Detection of a corotating interaction region in solar wind using RPW and SWA instruments of the Solar Orbiter mission.

The study of characteristics, size, and shape variations of corotating interaction region (CIR) with changes in heliocentric distance is of scientific interest. The unique orbit parameters of the Solar Orbiter spacecraft (SOLO) and its set of equipment provide an opportunity to address the posed question. In our study, an attempt has been made to identify CIR regions using only data from the SOLO instruments.

The methodology for identifying CIR is well-developed. It involves in-situ observations of solar wind parameters, such as those proposed in the works of Hajra and Sunny, and verifies the potential presence of high-speed streams (HSS) from coronal holes. Such verification can be performed using SDO/AIA extreme ultraviolet observation data. This methodology can be easily implemented considering the near-Earth satellite constellation. Often, the trajectory of the SOLO passes out of the visibility range of near-Earth solar observation facilities, and there is no opportunity to verify the presence of coronal holes on the solar disk, which could be sources of HSS. In such cases, it is necessary to rely solely on the data from the SOLO instruments.

During the analysis of RPW instrument data, it was observed that sometimes the instrument registers shock events not confirmed by SWA instrument data. However, these events demonstrate an intense increase in solar wind speed and other parameters. The hypothesis has been put forward that multiple activations of the RPW instrument's SBM1 algorithm within a day can be used as a marker for the spacecraft's presence in the CIR zone. To validate this hypothesis, a comparative analysis of RPW data at the time of SBM1 events is conducted, comparing it with data from the SWA-PAS instrument. Based on the examples considered, a conclusion is drawn regarding the ability to track the spacecraft's entry and exit moments from the CIR region and assess the changes in CIR parameters when the spacecraft is within it.

This work is supported by the “Long-term program of support of the Ukrainian research teams at the Polish Academy of Sciences carried out in collaboration with the U.S. National Academy of Sciences with the financial support of external partners”.