Magnetospheric Phenomena


This part of THEMIS wiki pages displays application of THEMIS data to magnetospheric research as well as related theoretical works and reviews. Magnetopause crossings by THEMIS probes give an unparalleled daily insight on the dayside magnetopause and its interaction with the solar wind.

Database

SPDF at NASA GSFC provides the database of events of Magnetopause Crossings (MCD) by THEMIS probes. This database represents THEMIS measurements and derived quantities characterizing magnetopause. Vector quantities are transformed into the Boundary-Normal Coordinates (BNC, also called LMN coordinates). The database provides the combination plots as well as numerical data. Plots are presented for download in a scalable graphics (PostScript and PDF) and in the GIF format for quick viewing using convenient SPDF GIFWALK web interface. (Even the authors of the database prefer to use GIFWALK for browsing through events instead of digging into the folders on the hard drive.)

Here is the database description, which also can be downloaded from the GIFWALK site. The MCD database structure is also explained in the slides of the talk by David Sibeck and Vladimir Kondratovich at the First Cluster-THEMIS workshop at the University of New Hampshire (Durham, 2008).

Before electric field boom deployment, it was impossible to measure the probe electric potential directly. Therefore, it was impossible to eliminate spurious photoelectrons before calculating electron moments. Vladimir Kondratovich and David Sibeck have developed and tested a procedure to salvage data with unknown (or inconsistent) spacecraft potentials. This procedure is routinely applied to THEMIS data provided on the pages and presented in the plots of MPC database. The procedure involves identifying the potential that best removes photoelectrons and brings ion and electron densities into agreement over extended periods of time. It is explained in the slides of the talk by David Sibeck and Vladimir Kondratovich at the First Cluster-THEMIS workshop at the University of New Hampshire (Durham, 2008). The common case is agreement of this potential (called Cutoff Potential, CP) with directly-measured spacecraft potential. The deviations between the two as well as the cases of diverging CP procedure can be tentatively associated with the presence of specific physical effects. The question is still under investigation. When CP procedure diverges, the direct measurements or default potential values from THEMIS database are used in MPC database.

Theoretical Work

* Geomagnetic Pulsations and Plasma Waves in the Earth's Magnetosphere. Review by John C. Samson. Click the thumbnail to download the full-size paper.

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