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The effect of the August 21, 2017 solar eclipse on the ionosphere is modeled using Sami3 is Also a Model of the Ionosphere (SAMI3). Due to the density gradient geometry that arises from the solar e...

The total solar eclipse over the continental United States on 21 August 2017 offered a unique opportunity to study the dependence of the ionospheric density and morphology on incident solar radiation at different local times. The Super Dual Auroral Radar Network (SuperDARN) radars in Christmas Valley, Oregon, and Fort Hays, Kansas, are located slightly southward of the line of totality; they both made measurements of the eclipsed ionosphere. The received power of backscattered signal decreases during the eclipse, and the slant ranges from the westward looking radar beams initially increase and then decrease after totality. The time scales over which these changes occur at each site differ significantly from one another. For Christmas Valley the propagation changes are fairly symmetric in time, with the largest slant ranges and smallest power return occurring coincident with the closest approach of totality to the radar. The Fort Hays signature is less symmetric. In order to investigate the underlying processes governing the ionospheric eclipse response, we use a ray-tracing code to simulate SuperDARN data in conjunction with different eclipsed ionosphere models. In particular, we quantify the effect of the neutral wind velocity on the simulated data by testing the effect of adding/removing various neutral wind vector components. The results indicate that variations in meridional winds have a greater impact on the modeled ionospheric eclipse response than do variations in zonal winds. The geomagnetic field geometry and the line-of-sight angle from each site to the Sun appear to be important factors that influence the ionospheric eclipse response. National Aeronautics and Space Administration (NASA)National Aeronautics & Space Administration (NASA) [NNX17AH70G]; National Science Foundation (NSF)National Science Foundation (NSF) [AGS-1552188, AGS-1341925, AGS-1934997, AGS-1341918, AGS-1935110]; Virginia Space Grant Consortium (VSGC) 2015-2016 Undergraduate Research Fellowship; 2017-2018 VSGC Graduate Research Fellowship; 2018-2019 VSGC Graduate Research Fellowship Published version Funding for this research was provided by National Aeronautics and Space Administration (NASA) grant NASA #NNX17AH70G, National Science Foundation (NSF) grant NSF #AGS-1552188, a Virginia Space Grant Consortium (VSGC) 2015-2016 Undergraduate Research Fellowship, and 2017-2018 and 2018-2019 VSGC Graduate Research Fellowships. The ray tracing results presented in this paper were obtained using the HF propagation toolbox, PHaRLAP, created by Dr. Manuel Cervera, Defence Science and Technology Organisation, Australia(manuel.cervera@dsto.defence.gov.au). Funding for operations of U.S. SuperDARN radars is provided by NSF grants AGS-1341925 and AGS-1934997 (for Dartmouth College) and AGS-1341918 and AGS-1935110 (for Virginia Tech). Data analysis and visualizations in this paper were generated by employing several free open-source software packages including matplotlib (Hunter, 2007), iPython (Perez & Granger, 2007), SciPy (Virtanen et al., 2020), NumPy (van derWalt et al., 2011), and DaViTPy (Ribeiro et al., 2020), among others. Note that DaViTPy was depreciated upon the release of pyDARN (Schmidt et al., 2020) in May 2020, after the work presented in this paper was completed. Also, we acknowledge the contributions of New Jersey Institute of Technology Eclipse Team (especially Joshua Vega, Joshua Katz, and Nathaniel Frissell) to our initial development of supporting Matlab functions for the use of SAMI3 output files with PHaRLAP.

The design of the first retarding potential analyzer (RPA) built specifically for use on resource-limited cubesat platforms is described. The size, mass, and power consumption are consistent with the limitations of a nano-satellite, but the performance specifications are commensurate with those of RPAs flown on much larger platforms. The instrument is capable of measuring the ion density, temperature, and the ram component of the ion velocity in the spacecraft reference frame, while also providing estimates of the ion composition. The mechanical and electrical designs are described, as are the operating modes, command and data structure, and timing scheme. Test data obtained using an ion source inside a laboratory vacuum chamber are presented to validate the performance of the new design.