Long-term aspects of nighttime spread F over a low mid-latitude European station

Paul, Ashik; Haralambous, Haris; Oikonomou, Christina

doi:10.1016/j.asr.2019.06.020

Cited by 9 publications

(6 citation statements)

References 53 publications

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“…Experimental evidence over the nighttime midlatitude ionosphere suggests a possible electrodynamical linkage between spread F with the occurrences of sporadic E (Es) layers. That was evident also on studies over Cyprus but also other stations over the European continent [6][7][8] . Mid-latitude backscatter studies over the last few years have shown the existence of enhanced electric fields inside patchy Es or spread Es layers.…”

Section: Introductionmentioning

confidence: 61%

“…On some occasions during geomagnetic storms these conditions at lower latitudes may be associated with GNSS scintillations 14 . The midlatitude spread F is strongly linked to spread Es as one of the major triggering mechanisms for spread F generation is electrodynamic coupling between E and F layer 6 . In the present analysis, a statistical study has been conducted to identify the correlation between spread Es and spread F over Nicosia from 2010 to 2016.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

“…In Figure 3(a-d), a higher occurrence of spread Es was noted during range spreading formation (~95%). This may indicate that zonal polarization fields that are set up inside spread Es map along the magnetic field lines to the F region to cause vertical plasma displacements at the bottom of the ionospheric F layer and thus contribute to the formation of spread F [6][7][8] . The seasonal occurrence rate of spread Es has been studied in Figure 4(a-d) and 90.8% of correlation was found between spread Es occurrence and the spread F formation in the summer solstices of 2010 to 2016 over Nicosia.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

“…In the present study, to investigate the characteristics of nighttime mid-latitude irregularities (MLDs) and their possible displacement mechanisms in terms of TID wavefronts for the formation of spread F, the ROT fluctuation indices map has been analyzed for each spread F case observed over Nicosia from 2010 to 2016. Paul et al (2018) 8 had classified spread F into four categories (i) Frequency spread F (FSF) (ii) Range spread F (RSF) (iii) Mixed spread F (MSF) and (iv) Range spread F converted into Frequency spread F (RSFtoFSF). Suggestions can be made from Figure 2(a) that the signature of ROT indices fluctuations over the ROT indices map may serve the purpose to indicate the presence of TID in the nighttime ionosphere.…”

Section: Rot Indices Fluctuation In Correlation With Spread F Observa...mentioning

confidence: 99%

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Aspects of traveling ionospheric disturbance effects over Cyprus

Paul,

Haralambous

2023

Ninth International Conference on Remote Sensing and Geoinformation of the Environment (RSCy2023)

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To investigate the dynamics of the nighttime ionosphere over the lower mid-latitude European station of Nicosia, Cyprus (35°N, 33°E geographic; magnetic dip. 29.38°N), ionograms recorded by the DPS-4D digisonde during the interval 2010-2016 have been analyzed thoroughly over magnetically quiet conditions to identify and characterize the nighttime spread F signatures. To establish the effect of different driving mechanisms on spread F within the framework of Perkins instability on a statistical basis, the spread F occurrence has been correlated with the presence of Traveling Ionospheric Disturbance (TID) wavefronts in the F region and/or the development of unstable sporadic E layers (spread Es) over the E region of the ionosphere. The presence of TID wavefronts in synchronism with spread F development has been identified by analyzing the GPS Rate of TEC Index (ROTI) fluctuation maps over the eastern Mediterranean nighttime ionosphere. Also, the association between the generation of spread Es layers prior to spread F development has been studied from the Height-time-intensity (HTI) analysis over the Nicosia Digisonde data. The results verify the systematic manifestation and therefore the significance of TID wavefronts and spread Es layers as triggering factors responsible for the seeding of spread F development over the lower European latitudes. A clear seasonal characteristic of spread F occurrence in synchronism with the presence of TID wavefronts and/or spread Es layers over the lower European midlatitudes is also established from 2010 to 2016. .

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Section: Introductionmentioning

confidence: 61%

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Section: Rot Indices Fluctuation In Correlation With Spread F Observa...mentioning

confidence: 99%

See 2 more Smart Citations

Aspects of traveling ionospheric disturbance effects over Cyprus

Paul,

Haralambous

2023

Ninth International Conference on Remote Sensing and Geoinformation of the Environment (RSCy2023)

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“…The seasonal variations in nighttime MSTID could also be understood in terms of the linear growth rate of the Perkins instability (Hamza, 1999; Kelley, 2009). The statistical analysis of SF occurrence presented in Candido et al (2011) and Paul et al (2019) demonstrates that MSTID related to the Perkins instability plays an important role in SF development. Jiang CH et al (2019) reconstructed the ionograms during TID using ray tracing and further verified that ionospheric density wave structure leads to SF.…”

Section: F Region Irregularitymentioning

confidence: 99%

Review of ionospheric irregularities and ionospheric electrodynamic coupling in the middle latitude region

Liu

Zhou

et al. 2021

Earth and Planetary Physics

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This paper briefly reviews ionospheric irregularities that occur in the E and F regions at mid‐latitudes. Sporadic E (ES) is a common ionospheric irregularity phenomenon that is first noticed in the E layer. ES mainly appears during daytime in summer hemispheres, and is formed primarily from neutral wind shear in the mesosphere and lower thermosphere (MLT) region. Field‐aligned irregularity (FAI) in the E region is also observed by Very High Frequency (VHF) radar in mid‐latitude regions. FAI frequently occurs after sunset in summer hemispheres, and spectrum features of E region FAI echoes suggest that type‐2 irregularity is dominant in the nighttime ionosphere. A close relationship between ES and E region FAI implies that ES may be a possible source of E region FAI in the nighttime ionosphere. Strong neutral wind shear, steep ES plasma density gradient, and a polarized electric field are the significant factors affecting the formation of E region FAI. At mid‐latitudes, joint observational experiments including ionosonde, VHF radar, Global Positioning System (GPS) stations, and all‐sky optical images have revealed strong connections across different scales of ionospheric irregularities in the nighttime F region, such as spread F (SF), medium‐scale traveling ionospheric disturbances (MSTID), and F region FAI. Observations suggest that different scales of ionospheric irregularities are generally attributed to the Perkins instability and subsequently excited gradient drift instability. Nighttime MSTID can further evolve into small‐scale structures through a nonlinear cascade process when a steep plasma density gradient exists at the bottom of the F region. In addition, the effect of ionospheric electrodynamic coupling processes, including ionospheric E‐F coupling and inter‐hemispheric coupling on the generation of ionospheric irregularities, becomes more prominent due to the significant dip angle and equipotentiality of magnetic field lines in the mid‐latitude ionosphere. Polarized electric fields can map to different ionospheric regions and excite plasma instabilities which form ionospheric irregularities. Nevertheless, the mapping efficiency of a polarized electric field depends on the ionospheric background and spatial scale of the field.

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