Outflows driven by Giant Protoplanets

We investigate outflows driven by a giant protoplanet using three-dimensional MHD nested grid simulations. We consider a local region around the protoplanet in the protoplanetary disk, and calculate three models: (a) unmagnetized disk model, (b) magnetized disk model having magnetic field azimuthally parallel to the disk, and (c) magnetic field perpendicular to the disk. Outflows with velocities, at least, 10 km/s are driven by the protoplanets in both magnetized disk models, while outflow does not appear in unmagnetized disk model. Tube-like outflows along the azimuthal direction of the protoplanetary disk appear in model with magnetic field being parallel to the disk. In this model, the magnetically dominated regions (i.e., density gap) are clearly contrasted from other regions and spiral waves appear near the protoplanet. On the other hand, in model with magnetic field being perpendicular to the disk, outflows are driven by a protoplanet with cone-like structure just as seen in the outflow driven by a protostar. Magnetic field lines are strongly twisted near the protoplanet and the outflows have well-collimated structures in this model.These outflows can be landmarks for searching exo-protoplanets in their formation stages. Our results indicate that the accretion rate onto the protoplanet tend to have a larger value than that expected from previous hydrodynamical calculations, since a fraction of the angular momentum of circum-planetary disk is removed by outflows, enhanced non-axisymmetric patterns caused by magnetic field, and magnetic braking. Possible implications for observation are also briefly discussed.Comment: 11 pages, 3 figures, Submitted to ApJL, For high resolution figures see http://www2.scphys.kyoto-u.ac.jp/~machidam/jupiter/doc/resubmit_0703.pd

Chiral spin-wave edge modes in dipolar magnetic thin films

Based on a linearized Landau-Lifshitz equation, we show that two-dimensional periodic allay of ferromagnetic particles coupled with magnetic dipole-dipole interactions supports chiral spin-wave edge modes, when subjected under the magnetic field applied perpendicular to the plane. The mode propagates along a one-dimensional boundary of the system in a unidirectional way and it always has a chiral dispersion within a band gap for spin-wave volume modes. Contrary to the well-known Damon-Eshbach surface mode, the sense of the rotation depends not only on the direction of the field but also on the strength of the field; its chiral direction is generally determined by the sum of the so-called Chern integers defined for spin-wave volume modes below the band gap. Using simple tight-binding descriptions, we explain how the magnetic dipolar interaction endows spin-wave volume modes with non-zero Chern integers and how their values will be changed by the field.Comment: 18 pages, 16 figures, some trivial typo in equations are fixe

Ultra Low Loss Trench Gate PCI-PiN Diode with VF<350mV

PiN diode forward voltage drop was reduced to as low as 325mV by the pulsed carrier injection (PCI) mechanism with trench MOS gate as the integrated injection control switch. The conventional PiN diodes have voltage drop of about 0.8V which is equivalent to 1%-2% energy loss in home appliances. The proposed PCI-PiN diode reduces the loss by more than 50% and the diode structure has process compatibility to conventional IGBTs and trench MOSFETs for easy implementation into mass production. The authors also confirmed PCI concept with the experiment with BSIT.2011 23rd International Symposium on Power Semiconductor Devices & Ics (ISPSD. 2011), May 23?26, 2011, San Diego, California, US

Topological chiral magnonic edge mode in a magnonic crystal

Topological phases have been explored in various fields in physics such as spintronics, photonics, liquid helium, correlated electron system and cold-atomic system. This leads to the recent foundation of emerging materials such as topological band insulators, topological photonic crystals and topological superconductors/superfluid. In this paper, we propose a topological magnonic crystal which provides protected chiral edge modes for magnetostatic spin waves. Based on a linearized Landau-Lifshitz equation, we show that a magnonic crystal with the dipolar interaction acquires spin-wave volume-mode band with non-zero Chern integer. We argue that such magnonic systems are accompanied by the same integer numbers of chiral spin-wave edge modes within a band gap for the volume-mode bands. In these edge modes, the spin wave propagates in a unidirectional manner without being scattered backward, which implements novel fault-tolerant spintronic devices.Comment: 12 pages, 7 figure

On Galloping Oscillation of Square Prism in Two Dimensional Uniform Flow

In the connection of frequently used structural members of longspanned bridges, the aeroelastic characteristics of a square prism are investigated, based on the quasi-steady theory. The experimental results of the wind tunnel tests are compared with the theoretical characteristics, using the theory given by G. V. Parkinson. In this paper, some considerations on the critical wind velocity for galloping phenomenon of square prism are presented. Also, the qualitataive method to determine the induced amplitude is discussed