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Pilot observations were conducted at Arecibo, Puerto Rico, using an all‐sky, image‐intensified CCD camera system in conjunction with radar, ionosonde, and Global Positioning System (GPS) diagnostic systems during the periods January 19–28, 1993, and February 21 to August 22, 1995. These represent the first use of campaign mode operations of an imager at Arecibo for extended periods of F region observations. The January 1993 period (the so‐called “10‐day run”) yielded a rich data set of gravity wave signatures, perhaps the first case of direct imaging of thermospheric wave train properties in the F region. The 6‐month 1995 campaign revealed two additional optical signatures of F region dynamics. A brightness wave in 6300 Å passing rapidly through the field of view (FOV) has been linked to meridional winds driven by the midnight temperature maximum (MTM) pressure bulge. On May 3, 1995, during a period of geomagnetic activity, a 6300‐Å airglow depletion pattern entered the Arecibo FOV. Such effects represent the optical signatures of equatorial spread F instabilities that rise above the equator to heights near 2500 km, thereby affecting Arecibo's L = 1.4 flux tube.
Mendillo et al. (Tue,) studied this question.