Coronal dimming as a proxy for stellar coronal mass ejections

AbstractSolar coronal dimmings have been observed extensively in the past two decades and are believed to have close association with coronal mass ejections (CMEs). Recent study found that coronal dimming is the only signature that could differentiate powerful flares that have CMEs from those that do not. Therefore, dimming might be one of the best candidates to observe the stellar CMEs on distant Sun-like stars. In this study, we investigate the possibility of using coronal dimming as a proxy to diagnose stellar CMEs. By simulating a realistic solar CME event and corresponding coronal dimming using a global magnetohydrodynamics model (AWSoM: Alfvén-wave Solar Model), we first demonstrate the capability of the model to reproduce solar observations. We then extend the model for simulating stellar CMEs by modifying the input magnetic flux density as well as the initial magnetic energy of the CME flux rope. Our result suggests that with improved instrument sensitivity, it is possible to detect the coronal dimming signals induced by the stellar CMEs.

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Causal relationships between eruptive prominences and coronal mass ejections

Annales Geophysicae ◽

10.5194/angeo-26-3025-2008 ◽

2008 ◽

Vol 26 (10) ◽

pp. 3025-3031 ◽

Cited By ~ 23

Author(s):

B. Filippov ◽

S. Koutchmy

Keyword(s):

Magnetic Flux ◽

Coronal Mass Ejections ◽

Close Association ◽

Flux Rope ◽

Critical Values ◽

General Question ◽

Magnetic Flux Rope ◽

Filament Activation ◽

Field Lines ◽

The Disappeared

Abstract. A close association between eruptive prominences and CMEs, both slow and fast CMEs, was reported in many studies. Sometimes it was possible to follow the material motion starting from the prominence (filament) activation to the CME in the high corona. Remnants of the prominence were found in the bright core of the CME. However, detailed comparisons of the two phenomena reveal problems in explaining CMEs as a continuation of filament eruptions in the upper corona. For example, the heliolatitudes of the disappeared filaments and subsequent coronal ejections sometimes differ by tens of degrees. In order to clear up the problems appearing when considering this association EP-CME, we tentatively analyse the more general question of the dynamics of the generic magnetic flux rope. Prominences and filaments are the best tracers of the flux ropes in the corona long before the beginning of the eruption. A twisted flux rope is held by the tension of field lines of photospheric sources until parameters of the system reach critical values and a catastrophe happens. We suggest that the associated flux rope height above the photosphere is one of these parameters and that it is revealed by the measured height of the filament. 80 filaments were analysed and we found that eruptive prominences were near the so-called limit of stability a few days before their eruptions. We suggest that a comparison of actual heights of prominences with the calculated critical heights from magnetograms could be systematically used to predict filament eruptions and the corresponding CMEs.

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Complex Evolution of Coronal Mass Ejections in the Inner Heliosphere as Revealed by Numerical Simulations and STEREO Observations: A Review

Proceedings of the International Astronomical Union ◽

10.1017/s174392131301106x ◽

2013 ◽

Vol 8 (S300) ◽

pp. 255-264 ◽

Cited By ~ 1

Author(s):

Noé Lugaz ◽

Charles J. Farrugia ◽

Nada Al-Haddad

Keyword(s):

Numerical Simulations ◽

Coronal Mass Ejections ◽

Flux Rope ◽

Magnetic Flux Rope ◽

Work Related ◽

The Core ◽

The Past ◽

Complex Models ◽

Inner Heliosphere

AbstractThe transit of coronal mass ejections (CMEs) from the Sun to 1 AU lasts on average one to five days. As they propagate, CMEs interact with the solar wind and preceding eruptions, which modify their properties. In the past ten years, the evolution of CMEs in the inner heliosphere has been investigated with the help of numerical simulations, through the analysis of remote-sensing heliospheric observations, especially with the SECCHI suite onboard STEREO, and through the analysis of multi-spacecraft in situ measurements. Most studies have focused on understanding the characteristics of the magnetic flux rope thought to form the core of the CME. Here, we first review recent work related to CME propagation in the heliosphere, which point towards the need to develop more complex models to analyze CME observations. In the second part of this article, we review some recent studies of CME-CME interaction, which also illustrate the complexity of phenomena occurring in the inner heliosphere.

