Can a Strong Radio Burst Escape the Magnetosphere of a Magnetar?

Abstract We examine the possibility that fast radio bursts (FRBs) are emitted inside the magnetosphere of a magnetar. On its way out, the radio wave must interact with a low-density e ± plasma in the outer magnetosphere at radii R = 109–1010 cm. In this region, the magnetospheric particles have a huge cross section for scattering the wave. As a result, the wave strongly interacts with the magnetosphere and compresses it, depositing the FRB energy into the compressed field and the scattered radiation. The scattered spectrum extends to the γ-ray band and triggers e ± avalanche, further boosting the opacity. These processes choke FRBs, disfavoring scenarios with a radio source confined at R ≪ 1010 cm. Observed FRBs can be emitted by magnetospheric flare ejecta transporting energy to large radii.

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LOFAR observations of radio burst source sizes and scattering in the solar corona

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038518 ◽

2020 ◽

Vol 645 ◽

pp. A11

Author(s):

Pearse C. Murphy ◽

Eoin P. Carley ◽

Aoife Maria Ryan ◽

Pietro Zucca ◽

Peter T. Gallagher

Keyword(s):

Solar Corona ◽

Radio Source ◽

Radio Wave ◽

Radio Burst ◽

Wave Scattering ◽

Low Frequency ◽

Density Fluctuations ◽

Source Size ◽

Burst Source ◽

Low Frequencies

Low frequency radio wave scattering and refraction can have a dramatic effect on the observed size and position of radio sources in the solar corona. The scattering and refraction is thought to be due to fluctuations in electron density caused by turbulence. Hence, determining the true radio source size can provide information on the turbulence in coronal plasma. However, the lack of high spatial resolution radio interferometric observations at low frequencies, such as with the LOw Frequency ARray (LOFAR), has made it difficult to determine the true radio source size and level of radio wave scattering. Here we directly fit the visibilities of a LOFAR observation of a Type IIIb radio burst with an elliptical Gaussian to determine its source size and position. This circumvents the need to image the source and then de-convolve LOFAR’s point spread function, which can introduce spurious effects to the source size and shape. For a burst at 34.76 MHz, we find full width at half maximum (FWHM) heights along the major and minor axes to be 18.8′ ± 0.1′ and 10.2′ ± 0.1′, respectively, at a plane of sky heliocentric distance of 1.75 R⊙. Our results suggest that the level of density fluctuations in the solar corona is the main cause of the scattering of radio waves, resulting in large source sizes. However, the magnitude of ε may be smaller than what has been previously derived in observations of radio wave scattering in tied-array images.

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Multiwavelength Observations of Fast Radio Bursts

Universe ◽

10.3390/universe7030076 ◽

2021 ◽

Vol 7 (3) ◽

pp. 76

Author(s):

Luciano Nicastro ◽

Cristiano Guidorzi ◽

Eliana Palazzi ◽

Luca Zampieri ◽

Massimo Turatto ◽

...

Keyword(s):

Radio Burst ◽

High Energy ◽

Medium Size ◽

Radio Bursts ◽

Starting Point ◽

Key Points ◽

Fast Radio Burst ◽

Theoretical Results ◽

Observational Strategy ◽

Shed Light

The origin and phenomenology of the Fast Radio Burst (FRB) remains unknown despite more than a decade of efforts. Though several models have been proposed to explain the observed data, none is able to explain alone the variety of events so far recorded. The leading models consider magnetars as potential FRB sources. The recent detection of FRBs from the galactic magnetar SGR J1935+2154 seems to support them. Still, emission duration and energetic budget challenge all these models. Like for other classes of objects initially detected in a single band, it appeared clear that any solution to the FRB enigma could only come from a coordinated observational and theoretical effort in an as wide as possible energy band. In particular, the detection and localisation of optical/NIR or/and high-energy counterparts seemed an unavoidable starting point that could shed light on the FRB physics. Multiwavelength (MWL) search campaigns were conducted for several FRBs, in particular for repeaters. Here we summarize the observational and theoretical results and the perspectives in view of the several new sources accurately localised that will likely be identified by various radio facilities worldwide. We conclude that more dedicated MWL campaigns sensitive to the millisecond–minute timescale transients are needed to address the various aspects involved in the identification of FRB counterparts. Dedicated instrumentation could be one of the key points in this respect. In the optical/NIR band, fast photometry looks to be the only viable strategy. Additionally, small/medium size radiotelescopes co-pointing higher energies telescopes look a very interesting and cheap complementary observational strategy.

