Effects of suprathermal electrons on the proton temperature anisotropy in space plasmas: Electromagnetic ion-cyclotron instability

In collision-poor plasmas from space, e.g., the solar wind and planetary magnetospheres, the kinetic anisotropy of the plasma particles is expected to be regulated by the kinetic instabilities. Driven by an excess of ion (proton) temperature perpendicular to the magnetic field $(~T_\perp >T_\parallel)$, the electromagnetic ion-cyclotron (EMIC) instability is fast enough to constrain the proton anisotropy, but the observations do not conform to the instability thresholds predicted by the standard theory for bi-Maxwellian models of the plasma particles. This paper presents an extended investigation of the EMIC instability in the presence of suprathermal electrons which are ubiquitous in these environments. The analysis is based on the kinetic (Vlasov-Maxwell) theory assuming that both species, protons and electrons, may be anisotropic, and the EMIC unstable solutions are derived numerically providing an accurate description for conditions typically encountered in space plasmas. The effects of suprathermal populations are triggered by the electron anisotropy and the temperature contrast between electrons and protons. For certain conditions the anisotropy thresholds exceed the limits of the proton anisotropy measured in the solar wind considerably restraining the unstable regimes of the EMIC modes.Comment: Accepted for publication in Astrophysics and space scienc

Comparing the counter-beaming and temperature anisotropy driven aperiodic electron firehose instabilities in collisionless plasma environments

The electron firehose instabilities are among the most studied kinetic instabilities, especially in the context of space plasmas, whose dynamics is mainly controlled by collisionless wave-particle interactions. This paper undertakes a comparative analysis of the aperiodic electron firehose instabilities excited either by the anisotropic temperature or by the electron counter-beaming populations. Two symmetric counter-beams provide an effective kinetic anisotropy similar to the temperature anisotropy of a single (non-drifting) population, with temperature along the magnetic field direction larger than that in perpendicular direction. Therefore, the counter-beaming plasma is susceptible to firehose-like instabilities (FIs), parallel and oblique branches. Here we focus on the oblique beaming FI, which is also aperiodic when the free energy is provided by symmetric counter-beams. Our results show that, for relative small drifts or beaming speeds ($U$), not exceeding the thermal speed ($\alpha$), the aperiodic FIs exist in the same interval of wave-numbers and the same range of oblique angles (with respect to the magnetic field direction), but the growth rates of counter-beaming FI (CBFI) are always higher than those of temperature anisotropy FI (TAFI). For $U/\alpha > 1$, however, another electrostatic two-stream instability (ETSI) is also predicted, which may have growth rates higher than those of CBFI, and may dominate in that case the dynamics.Comment: 19 pages, 6 figures, 2 tables, accepted for publication in The Astrophysical Journa

Like-sign dimuon charge asymmetry in Randall-Sundurm model

We confirm that in order to account for the recent D\O\ result of large like-sign dimuon charge asymmetry, a considerable large new physics effect in $\Gamma_{12}^s$ is required in addition to a large CP violating phase in $B_s -\bar{B}_s$ mixing. In the Randall-Sundrum model of warped geometry, where the fermion fields reside in the bulk, new sources of flavor and CP violation are obtained. We analyze the like-sign dimuon asymmetry in this class of model, as an example of the desired new physics. We show that the wrong charge asymmetry, $a_{sl}^s$, which is related to the dimuon asymmetry, is significantly altered compared to the Standard Model value. However, experimental limits from $\Delta M_s$, $\Delta\Gamma_s$ as well as $K$ mixing and electroweak corrections constrain it to be greater than a $\sigma$ away from its experimental average value. This model cannot fully account for the D\O\ anomaly due to its inability to generate sufficient new contribution to the width difference $\Gamma^s_{12}$, even though the model can generate large contribution to the mass difference $M^s_{12}$.Comment: 20 pages, 9 figures, discussions and references added, accepted for publication in Physical Review

