This paper presents a review of recent advances in those observations of radio pulsars which are relevant to the understanding of “where” and “how” the radio signals are generated in the magnetosphere of the neutron star. These include (i) results from simultaneous multi-frequency observations, (ii) emission geometry studies of multi-component pulsars, (iii) results from drifting and nulling pulsars, (iv) constraints from single pulse statistics and (v) progress in giant pulse studies.

We briefly review observational manifestations of pulsars with giant pulse emission and consider quasi-giant pulse phenomena in other pulsars. We argue that power-law statistics give the best definition of giant pulses. Finally, we speculate as to the origin of the giant pulses and a possible link with high energy emission.

Giant pulses (GPs), occasional individual pulses with an intensity 100 times the average intensity, have been detected in four pulsars to date. Their origin is not well understood, but studies suggest a connection between the strength of magnetic field at the light cylinder Blc and the existence of GPs. Here, we report on detection of significant Large Amplitude Pulses (LAPs) in two more pulsars with high values of Blc, PSRs J0218+4232 and B1957+20, observed using Giant Meterwave Radio Telescope (GMRT).

Extremely short and powerful subpulses were recently detected within the giant radio pulses from the Crab pulsar. We argue that these are consistent with beaming due to the curvature of field lines, and thus with coherent curvature radiation. We also demonstrate that the observed fluxes are consistent with the emission of charged relativistic solitons, generated by means of modulational instability of the Langmuir turbulence associated with sparking discharge of the pulsar's polar gap.

We have detected an enhancement in the optical emission from the Crab pulsar which is correlated with the presence of the giant radio pulses. Coincident optical pulses were found to be on average 3% brighter than those coincident with normal radio pulses. This enhancement, combined with the lack of any other pulse profile changes, indicates that both the giant radio pulses and the increased optical emission are most likely linked to an increase in the electron-positron plasma density.

We present high quality polarimetric observations with the Effelsberg radio telescope of the Crab pulsar at 8.35 GHz using a new sensitive receiver with a very large bandwidth. We present our observations and discuss them in the context of the conclusions reached by Moffett & Hankins (1999) about the geometry and the origin of the various pulse components.

The Crab pulsar (PSR B0531+21) has been observed with the EPIC-pn camera on board the ESA XMM-Newton satellite. The high time resolution of the EPIC camera (7 μs) in its special Burst mode in combination with the huge effective area and the high quantum efficiency of the pn-CCD allows phase resolved spectroscopy of good quality over the energy range 0.6–8.5 keV. We performed phase resolved spectroscopy of the modulated flux of the Crab pulsar and found a significant hardening of the photon index in the inter-pulse region. Also the second pulse is harder in index by 0.1 than the first pulse.

Pulse-shape changes correlating with flux have been shown to exist in the Vela pulsar's radio emission (Krishnamohan & Downs 1983). The aim of this work was to look for correlations between radio and X-ray flux in Vela on a pulse-by-pulse basis. We found that Vela emits significantly more X-rays during radio pulses with strong flux than during weak radio flux pulses, which indicates that the mechanisms creating the Vela pulsar's X-ray and radio emission must be related.

We have obtained simultaneous observations of single pulses from the bright pulsars B0329+54 and B1133+16 at two frequencies in full polarization and a total of four frequencies in total power only. Here is a summary of our fantastic results!

Spectra of several pulsars with turnover at unusually high frequencies ∼ 1 GHz are presented. These are relatively young pulsars with DM typically larger than for pulsars showing a low-frequency turnover.

By developing a new technique, 13 drifting subpulses have been revealed across one period in PSR B0826–34. The variation of drift rate when drifting subpulses drift through different longitude regions are noticed. A weak emission mode was detected during its apparent null.

The beamed emission by relativistic sources moving along the magnetic dipolar field lines occurs in the direction of tangents to the field lines. To receive such a beamed radiation, the line of sight must align with the tangent within the beaming angle 1/γ, where γ is the particle Lorentz factor. By solving the viewing geometry, in an inclined and rotating dipole magnetic field, we show that at any given pulse phase the observer can receive the radiation only from specific altitudes. We find that the outer conal emission is received from higher altitudes than the inner conal components including the core. At any pulse phase, low frequency emission comes from the higher altitudes than higher-frequency emission. As an application of our model, we have used it to explain the emission heights of conal components in PSR B0329+54.

We report some results based on 150 MHz observations of the millisecond pulsar J0437–4715 carried out using the Mauritius Radio Telescope (MRT). For the single pulse properties we also consider 327 MHz data from the Ooty Radio Telescope.

High-energy and radio emission mechanisms for pulsars are reviewed. The source region for high energy emission remains uncertain. Two preferred radio emission mechanism are identified. Some difficulties may be resolved by appealing to nonstationary pair creation distributed widely in height.

I review the theoretical understanding of the global structure of pulsar magnetospheres concentrating on recent progress in force-free electrodynamics and first-principles simulations of magnetospheres.

It is argued that the polar gap and flux tube in the pulsar magnetosphere act as a resonant cavity/waveguide system which is excited by oscillations in the primary beam current and accelerating potential. The modes will be converted, probably scattered, to produce radio beams in the frequency range of those observed.

A model for the origin of giant radio pulses is suggested. Radio emission is generated by the electric discharge taking place due to the magnetic reconnection of field lines connecting the opposite magnetic poles. The reconnection occurs in the region of the light cylinder near the zero line of the magnetic field. The coherent mechanism of radiation is pure maser amplification of Alfvén waves. The radiated frequencies are found.

We present high-energy light curves and polarization properties of pulsars calculated within the recently proposed two-pole caustic model. The results are compared with the optical data for the Crab pulsar and with predictions of other high-energy pulsar models: the polar cap model, and the outer gap model.

We present a relativistic model of pulsar radio emission by plasma accelerated along the rotating magnetic field lines projected on to a 2D plane perpendicular to the rotation axis. We have derived the expression for the trajectory of a particle, and estimated the spectrum of radio emission by the plasma bunches. We used the parameters given by Peyman & Gangadhara (2002). The analytical expressions for the Stokes parameters are obtained, and their values compared with the observed profiles. The one sense of circular polarization, observed in many pulsars, can be explained in light of our model.

General features of polarization transfer in the plasma of pulsar magnetospheres are outlined. A technique of plasma density diagnostics based on observed polarization profiles of radio pulses is developed. For the first time, it appears possible to obtain the profiles of the plasma density across the open field line tube from observations. The multiplicities derived are compatible with those predicted by modern theories of pair cascade and show a perfect exponential decrease towards the tube edge. Implications of the results are briefly discussed.