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No Evidence for Galactic Latitude Dependence of the Fast Radio Burst Sky Distribution

The Astrophysical Journal ◽

10.3847/1538-4357/ac33ad ◽

2021 ◽

Vol 923 (1) ◽

pp. 2 ◽

Cited By ~ 1

Author(s):

A. Josephy ◽

P. Chawla ◽

A. P. Curtin ◽

V. M. Kaspi ◽

M. Bhardwaj ◽

...

Keyword(s):

Radio Burst ◽

Sensitivity Threshold ◽

Galactic Latitude ◽

Radio Bursts ◽

Intensity Mapping ◽

Latitude Dependence ◽

Kolmogorov Smirnov ◽

Coin Flipping ◽

Fast Radio Burst ◽

Anderson Darling

Abstract We investigate whether the sky rate of fast radio bursts (FRBs) depends on Galactic latitude using the first catalog of FRBs detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) Project. We first select CHIME/FRB events above a specified sensitivity threshold in consideration of the radiometer equation, and then we compare these detections with the expected cumulative time-weighted exposure using Anderson–Darling and Kolmogorov–Smirnov tests. These tests are consistent with the null hypothesis that FRBs are distributed without Galactic latitude dependence (p-values distributed from 0.05 to 0.99, depending on completeness threshold). Additionally, we compare rates in intermediate latitudes (∣b∣ < 15°) with high latitudes using a Bayesian framework, treating the question as a biased coin-flipping experiment–again for a range of completeness thresholds. In these tests the isotropic model is significantly favored (Bayes factors ranging from 3.3 to 14.2). Our results are consistent with FRBs originating from an isotropic population of extragalactic sources.

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Analyzing the propagation of EUV waves and their connection with type II radio bursts by combining numerical simulations and multi-instrument observations

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038699 ◽

2020 ◽

Vol 644 ◽

pp. A90

Author(s):

A. Koukras ◽

C. Marqué ◽

C. Downs ◽

L. Dolla

Keyword(s):

Magnetic Field ◽

Wave Front ◽

Ray Tracing ◽

Radio Burst ◽

Radio Bursts ◽

Type Ii ◽

Fast Mode ◽

Type Ii Radio Bursts ◽

The Magnetic Field ◽

Burst Emission

Context. EUV (EIT) waves are wavelike disturbances of enhanced extreme ultraviolet (EUV) emission that propagate away from an eruptive active region across the solar disk. Recent years have seen much debate over their nature, with three main interpretations: the fast-mode magneto-hydrodynamic (MHD) wave, the apparent wave (reconfiguration of the magnetic field), and the hybrid wave (combination of the previous two). Aims. By studying the kinematics of EUV waves and their connection with type II radio bursts, we aim to examine the capability of the fast-mode interpretation to explain the observations, and to constrain the source locations of the type II radio burst emission. Methods. We propagate a fast-mode MHD wave numerically using a ray-tracing method and the WKB (Wentzel-Kramers-Brillouin) approximation. The wave is propagated in a static corona output by a global 3D MHD Coronal Model, which provides density, temperature, and Alfvén speed in the undisturbed coronal medium (before the eruption). We then compare the propagation of the computed wave front with the observed wave in EUV images (PROBA2/SWAP, SDO/AIA). Lastly, we use the frequency drift of the type II radio bursts to track the propagating shock wave, compare it with the simulated wave front at the same instant, and identify the wave vectors that best match the plasma density deduced from the radio emission. We apply this methodology for two EUV waves observed during SOL2017-04-03T14:20:00 and SOL2017-09-12T07:25:00. Results. The simulated wave front displays a good qualitative match with the observations for both events. Type II radio burst emission sources are tracked on the wave front all along its propagation. The wave vectors at the ray-path points that are characterized as sources of the type II radio burst emission are quasi-perpendicular to the magnetic field. Conclusions. We show that a simple ray-tracing model of the EUV wave is able to reproduce the observations and to provide insight into the physics of such waves. We provide supporting evidence that they are likely fast-mode MHD waves. We also narrow down the source region of the radio burst emission and show that different parts of the wave front are responsible for the type II radio burst emission at different times of the eruptive event.

