Magnetic Flux Emergence, Activity, Eruptions and Magnetic Clouds: Following Magnetic Field from the Sun to the Heliosphere

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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Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

International Astronomical Union Colloquium ◽

10.1017/s0252921100064630 ◽

2000 ◽

Vol 179 ◽

pp. 263-264

Author(s):

K. Sundara Raman ◽

K. B. Ramesh ◽

R. Selvendran ◽

P. S. M. Aleem ◽

K. M. Hiremath

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Magnetic Flux ◽

Ultra Violet ◽

Active Regions ◽

Morphological Properties ◽

Energy Storage And Conversion ◽

The Sun ◽

X Rays ◽

The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

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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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ENERGY INJECTION VIA FLUX EMERGENCE ON THE SUN DEPENDING ON THE GEOMETRIC SHAPE OF MAGNETIC FIELD

The Astrophysical Journal ◽

10.1088/0004-637x/731/2/122 ◽

2011 ◽

Vol 731 (2) ◽

pp. 122 ◽

Cited By ~ 4

Author(s):

T. Magara

Keyword(s):

Magnetic Field ◽

Geometric Shape ◽

The Sun ◽

Flux Emergence

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A Quantitative Study of Magnetic Flux Transport on the Sun

Symposium - International Astronomical Union ◽

10.1017/s0074180900029934 ◽

1983 ◽

Vol 102 ◽

pp. 273-278 ◽

Cited By ~ 2

Author(s):

N.R. Sheeley ◽

J.P. Boris ◽

T.R. Young ◽

C.R. DeVore ◽

K.L. Harvey

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Quantitative Study ◽

Differential Rotation ◽

Meridional Circulation ◽

Diffusion Constant ◽

The Sun ◽

Flux Transport ◽

Field Reversal ◽

Best Fit

A computational model, based on diffusion, differential rotation, and meridional circulation, has been developed to simulate the transport of magnetic flux on the Sun. Using Kitt Peak magnetograms as input, we have determined a best-fit diffusion constant by comparing the computed and observed fields at later times. Our value of 730 ± 250 km2/s is consistent with Leighton's (1964) estimate of 770–1540 km2/s and is significantly larger than Mosher's (1977) estimate of 200–400 km2/s. This suggests that diffusion may be fast enough to account for the observed polar magnetic field reversal without requiring a significant assist from meridional currents.

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Slow twists of solar magnetic flux tubes and the polar magnetic field of the Sun

Geophysical Research Letters ◽

10.1029/gl016i008p00919 ◽

1989 ◽

Vol 16 (8) ◽

pp. 919-922 ◽

Cited By ~ 44

Author(s):

Joseph V. Hollweg ◽

Martin A. Lee

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

The Sun ◽

Flux Tubes ◽

Polar Magnetic Field ◽

Magnetic Flux Tubes

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Solar and stellar magnetic flux tubes

Symposium - International Astronomical Union ◽

10.1017/s0074180900083236 ◽

1996 ◽

Vol 176 ◽

pp. 201-216

Author(s):

Sami K. Solanki

Keyword(s):

Magnetic Field ◽

Magnetic Properties ◽

Magnetic Flux ◽

Large Range ◽

The Sun ◽

Flux Tubes ◽

Magnetic Elements ◽

Turbulent Pressure ◽

Magnetic Flux Tubes ◽

The Magnetic Field

The magnetic field of the Sun is mainly concentrated into intense magnetic flux tubes having field strengths of the order of 1 kG. In this paper an overview is given of the thermal and magnetic properties of these flux tubes, which are known to exhibit a large range in size, from the smallest magnetic elements to sunspots. Differences and similarities between the largest and smallest features are stressed. Some thoughts are also presented on how the properties of magnetic flux tubes are expected to scale from the solar case to that of solar-like stars. For example, it is pointed out that on giants and supergiants turbulent pressure may dominate over gas pressure as the main confining agent of the magnetic field. Arguments are also presented in favour of a highly complex magnetic geometry on very active stars. Thus the very large starspots seen in Doppler images probably are conglomerates of smaller (but possibly still sizable) spots.

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Modelling coronal electron density and temperature profiles of the Active Region NOAA 11855

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317003842 ◽

2016 ◽

Vol 12 (S328) ◽

pp. 149-151

Author(s):

J. M. Rodríguez Gómez ◽

L. E. Antunes Vieira ◽

A. Dal Lago ◽

J. Palacios ◽

L. A. Balmaceda ◽

...

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Physical Mechanism ◽

Magnetic Energy ◽

Plasma Temperature ◽

Coronal Magnetic Field ◽

Flux Emergence ◽

Vector Magnetic Field ◽

Atmospheric Phenomena ◽

Coronal Electron

AbstractThe magnetic flux emergence can help understand the physical mechanism responsible for solar atmospheric phenomena. Emerging magnetic flux is frequently related to eruptive events, because when emerging they can reconnected with the ambient field and release magnetic energy. We will use a physic-based model to reconstruct the evolution of the solar emission based on the configuration of the photospheric magnetic field. The structure of the coronal magnetic field is estimated by employing force-free extrapolation NLFFF based on vector magnetic field products (SHARPS) observed by HMI instrument aboard SDO spacecraft from Sept. 29 (2013) to Oct. 07 (2013). The coronal plasma temperature and density are described and the emission is estimated using the CHIANTI atomic database 8.0. The performance of the our model is compared to the integrated emission from the AIA instrument aboard SDO spacecraft in the specific wavelengths 171Å and 304Å.

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