{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,25]],"date-time":"2026-03-25T23:52:27Z","timestamp":1774482747714,"version":"3.50.1"},"reference-count":42,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2021,2,2]],"date-time":"2021-02-02T00:00:00Z","timestamp":1612224000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The dynamics of ionospheric troughs during intense geomagnetic storms is considered in this paper. The study is based on electron density measurements at CHAMP satellite altitudes of 405\u2013465 km in the period from 2000 to 2002. A detailed analysis of four storms with Kp from 5+ to 9\u2212 is presented. Three troughs were identified: sub-auroral, mid-latitude, and low-latitude. The sub-auroral trough is usually defined as the main ionospheric trough (MIT). The mid-latitude trough is observed equatorward of the MIT and is associated with the magnetospheric ring current; therefore, it is named the ring ionospheric trough (RIT). The RIT appears at the beginning of the storm recovery phase at geomagnetic latitudes of 40\u201345\u00b0 GMLat (L = 1.75\u20132.0) and exists, for a long time, at the late stage of the recovery phase at latitudes of the residual ring current 50\u201355\u00b0 GMLat (L ~ 2.5\u20133.0). The low-latitude trough (LLT) is discovered for the first time. It forms only during great storms at the latitudes of the internal radiation belt (IRB), 34\u201345\u00b0 GMLat (L = 1.45\u20132.0). The LLT\u2019s lowest latitude of 34\u00b0 GMLat was recorded in the night sector (2\u20133 LT). The occurrence probability and position of the RIT and LLT depend on the hemisphere and longitude.<\/jats:p>","DOI":"10.3390\/rs13030534","type":"journal-article","created":{"date-parts":[[2021,2,2]],"date-time":"2021-02-02T13:01:12Z","timestamp":1612270872000},"page":"534","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Sub-Auroral, Mid-Latitude, and Low-Latitude Troughs during Severe Geomagnetic Storms"],"prefix":"10.3390","volume":"13","author":[{"given":"Alexander","family":"Karpachev","sequence":"first","affiliation":[{"name":"Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radiowave Propagation, (IZMIRAN), 4, Kaluzhskoe Hwy, Troitsk, 108840 Moscow, Russia"}]}],"member":"1968","published-online":{"date-parts":[[2021,2,2]]},"reference":[{"key":"ref_1","first-page":"804","article-title":"Magnetospheric disturbances and the associated dynamics of ionospheric electrojets, auroras, and plasmapause","volume":"27","author":"Khorosheva","year":"1987","journal-title":"Geomagn. Aeron."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"543","DOI":"10.1134\/S0016793207050015","article-title":"Relation of geomagnetic disturbances to the dynamics of the magnetosphere and the parameters of the interplanetary medium","volume":"47","author":"Khorosheva","year":"2007","journal-title":"Geomagn. Aeron."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"5692","DOI":"10.1029\/JA088iA07p05692","article-title":"Systematics of the equatorial diffuse auroral boundary","volume":"88","author":"Gussenhofen","year":"1983","journal-title":"J. Geophys. Res."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"489","DOI":"10.1029\/JA084iA02p00489","article-title":"Topside ionospheric trough morphology: Occurrence frequency and diurnal, seasonal and altitude variations","volume":"84","author":"Ahmed","year":"1979","journal-title":"J. Geophys. Res."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"5707","DOI":"10.1029\/90JA02751","article-title":"Storm time electric field penetration observed at mid-latitude","volume":"96","author":"Yeh","year":"1991","journal-title":"J. Geophys. Res."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"86","DOI":"10.1029\/JA080i001p00086","article-title":"Satellite and ground observations of magnetospheric VLF hiss associated with the severe magnetic storm on 25\u201327 May 1967","volume":"80","author":"Hayakawa","year":"1967","journal-title":"J. Geophys. Res."},{"key":"ref_7","first-page":"469","article-title":"On the great enhancement of the line [OI] 6300 in the aurora at Niigata on 11 February 1958","volume":"12","author":"Hikosaka","year":"1958","journal-title":"Rep. Ionos. Res. Jpn."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"26091","DOI":"10.1029\/2001JA000073","article-title":"A stable auroral red arc observed over Japan after an interval of very weak solar wind","volume":"106","author":"Shiokawa","year":"2001","journal-title":"J. Geophys. Res."