On the nature of Coherent pulsar

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On the nature of Coherent pulsar radio emission
Dipanjan Mitra (NCRA, India Pune)? Janusz Gil ,
George Melikidze (Uni. Of Zielona Gora)?
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A bright Single pulse from the GMRT
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A bright single pulse from GMRT
The Position angle Of this highly
polarized Pulse closely follow The average PA
Traverse (or RVM)
(Mitra, Gil, Melikidze 2009)?
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Collection ofSingle pulses from 9 more pulsars
These highly polarised pulses are free
from depolarization effects like overlapping
emission or orthogonal mode jumps
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High linearly polarized single pulse with several
subpulses Follows the average PA or RVM
PSR B192910
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Cases where PA dont follow the average PA or RVM
In several cases where the linear polarization
is not very high, the single pulse PA shows
deviations from the RVM by several degrees.
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The pulsar emission problem

• Radio Emission arises from the region where the
  magnetic field is dipolar (RVM)
• Coherent mechanisms are maser type or coherent
  curvature radiation
• Can we distinguish between the two mechanism
  observationally ? (using the high quality
  polarimetry)

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Expected PA variation due to maser and curvature
radiation
Curvature
Maser
PA under the subpulse Should follow the RVM (as
observed)
PA under the subpulse Should show fast swings
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Curvature radiation (in Vacuum)?
SINGLE PARTICLE PICTURE
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Curvature Radiation in Plasma
Ordinary wave interacts With the plasma and
gets damped
Extraordinary wave can Travel freely
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Extraordinary waves from vela
This suggest that the electric vector is
perpendicular to the magnetic field planes, which
is the extraordinary mode (Dong et al. )
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Summary

• The bright highly polarized single pulses is
  devoid of
• any depolarization making it ideal for
  investigating the
• basic emission mechanism.
• In these highly linearly polarized sub-pulses
  the PA
• follow the RVM, seen for a sample of 10 pulsars
• This behavior is a natural property of
  curvature
• radiation, and cannot be reproduced by maser
• mechanism.

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Thank you!
(observations presented here are done using the
phased array Mode of the GMRT)