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Iver H Cairns - One of the best experts on this subject based on the ideXlab platform.
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Spectropolarimetric Imaging of Metric Type III Solar Radio Bursts
Solar Physics, 2020Co-Authors: M. M. Rahman, Iver H Cairns, Patrick I MccauleyAbstract:We present low-frequency (80 – 240 MHz) Radio observations of circular polarization in 16 isolated type III Solar Radio Bursts using the Murchison Widefield Array (MWA) between August 2014 and November 2015. For most of the Bursts, near burst onset, we find on average 9 % $9\%$ circular polarization at 80 MHz and 22 % $22\%$ at 240 MHz whereas these percentages are 5 % $5\%$ and 20 % $20\%$ near burst maximum. The polarization fractions are neither constant in time nor uniform over the spatial extents of the Bursts. We measure polarization fractions as a function of burst source’s position. On average, near both burst onset and maximum, we find higher polarization near the disk center and lower polarization when the burst source is near the limb. We study total intensity (Stokes I $I$ ), circularly polarized intensity (Stokes V $V$ ), and polarization fraction ( | V | / I $| V| /I$ ) profiles for type III Bursts with and without source motion as a function of position at times when the intensity of Bursts is maximum. For the burst event with no source motion, we find symmetric profiles for Stokes I $I$ , V $V$ , and | V | / I $| V| /I$ . We find symmetric I $I$ and V $V$ but asymmetric | V | / I $| V| /I$ profiles for burst events which have source motion. We argue that this is due to the fundamental emission at the front of a type III electron beam and motion of the burst source. We then perform spectropolarimetric imaging studies of moving burst sources and analyze their motion. At burst onset, we obtain relatively higher polarization fractions, which is considered to be due to a large contribution from fundamental plasma emission at the front of the beam. At burst maximum, the polarization fraction is lower due to the combination of fundamental and harmonic components. After peak intensity, the emission is dominated again by the fundamental component that decays until the end of a burst with lesser polarization fraction than earlier. We argue that the fundamental radiation that decays over time after peak burst intensity is strongly scattered. This pattern of fundamental, fundamental and harmonic, and then fundamental emission with time at each frequency is consistent with the interpretations of Dulk, Suzuki, and Sheridan ( Astron. Astrophys. 130 , 39, 1984 ), Robinson, Cairns, and Willes ( Astrophys. J. 422 , 870, 1994 ), and Robinson and Cairns ( Solar Phys. 181 , 363, 1998 ). We propose that scattering effects can be a viable reason for low polarization fractions in type III events. Finally, we investigate the variations of the decay time ( t d $t_{d}$ ) for three events with frequency ( f $f$ ), finding that t d ∝ f − 2.0 ± 0.1 $t_{d} \propto f^{-2.0\pm 0.1}$ and decreases more rapidly with increasing f $f$ compared with previous lower-frequency observations ( t d ∝ f − 1.1 ± 0.1 $t_{d} \propto f^{-1.1\pm 0.1}$ ). This is interpreted in terms of radial variations of the turbulence properties.
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low altitude Solar magnetic reconnection type iii Solar Radio Bursts and x ray emissions
Scientific Reports, 2018Co-Authors: Iver H Cairns, D Oberoi, V V Lobzin, Alinacatalina Donea, S J Tingay, Patrick I Mccauley, R T DuffinAbstract:Type III Solar Radio Bursts are the Sun’s most intense and frequent nonthermal Radio emissions. They involve two critical problems in astrophysics, plasma physics, and space physics: how collective processes produce nonthermal radiation and how magnetic reconnection occurs and changes magnetic energy into kinetic energy. Here magnetic reconnection events are identified definitively in Solar Dynamics Observatory UV-EUV data, with strong upward and downward pairs of jets, current sheets, and cusp-like geometries on top of time-varying magnetic loops, and strong outflows along pairs of open magnetic field lines. Type III Bursts imaged by the Murchison Widefield Array and detected by the Learmonth Radiospectrograph and STEREO B spacecraft are demonstrated to be in very good temporal and spatial coincidence with specific reconnection events and with Bursts of X-rays detected by the RHESSI spacecraft. The reconnection sites are low, near heights of 5–10 Mm. These images and event timings provide the long-desired direct evidence that semi-relativistic electrons energized in magnetic reconnection regions produce type III Radio Bursts. Not all the observed reconnection events produce X-ray events or coronal or interplanetary type III Bursts; thus different special conditions exist for electrons leaving reconnection regions to produce observable Radio, EUV, UV, and X-ray Bursts.
