A two years 1969?1971 study of the atmospheric radio noise on low and VHF at the Br�beuf College Geophysical Observatory, Montr�al, Canada

Abstract

Two annual series (1969–1971) of night recordings of the atmospheric radio noise on 950 MHz have been analysed. Adetailed description of the receiving antenna and of the receiver itself is given. Great care has been taken for avoiding spurious registrations. The recordings were made every day, some hours before local sunset until some hours after local sunrise. The analysis shows that the atmospheric radio noise has generally two peaks: one before local midnight and another before local sunrise. The portion of the real radio cosmic noise remains unknown. during stormy weather the pattern on 950 MHz shows peculiar sudden and short lived groups of peaks. The author believes that these VHF sferics are caused by a distinct event namely by corona type pulsations issued from the stepped leader, which precedes the main stroke. Winter blizzards do not raise LF sferics but only a ‘frying noise’. The main stroke of the lightning is considered as a quarterwave Marconi grounded antenna, radiating a variable fundamental frequency fonction of the length of the lightning track from cloud to earth and vice versa. The stepped leader causes special VHF sferics. Low frequency (15–20 kHz) sferics show a different trend in the cold and warm sectors of extratropical cyclones. While a tropical cyclone is still at sea, sferics are absent. If some are present, radio goniometric fixes have shown that they are located on the limiting border of the storm, where it contacts the ocean high pressure anticyclonic air mass; not in the center of the tempest. Moreover, the continuous hissing noise of the high winds decreases as the center of the cyclone is approaching. In the cities, the reported lightnings are due to ground short-circuits.