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The development of magnetic field line wander by plasma turbulence

Journal of Plasma Physics ◽

10.1017/s0022377817000617 ◽

2017 ◽

Vol 83 (4) ◽

Cited By ~ 5

Author(s):

Gregory G. Howes ◽

Sofiane Bourouaine

Keyword(s):

Magnetic Field ◽

Field Line ◽

Magnetic Field Line ◽

Large Scale ◽

Magnetic Energy ◽

Plasma Turbulence ◽

Alfven Wave ◽

Astrophysical Plasmas ◽

Field Lines ◽

The Magnetic Field

Plasma turbulence occurs ubiquitously in space and astrophysical plasmas, mediating the nonlinear transfer of energy from large-scale electromagnetic fields and plasma flows to small scales at which the energy may be ultimately converted to plasma heat. But plasma turbulence also generically leads to a tangling of the magnetic field that threads through the plasma. The resulting wander of the magnetic field lines may significantly impact a number of important physical processes, including the propagation of cosmic rays and energetic particles, confinement in magnetic fusion devices and the fundamental processes of turbulence, magnetic reconnection and particle acceleration. The various potential impacts of magnetic field line wander are reviewed in detail, and a number of important theoretical considerations are identified that may influence the development and saturation of magnetic field line wander in astrophysical plasma turbulence. The results of nonlinear gyrokinetic simulations of kinetic Alfvén wave turbulence of sub-ion length scales are evaluated to understand the development and saturation of the turbulent magnetic energy spectrum and of the magnetic field line wander. It is found that turbulent space and astrophysical plasmas are generally expected to contain a stochastic magnetic field due to the tangling of the field by strong plasma turbulence. Future work will explore how the saturated magnetic field line wander varies as a function of the amplitude of the plasma turbulence and the ratio of the thermal to magnetic pressure, known as the plasma beta.

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Kinematics and Differential Emission Measure of the Flux Rope during Coronal Mass Ejections

EAS Publications Series ◽

10.1051/eas/1255040 ◽

2012 ◽

Vol 55 ◽

pp. 287-291

Author(s):

M.D. Ding ◽

X. Cheng ◽

J. Zhang

Keyword(s):

Coronal Mass Ejections ◽

Emission Measure ◽

Flux Rope ◽

Differential Emission Measure

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Hydrogen non-equilibrium ionisation effects in coronal mass ejections

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037638 ◽

2020 ◽

Vol 637 ◽

pp. A49

Author(s):

P. Pagano ◽

A. Bemporad ◽

D. H. Mackay

Keyword(s):