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Importance of Kappa Distributions to Solar Radio Bursts
Kappa Distributions, 2017Co-Authors: Iver H Cairns, J. M. SchmidtAbstract:Abstract Non-Maxwellian electron distributions are observed widely throughout the Solar system and are often well described as kappa distributions. This chapter addresses the importance of kappa distributions to the growth and damping of plasma waves (specifically Langmuir waves), the reflection of electrons from shocks, the evolution of electron beams, and the generation of type II and III Solar Radio Bursts. Kappa distributions extend to much higher speeds and have many more fast particles than Maxwellians. Accordingly, kappa distributions lead to a much larger spontaneous emission of plasma waves and Radio emissions produced by incoherent processes. Similarly, shocks that accelerate the background electrons have much higher numbers of fast electrons upstream for kappa-distributed electrons than for Maxwellian electrons, leading to stronger electron beams and stronger Langmuir waves and Radio emissions. This is demonstrated theoretically for type II Solar Radio Bursts. The extension of kappa distributions to larger speeds than for Maxwellian distributions leads to larger damping rates for electron beam-generated Langmuir waves. It also limits the relaxation of the beam to higher speeds and reduces energy transfers to the Langmuir waves and any Radio emissions generated therefrom. These effects are demonstrated theoretically for type III Solar Radio Bursts, allowing us to understand why kappa distributions for the background electrons lead naturally to faster beams with speeds of ≳0.5c and to the type III Bursts being weaker, having faster frequency drift rates, and starting at lower frequencies for smaller values of the kappa index, κ.
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production of fine structures in type iii Solar Radio Bursts due to turbulent density profiles
The Astrophysical Journal, 2014Co-Authors: Shyeh Tjing Loi, Iver H CairnsAbstract:Magnetic reconnection events in the corona release energetic electron beams along open field lines, and the beams generate Radio emission at multiples of the electron plasma frequency f{sub p} to produce type III Solar Radio Bursts. Type III Bursts often exhibit irregularities in the form of flux modulations with frequency and/or local temporal advances and delays, and a type IIIb burst represents the extreme case where a type III burst is fragmented into a chain of narrowband features called striae. Remote and in situ spacecraft measurements have shown that density turbulence is ubiquitous in the corona and Solar wind, and often exhibits a Kolmogorov power spectrum. In this work, we numerically investigate the effects of one-dimensional macroscopic density turbulence (along the beam direction) on the behavior of type III Bursts, and find that this turbulence produces stria-like fine structures in the dynamic spectra of both f{sub p} and 2 f{sub p} radiation. Spectral and temporal fine structures in the predicted type III emission are produced by variations in the scattering path lengths and group speeds of Radio emission, and in the locations and sizes of emitting volumes. Moderate turbulence levels yield flux enhancements with much broader half-power bandwidths in f{submore » p} than 2 f{sub p} emission, possibly explaining the often observed type IIIb-III harmonic pairs as being where intensifications in 2 f{sub p} radiation are not resolved observationally. Larger turbulence levels producing trough-peak regions in the plasma density profile may lead to broader, resolvable intensifications in 2 f{sub p} radiation, which may account for the type IIIb-IIIb pairs that are sometimes observed.« less
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harmonic waves and sheath rectification in type iii Solar Radio Bursts
