On the spatial relationship of 1-meter equatorial spread-F irregularities and depletions in total electron content

1979 ◽  
Vol 6 (11) ◽  
pp. 873-876 ◽  
Author(s):  
Roland T. Tsunoda ◽  
David M. Towle
Keyword(s):  
Total Electron Content ◽  
Spatial Relationship ◽  
Electron Content ◽  
Total Electron ◽  
Equatorial Spread F ◽  
Spread F ◽  
Relationship Of

scholarly journals Seasonal dependence of the "forecast parameter" based on the EIA characteristics for the prediction of Equatorial Spread F (ESF)

2008 ◽  
Vol 26 (7) ◽  
pp. 1751-1757 ◽  
Author(s):  
S. V. Thampi ◽  
S. Ravindran ◽  
T. K. Pant ◽  
C. V. Devasia ◽  
R. Sridharan
Keyword(s):  
Seasonal Variability ◽  
Seasonal Pattern ◽  
Onset Time ◽  
Critical Value ◽  
Latitudinal Gradients ◽  
Electron Content ◽  
Total Electron ◽  
Equatorial Spread F ◽  
Spread F ◽  
Definite Role

Abstract. In an earlier study, Thampi et al. (2006) have shown that the strength and asymmetry of Equatorial Ionization Anomaly (EIA), obtained well ahead of the onset time of Equatorial Spread F (ESF) have a definite role on the subsequent ESF activity, and a new "forecast parameter" has been identified for the prediction of ESF. This paper presents the observations of EIA strength and asymmetry from the Indian longitudes during the period from August 2005–March 2007. These observations are made using the line of sight Total Electron Content (TEC) measured by a ground-based beacon receiver located at Trivandrum (8.5° N, 77° E, 0.5° N dip lat) in India. It is seen that the seasonal variability of EIA strength and asymmetry are manifested in the latitudinal gradients obtained using the relative TEC measurements. As a consequence, the "forecast parameter" also displays a definite seasonal pattern. The seasonal variability of the EIA strength and asymmetry, and the "forecast parameter" are discussed in the present paper and a critical value for has been identified for each month/season. The likely "skill factor" of the new parameter is assessed using the data for a total of 122 days, and it is seen that when the estimated value of the "forecast parameter" exceeds the critical value, the ESF is seen to occur on more than 95% of cases.

scholarly journals LONGITUDINAL AND DAY-TO-DAY VARIATIONS OF EQUATORIAL SPREAD F OCCURRENCE FROM OBSERVATIONS OVER SOUTH AMERICA

2017 ◽  
Vol 35 (1) ◽  
Author(s):  
Ricardo Yvan de La Cruz Cueva ◽  
Cesar E. Valladares ◽  
Eurico Rodrigues de Paula ◽  
Mangalathayil Ali Abdu ◽  
Igo Paulino ◽  
...  
Keyword(s):  
South America ◽  
Periodic Structures ◽  
Detection Algorithm ◽  
Electron Content ◽  
Total Electron ◽  
Equatorial Spread F ◽  
Bubble Detection ◽  
December Solstice ◽  
Spread F ◽  
Occurrence Pattern

ABSTRACT. In this work we studied the longitudinal and day-to-day variability of equatorial spread F occurrence over South America. Digisonde from the equatorial stations of São Luís and Jicamarca, and Total Electron Content (TEC) data from several GPS receivers were used to analyse the ionospheric conditions conductive to ionospheric plasma irregularity generation during the solar minimum months of September 2009 to January 2010. To support this analysis an Automatic-Bubble- Detection-Algorithm was used to detect abrupt decreases that plasma bubbles introduce in the TEC values. The bubble occurrence pattern over SA observed in this work maximizes on September-October (equinox) in the west and November-January (December solstice) in the east-longitudes. However, on a day-to-day basis bubble signatures are also detected all over SA during this period. Besides being observed during days with pronounced prereversal enhancement (PRE), as expected, the TEC depletions were also observed during days without PRE, during equinox at Jicamarca and December solstice at São Luís. This unexpected occurrence of TEC depletions (TECds) suggests that seeding mechanisms, like periodic structures are present and modify the onset conditions of bubble-events. In this report are shown evidences of wave-like structures previous to bubble development. Keywords: day-to-day variation, equatorial spread F, aeronomy. RESUMO. Neste trabalho estuda-se a variabilidade longitudinal e dia-a-dia da ocorrência do spread F equatorial sobre América do Sul. Digissondas das estações equatoriais de São Luís e Jicamarca, e dados de Conteúdo Eletrônico Total (TEC) de vários receptores GPS foram usados para analisar as condições ionosféricas para a geração de irregularidades de plasma ionosférico durante os meses de mínimo solar de Setembro 2009 a Janeiro 2010. Para dar suporte a esta análise um Algoritmo de Detecção Automática de Bolhas foi usado para detectar decréscimos abruptos nos valores de TEC. O padrão de ocorrência de bolhas sobre SA observado neste trabalho são Setembro-Outubro (equinócio) no leste e Novembro-Janeiro (solstício de Dezembro) nas longitudes leste. Entretanto, na observação dia-a-dia as assinaturas de bolhas são também detectadas sobre toda SA neste período. Além de ter sido observado durante dias com pronunciado pré-reversal enhancement (PRE), como esperado, as depleções TEC foram também observadas durante dias sem PRE, durante equinócio em Jicamarca e solstício de Dezembro em São Luís. Esta ocorrência inesperada de depleções TEC (TECds) sugere que mecanismos geradores, como estruturas períodicas estão presentes e modificam as condições de início de eventos-bolhas. Neste trabalho são apresentados resultados mostrando evidências de estruturas tipo onda prévio ao desenvolvimento de uma bolha. Palavras-chave: variabilidade dia a dia, spread F equatorial, aeronomia.

scholarly journals Observations in equatorial anomaly region of total electron content enhancements and depletions

2005 ◽  
Vol 23 (7) ◽  
pp. 2449-2456 ◽  
Author(s):  
N. Dashora ◽  
R. Pandey
Keyword(s):  
Total Electron Content ◽  
Scintillation Index ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Low Latitude ◽  
Total Electron ◽  
First Results ◽  
Spread F ◽  
New Feature ◽  
Low Latitude Ionosphere

Abstract. A GSV 4004A GPS receiver has been operational near the crest of the equatorial anomaly at Udaipur, India for some time now. The receiver provides the line-of-sight total electron content (TEC), the phase and amplitude scintillation index, σφ and S4, respectively. This paper presents the first results on the nighttime TEC depletions associated with the equatorial spread F in the Indian zone. The TEC depletions are found to be very well correlated with the increased S4 index. A new feature of low-latitude TEC is also reported, concerning the observation of isolated and localized TEC enhancements in the nighttime low-latitude ionosphere. The TEC enhancements are not correlated with the S4 index. The TEC enhancements have also been observed along with the TEC depletions. The TEC enhancements have been interpreted as the manifestation of the plasma density enhancements reported by Le et al. (2003). Keywords. Ionosphere (Equatorial ionosphere; Ionospheric irregularities)

scholarly journals Short-term relationship of total electron content with geomagnetic activity in equatorial regions

2008 ◽  
Vol 113 (A11) ◽  
pp. n/a-n/a ◽  
Author(s):  
X. Wang ◽  
Q. Sun ◽  
R. Eastes ◽  
B. Reinisch ◽  
C. E. Valladares
Keyword(s):  
Total Electron Content ◽  
Geomagnetic Activity ◽  
Electron Content ◽  
Short Term ◽  
Total Electron ◽  
Relationship Of
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