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Results for “protonation states”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

A comparison of the temperature and density structure in high and low speed thermal proton flows

Steady-state altitude profiles of H(+) density, drift velocity, and temperature and O(+) density and temperature were deduced for a wide range of H(+) outflow velocities from subsonic to supersonic flow for plasma densities typical of both undisturbed and trough regions of the ionsophere. Allowance was made for the effects of inertia, parallel stress, and the velocity dependence of the H(+) collision frequencies. It was found that at supersonic outflow velocities there is a decrease in H(+) temperature with increasing outflow velocity. The H(+) temperatures are substantially increased above the O(+) temperatures when H(+) is flowing, with T(H+)/T(O+) reaching a maximum ratio of about 3:1.

Raitt, W. J.↗
NASA NTRS1988

Solar proton event forecasts

The United States operates a space weather service to provide information on space hazards including solar proton events to Federal government agencies and other users who operate systems that are affected by disturbances in the upper atmosphere and interplanetary environment. The observation and prediction of solar proton events has been continuous through solar cycle 21 (1976 to 1986), establishing a base of experience that can be used in providing similar support to space operations in the 1990's. The observations, indices, alerts, and forecasts used in the service are described. Also provided is a short summary of the experience obtained from making proton event predictions in solar cycle 21 including the years 1976 to 1986.

Heckman, G. R.↗
NASA NTRS1983

Ground state energy of electrons in a static point-ion lattice

The ground state energy of a neutral collection of protons and electrons was investigated under the assumption that in the ground state configuration, static protons occupy the sites of a rigid Bravais lattice. The Wigner-Seitz method was used in conjunction with three postulated potentials: bare Coulomb, Thomas-Fermi screening, and screening by a uniform bare background charge. Within these approximations, the exact band-minimum energy and wave functions are derived. For each of the three potentials, the approximate minimum ground state energy per proton (relative to isolated electrons and protons) is, respectively, -1.078 Ry, -1.038 Ry, and -1.052 Ry. These three minima all fall at a density of about 0.60 gm/cu cm, which is thus an approximate lower bound on the density of metallic hydrogen at its transition pressure.

Styer, D. F.↗
NASA NTRS1981

Collisional excitation of electron Landau levels in strong magnetic fields

The cross sections for the excitation and deexcitation of the quantized transverse energy levels of an electron in a magnetic field are calculated for electron-proton and electron-electron collisions in light of the importance of the cross sections for studies of X-ray pulsar emission. First-order matrix elements are calculated using the Dirac theory of the electron, thus taking into account relativistic effects, which are believed to be important in accreting neutron stars. Results for the collisional excitation of ground state electrons by protons are presented which demonstrate the importance of proton recoil and relativistic effects, and it is shown that electron-electron excitations may contribute 10 to 20% of the excitation rate from electron-proton scattering in a Maxwellian plasma. Finally, calculations of the cross section for electron-proton small-angle scattering are presented which lead to relaxation rates for the electron velocity distribution which are modified by the magnetic field, and to a possible increase in the value of the Coulomb logarithm.

Langer, S. H.↗
NASA NTRS1974

Many-particle theory of nuclear systems with application to neutron star matter

The energy-density relation was calculated for pure neutron matter in the density range relevant for neutron stars, using four different hard-core potentials. Calculations are also presented of the properties of the superfluid state of the neutron component, along with the superconducting state of the proton component and the effects of polarization in neutron star matter.

