Evolution of the magnetic fields of solar flare active regions from the geometry and topology of HMI/SDO magnetograms

2014 ◽  
Vol 58 (3) ◽  
pp. 145-155 ◽  
Author(s):  
I. S. Knyazeva ◽  
N. G. Makarenko
Keyword(s):  
Magnetic Fields ◽  
Solar Flare ◽  
Active Regions ◽  
And Topology

Connection between Active region complexity and Solar Flare strength

2018 ◽  
Vol 13 (S340) ◽  
pp. 75-76
Author(s):  
K. Amareswari ◽  
Sreejith Padinhatteeri ◽  
K. Sankarasubramanian
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Solar Flare ◽  
Solar Flares ◽  
Active Regions ◽  
Magnetic Topology ◽  
Automated Algorithm ◽  
Almost All ◽  
Full Disk

AbstractHale (1908) discovered the existence of magnetic fields in sunspots, and since then a consensus has been reached that magnetic fields play an important role in various forms of solar activities, such as solar flares . Modified Mount-Wilson scheme is one of the methodology to classify active regions based on their complexity . As per this scheme, sunspots are classified as α, β, γ, and δ with the complexity of the magnetic topology increasing from α to δ. The δ sunspots are known to be highly flare-productive. An existing automated algorithm (SMART-DF) is modified and used to identify δ-spots for the existing full disk SOHO/MDI data. The automatically identified δ-spots is compared with the NOAA-SRS database and found to be reproducing almost all the identified δ-spots. In thisstudy, the connection between formation of δ-spot and flares is also carried out using GOES flare flux and NOAA-SRS sunspot classification.

scholarly journals Helicity Generation and Signature in Solar Atmosphere

2005 ◽  
Vol 13 ◽  
pp. 89-93 ◽  
Author(s):  
A. A. Pevtsov
Keyword(s):  
Fine Structure ◽  
Magnetic Fields ◽  
Solar Atmosphere ◽  
Active Regions ◽  
Turbulent Convection ◽  
Coronal Loops ◽  
The Sun ◽  
Solar Magnetic Fields ◽  
And Topology ◽  
Current Helicity

AbstractTo fully understand the origin, evolution and topology of solar magnetic fields, one should comprehend their magnetic helicity. Observationally, non-zero helicity reveals itself in the patterns of electric currents inside active regions, superpenumbral sunspot whirls, the shape of coronal loops and the fine structure of chromospheric filaments. Some patterns may bear information about deep sub-photospheric processes (e.g., dynamo, turbulent convection). Others may originate at or near the photosphere. This presentation reviews the observations of magnetic and current helicity on the Sun, discusses the possible mechanisms of helicity generation, and compares them with the observations.

scholarly journals Spectral investigations of magnetic fields and thermodynamic conditions in active regions on the Sun

2019 ◽  
pp. 15-22
Author(s):  
V. Lozitsky
Keyword(s):  
Magnetic Fields ◽  
Solar Flare ◽  
Magnetic Flux ◽  
Active Regions ◽  
Doppler Velocity ◽  
The Sun ◽  
Strong Magnetic Fields ◽  
Flux Tubes ◽  
Thermodynamic Conditions ◽  
Mixed Polarity

