GEOMAGNETIC MICROPULSATION RESULTS FROM BYRD STATION AND GREAT WHALE RIVER

Abstract

Early reports from the near-conjugate stations at Great Whale River and Byrd Station were based on the scanty data available in early 1961 (Lokken et al., Martin et al. 1961). The increased volume of data seems now to justify another preliminary report, in which the chief emphasis is on the time-agreement of the abrupt commencements of the numerous examples of Birkeland's "Polar Elementary Storms". Passing reference only is made to the associations at Byrd between VLF hiss and other ionospheric phenomena that are being reported by Stanford University. In the auroral zones, the magnetic activity is usually so great, even during the IQSY, that magnetograms can be employed usefully to supplement the micropulsation records. Using selected nighttime occasions, when the change in H is so sudden that a reasonable accuracy in the timing of the micropulsations can be achieved, it is found that the time differences between the two conjugate stations average ± 1 minute, although there is clear evidence that the two stations are not conjugate at all times, as evidenced by the lack of similarity of records. It is confirmed that the more abrupt changes in the magnetic field are associated with high-frequency "riders" of the order of 1 c.p.s., and that these events are often seen with the same riders at the same time at our mid-latitude stations. The return currents that show up in these lower latitudes must be taken into consideration when the areas of conjugate station agreement are considered. The daytime regime of regular (Pc) variations did not lend itself to accurate time comparison, except for very long-period oscillations at the two stations, when the maximum excursions were so far apart in time that one could reasonably assume that the indicated phase differences on the records at the two stations were correct. On this assumption, the long-period oscillations are nearly coincident at the two stations. This may usually be true for the shorter-period oscillations also, but, in many cases, considerable phase differences do exist. These, however, may be due partly to differences in the electronic equipment.The general course of the geomagnetic diurnal variation at Byrd is shown, but these data may apply only to the two auroral conjugate stations and to periods of low solar activity.Up to the present time, only two cases of coincident satellite and ground station abrupt commencements have been observed. These were detected readily only by our mid-latitude stations, possibly because the two events occurred when these stations were on the side of the earth facing the solar wind. It is possible that nighttime coincidences will appear chiefly at the two auroral stations.