Dynamical effects of geomagnetic storms and substorms in the middle-latitude ionosphere: An observational campaign

An observational campaign was conducted in October 1992 for similar to 36 h ours, at three high- to low-latitude sites near 75 degrees W longitude (Son dre Stromfjord, Millstone Hill, and Arecibo). Vector plasma drift velocitie s are obtained using the incoherent scatter radar technique at each site, N eutral winds were measured using a Fabry-Perot interferometer, and 6300 Ang strom airglow structures were imaged at the midlatitude site. Electric fiel ds and meridional winds for the period were;perturbed when magnetic storms and substorms occurred on the day and night of the campaign. The penetratio n of magnetospheric electric field and the following interplays between ion ospheric electrodynamics and thermospheric wind perturbations in the midlat itude ionosphere are assessed using the multidiagnostic measurements. Evide nce for traveling atmospheric disturbances (TADs) and large-scale gravity w aves induced by auroral heating effects upon the thermosphere is identified . Diffuse aurora and a stable aurora red (SAR) are were observed from Mills tone Hill during the night of the campaign. The SAR are moved southward whe n there were westward electric field perturbations, indicating plasmasphere compression in the postmidnight sector under substorm conditions. The SAR are location was used to infer the motion of the magnetospheric shielding l ayer past the Millstone Hill site. Ionospheric F region disturbances in h(m )F(2), NmF2, and total electron content were driven by the observed dynamic s, exhibiting a complex mix of wind and electric field perturbations. While standard model episodes of penetration and shielding/overshielding occurre d during the daytime event, such unambiguous clarifications were far less o bvious during the nighttime event. This is perhaps due to the prolonged per iod of moderate geomagnetic activity that served as the background conditio ns for the substorms that occurred during the campaign.