Coherent and incoherent scatter radar observations during intense mid‐latitude spread F

Abstract

An intense mid‐latitude spread‐F event occurred over Puerto Rico during the night of February 17, 1998. Simultaneous observations were made with the Cornell University Portable Radar Interferometer (CUPRI) located near Isabela, PR, the University of Illinois VHF radar located at Salinas, PR, GPS receivers at Isabela and St. Croix, measuring total electron content, the Arecibo incoherent scatter radar, and the Cornell All‐Sky imager located at the Arecibo Observatory. This was the first time that such a broad range of complementary instrumentation captured a mid‐latitude spread‐F space weather event. It was the first (and still only) time that a spread‐F event over the Caribbean exhibited large Doppler shifts in the VHF spectra. This event was characterized with multiple filaments that initially produced receding Doppler velocities exceeding 300 m/s as seen by CUPRI and the Illinois radar. The Arecibo incoherent scatter radar recorded line‐of‐sight velocities exceeding 100 m/s that moved the F‐layer peak to over 400‐km altitude. Airglow images of 630.0 nm emissions from F‐region heights showed depleted structures oriented southeast to northwest. The large velocities observed with the radars suggest that we caught this event in a stage of explosive development. It is interesting that the first fully documented Caribbean event occurred during a magnetically active period.