Ground‐based photometric observations of the magnetospheric dayside cleft

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Abstract
A ground‐based meridian‐scanning photometer was operated at Cape Parry, N.W.T., Canada (70°N, 125°W geographic) in November and December, 1973, to observe the atomic oxygen emissions at 6300 Å and 5577 Å, and the H‐beta emission at 4861 Å. A 6300 Å behaviour pattern that could be identified with the dayside cleft was observed during a quiet afternoon and during a magnetically disturbed period. During quiet times a 1 kR 6300 Å feature was observed at 78° invariant latitude while during a modest disturbance the intensity increased to 4 kR and the feature moved to 73° invariant. This confirmed that the 6300 Å signature is readily identifiable from the ground, and that Cape Parry is one of the few relatively accessible Northern hemisphere sites where the optical cleft emissions can be observed from the ground.