Journal of Geophysical Research, 2014Co-Authors: Daniel B Graham, Iver H Cairns, D MalaspinaAbstract:In type III Solar Radio Bursts and planetary foreshocks, Langmuir waves are produced by electron beams and converted partially to Radio waves by linear and nonlinear processes. Lower amplitude second harmonic electric fields are observed simultaneously during the most intense Langmuir wave events in type III source regions. The electric fields at the harmonic frequencies can arise from various mechanisms, such as Radio wave emission by either coalescence or antenna mechanisms, nonlinear currents, harmonics of Langmuir waves, electron trapping in Langmuir wave potentials, and Langmuir wave rectification at the sheath surrounding the spacecraft, or they can result from instrumental harmonics. In this paper the relative powers and electric field vectors of Langmuir waves and the harmonic fields are compared for multiple events. The structure of the harmonic field is shown to be determined by the Langmuir waveform, but the harmonic field direction is typically closely aligned with the Solar wind flow. The magnitude, structure, and orientation of the harmonic fields is used to determine which processes are responsible. It is shown that the dominant process generating the observed harmonic fields is Langmuir wave rectification at the sheath surrounding the spacecraft. Key Points Intense Langmuir waves and harmonic fields are observed simultaneously Harmonic fields are primarily produced by sheath rectification Some evidence for nonlinear currents is found
P.a. Robinson - One of the best experts on this subject based on the ideXlab platform.
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type ii Solar Radio Bursts modeling and extraction of shock parameters
Journal of Geophysical Research, 2012Co-Authors: Dean Hillan, Iver H Cairns, P.a. RobinsonAbstract:[1] This first paper in a two part series summarizes the current theory and the data-driven Solar wind model for simulating dynamic spectra of type II Radio Bursts. It also introduces performance metrics and techniques for extraction of model shock parameters from these dynamic spectra. We use an iterative downhill simplex method which compares two dynamic spectra and quantitatively assesses and improves the agreement using two figures of merit: the first is based on the correlation function and the second is based on a normalized differences over the data set. By maximizing the agreement we are able to extract the input model shock parameters to within 30% or better when using model Solar winds of increasing complexity. The effects on the spectra predicted and on the figures of merit from changing the model shock parameters and Solar wind model are also investigated. The iterative downhill extraction method is then applied to the type II dynamic spectrum predicted using a realistic model Solar wind and a shock model estimated for an observed type II event. The shock parameters are recovered to within 10% of the correct solution.
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automatic recognition of type iii Solar Radio Bursts automated Radio burst identification system method and first observations
Social Work, 2009Co-Authors: V V Lobzin, Iver H Cairns, P.a. Robinson, Graham Steward, Garth PattersonAbstract:[1] Because of the rapidly increasing role of technology, including complicated electronic systems, spacecraft, etc., modern society has become more vulnerable to a set of extraterrestrial influences (space weather) and requires continuous observation and forecasts of space weather. The major space weather events like Solar flares and coronal mass ejections are usually accompanied by Solar Radio Bursts, which can be used for a real-time space weather forecast. Coronal type III Radio Bursts are produced near the local electron plasma frequency and near its harmonic by fast electrons ejected from the Solar active regions and moving through the corona and Solar wind. These Bursts have dynamic spectra with frequency rapidly falling with time, the typical duration of the coronal burst being about 1–3 s. This paper presents a new method developed to detect coronal type III Bursts automatically and its implementation in a new Automated Radio Burst Identification System. The central idea of the implementation is to use the Radon transform for more objective detection of the Bursts as approximately straight lines in dynamic spectra. Preliminary tests of the method with the use of the spectra obtained during 13 days show that the performance of the current implementation is quite high, ∼84%, while no false positives are observed and 23 events not listed previously are found. Prospects for improvements are discussed. The first automatically detected coronal type III Radio Bursts are presented.
