scholarly journals The Nonpotentiality of Active‐Region Coronae and the Dynamics of the Photospheric Magnetic Field

2005 ◽  
Vol 628 (1) ◽  
pp. 501-513 ◽  
Author(s):  
Carolus J. Schrijver ◽  
Marc L. DeRosa ◽  
Alan M. Title ◽  
Thomas R. Metcalf
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Photospheric Magnetic Field

scholarly journals The Formation of a Moat Around a Sunspot as Observed on Longitudinal–Field Magnetograms (?)

1993 ◽  
Vol 141 ◽  
pp. 75-77
Author(s):  
L.V. Ermakova
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Spatial Resolution ◽  
Sunspot Group ◽  
Longitudinal Magnetic Field ◽  
Photospheric Magnetic Field ◽  
Longitudinal Field ◽  
Maximum Area ◽  
Spot Group

In this paper the dynamics of the photospheric magnetic field near the sunspot of the active region McMath 15508 is considered on the basis of longitudinal magnetic field B11 magnetograms. The magnetograms were obtained at the panoramic magnetograph of the Sayan Observatory. The time taken to obtain one magnetogram was 5 min. The spatial resolution was 1.8“ × 3.6“. In the active region McMath 15508 a new bipolar spot group formed westward of the existing sunspot group on September 1; the next day the main sunspots had penumbras, and on September 3 the new sunspot group reached a maximum area and began decaying thereafter.

scholarly journals Large-scale photospheric magnetic field: The diffusion of active region fields

Solar Physics ◽  
1972 ◽  
Vol 26 (2) ◽  
pp. 283-289 ◽  
Author(s):  
Kenneth H. Schatten ◽  
Robert B. Leighton ◽  
Robert Howard ◽  
John M. Wilcox
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Large Scale ◽  
Photospheric Magnetic Field

scholarly journals ASYMMETRY IN APPEARANCE OF THE LEADING AND FOLLOWING POLARITIES IN THE PHOTOSPHERIC MAGNETIC FIELD AT THE EARLY STAGE OF ACTIVE REGION FORMATION

2020 ◽  
Vol 6 (4) ◽  
pp. 3-9
Author(s):  
Victor Grigoryev ◽  
Lyudmila Ermakova ◽  
Anna Khlystova
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Visual Inspection ◽  
Early Stage ◽  
Active Regions ◽  
Longitudinal Component ◽  
Photospheric Magnetic Field ◽  
Line Of Sight ◽  
Flux Dynamics ◽  
The Magnetic Field

We study the evolution of the photospheric magnetic field at the early stage of active region development. We use data on longitudinal component of the magnetic field and line-of-sight velocities from SOHO/MDI and SDO/HMI. The visual inspection of 48 cases of birth of active regions and the detailed analysis of the magnetic flux dynamics in 4 active regions have shown that at the time of emergence of a new magnetic field, the field of the following polarity is the first to be detected in the photosphere. The flux asymmetry of the leading and following polarities persists for several tens of minutes. The observed asymmetry of magnetic fluxes supports the results of the numerical simulation of emergence of the active region magnetic field in the upper layers of the convective zone, which has been carried out by Rempel and Cheung [2014].

scholarly journals Preprocessing of vector magnetograms for magnetohydrostatic extrapolations

2020 ◽  
Vol 644 ◽  
pp. A57
Author(s):  
X. Zhu ◽  
T. Wiegelmann ◽  
B. Inhester
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Magnetic Energy ◽  
Free Field ◽  
Original Data ◽  
Optimization Method ◽  
Boundary Integral ◽  
Photospheric Magnetic Field ◽  
Surface Integral ◽  
Force Free Field

