We analyze vertical profiles of Pc 1 wave fields produced in the ionosphere by Alfv¿n waves of magnetospheric origin. We show that the ratio of the electric and magnetic fields varies strongly with frequency due to the influence of the ionospheric Alfv¿n resonator. The difference is most remarkable for frequencies corresponding to either maximum or minimum ionospheric reflection. Therefore, low-orbiting satellites detecting Pc 1 emissions in the ionosphere (at the same field line as their magnetospheric source) can provide valuable information regarding the question whether these waves are generated at conditions of maximum or minimum ionospheric reflection and whether this reflection influences significantly their generation in the magnetosphere. Comparison of our theoretical result with recent statistical analysis of Pc 1 pearls recorded onboard DE 2 suggests that these waves correspond to the maximum reflection. This implies that ionospheric reflection played a significant role in formation of these emissions. ¿ 2000 American Geophysical Union