title: Ion-scale spectral break of solar wind turbulence at high and low beta.
abstract: The power spectrum of magnetic fluctuations in the solar wind at 1 AU displays a break between two power laws in the range of spacecraft-frame frequencies 0.1 to 1 Hz. These frequencies correspond to spatial scales in the plasma frame near the proton gyroradiusρiand proton inertial lengthdi. At 1 AU it is difficult to determine which of these is associated with the break, since [Formula: see text] and the perpendicular ion plasma beta is typicallyβ⊥i∼1. To address this, several exceptional intervals withβ⊥i≪1 andβ⊥i≫1 were investigated, during which these scales were well separated. It was found that forβ⊥i≪1 the break occurs atdiand forβ⊥i≫1 atρi, i.e., the larger of the two scales. Possible explanations for these results are discussed, including Alfvén wave dispersion, damping, and current sheets.
authors.affiliation: Department of Physics, Imperial College London London, UK ; Space Sciences Laboratory, University of California Berkeley, California, USA.
authors.forename: C H K
authors.initials: CH
authors.lastname: Chen
authors.affiliation: Space Sciences Laboratory, University of California Berkeley, California, USA.
authors.forename: L
authors.initials: L
authors.lastname: Leung
authors.affiliation: Department of Physics, University of Wisconsin-Madison Madison, Wisconsin, USA.
authors.forename: S
authors.initials: S
authors.lastname: Boldyrev
authors.affiliation: Space Sciences Laboratory, University of California Berkeley, California, USA.
authors.forename: B A
authors.initials: BA
authors.lastname: Maruca
authors.affiliation: Space Sciences Laboratory, University of California Berkeley, California, USA ; Department of Physics, University of California Berkeley, California, USA.
authors.forename: S D
authors.initials: SD
authors.lastname: Bale