Large electric fields in the magnetosphere

In several regions of the magnetosphere, perpendicular and/or parallel electric fields are found to be orders-of-magnitude larger than expected from simple considerations. Problems associated with these large fields that may be amenable to study through computer simulations are discussed. Regions in which large electric fields are observed include: a) The auroral ionosphere, where Langmuir soliton-like structures have been measured to contain plasma frequency oscillations as large as 500 mV/m, the envelopes of which have parallel electric fields of 100 mV/m lasting for fractions of a millisecond; b) The auroral acceleration region, where electrostatic shocks have been observed to contain perpendicular fields as large as 1000 mV/m and parallel fields as large as 100 mV/m, and where double layers having parallel fields up to 10 mV/m have been observed; c) The high latitude boundary of the plasma sheet, where turbulent electric fields as large as 100 mV/m have been seen along with quasi-static fields of 5–10 mV/m; d) Inside the plasma sheet, where fields of 5–10 mV/m have frequently been observed; e) The bow shock, where turbulent fields as large as 100 mV/m and d.c. fields of 5 mV/m normal to the shock have been seen.also Physics Department     

Implicit Adaptive Control for a Class of MIMO Systems

Two implicit model reference adaptive control algorithms for multi-input multi-output systems are developed. These algorithms do not require either satisfaction of the perfect model following conditions or explicit parameter identification. The first algorithm ensures asymptotic stability of the output error provided that the output stabilized plant transfer matrix is strictly positive real. The second algorithm guarantees a bounded error under less restrictive conditions. The algorithms are applied to the lateral axis of an F-8 aircraft.     

Big Bang Nucleosynthesis Calculation

I review standard big bang nucleosynthesis and some versions of nonstandard BBN. The abundances of the primordial isotopes D, He-3, and Li-7 produced in standard BBN can be calculated as a function of the baryon density with an accuracy of about 10%. For He-4 the accuracy is better than 1%. The calculated abundances agree fairly well with observations, but the baryon density of the universe cannot be determined with high precision. Possibilities for nonstandard BBN include inhomogeneous and antimatter BBN and nonzero neutrino chemical potentials.     

Red edge measurements for remotely sensing plant chlorophyll content

The feasibility of using the wavelength of the maximum slope of the red edge of leaf reflectance spectra (λ_re) as an indication of plant chlorophyll status was examined in the laboratory for single leaves of several species. λ_re for each sample was determined by derivative reflectance spectroscopy. A high positive correlation was found between λ_re and leaf chlorophyll content for all species, although there were some differences in the quantitative nature of the relationship for plants of different types. The position of the red edge was found to be unaffected by simulated change in ground cover, but multiple leaf layers produced a shift in its position. Appropriate spectral measurements and processing for obtaining useful information from the red edge are discussed, and the potential of the red edge in relation to other spectral measurements is considered.     

Orbit prediction and shuttle rendezvous strategy for eureca

The European Retrievable Carrier (EURECA) is a platform to be launched, deployed and retrieved in low Earth orbit by the Space Shuttle.A newly developed analytical orbit prediction method is described which meets the severe requirements for EURECA's orbit propagation. It is based on an averaging procedure including the Earth's zonal harmonics J₂, J₃ and J₄ and a refined treatment of the air drag perturbation where EURECA's large solar panels are taken into account. Some orbit prediction results are included.In order to offer more flexibility for the Shuttle retrieval of EURECA, it is proposed to execute a part of the rendezvous manoeuvres by EURECA. A corresponding strategy is described.     

A Statistical Glint/Radar Cross Section Target Model

We review the details of the glint (angular scintillation) problem in electromagnetic scattering. These results are employed to develop a statistical glint and radar cross section (RCS) target model featuring the correct glint probability density function, the correct time correlations of RCS and glint, and the correct cross correlation between RCS and glint. This model is suitable for simulation applications, and an implementation scheme for a glint/RCS signal generator is included.     

Influence of hypergravity on fish inner ear otoliths: I. Developmental growth profile.

Inner ear stones (otoliths) of larval cichlid fish Oreochromis mossambicus were marked with the calcium-tracer alizarin-complexone (AC) at 1 g earth gravity before and after a 3, 7, 14 or 21 days stay of the animals at hypergravity conditions (hg; 3 g, centrifuge). After the experiment, the otoliths' area between the two AC-labellings was measured with regard to size and asymmetry (size difference between the left and the right stones). Both utricular and saccular otoliths (lapilli and sagittae, respectively) continued growing in a linear way at hg, but growth was significantly slowed down as compared to parallely raised 1 g-control specimens. In case of bilateral asymmetry between the corresponding otoliths its formation in hg-animals became reduced as compared to the 1 g controls. The reduction of asymmetry was much more pronounced in the sagittae than in the lapilli. The latter result supports an earlier hypothesis, according to which especially a low sagittal asymmetry has a functional advantage. In general, the results strongly suggest that otolith growth is continuously regulated in dependence of the environmental gravity vector.     

Relay balloon

A relay balloon system for long-duration or large-area observations is described. The system consists of a balloon for scientific observations and a relay balloon for a data-relay terminal between a ground station and the balloon for observation. The system was successfully applied to the observation of electric-power fields (50 and 60 Hz) over the Pacific ocean. The maiximum distance between two balloons was about 1100 km and that between the Sanriku Balloon Center and the main balloon for the observation was about 1300 km.