Physics of auroral phenomena : proceedings of the 40th annual seminar, Apatity, 13-17 March, 2017 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2017. - 143 с. : ил., табл.

Theory ofa receiving antenna applied to the spacecraft observations o fquasi-electrostatic whistler mode waves in both cases 7eff /1^. can significantly exceed unity. Conclusions In this paper, we proposed a method for calculating the effective length of an electrical receiving antenna in case of the quasi-electrostatic chorus waves. We applied the obtained general relations to several cases of chorus electric field measurements onboard THEMIS spacecraft, and found that the antenna effective length could be up to an order (or more) of magnitude greater than the geometric length /rec . Therefore, the actual value of the electric field component that is parallel to the antenna can be less and even much less than quantity U/l ^ . , which is conventionally used as the measured electric field, and it is important to take properly into account the resonance nature of quasi-electrostatic whistler mode waves when interpreting the results of chorus electric field measurements. Acknowledgements. This work was supported by the Russian Science Foundation under grant 15-12-20005. We acknowledge NASA contract NAS5-02099 and V. Angelopoulos for use of data from the THEMIS Mission, specifically: J. W. Bonnell and F. S. Mozer for use of EFI data; A. Roux and O. LeContel for use of SCM data; К. H. Glassmeier, U. Auster and W. Baumjohann for the use of FGM data provided under the lead of the Technical University of Braunschweig and with financial support through the German Ministry for Economy and Technology and the German Center for Aviation and Space (DLR) under contract 50 ОС 0302. References Agapitov, O.V., A.V. Artemyev, D. Mourenas, V. Krasnoselskikh, J. Bonnell, O.L. Contel, C.M. Cully, and V. Angelopoulos (2014), The quasi-electrostatic mode of chorus waves and electron nonlinear acceleration, J. Geophys. Res. Space Physics, 119,1606-1626. Balanis, C.A. (2016), Antenna Theory: Analysis and Design, 4th ed., Wiley, Hoboken, N. J. Burch, J.L., and V. Angelopoulos (2009), The THEMIS Mission, Springer-Verlag, New York. Chugunov, Y.V., and E.A. Shirokov (2016), Quasistatic dipole in magnetized plasma in resonance frequency band. Response o f the receiving antenna, and charge distribution on the antenna wire, Cosmic Res., 54(3), 198-204. Chugunov, Y.V., E.A. Shirokov, and LA. Fomina (2015), On the theory of a short cylindrical antenna in anisotropic media, Radiophys. Quantum Electron., 58(5), 318-326. Chum, J., and O. Santoh'k (2005), Propagation of whistler-mode chorus to low altitudes: Divergent ray trajectories and ground accessibility, Ann. Geophys., 23(12), 3727-3738. Santolfk, О., M. Parrot, and F. Lefeuvre (2003), Singular value decomposition methods for wave propagation analysis, Radio Sci., 38(1), 1010. Santolfk, О., E. MacuSovd, I. KolmaSova, N. Comilleau-Wehrlin, and Y. de Conchy (2014), Propagation of lower- band whistler-mode waves in the outer Van Allen belt: Systematic analysis o f 11 years of multi-component data from the Cluster spacecraft, Geophys. Res. Lett., 41,2729-2737. Shirokov, E.A., A.G. Demekhov, Y.V. Chugunov, and A.V. Larchenko (2017), Effective length of a receiving antenna in case of quasi-electrostatic whistler mode waves: Application to spacecraft observations o f chorus emissions, Radio Sci., 52, 884-895. 61