|Abstract : || |
The Sun is a plasma laboratory capturing a variety of plasma parameters. The plasma resides in the meanders of the magnetic fields in the outmost layer, the solar corona, which is rooted in the photosphere, the visible solar surface. The dynamic processes at the solar
surface naturally influences the coronal magnetic fields. Thus produced solar activity, including eruptions like flares and coronal mass ejection, is crucial for space weather and presents a potential hazard for human space activity.
In X-rays and extreme-UV bands, this manifests itself in a broad range of phenomena ranging from the most energetic flares to those at the detection threshold of even the most capable instrumentation. The radio wavelengths catch unique plasma processes from the solar surface to the corona via emission mechanisms like gyrosynchrotron, plasma emission etc... These radio emissions are complex, dynamic and variable in frequency and time, even during periods of low solar activity. The propagation effects of the radio waves through the inhomogeneous turbulent coronal plasma further complicate the scenario. As coherent emission is involved, even the weaker solar flares can produce disproportionately strong signatures at radio metre waves. Constant fluctuations of energetically weak flares permeate even the quiet corona, often called "nanoflares". The observed variabilities are due to weak energetic events, which are requisite for nanoflare-based coronal and chromospheric heating theories.
The new-generation solar radio data like the Murchison Widefield Array, a precursor of the Square Kilometre Array (SKA) and Jansky Very Large Array, supply high-sensitivity solar data. It provides an opportunity to probe plasma diagnostics from the solar corona and eruptive phenomena like solar flares and coronal mass ejections. In this talk, I will summarise the new analysis techniques, the latest coronal diagnostics results during solar flares, radio wave propagation in corona, their relevance for space weather and challenges with future radio telescopes like SKA.