Summary—The auroral data collected by expeditions to the Antarctic Continent are examined in order to determine the position of the Zone of Maximum Auroral Frequency. It is found that these data are not of a form permitting accurate estimation of the position of this Zone but the approximate position has been determined from a general discussion of the data. It is found that the Zone is probably circular with center at 75° south and 129° east, a point near the magnetic axis‐pole. The radius of the zone is about 18°.

No abstract

No abstract

No abstract

(1) Introduction—Compared with the other two main ionized regions of the upper atmosphere (E‐ and F1‐regions) the highest and most richly ionized region (F2) presents theoretical problems which can be discussed adequately only when data collected in many different places of the Earth's surface can be examined simultaneously. The situation is similar to that of terrestrial magnetism in that the observations at one observatory cannot yield sufficient data upon which a theoretical discussion may be based. Amongst the many observations which can be made with wireless waves reflected from the F2‐region the most fundamental are concerned with the measurement of the maximum charge‐density of this region. In view of the apparently anomalous behavior of this region it is of interest to investigate firstly the diurnal and secondly the seasonal variation of the maximum charge‐density of the region. Thirdly the wide fluctuations of this quantity which occur from day to day are of interest since they appear to be intimately connected with other geophysical occurrences.