A cosmochemical view of cosmic rays and solar particles

The composition of cosmic rays and solar particles is reviewed with emphasis on the question of whether they are representative samples of Galactic and solar matter. The composition of solar particles changes with energy and from flare to flare. A strong excess of heavy elements at energies below a few MeV/nuc decreases with energy, and at energies above 15 MeV/nuc the composition of solar particles resembles that of galactic cosmic rays somewhat better than that of the solar atmosphere. The elements Ne through Pb have remarkably similar abundances in cosmic ray sources and in the matter of the solar system. The lighter elements are depleted in cosmic rays, whereas U and Th may be enriched or not, depending on whether the meteoritic or solar abundance of Th is used. Two prototype sources of cosmic rays are considered: gas with solar system composition but enriched in elements with Z > 8 during acceleration and emission (by analogy with solar particle emission), and highly evolved matter enriched in r-process elements such as U, Th and transuranic elements. The energy-dependence of cosmic ray composition suggests that both sources may contribute at different energies.Miller Institute Professor, 1972–73.     

Calculation of Probability of Detection with Target Scintillation

This paper presents a computational method for the calculation of probability of detection using measured radar target cross-section data. The described method can also be used for probability of detection calculations when the radar target cross section follows a specified probability density function. Using the computational procedure of the paper, a number of curves are generated which can be used for probability of detection calculations with exponential and Gaussian radar target cross-section distributions. The results obtained using theoretical distributions are compared with the corresponding results using actual target cross-section measurements. The results of computer runs are compared to the corresponding values in the literature where available.     

A Concept of Position Fixing by a Passive Mode Navigation Satellite System

A position fix in a passive mode using satellites usually necessitates an expensive computer or lengthy hand calculation. This is the largest drawback of passive navigation and it would be more desirable if the user could find his position by a mere glance at a chart and table, as one uses Loran. The first step toward this goal is to use a synchronous satellite because it simplifies the problem. The next step is to find the position of the user by a Loran type of chart, which is universal, and correct this apparent position by looking at a special table which is made according to the amount of perturbation of both the satellite and the user's position. An example of the position fix along the route between Yokohama to Hawaii is shown. The concept can be extended to orbiting satellites due to the rules which govern the motion of satellites, if the fix accuracy is in the order of 2 to 5 miles. This method should be more accurate than the common sextant and more practical due to the fact that the satellite can be used at any time and in any weather. As a total system, it will be better than Omega because it could provide additional navigation information such as communication or traffic control by using satellites.     

An analysis of Martian photometry and polarimetry

The physical parameters that influence the photometric and polarimetric properties of a solid are enumerated and used to guide a comparison of laboratory measurements with observations of Mars. Both the bright and dark areas of Mars are found to be covered by a fine powder. Furthermore, they appear to have a very similar chemical composition. It is argued that goethite is a major constituent of both regions. The particles on the bright areas are characterized by an average particle radius of 25 , while those on the dark areas have a mean size of 100 outside of the period of seasonal darkening and about 200 near the peak of the darkening. The seasonal darkening of the dark areas is the result of a change in the average particle dimension without an accompanying chemical change.The Martian atmosphere has much less of an influence on the photometric and polarimetric observations than was previously supposed. The observed lack of contrast in the blue appears to be largely the result of an intrinsic loss of surface contrast, and not an effect of a hypothetical atmospheric blue haze.

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Résumé Les paramètres physiques qui influencent les propriétés photométriques et polarimétriques d'un solide sont énumérés et utilisés pour conduire une comparaison entre des mesures de laboratoire et des observations de Mars. On trouve que les régions brillantes et les régions sombres de Mars sont couvertes d'une fine poudre. En outre, elles paraissent avoir des compositions chimiques très semblables. Il est soutenu que la goethite est un constituant majeur des deux régions. Les particules des régions brillantes sont caractérisées par un rayon moyen de 25 , tandis que celles des régions sombres ont une taille moyenne de 100 en dehors de la période d'assombrissement saisonnier, et d'environ 200 près du maximum d'assombrissement. L'assombrissement saisonnier des régions sombres est le résultat d'une variation de la dimension moyenne des particules, non accompagné d'un changement chimique.L'influence de l'atmosphère Martienne sur les observations photométriques et polarimétriques est bien inférieure à ce qui était supposé antérieurement. Le manque de contraste que l'on observe dans le bleu, parait être principalement une conséquencede la perte de contraste de surface, et non pas un effet d'un hypothétique halo atmosphérique bleu.

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This work was supported in part by grants NGR-09-015-023 and NGR-33-010-082 from the National Aeronautics and Space Administration. A preliminary account was published as Smithsonian Astrophysical Observatory Special Report 258 (1967). This paper is dedicated to the memory of V. V. Sharonov.     

Comments on Stabilization of a Satellite

An expression is derived for the cost resultingfrom the stabilization of a satellite using aspecific optimal control (SOC). An exampleis given in which the optimal and SOC yieldvirtually identical costs.     

Dissipation of magnetic fields in active galactic nuclei

A model for the emission processes causing rapid variability (less than one day) in active galactic nuclei is developed. Relativistic electron beams escape from reconnection sheets in coronae of accretion disks and excite plasma turbulence with a typical frequency , which depends on the electron number densityn (see also the contribution by R. van Oss). The finite lengths of different beams emerging from different reconnection sheets allows that the waves arecoherently scattered to frequencies ²_pe. For Lorentz factors 10³ and densities typical for disk coronaen10⁶ cm ^–3 (derived from iron line observations) one easily reaches the optical, frequency range. The time scale of the variability is then caused by the relaxation of the electron beams. Likewise, this model explains the very rapid variability in the X-ray (less than 10 minutes) by changing the parameters slightly. According to this scenario the higher the variable frequency is, the closer to the central black hole it should originate.     

Search radar detection and track with the Hough transform. II.detection statistics

For pt.I see ibid., vol.30, no.1, (Jan.1994). This paper describes the calculation of P_F and P_D for the Hough transform technique when the primary threshold crossings are weighted by their power before transforming (i.e., noncoherent integration). After expressions for P_F and P_D are derived, we examine the question of optimal granularity of the Hough accumulator space. We also investigate the relationship between primary and secondary thresholds and its effect on detectability     

EUV spectroscopy as a plasma diagnostic

The EUV wavelength regions is rich in emission lines from the transition region and the corona. Spectroscopic techniques have been used extensively to determine the physical conditions in the solar atmosphere for such diverse phenomena as coronal holes, active regions, sunspots, flares, etc. The diagnostics and dynamics of plasmas, both homogeneous and inhomogeneous plasmas, are reviewed. The future projects such as the CDS and SUMER instruments on SOHO have been discussed as they cover EUV wavelength region and will provide a wealth of observational data with excellent spatial, spectral, and temporal resolution.     

A localizer design to improve missed approach guidance

A novel VHF localizer system has been designed, built and successfully tested to provide increased reliability and safety of commercial and general aviation air transportation. Additional benefits are more precise tracks for aircraft executing a missed approach, reduced volume of the airspace needed for missed approaches, and reduced sizes of areas affected by noise. The design uses contemporary instrument landing system (ILS) hardware to provide dual independent front and back course directional localizer operation with two carriers in the receiver passband offset 4 kHz from the nominal carrier frequency. An example is given of an application and solution to an ILS problem at Reno, NV. Relevant data are presented