Electric field sources in the quiet plasmasphere from whistler observations

Existing evidence for the ionospheric dynamo being the source of quiet time electric fields in the plasmasphere is reviewed. Part of a 24 h set of whistler data recorded continuously at Sanae, Antarctica (L = 4), during quiet magnetic (average K_p = 1) is analysed to obtain westward electric fields in the equatorial plane. These electric fields are examined as a function of L-value in order to infer their source. It is found that for periods of outward flow of plasma during the noon-midnight local time period, the electric fields are consistent with the dominant source being the ionospheric dynamo. There is some evidence that during the evening period of inward flow the electric fields are magnetospheric in origin, although this could also be consistent with a refined dynamo model. The observed whistler duct convection patterns do not fit either of two theoretical models, which invoke a magnetospheric field but not a dynamo field.     

Parametric excitation of whistler waves by HF heater

Possible generation of whistler waves by Tromso HF heater is investigated. It is shown that the HF heater wave can parametrically decay into a whistler wave and a Langmuir wave. Since whistler waves may have a broad range of frequency, the simultaneously excited Langmuir waves can have a much broader frequency bandwidth than those excited by the parametric decay instability.     

On the influence of a plasma hot component on whistler propagation beyond the plasmapause

Theoretical spectrograms are computed for whistlers propagating beyond the plasmapause. The electron distribution function was modelled as consisting of a hot plus a cold component and an appropriate dispersion equation is used. A collisionless (CL) model is used for the cold electron concentration and for the hot electron component the derived model assumes a bi-maxwellian distribution function with a loss cone at the equator. The results indicate limits on the use of the cold plasma approximation (c.p.a.) in the study of magnetospheric whistler propagation beyond the plasmapause and show that whistler analysis with the c.p.a. may under or overestimate the L value of the path deduced from ground spectrograms, depending on the anisotropy of the hot component.     

Investigation by ray-tracing of the effect of a summer-winter asymmetry on whistler ducting

A ray-tracing model of the inner magnetosphere (L < 6) is constructed for a plasma distribution asymmetric about the equatorial plane, thus representing summer and winter conditions in the two hemispheres. At the reference height of 900 km, the oxygen ion concentration and electron density are taken to vary by factors of ten and two respectively between the hemispheres. The concentrations of hydrogen and helium ions at the reference level are chosen to ensure electron density continuity across the equatorial plane. The altitude at which ducts terminate is modelled to differ between the two hemispheres in accordance with the numerical simulations of Bernhardt and Park (1977).It is shown that the different plasma distributions in the two hemispheres affect the paths of ducted rays and consequently the likelihood of the reception of one-hop whistlers in the conjugate hemisphere. The difference in final latitude between propagation in the symmetric and asymmetric models for the same initial latitude is largest when ducts extend down to 300 km altitude in the conjugate hemisphere. When ducts terminate at greater altitude, the effect of a difference in termination heights between the two hemispheres generally has a larger effect than that of the plasma asymmetry. Both these effects may play a role in determining the seasonal variation of whistler occurrence.     

The effect of the mid-latitude ionospheric trough on whistler mode ducting during magnetic storms

Whistler-mode signals observed at Faraday, Antarctica (65° S, 64° W, Λ=50.8°) show anomalous changes in group delay and Doppler shift with time during the main phase of intense geomagnetic activity. These changes are interpreted as the effect of refracting signals into and out of ducts near L=2.5 by electron concentration gradients associated with edges of the mid-latitude ionospheric trough. The refraction region is observed to propagate equatorwards at velocities in the range 20–85 ms⁻¹ during periods of high geomagnetic activity (K_p ≥ 5), which is in good agreement with typical trough velocities. Model estimates of the time that the trough edges come into view from Faraday show a good correlation with the observed start times of the anomalous features. Whistler-mode signals observed at Dunedin, New Zealand (46° S, 171° E, Λ=52.5°) that have propagated at an average L-shell of 2.2 (Λ=47.6°) do not show such trough-related changes in group delay. These observations are consistent with a lower occurrence of the trough at lower invariant latitudes.     

The effects of ionospheric horizontal electron density gradients on whistler mode signals

Whistler mode group delays observed at Faraday, Antarctica (65° S, 64° W) and Dunedin, New Zealand (46° S, 171° E) show sudden increases of the order of hundreds of milliseconds within 15 minutes. These events (‘discontinuities’) are observed during sunrise or sunset at the duct entry regions, close to the receiver's conjugate point. The sudden increase in group delay can be explained as a tilting of the up-going wave towards the sun by horizontal electron density gradients associated with the passage of the dawn/dusk terminator. The waves become trapped into higher L-shell ducts. The majority of the events are seen during June-August and can be understood in terms of the orientation of the terminator with respect to the field aligned ducts. The position of the source VLF transmitter relative to the duct entry region is found to be important in determining the contribution of ionospheric electron density gradients to the L-shell distribution of the whistler mode signals.     

