{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,22]],"date-time":"2025-12-22T10:51:28Z","timestamp":1766400688961,"version":"build-2065373602"},"reference-count":49,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2024,4,29]],"date-time":"2024-04-29T00:00:00Z","timestamp":1714348800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"NASA","award":["80NSSC20K0189","80NSSC19K0278","80NSSC19K0835","80NSSC19K0356","80NSSC20K1350","NNH19ZDA001N-HTMS","80GSFC18C0061","80NSSC22M0163","1852977"],"award-info":[{"award-number":["80NSSC20K0189","80NSSC19K0278","80NSSC19K0835","80NSSC19K0356","80NSSC20K1350","NNH19ZDA001N-HTMS","80GSFC18C0061","80NSSC22M0163","1852977"]}]},{"name":"NASA DRIVE Science Center for Geospace Storms (CGS)","award":["80NSSC20K0189","80NSSC19K0278","80NSSC19K0835","80NSSC19K0356","80NSSC20K1350","NNH19ZDA001N-HTMS","80GSFC18C0061","80NSSC22M0163","1852977"],"award-info":[{"award-number":["80NSSC20K0189","80NSSC19K0278","80NSSC19K0835","80NSSC19K0356","80NSSC20K1350","NNH19ZDA001N-HTMS","80GSFC18C0061","80NSSC22M0163","1852977"]}]},{"name":"National Science Foundation","award":["80NSSC20K0189","80NSSC19K0278","80NSSC19K0835","80NSSC19K0356","80NSSC20K1350","NNH19ZDA001N-HTMS","80GSFC18C0061","80NSSC22M0163","1852977"],"award-info":[{"award-number":["80NSSC20K0189","80NSSC19K0278","80NSSC19K0835","80NSSC19K0356","80NSSC20K1350","NNH19ZDA001N-HTMS","80GSFC18C0061","80NSSC22M0163","1852977"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The ionosphere equatorial ionization anomaly (EIA) is usually characterized by two plasma density maxima in the Earth\u2019s equatorial region. Merged EIA (MEIA) is a unique phenomenon in the evolution of the EIA. Currently, the occurrence characteristics of MEIA are still not well understood. In this study, we investigate the occurrence characteristics of nighttime MEIA using NASA Global-scale Observations of the Limb and Disk (GOLD) observations between October 2018 and the end of 2023. We found that the occurrence of nighttime MEIA exhibits solar cycle, seasonal, and local time variations. The occurrence rate of the MEIA is inversely dependent on solar activity. Occurrence of the MEIA maximizes near the equinoxes, with a primary (secondary) low occurrence rate near the June (December) solstice. In addition, occurrences of the MEIA are suppressed during the pre-reversal enhancement (PRE), resulting in relatively fewer events. Furthermore, it was found that the occurrence of the MEIA is not significantly dependent on the strength of geomagnetic activity. As far as we know, this study represents the first instance of utilizing observations from GOLD observations to investigate the characteristics of MEIA occurrences and their correlations with solar activity, season, and local time.<\/jats:p>","DOI":"10.3390\/rs16091575","type":"journal-article","created":{"date-parts":[[2024,4,29]],"date-time":"2024-04-29T04:26:16Z","timestamp":1714364776000},"page":"1575","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Occurrence Characteristics of Nighttime Merged EIA Based on NASA GOLD Observations from 2018 to 2023"],"prefix":"10.3390","volume":"16","author":[{"given":"Kun","family":"Wu","sequence":"first","affiliation":[{"name":"High Altitude Observatory, NSF National Center for Atmospheric Research, Boulder, CO 80301, USA"}]},{"given":"Liying","family":"Qian","sequence":"additional","affiliation":[{"name":"High Altitude Observatory, NSF National Center for Atmospheric Research, Boulder, CO 80301, USA"}]}],"member":"1968","published-online":{"date-parts":[[2024,4,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"691","DOI":"10.1038\/157691a0","article-title":"Two anomalies in the ionosphere","volume":"157","author":"Appleton","year":"1946","journal-title":"Nature"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2003","DOI":"10.1038\/1842003a0","article-title":"Two anomalies in the behaviour of the F2 layer of the ionosphere","volume":"184","author":"Croom","year":"1959","journal-title":"Nature"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"89","DOI":"10.1016\/0021-9169(60)90081-7","article-title":"The equatorial f-region of the ionosphere","volume":"18","author":"Duncan","year":"1960","journal-title":"J. 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