Submillisecond Radio Intensity Variations in Pulsars

Craft, H. D.; Comella, J. M.; Drake, F. D.

doi:10.1038/2181122a0

Cited by 58 publications

(30 citation statements)

References 5 publications

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“…Examples include Langmuir waves in the source regions of interplanetary type III solar radio bursts 1,2 and planetary foreshocks, [3][4][5] pulsar radio emissions, 6,7 and various wave modes in laboratory plasmas. 8,9 Statistical plasma theories such as stochastic growth theory ͑SGT͒, 10,11 nonlinear strong turbulence theory ͑STT͒, 12 and self-organized criticality ͑SOC͒ 13 have successfully described wave fluctuations in various complex systems in laboratory, space, astrophysical, and simulated plasmas.…”

Section: Introductionmentioning

confidence: 99%

Waveform and envelope field statistics for waves with stochastically driven amplitudes

Cairns

Robinson

et al. 2010

Physics of Plasmas

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The statistically steady distributions P͑log E͒ and P e ͑log E e ͒ of waveform field E and envelope field E e are studied for time-varying waves with stochastically driven amplitudes. The waves are represented in one dimension ͑1D͒ by a single mode or superposition of multiple independent modes, whose amplitudes follow stochastic differential equations. Both distributions at low fields follow power laws: P͑log E͒ ϰ E p and P e ͑log E e ͒ ϰ E e q with distinct exponents p and q. Transitions in both distributions are found between the single-mode and multimode cases, with the distributions in the latter essentially independent of the number N ͑provided N Ն 2͒ of modes. For N Ն 2, p Ϸ +1.0, q Ϸ +2.0, and both distributions agree quantitatively with independent analytic predictions. Applications to Langmuir waves observed in Earth's polar cusp ionosphere show that both distributions for N Ն 2 agree quantitatively with the respective observations, suggesting that the Langmuir waves may be 1D and have a stochastic driver.

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Section: Introductionmentioning

confidence: 99%

Waveform and envelope field statistics for waves with stochastically driven amplitudes

Cairns

Robinson

et al. 2010

Physics of Plasmas

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“…For a number of pulsars, these sub‐pulses drift across the pulse window with a certain drift rate that is determined by the separation of two drifting sub‐pulses within a single pulse and the period at which sub‐pulses re‐occur at the same pulse phase (Backer 1970). Yet, there is another sub‐class of pulsars, for which micro‐structure has been identified (Craft, Comella & Drake 1968). Usually sitting on top of sub‐pulses, micro‐pulses appear to be concentrated features of emission which often exhibit typical widths τ μ and sometimes appear quasi‐periodic within a sub‐pulse, showing a periodicity, P μ (Hankins 1971).…”

Section: Introductionmentioning

confidence: 99%

High-resolution single-pulse studies of the Vela pulsar

Krämer¹,

Johnston²,

Straten³

2002

Monthly Notices of the Royal Astronomical Society

101

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We present high‐resolution multi‐frequency single‐pulse observations of the Vela pulsar, PSR B0833 − 45, aimed at studying micro‐structure, phase‐resolved intensity fluctuations and energy distributions at 1.41 and 2.30 GHz. We find micro‐structure in about 80 per cent of all pulses independent of observing frequency. The width of a micro‐pulse seems to depend on its peak flux density, whilst quasi‐periodicities observed in micro‐pulses remain constant. The width of the micro‐pulses may decrease with increasing frequency, but confirmation is needed at higher frequencies. The fraction of pulses showing quasi‐periodic micro‐pulses may become smaller at higher frequencies. We show that the micro‐pulse width in pulsars has a period dependence which suggests a model of sweeping micro‐beams as the origin of the micro‐pulses. Like individual pulses, the micro‐pulses of Vela are highly elliptically polarized. There is a strong correlation between Stokes parameters V and I in the micro‐structure. We do not observe any micro‐pulses where the handedness of the circular intensity changes within a micro‐pulse, although flips within a pulse are not uncommon. We show that the V/I distribution is Gaussian with a narrow width and that this width appears to be constant as a function of pulse phase. The phase‐resolved intensity distributions of I are best fitted with log‐normal statistics. Extra emission components, i.e. ‘bump’ and ‘giant micro‐pulses’, discovered by Johnston et al. at 0.6 and 1.4 GHz are also present at the higher frequency of 2.3 GHz. The bump component seems to be an extra component superposed on the main pulse profile but does not appear periodically. The giant micro‐pulses are time‐resolved and have significant jitter in their arrival times. Their flux density distribution is best fitted by a power‐law, indicating a link between these features and ‘classical’ giant pulses as observed for the Crab pulsar (PSR B0531 + 21), PSR B1937 + 21 and PSR B1821 − 24. We find that Vela contains a mixture of emission properties representing both ‘classical’ properties of radio pulsars (e.g. micro‐structure, high degree of polarization, S‐like position angle swing, orthogonal modes) and features which are most likely related to high‐energy emission (e.g. extra profile components, giant micro‐pulses). It hence represents an ideal test case to study the relationship between radio and high‐energy emission in significant detail.

