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Quasi-Periodicity in global solar radio flux at metric wavelengths during Noise Storms  

G. A. Shanmugha Sundaram   Submitted: 2004-11-25 01:14

We present observational results from studying the quasi-periodicities in global solar radio flux during periods of enhanced noise storm activity, over durations of ~4 hrs a day (''intra-day'' variations), observed at 77.5 MHz with the newly commissioned log-periodic array tracking system at the Gauribidanur radio observatory. Positional information on the storm centers were obtained with the radio imaging data from the Nançay (sic.) Radioheliograph (NRH), while their active region (AR) counterparts on the photosphere (and the overlying chromosphere) were located from the Hα images of the Big Bear Solar Observatory (BBSO). The quasi-periodicity in flux was found to be 110 minutes, with the fluctuation in flux being 3(± 1.5) solar flux units (sfu). The results of such pulsations are interpreted qualitatively as evidence for coronal seismology.

Authors: G. A. Shanmugha Sundaram, K. R. Subramanian
Projects: None

Publication Status: Published in 2004, Solar Physics, 222(2), 311
Last Modified: 2004-11-25 01:14
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Spectrum of Solar Type I Continuum Noise Storm in the 50 - 80 MHz band, and Plasma characteristics in the associated source region  

G. A. Shanmugha Sundaram   Submitted: 2004-07-25 20:47

Continuum observations of a solar noise storm in the frequency range of 50 - 80 MHz observed with the Gauribidanur radio spectrograph during 2000 September, 26 & 27, are presented here. The radio spectral index of the noise storm continuum in the band 50 - 80 MHz is found to be ~3.65 during the above period. The Noise Storm continuum radiation is explained as a consequence of the non-thermal, plasma emission mechanism. The beam-density of suprathermal electrons is estimated for the coronal plasma near the source region of storm radiation. Supplementary evidence for the density-estimate is provided by way of analysing the imaging data from the SXT on-board the Yohkoh spacecraft, and the LASCO, MDI, and EIT on board the SoHO spacecraft.

Authors: Sundaram, Shanmugha GA and Subramanian, KR
Projects: Soho-EIT,Soho-MDI,Soho-LASCO,Yohkoh-SXT

Publication Status: Astrophys.J. 605 (2004) 948-959
Last Modified: 2004-07-25 20:47
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Quasi-Periodicity in global solar radio flux at metric wavelengths during Noise Storms
Spectrum of Solar Type I Continuum Noise Storm in the 50 - 80 MHz band, and Plasma characteristics in the associated source region

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