Effective length of areceiving antenna in case of quasi-electrostatic whistler mode waves: Application to spacecraft observations of chorus emissions

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.