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Abstract Measuring plasma parameters in the upper solar corona and inner heliosphere is challenging because of the region’s weakly emissive nature and inaccessibility for most in situ observations. Radio imaging of broadened and distorted background astronomical radio sources during solar conjunction can provide unique constraints for the coronal material along the line of sight. In this study, we present radio spectral imaging observations of the Crab Nebula (Tau A) from 2024 June 9 to June 22 when it was near the Sun with a projected heliocentric distance of 5–27 solar radii, using the Owens Valley Radio Observatory’s Long Wavelength Array at multiple frequencies in the 30–80 MHz range. The imaging data reveal frequency-dependent broadening and distortion effects caused by anisotropic wave propagation through the turbulent solar corona at different distances. We analyze the brightness, size, and anisotropy of the broadened images. Our results provide detailed observations showing that the eccentricity of the unresolved source increases as the line of sight approaches the Sun, suggesting a higher anisotropic ratio of the plasma turbulence closer to the Sun. In addition, the major axis of the elongated source is consistently oriented in the direction perpendicular to the radial direction, suggesting that the turbulence-induced scattering effect is more pronounced in the direction transverse to the coronal magnetic field. Lastly, when the source undergoes large-scale refraction as the line of sight passes through a streamer, the apparent source exhibits substructures at lower frequencies. This study demonstrates that observations of celestial radio sources with lines of sight near the Sun provide a promising method for measuring turbulence parameters in the inner heliosphere. 

Abstract Routine measurements of the magnetic field of coronal mass ejections (CMEs) have been a key challenge in solar physics. Making such measurements is important both from a space weather perspective and for understanding the detailed evolution of the CME. In spite of significant efforts and multiple proposed methods, achieving this goal has not been possible to date. Here we report the first possible detection of gyroresonance emission from a CME. Assuming that the emission is happening at the third harmonic, we estimate that the magnetic field strength ranges from 7.9 to 5.6 G between 4.9 and 7.5R_⊙. We also demonstrate that this high magnetic field is not the average magnetic field inside the CME, but most probably is related to small magnetic islands, which are also being observed more frequently with the availability of high-resolution and high-quality white-light images. 

Abstract A number of theoretical studies have proposed a prompt or precursor low-frequency radio counterpart to gravitational wave events detected by LIGO and Virgo. Detection of such events would offer a new window on the immediate environment of the merger and provide an avenue to rapid localization. However, identifying fast transients in real-time in localization regions spanning hundreds to thousands of square degrees presents severe technical challenges. To address these challenges, we present a novel technique embodied in the Time Machine, a system featuring a two-stage voltage buffer and subsequent processing pipeline designed for the Long Wavelength Array at the Owens Valley Radio Observatory. This array is developed to instantaneously image the entire viewable sky. We detail the system’s buffer structure that allows data collection from several minutes before a trigger event, up to 30 minutes after an event. The processing of this voltage data involves beamforming and searching the full 90th-percentile localization region above the horizon with ms-time resolution and the ability to detect events with ∼100 Jy ms (7σ) fluence within the 55–85 MHz band. Furthermore, we incorporate an offline cross-correlation pipeline to improve positional accuracy of identified transients to within subarcminute levels. We present a full overview of the system design and initial testing results.