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Hayakawa, H., Ebihara, Y., Hand, D.P., Hayakawa, S., Kumar, S., Mukherjee, S., and Veenadhari, B. (2018). Low-latitude aurorae during the extreme space weather events in 1859. Astrophys. J.","DOI":"10.3847\/1538-4357\/aae47c"},{"key":"ref_10","first-page":"54","article-title":"Subauroral ionosphere in SUNDIAL period on June, 1987 on Cosmos-1809 satellite data","volume":"32","author":"Deminov","year":"1992","journal-title":"Geomagn. Aeron."},{"key":"ref_11","first-page":"54","article-title":"Dynamics of midlatitude ionospheric trough during storms 1. A qualitative picture","volume":"35","author":"Deminov","year":"1995","journal-title":"Geomagn. Aeron."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"141","DOI":"10.1016\/0273-1177(95)00706-K","article-title":"Dynamics of the ionization troughs in the night-time subauroral F-region during geomagnetic storms","volume":"17","author":"Deminov","year":"1996","journal-title":"Adv. Space Res."},{"key":"ref_13","first-page":"45","article-title":"The dynamics of the mid-latitude trough during the storms: Recovery phase","volume":"35","author":"Deminov","year":"1996","journal-title":"Geomagn. Aeron."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1016\/0273-1177(95)00928-0","article-title":"Model of the mid-latitude ionospheric trough on the base of Cosmos-900 and Intercosmos-19 satellites data","volume":"18","author":"Karpachev","year":"1996","journal-title":"Adv. Space Res."},{"key":"ref_15","first-page":"57","article-title":"The characteristics of the ring ionospheric trough","volume":"41","author":"Karpachev","year":"2001","journal-title":"Geomagn. Aeron."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Karpachev, A.T. (2020). Dynamics of main and ring ionospheric troughs at the recovery phase of storms\/substorms. J. Geophys. Res.","DOI":"10.1029\/2020JA028079"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"211","DOI":"10.1007\/s00585-996-0211-7","article-title":"Mechanism of the electron density depletion in the SAR arc region","volume":"14","author":"Pavlov","year":"1996","journal-title":"Ann. Geophys."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1867","DOI":"10.1016\/0032-0633(69)90161-5","article-title":"Electron density and temperature in the vicinity of the 29 September 1967 middle latitude red arc","volume":"17","author":"Norton","year":"1969","journal-title":"Planet. Space Sci."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"14343","DOI":"10.1029\/JA093iA12p14343","article-title":"Ring current development during the great geomagnetic storm of February 1986","volume":"93","author":"Hamilton","year":"1988","journal-title":"J. Geophys. Res."},{"key":"ref_20","first-page":"111","article-title":"The ring current and particle precipitation near plasmapause","volume":"31","author":"Hultqvist","year":"1975","journal-title":"Ann. Geophys."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"8039","DOI":"10.1029\/2019JA026631","article-title":"Variations in the winter troughs\u2019 position with local time, longitude, and solar activity in the Northern and Southern hemispheres","volume":"124","author":"Karpachev","year":"2019","journal-title":"J. Geophys. Res."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"950","DOI":"10.1016\/j.asr.2018.09.038","article-title":"Longitudinal variations of the ionospheric trough position","volume":"63","author":"Karpachev","year":"2018","journal-title":"Adv. Space Res."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"99","DOI":"10.1016\/0032-0633(83)90034-X","article-title":"Location and source of ionospheric high latitude troughs","volume":"31","author":"Grebowsky","year":"1983","journal-title":"Planet. Space Sci."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"812","DOI":"10.1134\/S0016793211050070","article-title":"Morphology and causes of the Weddell sea anomaly","volume":"51","author":"Karpachev","year":"2011","journal-title":"Geomagn. Aeron."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"2020","DOI":"10.1016\/j.asr.2014.12.032","article-title":"Spatial features of Weddell Sea and Yakutsk anomalies in foF2 diurnal variations during high solar activity periods: Interkosmos-19 satellite and ground-based ionosonde observations, IRI reproduction and GSM TIP model simulation","volume":"55","author":"Klimenko","year":"2015","journal-title":"Adv. Space Res."},{"key":"ref_26","first-page":"A02306","article-title":"Investigating the relationships among the South Atlantic Magnetic Anomaly, southern nighttime midlatitude trough, and nighttime Weddell Sea Anomaly during southern summer","volume":"114","author":"Horvath","year":"2009","journal-title":"J. Geophys. Res."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"625","DOI":"10.1134\/S0016793210050063","article-title":"Seasonal and diurnal (UT) variation in the boundaries of the auroral precipitation and polar cup","volume":"50","author":"Vorobjev","year":"2010","journal-title":"Geomagn. Aeron."