Effective Length of a Receiving Antenna in a Streaming Plasma

摘要

The root-mean-square (r.m.s) voltage induced on a receiving dipole antenna by incident potential waves in a streaming otherwise isotropic plasma in the resonance frequency band is calculated. The open-circuit voltage on antenna terminals is the product of the wave electric field strength at the receiving point and the effective length of the receiving antenna$L_eff$. The effective length differs substantially from that in a non-streaming plasma for waves propagating downstream at frequencies close to the plasma frequency. The case of stream velocity lower than the electron thermal velocity is considered, which is of interest for wave measurements in the solar wind. We discuss some implications for relevant experiments in space plasmas, namely the appearance of narrowband lines in the spectra around local plasma frequency observed in the solar wind. The possible exaggeration of plasma wave amplitudes in conventional interpretations of measurements is pointed out.