A viable source of low-latitude Pc3's in the magnetosphere

• Main Author: Kiyohumi Yumoto
• Format: Report
• Language: English
• Published: Onagawa Magnetic Observatory and Geophysical Institute, Tohoku University 1984
• Subjects: Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=1593; http://id.nii.ac.jp/1291/00001593/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=1593&item_no=1&attribute_id=18&file_no=1

Daytime magnetic pulsations observed at synchronous orbit by GOES 2 are analyzed to determine whether there is a candidate for the source of low-latitude Pc 3's in the outer magnetosphere. Compressional, radially transverse, and azimuthally transverse modes of magnetic pulsations in a wide frequency range exist simultaneously in the outer daytime magnetosphere. The compressional and the transverse modes of the daytime magnetic pulsations observed at GOES 2 are statistically dominant in the Pc 3 and in the Pc 4 frequency ranges, respectively. Some 70 percent of the compressional Pc 3 pulsations at GOES 2 have periods similar to the low-latitude Pc 3's observed at San Gabriel Canyon, which is located ∿ 11°west of GOES 2's longitude at L=1.8. The transverse Pc pulsations at GOES 2 can propagate only into the high-latitude ionosphere. The compressional Pc 3 pulsations at GOES 2 are theoretically expected to propagate across the ambient magnetic field to very low latitudes and to couple with one or more of the followings; (i) a surface wave at the plasmapause (Lpp), (ii) a trapped oscillation of the fast magnetosonic wave in the plasmasphere (L=1.7∿Lpp), (iii) a higher-harmonic standing oscillation of a local field line at mid-latitudes (L=2.0∿Lpp), and (iv) a fundamental standing oscillation at very low latitudes (L=1.1 and 1.7-2.6). Although further research is needed to clarify the wave and propagation characteristics of the low-latitude Pc 3 pulsations, we believe that the compressional Pc 3 magnetic pulsations in the outer magnetosphere are a source of the low-latitude Pc 3 magnetic pulsations.