ANTENNA RADIATION NEAR THE LOCAL PLASMA FREQUENCY BY LANGMUIR WAVE EIGENMODES

Abstract

Langmuir waves (LWs) in the solar wind are generated by electron beams associated with solar flares, interplanetary shock fronts, planetary bow shocks, and magnetic holes. In principle, LWs localized as eigenmodes of density fluctuations can emit electromagnetic (EM) radiation by an antenna mechanism near the local plasma frequency fp and twice the local plasma frequency. In this work, analytic expressions are derived for the radiated electric and magnetic fields and power generated near fp by LW eigenmodes. The EM wave power emitted near fp is predicted as a function of the eigenmode length scale L, maximum electric field, driving electron beam speed, and the ambient plasma density and temperature. The escape to a distant observer of fp radiation from a localized Langmuir eigenmode is also briefly explored as a function of the plasma conditions.