The chromospheric component of coronal bright points. Coronal and chromospheric responses to magnetic-flux emergence

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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Simulations of Switchback, Fragmentation and Sunspot Pair in δ-Sunspots during Magnetic Flux Emergence

Sensors ◽

10.3390/s21020586 ◽

2021 ◽

Vol 21 (2) ◽

pp. 586

Author(s):

Che-Jui Chang ◽

Jean-Fu Kiang

Keyword(s):

Magnetic Field ◽

Solar System ◽

Field Strength ◽

Magnetic Flux ◽

Initial Conditions ◽

Observation Data ◽

Flux Emergence ◽

Polarity Inversion ◽

Simulation Results ◽

Spot Type

Strong flares and coronal mass ejections (CMEs), launched from δ-sunspots, are the most catastrophic energy-releasing events in the solar system. The formations of δ-sunspots and relevant polarity inversion lines (PILs) are crucial for the understanding of flare eruptions and CMEs. In this work, the kink-stable, spot-spot-type δ-sunspots induced by flux emergence are simulated, under different subphotospheric initial conditions of magnetic field strength, radius, twist, and depth. The time evolution of various plasma variables of the δ-sunspots are simulated and compared with the observation data, including magnetic bipolar structures, relevant PILs, and temperature. The simulation results show that magnetic polarities display switchbacks at a certain stage and then split into numerous fragments. The simulated fragmentation phenomenon in some δ-sunspots may provide leads for future observations in the field.

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Magnetic Flux Emergence and Decay Rates for Preceder and Follower Sunspots Observed with HMI

The Astrophysical Journal ◽

10.3847/1538-4357/aa7052 ◽

2017 ◽

Vol 842 (1) ◽

pp. 3 ◽

Cited By ~ 10

Author(s):

A. A. Norton ◽

E. H. Jones ◽

M. G. Linton ◽

J. E. Leake

Keyword(s):

Magnetic Flux ◽

Decay Rates ◽

Flux Emergence

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Magnetic flux emergence

Scholarpedia ◽

10.4249/scholarpedia.4335 ◽

2007 ◽

Vol 2 (12) ◽

pp. 4335 ◽

Cited By ~ 8

Author(s):

Brigitte Schmieder ◽

Etienne Pariat

Keyword(s):

Magnetic Flux ◽

Flux Emergence

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Initiation of Coronal Mass Ejections by Magnetic Flux Emergence in the Framework of the Breakout Model

The Astrophysical Journal ◽

10.1086/595821 ◽

2008 ◽

Vol 689 (2) ◽

pp. L157-L160 ◽

Cited By ~ 21

Author(s):

F. P. Zuccarello ◽

A. Soenen ◽

S. Poedts ◽

F. Zuccarello ◽

C. Jacobs

Keyword(s):

Magnetic Flux ◽

Coronal Mass Ejections ◽

Flux Emergence

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Flare-CME Events Associated With a Superactive Region

Symposium - International Astronomical Union ◽

10.1017/s0074180900219451 ◽

2001 ◽

Vol 203 ◽

pp. 331-333 ◽

Cited By ~ 2

Author(s):

J. Wang ◽

J. Zhang ◽

T. Wang ◽

C. Zhang ◽

Y. Liu ◽

...

Keyword(s):

Magnetic Flux ◽

Coronal Mass Ejections ◽

Solar Surface ◽

Flare Activity ◽

Flux Emergence

In a few recent studies, 8 coronal mass ejections (CMEs) were identified to associate with a superactive region, AR 8100. They were all flare-CME events, It is found that the region is characterized by vigorous flux emergence and an imbalance of magnetic flux in two polarities. With the continuous flux emergence and its driven flux cancellation, the EUV dimming associated with flare activity increased in area. Whenever the dimming extended to an area of more than 50×50 square degrees on the solar surface, a flare in the region became CME-associated.

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