199 research outputs found
MHD Modeling for Formation Process of Coronal Mass Ejections: Interaction between Ejecting Flux Rope and Ambient Field
We performed magnetohydrodynamic simulation of a formation process of coronal
mass ejections (CMEs), focusing on interaction (reconnection) between an
ejecting flux rope and its ambient field. We examined three cases with
different ambient fields: no ambient field, and cases with dipole field of two
opposite directions which are parallel and anti-parallel to that of the flux
rope surface. As a result, while the flux rope disappears in the anti-parallel
case, in other cases the flux ropes can evolve to CMEs and show different
amounts of rotation of the flux rope. The results imply that the interaction
between an ejecting flux rope and its ambient field is an important process for
determining CME formation and CME orientation, and also show that the amount
and direction of magnetic flux within the flux rope and the ambient field are
key parameters for CME formation. Especially, the interaction (reconnection)
plays a significant role to the rotation of the flux rope, with a process
similar to "tilting instability" in a spheromak-type experiment of laboratory
plasma.Comment: 24 pages, 5 figures. Accepted for publication in Ap
CKP Hierarchy, Bosonic Tau Function and Bosonization Formulae
We develop the theory of CKP hierarchy introduced in the papers of Kyoto
school [Date E., Jimbo M., Kashiwara M., Miwa T., J. Phys. Soc. Japan 50
(1981), 3806-3812] (see also [Kac V.G., van de Leur J.W., Adv. Ser. Math.
Phys., Vol. 7, World Sci. Publ., Teaneck, NJ, 1989, 369-406]). We present
appropriate bosonization formulae. We show that in the context of the CKP
theory certain orthogonal polynomials appear. These polynomials are polynomial
both in even and odd (in Grassmannian sense) variables
747-4 Evaluation of Regurgitant Jets by Sound Intensity Using a Pulsatile Flow Model: Potential Contribution of Regurgitant Volume and Reynolds Number
Our goal in this study was to determine whether a new type of digital heart sound analysis method could give quantitative information about flow velocity and volume so as to allow a potentially lower-cost approach to followup studies of patients with stenotic or regurgitant valve lesions. To elucidate the relationships between hydrodynamic factors such as Reynolds number, flow velocity and flow volume and the sound characteristics of cardiac murmurs, we developed an in vitro pulsatile flow model with variable orifice size and shape (circular 0.11 cm2, 0.24 cm2, 1.77 cm2and 3.80 cm2; oval 0.24 cm2, with a ratio of major to minor axis=2; rectangular 0.24 cm2, ratio=4). Heart sounds were recorded with a new digital system (MCG) with real time spectral analysis and display and averaged over 15 “cardiac” cycles. Mean flow rate ranged from 0.6 l/min to 6 l/min. Actual instantaneous flow rate was measured using an ultrasonic flow meter for peak flow rates 1.6 l/min to 16.8 l/min. Reynolds number ranged from 6820 to 40050. For each orifice, there was an excellent relationship between total integrated sound energy (See figure: integration of intensity (I) and frequency (F) over time (T).) obtained by digital processing and Reynolds number, peak flow velocity and peak flow rate (r=0.89–0.97, 0.89–0.97, 0.93–D.99, P<0.001, respectively). The best relationship was obtained for the smallest orifice. Higher sound energies were detected for any given flow volume in asymmetrical orifices, probably due to higher turbulence. For all orifices combined, a correlation was found between peak frequency and peak velocity, but only total sound energywas correlated with peak flow rate (r=0.84, P<0.0t). Total integrated sound energy determined digitally is related to peak flow rate; peak velocity and Reynolds number parallel peak sound frequency
Handedness manipulation of propagating antiferromagnetic magnons
Antiferromagnetic magnons possess a distinctive feature absent in their
ferromagnetic counterparts: the presence of two distinct handedness modes, the
right-handed (RH) and left-handed (LH) precession modes. The magnon handedness
determines the sign of spin polarization carried by the propagating magnon,
which is indispensable for harnessing the diverse functionalities. However, the
control of coherently propagating magnon handedness in antiferromagnets has
remained elusive so far. Here we demonstrate the manipulation and electrical
readout of propagating magnon handedness in perpendicularly magnetized
synthetic antiferromagnets (SAF). We find that the antiferromagnetic magnon
handedness can be directly identified by measuring the inverse spin Hall effect
(ISHE) voltage, which arises from the spin pumping effect caused by the
propagating antiferromagnetic magnons in the SAF structure. The RH and LH modes
of the magnon can be distinguishable particularly when the SAF structure is
sandwiched by heavy metals with the same sign of spin Hall angle. Moreover, we
succeed in controlling the handedness of propagating antiferromagnetic magnons
by tuning the excitation microwave frequency. This work unveils promising
avenues for harnessing magnon unique properties in antiferromagnet-based
magnonic applications
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