Challenging Some Contemporary Views of Coronal Mass Ejections. Ii. The Case for Absent Filaments

Howard, T. A.; DeForest, C. E.; Schneck, Una; Alden, C. R.

doi:10.3847/1538-4357/834/1/86

Cited by 53 publications

(52 citation statements)

References 71 publications

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“…According to Vourlidas et al (2013), the "classical three part CME" morphology visible in white-light coronagraph images (Illing and Hundhausen, 1985) can be updated to a "five-part CME" structure. In the traditional view, the CME consists of a dark cavity, which is surrounded by a bright frontal loop, and an embedded bright core that is generally assumed to be an erupting prominence (however, for different interpretations see Howard et al, 2017 andVeronig et al, 2018). Vourlidas et al (2013) added a two-front morphology, where the outer bright loop is preceded by a faint sharp front and a broad region of diffuse emission.…”

Section: Source Region Locations and Association With Filament Eruptionsmentioning

confidence: 99%

Sun-to-Earth Observations and Characteristics of Isolated Earth-Impacting Interplanetary Coronal Mass Ejections During 2008 – 2014

Maričić¹,

Vršnak

Veronig

et al. 2020

Sol Phys

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A sample of isolated Earth-impacting interplanetary coronal mass ejections (ICMEs) that occurred in the period January 2008 to August 2014 is analysed in order to study in detail the ICME in situ signatures with respect to the type of filament eruption related to the corresponding CME. Observations from different vantage points provided by SOHO, STEREO-A and STEREO-B are used to determine for each CME under study whether it is Earth directed or not. For Earth-directed CMEs, a kinematical study was performed using the STEREO-A,B COR1 and COR2 coronagraphs and the Heliospheric Imagers HI1, to estimate the CME arrival time at 1 AU and to link the CMEs with the corresponding in situ solar wind counterparts. Based on the extrapolated CME kinematics, we identified interacting CMEs, which were excluded from further analysis. Applying this approach, a set of 31 isolated Earth-impacting CMEs was unambiguously identified and related to the in situ measurements recorded by the Wind spacecraft. We classified the events into subsets with respect to the CME source location as well as with respect to the type of the associated filament eruption. Hence, the events are divided into three subsamples: active region (AR) CMEs, disappearing filament (DSF) CMEs, and stealthy CMEs. The related three groups of ICMEs were further divided into two subsets: magnetic obstacle (MO) events (out of which four were stealthy), covering ICMEs that at least partly expose characteristics of flux ropes, and ejecta (EJ) events, not showing such characteristics. In this way, 14 MO-ICMEs and 17 EJ-ICMES were identified. The solar source regions of the non-stealthy MO-ICMEs are found to be located predominantly (9/10; 90%) within ±30°from the solar central meridian, whereas EJ-ICMEs originate predominantly (16/17; 94%) from source regions that are outside ±30°. In the next step, MO-events were analysed in more detail, considering the magnetic field strengths and the plasma characteristics in three different segments of the ICMEs, defined as the turbulent sheath (TS), the frontal region (FR), and the MO itself. The analysis revealed various well-defined correlations for AR, DSF, and stealthy ICMEs, which we interpreted considering basic physical concepts. Our results support the hypothesis that ICMEs show different signatures depending on the in situ spacecraft trajectory, in terms of apex versus flank hits.

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Section: Source Region Locations and Association With Filament Eruptionsmentioning

confidence: 99%

Sun-to-Earth Observations and Characteristics of Isolated Earth-Impacting Interplanetary Coronal Mass Ejections During 2008 – 2014

Maričić¹,

Vršnak

Veronig

et al. 2020

Sol Phys

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“…The core of the structure is typically considered to be filament material that was supported by the magnetic field above the system's photospheric polarity inversion line (PIL) prior to the eruption. While long-standing, it is worth noting recent work by Howard et al (2017) questions the filament-core connection for some events. Flux ropes have often been invoked as a theoretical construction corresponding to the pre-event plasma cavity, which contains the free energy necessary to drive CMEs (e.g., Low 2001;Török and Kliem 2003;Fuller et al 2008).…”

