Three bright pulsars (B0950+08, B1133+16, and B1929+10) were observed with the 70-m radio telescope in Tidbinbilla at a frequency of 1650 MHz using the S2 Data Acquisition System which provided continuous recording of pulsar signals in two conjugate bands of B=16 MHz each. Parameters of microstructure have been analyzed using the predetection dispersion removal technique.

MSP have much more various short time-scale phenomena than ”classical” microstructure in NP. Some of them have a long life-time and are observable not only in single pulses.

We report the discovery of the longest known radio pulsar period. PSR J2144–3933, previously thought to have a period of 2.84 s, actually has a period of 8.51 s. Under the usual assumptions about the stellar equation of state, this pulsar has an average surface dipolar magnetic field strength of ~ 2.0 × 1012G. According to popular theories of the emission mechanism this pulsar should not be emitting radio waves because its long period and magnetic field strength make pair creation impossible for all reasonable magnetic field configurations. Either assumptions about the equation of state are incorrect, or the emission theories must be revised.

Recent radio observations of pulsar profiles and the present knowledge about structure of the emission region based on this profiles data are reviewed.

Observations and component structure analysis revealed that there are pulsars profiles having more than 5 components. It call into question that the commonly adopted model of emission region as the double hollow cones and a central core is applicable. Mosaic model of an emission region fit observed profiles with complex more than 5 component structure.

The height (radius) for the emission region evaluated from a dependence of a width of integrated profiles from the pulsar period is estimated as rem ≅ 1.5 × l07P0.1 cm.

A comparative analysis of the frequency dependence of the profile widths of millisecond and normal pulsars in 0.1 to 1.4 GHz frequency range indicates that the frequency dependence of a width of their profiles, is much weaker than what is typically observed for normal pulsars. This suggests that the geometry of the emission region of millisecond pulsars is unlike that of normal ones.

We study the structure of the pulsar beam using the analysis of beam radius. We indentify three emission cones in radio beams. The dependence of the beam radius on frequency is obtained.

We carried out the Gaussian fitting to the profile of PSR B1237+25 and found that six components rather than five are necessary to make a good fit. In the central part, we found that the core emission is not filled pencil beam but is a small hollow cone. This implies that the impact angle could be β < 0.5°. The “hollow core” is in agreement with Inverse Compton Scattering model of radio pulsars.

In this paper, the effects of aberration, retardation and magnetic field sweep back, which are caused by pulsar’s rapid rotation, are estimated to see their influences on the pulse shape of pulsars and geometry asymmetry of the mean pulse profile. The width of mean pulse profile is modified only slightly, but the geometry asymmetry appears and will exhibit different behaviors at different cases. The pulsars of B1451-68 and J0437-4715 are analyzed as examples.

The main results of the linear polarization measurements of pulsars done at the lowest radio frequencies 40, 60 and 103 MHz are summarized in this paper. We have analyzed 35 integrated polarization profiles and 20 statistical distribution displays and compared them with published high frequency results.

Pulsars were discovered at 81.5 MHz and a lot of the studies of these exciting objects have been made up to the present time at radio frequencies below 1.6 GHz. The reasons for this concentration on the low radio frequency characteristics of pulsars is the fact that the spectra are very steep and that very few radio telescopes exist that are capable of efficient operations at high radio frequencies. The Effelsberg 100-m radio telescope of the Max-Planck-Institut fur Radioastronomie operates regularly up to the frequency of 50 GHz and was used to study pulsars at cm/mm-wavelengths. In the southern skies the Parkes 64-m telescope has been used to study pulsars up to 8.4 GHz. One pulsar has been detected at 87 GHz with the 30-m Pico Veleta telescope of IRAM.

The studies of pulsars over the whole frequency range are of great importance because this is necessary for the elucidation of the mechanism that is responsible for the pulsar emission. The high polarization of pulsar radio emission at lower radio frequencies has supported the hypothesis of a coherent emission mechanism, which is required to generate the high luminosity. It has been known for some time that pulsars, unlike other radio sources, have a lower polarization at high radio frequencies. Recently a change of pulsar spectrum, a flattening or possibly an inversion has been observed at the highest radio frequencies. The inversion of the pulsar spectrum seems to coincide with a complete depolarization of some pulsars.

