scholarly journals On the seismic emission in sunspots associated with Lorentz force changes accompanying major solar flares

2020 ◽  
Vol 497 (1) ◽  
pp. 976-987
Author(s):  
Hirdesh Kumar ◽  
Brajesh Kumar
Keyword(s):  
Lorentz Force ◽  
Solar Flares ◽  
Seismic Waves ◽  
Acoustic Power ◽  
High Energy ◽  
Space Mission ◽  
Solar Dynamics Observatory ◽  
Seismic Emission ◽  
X Ray ◽  
Power Maps

ABSTRACT Solar flares are known to generate seismic waves in the Sun. We present a detailed analysis of seismic emission in sunspots accompanying M- and X-class solar flares. For this purpose, we have used high-resolution Dopplergrams and line-of-sight magnetograms at a cadence of 45 s, along with vector magnetograms at a cadence of 135 s obtained from Helioseismic and Magnetic Imager instrument aboard the Solar Dynamics Observatory space mission. In order to identify the location of flare ribbons and hard X-ray footpoints, we have also used Hα chromospheric intensity observations obtained from Global Oscillation Network Group instruments and hard X-ray images in 12–25 keV band from the Reuvan Ramaty High Energy Solar Spectroscopic Imager spacecraft. The fast Fourier transform technique is applied to construct the acoustic velocity power map in 2.5–4 mHz band for pre-flare, spanning flare, and post-flare epochs for the identification of seismic emission locations in the sunspots. In the power maps, we have selected only those locations which are away from the flare ribbons and hard X-ray footpoints. These regions are believed to be free from any flare related artefacts in the observational data. We have identified concentrated locations of acoustic power enhancements in sunspots accompanying major flares. Our investigation provides evidence that abrupt changes in the magnetic fields and associated impulsive changes in the Lorentz force could be the driving source for these seismic emissions in the sunspots during solar flares.

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 What can He II 304 Å tell us about transient seismic emission from solar flares?

2016 ◽  
Vol 12 (S327) ◽  
pp. 113-116
Author(s):  
C. Lindsey ◽  
A. C. Donea
Keyword(s):  
Lorentz Force ◽  
Solar Flares ◽  
Solar Interior ◽  
Solar Dynamics Observatory ◽  
Transient Heating ◽  
Seismic Emission ◽  
Source Regions ◽  
Solar Dynamics

AbstractAfter neary 20 years since their discovery by Kosovichev and Zharkova, the mechanics of the release of seismic transients into the solar interior from some flares remain a mystery. Seismically emissive flares invariably show the signatures of intense chromosphere heating consistent with pressure variations sufficient to drive seismic transients commensurate with helioseismic observations—under certain conditions. Magnetic observations show the signatures of apparent magnetic changes, suggesting Lorentz-force transients that could likewise drive seismic transients—similarly subject to certain conditions. But, the diagnostic signatures of both of these prospective drivers are apparent over vast regions from which no significant seismic emission emanates. What distinguishes the source regions of transient seismic emission from the much vaster regions that show the signatures of both transient heating and magnetic variations but are acoustically unproductive? Observations of acoustically active flares in He II 304 Å by the Atomospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) offer a promising new resource with which to address this question.

scholarly journals Models of Flaring Loops

1989 ◽  
Vol 104 (1) ◽  
pp. 105-115
Author(s):  
A. Gordon Emslie
Keyword(s):  
Solar Flares ◽  
Energy Transport ◽  
High Energy ◽  
Loop Structure ◽  
Predominant Role ◽  
Release Process ◽  
Flare Loop ◽  
X Ray ◽  
Physical Mechanisms ◽  
High Energy Electrons

AbstractWe review the somewhat questionable concept of an isolated flare loop and the various physical mechanisms believed to be responsible, to some degree, for energy transport within the loop structure. Observational evidence suggests a predominant role for high-energy electrons as an energy transport mechanism, and we explore the consequences of such a scenario in some detail, focusing on radiation signatures in the soft X-ray, hard X-ray, and EUV wavebands, as observed by recent satellite observatories. We find that the predictions of flare loop models are in fact in excellent agreement with these observations, reinforcing both the notion of the loop as a fundamental component of solar flares and the belief that electron acceleration is an integral part of the flare energy release process.

