Localizing Sources of Pc1 Geomagnetic Pulsations

The position of zones of ion-cyclotron instability is analyzed in relation to the plasmasphere in the period 00:00 to 08:00 UT on September 11, 2017, using proton flux measurements made by low-orbit satellites. The position and dynamics of these zones help explain the structure and dynamics of the spectrum of geomagnetic pulsations in the range 0.2 to 4 Hz observed on the surface of Earth at this time.