The effective altitude range of the ionospheric Alfvén resonator studied by high-altitude EISCAT measurements

The altitude profiles of ionospheric plasma obtained by the EISCAT incoherent scatter radar can be used to study the effect of the ionospheric Alfvén resonator (IAR) upon the formation of the wave signal on the ground. We examine here a fortunate case of a multiband wave Pc1 event on March 7, 2001, at a time when the EISCAT radar was operated in two modes simultaneously, thus covering an exceptionally wide altitude range. This made it possible to test the IAR model and its effect upon the wave signal over a larger altitude range than earlier, and to determine the effective altitude range of the resonator (the IAR domain), which has to be taken into account in full-wave numerical modeling. This case study demonstrates that the IAR domain that affects the wave signal on the ground is essentially localized below the height of about 1200–1500 km.