Observation and Modeling of Small Spatial Structures of Solar Radio Noise Storms using the uGMRT
arXiv:2507.08093 · doi:10.1007/s11207-025-02519-8
Abstract
One of the most commonly observed solar radio sources in the metric and decametric wavelengths is the solar noise storm. These are generally associated with active regions and are believed to be powered by the plasma emission mechanism. Since plasma emission emits primarily at the fundamental and harmonic of the local plasma frequency, it is significantly affected by density inhomogeneities in the solar corona. The source can become significantly scatter-broadened due to the multi-path propagation caused by refraction from the density inhomogeneities. Past observational and theoretical estimates suggest some minimum observable source size in the solar corona. The details of this limit, however, depends on the modeling approach and details of the coronal turbulence model chosen. Hence pushing the minimum observable source size to smaller values can help constrain the plasma environment of the observed sources. In this work, we for the first time, use data from the upgraded Giant Metrewave Radio Telescope in the 250--500 MHz band, to determine multiple instances of very small-scale structures in the noise storms. We also find that these structures are stable over timescales of 15--30 minutes. By comparing the past observations of Type III radio bursts and noise storms, we hypothesize that the primary reason behind the detection of these small sources in noise storm is due to the local environment of the noise storm. We also build an illustrative model and propose some conditions under which the minimum observable source size predicted by theoretical models, can be lowered significantly.
Accepted for publication in Solar Physics
References in corpus (10)
- Array Programming with NumPy
- The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
- CASA, the Common Astronomy Software Applications for Radio Astronomy
- The structure of solar radio noise storms
- An Anisotropic Density Turbulence Model from the Sun to 1 au Derived From Radio Observations
- Characterising coronal turbulence using snapshot imaging of radio bursts in 80-200 MHz
- Parametric simulation studies on the wave propagation of solar radio emission: the source size, duration, and position
- Real-time RFI Filtering for uGMRT: Overview of the Released System and Relevance to the SKA
- Performance Analysis Techniques for Real-time Broadband RFI Filtering System of uGMRT
- New Insights into Type-I Solar Noise Storms from High Angular Resolution Spectroscopic Imaging with the Upgraded Giant Metrewave Radio Telescope