C.J. Zamlutti

Ionospheric Plasma Bubble Climatology Over Brazil Based on 22Years (1977-1998) of 630 nm Airglow Observations

Abstract The frequency of occurrence of the large-scale ionospheric plasma depletions, or plasma bubbles, over Cachoeira Paulista—CP (45°W, 33°S, 28°S dip), with solar activity, season, and geomagnetic activity, during the period of 1977–1998, is studied here based on 934 days of scanning photometers and imagers data of the atomic oxygen 630 nm nocturnal airglow. The bubble occurrence for the entire period of study shows maximum rate of 86% in January and 11% in May. The seasonal pattern of the bubble occurrence shows up as broad a maximum and a minimum centered around summer and winter months, respectively. While during the high-solar activity the maximum extends from September to April, for the low-activity period it extends from October to March. The average sunspot number for the solar maximum (minimum) for the data of this work is 129.9 (33.1). Significant increase of bubble occurrence (by ∼80%) from low to high solar activity levels is found to occur in the present analysis only during the equinoctial months of March–April and September–October. The post-sunset plasma bubble occurrence over Cachoeira Paulista is found to decrease with increase of Kp that precedes the sunset by >4 h , suggesting the role of disturbance dynamo electric field to inhibit its development. Increase of Kp during sunset hours can increase the bubble occurrence as a possible effect of prompt penetration electric field. These results are presented and discussed in this paper.

O(1S) and O(1D) quantum yields from rocket measurements of electron densities and 557.7 and 630.0 nm emissions in the nocturnal F-region

Abstract The quantum yields ƒ( 1 D) and ƒ( 1 S) of the atomic oxygen excited states O( 1 D) and O( 1 S), respectively, from dissociative recombination in the nocturnal F-region are determined utilizing rocket airglow (OI 630 nm and OI 557.7 nm) and electron density data obtained in two experiments that were carried out at Natal (geogr. 5.8°S, 35.2°W), Brazil, on 11 December 1985 and 31 October 1986. Using the 557.7 and 630 nm airglow data from the second experiment Takahashi et al. (1990, Planet. Space Sci . 38 , 547) calculated the ratio ƒ( 1 S)/tf( 1 D). From a different approach we utilize in this paper the airglow volumetric emission rate and electron density to calculate ƒ( 1 S) and ƒ( 1 D), individually, which are compared with the previously published results from in situ and laboratory measurements. Our results show ƒ( 1 S) to be height dependent. In the second experiment it varied from 1.96 × 10 −2 at 190 km to 1.33 × 10 −1 at 315 km with an average value of 0.053. The average value for the first experiment was 0.041. The ƒ( 1 D) magnitude was also found to vary significantly with altitude, its value increasing both upwards and downwards from 250 km where it attains a minimum of about 0.77.

Horizontal gradients of the nocturnal OI 557.7 nm and OI 630 nm photoemission rates in the equatorial ionosphere based on rocket electron density data

Altitude profiles of the nocturnal atomic oxygen 557.7 nm and 630.0 nm photoemission rates were calculated based on in-situ ionospheric electron density data obtained from a rocket experiment carried out on 31 May 1992, 23:52 LT, at the Brazilian equatorial rocket launching facility Alcântara (Geogr. 2°19′S; 44°22′W). The onboard instrumentation utilized for the electron density measurements was a Langmuir plasma probe and the vehicle was a Brazilian Sonda III rocket. Horizontal gradients of the photoemission rates were then calculated at 5 km height intervals based on the trajectory upleg and downleg photoemission rates. The resulting gradients are discussed in this paper. At some height levels these gradients resulted to be very large, namely, over a factor of two. The airglow resulting from the atomic oxygen dissociative recombination is generally assumed to stem from an uniform emitting layer. We show that the integrated airglow intensity, in Rayleighs, along the upleg and downleg portions of the trajectory are seen to differ from each other both for the red (∼10% difference) and the green lines (∼50% difference) which shows that in this case the red line emitting layer is about 5 times closer to uniformity than that of the green line.

