scholarly journals Why are CMEs large-scale coronal events: nature or nurture?

2008 ◽  
Vol 26 (10) ◽  
pp. 3077-3088 ◽  
Author(s):  
L. van Driel-Gesztelyi ◽  
G. D. R. Attrill ◽  
P. Démoulin ◽  
C. H. Mandrini ◽  
L. K. Harra
Keyword(s):  
Magnetic Reconnection ◽  
Large Scale ◽  
Observational Evidence ◽  
Angular Width ◽  
Small Scale ◽  
Apparent Contradiction ◽  
Lower Corona ◽  
Magnetic Structures ◽  
Source Regions ◽  
Scale Response

Abstract. The apparent contradiction between small-scale source regions of, and large-scale coronal response to, coronal mass ejections (CMEs) has been a long-standing puzzle. For some, CMEs are considered to be inherently large-scale events – eruptions in which a number of flux systems participate in an unspecified manner, while others consider magnetic reconnection in special global topologies to be responsible for the large-scale response of the lower corona to CME events. Some of these ideas may indeed be correct in specific cases. However, what is the key element which makes CMEs large-scale? Observations show that the extent of the coronal disturbance matches the angular width of the CME – an important clue, which does not feature strongly in any of the above suggestions. We review observational evidence for the large-scale nature of CME source regions and find them lacking. Then we compare different ideas regarding how CMEs evolve to become large-scale. The large-scale magnetic topology plays an important role in this process. There is amounting evidence, however, that the key process is magnetic reconnection between the CME and other magnetic structures. We outline a CME evolution model, which is able to account for all the key observational signatures of large-scale CMEs and presents a clear picture how large portions of the Sun become constituents of the CME. In this model reconnection is driven by the expansion of the CME core resulting from an over-pressure relative to the pressure in the CME's surroundings. This implies that the extent of the lower coronal signatures match the final angular width of the CME.

scholarly journals Solar activities observed with the New Vacuum Solar Telescope

2015 ◽  
Vol 11 (S320) ◽  
pp. 315-320
Author(s):  
Shuhong Yang ◽  
Jun Zhang
Keyword(s):  
Magnetic Reconnection ◽  
Flux Rope ◽  
Observational Evidence ◽  
Small Scale ◽  
Solar Telescope ◽  
New Name ◽  
Direct Observations ◽  
Filament Activation ◽  
First Time

AbstractBased on the New Vacuum Solar Telescope observations, some new results about the solar activities are obtained. (1) In the Hα line, a flux rope tracked by filament activation is detected for the first time. There may exist some mild heating during the filament activation. (2) The direct observations illustrate the mechanism of confined flares, i.e., the flares are triggered by magnetic reconnection between the emerging loops and the pre-existing loops and prevented from being eruptive by the overlying loops. (3) The solid observational evidence of magnetic reconnection between two sets of small-scale loops is reported. The successive slow reconnection changes the conditions around the reconnection area and leads to the rapid reconnection. (4) An ensemble of oscillating bright features rooted in a light bridge is observed and given a new name, light wall. The light wall oscillations may be due to the leakage of p-modes from below the photosphere.

scholarly journals Self-consistent model of electron drift mode turbulence

2008 ◽  
Vol 74 (1) ◽  
pp. 21-33 ◽  
Author(s):  
ZHANNA N. ANDRUSHCHENKO ◽  
MARTIN JUCKER ◽  
VLADIMIR P. PAVLENKO
Keyword(s):  
Large Scale ◽  
Magnetized Plasma ◽  
Small Scale ◽  
Electron Drift ◽  
Quasilinear Theory ◽  
Magnetic Structures ◽  
Large Scale Structures ◽  
Consistent Model ◽  
Scale Turbulence ◽  
Magnetic Electron

