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- Matsui, H., et al.
(author)
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Derivation of inner magnetospheric electric field (UNH-IMEF) model using Cluster data set
- 2008
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In: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 26:9, s. 2887-2898
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Journal article (peer-reviewed)abstract
- We derive an inner magnetospheric electric field (UNH-IMEF) model at L=2-10 using primarily Cluster electric field data for more than 5 years between February 2001 and October 2006. This electric field data set is divided into several ranges of the interplanetary electric field (IEF) values measured by ACE. As ring current simulations which require electric field as an input parameter are often performed at L=2-6.6, we have included statistical results from ground radars and low altitude satellites inside the perigee of Cluster in our data set (L similar to 4). Electric potential patterns are derived from the average electric fields by solving an inverse problem. The electric potential pattern for small IEF values is probably affected by the ionospheric dynamo. The magnitudes of the electric field increase around the evening local time as IEF increases, presumably due to the sub-auroral polarization stream (SAPS). Another region with enhanced electric fields during large IEF periods is located around 9 MLT at L>8, which is possibly related to solar wind-magnetosphere coupling. Our potential patterns are consistent with those derived from self-consistent simulations. As the potential patterns can be interpolated/extrapolated to any discrete IEF value within measured ranges, we thus derive an empirical electric potential model. The performance of the model is evaluated by comparing the electric field derived from the model with original one measured by Cluster and mapped to the equator. The model is open to the public through our website.
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- Puhl-Quinn, P. A., et al.
(author)
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An effort to derive an empirically based, inner-magnetospheric electric field model : Merging Cluster EDI and EFW data
- 2008
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In: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 70:2-4, s. 564-573
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Journal article (peer-reviewed)abstract
- A key ingredient for modelling many inner-magnetospheric processes is the realistic representation of the spatio-temporal dynamics of the inner-magnetospheric electric field, or, IMEF The Cluster Mission provides a unique opportunity to construct an IMEF model using electric field measurements from both the electron drift instrument (EDI) and the electric fields and waves instrument (EFW). A superset of IMEF data is formed by merging EDI and EFW data. Challenges presented by the merging process include the handling of compromised perpendicular electric field (E-L) calculations, electric field offsets, scaling problems, and spurious fields. The present goal is to produce the highest quality merged IMEF data set possible which is minimally affected by these issues. Preliminary investigation of the merging process on Cluster I for the years 2001-2003 has revealed that merging is a worthwhile exercise. The data sets are shown to be complementary, and the IMEF merged data set is superior to either data set alone in terms of improved spatial coverage, and coverage of a wider range of geomagnetic activity levels. Preliminary use of the merged IMEF data set to construct a parameterized, equatorial, electric field model for the inner magnetosphere, the UNH-IMEF model, is also presented. The electric field morphology produced by this preliminary version of the UNH-IMEF model shows the expected sensitivity to IMF orientation.
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