Polarized quasiperiodic structures in pulsar radio emission reflect temporal modulations of non-stationary plasma flow

Journal Article · Sat Jun 20 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/806/2/236· OSTI ID:22883001

Mitra, Dipanjan ^[1]; Arjunwadkar, Mihir ^[2]

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1. National Centre for Radio Astrophysics, TIFR, Pune 411007 (India)
2. Centre for Modeling and Simulation, Savitribai Phule Pune University, Pune 411007 (India)

Bright single pulses of many radio pulsars show rapid intensity fluctuations (called microstructure) when observed with time resolutions of tens of microseconds. Here, we report an analysis of Arecibo 59.5 μs resolution polarimetric observations of 11 P-band and 32 L-band pulsars with periods ranging from 150 ms to 3.7 s. These higher-frequency observations form the most reliable basis for detailed microstructure studies. Close inspection of individual pulses reveals that most pulses exhibit quasi-periodicities with a well-defined periodicity timescale (P{sub μ}). While we find some pulses with deeply modulating microstructure, most pulses show low-amplitude modulations on top of broad smooth subpulse features, thereby making it difficult to infer periodicities. We have developed a method for such low-amplitude fluctuations wherein a smooth subpulse envelope is subtracted from each de-noised subpulse; the fluctuating portion of each subpulse is then used to estimate P{sub μ} via autocorrelation analysis. We find that the microstructure timescale P{sub μ} is common across all Stokes parameters of polarized pulsar signals. Moreover, no clear signature of curvature radiation in vacuum in highly resolved microstructures was found. Our analysis further shows strong correlation between P{sub μ} and the pulsar period P. We discuss implications of this result in terms of a coherent radiation model wherein radio emission arises due to formation and acceleration of electron–positron pairs in an inner vacuum gap over magnetic polar cap, and a subpulse corresponds to a series of non-stationary sparking discharges. We argue that in this model, P{sub μ} reflects the temporal modulation of non-stationary plasma flow.

• OSTI ID: 22883001
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 806; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COHERENT RADIATION
EMISSION
FLUCTUATIONS
INDIUM FLUORIDES
MAGNETOHYDRODYNAMICS
PERIODICITY
PLASMA
PULSARS
STOKES PARAMETERS
TIME RESOLUTION