Thermal and suprathermal plasma densities in the outer magnetosphere

Using the low-frequency cutoff of electromagnetic noise trapped in the magnetosphere at frequencies above the local plasma frequency, it is now possible to make very accurate, + or - 1%, electron density measurements in the low density region between the magnetopause and plasmapause. This technique for measuring the total plasma density was used, together with measurements of the suprathermal proton intensities with the LEPEDEA instrumentation on the IMP-6 spacecraft, to determine the thermal proton densities in the region between the plasmapause and magnetopause. Although the thermal protons usually account for a significant fraction, approximately 50%, of the total proton density in this region, in some cases, particularly at the larger radial distances the density of the thermal protons sometimes drops to a very small fraction, 5%, of the total density and nearly all of the plasma consists of suprathermal particles

Fronts and frontogenesis as revealed by high time resolution data

Upper air sounding are used to examine a cold front of average intensity. Vertical cross sections of potential temperature and wind, and horizontal analyses were compared and adjusted for consistency. These analyses were then used to study the evolution of the front, found to consist of a complex system of fronts occurring at all levels of the troposphere. Low level fronts were strongest at the surface and rapidly weakened with height. Fronts in the midddle troposphere were much more intense. The warm air ahead of the fronts was nearly barotropic, while the cold air behind was baroclinic through deep layers. A deep mixed layer was observed to grow in this cold air

Observed relationships between electric fields and auroral particle precipitation

Simultaneous electric field and plasma observations with the low altitude, polar orbiting satellite Injun (Hawkeye) 5 provided a comprehensive survey of convection electric fields and their association with magnetospheric plasma phenomena. The most prominent features of the convection electric fields are reversals located at high magnetic latitudes, with generally anti sunward convection poleward convection equatorward of the electric field reversal location. The electric field reversal is interpreted as the boundary between open and closed magnetic field lines. To investigate the electric field and plasma interrelationships during a polar magnetic substorm, a series of passes obtained prior to and during a substrom is presented. Large, anti sunward convection velocities were detected over the polar cap several tens of minutes before the onset of the expansive phase of the substrom. These convection velocities gradually decreased during the decay phase of the substrom. Measurements of enhanced anti sunward flow over the polar cap region are generally consistent with concepts of the origin of substroms

On the distributions of plasmas and electric fields over the auroral zones and polar caps

Plasma and electric field distribution over auroral zones and polar cap

ELF noise bands associated with auroral arcs

ELF noise band associated with low-energy electron precipitation events and auroral arcs based on Explorer 40 observation

Electron plasma oscillations associated with type 3 radio emissions and solar electrons

An extensive study of the IMP-6 and IMP-8 plasma and radio wave data was performed to try to find electron plasma oscillations associated with type III radio noise bursts and low-energy solar electrons. It is shown that electron plasma oscillations are seldom observed in association with solar electron events and type III radio bursts at 1.0 AU. For the one case in which electron plasma oscillations are definitely produced by the electrons ejected by the solar flare the electric field strength is relatively small. Electromagnetic radiation, believed to be similar to the type III radio emission, is observed coming from the region of the more intense electron plasma oscillations upstream. Quantitative calculations of the rate of conversion of the plasma oscillation energy to electromagnetic radiation are presented for plasma oscillations excited by both solar electrons and electrons from the bow shock. These calculations show that neither the type III radio emissions nor the radiation from upstream of the bow shock can be adequately explained by a current theory for the coupling of electron plasma oscillations to electromagnetic radiation

Segmentation ART: A Neural Network for Word Recognition from Continuous Speech

The Segmentation ATIT (Adaptive Resonance Theory) network for word recognition from a continuous speech stream is introduced. An input sequeuce represents phonemes detected at a preproccesing stage. Segmentation ATIT is trained rapidly, and uses a fast-learning fuzzy ART modules, top-down expectation, and a spatial representation of temporal order. The network performs on-line identification of word boundaries, correcting an initial hypothesis if subsequent phonemes are incompatible with a previous partition. Simulations show that the system's segmentation perfonnance is comparable to that of TRACE, and the ability to segment a number of difficult phrases is also demonstrated.National Science Foundation (NSF-IRI-94-01659); Office of Naval Research (N00014-95-1-0409, N00014-95-1-0G57

Electron angular distributions above the dayside auroral oval

An electrostatic analyzer was employed on the Ariel 4 satellite to determine pitch angle distributions of electron intensities over the dayside auroral oval. Two major precipitation zones were encountered: an equatorward zone of broad spectra with intensities of approximately 1000 electrons/(sq cm-sec-sr-eV) and a poleward zone, the polar cusp, with intensities typical of those of the magnetosheath. Angular distributions within the equatorward zone are generally isotropic outside of the atmospheric backscatter cone. The precipitation mechanism appears to be pitch angle scattering near the distant magnetic equator. In contrast, pitch angle distributions within the polar cusp are often found to be strongly field aligned with intensities within the atmospheric loss cone greater by factors of approximately 10 than the mirroring intensities. These distributions are qualititatively similar to those for the inverted V precipitation events at later local times, and probably share a common acceleration mechanism with the inverted V phenomenon

How Do Firms Exercise Unilateral Market Power? Evidence from a Bid-Based Wholesale Electricity Market

This paper uses the framework in Wolak (2003a,b and 2007) and data on half-hourly offer curves and market-clearing prices and quantities from the New Zealand wholesale electricity market over the period January 1, 2001 to June 30, 2007 to characterize how the four large suppliers in this imperfectly competitive industry exercise market power. To accomplish this we introduce half-hourly measures of the firm-level ability and incentive of an individual supplier to exercise unilateral market power that are derived from a simplified model of expected profit-maximizing offer behaviour in a multi-unit auction market. We then show that half-hourly market-clearing prices are highly correlated with the half-hourly values of the firm-level and firm-average measures of both the ability and incentive of the four large suppliers in New Zealand to exercise market power. We then present evidence consistent with the view that this increasing relationship between the ability or incentive of individual suppliers to exercise market power and higher market-clearing prices is caused by the four large suppliers submitting higher offer prices when they have a greater ability or incentive to exercise unilateral market power. We show that after controlling for changes in input fossil fuel prices and other factors that impact the opportunity cost of producing electricity during that half hour, each of the four suppliers submits a higher offer price into the wholesale market when it has a greater ability or incentive to exercise unilateral market power. To strengthen the case that this increasing relationship between market prices and the ability and incentive of each of the suppliers to exercise unilateral market power is actually caused by the four large suppliers exercising unilateral market power by changing their offer prices in response to their ability and incentive to exercise market power, we also perform a test of the implications of the null hypothesis that the four large suppliers behave as if they had no ability to exercise market power. We find strong evidence against this null hypothesis and instead find that these hypothesis testing results are consistent with the perspective that these suppliers are exercising all available unilateral market power.Classification-JEL:Unilateral Market power analysis,New Zealand,Electricity Market,multi-unit auction

Large temporal variations of energetic electron intensities at mid-latitudes in the outer radiation zone Progress report

Variations of electron flux density observations by Explorer 12 and 1