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Steady‐state event‐excluded proton spectra at solar minimum at all heliolatitudes
Author(s) -
Patterson J. D.,
Armstrong T. P.
Publication year - 2003
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 - 10.1029/2003gl017154
Subject(s) - heliosphere , physics , spectral line , energetic neutral atom , population , proton , solar energetic particles , range (aeronautics) , astrophysics , solar minimum , interplanetary medium , spacecraft , astronomy , solar wind , coronal mass ejection , solar cycle , electron , nuclear physics , interplanetary spaceflight , plasma , demography , materials science , sociology , composite material
We present spectra of a steady foreground population of particles in the inner heliosphere observed by the Heliosphere Instrument for Spectra, Composition, and Anisotopy at Low Energies (HISCALE) on board the Ulysses spacecraft. The observed spectra come from the full range of heliolatitudes visited by Ulysses, −80 to +80 degrees, during Ulysses' first full orbit of the Sun during solar minimum. New corrections for background were applied resulting in a more sensitive and higher energy resolution data set that we used here to analyze quiet‐time (event‐excluded) spectra. We found a persistent foreground population of energetic protons that permeate the inner heliosphere. These protons have complex energy spectra suggesting multiple acceleration sources, and these particles move predominently in non‐radial directions. These findings support the idea that the inner heliosphere acts as a reservoir for energetic protons.