Particle beams as a source of noise storm depression?

Auraß, H.; Böhme, A.; Karlický, M.

doi:10.1007/bf00156776

Cited by 11 publications

(4 citation statements)

References 7 publications

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“…These events probably belong to the category of picoflares mentioned earlier. The possibility of fluctuations in the amplitude of the type I bursts in Figures 1 and 2 as well as the other events in Table 1, due to either a screening of the radio source region (by hot and dense evaporated chromospheric material) in the aftermath of flare onset as pointed out by Böhme & Krüger (1982), Aurass et al (1990), and Zaitsev et al (1994 or formation/deformation of reconnection regions (from where the type I emission is generated) after/before CMEs as shown by Chertok et al (2001) and Iwai et al (2012), can be ruled out since the events reported in the present work were not accompanied by either CMEs or Hα/X-ray flares, as mentioned earlier. We verified this using the previously mentioned online resources 3 and the SGD reports.…”

Section: Results and Analysismentioning

confidence: 90%

Low-Frequency Radio Observations of Picoflare Category Energy Releases in the Solar Atmosphere

Ramesh

Raja

Kathiravan

et al. 2012

ApJ

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We report low-frequency (80 MHz) radio observations of circularly polarized non-thermal type I radio bursts ("noise storms") in the solar corona whose estimated energy is ∼10 21 erg. These are the weakest energy release events reported to date in the solar atmosphere. The plot of the distribution of the number of bursts (dN) versus their corresponding peak flux density in the range S to S + dS shows a power-law behavior, i.e., dN ∝ S γ dS. The power-law index γ is in the range −2.2 to −2.7 for the events reported in the present work. The present results provide independent observational evidence for the existence of picoflare category energy releases in the solar atmosphere which are yet to be explored.

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Section: Results and Analysismentioning

confidence: 90%

Low-Frequency Radio Observations of Picoflare Category Energy Releases in the Solar Atmosphere

Ramesh

Raja

Kathiravan

et al. 2012

ApJ

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“…Type-I bursts are usually associated with active regions. They are sometimes enhanced or modulated by flares and CMEs (Aurass et al 1990(Aurass et al , 1993Chertok et al 2001;Iwai et al 2012a). The emissions of type-I bursts are usually sporadic (less than 1 s) and the emission is O-mode (e.g., Krucker et al, 1995).…”

Section: Growth Rate Of the Type-i Burstmentioning

confidence: 99%

“…No flares larger than C class (Watanabe et al 2012) or coronal mass ejections (CMEs) were reported during the observational periods on January 16 and 26 1 . Hence, the type-I modulation by flares (Aurass et al 1990(Aurass et al , 1993 or CMEs (Chertok et al 2001;Iwai et al 2012a) can be neglected. A CME was observed during the observational period on January 23.…”

Section: Introductionmentioning

confidence: 99%

Spectral Structures and Their Generation Mechanisms for Solar Radio Type-I Bursts

Iwai

Miyoshi

Masuda

et al. 2014

ApJ

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The fine spectral structures of solar radio type-I bursts were observed by the solar radio telescope AMATERAS. The spectral characteristics, such as the peak flux, duration, and bandwidth, of the individual burst elements were satisfactorily detected by the highly resolved spectral data of AMATEAS with the burst detection algorithm that is improved in this study. The peak flux of the type-I bursts followed a power-law distribution with a spectral index of 2.9-3.3, whereas their duration and bandwidth were distributed more exponentially. There were almost no correlations between the peak flux, duration, and bandwidth. That means there were no similarity shapes in the burst spectral structures. We defined the growth rate of a burst as the ratio between its peak flux and duration. There was a strong correlation between the growth rate and peak flux. These results suggest that the free energy of type-I bursts that is originally generated by non-thermal electrons is modulated in the subsequent stages of the generation of non-thermal electrons, such as plasma wave generation, radio wave emissions, and propagation. The variation of the time scale of the growth rate is significantly larger than that of the coronal environments. These results can be explained by the situation that the source region may have the inhomogeneity of an ambient plasma environment, such as the boundary of open and closed field lines, and the superposition of entire emitted bursts was observed by the spectrometer.

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“…While these storms are known to occur over very long timescales (e.g. Del Zanna et al 2011), they have also been observed to react rapidly to flare and coronal mass ejection (CME) activity (Aurass et al 1990;Kathiravan et al 2007;Iwai et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional magnetic reconnection in a collapsing coronal loop system

O'Flannagain

Maloney

Gallagher

et al. 2018

A&A

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Context. Magnetic reconnection is believed to be the primary mechanism by which non-potential energy stored in coronal magnetic fields is rapidly released during solar eruptive events. Unfortunately, owing to the small spatial scales on which reconnection is thought to occur, it is not directly observable in the solar corona. However, larger scale processes, such as associated inflow and outflow, and signatures of accelerated particles have been put forward as evidence of reconnection. Aims. Using a combination of observations we explore the origin of a persistent Type I radio source that accompanies a coronal X-shaped structure during its passage across the disk. Of particular interest is the time range around a partial collapse of the structure that is associated with inflow, outflow, and signatures of particle acceleration. Methods. Imaging radio observations from the Nançay Radioheliograph were used to localise the radio source. Solar Dynamics Observatory (SDO) AIA extreme ultraviolet (EUV) observations from the same time period were analysed, looking for evidence of inflows and outflows. Further mpole magnetic reconstructions using SDO HMI observations allowed the magnetic connectivity associated with the radio source to be determined. Results. The Type I radio source was well aligned with a magnetic separator identified in the extrapolations. During the partial collapse, gradual (1 km/s) and fast (5 km/s) inflow phases and fast (30 km/s) and rapid (80-100 km/s) outflow phases were observed, resulting in an estimated reconnection rate of ∼0.06. The radio source brightening and dimming was found to be co-temporal with increased soft x-ray emission in both Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Geostationary Operational Environmental Satellite (GOES). Conclusions. We interpret the brightening and dimming of the radio emission as evidence for accelerated electrons in the reconnection region responding to a gradual fall and rapid rise in electric drift velocity, in response to the inflowing and outflowing field lines. These results present a comprehensive example of 3D null-point reconnection.

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Particle beams as a source of noise storm depression?

Cited by 11 publications

References 7 publications

Low-Frequency Radio Observations of Picoflare Category Energy Releases in the Solar Atmosphere

Low-Frequency Radio Observations of Picoflare Category Energy Releases in the Solar Atmosphere

Spectral Structures and Their Generation Mechanisms for Solar Radio Type-I Bursts

Three-dimensional magnetic reconnection in a collapsing coronal loop system

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