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Variable emission mechanism of a Type IV radio burst

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834510 ◽

2019 ◽

Vol 623 ◽

pp. A63 ◽

Cited By ~ 5

Author(s):

D. E. Morosan ◽

E. K. J. Kilpua ◽

E. P. Carley ◽

C. Monstein

Keyword(s):

Frequency Band ◽

Radio Burst ◽

Extreme Ultraviolet ◽

Imaging Spectroscopy ◽

Continuum Emission ◽

Particle Accelerators ◽

Radio Bursts ◽

Emission Mechanism ◽

Type Iv ◽

Dynamic Spectra

Context. The Sun is an active star and the source of the largest explosions in the solar system, such as flares and coronal mass ejections (CMEs). Flares and CMEs are powerful particle accelerators that can generate radio emission through various emission mechanisms. Aims. CMEs are often accompanied by Type IV radio bursts that are observed as continuum emission in dynamic spectra at decimetric and metric wavelengths, but their emission mechanism can vary from event to event. Here, we aim to determine the emission mechanism of a complex Type IV burst that accompanied the flare and CME on 22 September 2011. Methods. We used radio imaging from the Nançay Radioheliograph, spectroscopic data from the e-Callisto network, ARTEMIS, Ondrejov, and Phoenix3 spectrometers combined with extreme-ultraviolet observations from NASA’s Solar Dynamic Observatory to analyse the Type IV radio burst and determine its emission mechanism. Results. We show that the emission mechanism of the Type IV radio burst changes over time. We identified two components in the Type IV radio burst: an earlier stationary Type IV showing gyro-synchrotron behaviour, and a later moving Type IV burst covering the same frequency band. This second component has a coherent emission mechanism. Fundamental plasma emission and the electron-cyclotron maser emission are further investigated as possible emission mechanisms for the generation of the moving Type IV burst. Conclusions. Type IV bursts are therefore complex radio bursts, where multiple emission mechanisms can contribute to the generation of the wide-band continuum observed in dynamic spectra. Imaging spectroscopy over a wide frequency band is necessary to determine the emission mechanisms of Type IV bursts that are observed in dynamic spectra.

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Density and temperature effects on electron mobilities in gaseous butene isomers

Canadian Journal of Chemistry ◽

10.1139/v79-440 ◽

1979 ◽

Vol 57 (20) ◽

pp. 2716-2726 ◽

Cited By ~ 15

Author(s):

Toshinori Wada ◽

Gordon R. Freeman

Keyword(s):

