A study on ionospheric scintillation near the EIA crest in relation to equatorial electrodynamics

Chatterjee, Sanjit; Chakraborty, Subhadeep; Veenadhari, B.; Banola, S.

doi:10.1002/2013ja019466

Cited by 6 publications

(5 citation statements)

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“…The H component observed at the station CMRN on these days (not shown here) exhibits an afternoon secondary maximum, which is the precursor of scintillation following Chatterjee et al (2014), and scintillations are observed. Ngwira et al, 2013, studied scintillations in 4 African GPS stations from West to East Africa.…”

Section: Discussionmentioning

confidence: 72%

“…Depending on the scale size irregularities, different observations are made, "the meter scale size irregularities producing plumes in the VHF backscatter radar maps, the decameter sizes that give rise to the spread F echoes in the ionograms, and the hectometer to kilometer sizes produce VHF and UHF radio wave scintillation (Abdu et al, 1983)". Recently, Chatterjee and Chakraborty (2013) and Chatterjee et al (2014) studied the scintillations near the crest of the EIA in India, during quiet magnetic days; in their work, they connected EIA, EEJ and scintillations. They found that a post sunset enhancement of the TEC and afternoon enhancement in EEJ are good precursors for postsunset occurrence of scintillation.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Signatures of solar event at middle and low latitudes in the Europe-African sector, during geomagnetic storms, October 2013

Azzouzi

Migoya-Orué

Mazaudier

et al. 2015

Advances in Space Research

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International audienceThis paper presents the variability of the total electron content, VTEC, the ROTI index (proxy of the scintillation index) and the transient variations of the Earth's magnetic field associated to the impacts of solar events during October 2013. The observations are from middle and low latitudes in European African longitude sector. During October 2013, there are four solar events reaching the Earth. The two first events, on October 2 and October 8 are CME, the third event on October 14, is a jet of fast solar wind flowing from a solar coronal hole, and the last event on October 30 is a slow solar wind with southward excursions of the Bz component of the Interplanetary magnetic field, associated to CME passing near the Earth. For the four events, the variation of VTEC at middle latitudes is the same and presents an increase of VTEC at the time of the impact followed by a decrease of VTEC, lasting one or several days. At low latitudes, no clear common pattern for all the events appears. For the four events the variation of the ROTI index over Africa is different showing the asymmetry between West and East Africa. For the first event, on October 2, the scintillations are not inhibited, for the second and the fourth events on October 8 and 30, the scintillations are inhibited on East Africa and for the third event (high speed solar wind stream), on October 14, the scintillations are inhibited over the whole Africa. The available data allow the full explanation of the observations of October 14, indeed, on this day, there is no post sunset increase of the virtual height h'F2 at Ascension Island. There is no Pre Reversal Enhancement (PRE) of the eastward electric field; it is this electric field which moves up the F layer, the necessary condition for the existence of scintillation. The analysis of the variations of the Earth's magnetic field at low latitudes highlights the presence of the ionospheric disturbance dynamo on October 14, which produces a decrease of the Equatorial Electrojet, several hours after the impact of the high speed solar wind. The disturbance dynamo electric field (DDEF) is westward during the day and till after sunset and turns eastward around 22.30LT. So, on October 14, the westward DDEF inhibits the eastward regular electric field

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Section: Discussionmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Signatures of solar event at middle and low latitudes in the Europe-African sector, during geomagnetic storms, October 2013

Azzouzi

Migoya-Orué

Mazaudier

et al. 2015

Advances in Space Research

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“…The procedure of this combined system is complex to explain for estimating TEC data that is not an issue in this study. A number of relevant studies exist (Edwards, 1989;Lin et al, 2001;Liu et al, 2004;Tsai and Tsai, 2004;Nishihashi et al, 2009;Pulinets and Boyarchuk, 2005;Liu et al, 2006;Klimenko et al, 2012;Lin, 2013;Chuo, 2014, Hayakawa, 2016Chatterjee et al, 2014;Nenovski et al, 2015;Thomas et al, 2017;Wang et al, 2017). TEC maps for three time periods are used in this study.…”

Section: Data Sourcementioning

confidence: 99%

Detecting Total Electron Content Precursors Before Earthquakes by Examining Total Electron Content Images Based on Butterworth Filter in Convolutional Neural Networks

