Premium
Ion‐Scale Spectral Break in the Normal Plasma Beta Range in the Solar Wind Turbulence
Author(s) -
Wang X.,
Tu C.Y.,
He J.S.,
Wang L.H.
Publication year - 2018
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2017ja024813
Subject(s) - solar wind , physics , gyroradius , turbulence , beta (programming language) , plasma , proton , astrophysics , atomic physics , computational physics , meteorology , nuclear physics , computer science , programming language
The spectral break ( f b ) of magnetic fluctuations at the ion scale in the solar wind is considered to give important clue on the turbulence dissipation mechanism. Among several possible mechanisms, the most notable two are related respectively to proton thermal gyroradius ρ i and proton inertial length d i . The corresponding frequencies of them are f ρ i = V SW /(2 π ρ i ) and f d i = V SW /(2 π d i ), respectively, where V SW is the solar wind speed. However, no definite conclusion has been given for which one is more reasonable because the two parameters have similar value when plasma beta β ∼ 1. Here we do a statistical study to see if the two ratios f b / f ρ i and f b / f d i have different dependence on β in the solar wind turbulence with 0.1 < β < 1.3. From magnetic measurements by the Wind spacecraft, we select 141 data sets with each one longer than 13 h. We find that the ratio f b / f d i is statistically not dependent on β , and the average value of it is 0.48 ± 0.06. However, f b / f ρ i increases with increasing β clearly and is significantly smaller than f b / f d i when β < 0.8. These new results show that f b is statistically 0.48 f d i , and the influence of β could be negligible in the studied β range. It indicates a preference of the dissipation mechanism associated with d i in the solar wind with 0.1 < β < 0.8. Further theoretical studies are needed to give detailed explanation.