On Collisionless Electron-Ion Temperature Equilibration in the Fast Solar Wind

Abstract

We explore a mechanism, entirely new to the fast solar wind, of electron heating by lower hybrid waves to explain the shift to higher charge states observed in various elements in the fast wind at 1 A.U. relative to the original coronal hole plasma. This process is a variation on that previously discussed for two temperature accretion flows by Begelman & Chiueh. Lower hybrid waves are generated by gyrating minor ions (mainly alpha-particles) and become significant once strong ion cyclotron heating sets in beyond 1.5 R_sun. In this way the model avoids conflict with SUMER electron temperature diagnostic measurements between 1 and 1.5 R_sun. The principal requirement for such a process to work is the existence of density gradients in the fast solar wind, with scale length of similar order to the proton inertial length. Similar size structures have previously been inferred by other authors from radio scintillation observations and considerations of ion cyclotron wave generation by global resonant MHD waves.

32 pages including 11 figures, 4 tables, accepted by ApJ

References in corpus (2)

• Alfvenic Turbulence in the Extended Solar Corona: Kinetic Effects and Proton Heating
• On the Determination of Ejecta Structure and Explosion Asymmetry from the X-ray Knots of Cassiopeia A

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• Linking the Sun to the Heliosphere Using Composition Data and Modelling. A Test Case with a Coronal Jet
• Tests for coronal electron temperature signatures in suprathermal electron populations at 1 AU
• How Nanoflares Produce Kinetic Waves, Nano-Type III Radio Bursts, and Non-Thermal Electrons in the Solar Wind
• A simple model for electron plasma heating in supernova remnants
• Preferential energization of alpha particles in polar coronal holes at one solar radius above the photosphere