اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدتأخير التفاصيل المعتمد على التردد من المغناطيس الناري للبولسار
Differential Frequency-dependent Delay from the Pulsar Magnetosphere
683
0
0.0
(
0
)
اسأل ChatGPT حول البحث
وبينما تظهر بعض البولسارات الإذاعية بالضوء بالضوء، حيث تظهر البولسارات الفرعية في طول البولس بنمط نظامي، نحن نفحص هنا كيف تتطور بولسارات البولسارات الفرعية لبولسار بي 0809 + 74 مع الوقت والتردد المرئي. نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذلك، نظرا لذل
Some radio pulsars show clear drifting subpulses, in which subpulses are seen to drift in pulse longitude in a systematic pattern. Here we examine how the drifting subpulses of PSR B0809+74 evolve with time and observing frequency. We show that the subpulse period (P3) is constant on timescales of days, months and years, and between 14-5100 MHz. Despite this, the shapes of the driftbands change radically with frequency. Previous studies have concluded that, while the subpulses appear to move through the pulse window approximately linearly at low frequencies (< 500 MHz), a discrete step of 180 degrees in subpulse phase is observed at higher frequencies (> 820 MHz) near to the peak of the average pulse profile. We use LOFAR, GMRT, GBT, WSRT and Effelsberg 100-m data to explore the frequency-dependence of this phase step. We show that the size of the subpulse phase step increases gradually, and is observable even at low frequencies. We attribute the subpulse phase step to the presence of two separate driftbands, whose relative arrival times vary with frequency - one driftband arriving 30 pulses earlier at 20 MHz than it does at 1380 MHz, whilst the other arrives simultaneously at all frequencies. The drifting pattern which is observed here cannot be explained by either the rotating carousel model or the surface oscillation model, and could provide new insight into the physical processes happening within the pulsar magnetosphere.
قيم البحث
اقرأ أيضاً
We present the structure of the 3D ideal MHD pulsar magnetosphere to a radius ten times that of the light cylinder, a distance about an order of magnitude larger than any previous such numerical treatment. Its overall structure exhibits a stable, smo
oth, well-defined undulating current sheet which approaches the kinematic split monopole solution of Bogovalov 1999 only after a careful introduction of diffusivity even in the highest resolution simulations. It also exhibits an intriguing spiral region at the crossing of two zero charge surfaces on the current sheet, which shows a destabilizing behavior more prominent in higher resolution simulations. We discuss the possibility that this region is physically (and not numerically) unstable. Finally, we present the spiral pulsar antenna radiation pattern.
On 14th September 2015, a transient gravitational wave (GW150914) was detected by the two LIGO detectors at Hanford and Livingston from the coalescence of a binary black hole system located at a distance of about 400 Mpc. We point out that GW150914 e
xperienced a Shapiro delay due to the gravitational potential of the mass distribution along the line of sight of about 1800 days. Also, the near-simultaneous arrival of gravitons over a frequency range of about 100 Hz within a 0.2 second window allows us to constrain any violations of Shapiro delay and Einsteins equivalence principle between the gravitons at different frequencies. From the calculated Shapiro delay and the observed duration of the signal, frequency-dependent violations of the equivalence principle for gravitons are constrained to an accuracy of $mathcal{O}(10^{-9})$
Pulsar timing has enabled some of the strongest tests of fundamental physics. Central to the technique is the assumption that the detected radio pulses can be used to accurately measure the rotation of the pulsar. Here we report on a broad-band varia
tion in the pulse profile of the millisecond pulsar J1643-1224. A new component of emission suddenly appears in the pulse profile, decays over 4 months, and results in a permanently modified pulse shape. Profile variations such as these may be the origin of timing noise observed in other millisecond pulsars. The sensitivity of pulsar-timing observations to gravitational radiation can be increased by accounting for this variability.
We present a global kinetic plasma simulation of an axisymmetric pulsar magnetosphere with self-consistent $e^pm$ pair production. We use the particle-in-cell method and log-spherical coordinates with a grid size $4096times 4096$. This allows us to a
chieve a high voltage induced by the pulsar rotation and investigate pair creation in a young pulsar far from the death line. We find the following. (1) The energy release and $e^pm$ creation are strongly concentrated in the thin, Y-shaped current sheet, with a peak localized in a small volume at the Y-point. (2) The Y-point is shifted inward from the light cylinder by $sim 15%$, and breathes with a small amplitude. (3) The dense $e^pm$ cloud at the Y-point is in ultra-relativistic rotation, which we call super-rotation, because it exceeds co-rotation with the star. The cloud receives angular momentum flowing from the star along the poloidal magnetic lines. (4) Gamma-ray emission peaks at the Y-point and is collimated in the azimuthal direction, tangent to the Y-point circle. (5) The separatrix current sheet between the closed magnetosphere and the open magnetic field lines is sustained by the electron backflow from the Y-point cloud. Its thickness is self-regulated to marginal charge starvation. (6) Only a small fraction of dissipation occurs in the separatrix inward of the Y-point. A much higher power is released in the equatorial plane, especially at the Y-point where the created dense $e^pm$ plasma is spun up and intermittently ejected through the nozzle between the two open magnetic fluxes.
Current closure in the pulsar magnetosphere holds the key to its structure. We must determine not only the global electric circuit, but also the source of its electric charge carriers. We address this issue with the minimum number of assumptions: a)
The magnetosphere is everywhere ideal and force-free, except above the polar cap and in some finite part of the current sheet; and b) pairs are produced above the polar cap with multiplicity kappa. We show that a thin region of width delta ~ r_pc/2 kappa << r_pc along the rim of the polar cap provides all the charges that are needed in the equatorial and separatrix electric current sheet. These charges are transferred to the current sheet in a narrow dissipation zone just outside the magnetospheric Y-point. The maximum accelerating potential in this region is equal to the potential drop in the thin polar cap rim, which is approximately equal to 1/kappa times the potential drop from the center to the edge of the polar cap. The dissipated electromagnetic energy is approximately equal to 0.5/kappa times the total pulsar spindown energy loss. Our framework allows to calculate the high energy emission in terms of the pair multiplicity.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
