Statistical study of emerging flux regions and the response of the upper atmosphere

Abstract

We statistically study the properties of emerging flux regions (EFRs) and response of the upper solar atmosphere to the flux emergence using data from the Helioseismic and Magnetic Imager and the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. Parameters including total emerged flux, flux growth rate, maximum area, duration of the emergence and separation speed of the opposite polarities are adopted to delineate the properties of EFRs. The response of the upper atmosphere is addressed by the response of the atmosphere at different wavelengths (and thus at different temperatures). According to our results, the total emerged fluxes are in the range of (0.44−11.2)×1019 Mx while the maximum area ranges from 17 to 182 arcsec2. The durations of the emergence are between 1 and 12 h, which are positively correlated to both the total emerged flux and the maximum area. The maximum distances between the opposite polarities are 7–25 arcsec and are also positively correlated to the duration. The separation speeds are from 0.05 to 1.08 km s−1, negatively correlated to the duration. The derived flux growth rates are (0.1−1.3)×1019 Mx h−1, which are positively correlated to the total emerging flux. The upper atmosphere first responds to the flux emergence in the 1600Å chromospheric line, and then tens to hundreds of seconds later, in coronal lines, such as the 171Å (T = 105.8 K) and 211Å (T = 106.3 K) lines almost simultaneously, suggesting the successive heating of the atmosphere from the chromosphere to the corona.