11 research outputs found
Enhanced Acoustic Emission in Relation to the Acoustic Halo Surrounding Active Region 11429
The use of acoustic holography in the high-frequency -mode spectrum can
resolve the source distributions of enhanced acoustic emissions within halo
structures surrounding active regions. In doing so, statistical methods can
then be applied to ascertain relationships with the magnetic field. This is the
focus of this study. The mechanism responsible for the detected enhancement of
acoustic sources around solar active regions has not yet been explained.
Furthermore the relationship between the magnetic field and enhanced acoustic
emission has not yet been comprehensively examined. We have used vector
magnetograms from the \Helioseismic and Magnetic Imager (HMI) on-board the
Solar Dynamics Observatory (SDO) to image the magnetic-field properties in the
halo. We have studied the acoustic morphology of an active region, with a
complex halo and "glories," and we have linked some acoustic properties to the
magnetic-field configuration. In particular, we find that acoustic sources are
significantly enhanced in regions of intermediate field strength with
inclinations no different from the distributions found in the quiet Sun.
Additionally we have identified a transition region between the active region
and the halo, in which the acoustic source power is hindered by inclined fields
of intermediate field strength. Finally, we have compared the results of
acoustic emission maps, calculated from holography, and the commonly used local
acoustic maps, finding that the two types of maps have similar properties with
respect to the magnetic field but lack spatial correlation when examining the
highest-powered regions.Comment: 19 pages, 8 figures, Accepted by Solar Physic
Radiation fields of disk, BLR and torus in quasars and blazars: implications for gamma-ray absorption
The radiation fields external to the jets and originating from within a few
parsecs from the black hole, are discussed in this paper. They are the direct
radiation from an accretion disk in symbiosis with jets, the radiation field
from the broad line region (BLR) surrounding the accretion disk, and the
infrared radiation from a dusty torus. The jet/disk symbiosis modifies the
energetics in the central parsec of AGN such that for a given accretion rate, a
powerful jet would occur at the expense of the disk luminosity, and
consequently the disk would less efficiently ionize the BRL clouds or heat the
dust in the torus, thereby affecting potentially important target photon fields
for interactions of gamma-rays, accelerated electrons and protons along the
jet.
Motivated by unification schemes of active galactic nuclei, we briefly review
the evidence for the existence of broad line regions and small-scale dust tori
in BL Lacs and Fanaroff-Riley Class I (FR-I) radio galaxies. We propose that an
existing jet-accretion disk symbiosis can be extrapolated to provide a large
scale-symbiosis between other important dusty constituents of the blazar/FR-I
family. In the present paper, we discuss in the context of this symbiosis
interactions of GeV and TeV gamma-rays produced in the jet with the various
radiation fields external to the jet in quasars and blazars, taking account the
anisotropy of the radiation.Comment: 27 pages, 12 figures. submitted to Astroparticle Physic
Variations of the magnetic fields in large solar flares
We present preliminary results from high resolution observations obtained with the Michelson Doppler Imager (MDI) instrument on the SOHO of two large solar flares of 14 July 2000 and 24 November 2000. We show that rapid variations of the line-of-sight magnetic field occured on a time scale of a few minutes during the flare explosions. The reversibility/irreversibility of the magnetic field of both active regions is a very good tool for understanding how the magnetic energy is released in these flares. The observed sharp increase of the magnetic energy density at the time of maximum of the solar flare could involve an unknown component which deposited supplementary energy into the system.H. Schunker, A. -C. Done
The structure of accretion flow at the base of jets in AGN
Donea, Alina-C; Biermann, Peter
On mode conversion, reflection, and transmission of magnetoacoustic waves from above in an isothermal stratified atmosphere
Enhanced Acoustic Emission in Relation to the Acoustic Halo Surrounding Active Region 11429
Thank You to Our 2021 Reviewers
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