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| Paper: |
Observational Consequences of the Partially Screened Gap |
| Volume: |
466, Electromagnetic Radiation from Pulsars and Magnetars |
| Page: |
125 |
| Authors: |
Szary, A.; Melikidze, G.; Gil, J. |
| Abstract: |
Observations of the thermal X-ray emission from old radio pulsars implicate
that the size of hot spots is much smaller then the size of the polar cap
that follows from the purely dipolar geometry of pulsar magnetic field.
Plausible explanation of this phenomena is an assumption that the magnetic
field at the stellar surface differs essentially from the purely dipolar field.
Using the conservation of the magnetic flux through the area bounded by open
magnetic field lines we can estimate the surface magnetic field as of the
order of 1014G. Based on observations that the hot spot temperature is
about a few million Kelvins the Partially Screened Gap (PSG) model was
proposed which assumes that the temperature of the actual polar cap equals to
the so called critical temperature. We discuss correlation between the
temperature and corresponding area of the thermal X-ray emission for a number
of pulsars.
We have found that depending on the conditions in a polar cap
region the gap breakdown can be caused either by the Curvature Radiation (CR)
or by the Inverse Compton Scattering (ICS). When the gap is dominated by ICS
the density of secondary plasma with Lorentz factors 102–103 is at
least an order of magnitude higher than in a CR scenario. We believe that
two different gap breakdown scenarios can explain the mode-changing
phenomenon and in particular the pulse nulling.
Measurements of the characteristic spacing between sub-pulses (P2) and
the period at which a pattern of pulses crosses the pulse window (P3)
allowed us to determine more strict conditions for avalanche pair production
in the PSG. |
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