Magnetic switchbacks: on the sensitivity of the statistical results with the chosen methodology

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.