Pulsar pair-production theories imply that the plasma leaves the source already flowing relativistically. Such winds might also have relativistic injection temperatures. MHD models of relativistic pulsar winds were considered, and it was shown that in this case cold wind theories can be misleading.

On the other hand, due to synchrotron radiation losses, the temperature of collisionless, strongly magnetized, relativistic plasma quickly becomes anisotropic. In this case the plasma pressure is no longer a scalar and to describe the properties of stellar wind a hydrodynamical model of relativistic plasma with the anisotropic temperature distribution should be developed.

The structure of the pulsar magnetosphere is studied in terms of a DC-circuit analogy. We find (1) the pulsar's death results from the ‘disappearance’ of operating points of this DC-circuit, (2) the outer gap is necessary, (3) the kinetic energy flux of the pair plasma wind and the electromagnetic flux are comparable, and (4) for rapid pulsars only two types of structure (a wind dominated one and an outer-gap dominated one) are possible.

The aim of this work (Fitzpatrick and Mestel 1988a, Fitzpatrick and Mestel 1988b) is to elucidate how a neutron star with a dipolar magnetic field of axis k and an instantaneous angular velocity αk would spin down, within the framework of classical physics. The rotation of the highly conducting stellar crust generates differences of electric potential between field lines. An electron current flows from points of lower to higher potential via a dissipation domain located largely beyond the light-cylinder. Electrons leave the star's polar regions as a subrelativistic stream, flowing nearly along the lines of the poloidal field Bp, picking up energy from the electric force and angular momentum from the moment about k of the magnetic force.

A self-consistent model of the pulsar magnetosphere is presented. The principal point of the model is its use of the massless approximation. In this approximation electrons and positrons are considered as massless particles, and the pulsar magnetosphere consists of regions of two types: (1) accelerating regions (A-regions) filled with particles moving with the speed of light [dynamical phase (DP)], (2) capture regions (C-regions) which, besides the DP, contain static phase (SP), i.e. captured particles resting at some coordinate system.

The existence of massless charged particles (electrons and positrons) in the description of the pulsar magnetosphere description leads to the appearance of two phases for each species. In the dynamical phase (DP), the particles move like photons with the speed of light. The static phase (SP), in which the massless particles move with a speed less than that of light, can exist only inside the capture region (C-region). Inside the C-region (E, H) = 0 or E2 < H2, and the Lorentz force acting upon the particles of SP vanishes. Inside the accelerating region (A-region), where (E,H) ≠ 0 or E2 ≥ H2 , only the DP can exist.

It is shown that pulsars with long periods differ systematically from those with short periods. We conclude that generation of emission in the second group occurs in a very thin layer (near the light cylinder). Relativistic effects may be significant here. Some properties of core emission can be explained by Melrose's mechanism.

The magnetosphere of a rapidly rotating, strongly magnetized neutron star with aligned magnetic and rotational axes (parallel rotator) is modelled numerically. Including the radiation of the particles accelerated to relativistic energies as an efficient damping mechanism, we obtain a quasi-stationary self-consistent solution to this classical problem. The numerical simulation,which was started from the well-known vacuum solution, yields a global magnetospheric structure that can be characterized by two regions of oppositely charged particles, which eventually produce a relativistic pulsar wind, separated by a vacuum gap of considerable extent.

A magnet rotating in vacuo with its vector of angular velocity ω perpendicular to its vector of magnetic dipole moment μ is able to act as a particle accelerator. The dynamic features involved may be relevant for the understanding of rotating magnetized neutron stars as cosmic accelerators (Thielheim 1989) and may be useful for the designing of new mechanisms for accelerating devices.

Pulsars are generally identified with rotating, magnetized neutron stars. According to Goldreich and Julian (1969), an induced electric field creates the electric current which flows out of the magnetic poles and fills the magnetosphere with plasma. The current flows along the open magnetic field lines and returns along the boundary between the closed and open parts of the magnetosphere (Scharlemann and Wagoner 1973). The boundary shape is determined by the equilibrium condition for the current sheet.

We present a possible emission mechanism based on the idea of current sheets in magnetohydrodynamice. The current sheets are formed close to the light cylinder due to a relativistic effect involving partly frozen-in particles. We estimate that the energy emitted by the current sheets fits the observations fairly well.

The phenomenon of collective spontaneous annihilation of a magnetized electron-positron plasma is predicted. Like the superradiance in systems with discrete energy spectra, collective annihilation leads to the generation of powerful coherent radiation with the rate of this process considerably exceeding the spontaneous annihilation and collisional relaxation rates.

An exact expression is given for the orbit of a charged particle accelerated by a non-propagating electrostatic wave. The corresponding current is obtained, for untrapped particles, as an expansion in Bessel functions, and a Lorentz transform allows us to treat the case of a propagating wave. An appropriate form for the absorption coefficient is derived, and an interesting angular and frequency dependence is revealed when the propagating wave is superluminal. Finally, the possible application to pulsars, particularly in explaining the multicomponent pulse profiles, is discussed briefly.

