Statistical Analysis of Orientation, Shape and Size of Switchbacks

Abstract:

One of the main discoveries from the first two encounters of Parker Solar Probe was the presence of switchbacks, whose deflections dominated the magnetic field measurements. Determining their shape and size could provide evidence for their origin, which is still unclear. Previous work on how deflection direction influences switchback duration has indicated that these are long, thin structures, although the direction of their major axis could not be determined. Rather than first defining an alignment with a physical direction, we instead search for the alignment direction that is most consistent with long, thin structures. We find that for all the streams analysed the alignment direction is always deflected away from the radial direction, to the side of -T in RTN coordinates, which is also distinct from the background flow direction. We conclude that the most likely physical direction is the Parker spiral, with switchbacks having a length several tens that of their width. We also note that in this formulation the switchback duration is only a function of spacecraft cutting direction. This means that a link cannot be made between larger switchback duration in time series data and a greater contribution to the solar wind.