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“…The variability of pulsar emissions, both from pulse to pulse at a given phase and from phase to phase within a pulse, has long been unexplained (Hankins 1996). These variations include subpulses (Drake & Craft 1968), with durations of order 10–50 per cent of the width of the average profile and sometimes a steady drift in phase, and microstructures superposed on the subpulses (Craft, Comella & Drake 1968; Hankins 1996), which are concentrated bursts of emissions that sometimes appear quasi‐periodic. The statistics of the variable fields, such as the probability distribution of fields, have not been characterized until recently (Cairns, Johnston & Das 2001, hereafter Paper I) and few constraints have been placed on pulsar emission mechanisms, despite decades of research.…”

Section: Introductionmentioning

confidence: 99%

Intrinsic variability and field statistics for the Vela pulsar -- III. Two-component fits and detailed assessment of stochastic growth theory

Cairns¹,

Das²,

Robinson³

et al. 2003

Monthly Notices of the Royal Astronomical Society

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The variability of the Vela pulsar (PSR B0833–45) corresponds to well‐defined field statistics that vary with pulsar phase, ranging from Gaussian intensity statistics off‐pulse to approximately power‐law statistics in a transition region and then lognormal statistics on‐pulse, excluding giant micropulses. These data are analysed here in terms of two superposed wave populations, using a new calculation for the amplitude statistics of two vectorially combined transverse fields. Detailed analyses show that the approximately power‐law and lognormal distributions observed are well fitted at essentially all on‐pulse phases by Gaussian–lognormal and double‐lognormal combinations, respectively. The good fits found, plus the smooth but significant variations in fitting parameters across the source, provide strong evidence that the approximately power‐law statistics observed in the transition region are not intrinsic. Instead, the data are consistent with the normal emission of the pulsar having lognormal statistics whenever the pulsar is detectable. This is consistent with generation in an inhomogeneous source obeying stochastic growth theory (SGT) and with the emission mechanism being purely linear (either direct or indirect), with no evidence for non‐linear processes. A non‐linear mechanism is viable only if it produces lognormal statistics when suitably ensemble‐averaged. Variations in the SGT fit parameters with phase are consistent with the radiation being relatively more variable near the pulse edges than near the centre, consistent with earlier work. In contrast, the giant micropulses of Vela come from a very restricted phase range and have power‐law statistics with indices (6.7 ± 0.6) not inconsistent with non‐linear wave collapse. These results are consistent with normal pulses coming from a source and generation mechanism different from giant micropulses, as suggested previously on other grounds. Analysis of field statistics thus emphasizes the richness of pulsar physics, the apparently widespread applicability of SGT, and connections between variability and the generation mechanism.

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Submillisecond Radio Intensity Variations in Pulsars

Cited by 58 publications

References 5 publications

Waveform and envelope field statistics for waves with stochastically driven amplitudes

Waveform and envelope field statistics for waves with stochastically driven amplitudes

High-resolution single-pulse studies of the Vela pulsar

Intrinsic variability and field statistics for the Vela pulsar -- III. Two-component fits and detailed assessment of stochastic growth theory

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