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A simple model of complex cusp ion dispersions during intervals of northward interplanetary magnetic field
Author(s) -
Topliss S. M.,
Owen C. J.,
Peterson W. K.
Publication year - 2000
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 - 10.1029/2000gl000123
Subject(s) - magnetosheath , magnetopause , field line , cusp (singularity) , physics , geophysics , latitude , interplanetary magnetic field , dispersion (optics) , computational physics , magnetosphere , atmospheric sciences , magnetic field , geology , astrophysics , solar wind , geometry , astronomy , quantum mechanics , mathematics , optics
During northward IMF intervals, cusp ion energy‐latitude dispersions observed by POLAR's TIMAS instrument often have two components. One dispersion decreases in energy with decreasing latitude. The second appears to split from the first and increases in energy as the equatorward edge of the cusp is approached. We present a simple model representing particle entry resulting from reconnection poleward of the cusp. We qualitatively show that split dispersions may arise on reconnected field lines which accelerate as they contract sunward into regions of lower magnetosheath flow velocity. The velocity filter effect produces the first dispersion by spreading particles entering near the reconnection site across a range of latitudes. The second, increasing energy dispersion, results from particles crossing the magnetopause at later times and lower latitudes. These particles are accelerated to higher energies due to the increased contraction speed of reconnected field lines at these latitudes.