Characteristics of Sunquake Events Observed in Solar Cycle 24

2021 ◽  
Author(s):  
Alexander Kosovichev ◽  
Ivan Sharykin
Keyword(s):  
Solar Cycle ◽  
Solar Flares ◽  
Active Regions ◽  
Impulsive Phase ◽  
High Energy ◽  
Lower Atmosphere ◽  
Solar Dynamics Observatory ◽  
X Ray ◽  
Solar Cycle 24 ◽  
Cycle 24

<p>Helioseismic response to solar flares ("sunquakes") occurs due to localized force or/and momentum impacts observed during the flare impulsive phase in the lower atmosphere. Such impacts may be caused by precipitation of high-energy particles, downward shocks, or magnetic Lorentz force. Understanding the mechanism of sunquakes is a key problem of the flare energy release and transport. Our statistical analysis of M-X class flares observed by the Solar Dynamics Observatory during Solar Cycle 24 has shown that contrary to expectations, many relatively weak M-class flares produced strong sunquakes, while for some powerful X-class flares, helioseismic waves were not observed or were weak. The analysis also revealed that there were active regions characterized by the most efficient generation of sunquakes during the solar cycle. We found that the sunquake power correlates with maximal values of the X-ray flux derivative better than with the X-ray class. The sunquake data challenge the current theories of solar flares.</p>

scholarly journals Source-region characteristics of anemone active regions in the ascending phase of solar cycle 24

2020 ◽  
Vol 642 ◽  
pp. A233
Author(s):  
R. Sharma ◽  
C. Cid
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Minimum Distance ◽  
Source Region ◽  
Coronal Holes ◽  
Active Regions ◽  
Yearly Average ◽  
Solar Cycle 24 ◽  
Cycle 24 ◽  
Rise Phase

Context. Active regions in close proximity to coronal holes, also known as anemone regions, are the best candidates for studying the interaction between closed and open magnetic field topologies at the Sun. Statistical investigation of their source-region characteristics can provide vital clues regarding their possible association with energetic events, relevant from space weather perspectives. Aims. The main goal of our study is to understand the distinct properties of flaring and non-flaring anemone active regions and their host coronal holes, by examining spatial and magnetic field distributions during the rise phase of the solar cycle, in the years 2011–2014. Methods. Anemone regions were identified from the minimum-distance threshold, estimated using the data available in the online catalogs for on-disk active regions and coronal holes. Along with the source-region area and magnetic field characteristics, associated filament and flare cases were also located. Regions with and without flare events were further selected for a detailed statistical examination to understand the major properties of the energetic events, both eruptive and confined, at the anemone-type active regions. Results. Identified anemone regions showed weak asymmetry in their spatial distribution over the solar disk, with yearly average independent from mean sunspot number trend, during the rise phase of solar cycle 24. With the progression in solar cycle, the area and minimum-distance parameters indicated a decreasing trend in their magnitudes, while the magnetic field characteristics indicated an increase in their estimated magnitudes. More than half of the regions in our database had an association with a filament structure, and nearly a third were linked with a magnetic reconnection (flare) event. Anemone regions with and without flares had clear distinctions in their source-region characteristics evident from the distribution of their properties and density analysis. The key differences included larger area and magnetic field magnitudes for flaring anemone regions, along with smaller distances between the centers of the active region and its host coronal hole.

X-Ray Flares and Activity Complexes on the Sun in Solar Cycle 24

2020 ◽  
Vol 64 (1) ◽  
pp. 58-65 ◽  
Author(s):  
E. S. Isaeva ◽  
V. M. Tomozov ◽  
S. A. Yazev
Keyword(s):  
Solar Cycle ◽  
The Sun ◽  
X Ray ◽  
Solar Cycle 24 ◽  
Cycle 24

scholarly journals Super-active regions in solar cycle 24

2015 ◽  
Vol 11 (S320) ◽  
pp. 309-314 ◽  
Author(s):  
Anqin Chen ◽  
Jingxiu Wang
Keyword(s):  
Solar Cycle ◽  
Active Regions ◽  
Total Solar Irradiance ◽  
Flare Activity ◽  
Solar Cycles ◽  
Solar Cycle 24 ◽  
Satisfactory Account ◽  
Current Cycle ◽  
Flare Index ◽  
Cycle 24

AbstractComparing with solar cycles 21-23, the level of solar activity in the current cycle is very low. So far, there have been only five SARs and 45 X class flares. The monthly smoothed total solar irradiance decreased sharply by 0.09% from the maximum of cycle 23 to the minima between cycles 23 and 24. In this contribution, we present new studies on SARs in Cycle 24. The SARs in the current cycle have relatively smaller flare index (Iflare) and composite vector field index (Icom) comparing with the SARs in cycles 22 and 23. There is a clearly linear relationship between Iflare and Icom. The emphasis of this contribution is put on the similarity and different behaviors of vector magnetic fields of the SARs in the current solar cycle and the previous ones. We try to get a satisfactory account for the general characteristics and relatively lower level of solar flare activity in Cycle 24.

