Signatures of quiet Sun reconnection events in Ca ii, Hα, and Fe i

Abstract

We use observations of quiet Sun (QS) regions in the Hα 6563 Å, Ca ii 8542 Å and Fe i 6302 Å lines. We observe brightenings in the wings of the Hα and Ca ii combined with observations of the interacting magnetic concentrations observed in the Stokes signals of Fe i. These brightenings are similar to Ellerman bombs (EBs), i.e. impulsive bursts in the wings of the Balmer lines which leave the line cores unaffected. Such enhancements suggest that these events have similar formation mechanisms to the classical EBs found in active regions, with the reduced intensity enhancements found in the QS regions due to a weaker feeding magnetic flux. The observations also show that the quiet Sun Ellerman bombs (QSEBs) are formed at a higher height in the upper photosphere than the photospheric continuum level. Using simulations, we investigate the formation mechanism associated with the events and suggest that these events are driven by the interaction of magnetic field-lines in the upper photospheric regions. The results of the simulation are in agreement with observations when comparing the lightcurves, and in most cases we found that the peak in the Ca ii 8542 Å wing occurred before the peak in Hα wing. Moreover, in some cases, the line profiles observed in Ca ii are asymmetrical with a raised core profile. The source of heating in these events is shown by the MURaM simulations and is suggested to occur 430 km above the photosphere.

Signatures of ubiquitous magnetic reconnection in the lower solar atmosphere

“…We found episodes of flux cancellation in the photosphere that spatially and temporally coincide with QSEBs. This supports the idea that magnetic reconnection in the photosphere is the fundamental mechanism for QSEBs (Rouppe van der Voort et al 2016; Shetye et al 2018). Nonetheless, not all the QSEBs show flux cancellation in our data, and many appear with unipolar B LOS patches.…”

“…1−3, B1, and B2 are available at https://www.aanda.org Sun Ellerman bombs (QSEBs) are smaller in size and exhibit weaker enhancement of their Hα wings than their active region counterparts (Rouppe van der Voort et al 2016;Nelson et al 2017). QSEBs are also thought to originate through magnetic reconnection in the photosphere (Rouppe van der Voort et al 2016;Shetye et al 2018), similar to EBs.…”

Transient brightenings in the quiet Sun detected by ALMA at 3 mm

“…Direct evidence includes the detection of time variability of the intensity A&A 638, A62 (2020) (e.g., Berghmans et al 1998) or the emission measure (e.g., of clusters of pixels above some predefined threshold. In most studies, most of the detected events are spatially unresolved (e.g., Benz & Krucker 1999), but some events may exhibit a loop-like morphology (e.g., White et al 1995;Warren et al 2007), a jet-like morphology (e.g., Tian et al 2014;Alissandrakis et al 2015), show evidence of two-loop interactions (e.g., Shimizu et al 1994;Alissandrakis et al 2017a), or even resemble Ellerman bombs (e.g., Shetye et al 2018).…”

Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST)

“…Zachariadis, Alissandrakis, and Banos, 1987;Georgoulis et al, 2002;Ma et al, 2015, but see Rutten et al, 2013, who suggest these are distinct phenomena), suggesting that largerscale flux eruption may underlie their occurrence (Pariat et al, 2004), recent observations indicate that smaller, shorter-lived, and lower Hα-wing-intensity-contrast events also occur in the quiet Sun. These quiet-Sun Ellerman-like brightenings (Rouppe van der Voort, Rutten, and Vissers, 2016;Shetye et al, 2018) are similar to Ellerman bombs, but with typical size scales of ≈ 0.25 -0.5 arcseconds and lifetimes of less than a minute compared to arcseconds and minutes for Ellerman bombs proper (e.g. Roy and Leparskas, 1973;Kurokawa et al, 1982;Vissers, Rouppe van der Voort, and Rutten, 2013).…”