Equatorial spread F initiation and growth from satellite traces as revealed from conjugate point observations in Brazil

A better understanding of the precursor conditions for the instability growth is very important for identifying the causes of day‐to‐day variability in the equatorial spread F (ESF)/plasma bubble irregularity development. We investigate here the satellite trace (S‐trace) in the ionograms, a precursor to the postsunset ESF occurrence, as observed by Digisondes operated at an equatorial and two magnetic conjugate sites in Brazil during a 66 day observational campaign (Conjugate Point Equatorial Experiment 2002). The satellite traces first occur at the equatorial site, and sequentially, after a variable delay of approximately 20 to 50 min, they are observed nearly simultaneously over the two conjugate sites. The evening prereversal enhancement in the zonal electric field/vertical drift is found to control its development. Using a three‐dimensional simulation code based on collisional interchange instability mechanism, it is shown that the observed S‐trace occurrence sequence is fully consistent with the instability initiation over the equator with the field‐aligned plasma depletion vertical growth marked by latitudinal expansion of its extremities to conjugate locations. The delay in the S‐trace occurrence at the conjugate sites (a measure of the nonlinear growth of the instability for plasma depletion) is controlled also by field line parallel (meridional) neutral wind. The relationship between the S‐trace and the large‐scale wave structure in the F layer, another widely known characterization of the precursor condition for the ESF development, is also clarified.

[1]  S. Vadas,et al.  Large‐scale ionospheric disturbances due to the dissipation of convectively‐generated gravity waves over Brazil , 2012 .

[2]  Weixing Wan,et al.  Precursor signatures and evolution of post‐sunset equatorial spread‐F observed over Sanya , 2012 .

[3]  Masahiro Yamamoto,et al.  On the application of differential phase measurements to study the zonal large scale wave structure (LSWS) in the ionospheric electron content , 2012 .

[4]  M. Yamamoto,et al.  On seeding, large‐scale wave structure, equatorial spread F, and scintillations over Vietnam , 2011 .

[5]  R. Tsunoda.  On equatorial spread F: Establishing a seeding hypothesis , 2010 .

[6]  M. Yamamoto,et al.  First observations of large‐scale wave structure and equatorial spread F using CERTO radio beacon on the C/NOFS satellite , 2009 .

[7]  E. R. de Paula,et al.  Gravity wave initiation of equatorial spread F/plasma bubble irregularities based on observational data from the SpreadFEx campaign , 2009 .

[8]  J. Chau,et al.  Climatology of postsunset equatorial spread F over Jicamarca , 2009 .

[9]  D. Fritts,et al.  The impact of gravity waves rising from convection in the lower atmosphere on the generation and nonlinear evolution of equatorial bubble , 2009 .

[10]  B. Reinisch,et al.  Conjugate Point Equatorial Experiment (COPEX) Campaign in Brazil: Electrodynamics highlights on spread F development conditions and day-to-day variability , 2009 .

[11]  Bodo W. Reinisch,et al.  New Digisonde for research and monitoring applications , 2009 .

[12]  P. Prikryl,et al.  The influence of solar wind on extratropical cyclones – Part 1: Wilcox effect revisited , 2009 .

[13]  F. Kamalabadi,et al.  Gravity wave and tidal influences on equatorial spread F based on observations during the Spread F Experiment (SpreadFEx) , 2008 .

[14]  R. Tsunoda.  Satellite traces: An ionogram signature for large‐scale wave structure and a precursor for equatorial spread F , 2008 .

[15]  B. Reinisch,et al.  Equatorial spread F and sporadic E-layer connections during the Brazilian Conjugate Point Equatorial Experiment (COPEX) , 2008 .

[16]  M. Mascarenhas,et al.  A Three-Dimensional Simulation of Collisional-Interchange-Instability in the Equatorial-Low-Latitude Ionosphere , 2005 .

[17]  Bodo W. Reinisch,et al.  Multistation digisonde observations of equatorial spread F in South America , 2004 .

[18]  J. Eccles.  Assimilation of global‐scale and mesoscale electric fields from low‐latitude satellites , 2004 .

[19]  E. R. Paula,et al.  Effects of the vertical plasma drift velocity on the generation and evolution of equatorial spread F , 1999 .

[20]  F. S. Johnson,et al.  Occurrence of equatorial F region irregularities: Evidence for tropospheric seeding , 1998 .

[21]  T. Maruyama.  A diagnostic model for equatorial spread F, 1, Model description and application to electric field and neutral wind effects , 1988 .

[22]  R. Tsunoda,et al.  On the generation and growth of equatorial backscatter plumes 1. Wave structure in the bottomside F layer , 1981 .

[23]  I. Batista,et al.  Some characteristics of spread F at the magnetic equatorial station Fortaleza , 1980 .

[24]  J. Röttger.  Wave-like structures of large-scale equatorial spread-F irregularities , 1973 .

[25]  A. Lyon,et al.  Equatorial spread-F at Ibadan, Nigeria , 1961 .

[26]  B. Reinisch,et al.  Equatorial F region evening vertical drift, and peak height, during southern winter months: A comparison of observational data with the IRI descriptions , 2006 .

[27]  I. Batista,et al.  Vertical ionization drift velocities and range type spread F in the evening equatorial ionosphere , 1983 .