| 番号 | R6-6 / IPMU/ILANCE/ICRR joint seminar |
| 日時 | 2024年10月11日(金) 15:00- (TBC) |
| 場所 | ICRR 6F large seminar room (601) Zoom: https://u-tokyo-ac-jp.zoom.us/j/89107721938?pwd=crFZhI3h93DTCavaavhBvuBzhB1feC.1 |
| 講演者 | Mahmoud Alawashra (DEZY Zeuthen, Germany) |
| タイトル | “Marginal Role of the Electrostatic Instability in the GeV-scale Cascade Flux from 1ES 0229+200” |
| 概要 | Relativistic pair beams produced in the intergalactic medium (IGM) by TeV gamma rays from blazars are expected to generate a detectable GeV-scale electromagnetic cascade, yet this cascade is absent in observations. This suppression is often attributed to weak intergalactic magnetic fields (IGMFs) deflecting electron-positron pairs out of the line of sight. Alternatively, it has been proposed that beam-plasma instabilities could drain the beams’ energy before they produce the secondary cascades. Recent studies suggest that the modification of beam distribution due to these instabilities is primarily driven by particle scattering, rather than energy loss. In this work, we quantitatively assess the impact of transfer diffusion caused by electrostatic instabilities on the arrival time of secondary gamma rays at Earth for the blazar 1ES 0229+200. We first computed the production rates of electron-positron pairs at various distances in the IGM using the Monte Carlo simulation CRPropa. We then simulated the feedback of the plasma instability on the beam, incorporating production rates and inverse-Compton cooling, to determine the modified steady state of the beam. Our findings reveal that the time delay of the GeV secondary cascade arrival due to instability broadening is on the order of a few months. This delay is insufficient to account for the missing cascade emission in observations of blazar spectra, suggesting that plasma instabilities do not significantly affect IGMF constraints. |
