A Statistical Analysis of Interhemispheric Pi1B Seasonal Variations
Abstract
Pi1B magnetic pulsations are characterized by irregular ULF broadband bursts, with periods of between 1-40 seconds, and are well correlated with substorm onsets. There has been debate over the years regarding the source of these pulsations. Heacock [1967] originally suggested that Pi1B pulsations result from small-scale, local ionospheric currents at substorm onset. Arnoldy et al. [1998] discovered that these pulsations are observed at geosynchronous orbit at onset, implying that they originate beyond geosynchronous orbit and not in the ionosphere. Motivated by papers showing interhemispheric differences in substorm evolution [Papitashvili et al., 2002], as well as the Newell et al. [1996] result, where the authors used satellite data in a comprehensive statistical study to conclude that intense aurora occur only when the background ionospheric conductivity is low (i.e., it is not sunlit), a preliminary study of Pi B pulsation arrival times has been carried out, comparing onset times at the South Pole and Iqaluit, its approximate magnetic conjugate in northern Canada. During the spring of 1995, ground signatures of Pi1B pulsations at the South Pole tended to lead those at Iqaluit often by a minute or two, with a wide distribution in time differences. During the fall of 1995, however, events at Iqaluit tended to lead those at the South Pole, but with significantly smaller time differences and with less scatter than in the spring. This preliminary study suggests the presence of a seasonal dependence in Pi1B onset times in opposite hemispheres. Further work will analyze a much larger data set for purposes of improved statistical significance.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMSM31B2627S
- Keywords:
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- 2704 Auroral phenomena;
- MAGNETOSPHERIC PHYSICS;
- 2736 Magnetosphere/ionosphere interactions;
- MAGNETOSPHERIC PHYSICS;
- 2776 Polar cap phenomena;
- MAGNETOSPHERIC PHYSICS;
- 2794 Instruments and techniques;
- MAGNETOSPHERIC PHYSICS