AbstractThe nonlinear dynamics of magnetic electron drift mode turbulence are outlined and the generation of large-scale magnetic structures in a non-uniform magnetized plasma by turbulent Reynolds stress is demonstrated. The loop-back of large-scale flows on the microturbulence is elucidated and the modulation of the electron drift mode turbulence spectrum in a medium with slowly varying parameters is presented. The wave kinetic equation in the presence of large-scale flows is derived and it can be seen that the small-scale turbulence and the large-scale structures form a self-regulating system. Finally, it is shown by the use of quasilinear theory that the shearing of microturbulence by the flows can be described by a diffusion equation in k-space and the corresponding diffusion coefficients are calculated.

scholarly journals Structure in the winds of O-Type stars: observations and inferences

2010 ◽  
Vol 6 (S272) ◽  
pp. 136-147
Author(s):  
Alex W. Fullerton
Keyword(s):  
Mass Loss ◽  
Large Scale ◽  
Spatial Scales ◽  
Model Atmosphere ◽  
Theoretical Framework ◽  
Observational Evidence ◽  
Considerable Progress ◽  
Small Scale ◽  
Wind Structure ◽  
Loss Rates

AbstractThis review describes the observational evidence for structure in the winds of O-type stars due to large-scale perturbations and small-scale inhomogeneities. Despite considerable progress, a comprehensive theoretical framework that explains the origin. properties, and coexistence of wind structure on different spatial scales has yet to be constructed and incorporated into model atmosphere analyses. Consequently, it is not yet possible to assess the effect of non-stationary structures on different wind diagnostics in a rigorous way, with the result that accurate empirical determinations of mass-loss rates remain elusive.

THE SOURCE REGIONS OF CORONAL MASS EJECTIONS

2013 ◽  
Vol 23 ◽  
pp. 459-466
Author(s):  
GUIPING ZHOU
Keyword(s):  
Magnetic Flux ◽  
Coronal Mass Ejection ◽  
Coronal Mass Ejections ◽  
Large Scale ◽  
Interplanetary Space ◽  
Activity Analysis ◽  
Angular Width ◽  
Source Regions ◽  
Paper Review ◽  
Mass Ejection

Coronal Mass Ejection is an entire process leading to the ejection of mass and magnetic flux into interplanetary space. Its source is studied by analyzing the associated surface activity. Analysis results show that CMEs have large-scale magnetic source structures, which provide their energy, initiation, and final angular width. This paper review the studies of CME source regions with laying emphasis on their large-scale source structures.

H.D. and the Promise of Queer Kinship

2018 ◽  
Author(s):  
Rebecca Colesworthy
Keyword(s):  
World War Ii ◽  
Large Scale ◽  
Western Culture ◽  
Small Scale ◽  
World War ◽  
Domestic Life ◽  
Apparent Contradiction ◽  
The Gift ◽  
Kinship Theory ◽  
The Way

This chapter aligns H.D.’s understanding of art as spiritual gift with recent queer critiques of kinship theory. H.D.’s posthumously published Notes on Thought and Vision in part reads as a treatise on kinship—on the way small-scale exchanges provide a basis for large-scale social formations. In identifying homoeroticism as the ground of Western culture and lending equal significance to masculine and feminine relationships, the text offers a queer alternative to Freud’s and Lévi-Strauss’s heteronormative models of kinship. Her World War II memoir, The Gift, also posthumously published, gives mythico-historical form to this alternative, drawing connections between her Moravian matrilineage, settler–Native relations, the current war, and her domestic life with Bryher. By further linking H.D.’s notion of the gift to developments in telecommunications, this chapter takes distance from atavistic, gynocentric, and elitist readings of her work while reconsidering the apparent contradiction between her limited publications and utopian ambitions for art.

scholarly journals Quiet Sun coronal heating: Analyzing large scale magnetic structures driven by different small-scale uniform sources

2002 ◽  
Vol 382 (2) ◽  
pp. 713-721 ◽  
Author(s):  
O. Podladchikova ◽  
T. Dudok de Wit ◽  
V. Krasnoselskikh ◽  
B. Lefebvre
Keyword(s):  
Large Scale ◽  
Coronal Heating ◽  
Small Scale ◽  
Quiet Sun ◽  
Magnetic Structures

scholarly journals Annihilation of Magnetic Islands at the Top of Solar Flare Loops

