The quiet geomagnetic field at geosynchronous orbit and its dependence on solar wind dynamic pressure

Rufenach, C. L.; McPherron, R. L.; Schaper, Justin

doi:10.1029/91ja02135

Cited by 52 publications

(40 citation statements)

References 16 publications

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“…This correlation arises from the earthward displacement and intensification of both the magnetopause and tail current, which increases the noon-midnight asymmetry of equatorial magnetic field (see e.g. the analysis of the magnetic field at 6.6 R e made by Rufenach et al (1992).…”

Section: Discussionmentioning

confidence: 99%

Statistical study of the proton isotropy boundary

2005

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Abstract. Based on a large data set of polar NOAA-type satellite observations we studied the latitude-MLT shape of the 80 keV proton isotropy boundary (IB) as a function of the solar wind parameters and magnetic activity. Using "snapshots" of isotropy boundaries near-simultaneously crossed at four points we found that its equatorward expansion, as well as its dawn-dusk shift, depends mostly on the AEindex and on the corrected D st *, whereas the amplitude of the IB daily variation is mostly controlled by the solar wind dynamic pressure. Applying a nonlinear, multi-parametric, least-square regression procedure, the empirical relationship describing the IB latitude as a function of MLT and AE, Pd, D st * parameters was obtained. Comparing it with the predictions from the Tsyganenko-2001 model we found a good agreement during the quiet time but some important differences during the disturbed periods. Interpretation of these results in terms of the properties of the magnetospheric configuration is briefly discussed.

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Section: Discussionmentioning

confidence: 99%

Statistical study of the proton isotropy boundary

2005

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“…Both their work and the work by Kokubun [1993] showed that, at geosynchronous orbit, sudden impulses had very little effect near midnight. Also, Rufenach et al [1992] studied the hourly quiet field values at geosynchronous orbit using GOES spacecraft data and found that the quiet magnetic field H component was stronger for higher solar wind dynamic pressure. Another study on quiet time geosynchronous magnetic field variability was recently done by Sanny et al [2002].…”

Section: Introductionmentioning

confidence: 99%

Geosynchronous magnetic field response to solar wind dynamic pressure pulse

Lee

Lyons

2004

J. Geophys. Res.

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We present a study of the response of the geosynchronous magnetic field to abrupt enhancements of the solar wind dynamic pressure. Results are obtained separately for cases of northward and southward interplanetary magnetic field (IMF) prior to and after the solar wind pressure jump. For pressure enhancements with southward IMF we find that the response of the geosynchronous magnetic field on the dayside is mostly compression. However, on the nightside it can be a dipolarization‐like change that is similar to that which occurs during substorms. We report four events showing the dipolarization‐like response on the nightside. Analysis using low‐latitude geomagnetic data as well as the geosynchronous energetic particle flux data leads us to argue that this dipolarization is part of the global disturbance directly driven by the solar wind pressure enhancement. We also find that the nightside magnetosphere is remarkably sensitive to small solar wind dynamic pressure enhancements when the IMF is strongly southward (i.e., Bz is below ∼−10 nT). For northward IMF, solar wind pressure enhancements generally lead to magnetic compression, with a few cases of depression on the nightside, neither of which is a dipolarization‐like response. The compression is strongest near noon, decreases toward dawn and dusk, and increases with the amount of increase in dynamic pressure.

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“…Increases in the solar wind dynamic pressure compress the magnetopause and enhance dayside magnetospheric magnetic field strengths but depress nightside geosynchronous magnetic field strengths [e.g., Rufenach et al, 1992]. A small fraction of the dawn/dusk IMF component "penetrates" to geosynchronous orbit [e.g., Cowley and Hughes, 1983; Nagai,nent of the dayside magnetospheric magnetic field [e.g., Maltsev and Lyatsky, 1975;Tsyganenko and Sibeck, 1994] but make oppositely directed contributions to the z component on the nightside.…”

Section: Introductionmentioning

confidence: 99%