Kinetic physics everywhere in the inner heliosphere: Evidence from the FIELDS instrument on Parker Solar Probe
Abstract
The NASA Parker Solar Probe mission has made its first set of solar encounters at 35.7 solar radii. The first encounters reveal a solar wind rich in instabilities and kinetic physics. The FIELDS instrument on PSP measures copious, intermittent burstsof electron plasma (Langmuir) waves throughout Encounters 1 and 2. These waves are purely electrostatic, to the sensitivity of the measurement, and have wave (electric field) vectors aligned with the solar wind magnetic field. We suggest that these Langmuir waves are generated on a Landau resonance by electron beams with beam speeds of 5-10 v_th. The duration of the bursts suggests beams of ~100-10000 km across the magnetic field. We examine the statistics and occurence conditions. Langmuir waves during Encounter 1 are definitively not associated with solar type III radio bursts. FIELDS also measures signatures of ion cyclotron waves and kinetic scale turbulence, with indications for energy exchange processes in the inner corona.