Evidence for Rayleigh-Taylor Plasma Instability at the Front of Solar Coronal Mass Ejections

This work focuses on the interaction of a Coronal Mass Ejection (CME) with the ambient solar corona, by studying the spatial and temporal evolution of the density fluctuations observed by the SOHO/UV Coronagraph Spectrometer (UVCS) during the CME. The investigation is performed by applying a wavelet analysis to the HI Ly α 1216 Å line intensity fluctuations observed with UVCS during the CME occurred on 24 December 2006. Strong and coherent fluctuations, with a significant spatial periodicity of about 84 Mm ≃ 0.12 R ⊙ , are shown to develop in about an hour along the front of the CME. The results seem to indicate the Rayleigh-Taylor (RT) instability, susceptible to the deceleration of the heavier fluid of the CME front into the lighter surrounding coronal plasma, as the likely mechanism underlying the generation of the observed plasma fluctuations. This could be the first inference of the RT instability in the outer solar corona in UV, due to the transit of a CME front in the quiet coronal plasma; this interpretation is also supported by a linear magnetohydrodynamic analysis of the RT instability.

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Coronal Mass Ejections and the Critical Velocity Ionization Phenomenon

International Astronomical Union Colloquium ◽

10.1017/s0252921100025240 ◽

1994 ◽

Vol 144 ◽

pp. 159-162

Author(s):

E. Golbraikh ◽

M. Filippov ◽

R. Steinitz

Keyword(s):

Solar Corona ◽

Coronal Mass Ejections ◽

High Speed ◽

High Energy ◽

Neutral Gas ◽

High Energy Electrons ◽

Mass Ejection ◽

Heating Up ◽

Ionization Velocity ◽

High Speed Flows

AbstractWe propose a new viewpoint concerning the mechanism for coronal mass ejection (CME) formation in the solar corona. According to developed approach the origin of CME is connected with high-speed movement in the transition zone or lower. The high-speed flows of neutral gas are able to produce explosive events (EEs) and jets in the chromosphere by the critical ionization velocity (CIV) mechanism. They can be sources of eruptive prominences. In this case CIV phenomenon results in ion and electron heating up to tens of eV. In turn high-energy electrons can cause weak flares. The eruptive prominences generate CMEs with velocities ≥ 100 km s−1. Thus, the following chain of phenomena appears to form the observed CME: high-speed movements of neutral gas – its ionization due to CIV phenomenon – eruptive prominences (weak flares) – CMEs.

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Exploring Coronal Structures with SOHO

International Astronomical Union Colloquium ◽

10.1017/s0252921100064915 ◽

2000 ◽

Vol 179 ◽

pp. 403-406

Author(s):

M. Karovska ◽

B. Wood ◽

J. Chen ◽

J. Cook ◽

R. Howard

Keyword(s):

Solar Corona ◽

Image Enhancement ◽

Coronal Mass Ejections ◽

Dynamical Evolution ◽

Small Scale ◽

Low Contrast ◽

Contrast Structures ◽

Scale Structures ◽

Small Scale Structures ◽

Coronal Structures

AbstractWe applied advanced image enhancement techniques to explore in detail the characteristics of the small-scale structures and/or the low contrast structures in several Coronal Mass Ejections (CMEs) observed by SOHO. We highlight here the results from our studies of the morphology and dynamical evolution of CME structures in the solar corona using two instruments on board SOHO: LASCO and EIT.

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Solar Filaments as Tracers of Subsurface Processes

International Astronomical Union Colloquium ◽

10.1017/s0252921100064459 ◽

2000 ◽

Vol 179 ◽

pp. 177-183

Author(s):

D. M. Rust

Keyword(s):

Magnetic Fields ◽

Magnetic Flux ◽

Coronal Mass Ejections ◽

Interplanetary Space ◽

Intermediate Stage ◽

Coronal Plasma ◽

Magnetic Helicity ◽

The Sun ◽

New Paradigm ◽

Solar Filaments

AbstractSolar filaments are discussed in terms of two contrasting paradigms. The standard paradigm is that filaments are formed by condensation of coronal plasma into magnetic fields that are twisted or dimpled as a consequence of motions of the fields’ sources in the photosphere. According to a new paradigm, filaments form in rising, twisted flux ropes and are a necessary intermediate stage in the transfer to interplanetary space of dynamo-generated magnetic flux. It is argued that the accumulation of magnetic helicity in filaments and their coronal surroundings leads to filament eruptions and coronal mass ejections. These ejections relieve the Sun of the flux generated by the dynamo and make way for the flux of the next cycle.

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