Quasi-stationary substructure within a sporadic E layer observed by the Low-Frequency Array (LOFAR)
Observations made with the Low-Frequency Array (LOFAR) have been used to infer the presence of variations in a sporadic E layer on a spatial scale of several kilometres and a temporal scale of ~10 min. LOFAR stations across the Netherlands observed Cygnus A between 17 UT and 18 UT on 14th July 2018...
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EDP Sciences
2024-01-01
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| Series: | Journal of Space Weather and Space Climate |
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| Online Access: | https://www.swsc-journal.org/articles/swsc/full_html/2024/01/swsc230077/swsc230077.html |
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| author | Wood Alan G. Dorrian Gareth D. Boyde Ben Fallows Richard A. Themens David R. Mevius Maaijke Sprenger Tim Main Robert Pryse S. Eleri Elvidge Sean |
| author_facet | Wood Alan G. Dorrian Gareth D. Boyde Ben Fallows Richard A. Themens David R. Mevius Maaijke Sprenger Tim Main Robert Pryse S. Eleri Elvidge Sean |
| author_sort | Wood Alan G. |
| collection | DOAJ |
| description | Observations made with the Low-Frequency Array (LOFAR) have been used to infer the presence of variations in a sporadic E layer on a spatial scale of several kilometres and a temporal scale of ~10 min. LOFAR stations across the Netherlands observed Cygnus A between 17 UT and 18 UT on 14th July 2018 at frequencies between 24.9 MHz and 64.0 MHz. Variations in the relative signal intensity, together with the consideration of geometric optics, were used to infer the presence of a plasma structure. Spatial variations between the stations and the dispersive nature of the observations suggested that this plasma structure was located within the ionosphere. Independent confirmation of the presence of a sporadic E layer, and variation within it, was obtained from observations made by the Juliusruh ionosonde (54.6°N, 13.4°E), which observed reflection of radio waves at an altitude of ~120 km and from frequencies of up to ~6 MHz. The large number (38) of LOFAR stations across the Netherlands, together with the sub-second temporal resolution and broadband frequency coverage of the observations, enabled the fine details of the spatial variation and the evolution of the structure to be determined. The structure was quasi-stationary, moving at ~12 m s−1, and it exhibited significant variation on spatial scales of a few kilometres. The observations were consistent with the steepening of a plasma density gradient at the edge of the feature over time due to an instability process. A 1-D numerical model showed that the observations were consistent with an electron density enhancement in the sporadic E layer with a density change of 2 × 1011 m−3 and a spatial scale of several kilometres. Collectively, these results show the ability of LOFAR to observe substructure within sporadic E layers and how this substructure varies with time. They also show the potential value of such datasets to constrain models of instability processes, or to discriminate between competing models. |
| format | Article |
| id | doaj-art-a5b5fc6d5d6d4b4a8097fdfb53fd0bc3 |
| institution | Kabale University |
| issn | 2115-7251 |
| language | English |
| publishDate | 2024-01-01 |
| publisher | EDP Sciences |
| record_format | Article |
| series | Journal of Space Weather and Space Climate |
| spelling | doaj-art-a5b5fc6d5d6d4b4a8097fdfb53fd0bc32024-11-08T09:36:38ZengEDP SciencesJournal of Space Weather and Space Climate2115-72512024-01-01142710.1051/swsc/2024024swsc230077Quasi-stationary substructure within a sporadic E layer observed by the Low-Frequency Array (LOFAR)Wood Alan G.0https://orcid.org/0000-0002-7527-4757Dorrian Gareth D.1https://orcid.org/0000-0002-5308-6894Boyde Ben2https://orcid.org/0000-0002-2953-9734Fallows Richard A.3Themens David R.4https://orcid.org/0000-0003-2567-8187Mevius Maaijke5https://orcid.org/0000-0002-3086-8455Sprenger Tim6https://orcid.org/0000-0002-1160-7276Main Robert7Pryse S. Eleri8Elvidge Sean9https://orcid.org/0000-0003-2846-0730Space Environment