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Title: The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons

Abstract

Using the Van Allen Probe in situ measured magnetic field and electron data, we examine the solar wind dynamic pressure and interplanetary magnetic field (IMF) effects on global magnetic field and outer radiation belt relativistic electrons (≥1.8 MeV). The dynamic pressure enhancements (>2 nPa) cause the dayside magnetic field increase and the nightside magnetic field reduction, whereas the large southward IMFs (B z-IMF < –2nT) mainly lead to the decrease of the nightside magnetic field. In the dayside increased magnetic field region (magnetic local time (MLT) ~ 06:00–18:00, and L > 4), the pitch angles of relativistic electrons are mainly pancake distributions with a flux peak around 90° (corresponding anisotropic index A > 0.1), and the higher-energy electrons have stronger pancake distributions (the larger A), suggesting that the compression-induced betatron accelerations enhance the dayside pancake distributions. However, in the nighttime decreased magnetic field region (MLT ~ 18:00–06:00, and L ≥ 5), the pitch angles of relativistic electrons become butterfly distributions with two flux peaks around 45° and 135° (A < 0). The spatial range of the nighttime butterfly distributions is almost independent of the relativistic electron energy, but it depends on the magnetic field day-night asymmetry and the interplanetary conditions.more » The dynamic pressure enhancements can make the nighttime butterfly distribution extend inward. The large southward IMFs can also lead to the azimuthal expansion of the nighttime butterfly distributions. As a result, these variations are consistent with the drift shell splitting and/or magnetopause shadowing effect.« less

Authors:
 [1];  [1];  [1]; ORCiD logo [2];  [3];  [4]
  1. Beihang Univ., Beijing (China)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Univ. of Colorado, Boulder, CO (United States)
  4. Univ. of New Hampshire, Durham, NH (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
National Aeronautic and Space Administration (NASA); USDOE
OSTI Identifier:
1304818
Report Number(s):
LA-UR-16-23137
Journal ID: ISSN 0094-8276
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 43; Journal Issue: 14; Journal ID: ISSN 0094-8276
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Heliospheric and Magnetospheric Physics

Citation Formats

Yu, J., Li, L. Y., Cao, J. B., Reeves, Geoffrey D., Baker, D. N., and Spence, H. The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons. United States: N. p., 2016. Web. doi:10.1002/2016GL069029.
Yu, J., Li, L. Y., Cao, J. B., Reeves, Geoffrey D., Baker, D. N., & Spence, H. The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons. United States. doi:10.1002/2016GL069029.
Yu, J., Li, L. Y., Cao, J. B., Reeves, Geoffrey D., Baker, D. N., and Spence, H. 2016. "The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons". United States. doi:10.1002/2016GL069029. https://www.osti.gov/servlets/purl/1304818.
@article{osti_1304818,
title = {The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons},
author = {Yu, J. and Li, L. Y. and Cao, J. B. and Reeves, Geoffrey D. and Baker, D. N. and Spence, H.},
abstractNote = {Using the Van Allen Probe in situ measured magnetic field and electron data, we examine the solar wind dynamic pressure and interplanetary magnetic field (IMF) effects on global magnetic field and outer radiation belt relativistic electrons (≥1.8 MeV). The dynamic pressure enhancements (>2 nPa) cause the dayside magnetic field increase and the nightside magnetic field reduction, whereas the large southward IMFs (Bz-IMF < –2nT) mainly lead to the decrease of the nightside magnetic field. In the dayside increased magnetic field region (magnetic local time (MLT) ~ 06:00–18:00, and L > 4), the pitch angles of relativistic electrons are mainly pancake distributions with a flux peak around 90° (corresponding anisotropic index A > 0.1), and the higher-energy electrons have stronger pancake distributions (the larger A), suggesting that the compression-induced betatron accelerations enhance the dayside pancake distributions. However, in the nighttime decreased magnetic field region (MLT ~ 18:00–06:00, and L ≥ 5), the pitch angles of relativistic electrons become butterfly distributions with two flux peaks around 45° and 135° (A < 0). The spatial range of the nighttime butterfly distributions is almost independent of the relativistic electron energy, but it depends on the magnetic field day-night asymmetry and the interplanetary conditions. The dynamic pressure enhancements can make the nighttime butterfly distribution extend inward. The large southward IMFs can also lead to the azimuthal expansion of the nighttime butterfly distributions. As a result, these variations are consistent with the drift shell splitting and/or magnetopause shadowing effect.},
doi = {10.1002/2016GL069029},
journal = {Geophysical Research Letters},
number = 14,
volume = 43,
place = {United States},
year = 2016,
month = 7
}

