Correlated Magnetic Field Dropouts and Plasma Wave Activity at Switchback Boundaries as Observed by Parker Solar Probe

Abstract

<p>The first solar encounters by the Parker Solar Probe revealed the magnetic field to be dominated by short field reversals in the radial direction referred to as "switchbacks."<span>  </span>While radial velocity and proton temperature were shown to increase inside the switchbacks, B exhibits very brief dropouts only at the switchback boundaries.<span>  </span>Brief intensifications in spectral density measurements near the electron plasma frequency, f<sub>pe</sub>, have also been observed at these boundaries, indicating the presence of plasma waves triggered by electron beams.<span>  </span>We perform a correlative study using observations from the Parker FIELDS Radio Frequency Spectrometer (RFS) and Fluxgate Magnetometer (MAG) to compare occurrences of spectral density intensifications at the electron plasma frequency (f<sub>pe</sub> intensifications) and B dropouts at switchback boundaries during Parker's first and second solar encounters.<span>  </span>We find that only a small fraction of minor B dropouts are associated with f<sub>pe</sub> intensifications.<span>  </span>This fraction increases with B dropout size until all dropouts are associated with f<sub>pe</sub> intensifications.<span>  </span>This suggests that in the presence of strong B dropouts, electron currents that create the perturbation in B along the boundaries are also stimulating plasma waves such as Langmuir waves.</p>