On energetic electrons (>38 keV) in the central plasma sheet: Data analysis and modeling

The spatial distribution of >38 keV electron fluxes in the central plasma sheet (CPS) and the statistical relationship between the CPS electron fluxes and the upstream solar wind and interplanetary magnetic field (IMF) parameters are investigated quantitatively using measurements from the Geotail satellite (1998-2004) at geocentric radial distances of 9-30 RE in the night side. The measured electron fluxes increase with closer distance to the center of the neutral sheet, and exhibit clear dawn-dusk asymmetry, with the lowest fluxes at the dusk side and increasing toward the dawn side. The asymmetry persists along the Earth's magnetotail region (at least to Geotail's apogee of 30 RE during the period of interest). Both the individual case and the statistical analysis on the relationship between >38 keV CPS electron fluxes and solar wind and IMF properties show that larger (smaller) solar wind speed and southward (northward) IMF B(z) imposed on the magnetopause result in higher (lower) energetic electron fluxes in the CPS with a time delay of about 1 hour, while the influence of solar wind ion density on the energetic electrons fluxes is insignificant. Interestingly, the energetic electron fluxes at a given radial distance correlate better with IMF B(z) than with the solar wind speed. Based on these statistical analyses, an empirical model is developed for the first time to describe the 2-D distribution (along and across the Earth's magnetotail) of the energetic electron fluxes (>38 keV) in the CPS, as a function of the upstream solar wind and IMF parameters. The model reproduces the observed energetic electron fluxes well, with a correlation coefficient R equal to 0.86. Taking advantage of the time delay, full spatial distribution of energetic electron fluxes in the CPS can be predicted about 2 hours in advance using the real-time solar wind and IMF measurements at the L1 point: 1 hour for the solar wind to propagate to the magnetopause and a 1 hour delay for the best correlation. Such a prediction helps us to determine whether there are enough electrons in the CPS available to be transported inward to enhance the outer electron radiation belt.

[1]  D. Baker,et al.  Cluster observations of energetic electron flux variations within the plasma sheet , 2009 .

[2]  D. Baker,et al.  Energetic plasma sheet electrons and their relationship with the solar wind: A Cluster and Geotail study , 2009 .

[3]  Yue Chen,et al.  Storm-dependent radiation belt electron dynamics , 2009 .

[4]  T. Mukai,et al.  The dawn‐dusk asymmetry of energetic electron in the Earth's magnetotail: Observation and transport models , 2008 .

[5]  A. Sharma,et al.  Transient and localized processes in the magnetotail: a review , 2008 .

[6]  B. Lavraud,et al.  Statistical properties of tail plasma sheet electrons above 40 keV , 2008 .

[7]  J. Weygand,et al.  Sources, transport, and distributions of plasma sheet ions and electrons and dependences on interplanetary parameters under northward interplanetary magnetic field , 2007 .

[8]  Xinlin Li,et al.  Prediction of the AL index using solar wind parameters , 2007 .

[9]  S. Mühlbachler,et al.  Energetic electron acceleration in the downstream reconnection outflow region , 2007 .

[10]  M. Fujimoto,et al.  Timescale for the formation of the cold‐dense plasma sheet: A case study , 2006 .

[11]  J. Weygand,et al.  Equatorial distributions of the plasma sheet ions, their electric and magnetic drifts, and magnetic fields under different interplanetary magnetic field Bz conditions , 2006 .

[12]  Yue Chen,et al.  Multisatellite determination of the relativistic electron phase space density at geosynchronous orbit: Methodology and results during geomagnetically quiet times , 2005 .

[13]  M. Fujimoto,et al.  Solar wind control of the radial distance of the magnetic reconnection site in the magnetotail , 2005 .

[14]  S. Wing,et al.  Dawn‐dusk asymmetries, ion spectra, and sources in the northward interplanetary magnetic field plasma sheet , 2005 .

[15]  Robert L. McPherron,et al.  A new interpretation of Weimer et al.'s solar wind propagation delay technique , 2005 .

[16]  D. Baker,et al.  Physical models of the geospace radiation environment , 2004 .

[17]  M. Dunlop,et al.  Multisatellite measurements of electron phase space density gradients in the Earth's inner and outer magnetosphere , 2004 .

