Browsing by Author "Ananthakrishnan, S."

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    Combining visibilities from the Giant Meterwave Radio Telescop and the Nancay Radio Heliograph : High dynamic range snapshot images of the solar corona at 327 MHz
    (2005-08-01) Mercier, C.; Ananthakrishnan, S.; Subramanian, Prasad
    We report first results from an ongoing program of combining visibilities from the GiantMeterwave Radio Telescope (GMRT) and the Nancay Radio Heliograph (NRH) to produce composite snapshot images of the sun at meter wavelengths. We describe the data processing, including a specific multi-scale CLEAN algorithm. We present results of a) simulations for two models of the sun at 327 MHz, with differing complexity b) observations of a complex noise storm on the sun at 327 MHz on Aug 27 2002. Our results illustrate the capacity of this method to produce high dynamic range snapshot images when the solar corona has structures with scales ranging from the image resolution of 49 ′′ to the size of the whole sun. We find that we cannot obtain reliable snapshot images for complex objects when the visibilities are sparsely sampled.
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    Giant meterwave radio telescope observations of an M2.8 flare: insights into the initiation of a flare-coronal mass ejection event
    (2011-07-05) Subramanian, Prasad; Ananthakrishnan, S.; Janardhan, P.; et al.
    We present the first observations of a solar flare with the GMRT. An M2.8 flare observed at 1060 MHz with the GMRT on Nov 17 2001 was associated with a prominence eruption observed at 17 GHz by the Nobeyama radioheliograph and the initiation of a fast partial halo CME observed with the LASCO C2 corono- graph. Towards the start of the eruption, we find evidence for reconnection above the prominence. Subsequently, we find evidence for rapid growth of a vertical current sheet below the erupting arcade, which is accompanied by the flare and prominence eruption.