and Radio Engineering (SERENE) Group, University of BirminghamSpace Environment and Radio Engineering (SERENE) Group, University of BirminghamSpace Environment and Radio Engineering (SERENE) Group, University of BirminghamScience and Technology Facilities Council (STFC) Rutherford Appleton LaboratorySpace Environment and Radio Engineering (SERENE) Group, University of BirminghamASTRON – The Netherlands Institute for Radio AstronomyMax-Planck-Institut für RadioastronomieMax-Planck-Institut für RadioastronomieDepartment of Physics, Aberystwyth UniversitySpace Environment and Radio Engineering (SERENE) Group, University of BirminghamObservations made with the Low-Frequency Array (LOFAR) have been used to infer the presence of variations in a sporadic E layer on a spatial scale of several kilometres and a temporal scale of ~10 min. LOFAR stations across the Netherlands observed Cygnus A between 17 UT and 18 UT on 14th July 2018 at frequencies between 24.9 MHz and 64.0 MHz. Variations in the relative signal intensity, together with the consideration of geometric optics, were used to infer the presence of a plasma structure. Spatial variations between the stations and the dispersive nature of the observations suggested that this plasma structure was located within the ionosphere. Independent confirmation of the presence of a sporadic E layer, and variation within it, was obtained from observations made by the Juliusruh ionosonde (54.6°N, 13.4°E), which observed reflection of radio waves at an altitude of ~120 km and from frequencies of up to ~6 MHz. The large number (38) of LOFAR stations across the Netherlands, together with the sub-second temporal resolution and broadband frequency coverage of the observations, enabled the fine details of the spatial variation and the evolution of the structure to be determined. The structure was quasi-stationary, moving at ~12 m s−1, and it exhibited significant variation on spatial scales of a few kilometres. The observations were consistent with the steepening of a plasma density gradient at the edge of the feature over time due to an instability process. A 1-D numerical model showed that the observations were consistent with an electron density enhancement in the sporadic E layer with a density change of 2 × 1011 m−3 and a spatial scale of several kilometres. Collectively, these results show the ability of LOFAR to observe substructure within sporadic E layers and how this substructure varies with time. They also show the potential value of such datasets to constrain models of instability processes, or to discriminate between competing models.https://www.swsc-journal.org/articles/swsc/full_html/2024/01/swsc230077/swsc230077.htmlsporadic esmall scale variationsradio wave propagationmid latitude ionosphereobservations |
| spellingShingle | Wood Alan G. Dorrian Gareth D. Boyde Ben Fallows Richard A. Themens David R. Mevius Maaijke Sprenger Tim Main Robert Pryse S. Eleri Elvidge Sean Quasi-stationary substructure within a sporadic E layer observed by the Low-Frequency Array (LOFAR) Journal of Space Weather and Space Climate sporadic e small scale variations radio wave propagation mid latitude ionosphere observations |
| title | Quasi-stationary substructure within a sporadic E layer observed by the Low-Frequency Array (LOFAR) |
| title_full | Quasi-stationary substructure within a sporadic E layer observed by the Low-Frequency Array (LOFAR) |
| title_fullStr | Quasi-stationary substructure within a sporadic E layer observed by the Low-Frequency Array (LOFAR) |
| title_full_unstemmed | Quasi-stationary substructure within a sporadic E layer observed by the Low-Frequency Array (LOFAR) |
| title_short | Quasi-stationary substructure within a sporadic E layer observed by the Low-Frequency Array (LOFAR) |
| title_sort | quasi stationary substructure within a sporadic e layer observed by the low frequency array lofar |
| topic | sporadic e small scale variations radio wave propagation mid latitude ionosphere observations |
| url | https://www.swsc-journal.org/articles/swsc/full_html/2024/01/swsc230077/swsc230077.html |
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