Variations of Total Electron Content and Illuminance Observed by Low-Cost Portable Instruments During the 2024 Total Solar Eclipse

The 2024 solar eclipse is one of the astronomical spectacles that has attracted worldwide observers in the last decade.On Apr 8, 2024, we deployed low-cost portable instruments at University of Texas at Arlington (UTA) and University of Texas at Dallas (UTD) in the United States, including two GNSS receivers for the ionospheric electron density and an all-sky imager to optically capture the phenomenon.The stand-alone instruments are all built with a Raspberry Pi and capable of continuous observation for at least 24 hours.As references, a digital lux meter was installed at UTA for illuminance observations and a Septentrio GNSS receiver was installed at UTD for co-location observations.The depletion of vertical total electron content started from southwest toward northeast as the lunar shadow moved across the local zenith.All-sky images show that clouds predominantly moved eastward before the partial eclipse.About 30 minutes before totality, higher clouds appeared and propagated southward.The red, green, and blue light curves depleted simultaneously during the totality, but the development progressed at different paces during a cloudless sunset at the same location.The differences result mainly from the atmospheric scattering of light at different frequencies.A numerical model is proposed to estimate illuminance with the RGB values of all the available all-sky images.The result indicates that the illuminance dropped to 1/10000 of that of a local noon during maximum obscuration.We also investigate the wave-like features captured in the all-sky images and compare with the perturbations observed by the GNSS receivers.