Behavior of thermal plasma in the ionosphere and magnetosphere

Models of ion flow in the topside ionosphere were developed. These models took both H(+) and O(+) into account and permitted various parameter studies to be made affecting H(+) escape in polar winds. Extensive computer programs were written to display the measured electron density profiles in ways useful to geophysical analysis. The relationship between the location of the plasmapause as it is found in the equatorial plane and the location of the ionospheric trough was also investigated

Studies of the structure of the plasmasphere as seen by radiosounder measurements aboard the Alovetti-satellite

The structure of the plasmasphere was studied as seen by radiosounder measurements aboard the Alovetti-2 satellite. Magnetic tape data files were obtained from the NASA Ames Research Center to give a reasonably complete set of high latitude electron density profiles. Considerable effort was expended to develop models of ion flow in the topside ionosphere. These models took both H(+) and O(+) into account and permitted various parameter studies to be made of the various factors which affect H(+) escape in polar wind flows. The results of these studies are included. Extensive computer programs were written to display the measured electron density profiles in ways useful to geophysical analysis. The expected mid-latitude trough was easily discernable in the nightime ionosphere at locations expected from similar observations of the plasmapause. In the dayside ionosphere, however, it proved extremely difficult to find any trough-like phenomena. Using the previously developed computer models, it was possible to study the region where the plasmapause appeared to be absent. It was found that over much of the dayside, large fluxes were computed well inside the plasmapause extending down to L-shells as low as 2.5

The Reduction of Ionograms from the Bottomside and Topside Scientific Report No. 230

Reduction of ionograms to electron density height profiles on digital compute

Proceedings of the 1st Space Plasma Computer Analysis Network (SCAN) Workshop

The purpose of the workshop was to identify specific cooperative scientific study topics within the discipline of Ionosphere Magnetosphere Coupling processes and to develop methods and procedures to accomplish this cooperative research using SCAN facilities. Cooperative scientific research was initiated in the areas of polar cusp composition, O+ polar outflow, and magnetospheric boundary morphology studies and an approach using a common metafile structure was adopted to facilitate the exchange of data and plots between the various workshop participants. The advantages of in person versus remote workshops were discussed also

Simultaneous measurement of ion and neutral motions by radar and optical techniques

The results of simultaneous thermospheric neutral wind and ionization drift measurements from near College, Alaska (L = 5.6, Λ = 65°) are presented. The neutral wind data were obtained by observing the Doppler shift of the 6300 Å atomic oxygen line with the 15‐cm Fabry‐Perot interferometer of the Michigan Airglow Observatory which is located temporarily at Ester Dome, Alaska. Ionization drifts were measured by the Chatanika incoherent scatter radar facility. These simultaneous measurements indicate that in the premidnight sector both the neutral wind and the ionization drift are generally westward. This westward ionization drift is consistent with the general magnetospheric convection pattern but the measured neutral wind is in a direction opposite to the diurnal pressure gradients and thus must be driven by ion drag. In the postmidnight sector the ionization drift turns eastward while the neutral wind direction turns south. Again, the ion drift is consistent with previously published results; the reasons for the absence of significant zonal neutral winds and the significant southward meridional wind in the postmidnight sector are not well understood at this time, but are probably a combination of a decrease in the ion drag force following magnetic midnight, Coriolis force, and pressure gradients due to both the diurnal and auroral heat sources. Copyright 1974 by the American Geophysical Union

G-protein signaling: back to the future

Heterotrimeric G-proteins are intracellular partners of G-protein-coupled receptors (GPCRs). GPCRs act on inactive Gα·GDP/Gβγ heterotrimers to promote GDP release and GTP binding, resulting in liberation of Gα from Gβγ. Gα·GTP and Gβγ target effectors including adenylyl cyclases, phospholipases and ion channels. Signaling is terminated by intrinsic GTPase activity of Gα and heterotrimer reformation — a cycle accelerated by ‘regulators of G-protein signaling’ (RGS proteins). Recent studies have identified several unconventional G-protein signaling pathways that diverge from this standard model. Whereas phospholipase C (PLC) β is activated by Gαq and Gβγ, novel PLC isoforms are regulated by both heterotrimeric and Ras-superfamily G-proteins. An Arabidopsis protein has been discovered containing both GPCR and RGS domains within the same protein. Most surprisingly, a receptor-independent Gα nucleotide cycle that regulates cell division has been delineated in both Caenorhabditis elegans and Drosophila melanogaster. Here, we revisit classical heterotrimeric G-protein signaling and explore these new, non-canonical G-protein signaling pathways

PIP2-Binding Site in Kir Channels: Definition by Multiscale Biomolecular Simulations†

Phosphatidylinositol bisphosphate (PIP(2)) is an activator of mammalian inwardly rectifying potassium (Kir) channels. Multiscale simulations, via a sequential combination of coarse-grained and atomistic molecular dynamics, enabled exploration of the interactions of PIP(2) molecules within the inner leaflet of a lipid bilayer membrane with possible binding sites on Kir channels. Three Kir channel structures were investigated: X-ray structures of KirBac1.1 and of a Kir3.1-KirBac1.3 chimera and a homology model of Kir6.2. Coarse-grained simulations of the Kir channels in PIP(2)-containing lipid bilayers identified the PIP(2)-binding site on each channel. These models of the PIP(2)-channel complexes were refined by conversion to an atomistic representation followed by molecular dynamics simulation in a lipid bilayer. All three channels were revealed to contain a conserved binding site at the N-terminal end of the slide (M0) helix, at the interface between adjacent subunits of the channel. This binding site agrees with mutagenesis data and is in the proximity of the site occupied by a detergent molecule in the Kir chimera channel crystal. Polar contacts in the coarse-grained simulations corresponded to long-lived electrostatic and H-bonding interactions between the channel and PIP(2) in the atomistic simulations, enabling identification of key side chains

Ionospheric gas dynamics of satellites and diagnostic probes

The gas dynamics of interactions of a tenuous ionosphere with moving satellites and probes that have bearings on the diagnostics of the ionosphere are discussed. Emphasis is on the cases where the body is moving at mesothermal speeds, namely intermediate between the thermal speeds of ions and electrons of the ambient ionosphere. Methods of collision-free plasma kinetics with self-consistent field are used. The development of the topics for discussion starts with stationary Langmuir probe which entails the basic mechanism of body-plasma interaction that becomes further intricated as the body moves at a higher and higher speed. Applications of the theory of plasma interaction to meteors which move in the ionosphere are also presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43801/1/11214_2004_Article_BF00212707.pd