5:15 PM - 6:45 PM
[PEM16-P07] Interplanetary Scintillation Observations of Solar Wind During Solar Cycles 24 and 25: Challenges for Enhanced Reconstruction
Keywords:solar wind, interplanetary scintillation
Radio waves originating from distant radio source are scattered by solar wind plasma, causing fluctuations in their intensity on the ground. This phenomenon, known as interplanetary scintillation (IPS), enables remote measurements of solar wind. Since the early-1980s, we started IPS observations at a frequency of 327MHz at the Institute for Space-Earth Environmental Research (ISEE), Nagoya University. Initially, we conducted at three domestic facilities at Toyokawa, Fuji, and Sugadaira, then expanded in 1993 with the installation of an antenna in Kiso, leading to observations at four sites. Subsequently, successful reconstruction of global solar wind structures as a two-dimensional map in each Carrington rotation with good special coverage was achieved. Unfortunately, the Sugadaira antenna was destroyed by heavy snowfall in 2012, resulting in the closure of the observatory, so the IPS observations have continued at three sites since then.
To derive the solar wind speed vector, a single radio source must be observed simultaneously at least three locations. Through a cross-correlation analysis of the scintillation data obtained at those sites, we obtain the solar wind speed across the Line-of-Sight (LOS) from the antenna to the radio source. However, the recent increase of radio interferences, the success rate of simultaneous observations at three locations is declining. This has led to significant implications for the reconstruction of solar wind structures, particularly evident in the form of data gaps affecting the reconstructed solar wind maps especially during solar cycles 24-25 after the closure of Sugadaira observatory.
In this study, we attempted to achieve a better reconstruction of solar wind structures in Solar Cycles (SC) 24 and 25 by revisiting data processing and developing techniques to compensate for the reduced number of observations. We will present a various trial of our study, and their validations by comparing the reconstructed solar wind structure with spacecraft observations. Then we will also discuss the characteristics of the newly obtained solar wind structure during SC 24 and SC 25 in this study.
To derive the solar wind speed vector, a single radio source must be observed simultaneously at least three locations. Through a cross-correlation analysis of the scintillation data obtained at those sites, we obtain the solar wind speed across the Line-of-Sight (LOS) from the antenna to the radio source. However, the recent increase of radio interferences, the success rate of simultaneous observations at three locations is declining. This has led to significant implications for the reconstruction of solar wind structures, particularly evident in the form of data gaps affecting the reconstructed solar wind maps especially during solar cycles 24-25 after the closure of Sugadaira observatory.
In this study, we attempted to achieve a better reconstruction of solar wind structures in Solar Cycles (SC) 24 and 25 by revisiting data processing and developing techniques to compensate for the reduced number of observations. We will present a various trial of our study, and their validations by comparing the reconstructed solar wind structure with spacecraft observations. Then we will also discuss the characteristics of the newly obtained solar wind structure during SC 24 and SC 25 in this study.