scholarly journals LASCO/EIT Observations of Coronal Mass Ejections from Large-Scale Filament Channels

1998 ◽  
Vol 167 ◽  
pp. 475-478
Author(s):  
S.P. Plunket ◽  
K.P. Dere ◽  
R.A. Howard ◽  
D.J. Michels ◽  
G.E. Brueckner ◽  
...  
Keyword(s):  
Solar Activity ◽  
Southern Hemisphere ◽  
Coronal Mass Ejections ◽  
Large Scale ◽  
Neutral Line ◽  
The West ◽  
Magnetic Neutral Line ◽  
Filament Channel ◽  
Global Nature

AbstractSolar activity in the latter half of 1996 was dominated by the presence of an extended filament channel in the southern hemisphere, forming a switchback configuration where it merged with the polar crown. Several large coronal mass ejections (CMEs) were observed to originate on or near this magnetic neutral line by the LASCO and EIT instruments on SOHO. As this channel gradually disappeared, a new, extended channel formed to the west of the old one, and this new channel also produced a number of large CMEs. We report here on observations of two events (December 23, 1996 and February 7,1997), and discuss the global nature of these events.

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 The east-west asymmetry in Coronal Mass Ejections: evidence for active longitudes

2005 ◽  
Vol 23 (9) ◽  
pp. 3139-3147 ◽  
Author(s):  
M. Skirgiello
Keyword(s):  
Solar Activity ◽  
Southern Hemisphere ◽  
Coronal Mass Ejections ◽  
Solar Rotation ◽  
Occurrence Rate ◽  
The Sun ◽  
The Earth ◽  
Orbital Revolution ◽  
Time Periods ◽  
East West

Abstract. Various manifestations of solar activity are not uniformly distributed with heliographic longitude. By using east-west asymmetry in the occurrence rate of CMEs (coronal mass ejections), the longitudinal dependence in SOHO LASCO 1996-2004 data has been studied in this work. The solar rotation periodicity has been found, indicating the presence of active longitudes, whose phase is reversed twice during the studied period. It is more prominent in the Southern Hemisphere. The east-west asymmetry is also present when calculated for longer time periods. Sometimes (particularly during low solar activity), there is an alternation of the eastern and western domination every six months. Taking into account the orbital revolution of the Earth about the Sun, this indicates the existence of enhanced activity, fixed in space (not undergoing Carrington rotation). Moreover, there is about a 3.7% overall excess of western events, lasting for the entire reported time, suggesting some bias in the observations. A hypothesis to explain this phenomenon is proposed.

scholarly journals Solar-forced shifts of the Southern Hemisphere Westerlies during the late Holocene

2010 ◽  
Vol 6 (2) ◽  
pp. 369-384 ◽  
Author(s):  
V. Varma ◽  
M. Prange ◽  
F. Lamy ◽  
U. Merkel ◽  
M. Schulz
Keyword(s):  
Solar Activity ◽  
Southern Hemisphere ◽  
Ocean Circulation ◽  
Late Holocene ◽  
Large Scale ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Latitudinal Position ◽  
Potential Factor

Abstract. The Southern Hemisphere Westerly Winds (SWW) constitute an important zonal circulation that influences large-scale precipitation patterns and ocean circulation. Variations in their intensity and latitudinal position have been suggested to exert a strong influence on the CO2 budget in the Southern Ocean, thus making them a potential factor affecting the global climate. In the present study, the possible influence of solar forcing on SWW variability during the late Holocene is addressed. It is shown that a high-resolution iron record from the Chilean continental slope (41° S), which basically reflects changes in the position of the SWW, is significantly correlated with reconstructed solar activity. In addition, solar sensitivity experiments with a comprehensive global climate model (CCSM3) are carried out to study the response of SWW to solar variability. Taken together, the proxy and model results strongly suggest that centennial-scale periods of lower (higher) solar activity caused equatorward (southward) shifts of the SWW during the past 3000 years.

scholarly journals Solar Coronal Mass Ejections

1990 ◽  
Vol 140 ◽  
pp. 16-16
Author(s):  
A. J. Hundhausen ◽  
D. G. Sime ◽  
B. C. Low
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Coronal Mass Ejections ◽  
Large Scale ◽  
Interplanetary Space ◽  
Field Of View ◽  
Solar Activity Minimum ◽  
Eruptive Prominence ◽  
Activity Maximum ◽  
Mass Ejection

