2,523 research outputs found
Empirical wind model for the middle and lower atmosphere. Part 1: Local time average
The HWM90 thermospheric wind model was revised in the lower thermosphere and extended into the mesosphere and lower atmosphere to provide a single analytic model for calculating zonal and meridional wind profiles representative of the climatological average for various geophysical conditions. Gradient winds from CIRA-86 plus rocket soundings, incoherent scatter radar, MF radar, and meteor radar provide the data base and are supplemented by previous data driven model summaries. Low-order spherical harmonics and Fourier series are used to describe the major variations throughout the atmosphere including latitude, annual, semiannual, and longitude (stationary wave 1). The model represents a smoothed compromise between the data sources. Although agreement between various data sources is generally good, some systematic differences are noted, particularly near the mesopause. Root mean square differences between data and model are on the order of 15 m/s in the mesosphere and 10 m/s in the stratosphere for zonal wind, and 10 m/s and 4 m/s, respectively, for meridional wind
The quasiparticle spectral function in doped graphene
We calculate the real and imaginary electron self-energy as well as the
quasiparticle spectral function in doped graphene taking into account
electron-electron interaction in the leading order dynamically screened Coulomb
coupling. Our theory provides the basis for calculating {\it all} one-electron
properties of extrinsic graphene. Comparison with existing ARPES measurements
shows broad qualitative agreement between theory and experiment. We also
calculate the renormalized graphene momentum distribution function, finding a
typical Fermi liquid discontinuity at k_F. We also provide a critical
discussion of the relevant many body approximations (e.g. RPA) for graphene.Comment: 5 pages, 3 figure
A dynamo theory prediction for solar cycle 22: Sunspot number, radio flux, exospheric temperature, and total density at 400 km
Using the dynamo theory method to predict solar activity, a value for the smoothed sunspot number of 109 + or - 20 is obtained for solar cycle 22. The predicted cycle is expected to peak near December, 1990 + or - 1 year. Concommitantly, F(10.7) radio flux is expected to reach a smoothed value of 158 + or - 18 flux units. Global mean exospheric temperature is expected to reach 1060 + or - 50 K and global total average total thermospheric density at 400 km is expected to reach 4.3 x 10 to the -15th gm/cu cm + or - 25 percent
Electron self-energy in A3C60 (A=K, Rb): Effects of t1u plasmon in GW approximation
The electron self-energy of the t1u states in A3C60 (A=K, Rb) is calculated
using the so-called GW approximation. The calculation is performed within a
model which considers the t1u charge carrier plasmon at 0.5 eV and takes into
account scattering of the electrons within the t1u band. A moderate reduction
(35 %) of the t1u band width is obtained.Comment: 4 pages, revtex, 1 figure more information at
http://www.mpi-stuttgart.mpg.de/dokumente/andersen/fullerene
Neutral winds derived from IRI parameters and from the HWM87 wind model for the sundial campaign of September, 1986
Meridional neutral winds derived from the height of the maximum ionization of the F2 layer are compared with values from results of the HWM87 empirical neutral wind model. The time period considered is the SUNDIAL-2 campaign, 21 Sept. through 5 Oct. 1986. Winds were derived from measurements by a global network of ionosondes, as well as from similar quantities generated by the International Reference Ionosphere. Global wind patterns from the three sources are similar. Differences tend to be the result of local or transient phenomena that are either too rapid to be described by the order of harmonics of the empirical models, or are the result of temporal changes not reproduced by models based on average conditions
Simulation of neutrino and charged particle production and propagation in the atmosphere
A precise evaluation of the secondary particle production and propagation in
the atmosphere is very important for the atmospheric neutrino oscillation
studies. The issue is addressed with the extension of a previously developed
full 3-Dimensional Monte-Carlo simulation of particle generation and transport
in the atmosphere, to compute the flux of secondary protons, muons and
neutrinos. Recent balloon borne experiments have performed a set of accurate
flux measurements for different particle species at different altitudes in the
atmosphere, which can be used to test the calculations for the atmospheric
neutrino production, and constrain the underlying hadronic models. The
simulation results are reported and compared with the latest flux measurements.
It is shown that the level of precision reached by these experiments could be
used to constrain the nuclear models used in the simulation. The implication of
these results for the atmospheric neutrino flux calculation are discussed.Comment: 11 pages, 9 figure
Fluctuations of g-factors in metal nanoparticles: Effects of electron-electron interaction and spin-orbit scattering
We investigate the combined effect of spin-orbit scattering and
electron-electron interactions on the probability distribution of -factors
of metal nanoparticles. Using random matrix theory, we find that even a
relatively small interaction strength %(ratio of exchange constant and mean
level %spacing \spacing ) significantly increases -factor
fluctuations for not-too-strong spin-orbit scattering (ratio of spin-orbit rate
and single-electron level spacing 1/\tau_{\rm so} \spacing \lesssim 1), and
leads to the possibility to observe -factors larger than two.Comment: RevTex, 2 figures inserte
Tables of thermospheric temperature, density and composition derived from satellite and ground based measurements. Volume 2: Ap=20
A mass spectrometer and incoherent scatter empirical thermosphere model is used to measure the neutral temperature and neutral densities for N2, O2, O, Ar, He and H, the mean molecular weight, and the total mass density. The data is presented in tabular form
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