Case study of nightside magnetospheric magnetic field response to interplanetary shocks

• Published in: Journal of Geophysical Research: Space Physics 2010-10, Vol.115 (A10), p.n/a
• Main Authors: Wang, C., Sun, T. R., Guo, X. C., Richardson, J. D.
• Format: Article
• Language: English
• Subjects: Atmospheric sciences; Case studies; Earth sciences; Earth, ocean, space; Exact sciences and technology; geosynchronous response; IP shocks; Magnetic fields; Magnetism; MHD simulation; Spacecraft
• ISSN: 0148-0227; 2169-9380; 2156-2202; 2169-9402
• DOI: 10.1029/2010JA015451

Observations show that the geosynchronous magnetic field in midnight sector sometimes decreases when an interplanetary (IP) fast forward shock (FFS) passes Earth, even though the magnetosphere is always compressed. We perform case studies of the response observed by the GOES spacecraft at geosynchronous orbit near midnight to two IP shocks passing Earth. One shock produces a decrease in BZ (a negative response) and the other an increase in BZ (a positive response). A global 3D MHD code is run to reproduce the responses at geosynchronous orbit, and to further provide information on the initiation and development of BZ variations in the entire magnetosphere. The model reveals that when a FFS sweeps over the magnetosphere, there exist mainly two regions, a positive response region caused by the compressive effect of the shock and a negative response region which is probably associated with the temporary enhancement of earthward convection in the nightside magnetosphere. The spacecraft may observe an increase or decrease of the magnetic field depending on which region it is in. The numerical results reproduce the main characters of the geosynchronous magnetic field response to IP shocks for these two typical cases.