Solar coronal heating from small-scale magnetic braids

Abstract

Relaxation of braided coronal magnetic fields through reconnection is thought to be a source of energy to heat plasma in active region coronal loops. However, observations of active region coronal heating associated with an untangling of magnetic braids remain sparse. One reason for this paucity could be the lack of coronal observations with a sufficiently high spatial and temporal resolution to capture this process in action. Using new observations with high spatial resolution (250-270 km on the Sun) and high cadence (3-10 s) from the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter, we observed the untangling of small-scale coronal braids in different active regions. The untangling is associated with impulsive heating of the gas in these braided loops. We assess that coronal magnetic braids overlying cooler chromospheric filamentary structures are perhaps more common. Furthermore, our observations show signatures of spatially coherent and intermittent coronal heating during the relaxation of the magnetic braids. Our study reveals the operation of gentle and impulsive modes of magnetic reconnection in the solar corona.

Picoflare jets power the solar wind emerging from a coronal hole on the Sun

“…Then through cross-correlation, we aligned each image to the first image in a given shorter sequence. Because the shorter sequences overlap, this resulted in a dataset in which all images from the whole observational sequence were aligned to the first image of the time series (53).…”

Polarisation of decayless kink oscillations of solar coronal loops

“…The imaging data from HRIEUV have a time cadence of 10 s, pixel size of 0.492 arcsec, and FoV of 2048 × 2048 pixels. The HRIEUV data is internally aligned using a cross correlation technique 56 to remove the spacecraft jitters. The co-temporal AIA images in 171 Å have a time cadence of 12 s and pixel size of 0.6 arcsec.…”

Fleeting Small-scale Surface Magnetic Fields Build the Quiet-Sun Corona

“…The EUI and SO/PHI data were further processed as follows. First, we coaligned all the EUI data to the first image of the time sequence using a cross-correlation technique described in Chitta et al (2022). We used these aligned level-2 EUI data at their native cadence to compute the light curves plotted in Figure 4.…”

“…Another traditional model of coronal heating is based on the energy dissipated in the process of untangling magnetic fields braided by slow stressing of footpoints (Parker 1988;Klimchuk 2006;Cirtain et al 2013;Chitta et al 2022). In this scenario, a typical QS coronal bright point with a loop length of 10 Mm might reach a steady state between the energy injected into the corona through slow footpoint motions and energy losses through radiation and conduction on timescales of 1.4 hr (Parker 1988).…”