scholarly journals M-Class Solar Flares in Solar Cycles 23 and 24: Properties and Space Weather Relevance

Universe ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 39
Author(s):  
Rositsa Miteva ◽  
Susan W. Samwel
Keyword(s):  
Space Weather ◽  
Solar Flares ◽  
Energetic Particles ◽  
Field Configuration ◽  
X Rays ◽  
Solar Cycles ◽  
Magnetic Field Configuration ◽  
Radio Emissions ◽  
Wave Radio ◽  
Magnetic Type

A comprehensive statistical analysis on the properties and accompanied phenomena of all M-class solar flares (as measured in soft X-rays) in the last two solar cycles (1996–2019) is presented here with a focus on their space weather potential. The information about the parent active region and the underlying sunspot (Hale) type is collected for each case, where possible, in order to identify photospheric precondition as precursors for the solar flare eruption or confinement. Associations with coronal mass ejections, solar energetic particles, and interplanetary radio emissions are also evaluated and discussed as possible proxies for flare eruption and subsequent space weather relevance. The results show that the majority (∼80%) of the analyzed M-class flares are of β, β-γ, and β-γ-δ magnetic field configuration. The M-class population of flares is accompanied by CMEs in 41% of the cases and about half of the flare sample has been associated with radio emission from electron beams. A much lower association (≲10%) is obtained with shock wave radio signatures and energetic particles. Furthermore, a parametric scheme is proposed in terms of occurrence rates between M-class flares and a variety of accompanied solar phenomena as a function of flare sub-classes or magnetic type. This study confirms the well-known reduced but inevitable space weather importance of M-class flares.

scholarly journals Descriptive study of X-class flares released in the year 2014, during the double peak of SC-24

2015 ◽  
Vol 11 (S320) ◽  
pp. 330-332
Author(s):  
Ahmed A. Hady ◽  
Marwa H. Mostafa ◽  
Susan W. Samwel
Keyword(s):  
Data Analysis ◽  
Solar Cycle ◽  
Solar Flares ◽  
Descriptive Study ◽  
Energetic Particles ◽  
Main Peak ◽  
Solar Cycles ◽  
Double Peak ◽  
Solar Cycle 24 ◽  
Cycle 24

AbstractDuring the declining phase of the Solar cycle 24, a new peak appeared on January 7, 2014. The release of x-class flares, with the high energetic particles, were found to be more intense than that occurred during the main peak of the same cycle. Few X-class flares were released, lately, during the year 2014. We note that during the last 5 solar cycles, a new peak has appeared, releasing high energetic particles and X-class solar flares, which are called the secondary peak or the double peak of solar cycle. The aim of this descriptive study is to follow the morphological and magnetic changes of the active region before, during, and after the production of X-class flares according to data analysis. Furthermore, the causes of the release of such eruptive storms have been discussed for the period, year 2014, during the double peak of the solar cycle 24.

scholarly journals Sources of solar energetic particles

2019 ◽  
Vol 377 (2148) ◽  
pp. 20180095 ◽  
Author(s):  
Loukas Vlahos ◽  
Anastasios Anastasiadis ◽  
Athanasios Papaioannou ◽  
Athanasios Kouloumvakos ◽  
Heinz Isliker
Keyword(s):  
Solar Corona ◽  
Space Weather ◽  
Solar Flares ◽  
Large Scale ◽  
Energetic Particles ◽  
Solar Energetic Particles ◽  
Plasma Parameters ◽  
Current Sheets ◽  
Solar Eruptions ◽  
Magnetohydrodynamic Simulations

Solar energetic particles are an integral part of the physical processes related with space weather. We present a review for the acceleration mechanisms related to the explosive phenomena (flares and/or coronal mass ejections, CMEs) inside the solar corona. For more than 40 years, the main two-dimensional cartoon representing our understanding of the explosive phenomena inside the solar corona remained almost unchanged. The acceleration mechanisms related to solar flares and CMEs also remained unchanged and were part of the same cartoon. In this review, we revise the standard cartoon and present evidence from recent global magnetohydrodynamic simulations that support the argument that explosive phenomena will lead to the spontaneous formation of current sheets in different parts of the erupting magnetic structure. The evolution of the large-scale current sheets and their fragmentation will lead to strong turbulence and turbulent reconnection during solar flares and turbulent shocks. In other words, the acceleration mechanism in flares and CME-driven shocks may be the same, and their difference will be the overall magnetic topology, the ambient plasma parameters, and the duration of the unstable driver. This article is part of the theme issue ‘Solar eruptions and their space weather impact’.

scholarly journals Solar flares and energetic particles

2012 ◽  
Vol 370 (1970) ◽  
pp. 3241-3268 ◽  
Author(s):  
Nicole Vilmer
Keyword(s):  
Particle Acceleration ◽  
Solar Flares ◽  
Interplanetary Medium ◽  
High Energy ◽  
Energetic Particles ◽  
Efficient Production ◽  
X Rays ◽  
Radio Waves ◽  
Magnetic Structures ◽  
Available Information

