Speaker
Description
Solar radio emissions originate from a wide range of phenomena — from faint gyrosynchrotron emission associated with CMEs, to thermal emission from the quiet Sun, to intense coherent emissions from solar radio bursts. These emissions can span up to nine orders of magnitude over small spans in time and frequency, requiring spectroscopic snapshot imaging to capture their full complexity. However, calibrating solar radio data, particularly from aperture arrays with large fields of view like LOFAR, remains a major challenge. Standard calibrator sources are often dominated and are not visible in the presence of the Sun, and even stronger sources, A-team sources, are frequently contaminated by solar flux, especially during solar radio bursts.
To address these challenges, we have developed a robust, fully unsupervised solar calibration and imaging pipeline — the Solar Imaging Pipeline for LOFAR (SIMPL). This pipeline, tuned for both LBA and HBA, significantly enhances image fidelity and dynamic range (by 1–2 orders of magnitude) through several calibration and flagging strategies tailored for solar data. These include: careful selection of data to be used for calibration, a custom RFI flagger optimized for solar data, and a self-calibration scheme tuned specifically for the solar case.
We are also actively developing full-Stokes polarization calibration and imaging capabilities. This approach leverages the unpolarized sky at these low radio frequencies, which appears polarized only due to the instrumental beam effects. Although still in early stages, our preliminary results are promising, demonstrating polarization leakage levels below 0.5%.
In this presentation, I will describe how we addressed the specific challenges of solar imaging with LOFAR, the strategies implemented in SIMPL, and highlight some key science results obtained by using this pipeline.