In addition to the more or less steady solar wind, the Sun also ejects mass in highly time dependent events taking place in the corona once every few days at solar activity minimum and as often as three times a day at solar activity maximum (Hundhausen 1988, Low 1986). These events involve large scale reconfiguration of the corona with an expulsion of some 1015g of ionized material into interplanetary space. The High Altitude Observatory (HAO) operates a groundbased internally occulted coronagraph at Mauna Loa, Hawaii, with a field of view of the corona from 1.2 to 2.2R⊙ in heliocentric distance, registering polarization brightness. A second instrument at the same site in Hawaii observes the solar limb in Hα emission to detect chromospheric material from the limb out to 1.5R⊙. HAO also operates an externally occulted coronagraph/polarimeter onboard the NASA Solar Maximum Mission Satellite (SMM) launched in 1980, capitalizing on the advantage of space with a field of view from 1.5 to 6R⊙ to cover the fainter outer corona. Coronal mass ejections involve magnetic field reconfiguration from high in the corona down to the base lying below 1.1R⊙. Important physical insights can be had when simultaneous observations by HAO's three instruments are put together with a common scale and orientation to reveal a mass ejection in the full extent of the solar atmosphere from the limb outward. Combined observations of two mass ejections are presented, one associated with an eruptive prominence and the the other associated with a flare. The significance of these two events is that in both cases, the mass ejection was in fully developed motion and had traveled high into the corona well before the onset of the associated prominence or flare eruption, pointing to an instability in the large scale coronal magnetic field as the underlying cause of the global reconfiguration.

scholarly journals Solar-forced shifts of the Southern Hemisphere Westerlies during the Holocene

2011 ◽  
Vol 7 (2) ◽  
pp. 339-347 ◽  
Author(s):  
V. Varma ◽  
M. Prange ◽  
F. Lamy ◽  
U. Merkel ◽  
M. Schulz
Keyword(s):  
Solar Activity ◽  
Southern Hemisphere ◽  
Ocean Circulation ◽  
Large Scale ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
The Holocene ◽  
Latitudinal Position ◽  
Potential Factor

Abstract. The Southern Hemisphere Westerly Winds (SWW) constitute an important zonal circulation that influences large-scale precipitation patterns and ocean circulation. Variations in their intensity and latitudinal position have been suggested to exert a strong influence on the CO2 budget in the Southern Ocean, thus making them a potential factor affecting the global climate. In the present study, the possible influence of solar forcing on SWW variability during the Holocene is addressed. It is shown that a high-resolution iron record from the Chilean continental slope (41° S), which is interpreted to reflect changes in the position of the SWW, is significantly correlated with reconstructed solar activity during the past 3000 years. In addition, solar sensitivity experiments with a comprehensive global climate model (CCSM3) were carried out to study the response of SWW to solar variability. Taken together, the proxy and model results suggest that centennial-scale periods of lower (higher) solar activity caused equatorward (southward) shifts of the annual mean SWW.

scholarly journals Colonial management as a social field: The Palestinian remaking of Israel’s system of spatial control

2021 ◽  
pp. 001139212110246
Author(s):  
Walid Habbas ◽  
Yael Berda
Keyword(s):  
Large Scale ◽  
Central Component ◽  
Colonial Rule ◽  
Spatial Mobility ◽  
The West ◽  
Social Field ◽  
Spatial Control ◽  
Racial Hierarchy ◽  
Economic Elite ◽  
The Everyday

This article delves into the everyday dynamics of colonial rule to outline a novel way of understanding colonized–colonizer interactions. It conceives colonial management as a social field in which both the colonized and colonizers negotiate and exchange resources, despite their decidedly unequal positions within a racial hierarchy. Drawing their example from the West Bank, the authors argue that a Palestinian economic elite has proactively participated in the co-production of the colonial management of spatial mobility, a central component of Israeli colonial rule. The study employs interviews and document analysis to investigate how the nexus between Palestine’s commercial-logistical needs and Israel’s security complex induced large-scale Palestinian producers to exert agency and reorder commercial mobility. The authors describe and explain the evolution of a ‘Door-to-Door’ logistical arrangement, in which large-scale Palestinian traders participate in extending Israeli’s system of spatial control in exchange for facilitating logistical mobility. This horizontal social encounter that entails pay-offs is conditioned, but not fully determined, by vertical relations of domination and subordination.

