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Hourly variances of fluctuations in the heliospheric magnetic field out of the ecliptic plane
Author(s) -
Forsyth R. J.,
Horbury T. S.,
Balogh A.,
Smith E. J.
Publication year - 1996
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 - 10.1029/96gl00416
Subject(s) - ecliptic , physics , coronal hole , solar wind , coronal mass ejection , polar , solar rotation , population , heliospheric current sheet , heliosphere , range (aeronautics) , wkb approximation , astrophysics , latitude , magnetic field , astronomy , solar physics , demography , materials science , quantum mechanics , sociology , composite material
Magnetic field fluctuations at high heliographic latitudes are discussed in terms of the latitude and radial dependence of their variances, as observed by the Ulysses spacecraft. The increased level of transverse fluctuations in fast solar wind flows from the polar coronal holes is similar to that found in high speed streams near the ecliptic. However, continuous observations in the fast solar wind both southward and northward of the solar equatorial plane has allowed the determination of the radial dependence of fluctuations on hourly and shorter timescales, free from additional energy input from stream‐stream interactions or from coronal mass ejections and in the presence of a slowly evolving, low frequency Alfvénic population. The conclusion is that fluctuations in the inertial range in the homogeneous polar coronal flows decay faster than predicted by the WKB approximation. However, even minor compression effects can increase the energy in these fluctuations.