Metric observations of transient, quasi-periodic radio emission from the solar corona in association with a “halo” CME and an “EIT wave” event

Ramesh, R.; Kathiravan, C.; Narayanan, A. Satya; Ebenezer, E.

doi:10.1051/0004-6361:20030019

Cited by 29 publications

(9 citation statements)

References 30 publications

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“…However, their spectral characteristics and polarization were not consistent with such interpretation. Thermal emission from CMEs has also been reported at 109 MHz by Kathiravan et al (2002) and Ramesh et al (2003) (Gauribidanur Radioheliograph observations). The thermal free-free CME emission, when detected, can be used for the calculation of the CME mass.…”

Section: Imaging Observations Of Flares and Cmesmentioning

confidence: 71%

Incoherent Solar Radio Emission

Nindos

2020

Front. Astron. Space Sci.

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Incoherent solar radio radiation comes from the free-free, gyroresonance, and gyrosynchrotron emission mechanisms. Free-free is primarily produced from Coulomb collisions between thermal electrons and ions. Gyroresonance and gyrosynchrotron result from the acceleration of low-energy electrons and mildly relativistic electrons, respectively, in the presence of a magnetic field. In the non-flaring Sun, free-free is the dominant emission mechanism with the exception of regions of strong magnetic fields which emit gyroresonance at microwaves. Due to its ubiquitous presence, free-free emission can be used to probe the non-flaring solar atmosphere above temperature minimum. Gyroresonance opacity depends strongly on the magnetic field strength and orientation; hence it provides a unique tool for the estimation of coronal magnetic fields. Gyrosynchrotron is the primary emission mechanism in flares at frequencies higher than 1-2 GHz and depends on the properties of both the magnetic field and the accelerated electrons, as well as the properties of the ambient plasma. In this paper we discuss in detail the above mechanisms and their diagnostic potential.

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Section: Imaging Observations Of Flares and Cmesmentioning

confidence: 71%

Incoherent Solar Radio Emission

Nindos

2020

Front. Astron. Space Sci.

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“…The primary radio bursts associated with coronal waves are metric Type II bursts. It has been noted that the majority of flares of any magnitude range are not necessarily accompanied by Type II activity, implying that an additional condition must be present for the bursts to form (Roberts 1959). With the discovery of Moreton waves (Moreton 1960), it was noticed that there was a strong correlation between metric Type II radio bursts and Moreton waves (Kai 1970).…”

Section: Coronal Bright Fronts and Radio Emissionmentioning

confidence: 99%

Large-scale Bright Fronts in the Solar Corona: A Review of “EIT waves”

2010

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"EIT waves" are large-scale coronal bright fronts (CBFs) that were first observed in 195Å images obtained using the Extreme-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO). Commonly called "EIT waves", CBFs typically appear as diffuse fronts that propagate pseudo-radially across the solar disk at velocities of 100-700 km s −1 with front widths of 50-100 Mm. As their speed is greater than the quiet coronal sound speed (c s ≤200 km s −1 ) and comparable to the local Alfvén speed (v A ≤1000 km s −1 ), they were initially interpreted as fast-mode magnetoacoustic waves (v f = (c 2 s + v 2 A ) 1/2 ). Their propagation is now known to be modified by regions where the magnetosonic sound speed varies, such as active regions and coronal holes, but there is also evidence for stationary CBFs at coronal hole boundaries. The latter has led to the suggestion that they may be a manifestation of a processes such as Joule heating or magnetic reconnection, rather than a wave-related phenomena. While the general morphological and kinematic properties of CBFs and their association with coronal mass ejections have now been well described, there are many questions regarding their excitation and propagation. In particular, the theoretical interpretation of these enigmatic events as magnetohydrodynamic waves or due to changes in magnetic topology remains the topic of much debate.

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“…That both the CMEs and streamers are primarily density enhancements in the solar atmosphere could be a reason for this; 5) for a similar type IVm burst event explained on the basis of optically thin gyro-synchrotron emission from the mildly relativistic non-thermal electrons in the magnetic field of the associated CME core,Tun & Vourlidas (2013) showed that B ≈ 5 − 15 G at r ≈ 1.7 R ⊙ ; 6) type IVm radio bursts associated with the 'leg' of the corresponding CMEs and generated due to second harmonic plasma emission from the enhanced electron density there indicate that B ≈ 4 G at r ≈ 1.6 R ⊙. Considering that the coronal magnetic field associated with the active regions have a range of values(Dulk & McLean 1978;Ramesh et al 2003Ramesh et al , 2011bSasikumar & Ramesh 2013), the different estimates mentioned above can be regarded as reasonable. With measurements of the coronal magnetic field being very limited, particularly in close association with a CME, the results indicate that contemporaneous whitelight and radio observations of the solar corona close to the Sun (r 2 R ⊙ ) are desirable to understand the CMEs and the associated magnetic field.It is a pleasure to thank the staff of the Gauribidanur observatory for their help in observations, maintenance of the antenna and receiver systems there.…”

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confidence: 99%

An Estimate of the Magnetic Field Strength Associated With a Solar Coronal Mass Ejection From Low Frequency Radio Observations

Raja

Ramesh

Hariharan

et al. 2014

ApJ

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We report ground based, low frequency heliograph (80 MHz), spectral MHz) and polarimeter (80 and 40 MHz) observations of drifting, non-thermal radio continuum associated with the 'halo' coronal mass ejection (CME) that occurred in the solar atmosphere on 2013 March 15. The magnetic field strengths (B) near the radio source were estimated to be B ≈ 2.2 ± 0.4 G at 80 MHz and B ≈ 1.4±0.2 G at 40 MHz. The corresponding radial distances (r) are r ≈ 1.9 R ⊙ (80 MHz) and r ≈ 2.2 R ⊙ (40 MHz). Subject headings: Sun -activity: Sun -flares: Sun -corona: Sun -radio radiation: Sun: coronal mass ejections (CMEs): Sun -magnetic topologythe referee for his/her comments that helped to bring out the results more clearly. The SOHO data are produced by a consortium of the Naval Research Laboratory (USA),

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Metric observations of transient, quasi-periodic radio emission from the solar corona in association with a “halo” CME and an “EIT wave” event

Cited by 29 publications

References 30 publications

Incoherent Solar Radio Emission

Incoherent Solar Radio Emission

Large-scale Bright Fronts in the Solar Corona: A Review of “EIT waves”

An Estimate of the Magnetic Field Strength Associated With a Solar Coronal Mass Ejection From Low Frequency Radio Observations

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