[18]  Xinlin Li Variations of 0.7–6.0 MeV electrons at geosynchronous orbit as a function of solar wind , 2004 .

[19]  M. Fujimoto,et al.  Spatial and Temporal Variations of the Cold Dense Plasma Sheet: Evidence for a Low‐Latitude Boundary Layer Source? , 2013 .

[20]  J. Borovsky,et al.  Delivery of cold, dense plasma sheet material into the near‐Earth region , 2003 .

[21]  T. Mukai,et al.  Tail plasma sheet models derived from Geotail particle data , 2003 .

[22]  D. Mccomas,et al.  Predicting interplanetary magnetic field (IMF) propagation delay times using the minimum variance technique , 2003 .

[23]  S. Bale,et al.  Evidence for Electron Acceleration up to ~300 keV in the Magnetic Reconnection Diffusion Region of the Earth's Magnetotail , 2002 .

[24]  S. Bale,et al.  Evidence for electron acceleration up to approximately 300 keV in the magnetic reconnection diffusion region of earth's magnetotail. , 2002, Physical review letters.

[25]  S. Wing,et al.  2D plasma sheet ion density and temperature profiles for northward and southward IMF , 2002 .

[26]  E. Sarris,et al.  The dawn-dusk plasma sheet asymmetry of energetic particles: An Interball perspective , 2001 .

[27]  Daniel N. Baker,et al.  Quantitative prediction of radiation belt electrons at geostationary orbit based on solar wind measurements , 2001 .

[28]  Xinlin Li,et al.  The Electron Radiation Belt , 2001 .

[29]  Eos Sorce,et al.  Laboratory for Atmospheric and Space Physics , 2000 .

[30]  J. Borovsky,et al.  Plasma sheet access to geosynchronous orbit , 1999 .

[31]  J. W. Griffee,et al.  Solar Wind Electron Proton Alpha Monitor (SWEPAM) for the Advanced Composition Explorer , 1998 .

[32]  D. Baker,et al.  Simulation of dispersionless injections and drift echoes of energetic electrons associated with substorms , 1998 .

[33]  R. Elphic,et al.  The transport of plasma sheet material from the distant tail to geosynchronous orbit , 1998 .

[34]  Norman F. Ness,et al.  The ACE Magnetic Fields Experiment , 1998 .

[35]  D. Baker,et al.  Strong electron acceleration in the Earth's magnetosphere , 1998 .

[36]  M. Fujimoto,et al.  Solar wind control of density and temperature in the near‐Earth plasma sheet: WIND/GEOTAIL collaboration , 1997 .

[37]  Daniel N. Baker,et al.  Neutral line model of substorms: Past results and present view , 1996 .

[38]  T. Mukai,et al.  Magnetotail Convection in Geomagnetically Active Times 1. Distance to the Neutral Lines , 1996 .

[39]  Richard W. McEntire,et al.  Geotail energetic particles and ion composition instrument , 1994 .

[40]  W. R. Paterson,et al.  The Comprehensive Plasma Instrumentation(CPI) for the GEOTAIL Spacecraft. , 1994 .

[41]  Hideaki Kawano,et al.  The GEOTAIL Magnetic Field Experiment. , 1994 .

[42]  R. Xu Dynamics of the neutral sheet in the magnetotail during substorm. , 1992 .

[43]  R. McPherron,et al.  7 – Physical Processes Producing Magnetospheric Substorms and Magnetic Storms , 1991 .

[44]  R. A. Mewaldt,et al.  The Advanced Composition Explorer , 1988 .

[45]  David G. Sibeck,et al.  An ISEE 3 study of average and substorm conditions in the distant magnetotail , 1985 .

[46]  E. W. Hones,et al.  Evolution of the Earth's distant magnetotail: ISEE 3 electron plasma results , 1984 .

[47]  S. Krimigis,et al.  Spatial distribution of energetic particles in the distant magnetotail , 1981 .

[48]  E. W. Hones Transient phenomena in the magnetotail and their relation to substorms , 1979 .

[49]  C. Russell,et al.  The magnetotail and substorms , 1973 .

[50]  R. Walker,et al.  Spatial distribution of energetic plasma sheet electrons. , 1972 .

[51]  E. W. Hones,et al.  Characteristics of the plasma sheet in the Earth's magnetotail , 1967 .