scholarly journals P/Halley: The Disconnection Event of 1986 April 11

1988 ◽  
Vol 98 ◽  
pp. 155-157 ◽  
Author(s):  
P.M. Bergé ◽  
G. Mahoux ◽  
A.C. Levasseur-Regourd
Keyword(s):  
Southern Hemisphere ◽  
Large Scale ◽  
Focal Length ◽  
La Réunion ◽  
Structure Dynamics ◽  
Plasma Tail

This work was carried out by an expedition organized by the S.A.F. in 1986 April to La Réunion. The aim was to observe and photograph P/Halley, within the framework of IHW, as part of the Island Network in the southern hemisphere. To be more precise, our work consisted of studying large-scale phenomena: the structure, dynamics and possible disconnection events in the plasma tail. We were lucky enough to observe one of the latter on the night of April 11/12, and describe it here.For the Island Network, IHW had a number of Schmidt telescopes (Celestron 8). One was lent to the S.A.F. and this is what we used. This telescope has a focal ratio of 1.5, with a 200-mm (8-inch) objective and 300-mm focal length. We used only Kodak TP2415 film, hypersensitized in forming gas (24h at 60°C).

Chronique d’une écologie décoloniale dans C’est ma terre de Fabrice Bouckat

2020 ◽  
Vol 23 (3) ◽  
pp. 189-205 ◽  
Author(s):  
Françoise Naudillon
Keyword(s):  
West Indies ◽  
Large Scale ◽  
Documentary Film ◽  
Ecological Crisis ◽  
Agent Orange ◽  
Time And Space ◽  
The West ◽  
The One

The documentary film C’est ma terre by Fabrice Bouckat screened during the 2019 edition of Terrafestival is one of the first large-scale films produced locally on the crisis of the chlordecone molecule. This article will examine from a decolonial perspective, how its director, a Martinican with Gabonese origins who lives and works in Guadeloupe, develops a synthetic and universal vision of environmental crises, and thus demonstrates that destruction of ecosystems crosses time and space, cultures and lands, languages and peoples by bringing ecological crisis in the West Indies closer to the one experienced by the Vietnamese victims of Agent Orange.

scholarly journals 14C in the Deep Water of the East Atlantic

Radiocarbon ◽  
1986 ◽  
Vol 28 (2A) ◽  
pp. 391-396 ◽  
Author(s):  
Reiner Schlitzer
Keyword(s):  
Deep Water ◽  
Large Scale ◽  
Bottom Water ◽  
Source Parameters ◽  
Potential Temperature ◽  
Source Terms ◽  
East Atlantic ◽  
The West ◽  
Model Calculations ◽  
Inflowing Water

The renewal of east Atlantic deep water and its large-scale circulation and mixing have been studied in observed distributions of temperature, silicate, ΣCO2, and 14C. 14C variations in northeast Atlantic deep water below 3500m depth are small. Δ14C values range from − 100‰ to −125‰. 14C bottom water concentrations decrease from Δ14C =−117‰ in the Sierra Leone Basin to Δ14C = − 123‰ in the Iberian Basin and are consistent with a mean northward bottom water flow. The characteristic of the water that flows from the west Atlantic through the Romanche Trench into the east Atlantic was determined by inspection of θ/Δ14C and θ/SiO2 diagrams. A mean potential temperature of θ = 1.50 ± .05°C was found for the inflowing water. A multi-box model including circulation, mixing, and chemical source terms in the deep water has been formulated. Linear programing and least-squares techniques have been used to obtain the transport and source parameters of the model from the observed tracer fields. Model calculations reveal an inflow through the Romanche Trench from the west Atlantic, which predominates over any other inflow, of (5 ± 2) Sv (potential temperature 1.50°C), a convective turnover of (150 ± 50) years and a vertical apparent diffusivity of (4 ± 1) cm2/s. Chemical source terms are in the expected ranges.

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