5,859 research outputs found
Multidisciplinary research in space-related science and technology Semiannual status report, 1 May - 1 Nov. 1965
Electrostatic and electrokinetic phenomena, thermal conductivity of sodium vapor, impedance characteristics of irradiated thin films, and ultrasonic paramagnetic resonanc
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Electron loss rates from the outer radiation belt caused by the filling of the outer plasmasphere: The calm before the storm
Measurements from seven spacecraft in geosynchronous orbit are analyzed to determine the decay rate of the number density of the outer electron radiation belt prior to the onset of high-speed-stream-driven geomagnetic storms. Superposed-data analysis is used with a collection of 124 storms. When there is a calm before the storm, the electron number density decays exponentially before the storm with a 3.4-day e-folding time: beginning about 4 days before storm onset, the density decreases from ∼4 × 10−4 cm−3 to ∼1 × 10−4 cm−3. When there is not a calm before the storm, the number density decay is very small. The decay in the number density of radiation belt electrons is believed to be caused by pitch angle scattering of electrons into the atmospheric loss cone as the outer plasmasphere fills during the calms. This is confirmed by separately measuring the density decay rate for times when the outer plasmasphere is present or absent. While the radiation belt electron density decreases, the temperature of the electron radiation belt holds approximately constant, indicating that the electron precipitation occurs equally at all energies. Along with the number density decay, the pressure of the outer electron radiation belt decays, and the specific entropy increases. From the measured decay rates, the electron flux to the atmosphere is calculated, and that flux is 3 orders of magnitude less than thermal fluxes in the magnetosphere, indicating that the radiation belt pitch angle scattering is 3 orders weaker than strong diffusion. Energy fluxes into the atmosphere are calculated and found to be insufficient to produce visible airglow
The Effective in Matter
In this paper we generalize the concept of an effective for
disappearance experiments, which has been extensively used
by the short baseline reactor experiments, to include the effects of
propagation through matter for longer baseline
disappearance experiments. This generalization is a trivial, linear combination
of the neutrino mass squared eigenvalues in matter and thus is not a simple
extension of the usually vacuum expression, although, as it must, it reduces to
the correct expression in the vacuum limit. We also demonstrated that the
effective in matter is very useful conceptually and
numerically for understanding the form of the neutrino mass squared eigenstates
in matter and hence for calculating the matter oscillation probabilities.
Finally we analytically estimate the precision of this two-flavor approach and
numerically verify that it is precise at the sub-percent level.Comment: 9 pages, 6 figures, 1 table, comments welcom
Sensitivity of full-sky experiments to large scale cosmic ray anisotropies
The two main advantages of space-based observation of extreme energy
( eV) cosmic rays (EECRs) over ground based
observatories are the increased field of view and the full-sky coverage with
nearly uniform systematics across the entire sky. The former guarantees
increased statistics, whereas the latter enables a clean partitioning of the
sky into spherical harmonics. The discovery of anisotropies would help to
identify the long sought origin of EECRs. We begin an investigation of the
reach of a full-sky space-based experiment such as EUSO to detect anisotropies
in the extreme-energy cosmic-ray sky compared to ground based partial-sky
experiments such as the Pierre Auger Observatory and Telescope Array. The
technique is explained here, and simulations for a Universe with just two
nonzero multipoles, monopole plus either dipole or quadrupole, are presented.
These simulations quantify the advantages of space-based, all-sky coverage.Comment: 11 pages, 8 figure
The role of fracture mechanics in the design of fuel tanks in space vehicles
With special reference to design of fuel tanks in space vehicles, the principles of fracture mechanics are reviewed. An approximate but extremely simple relationship is derived among the operating stress level, the length of crack, and the number of cycles of failure. Any one of the variables can be computed approximately from the knowledge of the other two, if the loading schedule (mission of the tank) is not greatly altered. Two sample examples illustrating the procedures of determining the allowable safe operating stress corresponding to a set of assumed loading schedule are included. The selection of sample examples is limited by the relatively meager available data on the candidate material for various stress ratios in the cycling
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