Relationship between the Horizontal Gradient of the Vertical Magnetic Field and the Horizontal Electric Current on the Photosphere in a Model Active Region of the Sun

2021 ◽  
Vol 61 (7) ◽  
pp. 956-963
Author(s):  
A. B. Nechaeva ◽  
I. N. Sharykin ◽  
I. V. Zimovets ◽  
F. Chen
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Electric Current ◽  
Horizontal Gradient ◽  
The Sun ◽  
Vertical Magnetic Field

scholarly journals Energetics of magnetic transients in a solar active region plage

2019 ◽  
Vol 623 ◽  
pp. A176 ◽  
Author(s):  
L. P. Chitta ◽  
A. R. C. Sukarmadji ◽  
L. Rouppe van der Voort ◽  
H. Peter
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Magnetic Flux ◽  
Numerical Simulations ◽  
Extreme Ultraviolet ◽  
Spatial Scales ◽  
Coronal Loops ◽  
The Sun ◽  
Flux Emergence ◽  
Transient Events

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.

scholarly journals On the regions over sunspots as studied by polarization observations on centimeter wavelengths

1959 ◽  
Vol 9 ◽  
pp. 125-128
Author(s):  
G. Gelfreich ◽  
D. Korol'Kov ◽  
N. Rishkov ◽  
N. Soboleva
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Radio Emission ◽  
Brightness Temperature ◽  
The Sun ◽  
Polarization Rotation

The observations of the sun at centimeter wavelengths made at Pulkovo in 1956–58 have shown: (1) There are regions of appreciable size over the majority of sunspots that have “enhanced” radio emission at centimeter wavelengths [1]. The nature of this emission shows that it belongs to the slowly varying component. In fact, as long as a group of sunspots persists, the flux of such an active region preserves its almost constant value. (2) The emission is partly circular, the polarized flux changing in magnitude but inappreciably. The sign of polarization rotation remains constant [2], which appears to be positive proof that a rather intense and stable magnetic field exists in these regions. (3) The extent of the regions is about that of the spot nuclei [3]. (4) Their brightness temperature amounts to several million degrees. (5) The height at which enhanced radio emission is produced is of the order 1.07 ± 0.02R⊙ [4].

scholarly journals Study of an active region of the Sun during three rotation periods

1968 ◽  
Vol 35 ◽  
pp. 85-91
Author(s):  
Constantin J. Macris ◽  
T. J. Prokakis
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
High Density ◽  
The Sun ◽  
Rotation Periods ◽  
The Magnetic Field ◽  
Active Centres

The abnormal evolution of an active region during three solar rotations is studied. The high density of flares during the second and third rotation seems to be caused by the collision of new active centres with existing ones.The increase of the activity is probably due to the disturbance of the magnetic field which became more complex because of the appearance of new centres near the original one.

scholarly journals The proper motions of sunspots and the magnetic field of active regions

1968 ◽  
Vol 35 ◽  
pp. 211-213
Author(s):  
G. V. Kuklin
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Proper Motion ◽  
Active Regions ◽  
The Sun ◽  
Proper Motions ◽  
The Magnetic Field

According to our program of sunspot proper motion investigations (Kuklin and Syklen, 1966) we study the interdependence of the sunspot proper motions inside the group and the magnetic field of the whole group or active region. This aspect of the dynamics of matter in disturbed regions of the Sun was not considered practically up to the last time.

scholarly journals The balance of magnetic fluxes in active regions

1968 ◽  
Vol 35 ◽  
pp. 47-49 ◽  
Author(s):  
Jan Olof Stenflo
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Active Region ◽  
Solar Surface ◽  
Active Regions ◽  
Basic Feature ◽  
The Sun ◽  
Magnetic Disturbance ◽  
The Magnetic Field

According to modern theories of the solar cycle, active regions on the Sun are caused by a magnetic disturbance penetrating the solar surface from below. Sunspots, filaments, flares and other conspicuous events in an active region seem to be only secondary phenomena, the basic feature being the magnetic field itself.

scholarly journals A long-duration active region: Evolution and quadrature observations of ejective events

