Observations of polar patches generated by solar wind Alfven wave couplingto the dayside magnetosphere

A long series of polar patches was observed by ionosondes and an all-sky im ager during a disturbed period (K-p = 7- and IMF B-z < 0). The ionosondes m easured electron densities of up to 9 x 10(11) m(-3) in the patch center, a n increase above the density minimum between patches by a factor of similar to 4.5. Bands of F-region irregularities generated at the equatorward edge of the patches were tracked by HF radars. The backscatter bands were swept northward and eastward across the polar cap in a fan-like formation as the afternoon convection cell expanded due to the IMF B-y > 0. Near the north magnetic pole, an all-sky imager observed the 630-nm emission patches of a distinctly band-like shape drifting northeastward to eastward. The 630-nm e mission patches were associated with the density patches and backscatter ba nds. The patches originated in, or near, the cusp footprint where they were formed by convection bursts (flow channel events, FCEs) structuring the so lar EUV-produced photoionization and the particle-produced auroral/cusp ion ization by segmenting it into elongated patches. Just equatorward of the cu sp footprint Pc5 field line resonances (FLRs) were observed by magnetometer s, riometers and VHF/HF radars. The AC electric field associated with the F LRs resulted in a poleward-progressing zonal flow pattern and backscatter b ands. The VHF radar Doppler spectra indicated the presence of steep electro n density gradients which, through the gradient drift instability, can lead to the generation of the ionospheric irregularities found in patches. The FLRs and FCEs were associated with poleward-progressing DPY currents (Hall currents modulated by the IMF B-y) and riometer absorption enhancements. Th e temporal and spatial characteristics of the VHF backscatter and associate d riometer absorptions closely resembled those of poleward moving auroral f orms (PMAFs). In the solar wind, IMP 8 observed large amplitude Alfven wave s that were correlated with Pc5 pulsations observed by the ground magnetome ters, riometers and radars. It is concluded that the FLRs and FCEs that pro duced patches were driven by solar wind Alfven waves coupling to the daysid e magnetosphere. During a period of southward IMF the dawn-dusk electric fi eld associated with the Alfven waves modulated the subsolar magnetic reconn ection into pulses that resulted in convection flow bursts mapping to the i onospheric footprint of the cusp.