Sunspot Light Walls Suppressed by Nearby Brightenings

Abstract

Light walls, as ensembles of oscillating bright structures rooted in sunspot light bridges, have not been well studied, although they are important for understanding sunspot properties. Using the Interface Region Imaging Spectrograph and Solar Dynamics Observatory observations, here we study the evolution of two oscillating light walls each within its own active region (AR). The emission of each light wall decays greatly after the appearance of adjacent brightenings. For the first light wall, rooted within AR 12565, the average height, amplitude, and oscillation period significantly decrease from 3.5 Mm, 1.7 Mm, and 8.5 min to 1.6 Mm, 0.4 Mm, and 3.0 min, respectively. For the second light wall, rooted within AR 12597, the mean height, amplitude, and oscillation period of the light wall decrease from 2.1 Mm, 0.5 Mm, and 3.0 min to 1.5 Mm, 0.2 Mm, and 2.1 min, respectively. Particularly, a part of the second light wall becomes even invisible after the influence of nearby brightening. These results reveal that the light walls are suppressed by nearby brightenings. Considering the complex magnetic topology in light bridges, we conjecture that the fading of light walls may be caused by a drop in the magnetic pressure, where flux is cancelled by magnetic reconnection at the site of the nearby brightening. Another hypothesis is that the wall fading is due to the suppression of driver source (p-mode oscillation), resulting from the nearby avalanche of downward particles along reconnected brightening loops.

Doppler shift oscillations of a sunspot detected by CYRA and IRIS

“…A period of nearly five minutes can be detected in Doppler velocities of CO 3-2 R14 and 7-6 R67 lines, which is consistent with previous findings in white light images or continuum spectrum (Beckers & Schultz 1972;Lites 1988;Nagashima et al 2007;Yuan et al 2014;Su et al 2016), and might be considered the solar p-mode waves in the photosphere (Thomas 1985;Bogdan 2000;Solanki 2003). While a period of roughly three minutes is found in the Doppler velocities of the CO 3-2 R14 and Mg ii k lines, which agrees closely with the previous observational results in UV-infrared lines or images at the sunspot umbra (e.g., Solanki et al 1996;Bogdan 2000;Fludra 2001;Maltby et al 2001;Centeno et al 2008;Tian et al 2014;Khomenko & Collados 2015;Yang et al 2017). They are explained as the resonant modes of sunspot oscillations (Uexkuell et al 1983;Thomas 1984;Gurman 1987;Khomenko & Collados 2015).…”

“…The dominant period of sunspot oscillations in the low solar atmosphere (photosphere) is about five minutes (Beckers & Schultz 1972;Lites 1988;Wang et al 2020), which is believed to be related to the five-minute p-mode wave (Thomas 1985;Bogdan 2000;Solanki 2003;Yuan 2015). Instead, sunspot oscillations in the middle solar atmosphere (chromosphere and transition regions) often have a typical period of around three minutes, which can also be observed at photospheric sunspots (Solanki et al 1996;Bogdan 2000;Yang et al 2017). They are thought to be resonant modes of sunspot oscillations, with cavities that may be located at sunspot umbrae in the solar layers of sub-photospheres (Scheuer & Thomas 1981;Thomas 1984Thomas , 1985 or chromospheres (Uexkuell et al 1983;Gurman 1987;Khomenko & Collados 2015).…”

Sunspot penumbral filaments intruding into a light bridge and the resultant reconnection jets

“…The structures mentioned above are usually derived from local inhomogeneous magnetic field and magneto-convection, indicating the complexity of sunspot magnetic and thermal properties (Spruit & Scharmer 2006;Schüssler & Vögler 2006;Rimmele 2008;Rempel et al 2009;Reardon et al 2013). As a result of the deviation from sunspot background conditions, various dynamic phenomena especially surge-like activities frequently occur around these structures, such as surges and light walls above the light bridges (Roy 1973;Asai et al 2001;Shimizu et al 2009;Louis et al 2014a;Yang et al 2015Yang et al , 2016Yang et al , 2017Bharti 2015;Robustini et al 2016;Hou et al 2016aHou et al ,b, 2017Zhang et al 2017;Tian et al 2018;Bai et al 2019), transient jets above a penumbral filament intrusion into the umbra (Bharti et al 2017), and ubiquitous penumbral microjets in the penumbral chromosphere (Katsukawa et al 2007b;Jurčák & Katsukawa 2008;Nakamura et al 2012;Tiwari et al 2016;Drews & Rouppe van der Voort 2017;Samanta et al 2017;Esteban Pozuelo et al 2019; Rouppe van der Voort & Drews 2019). These surge-like activities display an impressive variety of morphological, temporal, and spectral properties.…”

Magnetoacoustic Waves in a Magnetic Slab Embedded in an Asymmetric Magnetic Environment. II. Thin and Wide Slabs, Hot and Cold Plasmas

“…This limit may have both photospheric or coronal applications, if we describe them in Cartesian rather than cylindrical geometry. Such a description may be applicable to various solar phenomena, such as prominences (see Arregui et al 2012), sunspot light bridges and light walls (Yuan et al 2014;Yang et al 2016Yang et al , 2017, MBPs (Utz et al 2009;Liu et al 2018), or any thin and magnetized plasmaastrophysical object that is sandwiched between uniform, homogeneous but asymmetric magnetized semi-infinite plasma environments as a first approximation.…”