Coronal Heating and Solar Wind Formation in Quiet Sun and Coronal Holes: A Unified Scenario

Abstract

Coronal holes (CHs) are darker than the quiet Sun (QS) when observed in coronal channels. This study aims to understand the similarities and differences between CHs and QS in the transition region using the Si iv 1394 Å line, recorded by the Interface Region Imaging Spectrograph, by considering the distribution of magnetic field measured by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. We find that Si iv intensities obtained in CHs are lower than those obtained in QS for regions with identical magnetic flux densities. Moreover, the difference in intensities between CHs and QS increases with increasing magnetic flux. For the regions with equal magnetic flux density, QS line profiles are more redshifted than those measured in CHs. Moreover, the blueshifts measured in CHs show an increase with increasing magnetic flux density unlike in the QS. The non-thermal velocities in QS, as well as in CHs, show an increase with increasing magnetic flux. However, no significant difference was observed in QS and CHs, albeit a small deviation at small flux densities. Using these results, we propose a unified model for the heating of the corona in the QS and in CHs and the formation of solar wind.

Properties of the C II 1334 Å line in Coronal Hole and Quiet Sun as observed by IRIS

“…Bryans et al (2020) found that some CHs may be identified through a marginal excess in the peak separation of the Mg II h line. Similarly, for Si IV line, Tripathi et al (2021) found that CHs and QS show differences in intensities and Doppler shifts for the regions with identical |B|, while no difference in the non-thermal width was observed.…”

“…The details of the IRIS observations are given in Table . 1. Note that DS1, DS2 and DS5 are the same ones used by Tripathi et al (2021). We use corresponding coordinated AIA data cubes for this study, while the full disk HMI cubes were cut out from Level-2 data.…”

“…This variability, and the dynamic nature of CHs is suggested by Gopalswamy et al (1999) to be a signature of solar wind acceleration and heating. Differences between CHs and QS have also been studied in chromosphere and transition region using the Mg II (Kayshap et al 2018;Bryans et al 2020) and Si IV lines (Tripathi et al 2021) recorded by the Interface Region Imaging Spectrograph (IRIS, De Pontieu et al 2014). Kayshap et al (2018) found that while there is no distinction in the distribution of the absolute photospheric magnetic flux density (|B|) in CH and QS, the QS shows excess intensity vis-à-vis CHs for regions with identical |B|.…”

“…Moreover, how do these properties vary with the underlying magnetic field? A detailed understanding of these questions will not only provide essential ingredients to further understand the heating and dynamic coupling of the solar atmosphere in CHs and QS, but also help us diagnose the origin & formation of the solar wind (see e.g., Hassler et al 1999;Tu et al 2005) and the recently observed switch-backs in the magnetic field (see e.g., Balogh et al 1999;Fisk 2003;Bale et al 2019;Fisk & Kasper 2020;Zank et al 2020;Tripathi et al 2021).…”

Synchronization of Small-scale Magnetic Features, Blinkers, and Coronal Bright Points

“…Due to such associations and various other properties of the transients, the process of magnetic reconnection is considered to be one of the key mechanisms for their generation. These transients observed ubiquitously throughout the solar atmospheric are further considered to play an essential role in transferring the mass and energy within the solar atmosphere (Parker 1988;Schrijver et al 1997;Moore et al 1999;Winebarger et al 2002;Yamauchi et al 2005;Alipour et al 2012;Priest 2014;) and formation of the solar wind including switchbacks (Hassler et al 1999;Tu et al 2005;Zank et al 2020;Tripathi et al 2021;Liang et al 2021;.…”