Detection and Description of the Different Ionospheric Disturbances that Appeared during the Solar Eclipse of 21 August 2017

Heng Yang,Enrique Monte Moreno,Manuel Hernández-Pajares

doi:10.3390/rs10111710

Heng Yang, Enrique Monte Moreno + Show 1 more

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https://doi.org/10.3390/rs10111710

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Abstract

This work will provide a detailed characterization of the travelling ionospheric disturbances (TIDs) created by the solar eclipse of 21 August 2017, the shadow of which crossed the United States from the Pacific to the Atlantic ocean. The analysis is done by means of the Atomic Decomposition Detector of Traveling Ionospheric Disturbances (ADDTID) algorithm. This method automatically detects and characterizes multiple TIDs from the global navigation satellite system (GNSS) observation. The set of disturbances generated by the eclipse has a richer and more varied behavior than that associated with the shock wave directly produced by cooling effects of the moon shadow. This can be modeled in part as if the umbra and penumbra of the eclipse were moving cylinders that intersects with variable elevation angle a curved surface. This projection gives rise to regions of equal penumbra with shapes similar to ellipses, with different centers and foci. The result of this is reflected in the time evolution of the TID wavelengths produced by the eclipse, which depend on the vertical angle of the sun with the surface of the earth, and also a double bow wave phenomenon, where the bow waves are generated in advance to the umbra. We show that the delay in the appearance of the disturbances with the transit of the eclipse are compatible with the physical explanations, linked to the different origins of the disturbances and the wavelengths. Finally, we detected a consistent pattern, in location and time of disturbances in advance to the penumbra as a set of medium scale TIDs, which could be hypothesized as soliton waves of the bow wave. In all cases, the detected disturbances were checked visually on the detrended vertical total electron content (TEC) maps.

Highlights

The ionosphere is the Earth’s upper atmosphere primarily ionized by solar radiation and located at the height of ∼50–1000 km
In this work we have described the diverse types of ionospheric disturbances that were generated during the US solar eclipse of 21 August 2017
Due to different patterns of behavior, the travelling ionospheric disturbances (TIDs) in this work have been categorized into the following phases: (a) The time-varying TIDs observed in the early stage, beginning with the arrival of penumbra with 50–75% obscuration

Summary

Introduction

The ionosphere is the Earth’s upper atmosphere primarily ionized by solar radiation and located at the height of ∼50–1000 km. Chimonas and Hines [5] point out that gravity waves generated in middle neutral atmosphere by the eclipse-induced radiative cooling, should build up a bow wave propagating up to E-F region of ionosphere and forming TIDs when the moon’s shadow sweeps at supersonic speed. Davis and Da Rosa [9], Cheng et al [10] and Zerefos et al [11] observe the wavelike ionospheric disturbances of atmospheric gravity waves at the D-F1 region during the solar occultation by the moon, but show weak and ambiguous correlations with the bow wave characteristics due to the difficult observation conditions and the existence of other factors that have a greater influence, such as geomagnetic activity, regular solar terminator, etc. Liu et al [12] presented the observations of bow and stern waves in the ionosphere induced by the solar eclipse of 22 July 2009, the observations were to a certain extend incomplete because the GNSS network only partially covered the affected region

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