Research Article

Prompt identification of solar wind stream interaction regions from Survey Burst Mode observations of the Radio and Plasma Wave experiment on Solar Orbiter

¹ Institute of Radio Astronomy of the National Academy of Sciences of Ukraine, Mystetstv Street, 4, Kharkiv 61002, Ukraine
² Space Research Centre of the Polish Academy of Sciences, Bartycka Street, 18A, Warsaw, 00-716, Poland

^* Corresponding author: chechotkin@rian.kharkov.ua

Received: 9 August 2024
Accepted: 19 July 2025

Abstract

Studying stream interaction regions (SIRs), from their inception and the dynamics of their development, can provide insights into solar-terrestrial connections. Some in-situ instruments on the Solar Orbiter (SolO) space mission are designed to measure solar wind (SW) and interplanetary magnetic field parameters along the flight path. These instruments are ideal for studying the dynamics of SIR evolution at heliocentric distances ranging from 0.28 to 1.0 AU and with changes in heliolatitude of 0° to 33°. To address the challenges of promptly identifying SIRs and predicting their arrival time on Earth, we consider using trigger events from the Radio and Plasma Wave (RPW)/SolO instrument, which are transmitted in telemetry data packages. We suggest that multiple activations of the trigger mode (SBM1 mode) in the RPW instrument over an interval of up to 4 h may reflect the fine structure of large-scale events in SW. Such events can serve as markers for the spacecraft’s location within the SIR. In this regard, the 2023 analysis revealed that multiple activations of the SBM1 trigger mode throughout the day accounted for more than 50% of the total number of days for which such events were recorded. Of this number, 63% were events when the trigger algorithm was prompted repeatedly within a time interval of up to 4 h. A comparison of the registration times of SBM1 trigger events with the SW parameters obtained from the SWA-PAS and MAG instruments showed that repeated activations of the trigger algorithm occurred at the stream interface surface when a high-speed SW stream and a formed compression region were present. We believe that high gradients of changes in SW parameters in this SIR region lead to intense fluctuations in proton density and magnetic field in SW, which sets the trigger mode. To identify coronal holes that are a potential source for the observed solar wind structure, we propose a set of analytical expressions that enable estimating the position of coronal holes on the solar disk relative to the moment of SIR registration by SolO instruments.