Ion‐scale spectral break of solar wind turbulence at high and low beta. Issue 22 (25th November 2014)

• Record Type: Journal Article
• Authors: Chen, C. H. K.; Leung, L.; Boldyrev, S.; Maruca, B. A.; Bale, S. D.
• Is Part Of: Geophysical research letters. Volume 41:Issue 22(2014:Nov.)
• Page Start: 8081
• Page End: 8088
• Publication Date: 2014-11-25
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2014GL062009
• Languages: English
• ISSNs: 0094-8276

Abstract

<abstract abstract-type="main" id="grl52226-abs-0001"> <title>Abstract</title> <p id="grl52226-para-0001">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 gyroradius <italic>ρ</italic><sub>i</sub> and proton inertial length <italic>d</italic><sub>i</sub>. At 1 AU it is difficult to determine which of these is associated with the break, since <inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgh31vh5t15" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:grl:media:grl52226:grl52226-math-0001" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>d</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">i</mml:mi></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:msub><mml:mrow><mml:mi>ρ</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">i</mml:mi></mml:mrow></mml:msub><mml:mo>/</mml:mo><mml:msqrt><mml:mrow><mml:msub><mml:mrow><mml:mi>β</mml:mi></mml:mrow><mml:mrow><mml:mstyle mathvariant="normal"><mml:mo>⊥</mml:mo><mml:mi>i</mml:mi></mml:mstyle></mml:mrow></mml:msub></mml:mrow></mml:msqrt></mml:math></alternatives></inline-formula> and the perpendicular ion plasma beta is typically <italic>β</italic><sub>⊥i</sub>∼1. To address this, several exceptional intervals with <italic>β</italic><sub>⊥i</sub>≪1 and <italic>β</italic><sub>⊥i</sub>≫1 were investigated, during which these scales were well separated. It was found that for <italic>β</italic><sub>⊥i</sub>≪1 the break occurs at <italic>d</italic><sub>i</sub> and for <italic>β</italic><sub>⊥i</sub>≫1 at <italic>ρ</italic><sub>i</sub>, i.e., the larger of the two scales. Possible explanations for these results are discussed, including Alfvén wave dispersion, damping, and current sheets.</p> </abstract>