2016 ◽  
Vol 12 (S327) ◽  
pp. 60-66
Author(s):  
H. Cremades ◽  
C. H. Mandrini ◽  
M. C. López Fuentes ◽  
L. Merenda ◽  
I. Cabello ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Remote Sensing ◽  
Active Region ◽  
Remote Sensing Data ◽  
Time Interval ◽  
The Sun ◽  
Weather Forecasts ◽  
Long Duration ◽  
Triggering Mechanisms ◽  
Region Evolution

AbstractUnknown aspects of the initiation, evolution, and associated phenomena of coronal mass ejections (CMEs), together with their capability of perturbing the fragile technological equilibrium on which nowadays society depends, turn them a compelling subject of study. While space weather forecasts are thus far not able to predict when and where in the Sun will the next CME take place, various CME triggering mechanisms have been proposed, without reaching consensus on which is the predominant one. To improve our knowledge in these respects, we investigate a long-duration active region throughout its life, from birth until decay along five solar rotations, in connection with its production of ejective events. We benefit from the wealth of solar remote-sensing data with improved temporal, spatial, and spectral resolution provided by the ground-breaking space missions STEREO, SDO, and SOHO. During the investigated time interval, which covers the months July – November 2010, the STEREO spacecraft were nearly 180 degrees apart, allowing for the uninterrupted tracking of the active region and its ensuing CMEs. The ejective aspect is examined from multi-viewpoint coronagraphic images, while the dynamics of the active region photospheric magnetic field are inspected by means of SDO/HMI data for specific subintervals of interest. The ultimate goal of this work in progress is to identify common patterns in the ejective aspect that can be connected with the active region characteristics.

scholarly journals Ontogeny of the star compass in birds: pied flycatchers (Ficedula hypoleuca) can establish the star compass in spring

2021 ◽  
Vol 224 (3) ◽  
pp. jeb237875
Author(s):  
Anna Zolotareva ◽  
Gleb Utvenko ◽  
Nadezhda Romanova ◽  
Alexander Pakhomov ◽  
Nikita Chernetsov
Keyword(s):  
Magnetic Field ◽  
Small Sample Size ◽  
Polarized Light ◽  
Ficedula Hypoleuca ◽  
Small Sample ◽  
Autumn Migration ◽  
The Sun ◽  
Vertical Magnetic Field ◽  
Sun Compass ◽  
Star Compass

ABSTRACTThe star compass of birds, like the sun compass, is not innate. To possess either of them, birds have to observe the rotating sky and determine its centre of rotation (in the case of the star compass) or the sun's movement (for the sun compass). Young birds are believed to learn how to use the star compass before their first migration, even though the evidence of this is lacking. Here, we tested whether hand-raised Pied flycatchers (Ficedula hypoleuca) that had not established the star compass prior to their first autumn migration can gain it later in their ontogeny, in spring. We also attempted to examine whether the observation of diurnal celestial cues (the sun and polarized light) prior to autumn migration would affect the process of star compass learning in spring. When tested in the vertical magnetic field under the natural starry sky, the group of birds that observed the stars in spring as the first celestial cues were able to choose the migratory direction. In contrast, the birds that had never seen the stars were not able to use the nightly celestial cues in the vertical magnetic field. However, birds that had seen the daytime celestial cues till autumn and the stars at spring were disoriented, although this might be due to the small sample size. Our data suggest the possibility that the star compass may be learned in spring and emphasize the necessity for further research into the interaction of celestial compasses.

scholarly journals Inclusion of velocity gradients in the Unno solution for magnetic field diagnostic from spectropolarimetric data

2010 ◽  
Vol 6 (S274) ◽  
pp. 291-294
Author(s):  
Guillaume Molodij ◽  
Véronique Bommier
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Vertical Velocity ◽  
Velocity Gradient ◽  
Coming Out ◽  
The Sun ◽  
Velocity Gradients ◽  
Vertical Velocity Gradient

AbstractWe present an extension of the Unno-Rachkovsky solution that provides the theoretical profiles coming out of a Milne-Eddington atmosphere imbedded in a magnetic field, to the additional taking into account of a vertical velocity gradient. Thus, the theoretical profiles may display asymmetries as do the observed profiles, which facilitates the inversion based on the Unno-Rachkovsky theory, and leads to the additional determination of the vertical velocity gradient. We present UNNOFIT inversion on spectropolarimetric data performed on an active region of the Sun with the french-italian telescope THEMIS operated by CNRS and CNR on the island of Tenerife.

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