scholarly journals Solar Flare Surges in relation to Active Prominences and Sunspots

1994 ◽  
Vol 47 (6) ◽  
pp. 817
Author(s):  
TK Das ◽  
TN Chatterjee ◽  
AK Sen
Keyword(s):  
Active Region ◽  
Solar Flare ◽  
Sunspot Group ◽  
Active Regions ◽  
X Ray

A study has been made of flare surges (FS) after correlating them with prominences and sunspots. Results obtained are: (i) the duration of the 88% events lies between 0-40 min; (ii) in most cases the distance between FS and filaments ranges from 0�03 R0 to 0�12R0 whereas' that between FS and sunspots ranges from 0�05R0 to 0�25R0; (iii) there are several active regions which can produce sympathetic FS; and (iv) the number of FS from a particular sunspot group is proportional to the number of X-ray flares from the same active region.

scholarly journals Chronology of Formation of Solar Radio Burst Types III and V Associated with Solar Flare Phenomenon on 19th September 2011

2013 ◽  
Vol 24 ◽  
pp. 32-42
Author(s):  
Zety Sharizat Hamidi ◽  
N.N.M. Shariff
Keyword(s):  
Active Region ◽  
Solar Flare ◽  
Solar Radio ◽  
Active Regions ◽  
Radio Flux ◽  
X Ray ◽  
Type Iii ◽  
Solar Bursts ◽  
Type V

The formation of two different solar bursts, type III and V in one solar flare event is presented. Both bursts are found on 19th September 2011 associated with C-class flares on active region 1295. From the observation, we believed that the mechanism of evolution the bursts play an important role in the event. It is found that type V burst appeared in five minutes after type III. There are a few active regions on the solar disk but most are magnetically simple and have remained rather quiet. An interpretation of this new result depends critically on the number of sunspots and the role of active region 1295. Sunspot number is increased up to 144 with seven sunspots can be observed. During that event, the speed of solar wind exceeds 433.8 km/second with 2.0 g/cm3 density of protons in the solar corona. Currently, radio flux is also high up to 150 SFU. The solar flare type C6 is continuously being observed in the X-ray region for 24 hours since 1541 UT and a maximum C1 is detected on 1847 UT. Although the sources of both bursts are same, the direction and ejection explode differently. It is believed that the ejection of particles in a type III burst is higher than solar burst type V.

scholarly journals Statistical Properties of Magnetic Separators in Model Active Regions

2000 ◽  
Vol 195 ◽  
pp. 443-444
Author(s):  
B. T. Welsch ◽  
D. W. Longcope
Keyword(s):  
Active Region ◽  
Solar Corona ◽  
Magnetic Reconnection ◽  
First Principles ◽  
Magnetic Charge ◽  
Active Regions ◽  
Heating Rates ◽  
X Ray ◽  
Field Lines ◽  
Charge Topology

“Transient brightenings” (or “microflares”) regularly deposit 1027 ergs of energy in the solar corona, and account for perhaps 20% of the active corona's power (Shimizu 1995). We assume these events correspond to episodes of magnetic reconnection along magnetic separators in the solar corona. Using the techniques of magnetic charge topology, we model active region fields as arising from normally distributed collections of “magnetic charges”, point-like sources/sinks of flux (or field lines). Here, we present statistically determined separator (X-ray loop) lengths, derived from first principles. We are in the process of statistical calculations of heating rates due to reconnection events along many separators.

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.

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 Recent High Resolution X-Ray Spectra of the Sun

1972 ◽  
Vol 14 ◽  
pp. 740-741
Author(s):  
J. H. Parkinson ◽  
K. Evans ◽  
K. A. Pounds
Keyword(s):  
High Resolution ◽  
Active Region ◽  
Wavelength Range ◽  
South Australia ◽  
Active Regions ◽  
Effective Area ◽  
Field Of View ◽  
The Sun ◽  
X Ray

