A Study of Conjugate PC 5-6 Magnetic and Absorption Pulsation Event at Sub-auroral Latitudes in the Morning Sector

An interval of long-period hydromagnetic wave activity occurring during local morning in the decay phase of a magnetic storm has been studied using ground-based magnetic field and cosmic noise absorption data. During an ~90 min. interval of decreasing ring current following the storm maximum, a hydromagnetic pulsation train in the Pc5-6 range emerged (frequencies decreasing monotonically from ~3 mHz to ~1 mHz), accompanied by similar oscillations of the cosmic radio noise signal.