{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,5]],"date-time":"2026-05-05T13:35:08Z","timestamp":1777988108398,"version":"3.51.4"},"reference-count":42,"publisher":"MDPI AG","issue":"23","license":[{"start":{"date-parts":[[2021,12,2]],"date-time":"2021-12-02T00:00:00Z","timestamp":1638403200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100006769","name":"Russian Science Foundation","doi-asserted-by":"publisher","award":["20-12-00197"],"award-info":[{"award-number":["20-12-00197"]}],"id":[{"id":"10.13039\/501100006769","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002261","name":"Russian Foundation for Basic Research","doi-asserted-by":"publisher","award":["19-02-00343"],"award-info":[{"award-number":["19-02-00343"]}],"id":[{"id":"10.13039\/501100002261","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002261","name":"Russian Foundation for Basic Research","doi-asserted-by":"publisher","award":["20-32-70198"],"award-info":[{"award-number":["20-32-70198"]}],"id":[{"id":"10.13039\/501100002261","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100009917","name":"United States Naval Research Laboratory","doi-asserted-by":"publisher","award":["6.1 Basic Research Program"],"award-info":[{"award-number":["6.1 Basic Research Program"]}],"id":[{"id":"10.13039\/100009917","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>We discuss results on plasma density profile modifications in the F-region ionosphere that are caused by HF heating with the frequency f0 in the range [(\u2212150 kHz)\u2013(+75 kHz)] around the fourth electron gyroharmonic 4fc. The experiments were conducted at the HAARP facility in June 2014. A multi-frequency Doppler sounder (MDS), which measures the phase and amplitude of reflected sounding radio waves, complemented by the observations of the stimulated electromagnetic emission (SEE) were used for the diagnostics of the plasma perturbations. We detected noticeable plasma expulsion from the reflection region of the pumping wave and from the upper hybrid region, where the expulsion from the latter was strongly suppressed for f0 \u2248 4fc. The plasma expulsion from the upper hybrid region was accompanied by the sounding wave\u2019s anomalous absorption (AA) slower development for f0 \u2248 4fc. Furthermore, slower development and weaker expulsion were detected for the height region between the pump wave reflection and upper hybrid altitudes. The combined MDS and SEE allowed for establishing an interconnection between different manifestations of the HF-induced ionospheric turbulence and determining the altitude of the most effective pump wave energy input to ionospheric plasma by using the dependence on the offset between f0 and 4fc.<\/jats:p>","DOI":"10.3390\/rs13234895","type":"journal-article","created":{"date-parts":[[2021,12,6]],"date-time":"2021-12-06T03:10:38Z","timestamp":1638760238000},"page":"4895","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["HF-Induced Modifications of the Electron Density Profile in the Earth\u2019s Ionosphere Using the Pump Frequencies near the Fourth Electron Gyroharmonic"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1242-5666","authenticated-orcid":false,"given":"Alexey V.","family":"Shindin","sequence":"first","affiliation":[{"name":"Department of Radio Propagation and Radio Astronomy, Radiophysics Faculty, Lobachevsky State University of Nizhni Novgorod, Gagarin Av. 23, 603950 Nizhni Novgorod, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Evgeny N.","family":"Sergeev","sequence":"additional","affiliation":[{"name":"Department of Radio Propagation and Radio Astronomy, Radiophysics Faculty, Lobachevsky State University of Nizhni Novgorod, Gagarin Av. 23, 603950 Nizhni Novgorod, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Savely M.","family":"Grach","sequence":"additional","affiliation":[{"name":"Department of Radio Propagation and Radio Astronomy, Radiophysics Faculty, Lobachevsky State University of Nizhni Novgorod, Gagarin Av. 23, 603950 Nizhni Novgorod, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Gennady M.","family":"Milikh","sequence":"additional","affiliation":[{"name":"Space Plasma Physics Department, University of Maryland, College Park, MD 20742, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Paul","family":"Bernhardt","sequence":"additional","affiliation":[{"name":"Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Carl","family":"Siefring","sequence":"additional","affiliation":[{"name":"Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Michael J.","family":"McCarrick","sequence":"additional","affiliation":[{"name":"Information Technology Division, Naval Research Laboratory, Washington, DC 20375, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yulia K.","family":"Legostaeva","sequence":"additional","affiliation":[{"name":"Department of Radio Propagation and Radio Astronomy, Radiophysics Faculty, Lobachevsky State University of Nizhni Novgorod, Gagarin Av. 23, 603950 Nizhni Novgorod, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,12,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1091","DOI":"10.1070\/PU2007v050n11ABEH006212","article-title":"Nonlinear effects in the ionosphere","volume":"50","author":"Gurevich","year":"2007","journal-title":"Phys.-Uspekhi"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1091","DOI":"10.3367\/UFNe.2016.07.037868","article-title":"Dynamic properties of ionospheric plasma turbulence driven by high-power high-frequency radiowaves","volume":"59","author":"Grach","year":"2016","journal-title":"Phys.-Uspekhi"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"A09211","DOI":"10.1029\/2008JA013199","article-title":"Effects of ionospheric heating on feedback-unstable electromagnetic waves","volume":"113","author":"Streltsov","year":"2008","journal-title":"J. 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