3:30 PM - 3:45 PM
[PEM16-01] Evaluation of CME observation performance of next generation solar wind observation system using model simulation
Keywords:coronal mass ejections (CMEs), Interplanetary scintillation (IPS), MHD simulation, radio observation system
Understanding the propagation process of coronal mass ejections (CMEs) in interplanetary space is an important issue in heliospheric science. Predicting the arrival of CMEs on Earth is also important for space weather forecasting. Interplanetary scintillation (IPS) is a radio scattering phenomenon generated by the disturbances in the solar wind. IPS observation has been one of the most important tools for observing CMEs propagating in interplanetary space. Currently, the next-generation solar wind observation system is being developed to improve the IPS observations. This instrument will consist of a flat phased array antenna system at the 327 MHz band, and a digital phased array system. This system enables simultaneous IPS observations in multiple directions. One of the main scientific goals of this project is to understand the propagation process of CMEs in interplanetary space and to predict the arrival of CMEs with high accuracy. The next-generation system has a scalable array system design that will be developed step-by-step. This system design will allow us to achieve partial scientific results during its development phase. The purpose of this study is to clarify the scientific goals that can be achieved step-by-step by the next-generation solar wind observation system. We conducted simulated the CME observations of the next generation system using model simulations.
The model used in this study was SUSANOO-CME, a global magnetohydrodynamic (MHD) simulation of the heliosphere. This simulation can calculate the propagation of a CME that is approximated as a spheromak placed on the inner boundary. The radio scintillation of each radio source was simulated by calculating the scattering of radio wave along the line of sight from the Earth to the radio source using the 3D density distribution of the heliosphere obtained from the MHD simulation results. In this study, we assumed that the radio sources are uniformly distributed over the entire sky, and that each source is observed for 200 seconds, which is approximately the same as the current instruments. Because the next-generation system will be able to observe 4 or 8 directions simultaneously, the simulated IPS data for 4 or 8 directions within the assumed observation field-of-view were calculated.
First, the beam was assumed to scan in the range of +-60 degrees in both the north-south and east-west directions as an ideal condition. We found that this setup allowed us to derive the shape and propagation of the CME, as well as the deformation of the CME during the propagation. However, this setup requires about 16,000 ADCs, which is not realistic to construct. Next, as a realistic setup, we assumed the beam to scan +-60 degrees in the north-south direction and +-5 degrees in the east-west direction, which is the target of the ongoing Phase-I project of the next generation system. We found that the three-dimensional structure of the CME could be sufficiently derived. It was also found that the arrival time of a CME to the Earth could be predicted with an accuracy of about 1 hour by extrapolating the resulting CME to the Earth's position. In addition, it is suggested that the CME tracking performance will be further improved if the beam scan range in the east-west direction is expanded by installing more digital backends in the future. The simulated observation used in this study is expected to be widely applicable to IPS observations by other instruments, and also to scientific studies.
The model used in this study was SUSANOO-CME, a global magnetohydrodynamic (MHD) simulation of the heliosphere. This simulation can calculate the propagation of a CME that is approximated as a spheromak placed on the inner boundary. The radio scintillation of each radio source was simulated by calculating the scattering of radio wave along the line of sight from the Earth to the radio source using the 3D density distribution of the heliosphere obtained from the MHD simulation results. In this study, we assumed that the radio sources are uniformly distributed over the entire sky, and that each source is observed for 200 seconds, which is approximately the same as the current instruments. Because the next-generation system will be able to observe 4 or 8 directions simultaneously, the simulated IPS data for 4 or 8 directions within the assumed observation field-of-view were calculated.
First, the beam was assumed to scan in the range of +-60 degrees in both the north-south and east-west directions as an ideal condition. We found that this setup allowed us to derive the shape and propagation of the CME, as well as the deformation of the CME during the propagation. However, this setup requires about 16,000 ADCs, which is not realistic to construct. Next, as a realistic setup, we assumed the beam to scan +-60 degrees in the north-south direction and +-5 degrees in the east-west direction, which is the target of the ongoing Phase-I project of the next generation system. We found that the three-dimensional structure of the CME could be sufficiently derived. It was also found that the arrival time of a CME to the Earth could be predicted with an accuracy of about 1 hour by extrapolating the resulting CME to the Earth's position. In addition, it is suggested that the CME tracking performance will be further improved if the beam scan range in the east-west direction is expanded by installing more digital backends in the future. The simulated observation used in this study is expected to be widely applicable to IPS observations by other instruments, and also to scientific studies.