Statistics of auroral radio absorption at Siple and South Pole

• Main Author: S Krishnaswamy
• Format: Report
• Language: English
• Published: Institute for Physical Science and Technology, University of Maryland 1987
• Subjects: Siple; South Pole; Antarc*; Antarctica; Memoirs of National Institute of Polar Research; Polar Research; South pole
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2192; http://id.nii.ac.jp/1291/00002192/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2192&item_no=1&attribute_id=18&file_no=1

Analysis of cosmic noise absorption data from South Pole (L≈14) and Siple (75.6°S, 83.6°W, L=4.2), Antarctica, (a pair of stations on opposite sides of the latitude of maximum auroral activity) has revealed important differences in the statistics of auroral radio absorption at the two locations. At Siple, there is a general tendency for summer absorption levels to be higher than the absorption in winter (especially around local magnetic noon), but the data (1975,1980,1982) show significant year-to-year variations in the diurnal patterns of absorption. The diurnal patterns at South Pole also exhibit year-to-year variations (1982-1985) but they are very different from those at Siple, and the winter/summer relationship also changes from year to year. However, the regular trend in the South Pole variations suggests that they may be subject to a form of solar-cycle control not apparent at Siple. A second difference has to do with the occurrence statistics : while at Siple the occurrence-frequency distribution departs significantly from a log-normal relation (a relation commonly adopted to characterize the cumulative amplitude-probability distribution of auroral absorption), the South Pole distributions are closer to a log-normal and the two sets of distributions can have substantially different trends above about 1dB. Comparison with seasonal and annual means of the geomagnetic Ap index suggests that auroral absorption at Siple is more strongly correlated with Ap than is absorption at South Pole. In addition to their relevance for high latitude radio communication circuits, these observations may also have implications for auroral zone physics and morphology and also for magnetosphere-ionosphere interactions.