Determination of Differential Emission Measure from Solar Extreme Ultraviolet Images

Su, Yang; Veronig, Astrid; Hannah, I. G.; Cheung, Mark C. M.; Dennis, B. R.; Holman, Gordon D.; Gan, Weiqun; Li, Youping

doi:10.3847/2041-8213/aab436

Cited by 115 publications

(99 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the corresponding 1600Å image, the bright flare ribbons became more conspicuous (panel (b3)). Moreover, we investigate the temperature properties of the flux rope with the differential emission measure (DEM) method by employing the sparse inversion code (Cheung et al 2015;Su et al 2018). A set of AIA images taken at 13:16:40 UT in the 6 channels (i.e, 94, 131, 171, 193, 211, and 335Å) are used, and the EM maps at different temperature ranges are shown in panels (c)-(e).…”

Section: Resultsmentioning

confidence: 99%

Two-step Evolution of a Rising Flux Rope Resulting in a Confined Solar Flare

Yang

Zhang

Song

et al. 2019

ApJ

View full text Add to dashboard Cite

Combining the Solar Dynamics Observatory and the New Vacuum Solar Telescope observations, we study a confined flare triggered by a rising flux rope within the trailing sunspots of active region 12733. The flux rope lying above the sheared polarity inversion line can be constructed through magnetic extrapolation but could not be detected in multi-wavelength images at the pre-flare stage. The conspicuous shearing motions between the opposite-polarity fields in the photosphere are considered to be responsible for the flux rope formation. The maximum twist of the flux rope is as high as −1.76, and then the flux rope rises due to the kink instability. Only when the flare starts can the flux rope be observed in high-temperature wavelengths. The differential emission measure results confirm that this flux rope is a high-temperature structure. Associated with the rising flux rope, there appear many post-flare loops and a pair of flare ribbons. When the rising flux rope meets and reconnects with the large-scale overlying field lines, a set of large-scale twisted loops are formed, and two flare ribbons propagating in opposite directions appear on the outskirts of the former ribbons, indicating that the twist of the flux rope is transferred to a much larger system. These results imply that the external reconnection between the rising flux rope and the large-scale overlying loops plays an important role in the confined flare formation.

show abstract

Section: Resultsmentioning

confidence: 99%

Two-step Evolution of a Rising Flux Rope Resulting in a Confined Solar Flare

Yang

Zhang

Song

et al. 2019

ApJ

View full text Add to dashboard Cite

show abstract

“…To derive the size of each blob, we put a line that is perpendicular to the plasma sheet across the blob, With observations in the AIA 94 Å, 131 Å, 171 Å, 193 Å, 211 Å and 335 Å channels, we performed a differential emission measure (DEM, see Cheung et al 2015;Su et al 2018;Xue et al 2020a;Samanta et al 2021) analysis to investigate plasma properties in the reconnection region. The results are shown in Fig.…”

Section: (A)mentioning

confidence: 99%

Formation of solar coronal loops through magnetic reconnection in an emerging active region

Hou¹,

Chen²,

Zhu³

et al. 2021

Preprint

View full text Add to dashboard Cite

Coronal loops are building blocks of solar active regions (ARs). However, their formation is not well understood. Here we present direct observational evidence for the formation of coronal loops through magnetic reconnection as new magnetic fluxes emerge to the solar atmosphere. Observations in the EUV passbands of SDO/AIA clearly show the newly formed loops following magnetic reconnection within a vertical current sheet. Formation of the loops is also seen in the H&#945; images taken by NVST. The SDO/HMI observations show that a positive-polarity flux concentration moves toward a negative-polarity one with a speed of ~0.5 km s-1&#160;before the apparent formation of coronal loops. During the formation of coronal loops, we found signatures of flux cancellation and subsequent enhancement of the transverse field between the two polarities. We have reconstructed the three-dimensional magnetic field structure through a magnetohydrostatic model, which shows field lines consistent with the loops in AIA images. Numerous bright blobs with a width of ~1.5 Mm appear intermittently in the current sheet and move upward with apparent velocities of ~80 km s-1. We have also identified plasma blobs moving to the footpoints of the newly formed large loops, with apparent velocities ranging from 30 to 50 km s-1. A differential emission measure analysis shows that the temperature, emission measure and density of the bright blobs are 2.5-3.5 MK, 1.1-2.3&#215;1028&#160;cm-5&#160;and 8.9-12.9&#215;109&#160;cm-3, respectively. Power spectral analysis of these blobs indicates that the magnetic reconnection is inconsistent with the turbulent reconnection scenario.

show abstract

“…Observations taken from six EUV channels of SDO/AIA (94 Å, 131 Å, 171 Å, 193 Å, 211 Å, and 335 Å) were used to calculate the DEM(T) distribution for each pixel. We used an improved version (Su et al 2018) of the sparse inversion code (Cheung et al 2015). The derived solutions provide valuable information by mapping the thermal plasma from 0.3 to 30 MK.…”

Section: Dem Analysismentioning

confidence: 99%

Ultra-long and quite thin coronal loop without significant expansion

Yuan

Goossens

et al. 2020

A&A

Self Cite

View full text Add to dashboard Cite

Context. Coronal loops are the basic building blocks of the solar corona. They are related to the mass supply and heating of solar plasmas in the corona. However, their fundamental magnetic structures are still not well understood. Most coronal loops do not expand significantly, but the diverging magnetic field would have an expansion factor of about 5−10 over one pressure scale height. Aims. We investigate a unique coronal loop with a roughly constant cross section. The loop is ultra long and quite thin. A coronal loop model with magnetic helicity is presented to explain the small expansion of the loop width. Methods. This coronal loop was predominantly detectable in the 171 Å channel of the Atmospheric Imaging Assembly (AIA). Then, the local magnetic field line was extrapolated within a model of the potential field source-surface. Finally, the differential emission measure analysis made from six AIA bandpasses was applied to obtain the thermal properties of this loop. Results. This coronal loop has a projected length of roughly 130 Mm, a width of about 1.5 ± 0.5 Mm, and a lifetime of about 90 min. It follows an open magnetic field line. The cross section expanded very little (i.e., 1.5−2.0) along the loop length during its whole lifetime. This loop has a nearly constant temperature at about 0.7 ± 0.2 MK, but its density exhibits the typical structure of a stratified atmosphere. Conclusions. We use the theory of a thin twisted flux tube to construct a model for this nonexpanding loop and find that with sufficient twist, a coronal loop can indeed attain equilibrium. However, we cannot rule out other possibilities such as footpoint heating by small-scale reconnection or an elevated scale height by a steady flow along the loop.

show abstract

Determination of Differential Emission Measure from Solar Extreme Ultraviolet Images

Cited by 115 publications

References 25 publications

Two-step Evolution of a Rising Flux Rope Resulting in a Confined Solar Flare

Two-step Evolution of a Rising Flux Rope Resulting in a Confined Solar Flare

Formation of solar coronal loops through magnetic reconnection in an emerging active region

Ultra-long and quite thin coronal loop without significant expansion

Contact Info

Product

Resources

About

Determination of Differential Emission Measure from Solar Extreme Ultraviolet Images

Cited by 115 publications

References 25 publications

Two-step Evolution of a Rising Flux Rope Resulting in a Confined Solar Flare

Two-step Evolution of a Rising Flux Rope Resulting in a Confined Solar Flare

Formation of solar coronal loops through&#160;magnetic reconnection in an emerging active region

Ultra-long and quite thin coronal loop without significant expansion

Contact Info

Product

Resources

About

Formation of solar coronal loops through magnetic reconnection in an emerging active region