TITLE:   South American observations of equatorial spread F with all-sky imagers

ABSTRACT:   Equatorial spread F (ESF) is the name given to observational signatures caused by plasma irregularities occurring in the nighttime ionosphere near the Earth's magnetic equator. ESF scale sizes cover a wide range, from hundreds of kilometers down to centimeters. As a result, ESF can degrade the performance of technological assets such as satellite-based systems used for global navigation (e.g. GPS) and communication. The main drivers of ESF are well studied yet the causes of day-to-day variability and the connection between the large scale structures and small scale irregularities is not fully understood. Boston University has a network of all-sky imagers (ASI) that are used to examine a variety of ionospheric processes. We use three of these imagers in South America to observe large scale ESF structures. One ASI is located at the Jicamarca Radio Observatory which allows for concurrent measurements with other radar and other instruments at the magnetic equator. The other two ASIs are in Colombia and Argentina at approximately geomagnetic conjugate locations. In this presentation I will focus on three main results from the last few years of observations with these ASIs. I will discuss (1) the relationship between the large scale depletions of ESF and associated small scale irregularities observed with radar, (2) the grouping of bottomside ESF depletions, and (3) the morphology of conjugate ESF depletions.