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A model for pulsar nullings

A model for pulsar nullings. A. Kazbegi et al. 1996 A&A 309,515k. Introduction. Subpulse drift. Nulling and Phase Memory. Conclusion. 02. 01. 03. 04. Content. Introduction. Nulling phenomenon Subpulse drift Phase memory phenomenon. Model and difficulties Ruderman&Sutherland 1975

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A model for pulsar nullings

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  1. A model for pulsar nullings A. Kazbegi et al. 1996 A&A 309,515k

  2. Introduction Subpulse drift Nulling and Phase Memory Conclusion 02 01 03 04 Content

  3. Introduction • Nulling phenomenon • Subpulse drift • Phase memory phenomenon

  4. Model and difficulties Ruderman&Sutherland 1975 • drift velocity Vdr=ch/2RB • ~10-4-10-3s spark would diffuse over the whole gap • can't explain phase memory Filipenko&Radhakeishnan 1982 • Plasma column • rapid brodening of columns if Φ≠0 at different z

  5. Subpulse drift γp～3，np~1016cm-3,γt～104－105，nt~1013-1014cm-3,γb～106,nb~1011cm-3 assuming P~1s , Arons(1981)

  6. Low frequency wave mode (Volokitin et al.1985;Lominadze et al.1986) • t-wave: purely transversal electromagnetic wave • lt-wave: electrostatic-electromagnetic wave Perturbations • anlmalous Doppler-effect resonance • core type emission

  7. Cherenkov resonance • explain the cone radiation(Rankin 1983) • R~109cm (P=1s) for radio radiation • subpulse drift is in conal single profiles(Rankin 1983;1986) • growth rate

  8. Low frequency drift wave(Kazbegi A.Z. et al. 1991) • kx/kφ>>1, propagate across the magnetic field • frequence • growth rate the growth rate is rather small • ω＝Ω＋Δ • Δ>0 or <0 subpulse drift is observed

  9. Nulling and pahse memory • curvature radiation(RS vacuum gap model) • In order to produce e+-e- energy should exceed minimum lorentz factor

  10. if electic field E0//~107 CGSE and gap height h~103-104cm • γ≥γbmin, secondary particles are rapidly produced and E0// is screened - nulling • Pair formation front(PFF Model Arons et al. 1979;83;92) • Above the PFF the bulk of plasma is produced and E0// is screened • Primary particles extracted from the stellar surface is not take into account

  11. Binding energy of electrons • W~1-3keV • free particles reach γbmin before the PFF will produce pairs • positrons moving towards the stellar surface and leading electron thermoemission, brodens the primary beam distribution function

  12. large number of backstreaming positrons and more and more pairs produced lead E0// decreasing • peak of the primary beam smaller than γbmin growth rate is sensitive to γb

  13. nulling duration is depends on • the primary particles distribution function broadening time • number of events enough for closing up the gap mc2n+γ＋～mvth2nth n+～1， nth～104－105 Goldreich-Julian density 1011cm-3 need106-107 events

  14. note low frequency drift wave is excited with smallγb but the frequency is propotional toγb

  15. Hence during the nulling the drift wave continue to propagate across the magnatic field with reduced velocity • at small nulls i.e. 10P , the pahse of the pulse is "remenbered" • the smaller the null the better the pulsar window is remenbered

  16. Conclusion • Emission generated at • Doppler-effect resonance • Cherenkov resonance • Low frequency drift wave • PFF + thermoemission Screening the electric field and closing the gap

  17. 谢谢观赏

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