Estimate of Plasma Temperatures Across a CME-Driven Shock from a Comparison Between EUV and Radio Data

Frassati, Federica; Mancuso, Salvatore; Бемпорад, А.

doi:10.1007/s11207-020-01686-0

Cited by 15 publications

(14 citation statements)

References 44 publications

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“…Although this is typically estimated using radio data by examining the difference in frequency between the fundamental and harmonic frequencies of the shock, the type II emission observed here corresponds to the leading edge of the CME-driven shock rather than the laterally driven global wave shock, and could therefore provide an inaccurate estimate of the shock strength. Instead, the density compression ratio can be estimated by examining the change in EUV intensity and/or DEM (see Kozarev et al 2011;Ma et al 2011;Muhr et al 2011;Zhukov 2011;Frassati et al 2019;Long et al 2019;Frassati et al 2020). The EUV density compression ratio (X) was estimated here using both the intensity ratio approach of Zhukov (2011) and the DEM ratio approach of Frassati et al (2019).…”

Section: Plasma Diagnosticsmentioning

confidence: 99%

“…While initially characterized using either wave or pseudo-wave interpretations (see Warmuth 2015), recent work (see Long et al 2017b;Downs et al 2021) has made it increasingly evident that these features can best be interpreted as large-amplitude waves/shocks. The multi-wavelength observations provided by SDO have also enabled plasma diagnostics of these perturbations, showing an adiabatic increase in both temperature and density associated with their passage through the solar corona (Vanninathan et al 2015;Long et al 2019;Frassati et al 2020). However, in each case, these results have underlined the very weak nature of these shocks, finding Mach numbers only slightly greater than 1 (e.g., Long et al 2015;Frassati et al 2020).…”

Section: Introductionmentioning

confidence: 99%

“…The multi-wavelength observations provided by SDO have also enabled plasma diagnostics of these perturbations, showing an adiabatic increase in both temperature and density associated with their passage through the solar corona (Vanninathan et al 2015;Long et al 2019;Frassati et al 2020). However, in each case, these results have underlined the very weak nature of these shocks, finding Mach numbers only slightly greater than 1 (e.g., Long et al 2015;Frassati et al 2020).…”

Section: Introductionmentioning

confidence: 99%

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Localized Acceleration of Energetic Particles by a Weak Shock in the Solar Corona

Long¹,

Reid²,

Valori

et al. 2021

ApJ

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Globally propagating shocks in the solar corona have long been studied to quantify their involvement in the acceleration of energetic particles. However, this work has tended to focus on large events associated with strong solar flares and fast coronal mass ejections (CMEs), where the waves are sufficiently fast to easily accelerate particles to high energies. Here we present observations of particle acceleration associated with a global wave event which occurred on 2011 October 1. Using differential emission measure analysis, the global shock wave was found to be incredibly weak, with an Alfvén Mach number of ∼1.008–1.013. Despite this, spatially resolved type iii radio emission was observed by the Nançay RadioHeliograph at distinct locations near the shock front, suggesting localized acceleration of energetic electrons. Further investigation using magnetic field extrapolation identified a fan structure beneath a magnetic null located above the source active region, with the erupting CME contained within this topological feature. We propose that a reconfiguration of the coronal magnetic field driven by the erupting CME enabled the weak shock to accelerate particles along field lines initially contained within the fan and subsequently opening into the heliosphere, producing the observed type iii emission. These results suggest that even weak global shocks in the solar corona can accelerate energetic particles via reconfiguration of the surrounding magnetic field.

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Section: Plasma Diagnosticsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Localized Acceleration of Energetic Particles by a Weak Shock in the Solar Corona

Long¹,

Reid²,

Valori

et al. 2021

ApJ

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“…Type II bursts and herringbones represent signatures of electron beams accelerated at the CME shock (e.g. Mann & Klassen 2005;Morosan et al 2019a;Frassati et al 2020). Type IV radio bursts are defined by a continuum emission at decimetric and metric wavelengths in dynamic spectra that can show stationary or moving sources, or both, that are emitted by various emission mechanisms (e.g.…”

Section: Introductionmentioning

confidence: 99%

Moving solar radio bursts and their association with coronal mass ejections

Morosan

Kumari

Kilpua

et al. 2021

A&A

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Context. Solar eruptions, such as coronal mass ejections (CMEs), are often accompanied by accelerated electrons that can in turn emit radiation at radio wavelengths. This radiation is observed as solar radio bursts. The main types of bursts associated with CMEs are type II and type IV bursts that can sometimes show movement in the direction of the CME expansion, either radially or laterally. However, the propagation of radio bursts with respect to CMEs has only been studied for individual events. Aims. Here, we perform a statistical study of 64 moving bursts with the aim to determine how often CMEs are accompanied by moving radio bursts. This is done in order to ascertain the usefulness of using radio images in estimating the early CME expansion. Methods. Using radio imaging from the Nançay Radioheliograph (NRH), we constructed a list of moving radio bursts, defined as bursts that move across the plane of sky at a single frequency. We define their association with CMEs and the properties of associated CMEs using white-light coronagraph observations. We also determine their connection to classical type II and type IV radio burst categorisation. Results. We find that just over a quarter of type II and half of type IV bursts that occurred during the NRH observing windows in Solar Cycle 24 are accompanied by moving radio emission. All but one of the moving radio bursts are associated with white–light CMEs and the majority of moving bursts (90%) are associated with wide CMEs (> 60° in width). In particular, all but one of the moving bursts corresponding to type IIs are associated with wide CMEs; however, and unexpectedly, the majority of type II moving bursts are associated with slow white–light CMEs (< 500 km s−1). On the other hand, the majority of moving type IV bursts are associated with fast CMEs (> 500 km s−1). Conclusions. The observations presented here show that moving radio sources are almost exclusively associated with CMEs. The majority of events are also associated with wide CMEs, indicating that strong lateral expansion during the early stages of the eruption may play a key role in the occurrence of the radio emission observed.

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Section: Introductionmentioning

confidence: 99%

The nature and origin of moving solar radio bursts associated with coronal mass ejections

Morosan¹,

Kilpua²,

Palmerio³

et al. 2020

Preprint

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Flares and coronal mass ejections (CMEs) from the Sun are the most powerful and spectacular explosions in the solar system, capable of releasing vast amounts of magnetic energy over relatively short periods of time. These phenomena are often associated with particle acceleration processes that are often observed directly by spacecraft here at Earth. At the Sun, there are no direct methods of measuring these particles, which is necessary to predict their origin and propagation direction through the heliosphere. However, accelerated particles, in particular fast electrons, can generate emission at radio wavelengths through various mechanisms. Here, we exploit radio observations of Type II and Type IV radio bursts that accompany CME eruptions, in particular those radio bursts that show movement with the CME expansion in the low solar corona. Using multi-wavelength analysis, reconstruction of the radio emission and CME in three dimensions, we aim to determine the sources and locations of electron acceleration responsible for the Type II and Type IV emission in relation to the CME location and propagation. Such studies are important to&#160;understand CMEs and the sources of electron acceleration to ultimately improve the lead time to these impacts here at Earth.

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Estimate of Plasma Temperatures Across a CME-Driven Shock from a Comparison Between EUV and Radio Data

Cited by 15 publications

References 44 publications

Localized Acceleration of Energetic Particles by a Weak Shock in the Solar Corona

Localized Acceleration of Energetic Particles by a Weak Shock in the Solar Corona

Moving solar radio bursts and their association with coronal mass ejections

The nature and origin of moving solar radio bursts associated with coronal mass ejections

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