Influence of Rotation on Pulsar Radiation Characteristics

We present a relativistic model for pulsar radio emission by including the effect of rotation on coherent curvature radiation by bunches. We find that rotation broadens the width of leading component compared to the width of trailing component. We estimate the component widths in the average pulse profiles of about 24 pulsars, and find that 19 of them have a broader leading component. We explain this difference in the component widths by using the nested cone emission geometry. We estimate the effect of pulsar spin on the Stokes parameters, and find that the inclination between the rotation and magnetic axes can introduce an asymmetry in the circular polarization of the conal components. We analyze the single pulse polarization data of PSR B0329+54 at 606 MHz, and find that in its conal components, one sense of circular polarization dominates in the leading component while the other sense dominates in the trailing component. Our simulation shows that changing the sign of the impact parameter changes the sense of circular polarization as well as the swing of polarization angle.Comment: 20 pages, 4 Postscript figures, uses aastex.cls. Accepted for Publication in ApJ 200

Particle acceleration close to the supermassive black hole horizon: the case of M87

The radio galaxy M87 has recently been found to be a rapidly variable TeV emitting source. We analyze the implications of the observed TeV characteristics and show that it proves challenging to account for them within conventional acceleration and emission models. We discuss a new pulsar-type scenario for the origin of variable, very high energy (VHE) emission close to the central supermassive black hole and show that magneto-centrifugally accelerated electrons could efficiently Compton upscatter sub-mm ADAF disk photons to the TeV regime, leading to VHE characteristics close to the observed ones. This suggests, conversely, that VHE observations of highly under-luminous AGNs could provide an important diagnostic tool for probing the conditions prevalent in the inner accretion disk of these sources.Comment: 5 pages, one figure (typos corrected); based on presentation at "High Energy Phenomena in Relativistic Outflows", Dublin, Sept. 2007; accepted for publication in International Journal of Modern Physics

Understanding the radio emission geometry of multi-component radio pulsars from retardation and aberration effects

We have conducted a detailed analysis of the emission geometry of a handful of radio pulsars that have prominent, multiple-component profiles at meter wavelengths. From careful determination of the total number of emission components and their locations in pulse longitude, we find that all of the six pulsars show clear evidence for retardation and aberration effects in the conal emission beams. Using this information, coupled with a dipolar field geometry, we obtain estimates of the height and transverse location in the magnetosphere, for each of the emitting cones in these pulsars. These results support our earlier conclusions for PSR B0329+54 in that we find successive outer cones (in cases of multi-cone pulsars) being emitted at higher altitudes in the magnetosphere. The range of inferred heights is from ~200 to ~2200 km. The set of ``active'' field lines from which the conal emissions originate are located in the region from ~0.22 to ~0.74 of the polar cap radius. At the neutron star surface, these conal rings map to radii of a few to several tens of meters and the separation between successive rings is about 10 to 20 meters. We discuss the implications of these findings for the understanding of the pulsar emission geometry and for current theories and models of the emission mechanism.Comment: 20 pages, 2 figures. Accepted for Astrophysical Journal, 200

Centrifugally driven electrostatic instability in extragalactic jets

The stability problem of the rotation induced electrostatic wave in extragalactic jets is presented. Solving a set of equations describing dynamics of a relativistic plasma flow of AGN jets, an expression of the instability rate has been derived and analyzed for typical values of AGNs. The growth rate was studied versus the wave length and the inclination angle and it has been found that the instability process is much efficient with respect to the accretion disk evolution, indicating high efficiency of the instability.Comment: 7 pages, 4 figure

Pulsar Radio Emission Altitude from Curvature Radiation

We assume that the relativistic sources moving along the dipolar magnetic field lines emit curvature radiation. The beamed emission occurs in the direction of tangents to the field lines, and to receive it, the sight line must align with the tangent within the beaming angle 1/gamma, where gamma is the particle Lorentz factor. By solving the viewing geometry in an inclined and rotating dipole magnetic field, we show that, at any given pulse phase, observer tends to receive radiation only from the specific heights allowed by the geometry. We find outer conal components are emitted at higher altitudes compared to inner components including the core. At any pulse phase, low frequency emission comes from higher altitudes than high frequency emission. We have modeled the emission heights of pulse components of PSR B0329+54, and estimated field line curvature radii and particle Lorentz factors in the emission regions.Comment: 14 pages, 3 figures. Accepted for Astrophysical Journal, 200

Proportion, Risk Factors and the Impact of Dysmenorrhea among Girls

Background: Dysmenorrhea is the leading cause of recurrent short-term school absence in adolescent girls and a common problem in women of reproductive age. There are many factors related to this disorder which include a younger age, low body mass index (BMI), smoking, early menarche, and prolonged menstrual flow. Objectives: (1) To find the proportion of dysmenorrhea among girls of a nursing college; (2) To find out the risk factors and impact of dysmenorrhea.Materials and Methods: A cross-sectional study was conducted from November 2011 to April 2012 at Nursing College, VIMS, Bellary, Karnataka. Data were collected by a pre-tested and pre-designed semi-structured pro forma. The study was performed on a total of 196 students who agreed to participate and present at the time of study. Analysis was done by using Epi-info version 3.4.3.Results: The average age of the study group was 19.3+1.8 years (range 17–30). Proportion of dysmenorrhea was found to be 77% and was significantly higher in females with positive family history of dysmenorrhea when compared to the others (P<0.05), who had early age of menarche, irregular cycle, increased amount of flow, gynecological problems and lack exercise had high rate of dysmenorrhea compared to others but statistically it was not significant. In this study, because of dysmenorrhea 20.5% had class absenteeism, 23.2% college absenteeism, 44.4% had poor concentration, 31.8% were depressed, 53% were irritable and 2.6% had suicidal tendencies.Conclusion and Recommendation: There was a high proportion of dysmenorrhea and also girls were very much worried about it. There is a need to educate them about causes, treatment and also to cope with stress at the time of menstrual cycle

