Observed Deviations from Kinetic Alfvén Wave Theory in Solar Wind Turbulence Near Proton Scales
Abstract
The dominant dissipation mechanism at play in turbulent collisionless magnetized plasmas remains an open question. Kinetic Alfvén Waves (KAWs) are often believed to be a primary candidate as they are theoretically able to dissipate energy at electron scales; however, direct measurements of these smallest scales have been historically difficult to achieve. Recent observations of the near-sun (~0.074 au / ~15.9 Solar Radii ) solar wind during Parker Solar Probe's (PSP) Encounter 9 provide direct measurement of electric and magnetic fields in the electron dissipation range. Wave behavior is characterized by comparing measurements of the ratio of the wave electric to magnetic fields as a function of frequency to existing theoretical predictions for KAWs. Deviations from theory near proton scales are observed, along with decoherence of the electric and magnetic fields, before returning to coherent KAW behavior beyond ion scales. Explanations for these deviations are sought by a several means. First, we compare observations to numerical solutions from the PLUME dispersion solver for the case of a hot, drifting, electron-proton plasma with Bi-Maxwellian velocity distributions. Secondly, simultaneous observations of the Helicity Barrier in the electric and magnetic power spectra are considered as an explanation for deviations from KAW theory near proton scales.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFMSH22D2027T