Probing Magnetic Fields and Acceleration Mechanisms in Blazar Jets with X-ray Polarimetry

TL;DR

This paper reviews how X-ray polarimetry can reveal magnetic field structures and particle acceleration processes in blazar jets, focusing on high synchrotron peak blazars and upcoming observational prospects.

Contribution

It compares models of shock acceleration and magnetic reconnection in predicting X-ray polarization in blazars, guiding future observations with IXPE.

Findings

Magnetic reconnection models predict distinct polarization signatures from shock models.

Simulations suggest X-ray polarimetry can differentiate acceleration mechanisms.

Upcoming IXPE observations will test these theoretical predictions.

Abstract

X-ray polarimetry promises us an unprecedented look at the structure of magnetic fields and on the processes at the base of acceleration of particles up to ultrarelativistic energies in relativistic jets. Crucial pieces of information are expected from observations of blazars (that are characterized by the presence of a jet pointing close to the Earth), in particular of the subclass defined by a synchrotron emission extending to the X-ray band (so-called high synchrotron peak blazars, HSP). In this review, I give an account of some of the models and numerical simulations developed to predict the polarimetric properties of HSP at high energy, contrasting the predictions of scenarios assuming particle acceleration at shock fronts with those that are based on magnetic reconnection, and I discuss the prospects for the observations of the upcoming Imaging X-ray Polarimetry Explorer (IXPE) satellite.