On the efficiency of particle acceleration by rotating magnetospheres in AGN

To investigate the efficiency of centrifugal acceleration of particles as a possible mechanism for the generation of ultra-high $\gamma$-ray nonthermal emission from TeV blazars, we study the centrifugal acceleration of electrons by rotating magnetic field lines, for an extended range of inclination angles and determine the maximum Lorentz factors $\gamma_{max}$ attainable by the electrons via this process. {Two principal limiting mechanisms for the particle acceleration, inverse Compton scattering and breakdown of the bead-on-the-wire approximation, are examined. Particles may be centrifugally accelerated up to $\gamma_{max} \simeq 10^8$ and the main limiting mechanism for the $\gamma_{max}$ is the inverse Compton scattering. The energy of centrifugally accelerated particles can be amply sufficient for the generation (via inverse Compton scattering) of the ultra-high energy (up to $20TeV$) gamma emission in TeV blazars.Comment: 7 pages 5 figure

Equivalence principle and experimental tests of gravitational spin effects

We study the possibility of experimental testing the manifestations of equivalence principle in spin-gravity interactions. We reconsider the earlier experimental data and get the first experimental bound on anomalous gravitomagnetic moment. The spin coupling to the Earth's rotation may also be explored at the extensions of neutron EDM and g-2 experiments. The spin coupling to the terrestrial gravity produces a considerable effect which may be discovered at the planned deuteron EDM experiment. The Earth's rotation should also be taken into account in optical experiments on a search for axionlike particles.Comment: 12 pages, version to appear in Physical Review

On the method of estimating emission altitude from relativistic phase shift in pulsars

The radiation by relativistic plasma particles is beamed in the direction of field line tangents in the corotating frame, but in an inertial frame it is aberrated toward the direction of rotation. We have revised the relation of aberration phase shift by taking into account of the colatitude of emission spot and the plasma rotation velocity. In the limit of small angle approximation, aberration phase shift becomes independent of the inclination angle alpha and the sight line impact angle beta. However, at larger altitudes or larger rotation phases, the shift does depend on alpha and beta. We have given an expression for the phase shift in the intensity profile by taking into account of aberration, retardation and polar cap currents. We have re-estimated the emission heights of the six classical pulsars, and analyzed the profile of a millisecond pulsar PSR J0437-4715 at 1440 MHz by fitting the Gaussians to pulse components. By this procedure we have been able to identify 11 emission components of PSR J0437-4715. We propose that they form a emission beam with 5 nested cones centered on the core. Using the phase location of component peaks, we have estimated the relativistic phase shift and the emission height of conal components. We find some of the components are emitted from the altitudes as high as 23 percent of light cylinder radius.Comment: 31 pages, 17 Postscript figures, uses aastex.cls, Revised the aberation and retardation phase shift formula

Long term monitoring of mode switching for PSR B0329+54

The mode switching phenomenon of PSR B0329+54 is investigated based on the long-term monitoring from September 2003 to April 2009 made with the Urumqi 25m radio telescope at 1540 MHz. At that frequency, the change of relative intensity between the leading and trailing components is the predominant feature of mode switching. The intensity ratios between the leading and trailing components are measured for the individual profiles averaged over a few minutes. It is found that the ratios follow normal distributions, where the abnormal mode has a wider typical width than the normal mode, indicating that the abnormal mode is less stable than the normal mode. Our data show that 84.9% of the time for PSR B0329+54 was in the normal mode and 15.1% was in the abnormal mode. From the two passages of eight-day quasi-continuous observations in 2004, and supplemented by the daily data observed with 15 m telescope at 610 MHz at Jodrell Bank Observatory, the intrinsic distributions of mode timescales are constrained with the Bayesian inference method. It is found that the gamma distribution with the shape parameter slightly smaller than 1 is favored over the normal, lognormal and Pareto distributions. The optimal scale parameters of the gamma distribution is 31.5 minutes for the abnormal mode and 154 minutes for the normal mode. The shape parameters have very similar values, i.e. 0.75^{+0.22}_{-0.17} for the normal mode and 0.84^{+0.28}_{-0.22} for the abnormal mode, indicating the physical mechanisms in both modes may be the same. No long-term modulation of the relative intensity ratios was found for both the modes, suggesting that the mode switching was stable. The intrinsic timescale distributions, for the first time constrained for this pulsar, provide valuable information to understand the physics of mode switching.Comment: 31 pages,12 figures, Accepted by the Ap