2021 ◽  
Vol 923 (2) ◽  
pp. 227
Author(s):  
Yulei Wang ◽  
Xin Cheng ◽  
Mingde Ding ◽  
Quanming Lu
Keyword(s):  
Magnetic Reconnection ◽  
Thermal Conduction ◽  
Large Scale ◽  
Magnetic Energy ◽  
Small Scale ◽  
Magnetic Islands ◽  
Flare Loop ◽  
Flare Loops ◽  
Flare Model ◽  
Magnetic Energy Release

Abstract The dynamics of magnetic reconnection in the solar current sheet (CS) is studied by high-resolution 2.5-dimensional MHD simulation. With the commencing of magnetic reconnection, a number of magnetic islands are formed intermittently and move quickly upward and downward along the CS. Upon collision with the semi-closed flux of the flare loops, the downflow islands cause a second reconnection with a rate comparable with that in the main CS. Though the time-integrated magnetic energy release is still dominated by the reconnection in the main CS, the second reconnection can release substantial magnetic energy, annihilating the main islands and generating secondary islands with various scales at the flare loop top. The distribution function of the flux of the secondary islands is found to follow a power law varying from f ψ ∼ ψ − 1 (small scale) to ψ −2 (large scale), which seems to be independent to background plasma β and thermal conduction (TC). However, the spatial scale and the strength of the termination shocks driven by the main reconnection outflows or islands decrease if β increases or if TC is included. We suggest that the annihilation of magnetic islands at the flare loop top, which is not included in the standard flare model, plays a nonnegligible role in releasing magnetic energy to heat flare plasma and accelerate particles.

scholarly journals Magnetopause reconnection and interlinked flux tubes

2013 ◽  
Vol 31 (10) ◽  
pp. 1853-1866 ◽  
Author(s):  
F. R. Cardoso ◽  
W. D. Gonzalez ◽  
D. G. Sibeck ◽  
M. Kuznetsova ◽  
D. Koga
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Reconnection ◽  
Large Scale ◽  
Time Dependent ◽  
Mhd Simulation ◽  
Flux Tubes ◽  
Magnetic Structures ◽  
Mhd Simulations ◽  
Magnetopause Reconnection

Abstract. Magnetic reconnection can be a continuous or a transient process. Global magnetohydrodynamics (MHD) simulations are important tools to understand the relevant magnetic reconnection mechanisms and the resulting magnetic structures. We have studied magnetopause reconnection using a global 3-D MHD simulation in which the interplanetary magnetic field (IMF) has been set to large positive By and large negative Bz components, i.e., a south-duskward direction. Flux tubes have been observed even during these constant solar wind conditions. We have focused on the interlinked flux tubes event resulting from time-dependent, patchy and multiple reconnection. At the event onset, two reconnection modes seem to occur simultaneously: a time-dependent, patchy and multiple reconnection for the subsolar region; and, a steady and large-scale reconnection for the regions far from the subsolar site.

scholarly journals Soft X-Ray Observations of Eruptive Prominences

1998 ◽  
Vol 167 ◽  
pp. 376-379
Author(s):  
T. Watanabe ◽  
M. Yamamoto ◽  
H. Hudson ◽  
M. Irie ◽  
K. Ichimoto ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Large Scale ◽  
Eruptive Prominence ◽  
X Ray ◽  
Magnetic Structures

AbstractEvolution of magnetic structures in the region around an eruptive prominence of August 28, 1992 are examined using soft X-ray images obtained by Yohkoh. The eruption was preceded by the appearance of a large-scale soft X-ray jet which was ejected from near the root of the southern end of the prominence. Changes of magnetic geometry at the southern end of the prominence appeared to trigger the eruption. In the course of prominence eruption, helically twisted soft X-ray loops were observed around the prominence. This indicates that magnetic reconnection of a sheared arcade took place underneath the erupting prominence.

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