},{"key":"ref_28","first-page":"A03302","article-title":"Longitudinal variations of nighttime electron auroral precipitation in both the Northern and Southern hemispheres from the TIMED global ultraviolet imager","volume":"116","author":"Luan","year":"2011","journal-title":"J. Geophys. Res."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"6708","DOI":"10.1029\/JA077i034p06708","article-title":"Observations suggesting weak pitch angle diffusion of protons","volume":"77","author":"Berg","year":"1972","journal-title":"J. Geophys. Res."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"3753","DOI":"10.1029\/JZ072i015p03753","article-title":"On the extraterrestrial ring current during geomagnetic storms","volume":"72","author":"Frank","year":"1967","journal-title":"J. Geophys. Res."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"867","DOI":"10.5194\/angeo-26-867-2008","article-title":"Storm-time ionization enhancements at the topside low-latitude ionosphere","volume":"26","author":"Dmitriev","year":"2008","journal-title":"Ann. Geophys."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1134\/S0010952511060062","article-title":"Relaxation of electron and proton radiation belts of the Earth after strong magnetic storms","volume":"50","author":"Lazutin","year":"2012","journal-title":"Cosm. Res."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1007\/s11214-017-0452-7","article-title":"Space weather effects in the Earth\u2019s radiation belts","volume":"214","author":"Baker","year":"2018","journal-title":"Space Sci. Rev."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"2311","DOI":"10.1016\/S0273-1177(99)00514-1","article-title":"Model of the slot region of Earth\u2019s electron radiation belt depending on the heliospheric parameters","volume":"25","author":"Dmitriev","year":"2000","journal-title":"Adv. Space Res."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"489","DOI":"10.1023\/B:COSM.0000046230.62353.61","article-title":"Magnetic storms in October 2003","volume":"42","author":"Panasyuk","year":"2004","journal-title":"Cosm. Res."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"L03S06","DOI":"10.1029\/2004GL021502","article-title":"Response of the inner radiation belt to the violent Sun-Earth connection events of October\u2013November 2003","volume":"32","author":"Looper","year":"2005","journal-title":"Geophys. Res. Lett."},{"key":"ref_37","first-page":"A03305","article-title":"Satellite observations of electric fields in the South Atlantic anomaly region during the July 2000 magnetic storm","volume":"110","author":"Lin","year":"2005","journal-title":"J. Geophys. Res."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1241","DOI":"10.1016\/j.jastp.2006.09.012","article-title":"Conjugate localized enhancement of total electron content at low latitudes in the American sector","volume":"69","author":"Foster","year":"2007","journal-title":"J. Atmos. Sol. Terr. Phys."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"591","DOI":"10.1016\/0032-0633(88)90028-1","article-title":"Electron (0.19\u20133.2 MeV) and proton (0.58\u201335 MeV) precipitations observed by OHZORA satellite at low zones L = 1.6\u20131.8","volume":"36","author":"Nagata","year":"1988","journal-title":"Planet. Space Sci."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1992","DOI":"10.1016\/j.asr.2003.03.078","article-title":"Altitude distribution analysis of electron fluxes at L = 1.2\u20131.8","volume":"36","author":"Grachev","year":"2005","journal-title":"Adv. Space Res."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"307","DOI":"10.1007\/s10604-005-0050-4","article-title":"Fluxes of quasi-trapped electrons with energies > 0.08 MeV in the near-Earth space on drift shells L < 2","volume":"43","author":"Bogomolov","year":"2005","journal-title":"Cosm. Res."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"733","DOI":"10.1016\/j.pss.2011.02.010","article-title":"Latitudinal profile of UV nightglow and electron precipitation","volume":"59","author":"Dmitriev","year":"2011","journal-title":"Planet. Space Sci."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/3\/534\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T05:19:02Z","timestamp":1760159942000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/3\/534"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,2,2]]},"references-count":42,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2021,2]]}},"alternative-id":["rs13030534"],"URL":"https:\/\/doi.org\/10.3390\/rs13030534","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,2,2]]}}}