Lin

Chiou

2020

IEEE Access

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Taiwan Standard Time [TST]) as training images (inputs) were used to create two convolutional neural network (CNN) models. However, splitting the TEC maps of the three time periods into daily TEC images caused wedge effects. The wedge effects were reduced using a low-pass filter called the Butterworth filter. This resulted in clearer TEC precursors for earthquakes, facilitating the identification of earthquakes of magnitude M w ≥ 5.0 that exhibited associated TEC precursors during three periods, particularly for the Chi-Chi earthquake of September 21, 1999. The results of this study were compared with those of Lin et al. (2001) and Lin (2010) associated with the Chi-Chi earthquake. Simultaneously, two CNN models that were developed were verified to be rational due to the high accuracy of their predictions. These two models were used to verify each other's accuracies and to demonstrate the reliability of the method in this study. Therefore, statistical analysis was not the aim. The final outputs of the two CNN model were defined as similarities. Similarities, which are larger than 0.5, were defined as TEC precursors of earthquakes. TEC precursors described as temporal TEC multi-precursors (TTMPs) by Zoran et al. (2018) were detectable on the 1st, 3rd, and 4th days (that is, on September 17, 18, and 20, 1999, respectively) prior to the Chi-Chi earthquake of September 21, 1999. These results are consistent with those of Liu et al. (2001) and Lin (2010). A TEC precursor on May 13, 2003, (TST) was detectable 2 days prior to the earthquake on May 15, 2003, (TST) with the magnitude (M w) of 5.52. The low standard deviation (STD) and mean square error (MSE) confirm the reliability of both CNN models. Regarding mechanical principles, the TTMPs related to the Chi-Chi earthquake were caused by an electric field (Liu et al., 2001). The cause of the TEC precursor on May 13, 2003, prior to the earthquake on May 15, 2003, was an argument without any corresponding study for comparison.

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“…This finding is consistent with the diurnal occurrence of scintillation observed in all seasons, which suggests that is associated with the presence of E sb . Furthermore, it is possible that the scintillation events observed in the late afternoon sector could be due to plasma irregularities in the F-region (e.g., Chatterjee et al 2014); however, post sunset F-region scintillations are normally observed after~19:00 LT (Somayajulu et al 1984;Gwal et al 2004;Carter et al 2013;Narayanan et al 2014). Therefore, it is unlikely that the late-afternoon GPS scintillation events analyzed here (~17:00 LT) are due to F-region plasma irregularities.…”

Section: Characteristics Of Daytime Ghz Scintillation In the Vicinitymentioning

confidence: 99%

Daytime gigahertz scintillations near magnetic equator: relationship to blanketing sporadic E and gradient-drift instability

et al. 2015

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Observations made in non-equatorial regions appear to support the hypothesis that the daytime scintillation of radio signals at gigahertz (GHz) frequencies is produced by the gradient-drift instability (GDI) in the presence of a blanketing sporadic E (E sb ) layer. However, the only evidence offered, thus far, to validate this notion, has been some observations of E sb in the vicinity of GHz scintillations. A more comprehensive evaluation requires information about electric field, together with the presence of a steep gradient, which is presumed to be that of E sb . In this regard, the region in the vicinity of the equatorial electrojet (EEJ) appears to be an ideal "laboratory" to conduct such experiments. The dominant driver of electron drift there is the same as that of the EEJ, the vertical polarization electric field, and indications are that the presence of E sb in that vicinity is controlled by a balance in horizontal transport of E sb , between the EEJ electric field and the neutral wind, as described in a model by Tsunoda (On blanketing sporadic E and polarization effects near the equatorial electrojet, 2008). In this paper, we present, for the first time, results from a comprehensive study of daytime GHz scintillations near the magnetic equator. The properties, derived from measurements, are shown, for the first time, to be consistent with a scenario in which E sb presence is dictated by the Tsunoda model, and the plasma-density irregularities responsible for GHz scintillations appear to be produced by the GDI.

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A study on ionospheric scintillation near the EIA crest in relation to equatorial electrodynamics

Cited by 6 publications

References 60 publications

Signatures of solar event at middle and low latitudes in the Europe-African sector, during geomagnetic storms, October 2013

Signatures of solar event at middle and low latitudes in the Europe-African sector, during geomagnetic storms, October 2013

Detecting Total Electron Content Precursors Before Earthquakes by Examining Total Electron Content Images Based on Butterworth Filter in Convolutional Neural Networks

Daytime gigahertz scintillations near magnetic equator: relationship to blanketing sporadic E and gradient-drift instability

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