2016/02/29 by Erika Palmerio, Emilia Kilpua, Emilia K. J. Kilpua +2 · 1 citation
Biochemistry, Genetics and Molecular Biology · Medicine · Physics and Astronomy · #Astrophysics #Coronal mass ejection #Ejecta #Geomagnetism and Paleomagnetism Studies #Ionosphere and magnetosphere dynamics #Magnetic field #Medicine #Physics #Shock (circulatory) #Solar and Space Plasma Dynamics #Solar wind #astro-ph.SR #physics.space-ph
paper · pdf · doi:10.5194/angeo-34-313-2016
published as Ann. Geophys., 34, 313-322, 2016 · 10 pages, 7 figures, accepted for publication in Annales Geophysicae
openalex publication_date 2016/02/29 · openalex created_date 2016/06/24 · arxiv created 2017/01/30 · arxiv updated 2017/01/31 · openalex updated_date 2026/08/05
Abstract. Planar magnetic structures (PMSs) are periods in the solar wind during which interplanetary magnetic field vectors are nearly parallel to a single plane. One of the specific regions where PMSs have been reported are coronal mass ejection (CME)-driven sheaths. We use here an automated method to identify PMSs in 95 CME sheath regions observed in situ by the Wind and ACE spacecraft between 1997 and 2015. The occurrence and location of the PMSs are related to various shock, sheath, and CME properties. We find that PMSs are ubiquitous in CME sheaths; 85 % of the studied sheath regions had PMSs with the mean duration of 6 h. In about one-third of the cases the magnetic field vectors followed a single PMS plane that covered a significant part (at least 67 %) of the sheath region. Our analysis gives strong support for two suggested PMS formation mechanisms: the amplification and alignment of solar wind discontinuities near the CME-driven shock and the draping of the magnetic field lines around the CME ejecta. For example, we found that the shock and PMS plane normals generally coincided for the events where the PMSs occurred near the shock (68 % of the PMS plane normals near the shock were separated by less than 20° from the shock normal), while deviations were clearly larger when PMSs occurred close to the ejecta leading edge. In addition, PMSs near the shock were generally associated with lower upstream plasma beta than the cases where PMSs occurred near the leading edge of the CME. We also demonstrate that the planar parts of the sheath contain a higher amount of strong southward magnetic field than the non-planar parts, suggesting that planar sheaths are more likely to drive magnetospheric activity.