Statistical Analysis of Magnetic Field Fluctuations in Coronal Mass Ejection-Driven Sheath Regions

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http://hdl.handle.net/10138/328222

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Kilpua , E , Good , S , Ala-Lahti , M , Osmane , A , Fontaine , D , Hadid , L , Janvier , M & Yordanova , E 2021 , ' Statistical Analysis of Magnetic Field Fluctuations in Coronal Mass Ejection-Driven Sheath Regions ' , Frontiers in Astronomy and Space Sciences , vol. 7 , no. 109 , 610278 . https://doi.org/10.3389/fspas.2020.610278

Title: Statistical Analysis of Magnetic Field Fluctuations in Coronal Mass Ejection-Driven Sheath Regions
Author: Kilpua, Emilia; Good, Simon; Ala-Lahti, Matti; Osmane, Adnane; Fontaine, D.; Hadid, L.; Janvier, M.; Yordanova, E.
Contributor: University of Helsinki, Space Physics Research Group
University of Helsinki, Particle Physics and Astrophysics
University of Helsinki, Particle Physics and Astrophysics
University of Helsinki, Space Physics Research Group
Date: 2021-02-04
Language: eng
Number of pages: 17
Belongs to series: Frontiers in Astronomy and Space Sciences
ISSN: 2296-987X
URI: http://hdl.handle.net/10138/328222
Abstract: We report a statistical analysis of magnetic field fluctuations in 79 coronal mass ejection(CME-) driven sheath regions that were observed in the near-Earth solar wind. Wind highresolution magnetic field data were used to investigate 2 h regions adjacent to the shock and ejecta leading edge (Near-Shock and Near-LE regions, respectively), and the results were compared with a 2 h region upstreamof the shock. The inertial-range spectral indices in the sheaths are found to be mostly steeper than the Kolmogorov -5/3 index and steeper than in the solar wind ahead. We did not find indications of an f(-1) spectrum, implying that magnetic fluctuation properties in CME sheaths differ significantly from planetary magnetosheaths and that CME-driven shocks do not reset the solar wind turbulence, as appears to happen downstream of planetary bow shocks. However, our study suggests that new compressible fluctuations are generated in the sheath for a wide variety of shock/upstream conditions. Fluctuation properties particularly differed between the Near-Shock region and the solar wind ahead. A strong positive correlation in the mean magnetic compressibility was found between the upstream and downstream regions, but the compressibility values in the sheaths were similar to those in the slow solar wind (
Subject: coronal mass ejections
interplanetary shock
magnetic field
solar wind
turbulence
115 Astronomy, Space science
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