Polarization Characteristics of Zebra Patterns in Type IV Solar Radio Bursts

Kaneda, Kazutaka; Misawa, Hiroaki; Iwai, Kazumasa; Tsuchiya, F.; Obara, Takao; Katoh, Yutai; Masuda, S.

doi:10.3847/1538-4357/aa74c1

Cited by 11 publications

(9 citation statements)

References 39 publications

(70 reference statements)

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“…The induced plasma emissions at H and F bands are obtained through nonlinear wave-wave interaction, consistent with our earlier study (Ni et al 2020). The H emission dominates over the F emission in intensity by about 2 orders in magnitude, this indicates that the ZPs arise from the H emission, rather than the F emission as assumed in many studies (e.g., Zlotnik et al 2014;Chernov 2015;Kaneda et al 2017). The peak-valley contrast of intensity of the H emission is found to be ∼ 4, consistent with some observational reports.…”

Section: Summary and Discussionsupporting

confidence: 89%

PIC Simulation of Double Plasma Resonance and Zebra Pattern of Solar Radio Bursts

Li,

Chen,

et al. 2021

Preprint

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Latest study reports that plasma emission can be generated by energetic electrons of DGH distribution via the electron cyclotron maser instability (ECMI) in plasmas characterized by a large ratio of plasma oscillation frequency to electron gyro-frequency (ω pe /Ω ce ). In this study, on the basis of the ECMI-plasma emission mechanism, we examine the double plasma resonance (DPR) effect and the corresponding plasma emission at both harmonic (H) and fundamental (F) bands using PIC simulations with various ω pe /Ω ce . This allows us to directly simulate the feature of zebra pattern (ZP) observed in solar radio bursts for the first time. We find that (1) the simulations reproduce the DPR effect nicely for the upper hybrid (UH) and Z modes, as seen from their variation of intensity and linear growth rate with ω pe /Ω ce , (2) the intensity of the H emission is stronger than that of the F emission by ∼ 2 orders of magnitude and vary periodically with increasing ω pe /Ω ce , while the F emission is too weak to be significant, therefore we suggest that it is the H emission accounting for solar ZPs, (3) the peak-valley contrast of the total intensity of H is ∼ 4, and the peak lies around integer values of ω pe /Ω ce (= 10 and 11) for the present parameter setup. We also evaluate the effect of energy of energetic electrons on the characteristics of ECMI-excited waves and plasma radiation.The study provides novel insight on the physical origin of ZPs of solar radio bursts.

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Section: Summary and Discussionsupporting

confidence: 89%

PIC Simulation of Double Plasma Resonance and Zebra Pattern of Solar Radio Bursts

Li,

Chen,

et al. 2021

Preprint

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“…The reason for this remains an open question, but a common explanation is that scattering of the radio emission by other wave modes or by sharp density gradients tends to have a depolarizing effect (e.g. Wentzel, Zlobec, and Messerotti, 1986;Melrose, 1989Melrose, , 2006Kaneda et al, 2017). The polarization fraction of harmonic [2f p ] emission is more complicated because it depends on the angular distribution of the Langmuir waves.…”

Section: Introductionmentioning

confidence: 99%

The Low-Frequency Solar Corona in Circular Polarization

et al. 2019

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We present spectropolarimetric imaging observations of the solar corona at low frequencies (80 -240 MHz) using the Murchison Widefield Array (MWA). These images are the first of their kind, and we introduce an algorithm to mitigate an instrumental artefact by which the total intensity signal contaminates the polarimetric images due to calibration errors. We then survey the range of circular polarization (Stokes V ) features detected in over 100 observing runs near solar maximum during quiescent periods. First, we detect around 700 compact polarized sources across our dataset with polarization fractions ranging from less than 0.5 % to nearly 100 %. These sources exhibit a positive correlation between polarization fraction and total intensity, and we interpret them as a continuum of plasma emission noise storm (Type I burst) continua sources associated with active regions. Second, we report a characteristic "bullseye" structure observed for many low-latitude coronal holes in which a central polarized component is surrounded by a ring of the opposite sense. The central component does not match the sign expected from thermal bremsstrahlung emission, and we speculate that propagation effects or an alternative emission mechanism may be responsible. Third, we show that the large-scale polarimetric structure at our lowest frequencies is reasonably well-correlated with the line-of-sight (LOS) magnetic field component inferred from a global potential field source surface (PFSS) model. The boundaries between opposite circular polarization signs are generally aligned with polarity inversion lines in the model at a height roughly corresponding to that of the radio limb. This is not true at our highest frequencies, however, where the LOS magnetic field direction and polarization sign are often not straightforwardly correlated.

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“…While type IV radio bursts are known to be radiated from energetic electrons trapped in closed magnetic loops of the solar corona through the synchrotron emission process, fine spectral structures are embedded on it. Kaneda et al [2015;2017] found a zebra pattern (ZP) in a type IV solar radio burst and investigated the polarization characteristics. Analyzing highly resolved spectral and polarization data revealed the frequency dependence of the degree of circular polarization and the delay between two polarized components for the first time.…”

Section: Specification Of Amateras and On-line Databasementioning

confidence: 99%

Database of solar radio bursts observed by solar radio spectro-polarimeter AMATERAS

Cecconi

2018

Planetary Radio Emissions Viii

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Observations of solar radio bursts is a useful tool to study non-thermal electron acceleration and the plasma environment in the solar corona. The radio bursts in a frequency range from 150 to 500 MHz with fine temporal and spectral resolutions (10 ms and 61 kHz) have been observed with the AMATERAS radio spectropolarimeter installed at the Iitate Planetary Radio Telescope since 2010. Here we review results obtained from the AMATERAS observation and introduce the database which is open to the public. The AMATERAS receiver consists of a wideband and low-noise front-end receiver and a digital spectrometer. Both right and left-hand polarized components are simultaneously observed. The combination of a large aperture area of the telescope and the digital receiver enables us to observe the radio burst with high dynamic range and fine spectral resolution. After a daily observation of the Sun, a data processing pipeline generates low and high resolution data sets. The low resolution data with reduced resolutions of 1 s, 1 MHz, and 8 bits is converted to the FITS format and distributed through the AMATERAS Data Center. Quick look (PNG format) and meta-data of the FITS-format file are registered to the Virtual European Solar and Planetary Access (VESPA) and Interuniversity Upper atmosphere Global Observation NETwork (IUGONET) database. The high resolution data set has fine resolutions of 10 ms and 61 kHz, but the dynamic range is reduced to be 8 or 16 bits depending on the intensity of the radio burst observed. It is currently provided on request basis.

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Polarization Characteristics of Zebra Patterns in Type IV Solar Radio Bursts

Cited by 11 publications

References 39 publications

PIC Simulation of Double Plasma Resonance and Zebra Pattern of Solar Radio Bursts

PIC Simulation of Double Plasma Resonance and Zebra Pattern of Solar Radio Bursts

The Low-Frequency Solar Corona in Circular Polarization

Database of solar radio bursts observed by solar radio spectro-polarimeter AMATERAS

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