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simulations of coronal type iii Solar Radio Bursts 3 effects of beam and coronal parameters
Journal of Geophysical Research, 2009Co-Authors: Iver H Cairns, P.a. RobinsonAbstract:[1] A recently developed simulation model is used to investigate the effects of varying the coronal and electron heating conditions on the dynamic spectra of coronal type III Bursts (70–370 MHz) observed at Earth. The flux of 2fp emission is significantly higher than that of fp emission, which is unlikely to be observable except under very favorable propagation conditions. Moreover, the 2fp emission is unlikely to continue into the Solar wind, although some Bursts are very strong and will extend into the upper corona with lower frequencies than simulated, consistent qualitatively with observations. The flux and brightness temperature of 2fp emission are affected significantly by variations in the parameters, while the frequency drift rate and half-power duration are affected only weakly. Further, the simulations confirm the standard interpretation of the drift rate of 2fp emission in terms of the plasma density profile and a characteristic beam speed that agrees quantitatively with the simulated beam dynamics for wide ranges of coronal and heating conditions. For weak heating events or events with high coronal electron temperature, the remote radiation shows characteristics that agree quantitatively with microBursts. When the heating is even weaker and/or the electron temperature is even higher, the heating events are Radio quiet, consistent qualitatively with hard X-ray observations. For similar heating originating in similar frequency ranges, different density models yield quantitatively similar results except for the drift rate. Variations of the levels of a given density profile, corresponding to background corona or coronal streamers, can also cause significant changes in spectral characteristics.
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simulations of coronal type iii Solar Radio Bursts 1 simulation model
Journal of Geophysical Research, 2008Co-Authors: Iver H Cairns, P.a. RobinsonAbstract:[1] A simulation model is developed for type III Bursts that originate in the Solar corona and are observed at Earth. The model incorporates the three-dimensional structure of the source region, dynamics in the source of electron beam, Langmuir waves, ion-sound waves, electromagnetic emissions at the fundamental (fp) and second harmonic (2fp) of the plasma frequency, and propagation of electromagnetic radiation from the corona to interplanetary space, and it predicts the radiation dynamic spectrum measured by a remote observer. During the propagation of the radiation, the effects of refraction and reflection on large-scale density variations, scattering off small-scale density fluctuations, and free-free absorption are taken into account. The scattering of fp emission is modeled numerically on the basis of an analytic approach developed previously. The numerical results confirm approximations made in the approach and generalize it to more realistic Solar plasma conditions.
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simulations of coronal type iii Solar Radio Bursts 2 dynamic spectrum for typical parameters
Journal of Geophysical Research, 2008Co-Authors: Iver H Cairns, P.a. RobinsonAbstract:[1] Predictions are presented for the dynamic spectrum of a coronal type III burst observed at Earth, using a newly developed simulation model and employing realistic electron release and coronal parameters. The spectrum is studied in detail in association with the dynamics of beam and waves in the source. The frequency drift rate, Radio flux, brightness temperature, and temporal profile of the type III burst agree semiquantitatively with typical observations. The simulation model is thus viable. Because of strong free-free absorption and scattering-induced damping, the flux of fp emission is significantly lower than that of 2fp emission and is below the lower thresholds of typical Radio instruments. Moreover, the fp emission terminates at frequencies higher than the minimum simulated, and the 2fp emission appears to terminate at higher coronal altitudes that are not simulated because of computational limitations. Further simulations indicate that F-H pairs may exist under favorable conditions (e.g., generally, lower levels and larger length scales of the density fluctuations).
Eduard P Kontar - One of the best experts on this subject based on the ideXlab platform.
