Dr. Hamish Reid

University College London, UK

Solar electron beams, turbulence, and plasma waves: the perfect ingredients for radio burst fine structure.

Abstract: The Sun frequently accelerates near-relativistic electron beams that travel out through the solar corona and interplanetary space. Undergoing wave-particle interactions with Langmuir waves, these beams are the driver for type III radio bursts, the brightest astrophysical radio sources detected by humans. I will first discuss numerical predictions about how these electron beams evolve as a function of distance from the Sun, topical due to the new in situ observations that Solar Orbiter and Parker Solar Probe are taking close to the Sun. Secondly, I will address the formation and motion of type III fine frequency structure whose origins are a puzzle, believed to be related to plasma turbulence in the solar corona and solar wind. Combining a theoretical framework with kinetic, wave-particle simulations and high-resolution LOFAR radio type III observations, I will quantitatively show that the fine structures are caused by the moving intense clumps of Langmuir waves in a turbulent medium. Recent results show how type III fine structure can be used to remotely analyse the intensity and spectrum of compressive density fluctuations, and can infer ambient temperatures in astrophysical plasma, both significantly expanding the current diagnostic potential of solar radio emission.