Disturbances in Sporadic‐E During the Great Solar Eclipse of August 21, 2017

Chen, G.; Wang, J.; Reinisch, B. W.; Li, Yaxian; Gong, Wanlin

doi:10.1029/2020ja028986

Cited by 15 publications

(15 citation statements)

References 70 publications

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“…Ionospheric Sporadic‐E (Es) is a thin layer due to the wind convergence acting on the long‐lived metal ions, and the metal ions response to the solar flux variations very slowly. Both the day‐to‐day variations and the rapid variations during a solar eclipse show the quick response of the f b Es to the changing of solar radiation, implying a certain number of molecular ions also existing in Es layer (Chen et al., 2021; Matsushita & Reddy, 1967; Reddy & Matsushita, 1969). At night, due to the decreasing photoionization, a lot of molecular ions in E‐region have been recombined, but the metal ions in the thin Es layer still persist their old ways, thus the steep density gradient is formed at the edge of the Es layer to induce the higher ∆ f Es values during nighttime (Zhou and Morton, 2005).…”

Section: Analysis and Discussionmentioning

confidence: 99%

Statistical Characteristics of the Low‐Latitude E‐Region Irregularities Observed by the HCOPAR in South China

et al. 2021

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Sporadic-E (Es) between 90 and 120 km is a very special layer of Earth's ionosphere. It is considered as a sporadic concentration of the E-layer plasma into thin layers of high electron density (Mathews, 1998;Whitehead, 1989). It is believed that the wind shear together with the Earth's geomagnetic field compresses the E-region ions into a thin, ion-rich layer, approximately one to two km in thickness (Chu et al., 2014;Cosgrove & Tsunoda, 2002). The steep density gradient in Es creates a favorable environment for gradient drift instability, which is widely believed responsible for the E-region Field-Aligned Irregularities (FAIs) (Ecklund et al., 1981;Kagan & Kelley, 1998;Larsen, 2000). The earliest report of the scattered echoes from E-region FAIs was published in the middle of last century (Bailey et al., 1955). When the Quasi Periodic (QP) scattered echoes from Es layer were recorded by the MU radar (Middle and Upper Atmosphere Radar) in 1989 (Yamamoto et al., 1991), these plasma structures aligned along the geomagnetic fields have drawn a lot of attention of the space physics community. And then the observations of the FAIs were widely carried out all over the world (e.g.,

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Section: Analysis and Discussionmentioning

confidence: 99%

Statistical Characteristics of the Low‐Latitude E‐Region Irregularities Observed by the HCOPAR in South China

et al. 2021

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“…[2,13]. Recently, various studies have used ionosonde data to characterize E s during or after specific events (i.e., solar eclipse [14], tsunami [15], geomagnetic storms [16,17], etc.). Additionally, regional E s occurrence rates have been analyzed in Europe [18], South Korea [19], the United States of America [20], China [21], New Zealand [22], and various locations around the globe [23].…”

Section: Introductionmentioning

confidence: 99%

Comparison of Seasonal foEs and fbEs Occurrence Rates Derived from Global Digisonde Measurements

et al. 2021

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A global climatology of sporadic-E occurrence rates (ORs) based on ionosonde measurements is presented for the peak blanketing frequency, fbEs, and the ordinary mode peak frequency of the layer, foEs. ORs are calculated for a variety of sporadic-E frequency thresholds: no lower limit, 3, 5, and 7 MHz. Seasonal rates are calculated from 64 Digisonde sites during the period 2006–2020 using ionograms either manually or automatically scaled with ARTIST-5. Both foEs and fbEs ORs peak in the Northern Hemisphere during the boreal summer, with a decrease by roughly a factor of 2–3 in fbEs rates relative to foEs rates without a lower threshold on the sporadic-E intensity. This ratio of foEs to fbEs OR increases with increasing sporadic-E intensity, up to a factor of 5 for the 7 MHz threshold. An asymmetry is observed with the Southern Hemisphere peaks during the austral summer, with slightly lower rates compared with the Northern Hemisphere during the boreal summer. A drastic decrease in ORs is observed for the higher intensity thresholds, such that the fbEs occurrence rates for 7 MHz are nearly zero during most locations and seasons. These updated occurrence rates can be used for future statistical comparisons with GPS radio occultation-based sporadic-E occurrence rates.

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“…The E-region electron densities had a 20% decrease ~30 min after the beginning of the partial solar eclipse on 23 September 1987 [33]. During the solar eclipse of 21 August 2017, the E-region electron density in four locations of America was found to have an in-phase decrease and recovered with the eclipse; the maximum density depletion appeared around mid-eclipse [34]. As the recombination of the molecular ions outside the Es layer is faster than that of the metallic ions inside the Es layer [35], the metallic ions inside the Es layer are left to form the high plasma density gradient, which is beneficial to the occurrence of the gradient drift instability to generate FAIs.…”

Section: Discussionmentioning

confidence: 96%

E-Region Field-Aligned Irregularities in the Middle of a Solar Eclipse Observed by a Bistatic Radar

et al. 2022

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The Wuhan Ionospheric Oblique Backscatter Sounding System (WIOBSS) was applied as a bistatic radar to record the ionospheric E-region responses to a solar eclipse on 22 July 2009. The transmitter was located in Wuhan and the receiver was located in Huaian. The receiver observed anomalous echoes with larger Doppler shifts at the farther ranges compared with the echoes reflected by Es. According to the simulated ray propagation paths of the reflected and scattered waves, we considered that the anomalous echoes were scattered by E-region field-aligned irregularities (FAIs). The locations of the FAIs recorded by the WIOBSS were estimated with the International Geomagnetic Reference Field (IGRF) and the observed propagation parameters. These irregularities occurred at around the eclipse maximum and lasted for ~20–40 min. The steep plasma density gradient induced by the fast drop photo ionization under the lunar shadow was beneficial to the occurrence of gradient drift instability to generate the FAIs. They were different from the gravity wave-induced irregularities occurring in the recovery phase of the solar eclipse.

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Disturbances in Sporadic‐E During the Great Solar Eclipse of August 21, 2017

Cited by 15 publications

References 70 publications

Statistical Characteristics of the Low‐Latitude E‐Region Irregularities Observed by the HCOPAR in South China

Statistical Characteristics of the Low‐Latitude E‐Region Irregularities Observed by the HCOPAR in South China

Comparison of Seasonal foEs and fbEs Occurrence Rates Derived from Global Digisonde Measurements

E-Region Field-Aligned Irregularities in the Middle of a Solar Eclipse Observed by a Bistatic Radar

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