Computation of whistler wave normals using a combined matched filtering and parameter estimation technique

A new method is presented for computing the wave normal directions of deterministic VLF signals that can be approximated by plane waves. The a priori information about the frequency-time behaviour of the signal is exploited by a matched filtering and subsequent parameter estimation technique. The method was developed basically to determine wave normal directions of whistlers from wave field components measured on-board. After an outline of the method, results obtained for simulated whistlers are presented that demonstrate the superiority of the new method over the cross-product and Means methods.     

The influence of ionospheric absorption on mid-latitude whistler mode signal occurrence from VLF transmitters

Whistler mode signals from VLF transmitters received at Faraday, Antarctica (65° S, 64° W) during 1986–1991 show an annual variation in the number of hours over which signals are observed, with a maximum in June and a minimum in December. The variation was larger at solar minimum than at maximum and can be understood in terms of changes in absorption of VLF signals in the D-region, where the high geographic latitude of Faraday plays an important role in producing low attenuation levels during the austral winter. In contrast, very little such variation was observed at Dunedin, New Zealand (46° S, 171° E) in 1991. Nighttime whistler mode signals have start and end time trends that are consistent with the influence of F-region absorption. Increases in whistler mode occurrence appear to be associated with periods of high geomagnetic activity at solar maximum but not during solar minimum. A possible mechanism involving decreased F-region absorption is discussed.     

Analytic ethics in the central period

Analytic ethics in the central period – extending from the beginning of the twentieth century to post-World War II linguistic analysis – is too often construed by historians and philosophers alike in monolithic terms as the emotivism of A. J. Ayer. In contrast, we argue that a multiplicity of ethical doctrines were developed by analytic philosophers at this time of which Ayer's emotivism was just one. Moreover, we maintain that this multiplicity of ethical doctrines was itself the result of a multiplicity of conceptions of analysis and that connecting these two sets of beliefs makes for the best understanding of analytic ethics.     

Numerical simulation of the penetration and reflection of a whistler beam incident on the lower ionosphere at very low latitude

By the full-wave algorithm with Fourier synthesis, 3-D propagation of a whistler beam incident on the pre-dawn lower ionosphere at very low latitude is numerically investigated. Processes of transmission, reflection, and coupling with the Earth-ionosphere waveguide are discussed via the wave energy and polarisation distributions and their dependence on the wave parameters and the ionospheric profile (such as the E_s-layer). It is shown that the dominant wave above 90 km altitude has the propagation characteristics of the magneto-ionic whistler mode, and absorption, spreading, reflection and mode conversion mainly occur at, and are greatly affected by, the bottom of the ionosphere. It is found that the transmitted energy density along the Earth's surface is reduced by 20 dB or more. Beam transmission loss varies asymmetrically with the incident angle, but changes little with the frequency. In the region 150 km (for 5 kHz) away from the ‘exit area’ where whistlers emerge, the bearing measurements using ground-based VLF direction-finders may be in error because direction-finding algorithms assume plane wave propagation. Only a small portion (about −25 dB at 5 kHz) of the incident energy is reflected up to an altitude of 150 km, and major reflection takes place in a small range of altitude at the bottom of the ionosphere with little spreading and lateral shift with respect to the incident beam. Reflection is enhanced considerably at lower frequency. Our results also suggest that an E_s-layer or an ionospheric gradient refracting waves to higher latitudes would be favorable factors for multi-hop echoes to be received on the ground.     

新制度经济学的分析方法评述

新制度经济学是目前经济学领域最前沿的研究方向之一，日渐受到社会各界尤其是经济学界的密切关注，本详细论述了新制度经济学的产生、分析方法、与制度学派的区别、新制度经济学的贡献与局限以及新制度经济学的最新发展。     

The Implications of Analytic Philosophy of History for the Practicing Historian

An article by John O'Hagan and Elish Kelly in 2005 (see Historical Methods 38:118-25) discussed collecting information on visual artists that would allow a broad historical ranking based on "prominence." O'Hagan and Kelly collected these data to examine prominent artists' birth locations, work locations, and their consequential patterns of labor movement during several long periods. In this article, the authors examine artists' migration for four periods (based on their date of birth): Renaissance Italy, Europe in the first half of the nineteenth century, and the Western world in general for the periods 1850-99 and 1900-49. The data show that important artists clustered in all periods at a remarkably high level. Florence and Rome dominated in Renaissance Italy, with significant clustering because of the artists' birthplaces and domestic migration. Paris and London witnessed a marked clustering of artists born in the first half of the nineteenth century, with Paris continuing to dominate among artists born in the second half of the nineteenth century. Artists born in the first half of the twentieth century clustered in New York City, with all prominent American artists clustering there.     

