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SUMMARY:Polarization of synchrotron radiation from blazar jets
DTSTART;VALUE=DATE-TIME:20260507T121500Z
DTEND;VALUE=DATE-TIME:20260507T131500Z
DTSTAMP;VALUE=DATE-TIME:20260514T172300Z
UID:indico-event-961@indico.gssi.it
DESCRIPTION:Speakers: Filippo Bolis (University of Insubria & INAF)\n\nMul
 tiwavelength polarimetry has become a key tool for probing blazar jet phys
 ics\, especially with the launch of the Imaging X-ray Polarimetry Explorer
  (IXPE). I will discuss the polarization properties of High-Synchrotron Pe
 aked (HSP) blazars\, where both optical and X-ray emission arise from sync
 hrotron radiation produced by non-thermal electrons. I will show that\, re
 gardless of jet magnetization and particle acceleration mechanism\, the po
 larization degree (Pi) depends strongly on the spectral slope of the emitt
 ing electrons\, whereas the Electric Vector Position Angle (EVPA) is nearl
 y constant. I will present an axisymmetric\, stationary model of Poynting-
 dominated jets where the electromagnetic fields are fully ordered (i.e.\, 
 non-turbulent). The electromagnetic fields are determined by the jet shape
 \, which in turn depends on the pressure profile of the external confining
  medium. When the jet shape is quasi-parabolic\, the X-ray polarization de
 gree is much higher than the optical one (Pi_X/Pi_O > 2)\, whereas the EVP
 A is weakly dependent on the observed frequency. These results compare ver
 y well with observations of HSP blazars. Thus\, current IXPE data are less
  sensitive to the specific particle acceleration process than previously t
 hought. I will then discuss polarization variability using a geometric and
  deterministic model in which off-axis\, compact emitting features (i.e.\,
  blobs) propagate along the jet with the local flow velocity. The dynamics
  of the blobs is determined by jet electromagnetic fields\, which are calc
 ulated self-consistently using the analytical jet model described above. I
  will show that polarization variability is not universal and depends on t
 he initial conditions of the blobs and on the geometry of the jet\, allowi
 ng both smooth and irregular changes in the polarization degree and EVPA. 
 My results show that constraining the particle acceleration mechanism from
  multifrequency polarimetry is extremely challenging.\n\nhttps://indico.gs
 si.it/event/961/
LOCATION:Zenith Building (GSSI)
URL:https://indico.gssi.it/event/961/
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