Section: Icmes and Magnetic Cloudsmentioning

confidence: 99%

The Physical Processes of CME/ICME Evolution

et al. 2017

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As observed in Thomson-scattered white light, coronal mass ejections (CMEs) are manifest as large-scale expulsions of plasma magnetically driven from the corona in the most energetic eruptions from the Sun. It remains a tantalizing mystery as to how these erupting magnetic fields evolve to form the complex structures we observe in the solar wind at Earth. Here, we strive to provide a fresh perspective on the post-eruption and interplanetary evolution of CMEs, focusing on the physical processes that define the many complex interactions of the ejected plasma with its surroundings as it departs the corona and propagates through the heliosphere. We summarize the ways CMEs and their interplanetary CMEs (ICMEs) are rotated, reconfigured, deformed, deflected, decelerated and disguised during their journey through the solar wind. This study then leads to consideration of how structures originating in coronal eruptions can be connected to their far removed interplanetary counterparts. Given that ICMEs are the drivers of most geomagnetic storms (and the sole driver of extreme storms), this work provides a guide to the processes that must be considered in making space weather forecasts from remote observations of the corona.

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“…A coronal mass ejection (CME) is generally understood to comprise a magnetic flux rope, which at some time starts to rise into the high corona (e.g. Démoulin & Aulanier 2010;Howard et al 2017;Song et al 2019). It leaves behind a stressed magnetic field that will re-arrange itself over several hours.…”

Section: Introductionmentioning

confidence: 99%

Polarisation and source structure of solar stationary type IV radio bursts

Salas-Matamoros

Klein

2020

A&A

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The reconfiguration of the magnetic field during and after a coronal mass ejection (CME) may be accompanied by radio emission from non-thermal electrons. In particular, stationary type IV bursts (also called storm continua) are emitted by electrons in closed magnetic configurations usually located in the wake of the outward-travelling CME. Although stationary type IV bursts, which stand out by their long duration (up to several hours) and strong circular polarisation, have been known for more than fifty years, there have been no systematic studies since the 1980s. In this work we use the data pool of the Nançay Radioheliograph together with white-light coronagraphy, EUV imaging and magnetography from the SoHO, Proba2, SDO and STEREO spacecraft to revisit the source structure and polarisation of a sample of seven well-defined stationary type IV bursts at decimetre-to-metre wavelengths. The radio sources are most often found in one leg, in one case both legs, of the magnetic flux rope erupting into the high corona during the CME. The cross-correlation of the brightness temperature time profiles in the event with sources in both legs implies that the radiating electrons have energies of a few tens of keV. Comparison with the magnetic field measured in the photosphere and its potential extrapolation into the corona shows that the radio emission is in the ordinary mode. This result was inferred historically by means of the hypothesis that the magnetic field orientation in the radio source was that of the dominant sunspot in the parent active region. This hypothesis is shown here to be in conflict with noise storms in the same active region. It is confirmed that the polarisation of stationary type IV continua may be strong, but is rarely total, and that it gradually increases in the early phase of the radio event. We find that the increase is related to the gradual disappearance of some weakly polarised or unpolarised substructure, which dominates the first minutes of the radio emission.

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Challenging Some Contemporary Views of Coronal Mass Ejections. Ii. The Case for Absent Filaments

Cited by 53 publications

References 71 publications

Sun-to-Earth Observations and Characteristics of Isolated Earth-Impacting Interplanetary Coronal Mass Ejections During 2008 – 2014

Sun-to-Earth Observations and Characteristics of Isolated Earth-Impacting Interplanetary Coronal Mass Ejections During 2008 – 2014

The Physical Processes of CME/ICME Evolution

Polarisation and source structure of solar stationary type IV radio bursts

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