20世纪西方分析或批判的历史哲学

分析或批判的历史哲学的兴起,一方面批判了思辨的历史哲学,另一方面将历史哲学研究的重点从解释历史的性质转移到解释历史知识的性质上来。这极大地推进了史学理论的发展,也为历史学确立了更为稳固的根基。德国历史哲学家狄尔泰、文德尔班、李凯尔特继承德国历史主义传统,从文化科学与自然科学相异的角度来分析历史知识的性质;克罗齐、柯林武德也遵循了这个传统。分析学派罗素、波普尔、亨佩尔等人,则从语言逻辑的角度来分析理解历史的方式和历史知识的可能性。这两个方向共同构成了20世纪西方历史哲学的主流,进一步深化了人们对自我的认识。     

A test of the Hines dispersion equation for atmospheric gravity waves

Simultaneous observations of an ionospheric wave by two incoherent scatter facilities and three Faraday-rotation polarimeters have provided measurements of the frequency, vertical wavelength, horizontal wavelength and direction of propagation of the wave. These measured values confirm the Hines dispersion equation for atmospheric gravity waves.     

Horizontal velocity dispersion of medium-scale travelling ionospheric disturbances in the F-region

Daytime observations of the horizontal velocity dispersion of medium-scale travelling ionospheric disturbances (TID) near the F2 peak height have been carried out using an array of HF Doppler sounders in central Japan. Cross-correlation analysis of sample records has shown that the horizontal trace velocity is a decreasing function of the period of fluctuations in the range 13.3–40 min. The theoretical dispersion of the atmospheric gravity waves is also calculated using Klostermeyer's (1974) method. Comparison between the observed and the calculated results suggests the possibility that the components of the lower period of the observed velocity dispersion may be a remnant of the quasi-evanescent mode pertinent to lower-height levels.     

A spatial interaction model of vote dispersion

How do votes disperse through a territory? Studies of spatial voting patterns have largely focused on the influence of local factors on voting. The “Friends and Neighbors” model (Key (1949)) explains the advantage of candidates running for office in the locality with which they are associated (Arzheimer and Evans (2012, 2014): Collignon and Sajuria (2018); Horiuchi et al. (2018); Jankowski (2016); Hunt (2020); Munis (2021)), and the “neighbor” effect helps to explain why votes spread. More recent studies have found that the dispersion of votes decreases with distance (Put et al. (2020); Arzheimer and Evans (2012)). However, we know little about how spatial patterns of voting emerge or the mechanism behind the neighbor effect. We argue that this effect depends on the neighbors’ access to information about a candidate, which is constrained by the way information flows. Although scholars have argued that information is a relevant driver explaining the dispersion of votes (Bowler et al. (1993); Arzheimer and Evans (2012); Evans et al. (2017); Campbell, Cowley, Vivyan, and Wagner (2019)), no research has examined the relevance of the network through which information flows. We propose that a spatial interaction model (Wilson (1971)) allows us to predict where this information flows or the voting pattern that will form. Taking advantage of a quasi-natural experiment in Brazilian legislative elections in 1974 and 1978, we show that votes spread through areas of influence created by a hierarchy of cities based on the flows of exchanges among them, including information. We then use our spatial interaction model to predict voting patterns in the elections of 1978 using data from the 1974 elections. Our findings show that the spatial interaction model results fit the data quite well and can help predict spatial patterns of voting.     

一批中国古代镶嵌玻璃珠化学成分的检测报告

结合外束质子激发X荧光（proton induced X-ray emission,PIXE）和能量色散X射线荧光（energy dispersive X-ray emission,EDXRF）分析技术,对中国新疆、湖北、四川、广东出土的古代镶嵌玻璃珠的化学成分进行了检测.结果表明：新疆拜城克孜尔墓地出土的西周-春秋时期镶嵌玻璃珠为CaO-MgO-SiO2玻璃,战国时期中国境内的PbO-BaO-SiO2和Na2O-CaO-SiO2镶嵌玻璃珠是同时存在的.本文亦对相关问题进行了一些讨论,并提出了部分今后的工作建议.     

Effects of land and sea parameters on the dispersion of tweek atmospherics

The appearance of tweeks on whistler sonograms has been discussed in terms of VLF wave propagation through the land-sea and ionospheric waveguide. It is shown that the conductivity of ground and sea mixed path, forming the lower surface of the waveguide, may provide an estimate of the source distance of whistlers generating atmospherics.