Substorms and polar cap convection: the 10 January 2004 interplanetary CME case
The expansion-contraction model of Dungey cell plasma convection has two different convection sources, i.e. reconnections at the magnetopause and in the magnetotail. The spatial-temporal structure of the nightside source is not yet well understood. In this study we shall identify temporal v...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2012-01-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/30/67/2012/angeo-30-67-2012.pdf |
| _version_ | 1828488869824167936 |
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| author | Y. Andalsvik P. E. Sandholt C. J. Farrugia |
| author_facet | Y. Andalsvik P. E. Sandholt C. J. Farrugia |
| author_sort | Y. Andalsvik |
| collection | DOAJ |
| description | The expansion-contraction model of
Dungey cell plasma convection has two different convection
sources, i.e. reconnections at the magnetopause
and in the magnetotail. The spatial-temporal structure of the
nightside source is not yet well understood.
In this study we shall identify temporal variations
in the winter polar cap convection structure during substorm activity
under steady interplanetary conditions.
Substorm activity (electrojets and particle precipitations)
is monitored by
excellent ground-satellite DMSP F15 conjunctions in the
dusk-premidnight sector. We take advantage of the wide latitudinal
coverage of the IMAGE chain of ground magnetometers in
Svalbard – Scandinavia – Russia for the purpose of
monitoring magnetic deflections
associated with polar cap convection and substorm electrojets.
These are augmented by
direct observations of
polar cap convection derived from SuperDARN radars and
cross-track ion drift observations during
traversals of polar cap along the
dusk-dawn meridian by spacecraft DMSP F13.
The interval we study is characterized by
moderate, stable forcing of the
magnetosphere-ionosphere system
(<I>E</I><sub>KL</sub> = 4.0–4.5 mV m<sup>−1</sup>; cross polar cap potential (CPCP),
Φ (Boyle) = 115 kV)
during Earth passage of an
interplanetary CME (ICME), choosing an 4-h interval where
the magnetic field pointed continuously
south-west (<I>B</I><sub>z</sub> < 0; <I>B</I><sub>y</sub> < 0).
The combination of
continuous monitoring of ground magnetic deflections and
the F13 cross-track ion drift
observations in the polar cap allows us to infer the temporal
CPCP structure on time scales less than the ~10 min
duration of
F13 polar cap transits.
We arrived at the following estimates of the
dayside and nightside contributions to the CPCP
(CPCP = CPCP/day + CPCP/night)
under two intervals of substorm activity:
CPCP/day ~110 kV; CPCP/night ~50 kV (45% CPCP
increase during substorms).
The temporal CPCP structure during one of the substorm cases
resulted in a dawn-dusk convection asymmetry
measured by DMSP F13 which is
opposite to that expected from the prevailing
negative <I>B</I><sub>y</sub> polarity of the ICME magnetic field,
a clear indication of a nightside source. |
| first_indexed | 2024-12-11T10:15:18Z |
| format | Article |
| id | doaj.art-19166a4692ac4f06be946add8a7b3c98 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-11T10:15:18Z |
| publishDate | 2012-01-01 |
| publisher | Copernicus Publications |
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| series | Annales Geophysicae |
| spelling | doaj.art-19166a4692ac4f06be946add8a7b3c982022-12-22T01:11:37ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762012-01-0130678010.5194/angeo-30-67-2012Substorms and polar cap convection: the 10 January 2004 interplanetary CME caseY. Andalsvik0P. E. Sandholt1C. J. Farrugia2Department of Physics, University of Oslo, Oslo, NorwayDepartment of Physics, University of Oslo, Oslo, NorwaySpace Science Center, University of New Hampshire, Durham, USAThe expansion-contraction model of Dungey cell plasma convection has two different convection sources, i.e. reconnections at the magnetopause and in the magnetotail. The spatial-temporal structure of the nightside source is not yet well understood. In this study we shall identify temporal variations in the winter polar cap convection structure during substorm activity under steady interplanetary conditions. Substorm activity (electrojets and particle precipitations) is monitored by excellent ground-satellite DMSP F15 conjunctions in the dusk-premidnight sector. We take advantage of the wide latitudinal coverage of the IMAGE chain of ground magnetometers in Svalbard – Scandinavia – Russia for the purpose of monitoring magnetic deflections associated with polar cap convection and substorm electrojets. These are augmented by direct observations of polar cap convection derived from SuperDARN radars and cross-track ion drift observations during traversals of polar cap along the dusk-dawn meridian by spacecraft DMSP F13. The interval we study is characterized by moderate, stable forcing of the magnetosphere-ionosphere system (<I>E</I><sub>KL</sub> = 4.0–4.5 mV m<sup>−1</sup>; cross polar cap potential (CPCP), Φ (Boyle) = 115 kV) during Earth passage of an interplanetary CME (ICME), choosing an 4-h interval where the magnetic field pointed continuously south-west (<I>B</I><sub>z</sub> < 0; <I>B</I><sub>y</sub> < 0). The combination of continuous monitoring of ground magnetic deflections and the F13 cross-track ion drift observations in the polar cap allows us to infer the temporal CPCP structure on time scales less than the ~10 min duration of F13 polar cap transits. We arrived at the following estimates of the dayside and nightside contributions to the CPCP (CPCP = CPCP/day + CPCP/night) under two intervals of substorm activity: CPCP/day ~110 kV; CPCP/night ~50 kV (45% CPCP increase during substorms). The temporal CPCP structure during one of the substorm cases resulted in a dawn-dusk convection asymmetry measured by DMSP F13 which is opposite to that expected from the prevailing negative <I>B</I><sub>y</sub> polarity of the ICME magnetic field, a clear indication of a nightside source.https://www.ann-geophys.net/30/67/2012/angeo-30-67-2012.pdf |
| spellingShingle | Y. Andalsvik P. E. Sandholt C. J. Farrugia Substorms and polar cap convection: the 10 January 2004 interplanetary CME case Annales Geophysicae |
| title | Substorms and polar cap convection: the 10 January 2004 interplanetary CME case |
| title_full | Substorms and polar cap convection: the 10 January 2004 interplanetary CME case |
| title_fullStr | Substorms and polar cap convection: the 10 January 2004 interplanetary CME case |
| title_full_unstemmed | Substorms and polar cap convection: the 10 January 2004 interplanetary CME case |
| title_short | Substorms and polar cap convection: the 10 January 2004 interplanetary CME case |
| title_sort | substorms and polar cap convection the 10 january 2004 interplanetary cme case |
| url | https://www.ann-geophys.net/30/67/2012/angeo-30-67-2012.pdf |
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