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

Abstract

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