Chakkalakal, D. A.↗
NASA NTRS1990

Coronal proton transport in the presence of Alfven waves and implications for impact line linear polarization

The transport of fast (about 1 MeV) protons in the corona is considered when their density and ansiotropy are sufficiently large to excite Alfven waves. The Alfven waves scatter the protons and make them almost isotropic. The Alfven wave instability remains in a marginally stable state in which the proton anisotropy is just large enough to excite Alfven waves to a level which would eliminate any greater anisotropy. The protons propagate diffusively down a coronal loop and have a path length of order 100 times their length in the absence of Alfven waves. This increases their Coulomb losses, and much higher energy protons (2-20 MeV) are required initially to produce H-alpha impact line linear polarization in the chromosphere as compared to the case in the absence of Alfven waves (about 200 keV) for loop lengths about 10 to the 9th cm. The interpretation of the observed polarization becomes less direct because it depends on more poorly known parameters than in the case of the absence of Alfven waves.

Smith, Dean F.↗
NASA NTRS2023

Quantifying the Energy Budget in the Solar Wind from 13.3 to 100 Solar Radii

A variety of energy sources, ranging from dynamic processes, such as magnetic reconnection and waves, to quasi steady terms, such as plasma pressure, may contribute to the acceleration of the solar wind. We utilize a combination of charged particle and magnetic field observations from the Parker Solar Probe (PSP) to attempt to quantify the steady-state contribution of the proton pressure, the electric potential, and the wave energy to the solar wind proton acceleration observed by PSP between 13.3 and ∼100 solar radii (R☉). The proton pressure provides a natural kinematic driver of the outflow. The ambipolar electric potential acts to couple the electron pressure to the protons, providing another definite proton acceleration term. Fluctuations and waves, while inherently dynamic, can act as an additional effective steady-state pressure term. To analyze the contributions of these terms, we utilize radial binning of single-point PSP measurements, as well as repeated crossings of the same stream at different distances on individual PSP orbits (i.e., fast radial scans). In agreement with previous work, we find that the electric potential contains sufficient energy to fully explain the acceleration of the slower wind streams. On the other hand, we find that the wave pressure plays an increasingly important role in the faster wind streams. The combination of these terms can explain the continuing acceleration of both slow and fast wind streams beyond 13.3 R☉.

J S Halekas↗
NASA NTRS1994

ATP Synthesis in the Extremely Halophilic Bacteria

The proton-translocating ATPases are multimeric enzymes that carry out a multitude of essential functions. Their origin and evolution represent a seminal event in the early evolution of life. Amino acid sequences of the two largest subunits from archaeal ATPases (A-ATPases), vacuolar ATPases (V-ATPases), and FOF1-ATP syntheses (FATPases) suggest these ATPases evolved from an ancestral vacuolar-like ATP syntheses. A necessary consequence of this notion is that the A-ATPases are ATP syntheses. With the possible exception of the A-ATPase from Halobacterium salinarium. no A-ATPase has been demonstrated to synthesize ATP. The evidence for this case is dubious since ATP synthesis occurs only when conditions are distinctively unphysiological. We demonstrated that ATP synthesis in H.saccharovorum is inconsistent with the operation of an A-type ATPase. In order to determine if this phenomenon was unique to H. saccharovorum, ATP synthesis was examined in various extremely halophilic bacteria with the goal of ascertaining if it resembled what occurred in a. saccharovorum, or was consistent with the operation of an A-type ATPase. A-, V-, and F-type ATPases respond singularly to certain inhibitors. Therefore, the effect of these inhibitors on ATP synthesis in several extreme halophiles was determined. Inhibitors that either blocked or collapsed proton-gradients inhibited the steady state synthesis of ATP thus verifying that synthesis took place at the expense of a proton gradient. Azide, an inhibitor of F-ATPases inhibited ATP synthesis. Since the arginine-dependent synthesis of ATP, which occurs by way of substrate-level phosphorylation, was unaffected by azide, it was unlikely that azide acted as an "uncoupler." N -ethylmaleimide and nitrate, which inhibit V- and A-ATPases, either did not inhibit ATP synthesis or resulted in higher steady-state levels of ATP. These results suggest there are two types of proton-motive ATPases in the extreme halophiles (and presumably in other Archaea). One, the V-like enzyme which, provides protons that are subsequently used for solute translocation. The other ATPase is the familiar and ubiquitous F-ATPase that functions as a reversible proton pump and is the ATP Synthase in the extreme halophiles. Thus, while the suggested evolution of the proton -translocating ATPases accounts for the relationship among these ATPases, this scheme does not account for the presence of F-ATPases in the Archaea. Discounting lateral gene transfer, perhaps an F-type ATPase evolved before the eucaryal-archaeal and bacterial bifurcation. The presence of V-type ATPases in the Bacterial Domain is consistent with this suggestion. Finally, it is of interest to note that if an F-type ATPase appeared before the bifurcation, an endosymbiotic event need not be invoked to explain the presence of F-ATPases in the Eucarya.

