44,966 research outputs found
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
Orbital Angular Momentum in Scalar Diquark Model and QED
We compare the orbital angular momentum of the 'quark' in the scalar diquark
model as well as that of the electron in QED (to order {\alpha}) obtained from
the Jaffe-Manohar de- composition to that obtained from the Ji relation. We
estimate the importance of the vector potential in the definition of orbital
angular momentum
Reactor Fuel Fraction Information on the Antineutrino Anomaly
We analyzed the evolution data of the Daya Bay reactor neutrino experiment in
terms of short-baseline active-sterile neutrino oscillations taking into
account the theoretical uncertainties of the reactor antineutrino fluxes. We
found that oscillations are disfavored at with respect to a
suppression of the reactor antineutrino flux and at
with respect to variations of the and
fluxes. On the other hand, the analysis of the rates of the
short-baseline reactor neutrino experiments favor active-sterile neutrino
oscillations and disfavor the suppression of the flux at
and variations of the and fluxes
at . We also found that both the Daya Bay evolution data and the
global rate data are well-fitted with composite hypotheses including variations
of the or fluxes in addition to
active-sterile neutrino oscillations. A combined analysis of the Daya Bay
evolution data and the global rate data shows a slight preference for
oscillations with respect to variations of the and
fluxes. However, the best fits of the combined data are given
by the composite models, with a preference for the model with an enhancement of
the flux and relatively large oscillations.Comment: 9 page
Parametric survey of longitudinal prominence oscillation simulations
It is found that both microflare-sized impulsive heating at one leg of the
loop and a suddenly imposed velocity perturbation can propel the prominence to
oscillate along the magnetic dip. An extensive parameter survey results in a
scaling law, showing that the period of the oscillation, which weakly depends
on the length and height of the prominence, and the amplitude of the
perturbations, scales with , where represents the
curvature radius of the dip, and is the gravitational acceleration of
the Sun. This is consistent with the linear theory of a pendulum, which implies
that the field-aligned component of gravity is the main restoring force for the
prominence longitudinal oscillations, as confirmed by the force analysis.
However, the gas pressure gradient becomes non-negligible for short
prominences. The oscillation damps with time in the presence of non-adiabatic
processes. Compared to heat conduction, the radiative cooling is the dominant
factor leading to the damping. A scaling law for the damping timescale is
derived, i.e., , showing
strong dependence on the prominence length , the geometry of the magnetic
dip (characterized by the depth and the width ), and the velocity
perturbation amplitude . The larger the amplitude, the faster the
oscillation damps. It is also found that mass drainage significantly reduces
the damping timescale when the perturbation is too strong.Comment: 17 PAGES, 8FIGURE
The Counting of Generalized Polarizabilities
We demonstrate a concise method to enumerate the number of generalized
polarizabilities---quantities characterizing the independent observables in
singly-virtual Compton scattering---for a target particle of arbitrary spin s.
By using crossing symmetry and J^{PC} conservation, we show that this number is
(10s+1+delta_{s,0}).Comment: 10 pages, revtex4, no figures. Version to appear in Phys. Rev. D.
Paper now divided into sections and clarifying comments added, but physics
content unchange
Leading Chiral Contributions to the Spin Structure of the Proton
The leading chiral contributions to the quark and gluon components of the
proton spin are calculated using heavy-baryon chiral perturbation theory.
Similar calculations are done for the moments of the generalized parton
distributions relevant to the quark and gluon angular momentum densities. These
results provide useful insight about the role of pions in the spin structure of
the nucleon, and can serve as a guidance for extrapolating lattice QCD
calculations at large quark masses to the chiral limit.Comment: 8 pages, 2 figures; a typo in Ref. 7 correcte
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