The Radial Dependence of Proton-scale Magnetic Spectral Break in Slow Solar Wind during PSP Encounter 2 - Archive ouverte HAL Access content directly
Journal Articles The Astrophysical Journal Supplement Year : 2020

The Radial Dependence of Proton-scale Magnetic Spectral Break in Slow Solar Wind during PSP Encounter 2

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Jiansen He
Daniel Vech
  • Function : Author
J. Kasper
Marc Pulupa
John Bonnell
Anthony Case
Keith Goetz
Peter Harvey
Kelly Korreck
Davin Larson
Roberto Livi
Robert Macdowall
David Malaspina
Michael Stevens
Phyllis Whittlesey

Abstract

Magnetic field fluctuations in the solar wind are commonly observed to follow a power-law spectrum. Near proton-kinetic scales, a spectral break occurs that is commonly interpreted as a transition to kinetic turbulence. However, this transition is not yet entirely understood. By studying the scaling of the break with various plasma properties, it may be possible to constrain the processes leading to the onset of kinetic turbulence. Using data from the Parker Solar Probe, we measure the proton-scale break over a range of heliocentric distances, enabling a measurement of the transition from inertial to kinetic-scale turbulence under various plasma conditions. We find that the break frequency f(b) increases as the heliocentric distance r decreases in the slow solar wind following a power law of f(b) similar to r(-1.11). We also compare this to the characteristic plasma ion scales to relate the break to the possible physical mechanisms occurring at this scale. The ratio f(b)/f(c) (f(c) for Doppler-shifted ion cyclotron resonance scale) is close to unity and almost independent of plasma beta(p). While f(b)/f(p) (f(p) for Doppler-shifted proton thermal gyroradius) increases with beta(p) approaching to unity at larger beta(p), f(b)/f(d) (f(d) for Doppler-shifted proton inertial length) decreases with beta(p) from unity at small beta(p). Due to the large comparable Alfven and solar wind speeds, we analyze these results using both the standard and modified Taylor hypotheses, demonstrating the robust statistical results.

Dates and versions

insu-02937840 , version 1 (14-09-2020)

Identifiers

Cite

Die Duan, Trevor Bowen, Christopher Chen, Alfred Mallet, Jiansen He, et al.. The Radial Dependence of Proton-scale Magnetic Spectral Break in Slow Solar Wind during PSP Encounter 2. The Astrophysical Journal Supplement, 2020, 246 (2), pp.55. ⟨10.3847/1538-4365/ab672d⟩. ⟨insu-02937840⟩
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