Circular Polarization Observations of Type II Solar Radio Bursts and the Coronal Magnetic Field

Ramesh, R.; Kathiravan, C.; Chellasamy, E. Ebenezer

doi:10.3847/1538-4357/ac6f05

Cited by 8 publications

(10 citation statements)

References 82 publications

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“…Recently, Ramesh et al (2022) imaged the 80 MHz harmonic component of TII(1a) at ≈ 06:38 UT, which corresponds to the end of the inferred injection time of the low-energy electrons. The source of TII(1a) according to this study was located close to the southwest periphery of the flaring active region.…”

Section: Radio Observationsmentioning

confidence: 99%

Multiple injections of energetic electrons associated with the flare/CME event on 9 October 2021

Jebaraj¹,

Koulooumvakos²,

Dresing³

et al. 2023

Preprint

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Context. We study the solar energetic particle (SEP) event observed on 9 October 2021, by multiple spacecraft including Solar Orbiter (SolO). The event was associated with an M1.6 flare, a coronal mass ejection (CME) and a shock wave. During the event, high-energy protons and electrons were recorded by multiple instruments located within a narrow longitudinal cone.Aims. An interesting aspect of the event was the multi-stage particle energization during the flare impulsive phase and also what appears to be a separate phase of electron acceleration detected at SolO after the flare maximum. We aim to investigate and identify the multiple sources of energetic electron acceleration. Methods. We utilize SEP electron observations from the Energetic Particle Detector (EPD) and hard X-ray (HXR) observations from the Spectrometer/Telescope for Imaging X-rays (STIX) on-board SolO, in combination with radio observations at a broad frequency range. We focus on establishing an association between the energetic electrons and the different HXR and radio emissions associated with the multiple acceleration episodes. Results. We have found that the flare was able to accelerate electrons for at least 20 minutes during the nonthermal phase observed in the form of five discrete HXR pulses. We also show evidence that the shock wave has contributed to the electron acceleration during and after the impulsive flare phase. The detailed analysis of EPD electron data shows that there was a time difference in the release of low-and high-energy electrons, with the high-energy release delayed. Also, the observed electron anisotropy characteristics suggest different connectivity during the two phases of acceleration.

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Section: Radio Observationsmentioning

confidence: 99%

Multiple injections of energetic electrons associated with the flare/CME event on 9 October 2021

Jebaraj¹,

Koulooumvakos²,

Dresing³

et al. 2023

Preprint

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“…Among these di erent types of radio bursts, type-II radio bursts are directly linked to coronal shocks either generated by CMEs or other eruptive events (Ma & Chen, 2020). Type-II radio bursts appear as slowly drifting features in the dynamic spectrum (Figure 1) and their brightness temperature (T B ) can vary between 10 6 − 10 12 K. Non-imaging polarization observations (e.g., Ramesh et al, 2022, etc.) and band-splitting (e.g., Vrsnak, B. et al, 2001Cho et al, 2007;Mahrous et al, 2018, etc.…”

Section: Space-weather Observable At Radio Wavelengthsmentioning

confidence: 99%

Space Weather Research using Spectropolarimetric Radio Imaging Combined With Aditya-L1 and PUNCH Missions

Kansabanik,

Mondal,

Oberoi

et al. 2023

Preprint

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Low-frequency radio observations have been expected to serve as a powerful tool for Space Weather (SW) observations for decades. Radio observations are sensitive to a wide range of SW-related observations ranging from emissions from coronal mass ejections (CMEs) to the solar wind. Ground-based radio observatories allow one gathering of high-sensitivity data at high time and spectral resolution for an extended period, which remains a challenge for most space-based observatories. While radio techniques like Interplanetary Scintillation (IPS) are well established, radio imaging studies have remained technically challenging. This is now changing with the con uence of data from instruments, like the Murchison Wide eld Array (MWA), and robust unsupervised analysis pipelines. This pipeline delivers full Stokes radio images with unprecedented delity and dynamic range. This will serve as a powerful tool for coronal and heliospheric studies. We present the recent developments and achievements to measure the magnetic elds of the CME plasma and shock front at coronal heights and also share the current status of the objective to measure the heliospheric Faraday rotation towards numerous background linearly polarised radio sources with the Sun in the eld of view. We envision that in the coming years, the availability of new-generation radio instruments combined with the Aditya-L1 and PUNCH mission will mark the start of a new era in Space Weather modeling and prediction.

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“…In the case of harmonic plasma emission, the associated B can be estimated in a relatively simple manner (see, e.g., Melrose et al 1980;Zlotnik 1981). Several such estimates of B using observations of weak circularly polarized emission from harmonic type II bursts are there in the literature (Hariharan et al 2014;Kumari et al 2017aKumari et al , 2019Ramesh et al 2022b;Ramesh & Kathiravan 2022c). The abovementioned work by various authors indicate that power spectral density (PSD) and/ or B are useful parameters to compare successive type II bursts.…”

Section: Introductionmentioning

confidence: 99%

Solar Coronal Density Turbulence and Magnetic Field Strength at the Source Regions of Two Successive Metric Type II Radio Bursts

Ramesh

Kathiravan

Kumari

2023

ApJ

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We report spectral and polarimeter observations of two weak, low-frequency (≈85–60 MHz) solar coronal type II radio bursts that occurred on 2020 May 29 within a time interval ≈2 minutes. The bursts had fine structures, and were due to harmonic plasma emission. Our analysis indicates that the magnetohydrodynamic shocks responsible for the first and second type II bursts were generated by the leading edge (LE) of an extreme-ultraviolet flux rope/coronal mass ejection (CME) and interaction of its flank with a neighboring coronal structure, respectively. The CME deflected from the radial direction by ≈25° during propagation in the near-Sun corona. The estimated power spectral density and magnetic field strength (B) near the location of the first burst at heliocentric distance r ≈ 1.35 R ⊙ are ≈2 × 10−3 W2m and ≈1.8 G, respectively. The corresponding values for the second burst at the same r are ≈10−3 W2m and ≈0.9 G. The significant spatial scales of the coronal turbulence at the location of the two type II bursts are ≈62–1 Mm. Our conclusions from the present work are that the turbulence and magnetic field strength in the coronal region near the CME LE are higher compared to the corresponding values close to its flank. The derived estimates of the two parameters correspond to the same r for both the CME LE and its flank, with a delay of ≈2 minutes for the latter.

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Circular Polarization Observations of Type II Solar Radio Bursts and the Coronal Magnetic Field

Cited by 8 publications

References 82 publications

Multiple injections of energetic electrons associated with the flare/CME event on 9 October 2021

Multiple injections of energetic electrons associated with the flare/CME event on 9 October 2021

Space Weather Research using Spectropolarimetric Radio Imaging Combined With Aditya-L1 and PUNCH Missions

Solar Coronal Density Turbulence and Magnetic Field Strength at the Source Regions of Two Successive Metric Type II Radio Bursts

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