Microstructure in Radio Emission of the Pulsar B1133+16 at a Frequency of 111 MHz

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Abstract

This study is based on observations of the pulsar B1133+16 conducted on the BSA PRAO antenna array at a frequency of 111 MHz with continuous recording of undetected signal (voltage) in the 2.5 MHz band, providing time resolution 0.2 microseconds. From 30 observing sessions, 570 strong pulses were selected for the subsequent analysis of microstructure parameters. The analysis was performed by computing autocorrelation functions separately for the three components of the mean profile: two extreme main components I and II and for the central weak component S in the profile saddle. For the component S microstructure analysis was performed for the first time. Distributions have been constructed by the following parameters: time scales τµ, modulation depth mµ, and the parameter d, which characterizes the shape of the micropulses. Noticeable differences were found in some parameters for different profile components. The discovered features were interpreted in the model of hollow cone with a central component. It was believed that the radio emission of the extreme components (I and II) is generated by ordinary mode O, and the radio emission of the central component is provided by extraordinary mode X. Under this interpretation the radio emission output heights above the polar cap, were estimated to be 45 and 280 km for the X and O modes, respectively. A noticeable deformation of the X mode emission cone relative to the central component S was mentioned. Considerations are presented that point to the spatial structure of the secondary plasma flow, elongated along the meridians of the magnetic field.

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About the authors

M. V. Popov

P. N. Lebedev Physical Institute of the Russian Academy of Sciences

Author for correspondence.
Email: popov069@asc.rssi.ru
Russian Federation, Moscow

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Supplementary files

Supplementary Files
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2. Fig. 1. Mean profile obtained by averaging 4872 pulses recorded in 30 observation sessions. The crosses represent the observational data, and the solid lines show the approximation of the data by a set of three components (components I, S, II) given by the Gaussian function

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3. Fig. 2. Examples of strong individual pulses observed simultaneously in several components of the mean profile. The scale on the ordinate axis is given in units of analogue-to-digital converter (ADC) counts; a flux of 1 Jan corresponds to about 50 ADC units. The date of observation and the pulse number are indicated in the figures. The time resolution of the presented records is 200 µs

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4. Fig. 3. Average autocorrelation functions for the three components of the mean profile obtained by averaging 369, 153, and 311 pulses for the I, S, and II components, respectively

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5. Fig. 4. Example of the ACF of a single strong pulse. The dashed line shows the approximation of the microstructural pattern, and the dotted line corresponds to the approximation of the sub-pulse component of the ACF

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6. Fig. 5. Distribution of the analysed pulses by microstructure parameters: top left the distribution by the exponent d of the approximating function (5), bottom left the distribution by the modulation index mµ, top right the distribution by the half-width of the sub-pulse pattern in the ACF Wsub, and bottom right the distribution by the microstructure scale τµ. The ordinate axis is digitised in all panels in fractions of events of the total number of pulses analysed

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7. Fig. 6. Dependence of the modulation index on the time scale of the microstructure. The circles represent data related to the first component of the mean profile (I). Crosses correspond to the last component (II), and triangles to the saddle (S)

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8. Fig. 7. Examples of quasi-periodic pulses. The autocorrelation functions are given on the left, the pulses themselves are shown on the right. The figures show the date of observation and the pulse number, with the last digit corresponding to the number of the mean profile component. For pulse No. 107, observed in the second component of the mean profile (II) on 09.11.2022, the time scale in the lower right window is stretched twice relative to the digitisation of the abscissa axis

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9. Fig. 8. Schematic of the radiation cones in projection on the picture plane. The point P denotes the magnetic pole. Line AB shows the trajectory of the viewing beam. The shaded areas O and X represent the O-mode and X-mode radiation exit zones. The angular dimension of line AB is 25°

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