Many plasma processes in the solar wind with macroscopic consequences involve interactions at or below 100 km scales. Magnetic reconnection, turbulent dissipation, and heliospheric radio bursts are all examples. This work takes advantage of recent advances in spacecraft in-situ measurement capabilities to explore such microscale plasma processes in the solar wind that have macroscopic consequences.

The microphysical phenomena of Langmuir waves, heliospheric radio bursts, and density turbulence are investigated using high-cadence electric field waveform observations from the STEREO spacecraft. These processes are of particular interest since they can be used to investigate longstanding questions concerning coronal heating and solar wind acceleration.

A formulation of Langmuir waves as eigenmodes of ambient solar wind density cavities is derived and shown to be consistent with observations. Consequences of the eigenmode interpretation such as three-dimensional Langmuir wave structure, localized wave packet growth, conversion into electromagnetic radiation, and the nature of the interaction between Langmuir waves and a turbulently fluctuating density medium are explored using both measurement and derivation. Measurements of the power spectrum of solar wind density turbulence in the dissipation range are also explored.