Cross Section ◽

Coexistence Curve ◽

Inelastic Collisions ◽

Low Density ◽

Similar Extent ◽

Small Temperature ◽

In Trans ◽

Strength Formula ◽

Increasing Temperature ◽

In Cis

The density normalized mobilities μn at low electric field strengths in the low density gases fall in the order trans-2- > cis-2- > 1- > isobutene. The respective values in the saturated vapors at 297 ± 1 K were 10.7, 4.4, 3.8, and 1.84 (1022 molecules/cm V s). The scattering cross section σv has a Ramsauer–Townsend-like minimum at an electron energy of 0.085 eV in trans-2-butene, 0.13 eV in cis-2-butene, 0.12 eV in 1-butene, and 0.16 eV in isobutene. The mobilities in the last three isomers increase with increasing temperature (300–500 K) and field strength [Formula: see text]. Temperature and field effects were smaller in trans-2-butene. The ratio of the field effect threshold drift velocity to the speed of sound in the low density gas is 14, 19, 20, and > 50 in iso-, 1-, cis-2-, and trans-2-butene, respectively, at 297 K. The electrons are de-energized mainly by inelastic collisions. Quasilocalization occurs to a similar extent in each of the isomers at densities [Formula: see text] and temperatures near the coexistence curve. Quasilocalization is characterized by large, negative values of ΔH and ΔS, and a small value of ΔG over a small temperature range.

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A Decade and a Half of Fast Radio Burst Observations

Universe ◽

10.3390/universe7110453 ◽

2021 ◽

Vol 7 (11) ◽

pp. 453

Author(s):

Manisha Caleb ◽

Evan Keane

Keyword(s):

Magnetic Field ◽

Radio Burst ◽

Line Of Sight ◽

Radio Bursts ◽

Radio Observations ◽

The Past ◽

Interstellar Media ◽

Propagation Effects ◽

Fast Radio Burst ◽

The Universe

Fast radio bursts (FRBs) have a story which has been told and retold many times over the past few years as they have sparked excitement and controversy since their pioneering discovery in 2007. The FRB class encompasses a number of microsecond- to millisecond-duration pulses occurring at Galactic to cosmological distances with energies spanning about 8 orders of magnitude. While most FRBs have been observed as singular events, a small fraction of them have been observed to repeat over various timescales leading to an apparent dichotomy in the population. ∼50 unique progenitor theories have been proposed, but no consensus has emerged for their origin(s). However, with the discovery of an FRB-like pulse from the Galactic magnetar SGR J1935+2154, magnetar engine models are the current leading theory. Overall, FRB pulses exhibit unique characteristics allowing us to probe line-of-sight magnetic field strengths, inhomogeneities in the intergalactic/interstellar media, and plasma turbulence through an assortment of extragalactic and cosmological propagation effects. Consequently, they are formidable tools to study the Universe. This review follows the progress of the field between 2007 and 2020 and presents the science highlights of the radio observations.

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Interferometric imaging with LOFAR remote baselines of the fine structures of a solar type-IIIb radio burst

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037733 ◽

2020 ◽

Vol 639 ◽

pp. A115

Author(s):

PeiJin Zhang ◽

Pietro Zucca ◽

Sarrvesh Seethapuram Sridhar ◽

ChuanBing Wang ◽

Mario M. Bisi ◽

...

Keyword(s):

Radio Burst ◽

Solar Radio ◽

Source Size ◽

Radio Bursts ◽

Solar Radio Bursts ◽

Harmonic Emission ◽

Apparent Source ◽

Solar Type ◽

Fine Structures ◽

Source Motion

Context. Solar radio bursts originate mainly from high energy electrons accelerated in solar eruptions like solar flares, jets, and coronal mass ejections. A sub-category of solar radio bursts with short time duration may be used as a proxy to understand wave generation and propagation within the corona. Aims. Complete case studies of the source size, position, and kinematics of short term bursts are very rare due to instrumental limitations. A comprehensive multi-frequency spectroscopic and imaging study was carried out of a clear example of a solar type IIIb-III pair. Methods. In this work, the source of the radio burst was imaged with the interferometric mode, using the remote baselines of the LOw Frequency ARray (LOFAR). A detailed analysis of the fine structures in the spectrum and of the radio source motion with imaging was conducted. Results. The study shows how the fundamental and harmonic components have a significantly different source motion. The apparent source of the fundamental emission at 26.56 MHz displaces away from the solar disk center at about four times the speed of light, while the apparent source of the harmonic emission at the same frequency shows a speed of < 0.02 c. The source size of the harmonic emission observed in this case is smaller than that in previous studies, indicating the importance of the use of remote baselines.