Magnetic Flux ◽

Visible Light ◽

Coronal Mass Ejections ◽

Flux Rope ◽

Neutral Hydrogen ◽

Hydrogen Atoms ◽

Mhd Simulation ◽

Magnetic Flux Rope ◽

New Generation ◽

Non Equilibrium

Context. A new generation of coronagraphs used to study solar wind and coronal mass ejections (CMEs) are being developed and launched. These coronagraphs will heavily rely on multi-channel observations where visible light (VL) and UV-EUV (ultraviolet-extreme ultraviolet) observations provide new plasma diagnostics. One of these instruments, Metis on board ESA-Solar Orbiter, will simultaneously observe VL and the UV Lyman-α line. The number of neutral hydrogen atoms (a small fraction of coronal protons) is a key parameter for deriving plasma properties, such as the temperature from the observed Lyman-α line intensity. However, these measurements are significantly affected if non-equilibrium ionisation effects occur, which can be relevant during CMEs. Aims. The aim of this work is to determine if non-equilibrium ionisation effects are relevant in CMEs and, in particular, when and in which regions of the CME plasma ionisation equilibrium can be assumed for data analysis. Methods. We used a magneto-hydrodynamic (MHD) simulation of a magnetic flux rope ejection to generate a CME. From this, we then reconstructed the ionisation state of hydrogen atoms in the CME by evaluating both the advection of neutral and ionised hydrogen atoms and the ionisation and recombination rates in the MHD simulation. Results. We find that the equilibrium ionisation assumption mostly holds in the core of the CME, which is represented by a magnetic flux rope. In contrast, non-equilibrium ionisation effects are significant at the CME front, where we find about 100 times more neutral hydrogen atoms than prescribed by ionisation equilibrium conditions. We find this to be the case even if this neutral hydrogen excess might be difficult to identify due to projection effects. Conclusions. This work provides key information for the development of a new generation of diagnostic techniques that aim to combine visible light and Lyman-α line emissions. The results show that non-equilibrium ionisation effects need to be considered when we analyse CME fronts. Incorrectly assuming equilibrium ionisation in these regions would lead to a systematic underestimate of plasma temperatures.

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Do All Interplanetary Coronal Mass Ejections Have a Magnetic Flux Rope Structure Near 1 au?

The Astrophysical Journal ◽

10.3847/2041-8213/abb6ec ◽

2020 ◽

Vol 901 (2) ◽

pp. L21

Author(s):

H. Q. Song ◽

J. Zhang ◽

X. Cheng ◽

G. Li ◽

Q. Hu ◽

...

Keyword(s):

Magnetic Flux ◽

Coronal Mass Ejections ◽

Flux Rope ◽

Interplanetary Coronal Mass Ejections ◽

Magnetic Flux Rope

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Observations of flux rope formation prior to coronal mass ejections

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313010983 ◽

2013 ◽

Vol 8 (S300) ◽

pp. 209-214 ◽

Cited By ~ 7

Author(s):

Lucie M. Green ◽

Bernhard Kliem

Keyword(s):

Magnetic Flux ◽

Magnetic Structure ◽

Solar Atmosphere ◽

Coronal Mass Ejections ◽

Flux Rope ◽

Active Regions ◽

Magnetic Configuration ◽

Magnetic Flux Rope ◽

Source Regions ◽

Flux Ropes

AbstractUnderstanding the magnetic configuration of the source regions of coronal mass ejections (CMEs) is vital in order to determine the trigger and driver of these events. Observations of four CME productive active regions are presented here, which indicate that the pre-eruption magnetic configuration is that of a magnetic flux rope. The flux ropes are formed in the solar atmosphere by the process known as flux cancellation and are stable for several hours before the eruption. The observations also indicate that the magnetic structure that erupts is not the entire flux rope as initially formed, raising the question of whether the flux rope is able to undergo a partial eruption or whether it undergoes a transition in specific flux rope configuration shortly before the CME.

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Pursuing Forecasts of the Behavior and Arrival of Coronal Mass Ejections through Modeling and Observations

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317010882 ◽

2017 ◽

Vol 13 (S335) ◽

pp. 58-64 ◽

Cited By ~ 1

Author(s):

Hebe Cremades

Keyword(s):

Remote Sensing ◽

Coronal Mass Ejections ◽

Empirical Models ◽

Time Of Arrival ◽

Data Sets ◽

Radio Waves ◽

Weather Forecasts ◽

The Past ◽

Increasing Demand ◽

Solar Disturbances

AbstractSophisticated instrumentation dedicated to studying and monitoring our Sun’s activity has proliferated in the past few decades, together with the increasing demand of specialized space weather forecasts that address the needs of commercial and government systems. As a result, theoretical and empirical models and techniques of increasing complexity have been developed, aimed at forecasting the occurrence of solar disturbances, their evolution, and time of arrival to Earth. Here we will review groundbreaking and recent methods to predict the propagation and evolution of coronal mass ejections and their driven shocks. The methods rely on a wealth of data sets provided by ground- and space-based observatories, involving remote-sensing observations of the corona and the heliosphere, as well as detections of radio waves.

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