9:00 AM - 9:15 AM
[PEM16-07] Relationship between slow solar wind and plasma-upflow obtained from interplanetary scintillation observation, Hinode/EIS observation and PFSS model
Keywords:solar wind, Interplanetary Scintillation, Extreme Ultraviolet Imaging Spectrometer
Solar wind is a plasma flow that blows from the sun and can be roughly classified into fast solar wind (>500 km/s) and slow solar wind (<500 km/s). The source region of solar wind has been studied for many years. The source region of fast solar wind has been suggested to be related to coronal holes. On the other hand, the source region of slow solar wind has not yet been clarified, and previous studies have suggested various candidates. For example, small-scale coronal holes at low latitudes and boundaries of polar coronal holes have been suggested. It has been suggested that the plasma upflow (hereafter upflow) observed at the edge of active region may also be the source region of slow solar wind.
Institute for Space-Earth Environmental research (Nagoya University) has been conducting Interplanetary Scintillation (IPS) observations using large radio telescopes, and tomographic analysis of the observed data provides the global solar wind structure projected onto the source surface (2.5 solar radii). Upflow region is determined by measuring Doppler shift of the spectra and calculating velocity of plasma relative to the line of sight from spectroscopic data observed by the Extreme Ultraviolet Imaging Spectrometer (EIS) onboard the Hinode satellite. Furthermore, Potential Field Source Surface (PFSS) model can be used to estimate the magnetic field structure from chromosphere to upper source surface. The above data enables us to follow the magnetic field lines extending from upflow region to the source surface, and to analyze the solar wind velocity connected with the upflow.
The purpose of this study is to clarify the relationship between the upflow and slow solar wind and to understand the source region and acceleration mechanism of slow solar wind. In this study, we analyze the solar wind velocity obtained from IPS observations, spectroscopic observation data from EIS, and the magnetic field line structure calculated from the PFSS model to verify whether the upflow region can be a source region of the slow solar wind. Furthermore, relationship between the plasma velocity in the line-of-sight direction at the upflow region (hereafter upflow velocity) and the solar wind velocity was investigated.
We report the results of our analysis of the upflow region observed with Hinode/EIS on 2021/06/18 20:46 UT at the eastern edge of the active region NOAA 12833. We confirmed magnetic field lines extending from the upflow region to the source surface. Then we found the solar wind velocity connected by the magnetic field lines were 200~450 km/s in the region where the upflow velocity derived from FeXIII (202.04 Å) was above 10 km/s. Therefore, it is suggested that slow solar wind was blowing out from the upflow region analyzed in this study. The relationship between upflow and solar wind velocity at each magnetic field line was also investigated, and we found that there was no correlation between the two.
To conclude that upflow is the source region of the slow solar wind, it is necessary to interpret plasma density and abundance ratios in the upflow region obtained from Hinode/EIS spectroscopic observation and compare them with the corresponding in-situ observation data from Solar Orbiter and Parker Solar Probe. To do this, the coalignment error of the EIS data should be less than a few arcseconds. In addition, for understanding acceleration mechanism of the slow solar wind, the non-thermal velocity derived from Hinode/EIS spectroscopic observation and the expansion rate of the coronal magnetic field from PFSS model will be valid.
Institute for Space-Earth Environmental research (Nagoya University) has been conducting Interplanetary Scintillation (IPS) observations using large radio telescopes, and tomographic analysis of the observed data provides the global solar wind structure projected onto the source surface (2.5 solar radii). Upflow region is determined by measuring Doppler shift of the spectra and calculating velocity of plasma relative to the line of sight from spectroscopic data observed by the Extreme Ultraviolet Imaging Spectrometer (EIS) onboard the Hinode satellite. Furthermore, Potential Field Source Surface (PFSS) model can be used to estimate the magnetic field structure from chromosphere to upper source surface. The above data enables us to follow the magnetic field lines extending from upflow region to the source surface, and to analyze the solar wind velocity connected with the upflow.
The purpose of this study is to clarify the relationship between the upflow and slow solar wind and to understand the source region and acceleration mechanism of slow solar wind. In this study, we analyze the solar wind velocity obtained from IPS observations, spectroscopic observation data from EIS, and the magnetic field line structure calculated from the PFSS model to verify whether the upflow region can be a source region of the slow solar wind. Furthermore, relationship between the plasma velocity in the line-of-sight direction at the upflow region (hereafter upflow velocity) and the solar wind velocity was investigated.
We report the results of our analysis of the upflow region observed with Hinode/EIS on 2021/06/18 20:46 UT at the eastern edge of the active region NOAA 12833. We confirmed magnetic field lines extending from the upflow region to the source surface. Then we found the solar wind velocity connected by the magnetic field lines were 200~450 km/s in the region where the upflow velocity derived from FeXIII (202.04 Å) was above 10 km/s. Therefore, it is suggested that slow solar wind was blowing out from the upflow region analyzed in this study. The relationship between upflow and solar wind velocity at each magnetic field line was also investigated, and we found that there was no correlation between the two.
To conclude that upflow is the source region of the slow solar wind, it is necessary to interpret plasma density and abundance ratios in the upflow region obtained from Hinode/EIS spectroscopic observation and compare them with the corresponding in-situ observation data from Solar Orbiter and Parker Solar Probe. To do this, the coalignment error of the EIS data should be less than a few arcseconds. In addition, for understanding acceleration mechanism of the slow solar wind, the non-thermal velocity derived from Hinode/EIS spectroscopic observation and the expansion rate of the coronal magnetic field from PFSS model will be valid.