Open AccessMagnetic field depressions in the solar wind
Author(s) -
Fränz M.,
Burgess D.,
Horbury T. S.
Publication year - 2000
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2000ja900026
Subject(s) - solar wind , magnetic field , interplanetary magnetic field , dipole model of the earth's magnetic field , classification of discontinuities , physics , geophysics , mercury's magnetic field , computational physics , anisotropy , log normal distribution , interplanetary spaceflight , heliosphere , field strength , geology , optics , mathematics , statistics , mathematical analysis , quantum mechanics
Depressions in the interplanetary magnetic field strength occur on a wide range of temporal scales, starting with magnetic holes with a duration of several seconds and extending to larger‐scale structures of more than 30 min duration. Using the magnetic field measurements of the Ulysses spacecraft, we quantify the statistical significance of the occurrence rate of depressions in the magnetic field compared to a lognormal distribution. On this basis we introduce measures for the length and depth of magnetic depressions. There is a weak indication for a change in the character of the length distribution at 20–40 s in the high‐speed solar wind. An analysis of 115 depressions with a length > 2 min showed that (1) they are bounded by tangential discontinuities in 78% of all cases, (2) normals to the structure boundaries have no strong orientation with respect to background field or global geometry, and (3) an increased proton temperature anisotropy is the only bulk ion parameter correlating with the depressions.