Radio waves and whistler-mode waves in solar wind and their interactions
with energetic electrons
Abstract
The role of waves in the propagation, scattering and energization of
electrons in the solar wind has long been a topic of interest.
Conversely, understanding the excitation of waves by energetic electrons
can provide us with a diagnostic for the processes that accelerate the
electrons. We will discuss two different processes: (1) the interaction
of narrowband whistler-mode waves with solar wind electrons, and (2) how
periodic Type III radio bursts yield clues to small-scale acceleration
of energetic electrons in the solar corona. Waveform captures in the
solar wind at 1 AU obtained by the STEREO revealed the existence of
narrowband large amplitude whistler mode waves, propagating at highly
oblique angles to the magnetic field. Similar waves are less commonly
seen inside .2 AU by Parker Solar Probe. The differences provide clues
for understanding electron propagation, scattering and energization.
Type III radio bursts have long been used as remote probes of electron
acceleration in the solar corona. The occurrence of periodic behavior in
Type III bursts observed by Parker Solar Probe, Wind and STEREO when
there are no observable flares provides a unique opportunity to diagnose
small-scale acceleration of electrons in the corona. Periodicities of
~ 5 minutes in the Solar Dynamics Observatory
Atmospheric Imaging Assembly (AIA) Extreme Ultraviolet data in several
areas of an active region are well correlated with the repetition rate
of the Type III radio bursts. Similar periods occur in the Helioseismic
and Magnetic Imager (HMI )data. These results provide evidence for
acceleration by wave-modulated reconnection or small-scale size waves,
such as kinetic Alfven waves, even during intervals with no observable
flares. The possible connections between these two phenomena will be
addressed.