High-latitude plasma convection from Cluster EDI: variances and solar wind correlations
Based on drift velocity measurements of the EDI instruments on Cluster during the years 2001–2006, we have constructed a database of high-latitude ionospheric convection velocities and associated solar wind and magnetospheric activity parameters. In an earlier paper (Haaland et al., 20...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2007-07-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/25/1691/2007/angeo-25-1691-2007.pdf |
| _version_ | 1828542345099870208 |
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| author | M. Förster G. Paschmann S. E. Haaland S. E. Haaland J. M. Quinn R. B. Torbert H. Vaith C. A. Kletzing |
| author_facet | M. Förster G. Paschmann S. E. Haaland S. E. Haaland J. M. Quinn R. B. Torbert H. Vaith C. A. Kletzing |
| author_sort | M. Förster |
| collection | DOAJ |
| description | Based on drift velocity measurements of the EDI instruments on Cluster during
the years 2001–2006, we have constructed a database of high-latitude
ionospheric convection velocities and associated solar wind and magnetospheric
activity parameters.
In an earlier paper (Haaland et al., 2007), we have described the method, consisting
of an improved technique for calculating the propagation delay between the
chosen solar wind monitor (ACE) and Earth's magnetosphere, filtering the data
for periods of sufficiently stable IMF orientations, and mapping the EDI
measurements from their high-altitude positions to ionospheric altitudes.
The present paper extends this study, by looking at the spatial pattern of the
variances of the convection velocities as a function of IMF orientation, and
by performing sortings of the data according to the IMF magnitude in the
GSM y-z plane, |<I>B<sub>yz</sub></I><sup>IMF</sup>|, the estimated reconnection electric field, <I>E<sub>r,sw</sub></I>,
the
solar wind dynamic pressure, <I>P</I><sub>dyn</sub>, the season, and indices characterizing
the ring current (<I>D<sub>st</sub></I>) and tail activity (ASYM-H).
The variability of the high-latitude convection shows characteristic spatial
patterns, which are mirror symmetric between the Northern and Southern
Hemispheres with respect to the IMF <I>B<sub>y</sub></I> component.
The latitude range of the highest variability zone varies with
IMF <I>B<sub>z</sub></I> similar to the auroral oval extent.
The magnitude of convection standard deviations is of the same order as,
or even larger than, the convection magnitude itself.
Positive correlations of polar cap activity are found with |<I>B<sub>yz</sub></I><sup>IMF</sup>|
and with <I>E<sub>r,sw</sub></I>,
in particular.
The strict linear increase for small magnitudes of <I>E<sub>r,sw</sub></I> starts to deviate
toward a flattened increase above about 2 mV/m.
There is also a weak positive correlation with <I>P</I><sub>dyn</sub>.
At very small values of <I>P</I><sub>dyn</sub>, a secondary maximum appears, which is even
more pronounced for the correlation with solar wind proton density.
Evidence for enhanced nightside convection during high nightside activity
is presented. |
| first_indexed | 2024-12-12T01:54:36Z |
| format | Article |
| id | doaj.art-6430fb02694345e0a19e49ddbfc295b9 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-12T01:54:36Z |
| publishDate | 2007-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-6430fb02694345e0a19e49ddbfc295b92022-12-22T00:42:24ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762007-07-01251691170710.5194/angeo-25-1691-2007High-latitude plasma convection from Cluster EDI: variances and solar wind correlationsM. Förster0G. Paschmann1S. E. Haaland2S. E. Haaland3J. M. Quinn4R. B. Torbert5H. Vaith6C. A. Kletzing7GeoForschungsZentrum Potsdam, Potsdam, GermanyMax-Planck-Institut für extraterrestrische Physik, 85748 Garching, GermanyMax-Planck-Institut für extraterrestrische Physik, 85748 Garching, GermanyDepartment of Physics, University of Bergen, NorwayBoston University, Boston, MA 02215, USAUniversity of New Hampshire, Durham, NH 03824, USAMax-Planck-Institut für extraterrestrische Physik, 85748 Garching, GermanyUniversity of Iowa, Iowa City, IA 52242, USABased on drift velocity measurements of the EDI instruments on Cluster during the years 2001–2006, we have constructed a database of high-latitude ionospheric convection velocities and associated solar wind and magnetospheric activity parameters. In an earlier paper (Haaland et al., 2007), we have described the method, consisting of an improved technique for calculating the propagation delay between the chosen solar wind monitor (ACE) and Earth's magnetosphere, filtering the data for periods of sufficiently stable IMF orientations, and mapping the EDI measurements from their high-altitude positions to ionospheric altitudes. The present paper extends this study, by looking at the spatial pattern of the variances of the convection velocities as a function of IMF orientation, and by performing sortings of the data according to the IMF magnitude in the GSM y-z plane, |<I>B<sub>yz</sub></I><sup>IMF</sup>|, the estimated reconnection electric field, <I>E<sub>r,sw</sub></I>, the solar wind dynamic pressure, <I>P</I><sub>dyn</sub>, the season, and indices characterizing the ring current (<I>D<sub>st</sub></I>) and tail activity (ASYM-H). The variability of the high-latitude convection shows characteristic spatial patterns, which are mirror symmetric between the Northern and Southern Hemispheres with respect to the IMF <I>B<sub>y</sub></I> component. The latitude range of the highest variability zone varies with IMF <I>B<sub>z</sub></I> similar to the auroral oval extent. The magnitude of convection standard deviations is of the same order as, or even larger than, the convection magnitude itself. Positive correlations of polar cap activity are found with |<I>B<sub>yz</sub></I><sup>IMF</sup>| and with <I>E<sub>r,sw</sub></I>, in particular. The strict linear increase for small magnitudes of <I>E<sub>r,sw</sub></I> starts to deviate toward a flattened increase above about 2 mV/m. There is also a weak positive correlation with <I>P</I><sub>dyn</sub>. At very small values of <I>P</I><sub>dyn</sub>, a secondary maximum appears, which is even more pronounced for the correlation with solar wind proton density. Evidence for enhanced nightside convection during high nightside activity is presented.https://www.ann-geophys.net/25/1691/2007/angeo-25-1691-2007.pdf |
| spellingShingle | M. Förster G. Paschmann S. E. Haaland S. E. Haaland J. M. Quinn R. B. Torbert H. Vaith C. A. Kletzing High-latitude plasma convection from Cluster EDI: variances and solar wind correlations Annales Geophysicae |
| title | High-latitude plasma convection from Cluster EDI: variances and solar wind correlations |
| title_full | High-latitude plasma convection from Cluster EDI: variances and solar wind correlations |
| title_fullStr | High-latitude plasma convection from Cluster EDI: variances and solar wind correlations |
| title_full_unstemmed | High-latitude plasma convection from Cluster EDI: variances and solar wind correlations |
| title_short | High-latitude plasma convection from Cluster EDI: variances and solar wind correlations |
| title_sort | high latitude plasma convection from cluster edi variances and solar wind correlations |
| url | https://www.ann-geophys.net/25/1691/2007/angeo-25-1691-2007.pdf |
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