[摘要] Meteors are an important source for (a) the metal atoms of theupper atmosphere metal layers and (b) for condensation nuclei, theexistence of which are a prerequisite for the formation ofnoctilucent cloud particles in the polar mesopause region. For abetter understanding of these phenomena, it would be helpful toknow accurately the annual and diurnal variations of meteor rates.So far, these rates have been little studied at polar latitudes.Therefore we have used the 33 MHz meteor radar of the ALOMARobservatory at 69° N to measure the meteor rates at this locationfor two full annual cycles. This site, being within 3° of theArctic circle, offers in addition an interesting capability: Theaxis of its antenna field points (almost) towards the Northecliptic pole once each day of the year. In this particularviewing direction, the radar monitors the meteoroid influx from(almost) the entire ecliptic Northern hemisphere.
We report on the observed diurnal variations (averaged over onemonth) of meteor rates and their significant alterationsthroughout the year. The ratio of maximum over minimum meteorrates throughout one diurnal cycle is in January and Februaryabout 5, from April through December 2.3±0.3. If comparedwith similar measurements at mid-latitudes, our expectation, thatthe amplitude of the diurnal variation is to decrease towards theNorth pole, is not really borne out.Observations with the antenna axis pointing towards the Northecliptic pole showed that the rate of deposition of meteoric dustis substantially larger during the Arctic NLC season than theannual mean deposition rate. The daylight meteor showers of theArietids, Zeta Perseids, and Beta Taurids supposedly contributeconsiderably to the June maximum of meteor rates. We note, though,that with the radar antenna pointing as described above, all threemeteor radiants are close to the local horizon but all threeradiants were detected.
