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Relationship between energetic particles and plasmas in the distant plasma sheet
Author(s) -
Sarris E. T.,
Krimigis S. M.,
Lui A. T. Y.,
Ackerson K. L.,
Frank L. A.,
Williams D. J.
Publication year - 1981
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl008i004p00349
Subject(s) - plasma , plasma sheet , atomic physics , ion , spectral line , physics , range (aeronautics) , materials science , nuclear physics , magnetosphere , quantum mechanics , astronomy , composite material
Measurements of ions from three different instruments on the IMP‐7 and 8 spacecraft are combined to yield the differential energy spectra of ions over the entire energy range of ∼ 100 eV to 4 MeV in the earth’s distant (∼ 30 to ∼ 40 R e ) plasma sheet. These spectra, obtained during times of relatively small bulk flow velocities, span the intensity range from ∼ 10 −5 to 10 5 (cm²sec sr keV) −1 , varying smoothly over the entire energy range both when the plasma is cold (∼ 1 keV) and hot (∼ 9 keV). Overall, the shape of the spectrum resembles a Maxwellian but with a high energy (≳ 50 keV) tail described well by a power law (⧜E −γ ). The high energy tail is displaced in a parallel fashion to higher or lower intensities when the plasma is hot or cold, respectively. The transition between the Maxwellian and the power law occurs at E ≃ (γ + 1)kT. It is found that the energetic particle populations in the plasma sheet appear to be directly related to the mean thermal energies of the corresponding plasmas.