Journal Article:
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Cited by: 4works
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  • The relationship of increases in the intensities of electrons in the outer magnetosphere and large-scale disturbances of the solar wind is studied with measurements of fluxes of energetic (E/sub e/ approx. 1 MeV) electrons made on the satellites Prognoz-6, -7, and Raduga. It is shown that the effect of high-speed solar wind fluxes on the geomagnetosphere involves the acceleration of electrons near the magnetopause and the enhancement of charged-particle transport into the magnetosphere from the boundary.
  • Cited by 7
  • Radiation belt electron flux dropouts are a kind of drastic variation in the Earth's magnetosphere, understanding of which is of both scientific and societal importance. We report multi-satellite simultaneous observations of magnetopause and atmospheric losses of radiation belt electrons during an event of intense solar wind dynamic pressure pulse, using electron flux data from a group of 14 satellites. Moreover, when the pulse occurred, magnetopause and atmospheric loss could take effect concurrently contributing to the electron flux dropout. Losses through the magnetopause were observed to be efficient and significant at L ≳ 5, owing to the magnetopause intrusion into Lmore » ~6 and outward radial diffusion associated with sharp negative gradient in electron phase space density. Losses to the atmosphere were directly identified from the precipitating electron flux observations, for which pitch angle scattering by plasma waves could be mainly responsible. While the convection and substorm injections strongly enhanced the energetic electron fluxes up to hundreds of keV, they could delay other than avoid the occurrence of electron flux dropout at these energies. Finally, we demonstrate that the pulse-time radiation belt electron flux dropout depends strongly on the specific interplanetary and magnetospheric conditions and that losses through the magnetopause and to the atmosphere and enhancements of substorm injection play an essential role in combination, which should be incorporated as a whole into future simulations for comprehending the nature of radiation belt electron flux dropouts.« less
  • The variability of hourly values of solar wind number density, number density variation, speed, speed variation and dynamic pressure with IMF B{sub z} and magnitude {vert bar}B{vert bar} has been examined for the period 1965-1986. The authors wish to draw attention to a strong correlation in number density and number density fluctuation with IMF B{sub z} characterized by a symmetric increasing trend in these quantities away from B{sub z} = O nT. The fluctuation level in solar wind speed is found to be relatively independent of B{sub z}. They infer that number density and number density variability dominate in controllingmore » solar wind dynamic pressure and dynamic pressure variability. It is also found that dynamic pressure is correlated with each component of IMF and that there is evidence of morphological differences between the variation with each component. Finally, they examine the variation of number density, speed, dynamic pressure and fluctuation level in number density and speed with IMF magnitude {vert bar}B{vert bar}. Again they find that number density variation dominates over solar wind speed in controlling dynamic pressure.« less
  • The authors report a study of relationships between the behavior of aurorae in the cusp/cleft region and variations in the solar wind pressure, and B{sub z} and B{sub y} components of the interplanetary magnetic field. Here the authors examine a time sequence of data which reveals substantial variations in the solar wind and IMF data. In particular they look at correlations to observed latitudinal shifts in the location of the aurorae, and in addition, longitudinal shifts, either east of westward dependent upon the polarity of B{sub y}.