Magnetic Field at Geosynchronous Altitude
The magnetic field data shown in this site are from the ETS-VIII geosynchronous satellite launched by Japan Aerospace Exploration Agency (JAXA) on December 18, 2006.
The ETS-VIII satellite is placed at r=6.6 RE and geographic longitude of 146°E.
The magnetic field at geosynchronous altitude is stretched before substorm onset, while the field becomes dipole-like when substorm occurs. Thus the magnetic field at geosynchronous altitude increases at substorm onset. It should be noted that this magnetic field changes can be found preferentially when the satellite was on the nightside. In the plot, local midnight and local noon are indicated with filled circle and open circle, respectively.
Details on the ETS-VIII satellite can be found at WWW page of JAXA (http://www.jaxa.jp/projects/sat/ets8/index_e.html).