Energy Balance and Structure Of Active Regions

1977 ◽  
Vol 36 ◽  
pp. 457-473 ◽  
Author(s):  
Frank Q. Orrall ◽  
Roger A. Kopp
Keyword(s):  
Solar Activity ◽  
Energy Balance ◽  
Active Region ◽  
Internal Structure ◽  
Solar Flares ◽  
Active Regions ◽  
Particle Emission ◽  
Space Astronomy ◽  
Coronal Bright Points ◽  
Definition Of

With the advent of radio and space astronomy it became necessary to extend the definition of a center of activity or active region (AR) originally proposed by L. d’Azambuja. At IAU Symposium 35, K.O. Klepenheuer (1968) defined an AR as “The totality of all observable phenomena preceding, accompanying and following the birth of sunspots, including radio-, X-, EUV-, and particle emission.” The recognition that there are other short-lived bipolar features with a distribution similar to that of active regions (ephemeral active regions) by Harveyet al. (1975) and their identification with coronal bright points by Golub et al. (1975) suggests that the definition will have to be extended further. Active regions manifest themselves in the photosphere as sunspots and faculae; in the chromosphere as the plage and its structures; in the corona as a coronal enhancement with a complex, often loop-like internal structure. (The termenhancementwas Introduced by Billings. The original termpermanent coronal condensation, introduced by Waldemeler, only referred to the very bright enhancements and was, moreover, often confused with hissporadic coronal condensations, a flareassodated phenomena. The termcoronal active regionhas, recently also been used for the coronal extension of the AR.) In keeping with the aims of this symposium the stress of this review will be on the chromosphere and corona. Active regions are especially Important as the site of most flare-associated phenomena. Here we shall be concerned with flares only as they affect the overall energy balance. Our concern is with the “quiet” active regions that cause the slowly varying components of solar activity and provide the ambiance within which solar flares occur.

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.

scholarly journals Modelling of Solar Coronal Loops

1992 ◽  
Vol 9 ◽  
pp. 661-662
Author(s):  
C. Jordan
Keyword(s):  
Energy Balance ◽  
Active Region ◽  
Active Regions ◽  
Coronal Loops ◽  
Loop Structure ◽  
X Rays ◽  
Spectroscopic Observations ◽  
Available Information ◽  
Solar Coronal

Modelling of coronal active regions in terms of loop structures began around 1974 (see Jordan 1975) and was stimulated by images of the corona in X-rays and the uv, obtained from rocket flights. Vaiana was a pioneer in this field (see Vaiana et al. 1973). The Skylab missions provided a fuller range of imaging and spectroscopic observations, and much of the available information is still based on these data (see Orrall 1981). Since 1975 a very large number of papers have been published on the various aspects of loop structure, heating and stability (see review by Mewe 1991). Here I can mention only a few points concerning the relation between observable parameters and the energy balance and heating requirements of active region loops.

scholarly journals Dynamic Events in the X-Ray Corona (A Progress Report from the AS&E X-ray Telescope on Skylab)

1974 ◽  
Vol 57 ◽  
pp. 501-504 ◽  
Author(s):  
G. S. Vaiana ◽  
A. S. Krieger ◽  
J. K. Silk ◽  
A. F. Timothy ◽  
R. C. Chase ◽  
...  
Keyword(s):  
Active Region ◽  
Large Scale ◽  
Active Regions ◽  
Loop Structure ◽  
X Ray ◽  
Dynamic Events ◽  
Coronal Bright Points ◽  
Coronal Activity ◽  
East Limb ◽  
Coronal Structures

Data obtained by the AS&E X-ray Telescope Experiment during the first Skylab mission have revealed a variety of temporal changes in both the form and brightness of coronal structures. Dynamical changes have been noted in active regions, in large scale coronal structures, and in coronal bright points. The coronal activity accompanying a series of Hα flares and prominence activity between 0800 and 1600 UT on 10 June 1973 in active region 137 (NOAA) at the east limb is shown in Figure 1. It is characterized by increases in the brightness and temperature of active region loops and a dramatic change in the shape and brightness of a loop structure. Figure 2 shows the reconfiguration of an apparent polar crown filament cavity between 1923 UT on 12 June 1973 and 1537 UT on 13 June 1973. A ridge of emitting material which attains a peak brightness at least four times that of the surrounding coronal structures appears within the cavity during the course of the event. Typical X-ray photographs with filters passing relatively soft X-ray wavelengths (3–32, 44–54 Å) show 90 to 100 X-ray bright points (Vaiana et al., 1973). On twelve occasions in the data from the first mission, such bright points were seen to increase in intensity by two orders of magnitude in less than 4 min. Such an event is shown in Figure 3.

scholarly journals The Evolution of Unstable 'Beta-Gamma' Magnetic Fields of Active Region AR 2222

2015 ◽  
Vol 48 ◽  
pp. 95-102
Author(s):  
Zety Sharizat Hamidi ◽  
S.N.U. Sabri ◽  
N.N.M. Shariff ◽  
C. Monstein
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Solar Flares ◽  
Active Regions ◽  
Group Type ◽  
Solar Burst ◽  
Type Iv ◽  
Fine Structures ◽  
Using Data