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Young magnetars with fracturing crusts as fast radio burst repeaters

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2052 ◽

2019 ◽

Vol 488 (4) ◽

pp. 5887-5897 ◽

Cited By ~ 7

Author(s):

A G Suvorov ◽

K D Kokkotas

Keyword(s):

Statistical Analysis ◽

Power Law ◽

Radio Burst ◽

Rapid Evolution ◽

Compact Objects ◽

Tectonic Activity ◽

Radio Bursts ◽

Crustal Field ◽

Long Time ◽

Fast Radio Burst

Abstract Fast radio bursts are millisecond-duration radio pulses of extragalactic origin. A recent statistical analysis has found that the burst energetics of the repeating source FRB 121102 follow a power law, with an exponent that is curiously consistent with the Gutenberg–Richter law for earthquakes. This hints that repeat bursters may be compact objects undergoing violent tectonic activity. For young magnetars, possessing crustal magnetic fields which are both strong (B ≳ 1015 G) and highly multipolar, Hall drift can instigate significant field rearrangements even on ≲ century long time-scales. This reconfiguration generates zones of magnetic stress throughout the outer layers of the star, potentially strong enough to facilitate frequent crustal failures. In this paper, assuming a quake scenario, we show how the crustal field evolution, which determines the resulting fracture geometries, can be tied to burst properties. Highly anisotropic stresses are generated by the rapid evolution of multipolar fields, implying that small, localized cracks can occur sporadically throughout the crust during the Hall evolution. Each of these shallow fractures may release bursts of energy, consistent in magnitude with those seen in the repeating sources FRB 121102 and FRB 180814.J0422+73.

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The performance and calibration of the CRAFT fly’s eye fast radio burst survey

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2019.1 ◽

2019 ◽

Vol 36 ◽

Cited By ~ 11

Author(s):

C. W. James ◽

K. W. Bannister ◽

J.-P. Macquart ◽

R. D. Ekers ◽

S. Oslowski ◽

...

Keyword(s):

Radio Burst ◽

Phased Array ◽

Radio Frequency Interference ◽

Radio Bursts ◽

System Noise ◽

Fast Transients ◽

Fast Radio Burst ◽

Power Law Index ◽

Phased Array Feeds ◽

Best Fit

AbstractThe Commensal Real-time Australian Square Kilometre Array Pathfinder Fast Transients survey is the first extensive astronomical survey using phased array feeds. Since January 2017, it has been searching for fast radio bursts in fly’s eye mode. Here, we present a calculation of the sensitivity and total exposure of the survey that detected the first 20 of these bursts, using the pulsars B1641-45 and B0833-45 as calibrators. The beamshape, antenna-dependent system noise, and the effects of radio-frequency interference and fluctuations during commissioning are quantified. Effective survey exposures and sensitivities are calculated as a function of the source counts distribution. Statistical ‘stat’ and systematics ‘sys’ effects are treated separately. The implied fast radio burst rate is significantly lower than the 37 sky−1 day−1 calculated using nominal exposures and sensitivities for this same sample by Shannon et al. (2018). At the Euclidean (best-fit) power-law index of −1.5 (−2.2), the rate is $12.7_{-2.2}^{+3.3}$ (sys) ± 3.6 (stat) sky−1 day−1 ( $20.7_{-1.7}^{+2.1}$ (sys) ± 2.8 (stat) sky−1 day−1) above a threshold of 56.6 ± 6.6(sys) Jy ms (40.4 ± 1.2(sys) Jy ms). This strongly suggests that these calculations be performed for other FRB-hunting experiments, allowing meaningful comparisons to be made between them.

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