A simple method to assess walkability around metro stations

The ability to walk or ride a bike safely to and from metro stations is essential to the success of any metro service, especially for car users switching to the service. The main purpose of this study is to develop and apply a simple method to assess, compare, and rank walkability around different metro stations, with a priority order and specific recommendations for improvements. The proposed method depends on extracting different walkability variables in the catchment areas around metro stations. Three catchment areas around three proposed metro stations in the emerging city of Doha, Qatar were investigated using the proposed method to demonstrate its usefulness. The method was successful in comparing and ranking the different catchment areas, in addition to identifying priority areas for walkability enhancements in each area. This method is simple and can benefit professionals, practitioners, and policy makers to make swift decisions for future corrective measures, and can also be used to evaluate changes over time. 2018 Inderscience Enterprises Ltd.Scopu

The relationship between the dimensions of the internal auditory canal and the anomalies of the vestibulocochlear nerve

Background: Internal auditory canal (IAC) stenosis and vestibulocochlear nerve (VCN) abnormalities have been reported to be associated with sensorineural hearing loss. Previous studies classified the normal dimensions of the IAC and its anomalies with no consideration of the VCN. Other studies categorised the VCN development in only stenotic canals. In the present study, an anatomical classification of the normal dimensions of the IAC and its anomalies and their association with malformations of the VCN and its subdivisions were described. Materials and methods: Retrospective review was undertaken for children ranged from 1 to 10 years. A total of 764 canals were investigated for pre-operative assessment of cochlear implantation. Other 100 canals of normal hearing ears were included as the control group. The maximum anteroposterior diameter, considered the width of the canal, was measured in axial plane and the length of the canal was identified in coronal plane. The canals were categorised normal: if they are from 3 to 8 mm, patulous: if they are more than 8 mm, stenotic: if they are less than 3 mm and atretic if absent, using multislice computed tomography. The VCN trunks and their subdivisions were investigated using magnetic resonance imaging. Results: Internal auditory canals were found normal in 66% with a mean width: 5.27 ± ± 0.68, patulous in 17% with a mean width 113% more than that of the control group (p = 0.000), stenotic in 13% with a mean width 73% less as compared to that of the control group (p = 0.000) and atretic in 4% of the experimental canals. The VCN trunks were found normal with well-developed subdivisions in 77.8% of the normal canals, 98.4% of the patulous canals, and 19.2% of the stenotic canals. The VCN trunks were normal with hypoplastic subdivisions in 11.3% of the normal canals, 1.6% in the patulous canals, and 61.6% in the stenotic canals with a mean width 52% less than that of the normal trunk with developed subdivisions. Hypoplastic VCN trunks with absent subdivisions were reported in 7.3% of the normal canals, 11.1% of the stenotic canals and in 3.2% of the atretic canals. The VCN trunks were not found in 3.6% of the normal canals, in 8.1% of the stenotic canals and in 96.8% of the atretic canals. Conclusions: Internal auditory canal formation was dependent on the process of development and growth of the eighth cranial nerve and its subdivisions that greatly affected the completion of IAC canalisation. This paper could serve as a reference providing a quantitative classification of the relationship between the dimensions of the IAC and the development of the VCN trunk and its subdivisions

Radiation Patterns Account of a Circular Microstrip Antenna Loaded Two Annular

In this paper, theoretical study of circular microstrip antenna loaded two annular (CMSAL2AR) and calculation of the radiation pattern using principle equivalence with moment of method formulation of electromagnetic radiation in this these based on the bodies of revolution (BoR), which are generated by revolution a planar curve about an axis called axis of symmetry to solving the electric fields integral equation (EFIE) and magnetic field integral equation (MFIE). To find an unknown electric current density  on the conductor surface ,and both unknowns electric and magnetic density  current on the dielectric surface which are  responsible for the generation of far fields radiation in the space for the components (Eθ ,Eφ) ,the surface currents was represented by a set of basis functions that give the Fourier series because the body has a circular symmetry property and then select a set of weighted  functions to find a linear system by using.......