A Comparison of the Active Region Upflow and Core Morphologies Using Simultaneous Spectroscopic Observations from IRIS and Hinode.

Abstract:

The origin of the slow solar wind is still an open issue. It has been suggested that upflows at the edge of the active region are the source of the plasma outflow, and therefore contribute to the slow solar wind. However, the origin and morphology of the upflow region remain open questions. We investigated how the plasma properties (flux, Doppler velocity, and non-thermal velocity) change throughout the solar atmosphere, from the chromosphere via the transition region to the corona. We compared the upflow region and the core of an active region. We studied limb-to-limb observation of the active region (NOAA 12687) obtained between 14th and 25th November 2017. We analyzed spectroscopic data simultaneously obtained from Hinode/EIS and IRIS in six wavelengths (MgII, CII, SiIV, FeXII, FeXIII, and FeXIV). After the high-precision alignment (accuracy of the Hinode pixel size) of the raster maps, we studied the mutual relation between the plasma properties for each line, as well as compared the plasma properties in the close formation temperature lines. To find the most characteristic spectra, we classified the spectra in each wavelength using the machine learning technique k-means. We found that the fluxes of the lines formed in the close temperatures are highly correlated in the chromosphere via transition region to the corona. In the corona, the Doppler velocities are well correlated too. Despite high-correlation between the transition region and coronal fluxes, the Doppler velocities are independent in our active region. In coronal lines, the average non-thermal velocity is higher in the upflow region than the active region core. In the transition region, the velocities are similar; thus the non-thermal motions are essential in the coronal upflow. We found several mutual relations between the plasma parameters in different spectral lines. These relations and the spectra classification results suggest that the plasma upflow begins in the solar corona, but the nature of the upflow region can be determined from the underlying layers.