Premium
Evolution of the solar wind proton temperature anisotropy from 0.3 to 2.5 AU
Author(s) -
Matteini Lorenzo,
Landi Simone,
Hellinger Petr,
Pantellini Filippo,
Maksimovic Milan,
Velli Marco,
Goldstein Bruce E.,
Marsch Eckart
Publication year - 2007
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 - 10.1029/2007gl030920
Subject(s) - anisotropy , physics , solar wind , proton , instability , trajectory , space (punctuation) , parameter space , path (computing) , beta (programming language) , computational physics , astrophysics , geometry , mechanics , nuclear physics , optics , computer science , mathematics , plasma , astronomy , programming language , operating system
We report an analysis of the proton temperature anisotropy evolution from 0.3 to 2.5 AU based on the Helios and Ulysses observations. With increasing distance the fast wind data show a path in the parameter space ( β ∥ p , T ⊥ p / T ∥ p ). The first part of the trajectory is well described by an anticorrelation between the temperature anisotropy T ⊥ p / T ∥ p and the proton parallel beta, while after 1 AU the evolution with distance in the parameter space changes and the data result in agreement with the constraints derived by a fire hose instability. The slow wind data show a more irregular behavior, and in general it is not possible to recover a single evolution path. However, on small temporal scale we find that different slow streams populate different regions of the parameter space, and this suggests that when considering single streams also the slow wind follows some possible evolution path.