Subjects: Astronomy >> Astrophysics submitted time 2024-01-16
Abstract：
The pulsar radio emission mechanism remains an enigma over half a century.
A successful radiation process requires not only to explain the coherency, but also
microstructures, characteristic frequency of emission, and the “death line" problem, etc.
These challenge both the long standing gap models and recent models of magnetic reconnection
with emission based on open field lines.
This article points out that each intermittent plasma ejection from Y-point,
the boundary of closed zone intersecting the equatorial plane,
near the light cylinder of pulsar magnetosphere can
stretch a bundle of closed field lines significantly. Corresponding magnetic pressure imposed on the trapped plasma provides ideal site of
magnetic reconnection and hence generating pairs and Alfven wave near light cylinder.
The resultant marginal stable instability is expected for coherent curvature emission. This not only interprets above problems in a simple and unified way, but also offers hints to the behavior of Rotating Radio Transients (RRATs) and Fast Radio Bursts (FRBs).
Peer Review Status:
Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Abstract： Stochastic gravitational wave background (SGWB) is a promising tool to probe the very early universe where the standard model of particle physics and cosmology are connected closely. As a possible component of SGWB, gravitational waves (GW) from bubble collisions during the first order cosmological phase transitions deserve comprehensive analyses. In 2017, Ryusuke Jinno and Masahiro Takimoto proposed an elegant analysis approach to derive the analytical expressions of energy spectra of GW from bubble collisions in Minkowski spacetime avoiding large-scale numerical simulations for the first time[26]. However, they neglect the expansion of the universe and regard the duration of phase transitions as infinity in their derivation which could deviate their estimations from true values. For these two reasons, we give a new expression of GW spectra by adopting their method, switching spacetime background to FLRW spacetime, and considering a finite duration of phase transitions. By denoting $\sigma$ as the fraction of the speed of phase transitions to the expansion speed of the universe, we find when $\sigma$ is around $\mathcal{O}(10)$, the maxima of estimated GW energy spectra drop by around 1 order of magnitude than the results given by their previous work. Even when $\sigma=100$, the maximum of GW energy spectrum is only $65\%$ of their previous estimation. Such a significant decrease may bring about new challenges for the detectability of GW from bubble collisions. Luckily, by comparing new spectra with PLI (\textit{power-law integrated}) sensitivity curves of GW detectors, we find that the detection prospect for GW from bubble collisions is still promising for DECIGO, BBO, LISA, and TianQin in the foreseeable future.
Peer Review Status:Awaiting Review
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