Implications of spicule activity on coronal loop heating and catastrophic cooling

Abstract

We report on the properties of coronal loop foot-point heating with observations at the highest resolution, from the CRisp Imaging Spectro-Polarimeter (CRISP) located at the Swedish 1-m Solar Telescope (SST) and co-aligned NASA Solar Dynamics Observatory (SDO) observations, of Type II spicules in the chromosphere and their signatures in the EUV corona. Here, we address one important issue, as to why there is not always a one-to-one correspondence, between Type II spicules and hot coronal plasma signatures, i.e. beyond TR temperatures. We do not detect any difference in their spectral properties in a quiet Sun region compared to a region dominated by coronal loops. On the other hand, the number density close to the foot-points in the active region is found to be an order of magnitude higher than in the quiet Sun case. A differential emission measure analysis reveals a peak at ∼5 × 105 K on the order of 1022 cm−5 K−1. Using this result as a constraint, we conduct numerical simulations and show that with an energy input of 1.25 × 1024 erg (corresponding to ∼10 RBEs contributing to the burst) we manage to reproduce the observation very closely. However, simulation runs with lower thermal energy input do not reproduce the synthetic AIA 171 Å signatures, indicating that there is a critical number of spicules required in order to account for the AIA 171 Å signatures in the simulation. Furthermore, the higher energy (1.25 × 1024 ergs) simulations reproduce catastrophic cooling with a cycle duration of ∼5 hours, matching a periodicity we observe in the EUV observations.

Solar Spicules, Filigrees, and Solar Wind Switchbacks

“…This is the region where the extrapolated field lines run along the loop-like EUV bright structure, and the spicular activity is correlated with the EUV emission. This result is in favor of the selective correlation between Hα ejection and EUV emission found by Nived et al (2022).…”

“…In other regions without EUV brightness, we fail to detect such a periodic magnetic activity. Such a selective appearance of the EUV counterparts in regions with magnetic activity may imply the presence of a threshold for the correlation between spicule activity and EUV activity (see Nived et al 2022). 3.…”

“…In general, spicules and EUV emission do not correlate well with each other (e.g., Nived et al 2022), which yields an impression that they are not driven by reconnection. We nonetheless look for a possible relation between them by comparing spicule activity and magnetic property in the regions with and without EUV brightness.…”

“…First, they are not accompanied by impulsive brightening at their bases (called hereafter jet bright brightening or JBP) if they are reconnection-driven jets (Sterling & Moore 2016;. Another shortcoming is that correlation between spicular activity and EUV and X-ray jets remains unclear (Uritsky et al 2021;Nived et al 2022), and that spicules may not be energetic enough to contribute to coronal heating (Klimchuk 2012), unlike EUV or X-ray jets. Finally, they do not seem to be associated with magnetic eruption that is essential for larger scale solar eruptions.…”

On the Relation Between Coronal Green Line Brightness and Magnetic Fields Intensity

“…The coronal magnetic field gives information on the physical conditions of the sources, such as the sunspots, hot corona, solar eruptions and large-scale coronal loop structures (Brooks et al 2021). Therefore, routine and accurate measurements of the coronal magnetic field are crucial for the identification of the causes of various violent eruptions, the explanation of coronal heating mechanism (Ji et al 2012;Nived et al 2022) and the acceleration mechanism of solar wind (Stakhiv et al 2015(Stakhiv et al , 2016, as well as the origin of the solar magnetic field (Lin & Forbes 2000;Shen et al 2022).…”