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fine structure of type iii Solar Radio Bursts from langmuir wave motion in turbulent plasma
Nature Astronomy, 2021Co-Authors: Hamish A S Reid, Eduard P KontarAbstract:The Sun frequently accelerates near-relativistic electron beams that travel out through the Solar corona and interplanetary space. Interacting with their plasma environment, these beams produce type III Radio Bursts—the brightest astrophysical Radio sources seen from Earth. The formation and motion of type III fine frequency structures is a puzzle, but is commonly believed to be related to plasma turbulence in the Solar corona and Solar wind. Combining a theoretical framework with kinetic simulations and high-resolution Radio type III observations using the Low-Frequency Array, we quantitatively show that the fine structures are caused by the moving intense clumps of Langmuir waves in a turbulent medium. Our results show how type III fine structure can be used to remotely analyse the intensity and spectrum of compressive density fluctuations, and can infer ambient temperatures in astrophysical plasma, substantially expanding the current diagnostic potential of Solar Radio emission. Fine frequency structures of type III Radio Bursts are caused by the moving of intense clumps of Langmuir waves in a turbulent medium. Analysis of these structures can infer properties of the coronal and Solar wind plasma and its density fluctuations.
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fine structure of type iii Solar Radio Bursts from langmuir wave motion in turbulent plasma
arXiv: Solar and Stellar Astrophysics, 2021Co-Authors: Hamish A S Reid, Eduard P KontarAbstract:The Sun frequently accelerates near-relativistic electron beams that travel out through the Solar corona and interplanetary space. Interacting with their plasma environment, these beams produce type III Radio Bursts, the brightest astrophysical Radio sources seen from the Earth. The formation and motion of type III fine frequency structures is a puzzle but is commonly believed to be related to plasma turbulence in the Solar corona and Solar wind. Combining a theoretical framework with kinetic simulations and high-resolution Radio type III observations using the Low Frequency Array, we quantitatively show that the fine structures are caused by the moving intense clumps of Langmuir waves in a turbulent medium. Our results show how type III fine structure can be used to remotely analyse the intensity and spectrum of compressive density fluctuations, and can infer ambient temperatures in astrophysical plasma, both significantly expanding the current diagnostic potential of Solar Radio emission.
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anisotropic Radio wave scattering and the interpretation of Solar Radio emission observations
The Astrophysical Journal, 2019Co-Authors: Eduard P Kontar, Xingyao Chen, Nicolina Chrysaphi, Natasha L S Jeffrey, Gordon A Emslie, V Krupar, Milan Maksimovic, Mykola GordovskyyAbstract:American Astronomical Society logo iop-2016.png A publishing partnership Anisotropic Radio-wave Scattering and the Interpretation of Solar Radio Emission Observations Eduard P. Kontar1, Xingyao Chen1,2, Nicolina Chrysaphi1, Natasha L. S. Jeffrey1,3, A. Gordon Emslie4, Vratislav Krupar5,6, Milan Maksimovic7, Mykola Gordovskyy8, and Philippa K. Browning9 Published 2019 October 17 • © 2019. The American Astronomical Society. All rights reserved. The Astrophysical Journal, Volume 884, Number 2 DownloadArticle PDF DownloadArticle ePub Figures References 206 Total downloads 11 citation on Dimensions. Turn on MathJax Get permission to re-use this article Share this article Share this content via email Share on Facebook Share on Twitter Share on Google+ Share on Mendeley Article information Abstract The observed properties (i.e., source size, source position, time duration, and decay time) of Solar Radio emission produced through plasma processes near the local plasma frequency, and hence the interpretation of Solar Radio Bursts, are strongly influenced by propagation effects in the inhomogeneous turbulent Solar corona. In this work, a 3D stochastic description of the propagation process is presented, based on the Fokker–Planck and Langevin equations of Radio-wave transport in a medium containing anisotropic electron density fluctuations. Using a numerical treatment based on this model, we investigate the characteristic source sizes and burst decay times for Type III Solar Radio Bursts. Comparison of the simulations with the observations of Solar Radio Bursts shows that predominantly perpendicular density fluctuations in the Solar corona are required, with an anisotropy factor of ~0.3 for sources observed at around 30 MHz. The simulations also demonstrate that the photons are isotropized near the region of primary emission, but the waves are then focused by large-scale refraction, leading to plasma Radio emission directivity that is characterized by a half width at half maximum of about 40° near 30 MHz. The results are applicable to various Solar Radio Bursts produced via plasma emission.
