Is. Dunlop et al., A MULTISTATION STUDY OF LONG-PERIOD GEOMAGNETIC-PULSATIONS AT CUSP AND BOUNDARY-LAYER LATITUDES, Journal of atmospheric and terrestrial physics, 56(5), 1994, pp. 667-679
The characteristics of 1-20 mHz (Pc5) geomagnetic pulsations recorded
during the daytime on the ground at cusp and boundary layer latitudes
have been examined. On quiet and moderately disturbed days the major s
pectral contributions are due to three different mechanisms. Sustained
oscillations whose properties are consistent with the Kelvin-Helmholt
z instability at the low latitude boundary layer are the dominant mech
anism at -70 to -75-degrees geomagnetic latitude. Transient irregular
pulsations are frequently seen at single stations at the foot of polar
cap and boundary layer field lines. Occasionally similar transients o
ccur essentially simultaneously at widely spaced stations accompanied
by absorption spikes on riometer records. The latter signals are most
likely due to solar wind pressure pulses on the magnetopause. At cusp
latitudes the major spectral contribution arises from sustained irregu
lar pulsations centred on magnetic noon. Although their occurrence is
related to the proximity of the cusp's particle signature, it may be m
ore appropriate to discuss these signals in terms of fluctuations in b
oundary layer or mantle currents.