Another important factor is the state of the solar wind, in particular, the orientation and strength of the interplanetary magnetic field , "carried" to the Earth's orbit from Sun, owing to the high electrical conductivity of the solar wind plasma. Interaction between the terrestrial and interplanetary fields becomes especially effective, when the interplanetary magnetic field is directed antiparallel to the Earth's field on the dayside boundary of the magnetosphere. In this case the geomagnetic and interplanetary field lines connect across the magnetospheric boundary, which greatly enhances the transfer of the solar wind mass, energy, and electric field inside the magnetosphere. As a result, the magnetospheric field and plasma become involved in a convection, as illustrated in the following animation:
In actuality, this kind of stationary convection is rarely realized. The solar wind is not steady: periods of quiet flow are often interrupted by strong "gusts", and the interplanetary magnetic field fluctuates both in magnitude and orientation. This results in dramatic dynamical changes of the entire magnetospheric configuration, which culminate in magnetospheric storms, accompanied by an explosive conversion of huge amounts of the solar wind energy into the kinetic energy of charged particles in the near-Earth space, manifested in polar auroral phenomena and ionospheric disturbances. The animation below illustrates the dynamical changes of the global magnetic field in the course of a disturbance: a temporary compression of the magnetosphere by enhanced flow of the solar wind is followed by a tailward stretching of the field lines. Eventually, the increase of the tail magnetic field results in a sudden collapse of the nightside field (a substorm ) and a gradual recovery of the magnetosphere to its pre-storm configuration.
If you have more questions regarding the Earth's magnetosphere and geomagnetism, or would like to refresh your memory of even more general topics, covering basic astronomy and space physics, here is an excellent educational web source, developed by David Stern.
For this reason, understanding the properties of the geospace plasma requires knowing the structure of the geomagnetic field and its dynamics and relation to the state of the solar wind.
Click here to download a GEOPACK source-code library
of FORTRAN subroutines.
A fully revised version
(April 22, 2003) now available.
Includes 19 subroutines for evaluating field vectors, tracing field lines,
transformations between various coordinate systems, and locating the magnetopause
position. Full documentation file:
(Word, 100 KB)
Also available from our anonymous ftp-site .
Click here for downloading a source code (Fortran-77)
of the latest version
(T01_01, Aug.8, 2001) of the inner and near magnetosphere magnetic field model
.
Also available from our
anonymous ftp-site .
See ERRATA for a list of recent corrections/updates
(last correction of T01_01: May 14, 2002).
Click here for downloading a source code (Fortran-77) of the T96 model and a documentation file. Also available from our anonymous ftp-site .
Click here if you need a source code of the 1989 version of the model (T89c). Also available from our anonymous ftp-site .
Click here to view the list of data sets used to derive the models.
Click on highlighted items below for latest developments
Modeling the field of a substorm current wedge.
Magnetotail twisting/warping from GEOTAIL/ISEE data.
Using the divergence-free deformation method in the magnetospheric modeling
Polar Cusp: POLAR MFE data and quantitative modeling
Solar Wind Control of the Tail Lobe Field as Deduced From
Geotail, AMPTE/IRM and ISEE-2
Data
A new data-based model of the near magnetospheric magnetic field with a dawn-dusk
asymmetry:
1. Mathematical structure. JGR-A, v. 107 (A8), 2002,
(PDF 0.9 MB)
2. Parameterization and fitting to observations.
JGR-A, v. 107 (A8), 2002, (PDF 4.1 MB)
Tail plasma sheet models derived from Geotail particle data.
JGR-A, v.108 (A3), 2003. (PDF 1.6MB)
Modeling of the
inner magnetosphere during large storms
JGR-A, v.108 (A5), 2003. (PDF 1.6MB)
Global shape of the magnetotail current sheet as derived from Geotail and Polar data
(JGR-A, v.109(A3), 2004) (PDF 1.2MB)
Author and curator:
Dr. Nikolai Tsyganenko, USRA/NASA/GSFC: Nikolai.Tsyganenko@gsfc.nasa.gov
Mail Code 695,
NASA/Goddard Space Flight Center, Greenbelt, MD 20771
Phone: (301)-286-7925
Fax: (301)-286-1683