VHF radar observation of auroral E-region irregularities associated with moving-arcs

• Main Authors: Tadahiko Ogawa, Kiyoshi Igarashi
• Format: Report
• Language: English
• Published: Hiraiso,Branch, Radio Research Laboratories 1982
• Subjects: Syowa Station; Antarc*; Antarctica; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=1264; http://id.nii.ac.jp/1291/00001264/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=1264&item_no=1&attribute_id=18&file_no=1

Electron density irregularities appearing in the auroral E-region during a substorm expansion phase were examined by using a 50MHz doppler radar at Syowa Station, Antarctica. The following results are obtained. (1) Optical aurora is not always collocated with radio aurora, which suggests that the strong electric field exciting plasma instabilities in the E-region does not always have an intimate relation to the magnetospheric electric field. (2) The echoing region is substantially limited within the radar range where aspect angles are between 88°and 92°. (3) The 50MHz radar wave may undergo a few degrees of refraction due to high electron density. (4) Growth and decay times of the instabilities in accord with changes in electric field strength are a few seconds or less. (5) With increasing electric field, echo intensity and mean doppler velocity increase, and the doppler velocity spectrum changes from a 'diffuse' into a 'discrete' form (two-stream-like spectrum). A possibility of the neutral wind effect modifying electron drifts is suggested. These results are compared with the existing theories and with the radar observations made at other stations.