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.     

Some Electrical/Electronic Areas Requiring Emphasis in Preparation for Future Space Programs

A panel session held at the 1965 Aerospace Conference, Houston,Tex., June 23, 1965. Panelists discussed Life-Suppport interfaces with Electric Power; Communications; Navigation; System Integration for Future Space Programs; and Reliability.     

Application of a Highly Parallel Processor to Radar Data Processing

The application of a highly parallel computer known as PEPE (Parallel Element Processing Ensemble) to radar data processing is described. The PEPE computer consists of a large number of identical processing elements which operate in parallel and are controlled by a common control unit. Each of the processing elements is assigned to a particular radar target such that many targets can be tracked in parallel. PEPE is designed to augment a conventional computer rather than to stand alone. The total data processing load associated with a radar tracking system is distributed between PEPE and the sequential machine in a manner than maximizes the overall system efficiency and desensitizes the system performance to fluctuations in traffic levels. The use of PEPE provides very high data processing throughput potential to a radar data processing system.     

Theory of Errors of a Multigimbal, Elastically Supported, Tuned Gyroscope

An elastically supported, tuned gyroscope is a complex device, but experience has shown that it can be represented by mathematical models by means of which practically all of its characteristic errors can be analyzed and predicted with good accuracy. The gyro angular transfer function, derived in [1], serves as an excellent basis of evaluation of errors due to asymmetries of the gimballing system and effects of rotor angular offsets. The gyro translational transfer function, derived in this paper, may be used in the analysis of errors caused by linear acceleration inputs.     

VLF Loop Antennas for Pulse Reception

This paper describes an approach to the realization of a VLF loop-type antenna system. The theoretical analysis is applied to a four-loop system for Loran-C reception.     

A Clutter Reduction Technique for Random Signal Radars

The performance of certain radars is degraded in environments with significant clutter returns, and since the clutter is signal-generated, increasing the transmitted power does not improve the situation. However, changing the pulse width and pulse period of the transmitted signal can increase the input signal-to-interference ratio. In this correspondence, the transmitted signal is made up of pulses of random waveforms and the receiver is a correlator where the reference signal extends over many pulses. An expression for input signal-to-interference ratio as a function of pulse width and period is obtained for the case of a distributed target. This expression could be maximized by any of several methods, but to further elucidate the clutter reduction technique, contour plots of the input signal-to-interference ratio are presented.     

Hale-Bopp and Its Sodium Tails

The sodium emissions have been observed in several new and long-period comets, but only for comet Mrkos 1957d (Nguyen-Huu-Doan, 1960) was a sodium tail detected on a Schmidt plate obtained with a objective prism. Comet Hale-Bopp 1995 O1 offered the first great opportunity to get an image of a long sodium tail. It was more than 3 × 10⁷ km long, defined as a third type of tail, as it was composed only of neutral atoms (Cremonese, 1997a). After the discovery of the sodium tail another team announced it had observed it (Wilson et al., 1998), but it was soon realized they had seen a different sodium tail. The image of Wilson et al. (1998) showed a very diffuse sodium tail superimposed on the dust tail, most likely due to the release of sodium atoms from dust particles. It was different from the narrow tail found in the image obtained by the European Hale-Bopp Team and its position angle was 15-20 degrees lower. Spectroscopic observations have been performed on the dust tail, at different beta values, and along the narrow sodium tail showing that the sodium emissions had very different line profiles. The analysis of these profiles will yield important insights into the sources in the inner coma and in the dust tail. This work will report on preliminary analysis of both sodium tails and emphasize the high-resolution spectroscopy performed on the dust tail. This revised version was published online in June 2006 with corrections to the Cover Date.     

Coronal Heating: a Comparison of Ion-cyclotron and Gravity Damping Models

SOHO/UVCS data indicate that minor ions in the corona are heated more than hydrogen, and that coronal heating results in T_⊥ larger than T_‖. Analogous behavior has been known from in situ measurements in solar wind for many years. Here we compare and contrast two mechanisms which have been proposed to account for the above behavior: ion-cyclotron resonance and gravity damping. This revised version was published online in June 2006 with corrections to the Cover Date.