Magnetic field inference in active region coronal loops using coronal rain clumps

Context. Densely packed coronal loops are rooted in photospheric plages in the vicinity of active regions on the Sun. The photospheric magnetic features underlying these plage areas are patches of mostly unidirectional magnetic field extending several arcsec on the solar surface. Aims. We aim to explore the transient nature of the magnetic field, its mixed-polarity characteristics, and the associated energetics in the active region plage using high spatial resolution observations and numerical simulations. Methods. We used photospheric Fe I 6173 Å spectropolarimetric observations of a decaying active region obtained from the Swedish 1-m Solar Telescope (SST). These data were inverted to retrieve the photospheric magnetic field underlying the plage as identified in the extreme-ultraviolet emission maps obtained from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). To obtain better insight into the evolution of extended unidirectional magnetic field patches on the Sun, we performed 3D radiation magnetohydrodynamic simulations of magnetoconvection using the MURaM code. Results. The observations show transient magnetic flux emergence and cancellation events within the extended predominantly unipolar patch on timescales of a few 100 s and on spatial scales comparable to granules. These transient events occur at the footpoints of active region plage loops. In one case the coronal response at the footpoints of these loops is clearly associated with the underlying transient. The numerical simulations also reveal similar magnetic flux emergence and cancellation events that extend to even smaller spatial and temporal scales. Individual simulated transient events transfer an energy flux in excess of 1 MW m−2 through the photosphere. Conclusions. We suggest that the magnetic transients could play an important role in the energetics of active region plage. Both in observations and simulations, the opposite-polarity magnetic field brought up by transient flux emergence cancels with the surrounding plage field. Magnetic reconnection associated with such transient events likely conduits magnetic energy to power the overlying chromosphere and coronal loops.

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Solar stereoscopy – where are we and what developments do we require to progress?

Annales Geophysicae ◽

10.5194/angeo-27-2925-2009 ◽

2009 ◽

Vol 27 (7) ◽

pp. 2925-2936 ◽

Cited By ~ 10

Author(s):

T. Wiegelmann ◽

B. Inhester ◽

L. Feng

Keyword(s):

Magnetic Field ◽

Active Region ◽

Coronal Magnetic Field ◽

Reconstruction Error ◽

Physical Parameters ◽

Coronal Loops ◽

Reconstruction Problem ◽

Temperature Plasma ◽

Solid Objects ◽

Polar Plumes

Abstract. Observations from the two STEREO-spacecraft give us for the first time the possibility to use stereoscopic methods to reconstruct the 3-D solar corona. Classical stereoscopy works best for solid objects with clear edges. Consequently an application of classical stereoscopic methods to the faint structures visible in the optically thin coronal plasma is by no means straight forward and several problems have to be treated adequately: 1) First there is the problem of identifying one-dimensional structures – e.g. active region coronal loops or polar plumes- from the two individual EUV-images observed with STEREO/EUVI. 2) As a next step one has the association problem to find corresponding structures in both images. This becomes more difficult as the angle between STEREO-A and B increases. 3) Within the reconstruction problem stereoscopic methods are used to compute the 3-D-geometry of the identified structures. Without any prior assumptions, e.g., regarding the footpoints of coronal loops, the reconstruction problem has not one unique solution. 4) One has to estimate the reconstruction error or accuracy of the reconstructed 3-D-structure, which depends on the accuracy of the identified structures in 2-D, the separation angle between the spacecraft, but also on the location, e.g., for east-west directed coronal loops the reconstruction error is highest close to the loop top. 5) Eventually we are not only interested in the 3-D-geometry of loops or plumes, but also in physical parameters like density, temperature, plasma flow, magnetic field strength etc. Helpful for treating some of these problems are coronal magnetic field models extrapolated from photospheric measurements, because observed EUV-loops outline the magnetic field. This feature has been used for a new method dubbed "magnetic stereoscopy". As examples we show recent application to active region loops.

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A Thermal Catastrophe in a Resonantly Heated Coronal Loop

Symposium - International Astronomical Union ◽

10.1017/s0074180900030059 ◽

1983 ◽

Vol 102 ◽

pp. 397-400

Author(s):

P.C.H. Martens ◽

M. Kuperus

Keyword(s):

Magnetic Field ◽

Thermal Stability ◽

Coronal Loop ◽

Coronal Loops ◽

Natural Explanation ◽

X Ray ◽

Magnetic Field Topology ◽

Coronal Rain ◽

The Magnetic Field ◽

Thermal Stability Of

A theory for the thermal stability of hot coronal loops is presented, which is based on the resonant electrodynamic heating theory of Ionson (1982) and the evaporation/condensation scenario of Krall and Antiochos (1980). The theory predicts that gradual changes in the length of a loop or in its magnetic field strength can trigger catastrophic changes in the X-ray visibility of the loop, without the need for a change in the magnetic field topology.A natural explanation is thereby given for the observations of X-ray brightenings in loops and loop evacuations with coronal rain.

