29,461 research outputs found
H-Alpha and Hard X-Ray Observations of a Two-Ribbon Flare Associated with a Filament Eruption
We perform a multi-wavelength study of a two-ribbon flare on 2002 September
29 and its associated filament eruption, observed simultaneously in the H-alpha
line by a ground-based imaging spectrograph and in hard X-rays by RHESSI. The
flare ribbons contain several H-alpha bright kernels that show different
evolutional behaviors. In particular, we find two kernels that may be the
footpoints of a loop. A single hard X-ray source appears to cover these two
kernels and to move across the magnetic neutral line. We explain this as a
result of the merging of two footpoint sources that show gradually asymmetric
emission owing to an asymmetric magnetic topology of the newly reconnected
loops. In one of the H-alpha kernels, we detect a continuum enhancement at the
visible wavelength. By checking its spatial and temporal relationship with the
hard X-ray emission, we ascribe it as being caused by electron beam
precipitation. In addition, we derive the line-of-sight velocity of the
filament plasma based on the Doppler shift of the filament-caused absorption in
the H-alpha blue wing. The filament shows rapid acceleration during the
impulsive phase. These observational features are in principal consistent with
the general scenario of the canonical two-ribbon flare model.Comment: 15 pages, 5 figures, accepted for publication in Ap
Weight function for the quantum affine algebra
We give a precise expression for the universal weight function of the quantum
affine algebra . The calculations use the technique of
projecting products of Drinfeld currents on the intersections of Borel
subalgebras.Comment: 28 page
Reciprocatory magnetic reconnection in a coronal bright point
Coronal bright points (CBPs) are small-scale and long-duration brightenings
in the lower solar corona. They are often explained in terms of magnetic
reconnection. We aim to study the sub-structures of a CBP and clarify the
relationship among the brightenings of different patches inside the CBP. The
event was observed by the X-ray Telescope (XRT) aboard the Hinode spacecraft on
2009 August 2223. The CBP showed repetitive brightenings (or CBP flashes).
During each of the two successive CBP flashes, i.e., weak and strong flashes
which are separated by 2 hr, the XRT images revealed that the CBP was
composed of two chambers, i.e., patches A and B. During the weak flash, patch A
brightened first, and patch B brightened 2 min later. During the
transition, the right leg of a large-scale coronal loop drifted from the right
side of the CBP to the left side. During the strong flash, patch B brightened
first, and patch A brightened 2 min later. During the transition, the
right leg of the large-scale coronal loop drifted from the left side of the CBP
to the right side. In each flash, the rapid change of the connectivity of the
large-scale coronal loop is strongly suggestive of the interchange
reconnection. For the first time we found reciprocatory reconnection in the
CBP, i.e., reconnected loops in the outflow region of the first reconnection
process serve as the inflow of the second reconnection process.Comment: 13 pages, 8 figure
Chiral phase transition of (2+1)-flavor QCD
We present here results on the determination of the critical temperature in
the chiral limit for (2+1)-flavor QCD. We propose two novel estimators of the
chiral critical temperature where quark mass dependence is strongly suppressed
compared to the conventional estimator using pseudo-critical temperatures. We
have used the HISQ/tree action for the numerical simulation with lattices with
three different temporal extent 6, 8, 12 and varied the aspect ratio
over the range . To approach the chiral
limit, the light quark mass has been decreased keeping the strange quark mass
fixed at its physical value. Our simulations correspond to the range of pion
masses, 55 MeV 160 MeV.Comment: Prepared for the proceedings of Quark Matter 201
Heavy Quark diffusion from lattice QCD spectral functions
We analyze the low frequency part of charmonium spectral functions on large
lattices close to the continuum limit in the temperature region as well as for . We present evidence for the
existence of a transport peak above and its absence below . The
heavy quark diffusion constant is then estimated using the Kubo formula. As
part of the calculation we also determine the temperature dependence of the
signature for the charmonium bound state in the spectral function and discuss
the fate of charmonium states in the hot medium.Comment: 4 pages, Proceedings for Quark Matter 2011 Conference, May 23-28,
2011, Annecy, Franc
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