320,943 research outputs found
Eruption of a multi-flux-rope system in solar active region 12673 leading to the two largest flares in Solar Cycle 24
Solar active region (AR) 12673 in 2017 September produced two largest flares
in Solar Cycle 24: the X9.3 flare on September 06 and the X8.2 flare on
September 10. We attempt to investigate the evolutions of the two great flares
and their associated complex magnetic system in detail. Aided by the NLFFF
modeling, we identify a double-decker flux rope configuration above the
polarity inversion line (PIL) in the AR core region. The north ends of these
two flux ropes were rooted in a negative- polarity magnetic patch, which began
to move along the PIL and rotate anticlockwise before the X9.3 flare on
September 06. The strong shearing motion and rotation contributed to the
destabilization of the two magnetic flux ropes, of which the upper one
subsequently erupted upward due to the kink-instability. Then another two sets
of twisted loop bundles beside these ropes were disturbed and successively
erupted within 5 minutes like a chain reaction. Similarly, multiple ejecta
components were detected to consecutively erupt during the X8.2 flare occurring
in the same AR on September 10. We examine the evolution of the AR magnetic
fields from September 03 to 06 and find that five dipoles emerged successively
at the east of the main sunspot. The interactions between these dipoles took
place continuously, accompanied by magnetic flux cancellations and strong
shearing motions. In AR 12673, significant flux emergence and successive
interactions between the different emerging dipoles resulted in a complex
magnetic system, accompanied by the formations of multiple flux ropes and
twisted loop bundles. We propose that the eruptions of a multi-flux-rope system
resulted in the two largest flares in Solar Cycle 24.Comment: 10 pages, 8 figures. To be published in A&
Research Program towards Observation of Neutrino-Nucleus Coherent Scattering
The article describes the research program pursued by the TEXONO
Collaboration towards an experiment to observe coherent scattering between
neutrinos and the nucleus at the power reactor. The motivations of studying
this process are surveyed. In particular, a threshold of 100-200 eV has been
achieved with an ultra-low-energy germanium detector prototype. This detection
capability at low energy can also be adapted to conduct searches of Cold Dark
Matter in the low-mass region as well as to enhance the sensitivities in the
study of neutrino magnetic moments.Comment: 5 pages, 8 figures ; Proceedings of TAUP-2005 Workshop, Spain, 2005.
Updated on 2006/9/15 for Proceedings of Neutrino-2006 Conference, Santa Fe,
200
Measurement-induced entanglement of two superconducting qubits
We study the problem of two superconducting quantum qubits coupled via a
resonator. If only one quanta is present in the system and the number of
photons in the resonator is measured with a null result, the qubits end up in
an entangled Bell state. Here we look at one source of errors in this quantum
nondemolition scheme due to the presence of more than one quanta in the
resonator, previous to the measurement. By analyzing the structure of the
conditional Hamiltonian with arbitrary number of quanta, we show that the
scheme is remarkably robust against these type of errors.Comment: 4 pages, 2 figure
QCD corrections to the t-->H+b decay within the minimal supersymmetric standard model
I present the contribution of gluinos and scalar quarks to the decay rate of
the top quark into a charged Higgs boson and a bottom quark within the minimal
supersymmetric standard model, including the mixing of the scalar partners of
the left- and right-handed top quark. I show that for certain values of the
supersymmetric parameters the standard QCD loop corrections to this decay mode
are diminished or enhanced by several 10 per cent. I show that not only a small
value of 3 GeV for the gluino mass (small mass window) but also much larger
values of several hundreds of GeV's have a non-neglible effect on this decay
rate, against general belief. Last but not least, if the ratio of the vacuum
expectation values of the Higgs bosons are taken in the limit of I
obtain a drastic enhancement due to a \ dependence in the couplings.Comment: UQAM-PHE-94/01, 6 pages, plain tex, 4 figures not included, available
under request via mail or fa
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