Digital all-sky polarization imaging of the total solar eclipse on 21 August 2017 in Rexburg, Idaho, USA

Abstract

All-sky polarization images were measured from sunrise to sunset and during a cloud-free totality on 21 August 2017 in Rexburg, Idaho using two digital three-camera all-sky polarimeters and a time-sequential liquid-crystal-based all-sky polarimeter. Twenty-five polarimetric images were recorded during totality, revealing a highly dynamic evolution of the distribution of skylight polarization, with the degree of linear polarization becoming nearly zenith-symmetric by the end of totality. The surrounding environment was characterized with an infrared cloud imager that confirmed the complete absence of clouds during totality, an AERONET solar radiometer that measured aerosol properties, a portable weather station, and a hand-held spectrometer with satellite images that measured surface reflectance at and near the observation site. These observations confirm that previously observed totality patterns are general and not unique to those specific eclipses. The high temporal image resolution revealed a transition of a neutral point from the zenith in totality to the normal Babinet point just above the Sun after third contact, providing the first indication that the transition between totality and normal daytime polarization patterns occurs over of a time period of approximately 13 s.

Polarimetry for Bionic Geolocation and Navigation Applications: A Review

“…The maximum value of DoLP identically equals 1 in the Rayleigh single scattering model, but the actual DoLP in the celestial dome scarcely reaches 1 because of the multiple scattering effects [92]. Moreover, the existence of four neutral points where the emitted light is unpolarized (DoLP equals 0) has been verified and studied widely [70,[95][96][97], but it cannot be correctly described under the framework of the Rayleigh scattering theory. To model depolarization phenomena, Berry et al [98] proposed a singular value model to describe the existence of neutral points, and Hannay [99] presented a model to characterize the multiple scattering.…”

“…Jensen et al [195] established a physical model of the night skylight and analyzed the main components of the skylight as well as the influence of different light sources on the night imaging effect. In addition, the atmospheric polarization patterns during eclipses were also studied [97,183,196]. The mechanism of the navigation of aquatic animals using polarized skylight was also being researched [11,52].…”

Reduction of Spectral Radiance Reflectance During the Annular Solar Eclipse of 21 June 2020 Observed by EPIC

“…During the recent total eclipse on 21 August 2017, Bernhard and Petkov (2019) made surface spectral solar irradiance observations and performed 3D radiative transfer simulations; Ockenfuβ et al (2020) further used 3D radiative transfer simulations for understanding the impact of surface spectral albedo, ozone vertical distribution and surrounding mountains on surface spectral irradiance observed by Bernhard and Petkov (2019); Wen et al (2020) used ground-based pyranometer observations to estimate the impact of solar eclipse on surface broadband irradiance reduction; Calamas et al (2018) studied the impact of the eclipse on surface irradiance and ambient temperature; and Eshelman et al (2020) studied impact of total solar eclipse on all-sky polarization images. Gedzelman (2020) showed that the sunlit tops of cloud layers and arctic sea ice near the umbra appeared salmon-brown when viewed from airplanes or satellite during the 21 August 2017 as well as 2 July 2019 eclipse.…”