Results and problems of the model for Josephson pulsars are summarized and discussed. In this model coherent radio emission is generated in the mantle of a neutron star by the Josephson effect. The matter from the mantle may flow along the magnetic field through cracks in the crust, forming a magnetized plasma wave guide. Radio emission propagates in this plasma flow as polarized normal wave-guide modes. A line-of-sight section gives the observed polarized structure of pulses. In some cases polarized X- and γ-ray emission may be generated in this flow in or over cracks. Such an approach allows us to avoid the typical problems and is in agreement with the main observational results.

A system of pulsar profile classification is used as a starting point to study the emission characteristics of pulsars. Two types or mechanisms of pulsar radiation are identified which combine geometrically to produce five major species of profile. The core emission, which forms a pencil beam of radiation, is apparently produced close to the stellar surface throughout the entire polar cap region by low γ particles. The conal emission, which consists of a hollow conical beam, then seems to be emitted at heights of 10 to 20 stellar radii by currents of high γ particles travelling along some of the most peripheral of the “open” field lines.

From a study of the intensity and polarization data of a large number of pulsars, Lyne and Manchester (1988) showed that pulsar beams are essentially circular in cross-section, and confirmed that pulse widths are inversely correlated with pulse period. Using a homogeneous sub-sample of 80 “cone-dominated” pulsars from their compilation, we find an inverse correlation between pulse width and radio luminosity. We conclude that pulsar beams become wider at lower luminosities. This effect is expected since pulse profiles are observed to fall-off smoothly at their edges, thus showing that pulsar beams do not have sharp edges. If beams do become wider at lower luminosities, then some of the dispersion in the observed pulsar luminosities is not intrinsic, but merely due to varying offsets of the line-of-sight from the beam center. In view of this, one should re-examine the usual procedure of independently modeling the luminosity and beaming in pulsar statistics calculations. We expect that a self-consistent approach that includes luminosity and beaming within a single model will indicate that the “effective” beam size for statistical calculations is significantly larger (by a factor ~2) than the size one usually estimates based on the observed sample of high-luminosity pulsars.

A general feature of many models of the pulsar emission mechanism is that radiation of different frequencies is produced at different altitudes above the polar cap. The broadening of pulse components and increasing separation between components at low frequency is in general agreement with these theories. We review the available average profile and pulsar timing observations and discuss the implications for theories of radius-to-frequency mapping.

On the basis of pulse profiles in a limited interval of wavelength for ~260 pulsars, the dependence of the shape and width of the pulsar radiation pattern on pulsar period is investigated. The relative pulse duration is compared with the ratio of numbers of single and multicomponent pulsars. It is shown that the simple circular hollow cone model does not agree with observational data. Preliminary estimates show that the young pulsars (with short periods) have an elliptical pattern which at long periods becomes circular.

Flux density measurements of four recycled pulsars, PSR 1620-26, PSR 1821-24, PSR 1855+09, and PSR 1937+21, have been made to determine their spectral indices in the range between 425 MHz to 3 GHz. The four objects are shown to have indices that range from –1.3 to –2.6. The luminosities of these four pulsars are spread over nearly three orders of magnitude. An analytic pulse component model is developed for each object. Individual components are allowed to have different spectral indices and hence different component ratios as a function of frequency. Component separations are evaluated as a function of frequency. The analytic models are used to determine dispersion measures with a precision better than 0.01 pc cm–3 for each object. The intrinsic pulse widths of each of these objects is less than ~4 percent of their respective pulse periods.

Using values of the frequencies vc for the high-frequency cutoffs of 31 pulsars obtained by other authors, we confirmed the relationship (obtained by us earlier) between vc and the period of pulsar P. The plot vc(χ) was drawn where χ is the relative angular distance between the line of sight and the center of the radiation cone. It is shown that pulsars with long periods cluster in the lower left corner of this diagram. Some geometrical and physical reasons causing high-frequency cutoffs are analyzed. The results can be explained by a model of thin plasma sheets. The interaction of these sheets causes generation of Langmuir waves at distances ~108 cm from the center of the neutron star. Pulsars without high-frequency cutoffs can be described by a model in which vc is very near the frequency of maximum in the spectra of these pulsars.

An analysis has been made of the connection of characteristic frequencies and spectral indices with the following parameters of pulsars: P, Ṗ, T, L400, B, and χ. It is shown that a number of pulsar spectra apparently demonstrate the presence of two emission regions at a short distance between levels in the magnetosphere of pulsars, where the effects of the low-frequency turnover (LFT) and the high frequency cutoff (HFC) take place.