An automated, self-calibration based pipeline for high-fidelity solar imaging with LOFAR: SIMPL

TL;DR

This paper introduces SIMPL, an automated pipeline for high-fidelity solar imaging with LOFAR, effectively handling solar variability and ionospheric distortions to produce science-ready images for extensive solar studies.

Contribution

The paper presents a novel automated imaging pipeline, SIMPL, that significantly improves calibration, imaging quality, and automation for LOFAR solar observations compared to previous methods.

Findings

Achieves over tenfold improvement in imaging dynamic range.

Reliably produces high-quality spectroscopic snapshot images.

Successfully processes a decade of LOFAR solar data.

Abstract

The LOw Frequency ARray (LOFAR) is capable of imaging spectroscopy of the Sun in the 10-240 MHz frequency range, with high spectral, temporal, and spatial resolution. However, the complex and rapidly varying nature of solar radio emission - spanning several orders of magnitude in brightness further exacerbated by the strong ionospheric phase distortions during daytime observations, poses major challenges for calibration, imaging, and automation. We aim to develop a fully automated, high-fidelity imaging pipeline optimized for LOFAR solar observations, capable of handling the intrinsic variability of solar emission and producing science-ready images with minimal human intervention. We have built the Solar Imaging Pipeline for LOFAR (SIMPL), which integrates excision of radio-frequency interference (RFI) for the solar-specific scenarios, calibration strategies, and self-calibration. The pipeline is designed to enable scalable and uniform processing of large archival datasets. SIMPL achieves more than an order-of-magnitude improvement in imaging dynamic range compared to previous efforts and reliably produces high-quality spectroscopic snapshot images. It has been tested across a wide range of solar conditions. It is currently being employed to process a decade of LOFAR solar observations, providing science-ready FITS images for the community and enabling both comprehensive and novel studies of solar radio phenomena -- ranging from quiet Sun emission and faint non-thermal features to active regions and their associated dynamic events, such as transient bursts.