Planetary wave activity in the lower ionosphere during CRISTA I campaign in autumn 1994 (October-November)

On the basis of MEM spectrum analysis, the main planetary scale ̄uctuations formed in the lower ionosphere are studied over a period of 3±25 days during the CRISTA campaign (October-November 1994). Three dominant period bands are found: 3±5, 6±8 and 15±23 (mainly 16±18) days. For 7±8 and 16±18 day ̄uctuations, propagation was eastward with wave numbers K = 3 and K = 1, respectively. The magnitude of planetary wave activity in the mid-latitudes of the Northern Hemisphere during the CRISTA campaign seems to be fairly consistent with the expected undisturbed normal/climatological state of the atmosphere at altitudes of 80±100 km.