New results are presented from high resolution Bragg crystal spectrometers flown in late 1970 on two Skylark rockets. The first instrument, launched on 24 November 1970 at 22 13 UT from Woomera, South Australia, contained two crystal spectrometers, each with an effective area of 50 cm2 and field collimation to 3’ FWHM. This instrument obtained the X-ray spectrum of the quiet corona in the wavelength range 5–14 Å. The second instrument was launched on 6 December 1970 at 11 13 UT from Sardinia, Italy, and contained four crystals of 6 cm2, each collimated to 4’ FWHM. This instrument was pointed at a non-flaring active region near N20 W40(McMath region 11060), and obtained an X-ray spectrum between 5 and 23 Å. This first use of a collimator to limit the field of view has considerably increased the spectral clarity compared with earlier observations by excluding the contributions of other active regions.

scholarly journals X-Ray Structures Associated with Disappearing Hα Filaments in Active Regions

1980 ◽  
Vol 91 ◽  
pp. 61-65
Author(s):  
S. W. Kahler
Keyword(s):  
Active Region ◽  
Large Scale ◽  
Active Regions ◽  
Statistical Correlation ◽  
Coronal Emission ◽  
X Ray ◽  
Temporal Relationships ◽  
Using Data ◽  
Scale Length ◽  
Shape And Size

Several studies using data from Skylab instruments have been carried out to determine the spatial and temporal relationships between disappearing Hα filaments and the associated coronal emission features. Webb et al. (1976) studied 30 transient coronal X-ray enhancements which could be associated with the disappearances of Hα filaments outside active regions. They found that in the early phase of the transient X-ray brightening, emitting structures appeared at or near the filament location with shape and size resembling the filament. Sheeley et al. (1975) examined a long-lived X-ray enhancement of expanding loops associated with an active region filament which disappeared. Rust and Webb (1977) found a good statistical correlation in time and position between large scale (length > 60, 000 km) active region X-ray enhancements and Hα filament activity, in particular, events of an eruptive nature.

scholarly journals The Tendencies and Timeline of the Solar Burst Type II Fragmented

2014 ◽  
Vol 31 ◽  
pp. 84-102 ◽  
Author(s):  
Zety Sharizat Hamidi ◽  
N.N.M. Shariff ◽  
C. Monstein
Keyword(s):  
Active Region ◽  
Solar Flare ◽  
Radio Burst ◽  
Solar Radio ◽  
Active Regions ◽  
Solar Radio Burst ◽  
Beta Radiation ◽  
X Rays ◽  
Type Ii ◽  
Harmonic Structure

We report the timeline of the solar radio burst Type II that formed but fragmented at certain point based on the eruption of the solar flare on 13th November 2012 at 2:04:20 UT. The active region AR 1613 is one of the most active region in 2012. It is well known that the magnetic energy in the solar corona is explosively released before converted into the thermal and kinetic energy in solar flares. In this work, the Compound Astronomical Low-frequency, Low-cost Instrument for Spectroscopy Transportable Observatories (CALLIISTO) system is used in obtaining a dynamic spectrum of solar radio burst data. There are eight active regions and this is the indicator that the Sun is currently active. Most the active regions radiate a Beta radiation. The active regions 1610, 1611 and 1614 are currently the largest sunspots on the visible solar disk. There is an increasing chance for an isolated M-Class solar flare event. It is also expected that there will be a chance of an M flare, especially from AR 1614 and 1610. Although these two observations (radio and X-rays) seem to be dominant on the observational analysis, we could not directly confirmed that this is the only possibility, and we need to consider other processes to explain in detailed the injection, energy loss and the mechanism of the acceleration of the particles. In conclusion, the percentage of energy of solar flare becomes more dominant rather than the acceleration of particles through the Coronal Mass Ejections (CMEs) and that will be the main reason why does the harmonic structure of type II burst is not formed. This event is one fine example of tendencies solar radio burst type III, which makes the harmonic structure of solar radio burst type II fragmented.

