sky camera MSP ASK EISCAT Fusion Plasma and Space Physics plasma och rymdfysik |
spellingShingle |
aurora fragments Svalbard all-sky camera MSP ASK EISCAT Fusion Plasma and Space Physics plasma och rymdfysik Dreyer, Joshua A detailed study of auroral fragments |
topic_facet |
aurora fragments Svalbard all-sky camera MSP ASK EISCAT Fusion Plasma and Space Physics plasma och rymdfysik |
description |
Aurora occurs in various shapes, one of which is the hitherto unreported phenomenon of auroral fragments. For three periods of occurrence of these fragments their properties were studied in detail during this master’s thesis, using mainly ground-based instrumentation located near Longyearbyen on Svalbard, Norway. A base dataset was constructed from 103 all-sky camera images, manually marking 305 fragments for further analysis. This thesis reports and describes the fragment observations during the observed events, including the auroral and geomagnetic context. Fragments generally seem to fall into two categories, the first being singular, apparently randomly distributed fragments, and the second being periodic fragments that occur in groups with a regular spacing close to auroral arcs. A typical fragment has a small horizontal size below 20 km, a short lifetime of less than a minute and shows no field-aligned extent in the emission. The fragments appear mainly west of zenith (73%) during the three observation nights, whereas their north-south distribution is symmetric around the zenith. Almost all of them exhibit westward drift, the estimated speed for one of the fragments passing the field of view of ASK is ∼1 km/s. A spectral signature can be seen in the green auroral wavelength of O at 557.7 nm and red emission line of N2 at 673.0 nm, but no emission enhancement was observed in the blue wavelengths. One fragment passing the EISCAT Svalbard radar’s field of view shows a local ion temperature increase in a small altitude range of ∼15 km, whereas there is no visible increase in electron density. This could be explained by fragment generation due to locally strong horizontal electric fields. A potential mechanism for this might be electric fields of atmospheric waves superposing with the converging electric fields of auroral arcs created by particle precipitation and the corresponding field-aligned currents. The resulting field would be perpendicular to the magnetic field and the auroral arcs, leading to wave-like ... |
format |
Bachelor Thesis |
author |
Dreyer, Joshua |
author_facet |
Dreyer, Joshua |
author_sort |
Dreyer, Joshua |
title |
A detailed study of auroral fragments |
title_short |
A detailed study of auroral fragments |
title_full |
A detailed study of auroral fragments |
title_fullStr |
A detailed study of auroral fragments |
title_full_unstemmed |
A detailed study of auroral fragments |
title_sort |
detailed study of auroral fragments |
publisher |
Uppsala universitet, Institutionen för fysik och astronomi |
publishDate |
2019 |
url |
http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388546 |
geographic |
Longyearbyen Norway Svalbard |
geographic_facet |
Longyearbyen Norway Svalbard |
genre |
EISCAT Longyearbyen Svalbard |
genre_facet |
EISCAT Longyearbyen Svalbard |
op_relation |
FYSAST FYSMAS1098 http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388546 |
op_rights |
info:eu-repo/semantics/openAccess |
_version_ |
1766400293982961664 |