Characterizing the Ionosphere Using a Commercial Off the Shelf Software Defined Radio System

On August 21, 2017, there will be a total solar eclipse over the continental United States (US). Solar eclipses offer a way to study the dependence of the ionospheric density and morphology on incident solar radiation. There are significant differences between the conditions during a solar eclipse and the conditions normally experienced at sunset and sunrise, including the east-west motion of the eclipse terminator, the speed of the transition, and the continued visibility of the corona throughout the eclipse interval. Taken together, these factors imply that unique ionospheric responses may be witnessed during eclipses including variations in the density and altitude of the F2 peak. In order to study these changes, we will establish four temporary field stations along the path of totality to track the maximum usable frequency (MUF) across the US over the course of the eclipse. Each field station shall consist of a commercial off the shelf (COTS) software defined radio (SDR) transceiver, a laptop computer running automatic link establishment (ALE) software, a Global Positioning System (GPS) receiver for timing, and a COTS antenna. Custom ALE software will automate the sites’ operation during the experiment to determine the MUF. As a validation test prior to the eclipse, we established three sites along the east coast to confirm that the SDRs are capable of inferring ionospheric conditions. The preliminary results characterize the effects of the sunrise/sunset terminator on our system’s measurements as well as the change in foF2 during different seasons and under different geomagnetic conditions.