【6.21; Seminar】2024年粒子天体物理重点实验室系列学术报告 #30：Gamma-Ray Burst afterglows and Their Implications to Particle acceleration at Relativistic Shocks

时间/Time: 6月21日上午10:00/Friday, June 21st at 10:00 am

地点/Location: 多学科楼226会议室/Multidisciplinary Building 226

报告人/Speaker: Dr. Zhiqiu Huang（SISSA）

题目/Title: Gamma-Ray Burst afterglows and Their Implications to Particle acceleration at Relativistic Shocks

主持人/Host: 席绍强/Shaoqiang XI

摘要/Abstract:

abstract: Recent TeV detections of gamma-ray burst afterglows offer new insights into particle acceleration at relativistic shocks. Kinetic simulations have improved our understanding of shock microphysics, enhancing models of particle acceleration relevant to afterglows. We explore scenarios for determining the maximum achievable energy, comparing our findings with data from the H.E.S.S. source, GRB 190829A. This comparison reveals a tension between observations and theoretical expectations. Motivated by this, we developed a Monte Carlo code to revisit acceleration theory for relativistic shocks in uniform and non-uniform magnetic field configurations. In uniform fields, we demonstrate that acceleration requires only strong scattering on one side of the shock. Analytic solutions confirm this conclusion. For non-uniform fields, we consider a cylindrical magnetic-field structure typical of astrophysical jets. We find that curvature drifts enable repeated shock-crossings for particles of favourable charge, and neglecting losses extends the maximum energy to the system's confinement limit. These results challenge the misconception that ultra-relativistic shocks cannot serve as effective accelerators, offering a fresh perspective on relativistic shock acceleration. The findings suggest new features on maximum achievable energy and spectral index, indicating the need to revisit current knowledge on relativistic shocks. This could open promising avenues for producing ultra-high energy cosmic rays.

个人简介/Biography：

Zhiqiu Huang obtained PhD degree at Max-Planck-Institut für Kernphysik in Heidelberg, Germany and did researches on gamma-ray bursts and particle acceleration at relativistic shocks. He has already received a postdoc fellowship in SISSA (Trieste, Italy) since June 2024 and will continue his studies on gamma-ray bursts.