Context. Understanding the 3D magnetic field as well as the plasma in the chromosphere and transition region is important. One way is to extrapolate the magnetic field and plasma from the routinely measured vector magnetogram on the photosphere based on the assumption of the magnetohydrostatic (MHS) state. However, photospheric data may be inconsistent with the MHS assumption. Therefore, we must study the restriction on the photospheric magnetic field, which is required by the MHS system. Moreover, the data should be transformed accordingly before MHS extrapolations can be applied. Aims. We aim to obtain a set of surface integrals as criteria for the MHS system and use this set of integrals to preprocess a vector magnetogram. Methods. By applying Gauss’ theorem and assuming an isolated active region on the Sun, we related the magnetic energy and forces in the volume to the surface integral on the photosphere. The same method was applied to obtain restrictions on the photospheric magnetic field as necessary criteria for a MHS system. We used an optimization method to preprocess the data to minimize the deviation from the criteria as well as the measured value. Results. By applying the virial theorem to the active region, we find the boundary integral that is used to compute the energy of a force-free field usually underestimates the magnetic energy of a large active region. We also find that the MHS assumption only requires the x-, y-component of net Lorentz force and the z-component of net torque to be zero. These zero components are part of Aly’s criteria for a force-free field. However, other components of net force and torque can be non-zero values. According to new criteria, we preprocess the magnetogram to make it more consistent with the MHS system and, at the same time close, to the original data.

scholarly journals ASYMMETRY IN APPEARANCE OF THE LEADING AND FOLLOWING POLARITIES IN THE PHOTOSPHERIC MAGNETIC FIELD AT THE EARLY STAGE OF ACTIVE REGION FORMATION

2020 ◽  
Vol 6 (4) ◽  
pp. 3-9
Author(s):  
Victor Grigoryev ◽  
Lyudmila Ermakova ◽  
Anna Khlystova
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Visual Inspection ◽  
Early Stage ◽  
Active Regions ◽  
Longitudinal Component ◽  
Photospheric Magnetic Field ◽  
Line Of Sight ◽  
Flux Dynamics ◽  
The Magnetic Field

We study the evolution of the photospheric magnetic field at the early stage of active region development. We use data on longitudinal component of the magnetic field and line-of-sight velocities from SOHO/MDI and SDO/HMI. The visual inspection of 48 cases of birth of active regions and the detailed analysis of the magnetic flux dynamics in 4 active regions have shown that at the time of emergence of a new magnetic field, the field of the following polarity is the first to be detected in the photosphere. The flux asymmetry of the leading and following polarities persists for several tens of minutes. The observed asymmetry of magnetic fluxes supports the results of the numerical simulation of emergence of the active region magnetic field in the upper layers of the convective zone, which has been carried out by Rempel and Cheung [2014].

scholarly journals Photospheric magnetic field properties of active region 12740

2020 ◽  
Vol 1523 ◽  
pp. 012014
Author(s):  
M Z Nurzaman ◽  
S Sulistiani ◽  
V Volvacea
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Photospheric Magnetic Field

scholarly journals Case Studies of Photospheric Magnetic Field Properties of Active Regions Associated with X-class Solar Flares

2021 ◽  
Vol 50 (1) ◽  
pp. 253-260
Author(s):  
Wai-Leong Teh ◽  
Farahana Kamarudin
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Temporal Variation ◽  
Solar Flares ◽  
Magnetic Parameter ◽  
Onset Time ◽  
Active Regions ◽  
Space Mission ◽  
Photospheric Magnetic Field ◽  
Magnetic Parameters

Solar flares are a transient phenomenon occurred in the active region (AR) on the Sun’s surface, producing intense emissions in EUV and soft X-ray that can wreak havoc in the near-Earth space mission and satellite as well as radio-based communication and navigation. The ARs are accompanied with strong magnetic fields and manifested as dark spots on the photosphere. To understand the photospheric magnetic field properties of the ARs that produce intense flares, two ARs associated with X-class flares, namely AR 12192 and AR 12297, occurred respectively on 25 October 2014 and 11 March 2015, are studied in terms of magnetic classification and various physical magnetic parameters. Solar images from the Langkawi National Observatory (LNO) and physical magnetic parameters from the Space-weather HMI Active Region Patches (SHARP) are used in this study. A total of seven SHARP magnetic parameters are examined which are calculated as sums of various magnetic quantities and have been identified as useful predictors for flare forecast. These two ARs are classified as βγδ sunspots whereas their formation and size are quite different from each other. Our results showed that the intensity of a flare has little relationship with the area of an AR and the magnetic free energy; and the temporal variation of individual magnetic parameter has no obvious and consistent pre-flare feature. It is concluded that the temporal variation of individual magnetic parameter may not be useful for predicting the onset time of a flare.

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