Pc 1 wives and ionospheric Alfven resonator: Generation or filtration?

We analyze vertical profiles of Pc 1 wave fields produced in the ionosphere by Alfven waves of magnetospheric origin. We show that the ratio of the el ectric and magnetic fields varies strongly with frequency due to the influe nce of the ionospheric Alfven resonator. The difference is most remarkable for frequencies corresponding to either maximum or minimum ionospheric refl ection. Therefore, low-orbiting satellites detecting Pc 1 emissions in the ionosphere (at the same field line as their magnetospheric source) can prov ide valuable information regarding the question whether these waves are gen erated at conditions of maximum or minimum ionospheric reflection and wheth er this reflection influences significantly their generation in the magneto sphere. Comparison of our theoretical result with recent statistical analys is of Pc 1 pearls recorded onboard DE 2 suggests that these waves correspon d to the maximum reflection. This implies that ionospheric reflection playe d a significant role in formation of these emissions.