X-Ray Emissions from Solar Flares and from Celestial Sources

1967 ◽  
Vol 1 (1) ◽  
pp. 4-5 ◽  
Author(s):  
T. A. Chubb
Keyword(s):  
Solar Flares ◽  
Thermal Emission ◽  
High Energy ◽  
Geiger Counter ◽  
X Rays ◽  
Large Measure ◽  
X Ray ◽  
Ion Chamber

One of the interesting questions in solar X-ray astronomy is the question as to whether the hard X-ray emission which occurs during major solar flares is a thermal or nonthermal phenomenon. The evidence for non-thermal emission has been based in large measure on a balloon-borne experiment by Peterson and Winckler, which constituted the first detection of high energy flare X-rays. In the Peterson-Winckler experiment, the incident solar X-rays were measured by both an ion chamber and a Geiger counter photometer, and from the ratio of responses, the hardness character of the incident X-rays was reduced. It was concluded that the observed result could have been explained in terms of the sudden non-thermal production of a group of electrons with energy of the order of 500 kilovolts.

Millimeter, Microwave, Hard X-Ray, and Soft X-Ray Observations of Energetic Electron Populations in Solar Flares

1994 ◽  
Vol 142 ◽  
pp. 599-610
Author(s):  
M. R. Kundu ◽  
S. M. White ◽  
N. Gopalswamy ◽  
J. Lim
Keyword(s):  
Solar Flares ◽  
Energetic Electron ◽  
Impulsive Phase ◽  
High Energy ◽  
X Rays ◽  
High Turnover ◽  
X Ray ◽  
Nonthermal Electrons ◽  
Time Profiles ◽  
Wavelength Emission

AbstractWe present comparisons of multiwavelength data for a number of solar flares observed during the major campaign of 1991 June. The different wavelengths are diagnostics of energetic electrons in different energy ranges: soft X-rays are produced by electrons with energies typically below 10 keV, hard X-rays by electrons with energies in the range 10-200 keV, microwaves by electrons in the range 100 keV-1 MeV, and millimeter-wavelength emission by electrons with energies of 0.5 MeV and above. The flares in the 1991 June active period were remarkable in two ways: all have very high turnover frequencies in their microwave spectra, and very soft hard X-ray spectra. The sensitivity of the microwave and millimeter data permit us to study the more energetic (>0.3 MeV) electrons even in small flares, where their high-energy bremsstrahlung is too weak for present detectors. The millimeter data show delays in the onset of emission with respect to the emissions associated with lower energy electrons and differences in time profiles, energy spectral indices incompatible with those implied by the hard X-ray data, and a range of variability of the peak flux in the impulsive phase when compared with the peak hard X-ray flux which is two orders of magnitude larger than the corresponding variability in the peak microwave flux. All these results suggest that the hard X-ray-emitting electrons and those at higher energies which produce millimeter emission must be regarded as separate populations. This has implications for the well-known “number problem” found previously when comparing the numbers of nonthermal electrons required to produce the hard X-ray and radio emissions.Subject headings: Sun: flares — Sun: radio radiation — Sun: X-rays, gamma rays

High Energy Transient Ionospheric Monitoring Network

1990 ◽  
Vol 8 (3) ◽  
pp. 263-265
Author(s):  
Paul J. Edwards
Keyword(s):  
Gravity Waves ◽  
Solar Flares ◽  
Gamma Ray ◽  
Monitoring Network ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Ionospheric Perturbations ◽  
X Ray ◽  
Radio Receivers ◽  
Computer Based

AbstractContinuous, wide sky coverage is essential for the detection and monitoring of infrequent, short-lived events of astrophysical interest such as supernova and nova explosions, variable X-ray sources, gamma ray bursts, gravity waves and stellar and solar flares. We propose to (1) examine past radio propagation records and (2) develop new computer based radio receivers to monitor and log ionospheric perturbations associated with these events.

