scholarly journals The Key Role of Cold Ionospheric Ions As a Source of Hot Magnetospheric Plasma and As a Driver of the Dynamics of Substorms and Storms

2021 ◽  
Vol 8 ◽  
Author(s):  
C. R. Chappell ◽  
A. Glocer ◽  
B. L. Giles ◽  
T. E. Moore ◽  
M. M. Huddleston ◽  
...  
Keyword(s):  
Solar Wind ◽  
Magnetospheric Plasma ◽  
Direct Access ◽  
Polar Wind ◽  
Polar Cusp ◽  
Reconnection Region ◽  
Mhd Modeling ◽  
Warm Plasma ◽  
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The solar wind has been seen as the major source of hot magnetospheric plasma since the early 1960’s. More recent theoretical and observational studies have shown that the cold (few eV) polar wind and warmer polar cusp plasma that flow continuously upward from the ionosphere can be a very significant source of ions in the magnetosphere and can become accelerated to the energies characteristic of the plasma sheet, ring current, and warm plasma cloak. Previous studies have also shown the presence of solar wind ions in these magnetospheric regions. These studies are based principally on proxy measurements of the ratios of He++/H+ and the high charge states of O+/H+. The resultant admixture of ionospheric ions and solar wind ions that results has been difficult to quantify, since the dominant H+ ions originating in the ionosphere and solar wind are indistinguishable. The ionospheric ions are already inside the magnetosphere and are filling it from the inside out with direct access from the ionosphere to the center of the magnetotail. The solar wind ions on the other hand must gain access through the outer boundaries of the magnetosphere, filling the magnetosphere from the outside in. These solar wind particles must then diffuse or drift from the flanks of the magnetosphere to the near-midnight reconnection region of the tail which takes more time to reach (hours) than the continuously large outflowing ionospheric polar wind (10’s of min). In this paper we examine the magnetospheric filling using the trajectories of the different ion sources to unravel the intermixing process rather than trying to interpret only the proxy ratios. We compare the timing of the access of the ionospheric and solar wind sources and we use new merged ionosphere-magnetosphere multi-fluid MHD modeling to separate and compare the ionospheric and solar wind H+ source strengths. The rapid access of the initially cold polar wind and warm polar cusp ions flowing down-tail in the lobes into the mid-plane of the magnetotail, suggests that, coupled with a southward turning of the IMF Bz, these ions can play a key triggering role in the onset of substorms and subsequent large storms.

scholarly journals Role of Magnetospheric Plasma Physics for Understanding Cosmic Phenomena

1990 ◽  
Vol 115 ◽  
pp. 90-93 ◽  
Author(s):  
Indra Mohan Lal Das
Keyword(s):  
Solar Wind ◽  
Plasma Physics ◽  
Laboratory Experiments ◽  
Magnetospheric Plasma ◽  
Proper Understanding ◽  
In Situ Observations

AbstractCosmic phenomena occur in the remote regions of space where in-situ observations are not possible. For proper understanding of these phenomena laboratory experiments are essential, but the in-situ observations of magnetospheric plasma provides even a better background to test various hypothesis of cosmic interest. This is because the ionospheric-magnetospheric plasma and the solar wind are the only cosmic plasmas accessible to extensive in-situ observations and experiments.

scholarly journals The Role of Capsid in HIV-1 Nuclear Entry

Viruses ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1425
Author(s):  
Anabel Guedán ◽  
Eve R. Caroe ◽  
Genevieve C. R. Barr ◽  
Kate N. Bishop
Keyword(s):  
Nuclear Pore ◽  
Outer Face ◽  
Nuclear Entry ◽  
Nuclear Compartment ◽  
Critical Step ◽  
Technological Advances ◽  
Dividing Cells ◽  
Hiv 1 ◽  
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HIV-1 can infect non-dividing cells. The nuclear envelope therefore represents a barrier that HIV-1 must traverse in order to gain access to the host cell chromatin for integration. Hence, nuclear entry is a critical step in the early stages of HIV-1 replication. Following membrane fusion, the viral capsid (CA) lattice, which forms the outer face of the retroviral core, makes numerous interactions with cellular proteins that orchestrate the progress of HIV-1 through the replication cycle. The ability of CA to interact with nuclear pore proteins and other host factors around the nuclear pore determines whether nuclear entry occurs. Uncoating, the process by which the CA lattice opens and/or disassembles, is another critical step that must occur prior to integration. Both early and delayed uncoating have detrimental effects on viral infectivity. How uncoating relates to nuclear entry is currently hotly debated. Recent technological advances have led to intense discussions about the timing, location, and requirements for uncoating and have prompted the field to consider alternative uncoating scenarios that presently focus on uncoating at the nuclear pore and within the nuclear compartment. This review describes recent advances in the study of HIV-1 nuclear entry, outlines the interactions of the retroviral CA protein, and discusses the challenges of investigating HIV-1 uncoating.

scholarly journals Three-dimensional MHD modeling of the solar wind structures associated with 13 December 2006 coronal mass ejection

