Polarization Characteristics of Individual Elements in a PC 1 Micropulsation Event

Abstract

POLARIZATION characteristics of PC 1 micropulsations of the Earth's magnetic field were examined in narrow frequency bands. Wide-band observations were reported earlier¹. The induction magnetometer data were recorded at College, Alaska, in FM mode on magnetic tape. The data were played back through a bank of active band-pass filters into a dual-beam oscilloscope. Each filter had attenuation slope 24 dB/octave nominal value and approximately 12 dB/octave at a cut-off. Two filters were used in series for each magnetic field component. The high-frequency and low-frequency cut-offs were set equal to the desired mid-band frequency f_m, then the filters were tuned to preserve the shape and sense of rotation for test patterns at f_m. There was considerable phase shift through the filters, but this procedure preserved the shape and sense of natural PC 1 configurations in the narrow band, and it is these characteristics which are discussed here. Fig. 1, top, illustrates the attenuation on either side of f_m. All circles had the same amplitude at the input to the filter system. The largest circle is the filter output f_m = 0.5 Hz.