Antarctic HF radar observations of irregularities associated with polar patches and auroral blobs: A case study

• Published in: Journal of Geophysical Research: Space Physics
• Main Authors: Ogawa, T., Nishitani, N., Pinnock, M., Sato, N., Yamagishi, H., Yukimatu, A. S.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Geophysical Union 1998
• Subjects: Antarctic; The Antarctic; Syowa Station; Antarc*
• Online Access: http://nora.nerc.ac.uk/id/eprint/504220/; https://doi.org/10.1029/98JA02044

We report a case study of decameter-scale electron density irregularities associated with polar cap patches and auroral (boundary) blobs in the southern high-latitude F region ionosphere. The observations were carried out on July 14, 1995, with the Antarctic Super Dual Auroral Radar Network HF radars located at Syowa Station and Halley. On that day, 17 irregularity events associated with the patches were identified in the polar cap. The time distribution of these events is consistent with previous model calculations of patch formation and transportation in the northern hemisphere for southward interplanetary magnetic field (IMF) conditions (Bz < 0). The irregularity areas observed can attain to 1000×1500 km that is comparable to a typical polar patch size, suggesting that the electron density within the patch is not uniform but structured. Somewhat surprisingly, patch-associated irregularities appear even under long-lasting northward IMF conditions (Bz > 0). These patches seem to have been transported into the polar cap from the dayside cusp where the patches had been generated under negative Bz conditions. The striated radar echo patterns due to a series of auroral blobs, clearly observed at Halley in the evening auroral zone, are well explained by previous simulations that calculated the time evolution and transportation of a patch initially located in the polar cap.