Waiting time (distance) distributions of magnetic field and velocity PVI events during the first Parker Solar Probe encounter

During the Parker Solar Probe's (PSP) first perihelion pass, the spacecraft reached to within a heliocentric distance of ~37 solar radii and observed magnetic and flow structures characterized by sharp gradients. As we try and understand these intermittent coronal structures better, an important property to examine is their degree of correlation. To this end, we use the well-tested Partial Variance of Increments (PVI) technique [1] to identify intermittent events in FIELDS and SWEAP observations of magnetic and velocity fields. We then examine the distributions of waiting times between events with varying separation and PVI levels. We find power-law distributions, suggesting a high degree of correlation that may originate in a clustering process, as opposed to a random distribution produced by a memory-less Poisson process [2]. We also find that waiting times between events with separations larger than inertial-range scales follow a power-law close to -1, hinting at a possible connection with observations of "1/f noise" associated with signals originating near the source solar surface [3]. The present study complements the one by Dudok de Wit et al., which focuses on the waiting times between the observed "switchbacks" in the radial magnetic field.

[1] Greco et al. Space Sci. Rev. (2018) 214:1

[2] Greco et al. Phys. Rev. E (2009) 80, 046401

[3] Matthaeus & Goldstein PRL (1986) 57, 4