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anisotropic Radio wave scattering and the interpretation of Solar Radio emission observations
arXiv: Solar and Stellar Astrophysics, 2019Co-Authors: Eduard P Kontar, Xingyao Chen, Nicolina Chrysaphi, Natasha L S Jeffrey, Gordon A Emslie, V Krupar, Milan Maksimovic, Mykola GordovskyyAbstract:The observed properties (i.e., source size, source position, time duration, decay time) of Solar Radio emission produced through plasma processes near the local plasma frequency, and hence the interpretation of Solar Radio Bursts, are strongly influenced by propagation effects in the inhomogeneous turbulent Solar corona. In this work, a 3D stochastic description of the propagation process is presented, based on the Fokker-Planck and Langevin equations of Radio-wave transport in a medium containing anisotropic electron density fluctuations. Using a numerical treatment based on this model, we investigate the characteristic source sizes and burst decay times for Type III Solar Radio Bursts. Comparison of the simulations with the observations of Solar Radio Bursts shows that predominantly perpendicular density fluctuations in the Solar corona are required, with an anisotropy factor $\sim 0.3$ for sources observed at around 30~MHz. The simulations also demonstrate that the photons are isotropized near the region of primary emission, but the waves are then focused by large-scale refraction, leading to plasma Radio emission directivity that is characterized by a half-width-half-maximum of about 40~degrees near 30~MHz. The results are applicable to various Solar Radio Bursts produced via plasma emission.
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imaging spectroscopy of type u and j Solar Radio Bursts with lofar
Astronomy and Astrophysics, 2017Co-Authors: Hamish A S Reid, Eduard P KontarAbstract:Context. Radio U-Bursts and J-Bursts are signatures of electron beams propagating along magnetic loops confined to the corona. The more commonly observed type III Radio Bursts are signatures of electron beams propagating along magnetic loops that extend into interplanetary space. Given the prevalence of Solar magnetic flux to be closed in the corona, why type III Bursts are more frequently observed than U-Bursts or J-Bursts is an outstanding question. Aims. We use Low-Frequency Array (LOFAR) imaging spectroscopy between 30–80 MHz of low-frequency U-Bursts and J-Bursts, for the first time, to understand why electron beams travelling along coronal loops produce Radio emission less often. Radio burst observations provide information not only about the exciting electron beams but also about the structure of large coronal loops with densities that are too low for standard extreme ultraviolet (EUV) or X-ray analysis. Methods. We analysed LOFAR images of a sequence of two J-Bursts and one U-burst. The different Radio source positions were used to model the spatial structure of the guiding magnetic flux tube and then deduce the energy range of the exciting electron beams without the assumption of a standard density model. We also estimated the electron density along the magnetic flux rope and compared it to coronal models. Results. The Radio sources infer a magnetic loop that is 1 Solar radius in altitude with the highest frequency sources starting around 0.6 Solar radii. Electron velocities were found between 0.13 c and 0.24 c with the front of the electron beam travelling faster than the back of the electron beam. The velocities correspond to energy ranges within the beam from 0.7–11 keV to 0.7–43 keV. The density along the loop is higher than typical coronal density models and the density gradient is smaller. Conclusions. We found that a more restrictive range of accelerated beam and background plasma parameters can result in U-Bursts or J-Bursts, causing type III Bursts to be more frequently observed. The large instability distances required before Langmuir waves are produced by some electron beams, and the small magnitude of the background density gradients makes closed loops less facilitative for Radio emission than loops that extend into interplanetary space
R T J Mcateer - One of the best experts on this subject based on the ideXlab platform.
