LARGE AMPLITUDE PC 1 EVENTS AT COLLEGE

The Pc 1 events with amplitudes over ∼1/2γ recorded at College, Alaska, over a 6 1/2 year interval, were studied. Their general characteristics are described. Sonagram displays and polarizations are similar to those for smaller events, but there is typically more ionospheric cosmic noise absorption accompanying the large events, and the large events are usually observed at only one station. It is proposed that large amplitudes observed on the ground are at least partially due the presence of unusually welldefined wave guides of enhanced ionization along magnetospheric field lines. © 1968, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.