The coupling between the solar wind and proton fluxes at GEO

R J Boynton,S A Billings,O A Amariutei,I Moiseenko

doi:10.5194/angeo-31-1631-2013

R J Boynton, S A Billings + Show 2 more

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https://doi.org/10.5194/angeo-31-1631-2013

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Abstract

Abstract. The relationship between the solar wind and the proton flux at geosynchronous Earth orbit (GEO) is investigated using the error reduction ratio (ERR) analysis. The ERR analysis is able to search for the most appropriate inputs that control the evolution of the system. This approach is a black box method and is able to derive a mathematical model of a system from input-output data. This method is used to analyse eight energy ranges of the proton flux at GEO from 80 keV to 14.5 MeV. The inputs to the algorithm were solar wind velocity, density and pressure; the Dst index; the solar energetic proton (SEP) flux; and a function of the interplanetary magnetic field (IMF) tangential magnitude and clock angle. The results show that for lowest five energy channels (80 to 800 keV) the GEO proton fluxes are controlled by the solar wind velocity with a lag of two to three days. However, above 350 keV, the SEP fluxes, accounts for a significant portion of the GEO proton flux variance. For the highest three energy channels (0.74 to 14.5 MeV), the SEPs account for the majority of the ERR. The results also show an anisotropy of protons with gyrocenters inside GEO and outside GEO, where the protons inside GEO are controlled partly by the Dst index and also an IMF-clock angle function.

Highlights

The Van Allen radiation belts, first discovered by Explorer I (van Allen, 1958), are regions of the magnetosphere that are inhabited by highly energetic particles trapped by the Earth’s magnetic field
Paulikas and Blake (1969) pointed out that these < 20 MeV protons mainly occurred in the nightside sector and concluded that the access of the 5–21 MeV protons is governed by the structure and fluctuations in the magnetic field well outside the geosynchronous Earth orbit (GEO)
Observations on polar orbiting satellites have shown that the access of > 1 MeV solar protons to lower L-shells is correlated with Dst, AE and dynamic pressure (Ivanova et al, 1985). storm sudden commencements (SSCs) associated with coronal mass ejections (CMEs) are known to inject the > 10 MeV protons into the magnetosphere (Vampola and Korth, 1992; Blake et al, 1992; Li et al, 1993; Hudson et al, 1995)

Summary

Introduction

The Van Allen radiation belts, first discovered by Explorer I (van Allen, 1958), are regions of the magnetosphere that are inhabited by highly energetic particles trapped by the Earth’s magnetic field. These trapped particles can significantly increase the probability of detrimental effects to the onboard satellite systems and can even lead to permanent hardware damage (Roeder and Fennell, 2009). Paulikas and Blake (1969), using data from GEO satellite ATS 1 and measurements from outside the magnetosphere, showed that during magnetically quiet times, protons with energies > 20 MeV have free access to the geosynchronous regions of the magnetosphere as the theory suggested. Observations on polar orbiting satellites have shown that the access of > 1 MeV solar protons to lower L-shells is correlated with Dst, AE and dynamic pressure (Ivanova et al, 1985). storm sudden commencements (SSCs) associated with coronal mass ejections (CMEs) are known to inject the > 10 MeV protons into the magnetosphere (Vampola and Korth, 1992; Blake et al, 1992; Li et al, 1993; Hudson et al, 1995). Richard et al (2002) studied the importance

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