On the Dynamics of the Largest Active Region of the Solar Cycle 24

2017 ◽  
Vol 13 (S335) ◽  
pp. 32-35
Author(s):  
Ranadeep Sarkar ◽  
Nandita Srivastava ◽  
Sajal Kumar Dhara
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Active Region ◽  
Comparative Study ◽  
Lorentz Force ◽  
Sunspot Group ◽  
Solar Dynamics Observatory ◽  
Solar Cycle 24 ◽  
Solar Dynamics ◽  
Cycle 24

AbstractWe have studied the dynamics of the solar active region (AR) NOAA 12192 using full-disc continuum images and the vector magnetograms observed by the Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamics Observatory (SDO). AR 12192 is the largest region of the solar cycle 24. It underwent a noticeable growth and produced 6 X-class, 22 M-class and 53 C-class flares during its disc passage. But the most peculiar fact of this AR is that it was associated with only one CME in spite of producing several X-class flares. In this work, we present the area evolution of this giant sunspot group during the first three rotations when it appeared as AR 12172, AR 12192 and AR 12209, respectively. We have also attempted to make a comparative study of the flare-related photospheric magnetic field and Lorentz force changes for both the eruptive and non-eruptive flares produced by AR 12192.

scholarly journals Magnetic instability of filaments in different solar regions

2016 ◽  
Vol 12 (S327) ◽  
pp. 71-76
Author(s):  
J. Palacios ◽  
A. Guerrero ◽  
C. Cid ◽  
E. Saiz ◽  
Y. Cerrato
Keyword(s):  
Solar Cycle ◽  
Potential Field ◽  
Active Regions ◽  
Magnetic Instability ◽  
Field Modelling ◽  
Decay Index ◽  
Solar Cycle 24 ◽  
Cycle 24 ◽  
Potential Field Modelling ◽  
3D Evaluation

AbstractMagnetic instability is a key consideration for filament eruptions and subsequent CMEs. In this contribution we are considering different magnetic conditions for active and non-active regions, such as coronal hole regions and quiet sun, and also active regions of a simple magnetic configuration. The aim is to assess magnetic instability through potential and non-potential field modelling and 3D evaluation of the magnetic decay index. Some eruptive examples from solar cycle 24 using HMI/SDO data are presented, complemented with observations of AIA/SDO.

Solar flares, CMEs and solar energetic particle events during solar cycle 24

2018 ◽  
Vol 61 (2) ◽  
pp. 777-785 ◽  
Author(s):  
Bimal Pande ◽  
Seema Pande ◽  
Ramesh Chandra ◽  
Mahesh Chandra Mathpal
Keyword(s):  
Solar Cycle ◽  
Solar Flares ◽  
Energetic Particle ◽  
Solar Energetic Particle ◽  
Solar Energetic Particle Events ◽  
Solar Cycle 24 ◽  
Cycle 24

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.

A physics-based method that can predict imminent large solar flares

Science ◽  
2020 ◽  
Vol 369 (6503) ◽  
pp. 587-591 ◽  
Author(s):  
Kanya Kusano ◽  
Tomoya Iju ◽  
Yumi Bamba ◽  
Satoshi Inoue
Keyword(s):  
Solar Cycle ◽  
Solar Flares ◽  
Solar Surface ◽  
Magnetic Polarity ◽  
Empirical Methods ◽  
Polarity Inversion ◽  
Solar Cycle 24 ◽  
Polarity Inversion Line ◽  
Magnetohydrodynamic Instability ◽  
Cycle 24

Solar flares are highly energetic events in the Sun’s corona that affect Earth’s space weather. The mechanism that drives the onset of solar flares is unknown, hampering efforts to forecast them, which mostly rely on empirical methods. We present the κ-scheme, a physics-based model to predict large solar flares through a critical condition of magnetohydrodynamic instability, triggered by magnetic reconnection. Analysis of the largest (X-class) flares from 2008 to 2019 (during solar cycle 24) shows that the κ-scheme predicts most imminent large solar flares, with a small number of exceptions for confined flares. We conclude that magnetic twist flux density, close to a magnetic polarity inversion line on the solar surface, determines when and where solar flares may occur and how large they can be.

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