Evidence for a Cutoff in the Frequency Distribution of Solar Flares from Small Active Regions

1997 ◽  
Vol 475 (1) ◽  
pp. 338-347 ◽  
Author(s):  
T. A. Kucera ◽  
B. R. Dennis ◽  
R. A. Schwartz ◽  
D. Shaw
Keyword(s):  
Frequency Distribution ◽  
Solar Flares ◽  
Active Regions

Peculiarities of the microwave emission from active regions generating intense solar flares

2003 ◽  
Vol 29 (4) ◽  
pp. 263-273 ◽  
Author(s):  
V. M. Bogod ◽  
S. Kh. Tokhchukova
Keyword(s):  
Solar Flares ◽  
Active Regions ◽  
Microwave Emission

A Study of Connections Between Solar Flares and Subsurface Flow Fields of Active Regions

2013 ◽  
pp. 57-66
Author(s):  
Yu Gao ◽  
Junwei Zhao ◽  
Hongqi Zhang
Keyword(s):  
Solar Flares ◽  
Subsurface Flow ◽  
Active Regions ◽  
Flow Fields

OPTICAL SYSTEM DESIGN OF THE DETECTOR FOR SOLAR TERAHERTZ EMISSION MEASUREMENTS

2021 ◽  
pp. 22-30
Author(s):  
Aleksandr A. KVASHNIN ◽  
Valery I. LOGACHEV ◽  
Maksim V. PHILIPPOV ◽  
Vladimir S. MAKHMUTOV ◽  
Osman MAKSUMOV ◽  
...  
Keyword(s):  
System Design ◽  
Optical System ◽  
Solar Flares ◽  
Electromagnetic Emission ◽  
Active Regions ◽  
Close Correlation ◽  
Frequency Range ◽  
Terahertz Emission ◽  
Optical System Design ◽  
Astrophysical Objects

The objectives and scientific tasks of the planned space experiment “Solntse-Terahertz” to be performed onboard the ISS Russian Segment are briefly described in the paper. In particular, the aim of the experiment is to study uninvestigated solar electromagnetic emission in the terahertz domain, in ~ 1012 – 1013 Hz (300-30 µm) frequency range. It is expected to obtain new data on solar active region emission including solar flare emission. These data are necessary to clarify the nature of solar activity and construct physical model of charged particle acceleration in active regions during solar flares and other astrophysical objects. We focus on the telescope optical system design and evaluation of main characteristics of this system. Results of simulations and comparison with the experimental verification of obtained characteristics are presented. A close correlation of the estimations and experimental results was obtained. As a result, main parameters of the telescope optical system of experimental hardware “Solntse-Terahertz” were determined. Key words: Sun, solar flares, terahertz emission, optical system.

The 1 1S-n 1 P/1 1S-2 1 P emission-line ratios in SI XIII as electron temperature diagnostics for solar flares and active regions

1990 ◽  
Vol 363 ◽  
pp. 310 ◽  
Author(s):  
F. P. Keenan ◽  
S. M. McCann ◽  
K. J. H. Phillips
Keyword(s):  
Emission Line ◽  
Electron Temperature ◽  
Solar Flares ◽  
Active Regions ◽  
Temperature Diagnostics

Weak solar flares with a detectable flux of hard X rays: Specific features of microwave radiation in the corresponding active regions

2014 ◽  
Vol 54 (8) ◽  
pp. 1045-1052 ◽  
Author(s):  
I. Yu. Grigor’eva ◽  
M. A. Livshits
Keyword(s):  
Microwave Radiation ◽  
Solar Flares ◽  
Active Regions ◽  
X Rays

scholarly journals The Role of Magnetic Helicity in Solar Flares

2005 ◽  
Vol 13 ◽  
pp. 128-131
Author(s):  
Mark G. Linton
Keyword(s):  
Solar Flares ◽  
Magnetic Energy ◽  
Active Regions ◽  
Excess Energy ◽  
Flux Tubes ◽  
Surplus Energy ◽  
Coronal Magnetic Fields ◽  
Kink Instability ◽  
Magnetic Energy Release

AbstractHelicity in coronal magnetic fields, often occurring in the form of twisted or sheared fields, can provide surplus energy which is available for release in solar flares. In this paper, several models of how this extra, non-potential, energy can be released will be reviewed. For example, twisted flux tubes can release excess energy via the kink instability. Or energy can be released via a transfer of helicity between different magnetic tubes. For untwisted field, the mutual helicity between flux tubes provides a measure of the shear in the fields, and therefore how much energy is available for release in a flare. For twisted flux tubes, the twist helicity of each tube in combination with the mutual helicity between the tubes dictate what type of reconnection the tubes can undergo and how much energy is available for release. Measuring the helicity of coronal active regions, and studying how this helicity affects magnetic energy release is therefore vital for our understanding of and our ability to predict solar flares.

Solar flare forecasting model using 3D magnetic field data

2020 ◽  
Author(s):  
Xin Huang
Keyword(s):  
Magnetic Field ◽  
Deep Learning ◽  
Solar Flare ◽  
Solar Flares ◽  
Field Data ◽  
Active Regions ◽  
Forecasting Model ◽  
Magnetic Field Data ◽  
The Magnetic Field

<p>Solar flares originate from the release of the energy stored in the magnetic field of solar active regions. Generally, the photospheric magnetograms of active regions are used as the input of the solar flare forecasting model. However, solar flares are considered to occur in the low corona. Therefore, the role of 3D magnetic field of active regions in the solar flare forecast should be explored. We extrapolate the 3D magnetic field using the potential model for all the active regions during 2010 to 2017, and then the deep learning method is applied to extract the precursors of solar flares in the 3D magnetic field data. We find that the 3D magnetic field of active regions is helpful to build a deep learning based forecasting model.</p>

A Comprehensive Study of Superstorms from 1957 to present

2020 ◽  
Author(s):  
Xing Meng ◽  
Bruce Tsurutani ◽  
Anthony Mannucci
Keyword(s):  
Solar Flares ◽  
Active Regions ◽  
Main Phase ◽  
Central Meridian ◽  
Interplanetary Shocks ◽  
Interplanetary Coronal Mass Ejection ◽  
Phase Development ◽  
Almost All ◽  
Mass Ejection ◽  
Comprehensive Study

<p>We present a comprehensive study of all 39 superstorms (minimum Dst ≤ −250 nT) occurring from 1957 to present including analyzing their main phase developments, seasonal and solar cycle dependences, as well as their solar and interplanetary causes. We find that 87% of the superstorms have a multistep main phase development or are built upon preceding geomagnetic activities, and 90% of the superstorms occurred either near solar maximum or during the declining phase.  For the superstorm association with solar activities, 54% of the superstorms were associated with X‐class solar flares, 36% were associated with M‐class flares, and 5% with C‐class flares. All solar flares related to superstorms occurred in active regions, indicating the importance of active regions to superstorms. Most flares were located in the central meridian or slightly west of it as expected. For the interplanetary conditions leading to the development of the superstorm main phase, 95% of the 19 superstorms with available solar wind data are solely caused or partially caused by the sheath anti-sunward of an interplanetary coronal mass ejection (ICME), indicating the importance of the sheath structure in driving superstorms. For eight superstorms that have identifiable interplanetary shocks preceding the ICMEs, the shock normal angles were almost all quasi‐perpendicular. Larger shock normal angles statistically corresponded to greater superstorm intensities.</p>

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