2009 ◽  
Vol 114 (A10) ◽  
pp. n/a-n/a ◽  
Author(s):  
R. Kataoka ◽  
T. Ebisuzaki ◽  
K. Kusano ◽  
D. Shiota ◽  
S. Inoue ◽  
...  
Keyword(s):  
Solar Wind ◽  
Coronal Mass Ejection ◽  
Three Dimensional ◽  
Mhd Modeling ◽  
Mass Ejection

scholarly journals LPS Primes Brain Responsiveness to High Mobility Group Box-1 Protein

2021 ◽  
Vol 14 (6) ◽  
pp. 558
Author(s):  
Verena Peek ◽  
Lois M. Harden ◽  
Jelena Damm ◽  
Ferial Aslani ◽  
Stephan Leisengang ◽  
...  
Keyword(s):  
Inflammatory Responses ◽  
Area Postrema ◽  
High Mobility ◽  
High Mobility Group ◽  
Direct Access ◽  
Significant Release ◽  
Factor Α ◽  
Culture Supernatants

High mobility group box (HMGB)1 action contributes to late phases of sepsis, but the effects of increased endogenous plasma HMGB1 levels on brain cells during inflammation are unclear. Here, we aimed to further investigate the role of HMGB1 in the brain during septic-like lipopolysaccharide-induced inflammation in rats (LPS, 10 mg/kg, i.p.). HMGB-1 mRNA expression and release were measured in the periphery/brain by RT-PCR, immunohistochemistry and ELISA. In vitro experiments with disulfide-HMGB1 in primary neuro-glial cell cultures of the area postrema (AP), a circumventricular organ with a leaky blood–brain barrier and direct access to circulating mediators like HMGB1 and LPS, were performed to determine the direct influence of HMGB1 on this pivotal brain structure for immune-to-brain communication. Indeed, HMGB1 plasma levels stayed elevated after LPS injection. Immunohistochemistry of brains and AP cultures confirmed LPS-stimulated cytoplasmatic translocation of HMGB1 indicative of local HMGB1 release. Moreover, disulfide-HMGB1 stimulation induced nuclear factor (NF)-κB activation and a significant release of interleukin-6, but not tumor necrosis factor α, into AP culture supernatants. However, only a few AP cells directly responded to HMGB1 with increased intracellular calcium concentration. Interestingly, priming with LPS induced a seven-fold higher percentage of responsive cells to HMGB1. We conclude that, as a humoral and local mediator, HMGB1 enhances brain inflammatory responses, after LPS priming, linked to sustained sepsis symptoms.

scholarly journals Remotely distinguishing and mapping endogenic water on the Moon

2017 ◽  
Vol 375 (2094) ◽  
pp. 20150391 ◽  
Author(s):  
Rachel L. Klima ◽  
Noah E. Petro
Keyword(s):  
Solar Wind ◽  
Spatial Distribution ◽  
Solar System ◽  
The Moon ◽  
Testing Hypotheses ◽  
Origin And Evolution ◽  
Lunar Interior ◽  
Geological Features ◽  
Insight Into

Water and/or hydroxyl detected remotely on the lunar surface originates from several sources: (i) comets and other exogenous debris; (ii) solar-wind implantation; (iii) the lunar interior. While each of these sources is interesting in its own right, distinguishing among them is critical for testing hypotheses for the origin and evolution of the Moon and our Solar System. Existing spacecraft observations are not of high enough spectral resolution to uniquely characterize the bonding energies of the hydroxyl molecules that have been detected. Nevertheless, the spatial distribution and associations of H, OH − or H 2 O with specific lunar lithologies provide some insight into the origin of lunar hydrous materials. The global distribution of OH − /H 2 O as detected using infrared spectroscopic measurements from orbit is here examined, with particular focus on regional geological features that exhibit OH − /H 2 O absorption band strengths that differ from their immediate surroundings. This article is part of the themed issue ‘The origin, history and role of water in the evolution of the inner Solar System’.

Disengagement from the State in Africa: Reflections on the Experience of Ghana and Guinea

1987 ◽  
Vol 29 (1) ◽  
pp. 106-131 ◽  
Author(s):  
Victor Azarya ◽  
Naomi Chazan
Keyword(s):  
Social Life ◽  
The State ◽  
Underlying Assumption ◽  
Center Stage ◽  
Societal Response ◽  
Role Of The State ◽  
Political Studies ◽  
Cast Doubt ◽  
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Few questions have galvanized the attention of observers of African affairs in recent years as forcefully as the performance of the state on the continent. The debate on the nature of the state—its capabilities, weaknesses, external and societal connections, and impact—has come to occupy center stage in the field of African political studies. This overriding preoccupation emanates from the underlying assumption that the state constitutes a superior means for the fulfillment of economic and social aspirations; participation in its activities is deemed beneficial, and various sectors of society strive to associate with its institutions and gain access to its resources. Some recent works have cast doubt on this assumption, however, and the trend in the literature has been shifting towards an emphasis on the diminishing role of the state in African social life. However, even in these new studies the focus has been primarily on the state itself, its difficulties, incapacities, and failures, rather than on societal response to its actions.

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