Turbulent Heating of Colliding Streams in the Solar Wind

Abstract

Turbulent heating of colliding plasma streams has previously been observed in the solar wind. The original data were interpreted in terms of a fluid model. We argue that a plasma-kinctic description is the more appropriate theoretical approach and is necessary in order to better understand the microscopic physical phenomena that underlie all fluid models. We used microscopic solar-wind parameters characteristic of conditions during the observations, together with the quasi-linear plasma-kinetic theory, to compute the expected magnetic field and temperature enhancements in the interaction region between two counterstreaming plasma beams. The physical mechanism of excitation is the electromagnetic two-stream instability in which Alfve'n waves are unstable. We compute a total field in the interaction region of B ∼ 8 γ (10-12 γ is observed) and a change in temperature of ΔT ∼ 1 x 10⁵ ° K is observed). Other features of the observations are discussed in terms of a plasma-kinetic theory.