scholarly journals Time Variations in Coronal Active Regions

1975 ◽  
Vol 68 ◽  
pp. 103-103
Author(s):  
A. S. Krieger ◽  
R. C. Chase ◽  
M. Gerassimenko ◽  
S. W. Kahler ◽  
A. F. Timothy ◽  
...  
Keyword(s):  
Active Region ◽  
Potential Field ◽  
Active Regions ◽  
Field Approximation ◽  
X Ray ◽  
Evolutionary Changes ◽  
Potential Component ◽  
Time Variations ◽  
Field Lines

SummaryThe AS&E X-ray telescope experiment on Skylab has obtained images of the solar X-ray corona with a variety of time resolutions ranging from 21/2 s to the regular 12 ± 2 h synoptic observation rate. The form and brightness of coronal active region structures are seen to vary on time scales ranging from seconds, for flare associated changes, to several solar rotations for long term evolution of the regions. The extrapolation of photospheric magnetic fields into the corona, using the potential field approximation, results in a good morphological agreement between the form of the computed coronal field lines and the structure of many of the active regions observed. Thus, in general, the coronal active region structures follow potential field lines and the long term evolutionary changes can be explained on the basis of the spreading of the fields. Short term changes in active region structure frequently take the form of selective brightening or dimming of pre-existing loops due to changes in the pressure of the emitting coronal plasma. In these cases, variations in the non-potential component of the coronal fields supporting and containing the plasma are implied.

scholarly journals Signatures of the non-Maxwellian κ-distributions in optically thin line spectra

2019 ◽  
Vol 626 ◽  
pp. A88 ◽  
Author(s):  
Jaroslav Dudík ◽  
Elena Dzifčáková ◽  
Giulio Del Zanna ◽  
Helen E. Mason ◽  
Leon L. Golub ◽  
...  
Keyword(s):  
Active Region ◽  
Active Regions ◽  
Grazing Incidence ◽  
High Energy ◽  
Maxwellian Distribution ◽  
Ionization Equilibrium ◽  
X Ray ◽  
High Energy Tail ◽  
Intensity Ratios ◽  
Collisional Ionization

Aims. We investigated the possibility of diagnosing the degree of departure from the Maxwellian distribution using the Fe XVII–Fe XVIII spectra originating in plasmas in collisional ionization equilibrium, such as in the cores of solar active regions or microflares. Methods. The original collision strengths for excitation are integrated over the non-Maxwellian electron κ-distributions characterized by a high-energy tail. Synthetic X-ray emission line spectra were calculated for a range of temperatures and κ. We focus on the 6–24 Å spectral range to be observed by the upcoming Marshall Grazing-Incidence X-ray Spectrometer MaGIXS. Results. We find that many line intensity ratios are sensitive to both T and κ. Best diagnostic options are provided if a ratio involving both Fe XVII and Fe XVIII is combined with another ratio involving lines formed within a single ion. The sensitivity of such diagnostics to κ is typically a few tens of per cent. Much larger sensitivity, of about a factor of two to three, can be obtained if the Fe XVIII 93.93 Å line observed by SDO/AIA is used in conjuction with the X-ray lines. Conclusions. We conclude that the MaGIXS instrument is well-suited for detection of departures from the Maxwellian distribution, especially in active region cores.

scholarly journals The Structure of Solar Active Regions from EUV and Soft X-Ray Observations

1975 ◽  
Vol 68 ◽  
pp. 109-131 ◽  
Author(s):  
Carole Jordan
Keyword(s):  
Spatial Distribution ◽  
Active Region ◽  
Emission Measure ◽  
Active Regions ◽  
Flux Tubes ◽  
X Ray ◽  
Solar Active Regions

The structure of solar active regions derived from EUV and soft X-ray observations is reviewed. The methods by which the emission measure as a function of temperature can be interpreted are discussed. The models of density and temperature which can be made from a variety of combinations of the emission measure with information on the spatial distribution of material, are broadly consistent. They show that the plasma at low heights over the central parts of an active region is hotter and denser than that which extends to greater heights. It appears that much of the emitting material exists in the form of loop structures, presumably magnetically controlled flux tubes. Analytical relationships between the physically important parameters describing the properties of the active region at Te > 2 × 105 K are developed and discussed.

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