Other
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufmsm12a0477f&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #SM12A-0477
Other
2407 Auroral Ionosphere (2704), 2439 Ionospheric Irregularities, 2724 Magnetopause, Cusp, And Boundary Layers, 2736 Magnetosphere/Ionosphere Interactions, 2752 Mhd Waves And Instabilities
Scientific paper
From the analysis of search coil magnetometer data obtained at Automatic Geophysical Observatories (AGOs) and South Pole station in the Antarctic, it is found that there are two types of transient Pc 1-2 waves associated with the passage of traveling convection vortices (TVCs). The first type is transient narrowband Pc 1 waves with mid-frequencies of 0.2 - 0.6 Hz, bandwidths of 0.1 - 0.2 Hz, and durations of typically about 5 min. This type of Pc 1 occurs in the downward field-aligned current region of TCVs, and occasionally shows a falling tone structure as changing the mid-frequencies from 0.3 - 0.4 Hz to 0.1 - 0.2 Hz over the duration of Pc 1. The second type is wideband Pc 1-2 bursts which occur around the poleward edge of upward field-aligned current region. The Pc 1-2 burst region is found to correspond to the region of fast poleward convection flows with intense HF radar backscatter. Based on these characteristics, we will propose the generation mechanisms of these two types of TCV-related transient Pc 1-2 waves. The narrowband Pc 1 waves would be generated by the electromagnetic ion cyclotron (EMIC) instability in the outer magnetosphere adjacent to LLBL. Kataoka et al. [2002] suggested that the main source of TCVs is the formation of hot flow anomalies (HFAs) due to the arrival of solar wind tangential discontinuities. The outward motion of the magnetopause caused by the formation of HFAs would reduce the frequency of ion cyclotron waves. On the other hand, it is likely that the wideband Pc 1-2 bursts are turbulent dispersive Alfven waves generated by localized field-aligned currents. The observed intense HF backscatter can be attributed to F-region irregularities produced by the time-varying electric field of these Pc 1-2 bursts, as suggested by Andre et al. [1999].
Fukunishi Hiroshi
Kataoka Ryuho
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