Magnetic Loops above a Small Flux-emerging Region Observed by IRIS, Hinode, and SDO

Abstract

I report on observations of a set of magnetic loops above a region with late-phase flux emergence taken by IRIS, Hinode and SDO. The loop system consists of many transition region loop threads with size of 5-12 ′′ in length and ∼ 0.5 ′′ in width and coronal loops with similar length and ∼ 2 ′′ width. Although the loop system consists of threads with different temperatures, most individual loop thread have temperature in a narrow range. In the middle of the loop system, it shows clear systematic blue-shifts of about 10 km s −1 in the transition region that is consistent with a flux emerging picture, while red-shifts of about 10 km s −1 in the corona is observed. The nonthermal velocity of the loop system are smaller than the surrounding region in the transition region but are comparable in the corona. The electron densities of the coronal counterpart of the loop system range from 1 × 10 9 cm −3 to 4 × 10 9 cm −3 . Electron density of a transition region loop is also measured and found to be about 5 × 10 10 cm −3 , a magnitude larger than that in the coronal loops. In agreement with imaging data, the temperature profiles derived from the differential emission measurement technique confirms that some of the loops have been heated to corona. Our observations indicate that the flux emergence in its late phase is much different from that at the early stage. While the observed transition region is dominated by emerging flux, these emerging loops could be heated to corona and the heatings most likely take place only after they reaching the transition region or lower corona.

Spectroscopic and imaging observations of transient hot and cool loops by IRIS and SDO

“…Densities obtained here for cool loop is quite higher than those reported by Huang et al (2015) of about 10 10 cm −3 at transition region temperature. However, densities are comparable with findings of Huang (2018) for a cool loop reaching temperature up to 2 MK. For hot loop, Gupta et al (2018) found electron densities to be 10 11.5 cm −3 for transition region temperature whereas Testa & Reale (2020) found densities reaching of the order of 10 10 cm −3 at hot coronal temperatures.…”

Impulsive Coronal Heating from Large-scale Magnetic Rearrangements: From IRIS to SDO/AIA

“…The interaction of small loops has been taken as explanation of a small flare observed with IRIS (Alissandrakis et al 2017), and our study provides direct evidence from the morphology observed in the hot AIA channels counterparts. Many recent papers have studied simultaneous observations from IRIS and SDO/AIA to investigate magnetic rearrangements causing localized brightenings in the transition region, and likely related with flux emergence (e.g., Jiang et al 2015;Toriumi et al 2017;Guglielmino et al 2018;Huang 2018;Tian et al 2018;Guglielmino et al 2019). However we note that the coronal heating events we study here have quite different properties with respect to those events, in that they have generally lower Doppler shift velocities (up to ∼ ±30 km/s) and show heating of the overlying coronal loops to several MK.…”

Solar ultraviolet bursts in a coordinated observation of IRIS, Hinode and SDO

“…Moreover, some coronal loops can be seen from the AIA 131 and 171 Å images in the same region. It is likely that cool and hot loops are mixed in this region [63,64,65].…”