Solar flares are now observed at all wavelengths from γ -rays to decametre radio waves. They are commonly associated with efficient production of energetic particles at all energies. These particles play a major role in the active Sun because they contain a large amount of the energy released during flares. Energetic electrons and ions interact with the solar atmosphere and produce high-energy X-rays and γ -rays. Energetic particles can also escape to the corona and interplanetary medium, produce radio emissions (electrons) and may eventually reach the Earth's orbit. I shall review here the available information on energetic particles provided by X-ray/γ-ray observations, with particular emphasis on the results obtained recently by the mission Reuven Ramaty High-Energy Solar Spectroscopic Imager. I shall also illustrate how radio observations contribute to our understanding of the electron acceleration sites and to our knowledge on the origin and propagation of energetic particles in the interplanetary medium. I shall finally briefly review some recent progress in the theories of particle acceleration in solar flares and comment on the still challenging issue of connecting particle acceleration processes to the topology of the complex magnetic structures present in the corona.

A Discussion on the physics of the solar atmosphere - Solar flares

1976 ◽  
Vol 281 (1304) ◽  
pp. 507-513 ◽  
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Observational Data ◽  
Time Scales ◽  
Solar Atmosphere ◽  
Flux Tube ◽  
Solar Flares ◽  
Field Configuration ◽  
Magnetic Field Configuration

A summary is given of some recent observational data on solar flares. Particularly we discuss the flare build-up process and the time scales involved. We suggest as a possible magnetic field configuration a multiply kinked or supertwisted flux tube. The role of plasma turbulence and the Fermi mechanism in particle acceleration is discussed.

scholarly journals LOW-POWER SOLAR FLARES OF OPTICAL AND X-RAY WAVELENGTHS FOR SOLAR CYCLES 21–24

2020 ◽  
Vol 6 (3) ◽  
pp. 18-25
Author(s):  
Aleksandr Borovik ◽  
Anton Zhdanov
Keyword(s):  
Solar Activity ◽  
Low Power ◽  
Solar Flares ◽  
Optical Emission ◽  
Flare Activity ◽  
X Rays ◽  
Solar Cycles ◽  
X Ray ◽  
Cycle 24 ◽  
Using Data

Using data obtained in optical and X-ray wavelengths, we have analyzed solar flare activity for cycles 21–24. Over the last three cycles, solar activity is shown to decrease significantly. As compared to solar cycle 21 (the most active over the last 50 years), in cycle 24 2–4-class large optical flares are 4.4 times rarer; 1-class flares, 8.2 times; and S-class small flares, 4.1 times. The number of X-class flares decreased 3.7 times; M-class flares, 3.2 times. This confirms that secular solar activity trends affect peak values of 11-year cycles. It is shown that optical low-power flares can be accompanied by proton fluxes and X-ray bursts of different intensity, including X-class ones. Ranges of small flare emission in soft X-rays largely overlap with emission ranges of flares of high optical classes. We have confirmed that X-ray emission from solar flares appears on average 2 min before the optical emission. The X-ray maximum for small optical flares and 1-class flares occurs approximately 1 min later; for 2–4-class flares, 2 min.

Magnetic Field Configuration in Impulsive Solar Flares Inferred from Coaligned Microwave/X‐Ray Images

1997 ◽  
Vol 489 (2) ◽  
pp. 976-991 ◽  
Author(s):  
Masanori Nishio ◽  
Kentaro Yaji ◽  
Takeo Kosugi ◽  
Hiroshi Nakajima ◽  
Takashi Sakurai
Keyword(s):  
Magnetic Field ◽  
Solar Flares ◽  
Field Configuration ◽  
Magnetic Field Configuration ◽  
X Ray

scholarly journals The Transient Highly Excited Solar Flare Plasma

1972 ◽  
Vol 14 ◽  
pp. 827-842 ◽  
Author(s):  
L. D. De Feiter
Keyword(s):  
Solar Flare ◽  
Radio Emission ◽  
Special Reference ◽  
Solar Flares ◽  
Energetic Particles ◽  
X Rays ◽  
Microwave Region ◽  
X Ray ◽  
Flare Plasma ◽  
Radiation Processes

AbstractRecent observations of the energetic particles produced in solar flares indicate that the production of electrons, with energies up to about 100 keV, is a fairly common feature of small flares. In those flares the acceleration of protons and other nuclei does not extend beyond about 1 MeV.The X-ray emission often exhibits two distinct components of which the first one is produced by non-thermal, the second by thermal electrons through bremsstrahlung collisions with the ambient ions. Along with these X rays, radio emission, in the microwave region, is observed. This radio emission is usually interpreted as due to gyrosynchrotron radiation from the same electrons.In this review a discussion is presented of the processes occurring in solar flares with special reference to the acceleration and radiation processes.

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