Effective length of a receiving antenna in case of quasi‐electrostatic whistler mode waves: Application to spacecraft observations of chorus emissions

Abstract

We propose a method for calculating the receiving antenna effective length in the case of reception of quasi‐electrostatic whistler mode waves in plasmas and apply it to the spacecraft observations of oblique VLF chorus waves. The method is based on the reciprocity theorem and requires an appropriate choice of the radiation source. Such a choice is possible on the basis of the measured emission parameters if a quasi‐monochromatic (i.e., having narrow instant width of the dynamic spectrum) wave packet with wave normal angles near the resonance cone is detected. We analyze several typical chorus events detected by Time History of Events and Macroscale Interactions during Substorms spacecraft and show that the effective length of receiving antenna can be more than an order of magnitude greater than the geometric length.

Theory of a Strip Antenna Located at the Interface of an Isotropic Medium and a Magnetoplasma

“…In integral Equations (22) and 23, it is assumed that |z| < d, and the integrals, which turn out to be singular for z − z → 0, are understood in the sense of Cauchy's principal value.…”

“…are fulfilled, the properties of these kernels allow one to obtain an approximate solution of Equations (22) and (23) in closed form. To this end, we represent the kernels of these equations as the sums of singular and regular terms:…”

“…Hence, the fulfillment of the first two inequalities in Equation (24) ensures the applicability of the used approximations. After the above algebra, integral Equations (22) and (23) are rewritten for |z| < d as…”

“…It can be shown [13,16] that the solutions of Equations (35) and (36) are the main terms of asymptotics of the solutions of the initial integral Equations (22) and (23) when inequalities (24) are fulfilled. In what follows, we restrict ourselves to analyzing only Equations (35) and (36).…”

“…Electrodynamic characteristics of metal antennas in a magnetoplasma have been studied in many papers (see, e.g., [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] and references therein). The interest in the subject is stipulated by the wide use of such transmitters in various experiments in laboratory and space plasmas [17][18][19][20][21][22], and is stimulated continuously by the needs of practical applications such as diagnostics of plasma media, space communication, etc. In earlier theoretical works, antennas with given currents in a homogeneous magnetoplasma have been considered [1][2][3][4][5][6][7].…”