This event allows us to investigate how plasma–magnetic field interactions in the solar corona can produce suprathermal electron populations over periods from tens of minutes to several hours, and the interactions of wave-particle and wave-wave lead to characteristic fine structures of the emission. An intense and broad solar radio burst type IV was recorded by CALLISTO spectrometer from 240-360 MHz. Using data from a the KRIM observatory, we aim to provide a comprehensive description of the synopsis formation and dynamics of a a single solar burst type IV event due to active region AR2222. For five minutes, the event exhibited strong pulsations on various time scales and “broad patterns” with a formation of a group type III solar burst. AR 2222 remained the most active region, producing a number of minor C-Class solar flares. The speed of the solar wind also exceeds 370.8 km/second with 10.2 g/cm3 density of proton in the solar corona. The radio flux also shows 171 SFU. Besides, there are 3 active regions, AR2217, AR2219 and AR2222 potentially pose a threat for M-class solar flares. Active region AR2222 have unstable 'beta-gamma' magnetic fields that harbor energy for M-class flares. As a conclusion, we believed that Sun’s activities more active in order to achieve solar maximum cycle at the end of 2014.

scholarly journals Searching for failed eruptions interacting with overlying magnetic field

2015 ◽  
Vol 11 (S320) ◽  
pp. 221-223 ◽  
Author(s):  
Dominik Gronkiewicz ◽  
Tomasz Mrozek ◽  
Sylwester Kołomański ◽  
Martyna Chruślińska
Keyword(s):  
Magnetic Field ◽  
Statistical Analysis ◽  
Active Region ◽  
Solar Flares ◽  
Active Regions ◽  
Automated Method ◽  
Solar Eruptions ◽  
Mass Ejection ◽  
The Magnetic Field ◽  
Flare Site

AbstractIt is well known that not all solar flares are connected with eruptions followed by coronal mass ejection (CME). Even strongest X-class flares may not be accompanied by eruptions or are accompanied by failed eruptions. One of important factor that prevent eruption from developing into CME is strength of the magnetic field overlying flare site. Few observations show that active regions with specific magnetic configuration may produce many CME-less solar flares. Therefore, forecasts of geoeffective events based on active region properties have to take into account probability of confining solar eruptions. Present observations of SDO/AIA give a chance for deep statistical analysis of properties of an active region which may lead to confining an eruption. We developed automated method which can recognize eruptions in AIA images. With this tool we will be able to analyze statistical properties of failed eruptions observed by AIA telescope.

scholarly journals Physical Features in the AR5395

1993 ◽  
Vol 141 ◽  
pp. 84-87
Author(s):  
Heng Zhang ◽  
Yongjin Kong ◽  
Di Luan ◽  
Ying Cao
Keyword(s):  
Active Region ◽  
High Activity ◽  
Solar Flares ◽  
Active Regions ◽  
Velocity Fields ◽  
Dynamical Characteristics ◽  
Physical Features ◽  
The Relationship

AbstractThe active region Boulder # 5395 (N34, L257), which appeared on the disk in March 1989, is one of the biggest active regions in fifty years. Study on the structure and dynamical characteristics of the region can help to understand the physics of solar flares. Many authors have studied morphology and sunspot motion of the region (e.g. Wang et al. 1991, and Zhao 1990); the magnetic emergence and shear; the relationship between the extrusion and the flares and the characteristics of the magnetic and velocity fields in the flare sites (Chen 1990; Li et al. 1990; Zhang et al. 1990). It comes into question that most of the regions display the features mentioned above but only a few of them produce such a high activity as AR5395 does. In other word, AR5395 must possess some particular features that are probably related to its high activity. Our attempt is to find what the special features are.

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 Origine des régions actives solaires ‘anormales’

1968 ◽  
Vol 35 ◽  
pp. 25-32 ◽  
Author(s):  
M. J. Martres
Keyword(s):  
Solar Activity ◽  
Active Region ◽  
Active Center ◽  
Active Regions ◽  
The West ◽  
Magnetic Inversion ◽  
Solar Active Regions ◽  
Western Side ◽  
Magnetic Inversion Line

Solar active regions are considered ‘anomalous’ when they belong to magnetic classes γ,βγ and βf-αf. The study of the solar activity of the region where, later on, these groups are born shows an evident correlation between the presence of an old active center and the complexity of the new active region.It is found that the complexity is greater if the old active center is younger, and the superposition better. We also observe that the birth of anomalous sunspots groups occurs much more frequently on the western side of the magnetic inversion line of the old center.When the birth of an active center occurs outside and on the West of the faculae, we observe the weakly anomalous groups βf-αf. The ‘perturbation’ decreases with distance and is extended at least to 10 heliographic degrees of the boundaries of the old faculae.

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.

scholarly journals Variations of the total electronic concentration in the ionosphere in seismically active region

2021 ◽  
Vol 333 ◽  
pp. 02012
Author(s):  
Valentin Kashkin ◽  
Tatyana Rubleva ◽  
Konstantin Simonov ◽  
Andrey Zabrodin ◽  
Aleksey Kabanov
Keyword(s):  
Solar Activity ◽  
Active Region ◽  
Electron Concentration ◽  
Navigation System ◽  
Active Regions ◽  
Computational Technique ◽  
Total Electron ◽  
Catastrophic Earthquake ◽  
Electronic Concentration ◽  
Geodynamic Activity

In this work we studied the variations in the total electron concentration (TEC) obtained from measurements of the global navigation system GPS in the preparation zone for the 2010 catastrophic Chilean earthquake (Mw = 8.8) under calm background conditions at a minimum of 24 solar activity (SA) cycles. The analysis of the geodynamic activity and ionospheric TEC disturbances in the seismically active region of this catastrophic earthquake is carried out. A computational technique has been developed that can be used to study TEC variations over seismically active regions.

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