Wave-particle energy transfer directly observed in an ion cyclotron wave

¹ Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA
e-mail: daniel.vech@lasp.colorado.edu
² Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85719, USA
³ Space Science Laboratory, University of California Berkeley, Berkeley, CA, USA
⁴ Smithsonian Astrophysical Observatory, Cambridge, MA 02138, USA
⁵ LPC2E, CNRS and University of Orléans, Orléans, France
⁶ Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI 48109, USA
⁷ School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA
⁸ NASA Goddard Space Flight Center, Greenbelt, MD, USA

Received: 30 August 2020
Accepted: 28 October 2020

Abstract

Context. The first studies with Parker Solar Probe (PSP) data have made significant progress toward understanding of the fundamental properties of ion cyclotron waves in the inner heliosphere. The survey mode particle measurements of PSP, however, did not make it possible to measure the coupling between electromagnetic fields and particles on the time scale of the wave periods.

Aims. We present a novel approach to study wave-particle energy exchange with PSP.

Methods. We used the Flux Angle operation mode of the Solar Probe Cup in conjunction with the electric field measurements and present a case study when the Flux Angle mode measured the direct interaction of the proton velocity distribution with an ion cyclotron wave.

Results. Our results suggest that the energy transfer from fields to particles on the timescale of a cyclotron period is equal to approximately 3–6% of the electromagnetic energy flux. This rate is consistent with the hypothesis that the ion cyclotron wave was locally generated in the solar wind.