On the motion of dayside auroras caused by a solar wind pressure pulse
Global ultraviolet auroral images from the IMAGE satellite were used to investigate the dynamics of the dayside auroral oval responding to a sudden impulse (SI) in the solar wind pressure. At the same time, the TV all-sky camera and the EISCAT radar on Svalbard (in the pre-noon sector) allowed for d...
Published in: | Annales Geophysicae |
---|---|
Main Authors: | , , , , , , |
Format: | Text |
Language: | English |
Published: |
2018
|
Subjects: | |
Online Access: | https://doi.org/10.5194/angeo-23-509-2005 https://angeo.copernicus.org/articles/23/509/2005/ |
id |
ftcopernicus:oai:publications.copernicus.org:angeo35370 |
---|---|
record_format |
openpolar |
spelling |
ftcopernicus:oai:publications.copernicus.org:angeo35370 2023-05-15T16:04:50+02:00 On the motion of dayside auroras caused by a solar wind pressure pulse Kozlovsky, A. Safargaleev, V. Østgaard, N. Turunen, T. Koustov, A. Jussila, J. Roldugin, A. 2018-09-27 application/pdf https://doi.org/10.5194/angeo-23-509-2005 https://angeo.copernicus.org/articles/23/509/2005/ eng eng doi:10.5194/angeo-23-509-2005 https://angeo.copernicus.org/articles/23/509/2005/ eISSN: 1432-0576 Text 2018 ftcopernicus https://doi.org/10.5194/angeo-23-509-2005 2020-07-20T16:27:30Z Global ultraviolet auroral images from the IMAGE satellite were used to investigate the dynamics of the dayside auroral oval responding to a sudden impulse (SI) in the solar wind pressure. At the same time, the TV all-sky camera and the EISCAT radar on Svalbard (in the pre-noon sector) allowed for detailed investigation of the auroral forms and the ionospheric plasma flow. After the SI, new discrete auroral forms appeared in the poleward part of the auroral oval so that the middle of the dayside oval moved poleward from about 70° to about 73° of the AACGM latitude. This poleward shift first occurred in the 15MLT sector, then similar shifts were observed in the MLT sectors located more westerly, and eventually the shift was seen in the 6 MLT sector. Thus, the auroral disturbance "propagated" westward (from 15MLT to 6MLT) at an apparent speed of the order of 7km/s. This motion of the middle of the auroral oval was caused by the redistribution of the luminosity within the oval and was not associated with the corresponding motion of the poleward boundary of the oval. The SI was followed by an increase in the northward plasma convection velocity. Individual auroral forms showed poleward progressions with velocities close to the velocity of the northward plasma convection. The observations indicate firstly a pressure disturbance propagation through the magnetosphere at a velocity of the order of 200km/s which is essentially slower than the velocity of the fast Alfvén (magnetosonic) wave, and secondly a potential (curl-free) electric field generation behind the front of the propagating disturbance, causing the motion of the auroras. We suggest a physical explanation for the slow propagation of the disturbance through the magnetosphere and a model for the electric field generation. Predictions of the model are supported by the global convection maps produced by the SuperDARN HF radars. Finally, the interchange instability and the eigenmode toroidal Alfvén oscillations are discussed as possible generation mechanisms for the dayside auroral forms launched by the SI. Text EISCAT Svalbard Copernicus Publications: E-Journals Curl ENVELOPE(-63.071,-63.071,-70.797,-70.797) Svalbard Annales Geophysicae 23 2 509 521 |
institution |
Open Polar |
collection |
Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
Global ultraviolet auroral images from the IMAGE satellite were used to investigate the dynamics of the dayside auroral oval responding to a sudden impulse (SI) in the solar wind pressure. At the same time, the TV all-sky camera and the EISCAT radar on Svalbard (in the pre-noon sector) allowed for detailed investigation of the auroral forms and the ionospheric plasma flow. After the SI, new discrete auroral forms appeared in the poleward part of the auroral oval so that the middle of the dayside oval moved poleward from about 70° to about 73° of the AACGM latitude. This poleward shift first occurred in the 15MLT sector, then similar shifts were observed in the MLT sectors located more westerly, and eventually the shift was seen in the 6 MLT sector. Thus, the auroral disturbance "propagated" westward (from 15MLT to 6MLT) at an apparent speed of the order of 7km/s. This motion of the middle of the auroral oval was caused by the redistribution of the luminosity within the oval and was not associated with the corresponding motion of the poleward boundary of the oval. The SI was followed by an increase in the northward plasma convection velocity. Individual auroral forms showed poleward progressions with velocities close to the velocity of the northward plasma convection. The observations indicate firstly a pressure disturbance propagation through the magnetosphere at a velocity of the order of 200km/s which is essentially slower than the velocity of the fast Alfvén (magnetosonic) wave, and secondly a potential (curl-free) electric field generation behind the front of the propagating disturbance, causing the motion of the auroras. We suggest a physical explanation for the slow propagation of the disturbance through the magnetosphere and a model for the electric field generation. Predictions of the model are supported by the global convection maps produced by the SuperDARN HF radars. Finally, the interchange instability and the eigenmode toroidal Alfvén oscillations are discussed as possible generation mechanisms for the dayside auroral forms launched by the SI. |
format |
Text |
author |
Kozlovsky, A. Safargaleev, V. Østgaard, N. Turunen, T. Koustov, A. Jussila, J. Roldugin, A. |
spellingShingle |
Kozlovsky, A. Safargaleev, V. Østgaard, N. Turunen, T. Koustov, A. Jussila, J. Roldugin, A. On the motion of dayside auroras caused by a solar wind pressure pulse |
author_facet |
Kozlovsky, A. Safargaleev, V. Østgaard, N. Turunen, T. Koustov, A. Jussila, J. Roldugin, A. |
author_sort |
Kozlovsky, A. |
title |
On the motion of dayside auroras caused by a solar wind pressure pulse |
title_short |
On the motion of dayside auroras caused by a solar wind pressure pulse |
title_full |
On the motion of dayside auroras caused by a solar wind pressure pulse |
title_fullStr |
On the motion of dayside auroras caused by a solar wind pressure pulse |
title_full_unstemmed |
On the motion of dayside auroras caused by a solar wind pressure pulse |
title_sort |
on the motion of dayside auroras caused by a solar wind pressure pulse |
publishDate |
2018 |
url |
https://doi.org/10.5194/angeo-23-509-2005 https://angeo.copernicus.org/articles/23/509/2005/ |
long_lat |
ENVELOPE(-63.071,-63.071,-70.797,-70.797) |
geographic |
Curl Svalbard |
geographic_facet |
Curl Svalbard |
genre |
EISCAT Svalbard |
genre_facet |
EISCAT Svalbard |
op_source |
eISSN: 1432-0576 |
op_relation |
doi:10.5194/angeo-23-509-2005 https://angeo.copernicus.org/articles/23/509/2005/ |
op_doi |
https://doi.org/10.5194/angeo-23-509-2005 |
container_title |
Annales Geophysicae |
container_volume |
23 |
container_issue |
2 |
container_start_page |
509 |
op_container_end_page |
521 |
_version_ |
1766400466773606400 |