Current sheet with medium scale developed turbulence and the formation of the plasma sheet of Earth''s magnetosphere and solar prominences

A current sheet model with developed medium scale turbulence has been constructed. It is suggested that regular plasma flow in the current sheet is compensated by diffusive flux and plasma mixing, leading to temperature equalization. The analyzed turbulence has the form of electrostatic vortices in which electrons and ions move with the same velocities and hence does not lead to anomalous resistivity and current dissipation. It is possible to determine the plasma pressure dependence on magnetic vector potential and to find the Grad—Shafranov equation solutions. The theory is used to explain the Earth's magnetosphere plasma sheet characteristics. It is taken into account that experimentally observed plasma velocity fluctuations in the Earth's plasma sheet and quiescent prominences are much higher than regular plasma flow velocities. The analysis of turbulent current sheet dynamics after the regular motion weakening allows to construct the prominence formation theory. The decreasing of plasma pressure in the sheet due to diffusion leads to field-aligned plasma flow and plasma tube filling by cold chromospheric plasma by the action of siphon mechanism.     

Radio observations of total solar eclipse of November 3, 1994 at Chapecó (Brzil)

Radio observations of the eclipse on November 3, 1994, were carried out at Chapecó, Brazil by using a decimetric spectrograph having high spectral and time resolution. The light curve shows that: (1) Time variation of the radio flux before the totality was more compared to that after. (2) During the totality radio emission at 1.5 GHz was observed. Advantage of high spatial resolution ( 3.2 arc sec) possible during solar eclipse enabled us to determine the height of radio emission at 1.5 GHz. (3) Microwave bursts were observed associated with metric Type III-RS bursts. The source size of one of the microwave bursts was 7 arc sec and its physical parameters have been estimated. (4) The time difference between radio and optical contacts suggested for the first time asymmetrical limb brightening at 1.5 GHz.     

Conjecture on superrotation in planetary atmospheres: A diffusion model with mixing length theory

Superrotation on Venus is discussed in the context of comparative planetary atmospheres. In our planetary system, the rigid shell component (global average) of superrotation is ubiquitous (Jupiter, Saturn, Earth, Venus, Mars, Titan). The largest equatorial values of the component are between 25 and 150 m/sec. We present a simplified, heuristic analysis, utilizing mixing length theory to describe the small scale non-linear advections of energy and angular momentum, thereby providing a closure of the dynamic system. This leads to the conjecture that the zonal velocity may be crudely estimated by

, approximating the observed planetary trends; with c the speed of sound, the parameter a being 1 or 2 for geostrophic or cyclostrophic conditions respectively, P_α an effective Prandtl number which becomes less than one when radiative cooling is important, S_o the average stability, Γ the adiabatic lapse rate and γ the ratio of specific heats.     

Cosmic ray investigation for the Voyager missions; energetic particle studies in the outer heliosphere—And beyond

A cosmic-ray detector system (CRS) has been developed for the Voyager mission which will measure the energy spectrum of electrons from 3–110 MeV and the energy spectra and elemental composition of all cosmic-ray nuclei from hydrogen through iron over an energy range from 1–500 MeV/nuc. Isotopes of hydrogen through sulfur will be resolved from 2–75 MeV/nuc. Studies with CRS data will provide information on the energy content, origin and acceleration process, life history, and dynamics of cosmic rays in the galaxy, and contribute to an understanding of the nucleosynthesis of elements in the cosmic-ray sources. Particular emphasis will be placed on low-energy phenomena that are expected to exist in interstellar space and are known to be present in the outer Solar System. This investigation will also add to our understanding of the transport of cosmic rays, Jovian electrons, and low-energy interplanetary particles over an extended region of interplanetary space. A major contribution to these areas of study will be the measurement of three-dimensional streaming patterns of nuclei from H through Fe and electrons over an extended energy range, with a precision that will allow determination of anisotropies down to 1%. The required combination of charge resolution, reliability and redundance has been achieved with systems consisting entirely of solid-state charged-particle detectors.Principal Investigator of the Voyager Cosmic Ray Experiment.     

The Effect of Spectral Shape on Clutter Standard Deviation

Many radar systems now employ wideband waveforms and noncoherent averaging techniques to reduce the scintillation of the backscatter from ground clutter. The purpose of this paper is to quantify the effects of the wideband spectral shape on the clutter standard deviation after noncoherent averaging of the received signal. Relationships are developed which quantify the clutter standard deviation for any spectral shape and any ratio of transmitted band-width to processed bandwidth.     

Estimation of Time of Arrival for Rectangular Pulses

We consider the performance of the maximum likelihood estimator (MLE) for the time of arrival of a rectangular pulse in additive white Gaussian noise. Upper and lower bounds are derived for the mean square error. These bounds are tight for both medium and large energy-to-noise ratios.     

Early Data from Aura and Continuity from Uars and Toms

Aura, the last of the large EOS observatories, was launched on July~15, 2004. Aura is designed to make comprehensive stratospheric and tropospheric composition measurements from its four instruments, HIRDLS, MLS, OMI and TES. These four instruments work in synergy to provide data on ozone trends, air quality and climate change. The instruments observe in the nadir and limb and provide the best horizontal and vertical resolution ever achieved from space. After over one year in orbit the instruments are nearly operational and providing data to the scientific community. We summarize the mission, instruments, and initial results and give examples of how Aura will provide continuity to earlier chemistry missions.     

Investigation of the Influence of Magnetic Anomalies on Ion Distributions at Mars

Using data from the Mars Express Ion Mass Analyzer (IMA) we investigate the distribution of ion beams of planetary origin and search for an influence from Mars crustal magnetic anomalies. We have concentrated on ion beams observed inside the induced magnetosphere boundary (magnetic pile-up boundary). Some north-south asymmetry is seen in the data, but no longitudinal structure resembling that of the crustal anomalies. Comparing the occurrence rate of ion beams with magnetic field strength at 400 km altitude below the spacecraft (using statistical Mars Global Surveyor results) shows a decrease of the occurrence rate for modest (< 40 nT) magnetic fields. Higher magnetic field regions (above 40 nT at 400 km) are sampled so seldom that the statistics are poor but the data is consistent with some ion outflow events being closely associated with the stronger anomalies. This ion flow does not significantly affect the overall distribution of ion beams around Mars.