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observations of low frequency Solar Radio Bursts from the rosse Solar terrestrial observatory
Solar Physics, 2012Co-Authors: Pietro Zucca, C Monstein, Eoin P Carley, Joseph Mccauley, Peter T Gallagher, R T J McateerAbstract:The Rosse Solar-Terrestrial Observatory (RSTO; www.rosseobservatory.ie) was established at Birr Castle, Co. Offaly, Ireland (53°05′38.9″, 7°55′12.7″) in 2010 to study Solar Radio Bursts and the response of the Earth’s ionosphere and geomagnetic field. To date, three Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy in Transportable Observatory (CALLISTO) spectrometers have been installed, with the capability of observing in the frequency range of 10 – 870 MHz. The receivers are fed simultaneously by biconical and log-periodic antennas. Nominally, frequency spectra in the range of 10 – 400 MHz are obtained with four sweeps per second over 600 channels. Here, we describe the RSTO Solar Radio spectrometer set-up, and present dynamic spectra of samples of type II, III and IV Radio Bursts. In particular, we describe the fine-scale structure observed in type II Bursts, including band splitting and rapidly varying herringbone features.
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observations of low frequency Solar Radio Bursts from the rosse Solar terrestrial observatory
arXiv: Solar and Stellar Astrophysics, 2012Co-Authors: Pietro Zucca, C Monstein, Eoin P Carley, Joseph Mccauley, Peter T Gallagher, R T J McateerAbstract:The Rosse Solar-Terrestrial Observatory (RSTO; www.rosseobservatory.ie) was established at Birr Castle, Co. Offaly, Ireland (53 05'38.9", 7 55'12.7") in 2010 to study Solar Radio Bursts and the response of the Earth's ionosphere and geomagnetic field. To date, three Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory (CALLISTO) spectrometers have been installed, with the capability of observing in the frequency range 10-870 MHz. The receivers are fed simultaneously by biconical and log-periodic antennas. Nominally, frequency spectra in the range 10-400 MHz are obtained with 4 sweeps per second over 600 channels. Here, we describe the RSTO Solar Radio spectrometer set-up, and present dynamic spectra of a sample of Type II, III and IV Radio Bursts. In particular, we describe fine-scale structure observed in Type II Bursts, including band splitting and rapidly varying herringbone features.
C Monstein - One of the best experts on this subject based on the ideXlab platform.
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investigation into cme shock speed resulting from type ii Solar Radio Bursts
Solar Physics, 2020Co-Authors: F A M Pauzi, Zamri Zainal Abidin, S J Guo, Guannan Gao, L Dong, C MonsteinAbstract:An investigation into Type II Solar Radio Bursts was carried out to understand the frequency gap between fundamental and harmonic emissions of the Radio burst. This investigation focused on Type II Solar Radio Bursts with flares and coronal mass ejections by relating the separation between fundamental and harmonic emissions. We used the Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Spectrometers (CALLISTO) and a newly designed low-frequency antenna array. This article describes the proposed new instrument in terms of its antenna design, the bandpass testing of the antenna, the new system significance in studying Type II Solar Radio Bursts, and its comparison with other leading Radio Solar monitoring instruments. Upon setting up the new technology, the Radio-frequency interference of the observation site at the University of Malaya was shown to emphasize the suitability of the selected site. This article also shows the preliminary results of the proposed new instrument by reporting the detection of a Type III Solar Radio burst that was confirmed by CALLISTO. Moreover, it also includes the optimal observation design and strategies for future detections.
