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The inner magnetosphere ion composition and local time distribution over a solar cycle
Author(s) -
Kistler L. M.,
Mouikis C. G.
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2015ja021883
Subject(s) - magnetosphere , physics , solar wind , earth's magnetic field , flux (metallurgy) , range (aeronautics) , local time , solar cycle , ion , atomic physics , astrophysics , atmospheric sciences , plasma , computational physics , chemistry , magnetic field , materials science , quantum mechanics , statistics , organic chemistry , mathematics , composite material
Using the Cluster/Composition and Distribution Function (CODIF) analyzer data set from 2001 to 2013, a full solar cycle, we determine the ion distributions for H + , He + , and O + in the inner magnetosphere (L < 12) over the energy range 40 eV to 40 keV as a function magnetic local time, solar EUV ( F 10.7 ), and geomagnetic activity ( Kp ). Concentrating on L = 6–7 for comparison with previous studies at geosynchronous orbit, we determine both the average flux at 90° pitch angle and the pitch angle anisotropy as a function of energy and magnetic local time. We clearly see the minimum in the H + spectrum that results from the competition between eastward and westward drifts. The feature is weaker in O + and He + , leading to higher O + /H + and He + /H + ratios in the affected region, and also to a higher pitch angle anisotropy, both features expected from the long‐term effects of charge exchange. We also determine how the nightside L = 6–7 densities and temperatures vary with geomagnetic activity ( Kp ) and solar EUV ( F 10.7 ). Consistent with other studies, we find that the O + density and relative abundance increase significantly with both Kp and F 10.7 . He + density increases with F 10.7 , but not significantly with Kp . The temperatures of all species decrease with increasing F 10.7 . The O + and He + densities increase from L = 12 to L ~ 3–4, both absolutely and relative to H + , and then drop off sharply. The results give a comprehensive view of the inner magnetosphere using a contiguous long‐term data set that supports much of the earlier work from GEOS, ISEE, Active Magnetospheric Particle Tracer Explorers, and Polar from previous solar cycles.