Radar chain study of the May, 1995 storm

We summarize the main features of the ionospheric F region as observed by the Sondrestrom, Millstone Hill, Arecibo, and Jicamarca incoherent scatter radars during the 1-5 May, 1995 CEDAR Storm Study interval. This paper apparently represents the first study of a major storm interval using the current incoherent scatter radar chain supported by the U.S. National Science Foundation. We focus most attention on 2-3 May, and include additional data from IMP-8, the St. John's magnetometer, SuperDARN, and global total electron content (TEC) maps from GPS. Three intervals of likely penetration of magnetospheric electric field from high to low latitude are identified on 2 May. A unique feature of this storm are the strong daytime equatorward wind surges in the neutral meridional wind observed at Millstone Hill. The first of these (at 14 UT on 2 May) is apparently due to a travelling atmospheric disturbance launched by intense frictional and Joule heating as observed at Sondrestrom. An evening enhancement in NmF(2) (the 'dusk effect') is typically seen only on the first day of a geomagnetic storm. However, during this storm a strong dusk effect is seen at Millstone Hill on 2, 3, and 4 May, associated with the equatorward wind surges. A penetrating eastward electric field also contributed to the dusk effect on 2 May. A large rise in hmF(2) at Arecibo near 0000 UT on 3 May is due to the same eastward electric field, which penetrates to the equator, causing a strong upward plasma drift at Jicamarca. This apparently results in a poleward expansion of the equatorial anomaly zones as seen in GPS total electron content, and an increase in NmF(2) at Arecibo to the largest value seen at midnight in several years. (C) 1999 Elsevier Science Ltd. All rights reserved.