Articles | Volume 34, issue 2
Regular paper
16 Feb 2016
Regular paper |  | 16 Feb 2016

Generation of resonant Alfvén waves in the auroral oval

V. A. Pilipenko, D. Yu. Klimushkin, P. N. Mager, M. J. Engebretson, and O. V. Kozyreva

Abstract. Many independent observations have shown that resonant field line Pc5 pulsations (typical periods of about several minutes) are preferably excited inside the auroral oval. Consideration of the most evident interpretation schemes shows that there is no simple explanation of this effect. Here we consider theoretically the generation of toroidal Pc5 Alfvén waves by fluctuating magnetospheric field-aligned currents. It is shown that the Alfvén wave latitudinal structure has the same features as in the case of the classical field line resonance driven by external sources: a peak localized in latitude and a 180° phase shift across the resonant magnetic shell. This model suggests an additional mechanism of ultra-low-frequency (ULF) wave excitation which can operate at auroral latitudes.

Short summary
Many independent observations have shown that long-period electromagnetic waves (with periods of several minutes) are preferably observed inside the auroral oval. Here we examine theoretically the possibility of Alfven wave generation by fluctuating large-scale field-aligned currents which couple outer space and the auroral ionosphere. The elaborated model indeed confirms the feasibility of an additional mechanism of long-period wave excitation which can operate at auroral latitudes.