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A model for estimating the relation between the Hall to Pedersen conductance ratio and ground magnetic data derived from CHAMP satellite statistics
- Source :
- Annales Geophysicae, Vol 25, Pp 721-736 (2007), Annales Geophysicae, Vol 25, Iss 3, Pp 721-736 (2007)
- Publication Year :
- 2007
- Publisher :
- Copernicus GmbH, 2007.
-
Abstract
- The goal of this study is to find a way to statistically estimate the Hall to Pedersen conductance ratio α from ground magnetic data. We use vector magnetic data from the CHAMP satellite to derive this relation. α is attained from magnetic satellite data using the 1-D Spherical Elementary Current Systems (SECS). The ionospheric equivalent current density can either be computed from ground or satellite magnetic data. Under the required 1-D assumption, these two approaches are shown to be equal, which leads to the advantage that the statistics are not restricted to areas covered by ground data. Unlike other methods, using magnetic satellite measurements to determine α ensures reliable data over long time sequences. The statistical study, comprising over 6000 passes between 55° and 76.5° northern geomagnetic latitude during 2001 and 2002, is carried out employing data from the CHAMP satellite. The data are binned according to activity and season. In agreement with earlier studies, values between 1 and 3 are typically found for α. Good compatibility is found, when α attained from CHAMP data is compared with EISCAT radar measurements. The results make it possible to estimate α from the east-west equivalent current density Jφ; [A/km]: α=2.07/(36.54/|Jφ|+1) for JφJφ+1) for Jφ0 (eastward). Using the same data, statistics of ionospheric and field-aligned current densities as a function of geomagnetic latitude and MLT are included. These are binned with respect to activity, season and IMF BZ and BY. For the first time, all three current density components are simultaneously studied this way on a comparable spatial scale. With increasing activity, the enhancement and the equatorward expansion of the electrojets and the R1 and R2 currents is observed, and in the nightside, possible indications of a Cowling channel appear. During southward IMF BZ, the electrojets and the R1 and R2 currents are stronger and clearer than during northward BZ. IMF BY affects the orientation of the pattern.
- Subjects :
- Physics
Atmospheric Science
Satellite observation
[SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere
lcsh:QC801-809
Conductance
Geology
Astronomy and Astrophysics
Probability density function
lcsh:QC1-999
law.invention
lcsh:Geophysics. Cosmic physics
Space and Planetary Science
law
Satellite data
Statistics
[SDU.STU] Sciences of the Universe [physics]/Earth Sciences
Earth and Planetary Sciences (miscellaneous)
Geomagnetic latitude
lcsh:Q
Radar
Ionosphere
lcsh:Science
Current density
lcsh:Physics
Subjects
Details
- ISSN :
- 14320576
- Volume :
- 25
- Database :
- OpenAIRE
- Journal :
- Annales Geophysicae
- Accession number :
- edsair.doi.dedup.....349eabdfc095fa972e5f95b4e05100e8