SH049-0019
Magnetic switchbacks: on the sensitivity of the statistical results with the chosen methodology
Wednesday, 16 December 2020
Poster
Naïs Fargette1, Benoit Lavraud2, Alexis P Rouillard2, Nicolas Poirier1, Marit Oieroset3, Tai Phan4, Rui Pinto2, Athanasios Kouloumvakos1, Jonathan P Eastwood5, Jasper S Halekas6, Justin Christophe Kasper7, Jia Huang7, Stuart Bale8, Matthieu Berthomier9, Anthony W Case10, Kelly E Korreck10, Davin E Larson11, Philippe Louarn12, David Malaspina13, Marc Pulupa14, Michael Louis Stevens10, Phyllis L Whittlesey14 and Keith Goetz15, (1)IRAP, Toulouse, France, (2)IRAP/CNRS, Toulouse, France, (3)Univ California, Berkeley, CA, United States, (4)University of California Berkeley, Berkeley, United States, (5)Imperial College London, Physics, London, SW7, United Kingdom, (6)University of Iowa, Department of Physics and Astronomy, Iowa City, IA, United States, (7)University of Michigan, Climate and Space Sciences and Engineering, Ann Arbor, MI, United States, (8)University of California, Berkeley, Berkeley, CA, United States, (9)LPP, Ecole Polytechnique, UPMC, Paris, France, (10)Smithsonian Astrophysical Observatory, Cambridge, MA, United States, (11)Space Sciences Laboratory, Berkeley, CA, United States, (12)IRAP, CNRS, Toulouse, France, (13)University of Colorado, Astrophysical and Planetary Sciences Department, Boulder, CO, United States, (14)Space Sciences Laboratory, University of California Berkeley, Berkeley, CA, United States, (15)University of Minnesota, School of Physics and Astronomy, Minneapolis, MN, United States
Abstract:
Early Parker Solar Probe (PSP) data, when first streamed down to Earth, were astonishing in the number of magnetic field reversals they displayed. The radial magnetic field, which was expected to exhibit a persistent polarity inside a specific magnetic sector, was instead dominated by Alfvénic structures reversing the direction of the field. These field reversals are associated with velocity spikes, imposed on an otherwise calmer background. Due to these properties, the structures are called switchbacks or spikes depending on the focus (magnetic field or plasma velocity).
In this work, we perform a statistical and systematic analysis of switchbacks, with a particular focus on the sensitivity of the results to the definition of a switchback. Indeed, results vary whether the structures are defined based on 1) a reversal in direction of the magnetic field; 2) a deviation from a median value calculated over large time windows; or 3) a deviation from the Parker spiral.
When focusing on the switchback orientation as a deviation from the Parker spiral, we find that they are mostly isotropic but sometimes display some regular and constant Bt orientation for ~6h periods of time. These periods, even if not the most common, may not be explained by regular turbulence alone. We also investigate switchback properties as a function of magnetic connectivity to the Sun, using both connectivity tools and white light observations.