Transport equations for multicomponent isotropic and anisotropic high speed space plasmas

Abstract This paper presents revised sets of the 13-and 16-moment systems of transport equations using the flow form, which may eventually be more convenient in the studies of interhemisphere transport of plasma, polar wind, solar wind, etc. This alternative form can be recast into the traditional well known forms existing in the literature. A discussion of the structural aspects of the equations is presented.

Atmospheric wave observations at Arecibo

Abstract Multiple pulse incoherent scatter experiments, observing E -region altitudes with height resolution better than 2.4 km, have been carried out at Arecibo from August 1972 to January 1973. Neutral temperature, ion-neutral collision frequency and drift velocities were obtained. The results showed an oscillatory behavior of the neutral atmosphere. Evidences of non-linearities of the atmospheric oscillations are explored. They help to determine the period of the tidal mode consistent with the semi-diurnal tide predicted by the theory.

Long range collision effects for drifting velocity distributions

Abstract The interparticle force acting during a binary encounter is usually modeled by a potential of the inverse power law form. The influence of one particle on the other decays with distance and here the effects felt around the so called cutoff distance are considered. Attention is given to the Fokker–Planck model in generalized and restricted forms to describe the collisional consequences of this sort of interaction. Particular emphasis is placed on the peculiar details of the Coulomb collision theory overlooked in earlier works on this matter as: (a) the form of the collision term, (b) the definition of the Coulomb logarithm and (c) the value of the effective cross section. Only the long range effects are focused. To combine close and long ranges into a unique collision term the cross section corresponding to each range must be added. The classical use of the same expression for the cross section in both ranges is shown to be inappropriate. The proposed approach is valid regardless the form of the distribution function, on the magnitude of the flow velocity, besides being applicable to other types of interparticle forces as Maxwell molecule interactions. The material is relevant for solar plasma, interplanetary transport and planetary magnetosphere studies.

Weather disturbances in the low latitude ionosphere and their low altitude modeling

Abstract Though the climatology of the system is basically understood the modeling of the low altitude region of the low latitude ionosphere still challenges our ability to handle this matter. The underlying causes of weather phenomena (sporadic E layers, intermediate layers, and equatorial electrojet) can be traced to the propagation of tides and gravity waves from the lower atmosphere. Thus, it is time to investigate the possibility for specifying conditions and eventually forecast models for predicting the occurrence, duration and intensity of these phenomena. This work provides a brief and formal discussion on the low-altitude space weather issues related with the low latitude ionosphere, as well as the problems associated with conforming the necessary conditions for their occurrence with the standard systematics for empirical modeling. In particular it is shown that the composition, morphology and dynamics are well determined though the driving mechanisms and chemistry of irregular layers remains as intriguing as ever.

On the influence of the stress tensor and heat flow vector in collisional multispecies fluids

Abstract The effective influence of the stress tensor and heat flow vector in collisional multispecies fluids is quite a controversial matter. Suggested by phenomenological laws these parameters are usually evaluated with the simple Newton and Fourier relations. The kinetic theory attributed them to the motion and interactions of particles. The validity of the Navier–Stokes set of equations with Newtons-law of stresses and Fouriers law of heat flow has been contested in many cases based on simple traditional models of the collision frequency. Thanks to many recent advances on the evaluation of the Boltzmann collision term, now one can make a more reliable analysis as to proper account for the effect of these parameters. To accomplish this task in this work, the essential aspects of the matter are revised with improved accuracy. It is shown, in particular, that the theory can present now reasonable grounds to properly set appropriate boundaries on the validity of the currently used expressions for modelling stresses and heat flow. The theoretical results presented here are applicable to a wide range of gas and plasma conditions covering the needs from rarefied to dense fluids and also low- (subsonic) and high-speed (supersonic) flows. Thus, they can be used for problems of physics of fluids, geophysics, solar and interplanetary physics.