Millisecond pulsars are less luminous than normal pulsars. This makes them even more difficult to detect at higher radio frequencies. Recent observations have extended the spectra of ten millisecond pulsars up to 4.85 GHz. The results imply that millisecond pulsars have properties very similar to normal (slow) pulsars, which suggests similar emission mechanisms.

We describe the expected distribution of intensity for a scintillating source of finite size observed through a scattering medium, including systematic and instrumental effects. We describe measurements of the size of the Vela pulsar, using this technique.

We have measured the properties of the diffractive scintillation toward the Vela pulsar under the extremely strong scattering conditions encountered at 660 MHz. We obtain a decorrelation bandwidth of vd = 244±4 Hz and diffractive decorrelation timescale of tdiff = 3.3±0.3s. Our measurement of the modulation indices m = 0.87±0.003±0.05 and m = 0.93±0.03±0.05 (one For each polarization stream), are at variance with the modulation index of the Vela pulsar obtained at 2.3 GHz by Gwinn et al. (F997) if the deviation from a modulation index of unity is ascribed to a source size effect.

We present a method that allows to find the radial separation of regions emitting individual components of pulsar average profiles at two radio frequencies. It may also be used for single–frequency observations in pulsars that have intensity–dependent average profiles and/or mode–switching. Preliminary results for three radio pulsars are presented, obtained using average profiles from non-simultaneous observations.

A review of the pulsar radio spectra is continued. Two approches of the spectrum construction are considered. The influence of the interstellar stcintillations on the pulsar flux density measurements and spectra is examined. The description of new pulsar spectra catalog is made. Examples of different types of spectra including one for Geminga are presented.

We have extended the database of flux density measurements of 280 pulsars made by Lorimer et al. (1995) to frequencies higher than 1.4 GHz and lower than 300 MHz. Our analysis shows that the spectral behaviour of the majority of pulsars can be well described by a simple power law (S ~ υα where = −1.8) though some pulsar spectra are described by a ”broken power law” with a break at high frequencies υb ~ 1.8 GHz.

We report the most recent progress in understanding the emission properties of millisecond pulsars.

Millisecond pulsars are differ to ”normal” ones in much weaker frequency dependence of the width of integrated profiles and the absence of the low-frequency turn-over in pulsar spectra.

MSP are very similar to NP, but need higher accelerating voltage, because of different emitting agent.

We have used the VLA to image the location of the gamma-ray pulsar Geminga at 74 and 326 MHz. Upper limits to the pulse-averaged flux density, taking diffractive scintillation (DISS) into account, are S < 56 mJy (2σ; DISS quenched) at 74 MHz and S < 5 mJy (95% confidence) at 326 MHz. Intrinsic variability appears to be required in order to reconcile our upper limits with previous low-frequency detections.

The measurements of profiles at 102, 87, 59 and 40 MHz are presented. Geminga shows unique character of radio emission: the most steep spectrum, the large changes of pulse widths, phases of pulse time of arrival and the presence of giant pulses.

Faraday Rotation of the plane of polarization of broad-band signals, during propagation through the intervening medium, manifests as quasi-sinusoidal spectral modulations when observed with a telescope sensitive to a single linear polarization. Such a modulation can be exploited to study linear polarization characteristics of pulsars (Suleimanova, Volodin, & Shitov, 1988; Smirnova & Boriakoff 1997, Ramkumar & Deshpande 1999 (RD99)). We have used our data on a few bright pulsars at 35 MHz (Asgekar & Deshpande 1999, elsewhere in this volume) and data obtained at 327 MHz using Ooty Radio Telescope (see RD99 for details), to study average linear polarization properties using this technique. The data obtained over 256 frequency channels were re-sampled in the spectral domain to make the Faraday modulation appear periodic, and then a simple Fourier analysis was performed to look for (ACF) features associated with the possible spectral modulation (see RD99 for the analysis details).