Parker Solar Probe detects solar radio bursts related with a behind-the-limb active region

TL;DR

This study combines ground-based and spacecraft observations to detect and analyze solar radio bursts from an active region behind the solar limb, refining coronal density models and understanding wave propagation.

Contribution

It presents simultaneous observations from PSP and ground-based telescopes to detect behind-the-limb solar radio bursts and refines the solar corona density model based on these data.

Findings

Detected radio bursts from behind-the-limb active region using PSP and ground observations.

Refined the solar corona density model based on radio wave delays.

Demonstrated propagation of radio waves through low-density regions enabling detection by PSP.

Abstract

The interpretation of solar radio bursts observed by Parker Solar Probe (PSP) in the encounter phase plays a key role in understanding intrinsic properties of the emission mechanism in the solar corona. Lower time-frequency resolution of the PSP receiver can be overcome by simultaneous ground-based observations using more advanced antennas and receivers. In this paper we present such observations for which the active active region 12765, begetter of type III, J, and U solar bursts, was within sight of ground-based instruments and behind the solar limb of the PSP spacecraft. We used a subarray of the Giant Ukrainian Radio Telescope (GURT) to get the spectral properties of radio bursts at the frequency range of 8-80 MHz, as well as the PSP radio instruments with a bandwidth of 10.5 kHz - 19.2 MHz, during solar observations on June 5, 2020. We directly detected the radio events initiated by the active region behind the solar limb of the PSP spacecraft, using special conditions in the solar corona, due to the absence of active regions from the PSP side. Following the generation mechanism of solar radio emission, we refined the density model for the solar corona above the active region 12765 responsible for the radio bursts. Based on the PSP spacecraft position near the Sun and delays of radio waves between space- and ground-based records, we found the corresponding radio responses on the PSP spectrogram. The absence of sunspots from the PSP side contributes to the propagation of radio waves from a dense loop of the Sun to quiet regions with low densities, through which PSP instruments can detect the radiation.