The observability of plasmoid-powered $\gamma$-ray flares with the Fermi Large Area Telescope

TL;DR

This paper demonstrates that magnetic reconnection in blazar jets can produce gamma-ray flares with variability patterns observable by Fermi, supporting reconnection as a key mechanism behind rapid gamma-ray variability.

Contribution

It provides realistic gamma-ray light curves from magnetic reconnection simulations and compares them with observations, highlighting the role of plasmoids and jet orientation in variability.

Findings

Magnetic reconnection can produce flux levels similar to observed gamma-ray flares.

Fast plasmoids near the line of sight can explain minute-scale variability.

Reconnection events are consistent with observed variability patterns in FSRQs.

Abstract

The exact mechanism for the production of fast $\gamma$-ray variability in blazars remains debated. Magnetic reconnection, in which plasmoids filled with relativistic particles and magnetic fields are formed, is a viable candidate to explain the broadband electromagnetic spectrum and variability of these objects. Using state-of-the-art magnetic reconnection simulations, we generate realistic $\gamma$-ray light curves that would be observed with the Fermi Large Area Telescope. A comparison with observed $\gamma$-ray flares from flat spectrum radio quasars (FSRQs) reveals that magnetic reconnection events lead to comparable flux levels and variability patterns, in particular when the reconnection layer is slightly misaligned with the line of sight. Emission from fast plasmoids moving close to the line of sight could explain fast variability on the time scales of minutes for which evidence has been found in observations of FSRQs. Our results motivate improvements in existing radiative transfer simulations as well as dedicated searches for fast variability as evidence for magnetic reconnection events.