The main results of studies of magnetic fields and thermodynamic conditions in active regions in the Sun obtained at the Astronomical Observatory of the Taras Shevchenko National University of Kyiv (AO KNU) during the last 10 years (2010–2019) are presented. The true diameter of the extremely small(spatially unresolved) magnetic flux tubes was estimated on a base of data from Hinode Space Observatory; this diameter was found to be within the range of 15–20 km, which is much smaller than the spatial resolution limit of the largest solar telescopes to date (≈ 60 km). According to the observations made at AO KNU, it was shown that there are three types of magnetic fields in a solar faculae: strong (kilogauss range) fields in small-scale flux tubes, areas of weak and moderate background fields of regular polarity, and areas of sub-telescopic fields of mixed polarity. The magnetic flux of mixed polarity exceeds the absolute flux of the entire field of regular polarity by at least 2 times. In the sunspot umbra observed at GST of AO KNU and ATsU-5 of GAO NASU, thin spectral effects of Zeeman splitting were found, which indicate presence of very strong magnetic fields at least of 5,8 kG. The polarity of the magnetic field in sub-telescopic structures with such very strong fields is found to be the same as in the background field, and the Doppler velocity is about 2 km/s (plasma lifting). Super- strong magnetic fields in the range of 5–5,7 kG were also detected from observations of the Big Bear Observatory (BBSO), USA. A unique observational material also obtained on AO KNU concerning the area of a seismic source of extremely powerful solar flare on October 28, 2003 of X17.2 / 4B class was analyzed. This solar flare had a Balmer decrement with a record intensity ratio I (Hβ) / I (Hα) = 1,68 of the Hβ and Hα lines, which is unprecedented for all flares observed. In this flare, indications of the existence of particularly strong magnetic fields in the range of several tens of kilogauss were found. The semi-empirical model of this flare has an interesting feature, namely three discrete layers with high plasma concentration and temperature, including a very thick and thin layer in the chromosphere with the following parameters: hydrogen concentration nH = 1018 cm–3, thickness Δh = 3–5 km and height h ≈ 1200 km above the level of the photosphere. In active solar prominences, rather strong magnetic fields (up to 4 kG) were detected at altitudes of 3–14 Mm. The modeling of spectral line profiles within the two-component model showed that the true magnitude of local magnetic fields can be even greater by at least 3 times. A theoretical MHD model is proposed, according to which such high strengths occur in force-free magnetic ropes with a characteristic scale of 300 km.

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

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.

Influence of Magnetic Fields on Solar Hydrodynamics: Experimental Results

1977 ◽  
Vol 36 ◽  
pp. 143-180 ◽  
Author(s):  
J.O. Stenflo
Keyword(s):  
Solar Activity ◽  
Energy Balance ◽  
Magnetic Fields ◽  
Solar Atmosphere ◽  
General Problem ◽  
Solar Rotation ◽  
Active Regions ◽  
Physical Conditions ◽  
Dynamic Phenomena

It is well-known that solar activity is basically caused by the Interaction of magnetic fields with convection and solar rotation, resulting in a great variety of dynamic phenomena, like flares, surges, sunspots, prominences, etc. Many conferences have been devoted to solar activity, including the role of magnetic fields. Similar attention has not been paid to the role of magnetic fields for the overall dynamics and energy balance of the solar atmosphere, related to the general problem of chromospheric and coronal heating. To penetrate this problem we have to focus our attention more on the physical conditions in the ‘quiet’ regions than on the conspicuous phenomena in active regions.

A Study of the Evolution of Solar Active Regions for Improving Solar Flare Forecasts

1989 ◽  
Author(s):  
Patricia L. Bornmann ◽  
Darren Kalmbach ◽  
David Kulhanek ◽  
April Casale
Keyword(s):  
Solar Flare ◽  
Active Regions ◽  
Solar Active Regions

scholarly journals Nonlinear force-free modeling of magnetic fields in flare-productive active regions

2015 ◽  
Vol 11 (S320) ◽  
pp. 167-174
Author(s):  
M. S. Wheatland ◽  
S. A. Gilchrist
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Boundary Data ◽  
Numerical Solutions ◽  
Free Field ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
Nonlinear Force ◽  
The Magnetic Field ◽  
Force Free Field

AbstractWe review nonlinear force-free field (NLFFF) modeling of magnetic fields in active regions. The NLFFF model (in which the electric current density is parallel to the magnetic field) is often adopted to describe the coronal magnetic field, and numerical solutions to the model are constructed based on photospheric vector magnetogram boundary data. Comparative tests of NLFFF codes on sets of boundary data have revealed significant problems, in particular associated with the inconsistency of the model and the data. Nevertheless NLFFF modeling is often applied, in particular to flare-productive active regions. We examine the results, and discuss their reliability.

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