China
Africa
Explore chapters and articles related to this topic
Nucleosynthesis, Cosmic Radiation, and the Universe
Published in Ivan G. Draganić, Zorica D. Draganić, Jean-Pierre Adloff, Radiation and Radioactivity on Earth and Beyond, 2020
Ivan G. Draganić, Zorica D. Draganić, Jean-Pierre Adloff
The remnants of supernovas are the stars known as pulsars, or pulsating stars. These are rapidly spinning bodies which emit pulses of energy in the radiowave regions of the electromagnetic spectrum. The pulses are perceived regularly like signals from a lighthouse; for example, the remnant of the “Chinese” supernova twinkles 30 times per second.
Sources of Radiation
Published in Douglas S. McGregor, J. Kenneth Shultis, Radiation Detection, 2020
Douglas S. McGregor, J. Kenneth Shultis
A neutron star produced by a supernova explosion that spins with a period of less than a few seconds is called a pulsar. Because pulsars have very strong corotating magnetic fields (>1012 G), a strong electric field is induced, which in turns accelerates charged particles.
Radio Emission from Stellar Objects
Published in Ronald L. Snell, Stanley E. Kurtz, Jonathan M. Marr, Fundamentals of Radio Astronomy, 2019
Ronald L. Snell, Stanley E. Kurtz, Jonathan M. Marr
The model of a pulsar is a rapidly rotating neutron star, whose magnetic field axis is mis-aligned with its rotation axis. Radiation is emitted along the magnetic axis of the star, in the form of a “lighthouse” beam, Pulsars!lighthouse model extending outward from the magnetic poles. The radiation mechanism responsible for this emission is discussed in Section 7.4.2. A pulsar does not ‘pulse’ in the sense of turning ‘on’ and ‘off’. Rather, as its radio beam sweeps out a path on the sky, if the beam periodically points toward Earth, we detect a pulse of emission as the beam sweeps by; see Figure 7.10. There are expected to be many more pulsars in existence than we detect, but their orientation is such that their emission beams never sweep over the Earth, and so we do not see them.
Light, the universe and everything – 12 Herculean tasks for quantum cowboys and black diamond skiers
Published in Journal of Modern Optics, 2018
Girish Agarwal, Roland E. Allen, Iva Bezděková, Robert W. Boyd, Goong Chen, Ronald Hanson, Dean L. Hawthorne, Philip Hemmer, Moochan B. Kim, Olga Kocharovskaya, David M. Lee, Sebastian K. Lidström, Suzy Lidström, Harald Losert, Helmut Maier, John W. Neuberger, Miles J. Padgett, Mark Raizen, Surjeet Rajendran, Ernst Rasel, Wolfgang P. Schleich, Marlan O. Scully, Gavriil Shchedrin, Gennady Shvets, Alexei V. Sokolov, Anatoly Svidzinsky, Ronald L. Walsworth, Rainer Weiss, Frank Wilczek, Alan E. Willner, Eli Yablonovitch, Nikolay Zheludev
Binary neutron star systems were known to exist after the major discovery by Hulse and Taylor of the observation of the radio pulses emitted by a binary pulsar system. The system gave the first measurement of the energy carried away by gravitational waves, thereby settling the issue of the reality of gravitational waves. It also provided the first firm evidence for a source that might be observed by a gravitational wave detector; the coalescence of a binary neutron star system into a black hole. These are also possible models for short gamma-ray bursts which are detected at a rate of a few per month from all over the universe. We had expected to measure the gravitational waves from them as our first likely detections. To date we still have not detected any. [After this paper was written and submitted for publication, LIGO and Virgo announced the observation of a dramatic neutron star merger, as well as additional black hole mergers.]
Nonlinear whistler wave turbulence in pulsar wind nebula: FDTD simulations
Published in Waves in Random and Complex Media, 2023
Asif Shah, Saeed Ur Rehman, Q. Haque
Pulsars are rotating neutron stars characterized by an extremely high density, strong magnetic fields, and emit relativistic winds comprising of matter (electrons) and antimatter (positrons) particles [1,2]. When these winds interact with interstellar gas, luminous pulsar wind nebulae (PWN) are generated, having an electromagnetic spectrum in synchrotron and optical range [2]. Chandra observations have tracked PWN with radio and γ-rays under shocked conditions. The PWN structure and spectral characteristics depend on angular momentum, magnetic field, beam streaming speeds and properties of the ambient matter [3]. The AMS-02 experiment has observed positron and electron fluxes in PWN [4]. The interaction of PWN and reverse shock leads to the coexistence of thermal and nonthermal fluids [5]. It has been suggested that radio emissions from PWN are due to instantly accelerated electrons [6]. Resonant cyclotron absorption is thought to be an appropriate model for plasma acceleration in PWN [7]. Whistler waves are ubiquitous in space, astrophysical, and laboratory plasma systems and are thought to play a crucial part in plasma heating. Therefore, a large literature in the past several decades has explored different aspects of whistler waves. The whistler waves dissipate PWN energy [8]. Dispersive whistlers identify the magnetic reconnection rates [9]. Whistler mode evolves into transients in the presence of adiabatic electrons [10]. Satellites have simultaneously seen whistler waves at frequencies lower than the electron cyclotron frequency and anisotropic distributions of particles [11]. The production phenomena of whistler turbulence is useful for understanding intense electromagnetic fluctuations [12]. Recently, it is reported that whistler wave nonlinear steepening takes place very quickly [13]. Electron whistler mode triggers phase space diffusion and rapid pitch angle scattering [14]. The damping effects lead to spectral index modifications for whistler wave [15]. The particle beams act as a source of whistlers [16]. Landau resonance involves the mutual interactions of electrons with whistlers [17]. Whistler wave spectrum is closely associated with energy cascade during turbulence [18]. Recently, a variety of models have been employed to explore the nonlinear dynamics of oblique whistler waves [19–31]. But the nonlinear dynamics of whistler wave in PWN in the presence of counter streaming positron and electron beams is yet not studied in the literature. Therefore, this study is focused on the nonlinear dynamics of whistler wave in PWN. This study applies finite difference time domain (FDTD) simulation scheme which incorporates feedback between whistler wave, positron, and electron beams. The paper is organized as follows: Section 2 provides the basic set of fluid equations. The linear equations are presented in Section 3. The FDTD algorithm for nonlinear whistler waves in PWN is described in Section 4. The simulation results are discussed in Section 5. Section 6 is devoted to the summary.