ISWI Newsletter - Vol.2 No.51
28 June 2010

Dr Jean-Pierre Raulin has asked me to circulate the following text (in blue) and the attached pdf.

In his words: "It is an update of scientific activities performed using the South America VLF Network (SAVNET). I also attach a recently accepted (JGR) paper related to the [following] text." ***********************************************************************

The SAVNET instrumental facility has shown its ability to perform research on the monitoring of transient solar activity. For the period of 2007 - 2010 of low solar activity, about 500 hundred solar X-ray flares were detected by the SAVNET as phase changes of waves propagating on log distances.

This traduces perturbations of the electrical conductivity below the quiescent D region of the ionosphere, when ionization excesses appear due to the incoming solar photons. In this study, SAVNET has shown that the low ionospheric plasma is a very sensitive sensor of such events since 100% of B4 (GOES) class events are detected. Similarly, the lowest event detected so far corresponds to a small B2.7 (GOES) class X-ray event, that is a peak X-ray power of 2.7 10^-7W/m².

These results also directly confirm that the solar Lyman-alpha radiation is the main responsible for the formation of the quiescent daytime ionospheric D-region. Therefore, the VLF technique, is a very promising mean of monitoring the solar Lyman-alpha emission, which cannot be directly observed on ground.

Very impressive, Dr Raulin !

(1) Jean-Pierre Raulin, Fernando C. P. Bertoni, Hernan R. Gavilán, Walter Guevara-Day, Rodolfo Rodriguez, Germán Fernandez, Emilia Correia, Pierre Kaufmann, Alessandra Pacini, Tardelli R. C. Stekel, Washington L. C. Lima, Nelson J. Schuch, Paulo R. Fagundes, Rubens Hadano Solar flare detection sensitivity using the South America VLF Network (SAVNET), JGR in print 284 KB pdf, 19 pages, (click )

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