Magnetic Switchback Occurrence Rates in the Inner Heliosphere: Parker Solar Probe and 1 au

• Published in: Astrophysical journal. Letters Vol. 929; no. 1; p. L10
• Main Authors: Pecora, Francesco, Matthaeus, William H., Primavera, Leonardo, Greco, Antonella, Chhiber, Rohit, Bandyopadhyay, Riddhi, Servidio, Sergio
• Format: Journal Article
• Language: English
• Published: Austin The American Astronomical Society 01.04.2022; IOP Publishing
• Subjects: Frequency analysis; Heliosphere; Interplanetary magnetic fields; Interplanetary medium; Interplanetary turbulence; Magnetic fields; Orbits; Solar probes
• ISSN: 2041-8205; 2041-8213
• DOI: 10.3847/2041-8213/ac62d4

The subject of switchbacks, defined either as large angular deflections or polarity reversals of the magnetic field, has generated substantial interest in the space physics community since the launch of the Parker Solar Probe (PSP) in 2018. Previous studies have characterized switchbacks in several different ways and have been restricted to data available from the first few orbits. Here, we analyze the frequency of occurrence of switchbacks per unit distance for the first full eight orbits of PSP. In this work, events that reverse the sign of the magnetic field relative to a regional average are considered switchbacks. A significant finding is that the rate of occurrence falls off sharply approaching the Sun near 0.2 au (40 R ⊙ ) and rises gently from 0.2 au outward. The analysis is varied for different magnetic field cadences and for different local averages of the ambient field, confirming the robustness of the results. We discuss implications for the mechanisms of switchback generation. A publicly available database has been created with the identified reversals.