arXiv subjects

Wei-Cheng Long

Publications and source records attributed to Wei-Cheng Long.

3 recordsLinked to original sources

arXiv2026

High-energy neutrino signatures of embedded GRB jets in AGN disks: a dynamic jet-propagation framework

Relativistic jets embedded in active galactic nucleus (AGN) accretion disks are promising high-energy neutrino sources, but their emission is often estimated from a single representative jet state. We develop a time-dependent framework that follows jet-head propagation, evolving reverse-shock conditions, and particle cooling until the jet chokes or breaks out, and apply it to the SG and TQM disk models. For the representative choked cases, neutrino emission is dominated by the high-dissipation phase near jet stalling, allowing a stalling-state approximation to reproduce the trajectory-integrated, detector-weighted event yield within approximately $14\%$. In breakout cases, however, rapid jet-head acceleration across steep disk-density gradients suppresses reverse-shock dissipation and can cause single-state estimates to overpredict the fluence, even after accounting for the available energy budget. Full trajectory integration also reshapes the high-energy spectral tail and produces distinct detectability patterns across SMBH mass and disk radius for the two disk models. Some lower-density outer-disk cases develop harder tails extending into the 10--100 PeV range, motivating future ultra-high-energy neutrino searches. Resolving jet propagation dynamics is therefore indispensable for evaluating embedded transients across AGN disk environments and avoiding systematic biases in multi-messenger modeling.

astro-ph.HE↗

arXiv2024

Probing solar modulation analytic models with cosmic ray periodic spectra

The AMS02 experiment has published the periodic spectra of proton, helium and helium isotopes across the majority of the 24 solar cycle. These precise data exhibit temporal structures that correlate with solar modulation. In this study, we utilize these data to probe three analytic solar modulation models, including the force-field approximation, the convection-diffusion model and the extended force-field approximation with a drift effect. We adopt a method that eliminates the influence of interstellar cosmic ray spectra, and use the Earth-observed spectra at time $t_1$ to predict those at time $t_2$. In order to explore the rigidity-dependence of solar modulation models, we substitute the conventional potential parameter $ϕ$ with a modified parameter $ϕ'=\frac{R}{ k_2(R)}ϕ$ for our analysis. Combining with the $χ^2$ minimization method, the best-fit modulation parameter $ϕ'$ can be evaluated. First, we test the validity of a rigidity-independent $ϕ'$ and find that both the force-field approximation (FFA) and the extended force-field approximation (EFFA) agree well with data near the solar minimum period. However, all models significantly deviate from the data during the solar maximum. Consequently, we assume a constant $ϕ'(t_1)$ at solar minimum and calculate $Δϕ'=ϕ'(t_2)-ϕ'(t_1)$ for each rigidity bin at time $t_2$. It is found that $Δϕ'$ generally adheres to a linear-logarithm relationship with rigidity at any given time. By adopting a linear-logarithm formula of $Δϕ'$, we further discover that both the modified FFA and EFFA can reconcile the observations during solar maxima. This suggests that at solar maximum, the parameter $ϕ'$, which correlates with the diffusion pattern in the heliospheric magnetic fields, exhibits a rigidity dependence.

astro-ph.SR↗

arXiv2022

Testing the consistency of proapgation between light and heavy cosmic ray nuclei

One of the fundamental issues in cosmic ray physics is to explain the nature of cosmic ray acceleration and propagation mechanisms. Thanks to the precise cosmic ray data measured by recent space experiments, we are able to investigate the cosmic ray acceleration and propagation models more comprehensively and reliably. In this paper, we combine the secondary-to-primary ratios and the primary spectra measured by PAMELA, AMS02, ACE-CRIS and Voyager-1 to constrain the cosmic ray source and transport parameters. The study shows that the $Z>2$ data yield a medium-energy diffusion slope $δ_{2}\sim\left(0.42, 0.48\right)$ and a high-energy slope $δ_{3}\sim\left(0.22, 0.34\right)$. The $Z\leq2$ species obtain a looser constraint on $δ_{2}\sim\left(0.38, 0.47\right)$, but a tighter constraint on $δ_{3}\sim\left(0.21, 0.30\right)$. The overlaps infer that the heavy and light particles can give compatible results at medium to high energies. Besides, both the light and heavy nuclei indicate a consistent diffusion slope variation $Δδ_{H}$ around $200\sim300$~GV. At low energies, significant disagreements exist between the heavy and light elements. The B/C ratio requires a much larger diffusion slope shift $Δδ_{L}$ around 4 GV or a stronger \textit{Alfv$\acute{e}$n velocity} $v_{A}$ than the low-mass data. This indicates that the heavy and light particles may suffer different low-energy transport behaviors in Galaxy. However, better understanding on the consistency/inconsistency between the heavy and light cosmic rays relies on more precise cross-sections, better constraints on correlations in systematic errors of data, more accurate estimation on Galaxy halo size and more robust description for Solar modulation during the reversal period of HMF.

astro-ph.HE↗