Main Objective: To study how penumbral filaments and spines in sunspot penumbra, and moving magnetic features nearsunspot penumbra evolve, and what is their transition region response.
Scientific Justification: Sunspot penumbra is formed of filaments and spines (more vertical field between the horizontal-field filaments: Lites et al. 1993, ApJ; Tiwari et al. 2015, A&A). Although observations and modeling now largely agree on penumbral filaments being elongated magnetoconvection cells (Rempel 2012, ApJ; Tiwari et al. 2013, A&A), the interaction of filaments and spines and their evolution are not understood. The lifetime of penumbral filaments is not accurately known due to absence of high-resolution high-cadence spectropolarimetric data of sunspot penumbra for a large span of several to many hours. Moreover, chromospheric/transition-region/coronal dynamic events in sunspot penumbrae e.g., penumbral jets and bright dots might result from the evolution and/or interaction of filaments and spines. Bright Dots are moving bright dot-like transition region events in sunspot penumbrae (Tian et al. 2015, ApJL; Alpert et al. 2016, ApJ). Penumbral jets are narrow transient brightenings best seen in the chromosphere but are proposed to contribute to the transition region and coronal heating (Katsukawa et al. 2007, Sci.; Tiwari et al. 2016, ApJ, Vissers et al 2016).
Penumbral jets are proposed to form by magnetic reconnection between two filaments inclined at an acute angle (Katsukawa et al. 2007, Science), or between the spine field and the opposite polarity magnetic field present at the edges of filaments (Tiwari et al. 2016, ApJ) -- some largest jets form at the tails of filaments, dominant at the outer edges of penumbra. Penumbral jets could alternatively be fast propagating heat fronts (Rouppe van der Voort & Drews, 2019, A&A) - thus their formation mechanism remains unsettled. Some of larger jets also show twisting in them (similar to X-ray jets) but whether all penumbral jets twist remains to be explored using suitable IRIS observations (Tiwari et a. 2018, ApJ; Drews & Rouppe van der Voort 2020).
The proposed observations will also allow investigation of transition region response of moving magnetic features, found in and around sunspot penumbra.
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