High-latitude plasma convection during Northward IMF as derived from in-situ magnetospheric Cluster EDI measurements
In this study, we investigate statistical, systematic variations of the high-latitude convection cell structure during northward IMF. Using 1-min-averages of Cluster/EDI electron drift observations above the Northern and Southern polar cap areas for six and a half years (February 2001 till July...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2008-09-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/26/2685/2008/angeo-26-2685-2008.pdf |
| _version_ | 1818062076944318464 |
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| author | M. Förster S. E. Haaland S. E. Haaland G. Paschmann J. M. Quinn R. B. Torbert H. Vaith C. A. Kletzing |
| author_facet | M. Förster S. E. Haaland S. E. Haaland G. Paschmann J. M. Quinn R. B. Torbert H. Vaith C. A. Kletzing |
| author_sort | M. Förster |
| collection | DOAJ |
| description | In this study, we investigate statistical, systematic variations of the
high-latitude convection cell structure during northward IMF.
Using 1-min-averages of Cluster/EDI electron drift observations above
the Northern and Southern polar cap areas for six and a half years
(February 2001 till July 2007), and mapping the spatially distributed
measurements to a common reference plane at ionospheric level in a
magnetic latitude/MLT grid, we obtained regular drift patterns
according to the various IMF conditions.
We focus on the particular conditions during northward IMF, where
lobe cells at magnetic latitudes >80°
with opposite (sunward) convection over the central polar cap are
a permanent feature in addition to the main convection cells
at lower latitudes. They are due to reconnection processes at the
magnetopause boundary poleward of the cusp regions.
Mapped EDI data have a particular good coverage within the central part
of the polar cap, so that these patterns and their dependence on various
solar wind conditions are well verified in a statistical sense.
On average, 4-cell convection pattern are shown as regular structures
during periods of nearly northward IMF with the tendency of a
small shift toward negative clock angles.
The positions of these high-latitude convection foci are within 79°
to 85° magnetic latitude and 09:00–15:00 MLT. The MLT positions are
approximately symmetric ±2 h about 11:30 MLT, i.e. slightly
offset from midday toward prenoon hours,
while the maximum (minimum) potential of the high-latitude cells
is at higher magnetic latitudes near their maximum potential difference
at ≈−10° to −15° clock angle for the North (South)
Hemisphere.
With increasing clock angle distances from ≈IMF<I>B<sub>z</sub></I>+,
a gradual transition occurs from the 4-cell pattern via a 3-cell
to the common 2-cell convection pattern, in the course of which
one of the medium-scale high-latitude dayside cells diminishes and disappears
while the other intensifies and merges with the opposite main cell of the
same polarity to form the large "round-shaped" convection cell when
approaching a well-known IMF<I>B<sub>y</sub></I>-dominated configuration.
Opposite scenarios with interchanged roles of the respective cells occur
for the opposite turning of the clock angle and at the Southern Hemisphere.
The high-latitude dayside cells become more pronounced with increasing
magnitude of the IMF vector. |
| first_indexed | 2024-12-10T13:58:28Z |
| format | Article |
| id | doaj.art-aa4ff0dd769f41db82f682fafe5527f1 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-10T13:58:28Z |
| publishDate | 2008-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-aa4ff0dd769f41db82f682fafe5527f12022-12-22T01:45:52ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762008-09-01262685270010.5194/angeo-26-2685-2008High-latitude plasma convection during Northward IMF as derived from in-situ magnetospheric Cluster EDI measurementsM. Förster0S. E. Haaland1S. E. Haaland2G. Paschmann3J. M. Quinn4R. B. Torbert5H. Vaith6C. A. Kletzing7Helmholtz-Zentrum Potsdam, GeoForschungsZentrum (GFZ), 14473 Potsdam, GermanyMax-Planck-Institut für extraterrestrische Physik, 85748 Garching, Germanyalso at: Department of Physics, University of Bergen, NorwayMax-Planck-Institut für extraterrestrische Physik, 85748 Garching, GermanyBoston University, Boston, MA 02215, USAUniversity of New Hampshire, Durham, NH 03824, USAUniversity of New Hampshire, Durham, NH 03824, USAUniversity of Iowa, Iowa City, IA 52242, USAIn this study, we investigate statistical, systematic variations of the high-latitude convection cell structure during northward IMF. Using 1-min-averages of Cluster/EDI electron drift observations above the Northern and Southern polar cap areas for six and a half years (February 2001 till July 2007), and mapping the spatially distributed measurements to a common reference plane at ionospheric level in a magnetic latitude/MLT grid, we obtained regular drift patterns according to the various IMF conditions. We focus on the particular conditions during northward IMF, where lobe cells at magnetic latitudes >80° with opposite (sunward) convection over the central polar cap are a permanent feature in addition to the main convection cells at lower latitudes. They are due to reconnection processes at the magnetopause boundary poleward of the cusp regions. Mapped EDI data have a particular good coverage within the central part of the polar cap, so that these patterns and their dependence on various solar wind conditions are well verified in a statistical sense. On average, 4-cell convection pattern are shown as regular structures during periods of nearly northward IMF with the tendency of a small shift toward negative clock angles. The positions of these high-latitude convection foci are within 79° to 85° magnetic latitude and 09:00–15:00 MLT. The MLT positions are approximately symmetric ±2 h about 11:30 MLT, i.e. slightly offset from midday toward prenoon hours, while the maximum (minimum) potential of the high-latitude cells is at higher magnetic latitudes near their maximum potential difference at ≈−10° to −15° clock angle for the North (South) Hemisphere. With increasing clock angle distances from ≈IMF<I>B<sub>z</sub></I>+, a gradual transition occurs from the 4-cell pattern via a 3-cell to the common 2-cell convection pattern, in the course of which one of the medium-scale high-latitude dayside cells diminishes and disappears while the other intensifies and merges with the opposite main cell of the same polarity to form the large "round-shaped" convection cell when approaching a well-known IMF<I>B<sub>y</sub></I>-dominated configuration. Opposite scenarios with interchanged roles of the respective cells occur for the opposite turning of the clock angle and at the Southern Hemisphere. The high-latitude dayside cells become more pronounced with increasing magnitude of the IMF vector.https://www.ann-geophys.net/26/2685/2008/angeo-26-2685-2008.pdf |
| spellingShingle | M. Förster S. E. Haaland S. E. Haaland G. Paschmann J. M. Quinn R. B. Torbert H. Vaith C. A. Kletzing High-latitude plasma convection during Northward IMF as derived from in-situ magnetospheric Cluster EDI measurements Annales Geophysicae |
| title | High-latitude plasma convection during Northward IMF as derived from in-situ magnetospheric Cluster EDI measurements |
| title_full | High-latitude plasma convection during Northward IMF as derived from in-situ magnetospheric Cluster EDI measurements |
| title_fullStr | High-latitude plasma convection during Northward IMF as derived from in-situ magnetospheric Cluster EDI measurements |
| title_full_unstemmed | High-latitude plasma convection during Northward IMF as derived from in-situ magnetospheric Cluster EDI measurements |
| title_short | High-latitude plasma convection during Northward IMF as derived from in-situ magnetospheric Cluster EDI measurements |
| title_sort | high latitude plasma convection during northward imf as derived from in situ magnetospheric cluster edi measurements |
| url | https://www.ann-geophys.net/26/2685/2008/angeo-26-2685-2008.pdf |
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