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Solar Flares (solar + flare)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Helioseismic analysis of the solar flare-induced sunquake of 2005 January 15

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2007
H. Moradi
ABSTRACT We report the discovery of one of the most powerful sunquakes detected to date, produced by an X1.2-class solar flare in active region AR10720 on 2005 January 15. We used helioseismic holography to image the source of seismic waves emitted into the solar interior from the site of the flare. Acoustic egression power maps at 3 and 6 mHz with a 2-mHz bandpass reveal a compact acoustic source strongly correlated with impulsive hard X-ray and visible-continuum emission along the penumbral neutral line separating the two major opposing umbrae in the ,-configuration sunspot that predominates AR10720. At 6 mHz the seismic source has two components, an intense, compact kernel located on the penumbral neutral line of the ,-configuration sunspot that predominates AR10720, and a significantly more diffuse signature distributed along the neutral line up to ,15 Mm east and ,30 Mm west of the kernel. The acoustic emission signatures were directly aligned with both hard X-ray and visible continuum emission that emanated during the flare. The visible continuum emission is estimated at 2.0 × 1023 J, approximately 500 times the seismic emission of ,4 × 1020 J. The flare of 2005 January 15 exhibits the same close spatial alignment between the sources of the seismic emission and impulsive visible continuum emission as previous flares, reinforcing the hypothesis that the acoustic emission may be driven by heating of the low photosphere. However, it is a major exception in that there was no signature to indicate the inclusion of protons in the particle beams thought to supply the energy radiated by the flare. The continued strong coincidence between the sources of seismic emission and impulsive visible continuum emission in the case of a proton-deficient white-lightflare lends substantial support to the ,back-warming' hypothesis, that the low photosphere is significantly heated by intense Balmer and Paschen continuum-edge radiation from the overlying chromosphere in white-light flares. [source]

Space weather degrades GPS signals

ASTRONOMY & GEOPHYSICS, Issue 3 2007
Article first published online: 12 JUN 200
A powerful solar flare on 6 December last year produced so much radio noise that GPS signals were significantly affected, according to researchers from Cornell University. This raises the question of how badly such systems would be affected at solar maximum. [source]

An interpretation of rapid changes in the magnetic field associated with solar flares

ASTRONOMISCHE NACHRICHTEN, Issue 8 2008
I.V. Oreshina
Abstract The energy source of a flare is the magnetic field in the corona. A topological model of the magnetic field is used here for interpreting the recently discovered drastic changes in magnetic field associated with solar flares. The following observational results are self-consistently explained: (1) the transverse field strength decreases at outer part of active regions and increases significantly in their centers; (2) the center-of-mass positions of opposite magnetic polarities converge towards the magnetic neutral line just after flares onset; (3) the magnetic flux of active regions decreases steadily during the course of flares. For X-class flares, almost 50% events show such changes. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Measurement of linear polarization in the H, line in solar flares

ASTRONOMISCHE NACHRICHTEN, Issue 4 2003
Article first published online: 28 MAY 200, P. Kotr
Abstract Large solar telescopes built at places with a quite excellent seeing, equipped with a sophisticated optics and control system are too expensive and unique to be used currently in hunting of sudden and short-lasting activity events, e.g. flares and eruptive prominences. For a systematic observation of selected kinds of active phenomena it is still necessary to use smaller or medium-sized telescopes equipped with a special setup of devices. Detection of linear polarization in the H, line emitted in a flare seems to be just a right task and delicate matter for such a systematic observation. This kind of polarization is supposed to be generated by particle beams accelerated in thke corona and directed towards denser chromospheric layers where the particle beams deposit their kinetic energy. As the accelerated particle beams possess a preferred direction of velocity they can produce a linearly polarized light. However, the occurrence of the accelerated particle beams and the related linear polarization in the H, line may have a tendency to appear: 1) at the early beginning of a flare 2) in pulses lasting just a few seconds or even less. To measure the linear polarization in flares regularly we have built an additional branch in the Ond,ejov multichannel flare spectrograph. In this paper we describe the optical system, the detectors, the method used for data recording and reduction and we also briefly discuss the first results. [source]