Comparison of Two Coronal Mass Ejections Observed by EIT and LASCO with a Model of an Erupting Magnetic Flux Rope

1999 ◽  
Vol 512 (1) ◽  
pp. 484-495 ◽  
Author(s):  
B. E. Wood ◽  
M. Karovska ◽  
J. Chen ◽  
G. E. Brueckner ◽  
J. W. Cook ◽  
...  
Keyword(s):  
Magnetic Flux ◽  
Coronal Mass Ejections ◽  
Flux Rope ◽  
Magnetic Flux Rope

scholarly journals Hydrogen non-equilibrium ionisation effects in coronal mass ejections

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.

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

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

scholarly journals Observations of flux rope formation prior to coronal mass ejections

2013 ◽  
Vol 8 (S300) ◽  
pp. 209-214 ◽  
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.

scholarly journals Causal relationships between eruptive prominences and coronal mass ejections

2008 ◽  
Vol 26 (10) ◽  
pp. 3025-3031 ◽  
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.

The magnetic flux rope structure of coronal mass ejections – 2021 Julius Bartels Medal Lecture at vEGU

2021 ◽  
Author(s):  
Volker Bothmer
Keyword(s):  
Magnetic Flux ◽  
White Light ◽  
Coronal Mass Ejections ◽  
Large Scale ◽  
Neutral Line ◽  
Source Region ◽  
Flux Rope ◽  
Magnetic Clouds ◽  
Small Scale ◽  
Magnetic Flux Rope

<div> <p><span>Magnetic clouds are transient solar wind flows in the interplanetary medium with smooth rotations of the magnetic field vector and low plasma beta values. The analysis of magnetic clouds identified in the data of the two Helios spacecraft between 0.3 and 1 AU showed that they can be interpreted to first order by force-free, large-scale, cylindrical magnetic flux tubes. A close correlation of their occurrences was found with disappearing filaments at the Sun. The magnetic clouds that originated from the northern solar hemisphere showed predominantly left-handed magnetic helicities and the ones from the southern hemisphere predominantly right-handed ones. They were often preceded by an interplanetary shock wave and some were found to be directly following a coronal mass ejection towards the Helios spacecraft as detected by the Solwind coronagraph on board the P78-1 satellite. With the SOHO mission unprecedented long-term observations of coronal mass ejections (CMEs) were taken with the LASCO coronagraphs, with a spatial and time resolution that allowed to investigate their internal white-light fine structure. With complementary photospheric and EUV observations from SOHO, CMEs were found to arise from pre-existing small scale loop systems, overlying regions of opposite magnetic polarities. From the characteristic pattern of their source regions in both solar hemispheres, a generic scheme was presented in which their projected white-light topology depends primarily on the orientation and position of the source region’s neutral line on the solar disk. Based on this interpretation the graduated cylindrical shell method was developed, which allowed to model the electron density distribution of CMEs as 3D flux ropes. This concept was validated through stereoscopic observations of CMEs taken by the coronagraphs of the SECCHI remote sensing suite on board the twin STEREO spacecraft. The observations further revealed that the dynamic near-Sun evolution of CMEs often leads to distortions of their flux rope structure. However, the magnetic flux rope concept of CMEs is today one of the fundamental methods in space weather forecasts. With the Parker Solar Probe we currently observe for the first time CMEs in-situ and remotely at their birthplaces in the solar corona and can further unravel their origin and evolution from the corona into the heliosphere. This lecture provides a state-of-the-art overview on the magnetic structure of CMEs and includes latest observations from the Parker Solar Probe mission.</span></p> </div>

scholarly journals Buildup of a highly twisted magnetic flux rope during a solar eruption

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Wensi Wang ◽  
Rui Liu ◽  
Yuming Wang ◽  
Qiang Hu ◽  
Chenglong Shen ◽  
...  
Keyword(s):  
Magnetic Flux ◽  
Flux Rope ◽  
Magnetic Flux Rope

scholarly journals Magnetic flux rope formation within a magnetosheath hot flow anomaly

2012 ◽  
Vol 117 (A9) ◽  
pp. n/a-n/a ◽  
Author(s):  
H. Hasegawa ◽  
H. Zhang ◽  
Y. Lin ◽  
B. U. Ö. Sonnerup ◽  
S. J. Schwartz ◽  
...  
Keyword(s):  
Magnetic Flux ◽  
Flux Rope ◽  
Magnetic Flux Rope

VERTICAL KINK OSCILLATION OF A MAGNETIC FLUX ROPE STRUCTURE IN THE SOLAR CORONA

2014 ◽  
Vol 797 (2) ◽  
pp. L22 ◽  
Author(s):  
S. Kim ◽  
V. M. Nakariakov ◽  
K.-S. Cho
Keyword(s):  
Magnetic Flux ◽  
Solar Corona ◽  
Flux Rope ◽  
Magnetic Flux Rope
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