Hochstein, Lawrence I.↗
NASA NTRS1989

The abundances of elements and isotopes in the solar wind

Solar wind abundances have now been measured for eleven elements and the isotopes of the noble gases. Aside from solar wind protons and alpha particles, which have been studied extensively since the 1960's, information for heavier elements is limited. Nevertheless, two effects stand out. First is the enrichment of abundances of elements with low first ionization potential (FIP), most likely the combined result of an atom-ion separation process in the upper chromosphere, and a marginal coupling of low-charge-state heavy ions to protons and alphas during the acceleration of the solar wind. Second, there is variability in the solar wind composition over a whole range of time scales. Recent measurements carried out in the earth's magnetosheath during times that included high-speed coronal-hole-associated flows indicate a significantly lower overabundance of low FIP elements. Given the fact that the He/H ratio is remarkably constant in the coronal hole solar wind, this result suggests that both enrichment and variability are reduced in such flows.

Gloeckler, George↗
NASA NTRS1994

The proton cyclotron instability and the anisotropy/B inverse correlation

Spacecraft observations in the strongly compressed subsolar magnetosheath show an inverse correlation between the proton temperature anistrophy (T(sub perpendicular to p)/T(sub parallel to p) greater than 1 where perpendicular to and parallel to denote directions perpendicular and parallel to the background magnetic field) and the parallel proton beta (beta(sub parallel to p). This manuscript uses one-dimensional hybrid simulations of the proton cyclotron anisotropy instability in homogeneous electron-proton plasmas to study this correlation which may represent a limited closure relation for fluid theories of anisotropic space plasmas. The emphasis is on driven simulation which increase the temperature anisotropy by periodically reducing the magnetic-field-aligned velocities of the protons. The late-time states from ensembles of both initial value and driven simulations yield very similar expressions for the proton anisotropy/beta(sub parallel to P) inverse correlation, and provide a basis for explaining differences between sheath observations from different spacecraft. The driven simulations also yield expressions for the maximum instability growth rate and the fluctuating field energy as functions of beta (sub parallel to p) and a parameter characterizing the anisotropy driver.

Gary, S. Peter↗
NASA NTRS1991

Pair-density transitions in accretion disk coronae

The thermal and e(+)e(-)-pair equilibrium structure of two-temperature disk coronae above a cool (about 10 exp 6 K) disk around a black hole of 10 solar masses are investigated. Soft photons are assumed to be amply supplied from the cool disk. Two-pair thermal equilibrium points are found for a given proton column density: the low state with very small pair density and the high state dominated by pairs. Both states are thermally unstable, while for perturbations in pair density the high state is unstable and the low state is stable. Two possible scenarios are discussed for the fate of a two-temperature corona. When the proton optical depth is relatively small (e.g., less than 1) and the temperature of input soft photons is low (e.g., less than 10 exp 6 K), the corona will undergo a limit cycle between the high state and the low state on a time scale of milliseconds. As a consequence of Compton scattering of the soft photons, the emergent spectrum in the high state is rather flat with a big Wien bump at about 100 keV, whereas it is composed of a power-law component in the low state. Some observational consequences are briefly discussed in connection with the high-low spectral transition in Cyg X-1.

Kusunose, Masaaki↗