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Comparison of Two Coronal Magnetic Field Models to Reconstruct a Sigmoidal Solar Active Region with Coronal Loops

The Astrophysical Journal ◽

10.3847/1538-4357/aa76e1 ◽

2017 ◽

Vol 842 (2) ◽

pp. 119 ◽

Cited By ~ 11

Author(s):

Aiying Duan ◽

Chaowei Jiang ◽

Qiang Hu ◽

Huai Zhang ◽

G. Allen Gary ◽

...

Keyword(s):

Magnetic Field ◽

Active Region ◽

Coronal Magnetic Field ◽

Solar Active Region ◽

Coronal Loops

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USING CORONAL LOOPS TO RECONSTRUCT THE MAGNETIC FIELD OF AN ACTIVE REGION BEFORE AND AFTER A MAJOR FLARE

The Astrophysical Journal ◽

10.1088/0004-637x/783/2/102 ◽

2014 ◽

Vol 783 (2) ◽

pp. 102 ◽

Cited By ~ 46

Author(s):

A. Malanushenko ◽

C. J. Schrijver ◽

M. L. DeRosa ◽

M. S. Wheatland

Keyword(s):

Magnetic Field ◽

Active Region ◽

Coronal Loops ◽

Major Flare ◽

Before And After ◽

The Magnetic Field

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Signature and escape of highly fractionated plasma in an active region

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab2681 ◽

2021 ◽

Vol 508 (2) ◽

pp. 1831-1841

Author(s):

David H Brooks ◽

Stephanie L Yardley

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Active Region ◽

Active Regions ◽

Abundance Ratio ◽

Elemental Abundance ◽

Composition Analysis ◽

Closed Field ◽

Coronal Loops ◽

Magnetic Field Model

ABSTRACT Accurate forecasting of space weather requires knowledge of the source regions where solar energetic particles (SEP) and eruptive events originate. Recent work has linked several major SEP events in 2014, January, to specific features in the host active region (AR 11944). In particular, plasma composition measurements in and around the footpoints of hot, coronal loops in the core of the active region were able to explain the values later measured in situ by the Wind spacecraft. Due to important differences in elemental composition between SEPs and the solar wind, the magnitude of the Si/S elemental abundance ratio emerged as a key diagnostic of SEP seed population and solar wind source locations. We seek to understand if the results are typical of other active regions, even if they are not solar wind sources or SEP productive. In this paper, we use a novel composition analysis technique, together with an evolutionary magnetic field model, in a new approach to investigate a typical solar active region (AR 11150), and identify the locations of highly fractionated (high Si/S abundance ratio) plasma. Material confined near the footpoints of coronal loops, as in AR 11944, that in this case have expanded to the AR periphery, show the signature, and can be released from magnetic field opened by reconnection at the AR boundary. Since the fundamental characteristics of closed field loops being opened at the AR boundary is typical of active regions, this process is likely to be general.

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Magnetic field topology by MDI data: Active region

Astronomy Letters ◽

10.1134/s1063773712070055 ◽

2012 ◽

Vol 38 (8) ◽

pp. 531-542 ◽

Cited By ~ 4

Author(s):

N. G. Makarenko ◽

I. S. Knyazeva ◽

L. M. Karimova

Keyword(s):

Magnetic Field ◽

Active Region ◽

Magnetic Field Topology

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The Persistence of Apparent Non-Magnetostatic Equilibrium in NOAA 11035

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315004366 ◽

2014 ◽

Vol 10 (S305) ◽

pp. 35-41

Author(s):

Sarah A. Jaeggli

Keyword(s):

Magnetic Field ◽

Active Region ◽

Strong Magnetic Field ◽

Solar Atmosphere ◽

Activity Cycle ◽

Opposite Polarity ◽

Unusual Feature ◽

Complete Picture

AbstractNOAA 11035 was a highly sheared active region that appeared in December 2009 early in the new activity cycle. The leading polarity sunspot developed a highly unusual feature in its penumbra, an opposite polarity pore with a strong magnetic field in excess of 3500 G along one edge, which persisted for several days during the evolution of the region. This region was well observed by both space- and ground-based observatories, including Hinode, FIRS, TRACE, and SOHO. These observations, which span wavelength and atmospheric regimes, provide a complete picture of this unusual feature which may constitute a force-free magnetic field in the photosphere which is produced by the reconnection of magnetic loops low in the solar atmosphere.

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