Effective length of a receiving antenna in case of spacecraft observations of quasi-electrostatic chorus emissions

We propose a method of calculating the effective length of receiving antenna for the case of spacecraft observations of quasi-electrostatic chorus emissions. Using the obtained analytical expression, we calculate this length for some measurements of chorus wave quasi-electrostatic fields onboard THEMIS spacecraft. The calculation results show that the effective length can be up to an order of magnitude greater than the geometric length of receiving antenna. Therefore, the actual electric field value can be much less as compared to the one calculated using the geometric length which is a conventionally used technique in the satellite data analysis. In particular, this result can be important for the estimates of electron energization by quasi-electrostatic chorus waves.