scholarly journals Solar flares observed simultaneously with SphinX, GOES and RHESSI

2012 ◽  
Vol 8 (S294) ◽  
pp. 571-572 ◽  
Author(s):  
Tomasz Mrozek ◽  
Szymon Gburek ◽  
Marek Siarkowski ◽  
Barbara Sylwester ◽  
Janusz Sylwester ◽  
...  
Keyword(s):  
Energy Range ◽  
Solar Flares ◽  
Solar Minimum ◽  
Spectroscopic Analysis ◽  
High Energy ◽  
Pin Diode ◽  
X Rays ◽  
X Ray ◽  
Thermal Part ◽  
Silicon Pin Diode

AbstractIn February 2009, during recent deepest solar minimum, Polish Solar Photometer in X-rays (SphinX) begun observations of the Sun in the energy range of 1.2–15 keV. SphinX was almost 100 times more sensitive than GOES X-ray Sensors. The silicon PIN diode detectors used in the experiment were carefully calibrated on the ground using Synchrotron Radiation Source BESSY II. The SphinX energy range overlaps with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) energy range. The instrument provided us with observations of hundreds of very small flares and X-ray brightenings. We have chosen a group of solar flares observed simultaneously with GOES, SphinX and RHESSI and performed spectroscopic analysis of observations wherever possible. The analysis of thermal part of the spectra showed that SphinX is a very sensitive complementary observatory for RHESSI and GOES.

scholarly journals The First Results from “Solar X-ray Spectrometer (SOXS)” Mission

2005 ◽  
Vol 13 ◽  
pp. 622-622 ◽  
Author(s):  
Rajmal Jain ◽  
Hemant Dave ◽  
P. Sreekumar ◽  
A. B. Shah ◽  
N. M. Vadher ◽  
...  
Keyword(s):  
Solid State ◽  
Solar Flare ◽  
Energy Range ◽  
Solar Flares ◽  
High Energy ◽  
Low Energy ◽  
Energy Detector ◽  
X Ray ◽  
Phoswich Detector ◽  
First Results

Abstract“Solar X-ray Spectrometer (SOXS)” mission on-board GSAT-2 Indian spacecraft was launched on 08 May 2003 by GSLV-D2 and deployed in geostationery orbit to study the X-ray emission from solar flares with high spectral and temporal resolution. The SOXS consists of two independent payloads viz. SOXS Low Energy Detector (SLD) payload, and SOXS High Energy Detector (SHD) payload. The SLD consists of two solid state detectors Si PIN and CZT, which cover the energy range from 4-60 keV, while the SHD has NaI(Tl)/CsI(Na) sandwiched phoswich detector that covers energy range from 20 keV to 10 MeV. We present very briefly the science objectives and instrumentation of SLD payload. After the successful In-orbit Tests (IOT), the first light was fed into SLD payload on 08 June 2003 when the solar flare was already in progress. We briefly present the first results from the SLD payload.

scholarly journals Major solar flares without coronal mass ejections

2008 ◽  
Vol 4 (S257) ◽  
pp. 283-286 ◽  
Author(s):  
N. Gopalswamy ◽  
S. Akiyama ◽  
S. Yashiro
Keyword(s):  
Open Field ◽  
Coronal Mass Ejections ◽  
Solar Flares ◽  
Active Regions ◽  
High Energy ◽  
X Ray ◽  
Type Iii ◽  
High Energy Electrons ◽  
Field Lines ◽  
Microwave Bursts

AbstractWe examine the source properties of X-class soft X-ray flares that were not associated with coronal mass ejections (CMEs). All the flares were associated with intense microwave bursts implying the production of high energy electrons. However, most (85%) of the flares were not associated with metric type III bursts, even though open field lines existed in all but two of the active regions. The X-class flares seem to be truly confined because there was no material ejection (thermal or nonthermal) away from the flaring region into space.

Sign in / Sign up

Export Citation Format

Share Document