9,038 research outputs found
Prandtl number of lattice Bhatnagar-Gross-Krook fluid
The lattice Bhatnagar-Gross-Krook modeled fluid has an unchangeable unit
Prandtl number. A simple method is introduced in this letter to formulate a
flexible Prandtl number for the modeled fluid. The effectiveness was
demonstrated by numerical simulations of the Couette flow.Comment: 4 pages, uuencoded postscript fil
Collapse modes of structures under strong motions of earthquake
Under strong motion earthquakes, structures receive various types of damage. The most fatal damage is the loss of lateral strengths of a structure. The loss of lateral resistance causes a total collapse of the structure due to the P-d effect associated with the lateral displacements and the gravity loading. To eliminate such a collapse mode, to introduce into the ordinary stiff structure a flexible element which remains elastic is very effective. The flexible-stiff mixed structure can behave preferably in many aspects under strong earthquakes
BMB activity defines refractory and competent hair follicle populations during the propagation of regenerative waves
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A Hierarchical Relationship between the Fluence Spectra and CME Kinematics in Large Solar Energetic Particle Events: A Radio Perspective
We report on further evidence that solar energetic particles are organized by
the kinematic properties of coronal mass ejections (CMEs)[1]. In particular, we
focus on the starting frequency of type II bursts, which is related to the
distance from the Sun where the radio emission starts. We find that the three
groups of solar energetic particle (SEP) events known to have distinct values
of CME initial acceleration, also have distinct average starting frequencies of
the associated type II bursts. SEP events with ground level enhancement (GLE)
have the highest starting frequency (107 MHz), while those associated with
filament eruption (FE) in quiescent regions have the lowest starting frequency
(22 MHz); regular SEP events have intermediate starting frequency (81 MHz).
Taking the onset time of type II bursts as the time of shock formation, we
determine the shock formation heights measured from the Sun center. We find
that the shocks form on average closest to the Sun (1.51 Rs) in GLE events,
farthest from the Sun in FE SEP events (5.38 Rs), and at intermediate distances
in regular SEP events (1.72 Rs). Finally, we present the results of a case
study of a CME with high initial acceleration (~3 km s^-2) and a type II radio
burst with high starting frequency (~200 MHz) but associated with a minor SEP
event. We find that the relation between the fluence spectral index and CME
initial acceleration continues to hold even for this minor SEP event.Comment: 11 pages, 7 figures, 1 table, to appear in Journal of Physics:
Conference Series (JPCS), Proceedings of the 16th Annual International
Astrophysics Conference held in Santa Fe, NM, 201
The Peculiar Behavior of Halo Coronal Mass Ejections in Solar Cycle 24
We report on a remarkable finding that the halo coronal mass ejections (CMEs)
in cycle 24 are more abundant than in cycle 23, although the sunspot number in
cycle 24 has dropped by about 40%. We also find that the distribution of
halo-CME source locations is different in cycle 24: the longitude distribution
of halos is much flatter with the number of halos originating at central
meridian distance >/=60 degrees twice as large as that in cycle 23. On the
other hand, the average speed and the associated soft X-ray flare size are the
same in the two cycles, suggesting that the ambient medium into which the CMEs
are ejected is significantly different. We suggest that both the higher
abundance and larger central meridian longitudes of halo CMEs can be explained
as a consequence of the diminished total pressure in the heliosphere in cycle
24 (Gopalswamy et al. 2014). The reduced total pressure allows CMEs expand more
than usual making them appear as halos.Comment: 12 pages, 5 figures, accepted for publication in the Astrophysical
Journal Letters, April 7, 201
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