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automated detection of Solar Radio Bursts using a statistical method
Solar Physics, 2019Co-Authors: Dayal Singh, Prasad Subramanian, Sasikumar K Raja, R Ramesh, C MonsteinAbstract:Radio Bursts from the Solar corona can provide clues to forecast space-weather hazards. After recent technology advancements, regular monitoring of Radio Bursts has increased and large observational datasets are produced. Hence, manual identification and classification of them is a challenging task. In this article, we describe an algorithm to automatically identify Radio Bursts from dynamic Solar Radio spectrograms using a novel statistical method. We use e-CALLISTO (Compound Astronomical Low Cost Low Frequency Instrument for Spectroscopy and Transportable Observatory) Radio spectrometer data obtained at Gauribidanur Observatory near Bangalore in India during 2013 – 2014. We have studied the classifier performance using the receiver operating characteristics. Further, we analyze type III Bursts observed in the year 2014 and find that $75\%$ of the observed Bursts were below 200 MHz. Our analysis shows that the positions of flare sites, which are associated with the type III Bursts with upper frequency cutoff $\gtrsim200$ MHz originate close to the Solar disk center.
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automated detection of Solar Radio Bursts using a statistical method
arXiv: Solar and Stellar Astrophysics, 2019Co-Authors: Dayal Singh, Prasad Subramanian, Sasikumar K Raja, R Ramesh, C MonsteinAbstract:Radio Bursts from the Solar corona can provide clues to forecast space weather hazards. After recent technology advancements, regular monitoring of Radio Bursts has increased and large observational data sets are produced. Hence, manual identification and classification of them is a challenging task. In this paper, we describe an algorithm to automatically identify Radio Bursts from dynamic Solar Radio spectrograms using a novel statistical method. We used e-CALLISTO Radio spectrometer data observed at Gauribidanur observatory near Bangalore in India during 2013 - 2014. We have studied the classifier performance using the receiver operating characteristics. Further, we studied type III Bursts observed in the year 2014 and found that $75\%$ of the observed Bursts were below 200 MHz. Our analysis shows that the positions of the flare sites which are associated with the type III Bursts with upper-frequency cut-off $\gtrsim 200$ MHz originate close to the Solar disk center
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callisto spectrometer at iiser pune
arXiv: Instrumentation and Methods for Astrophysics, 2018Co-Authors: Sasikumar K Raja, Prasad Subramanian, S Ananthakrishnan, C MonsteinAbstract:A CALLISTO spectrometer to monitor Solar Radio transient emissions from $\approx 0.8-1.6~R_{\odot}$ (above photosphere) is installed at IISER, Pune, India (longitude $73^{\circ} 55'$ E and latitude $18^{\circ}31'$ N). In this paper, we illustrate the instrumental details (log-periodic dipole antenna and the receiver system) along with the recorded Solar Radio Bursts and Radio frequency interferences produced by the thunderstorms in the frequency range 45-870 MHz. We also developed the image processing pipelines using `sunpy' and in-house developed python library called `pycallisto'.
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observations of low frequency Solar Radio Bursts from the rosse Solar terrestrial observatory
Solar Physics, 2012Co-Authors: Pietro Zucca, C Monstein, Eoin P Carley, Joseph Mccauley, Peter T Gallagher, R T J McateerAbstract:The Rosse Solar-Terrestrial Observatory (RSTO; www.rosseobservatory.ie) was established at Birr Castle, Co. Offaly, Ireland (53°05′38.9″, 7°55′12.7″) in 2010 to study Solar Radio Bursts and the response of the Earth’s ionosphere and geomagnetic field. To date, three Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy in Transportable Observatory (CALLISTO) spectrometers have been installed, with the capability of observing in the frequency range of 10 – 870 MHz. The receivers are fed simultaneously by biconical and log-periodic antennas. Nominally, frequency spectra in the range of 10 – 400 MHz are obtained with four sweeps per second over 600 channels. Here, we describe the RSTO Solar Radio spectrometer set-up, and present dynamic spectra of samples of type II, III and IV Radio Bursts. In particular, we describe the fine-scale structure observed in type II Bursts, including band splitting and rapidly varying herringbone features.