Mode Conversion of Kinetic Alfvén Waves in the Presence of Proton Beams and Its Role in Plasma Heating in the Solar Corona

Abstract

The density inhomogeneity is a typical feature in various magnetoplasmas in the corona, where kinetic Alfvén waves (KAWs) are effectively generated and contribute greatly to the inhomogeneous heating of coronal plasmas. Proton beams exist widely in various space and solar plasma environments. In this paper, based on the kinetic Vlasov theory, we investigate the resonant mode conversion of Alfvén waves to KAWs in the presence of proton beams in an inhomogeneous plasma and the plasma heating of KAWs due to wave−particle interactions. It is found that the wave properties of excited KAWs are highly sensitive to the density of proton beams n bi /n 0, the drift velocity of proton beams v bi /v A, the proton-to-electron temperature ratio T i /T e , and the proton-beam-to-proton-temperature ratio T bi /T i . In addition, the maximum heating rate of KAWs Q m /Q 0 obviously increases with increasing n bi /n 0 and/or v bi /v A. As the electron beta β e increases, Q m /Q 0 decreases sharply in the region of 6 × 10−4 < β e < 10−2 and decreases slowly in the region of β e > 10−2. In addition, the applications of KAW dissipation to plasma heating are discussed in the corona and coronal loops. The KAWs associated with perturbed electric field E x ∼ a few V · m−1 are enough to supply the energy loss in the corona and coronal loops. The present results are of significant importance for comprehending the KAW excitation and the particle energization in the corona.