A Non-Radial Oscillation Model for Radio Pulsars

In collaboration withDr. J. Christopher Clemens

University of North Carolina at Chapel Hill

Average Pulse Shapes

Lyne, A. G., & Manchester, R. N. 1988, Monthly Notices of the RAS, 234, 477

Polarization Properties

Stinebring, D. R., Cordes, J. M., Rankin, J. M., Weisberg, J. M., & Boriakoff, V. 1984, ApJS, 55, 247

Drifting Subpulses

Vacuum Gap, Drifting Spark Model

Ruderman, M. A., & Sutherland, P. G. 1975, Astrophysical Journal, 196, 51

Phase Shifts

Rapidly oscillating Ap star HR 3831

PSR 0320+39

Edwards, R. T., Stappers, B. W., & van Leeuwen, A. G. J. 2003, A&A, 401, 321

Intensity and Velocity Variations

The displacement (intensity) variations are described as:

Where are spherical coordinates aligned to the magnetic axis of the star

The velocity variations are described as:

=∂ l ,0 ,

∂sint t

= l , o ,cos t t− o

,

Intensity Variations in WDs

l = 2, m = 0 l = 1, m = 0

Polarization Geometry

Displacements and velocitiesare aligned to magnetic pole

Induced electric field (Eϕ)

due to Eϕ = v x B(0)

is orthogonal to Eθ

Result: two orthogonal electricfields

Our Model

Single Pulse Behavior

PSR 0943+10: DataThe:

Single pulses

Fourier Transform

PSR 0943+10: Dual FrequenciesTwo possibilities for a split subpulse frequency:1. Two closely spaced independent frequencies2. Combined frequency and amplitude or phase

modulation of a single frequency

PSR B0943+10Pulsational and geometrical parameters are largely independent

Conclusions and Future Work

Developed a physical model for pulsar morphology based on asteroseismological principles

Conducted quantitative fitting of model to data

Next step: fit more complex pulsar behavior, acquire data for definitive tests

Subpulse phase correlation between both magnetic poles

Subpulse frequency independent of observational radio frequency