Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science最新文献_第2页

Formation of electrostatic potential drops in the auroral zone 在极光区静电电位下降的形成

Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science Pub Date : 2001-01-01 DOI: 10.1016/S1464-1917(00)00092-1

D. Schriver , M. Ashour-Abdalla , R.L. Richard

{"title":"Formation of electrostatic potential drops in the auroral zone","authors":"D. Schriver , M. Ashour-Abdalla , R.L. Richard","doi":"10.1016/S1464-1917(00)00092-1","DOIUrl":"https://doi.org/10.1016/S1464-1917(00)00092-1","url":null,"abstract":"<div>In order to examine the self-consistent formation of large-scale quasi-static parallel electric fields in the auroral zone on a micro/meso scale, a particle in cell simulation has been developed. The code resolves electron Debye length scales so that electron micro-processes are included and a variable grid scheme is used such that the overall length scale of the simulation is of the order of an Earth radii along the magnetic field. The simulation is electrostatic and includes the magnetic mirror force, as well as two types of plasmas, a cold dense ionospheric plasma and a warm tenuous magnetospheric plasma. In order to study the formation of parallel electric fields in the auroral zone, different magnetospheric ion and electron inflow boundary conditions are used to drive the system. It has been found that for conditions in the primary (upward) current region an upward directed quasi-static electric field can form across the system due to magnetic mirroring of the magnetospheric ions and electrons at different altitudes. For conditions in the return (downward) current region it is shown that a quasi-static parallel electric field in the opposite sense of that in the primary current region is formed, i.e., the parallel electric field is directed earthward. The conditions for how these different electric fields can be formed are discussed using satellite observations and numerical simulations.</div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 1","pages":"Pages 65-70"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(00)00092-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91669909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

Effects of gravity and planetary waves on the lower ionosphere as obtained from radio wave absorption measurements 从无线电波吸收测量得到的重力波和行星波对电离层下层的影响

Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science Pub Date : 2001-01-01 DOI: 10.1016/S1464-1917(01)00018-6

J. Laštovička

{"title":"Effects of gravity and planetary waves on the lower ionosphere as obtained from radio wave absorption measurements","authors":"J. Laštovička","doi":"10.1016/S1464-1917(01)00018-6","DOIUrl":"10.1016/S1464-1917(01)00018-6","url":null,"abstract":"<div>This paper is an overview of effects of gravity and planetary waves on the lower ionosphere as obtained from radio wave absorption measurements. To transform gravity waves from the neutral atmosphere into the ionized component is not easy. The uncertainty caused by problems with transfer of oscillations from neutral to ionized component makes the use of daytime absorption measurements for gravity wave investigations largely impossible and allows us to use only nighttime radio wave absorption. Some results of gravity wave activity studies in the lower ionosphere, based on 5.5 year long data set, are presented: (i) The gravity wave activity is almost insensitive to QBO. (ii) It decreases from the solar cycle maximum to the solar cycle minimum by ∼30%. (iii) The Mt. Pinatubo volcanic effect is well expressed for longer periods ( > 2 hours) but not detectable at short periods (< 1 hour). (iv) There is no detectable seasonal variation at high solar activity but there is a tendency to summer maximum at medium solar activity. The planetary waves are transformed from the neutral to the ionized component adequately as for the period. It was proved that planetary wave type oscillations in the lower ionosphere are caused by the neutral atmosphere oscillations, not by solar or geomagnetic activity. Various features of planetary wave activity, inferred from ionospheric measurements, have been studied. Perhaps the most interesting results are those on long-term trends. A general increase of planetary wave activity has been observed in the 1970s and 1980s, while the level of planetary wave activity has been stable in the 1960s and 1990s.</div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 6","pages":"Pages 381-386"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(01)00018-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79646489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 18

Preliminary results on the within-the-hour ionospheric variability 电离层小时内变率的初步结果

Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science Pub Date : 2001-01-01 DOI: 10.1016/S1464-1917(01)00005-8

D.N. Fotiadis , S.S. Kouris , B. Zolesi

引用次数: 4

Particle acceleration linked to Alfvén wave propagation on small scale density gradients 粒子加速与小尺度密度梯度上的alfvsamn波传播有关

Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science Pub Date : 2001-01-01 DOI: 10.1016/S1464-1917(00)00111-2

V. Génot , F. Mottez , P. Louarn

引用次数: 14

Experimental study on the entrainment of bed material into debris flow 泥石流中床质夹带的实验研究

Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science Pub Date : 2001-01-01 DOI: 10.1016/S1464-1917(01)00062-9

S. Egashira , N. Honda , T. Itoh

{"title":"Experimental study on the entrainment of bed material into debris flow","authors":"S. Egashira , N. Honda , T. Itoh","doi":"10.1016/S1464-1917(01)00062-9","DOIUrl":"10.1016/S1464-1917(01)00062-9","url":null,"abstract":"<div>The present study describes entraining characteristics of bed material into debris flow, based on flume tests, numerical and dimensional analyses. Flume tests are conducted to investigate influences of bed sediment size on erosion rate by supplying debris flows having unsaturated sediment concentration onto erodible beds. Experimental results show that the relative erosion rate, E/E0, decreases monotonically with increase of relative sediment size, d/d0, although E/E0 changes slightly with sediment concentration of debris flow. Herein, E is the erosion rate of bed sediment of size, d, E0 is the erosion rate when solid particle size, d0, of debris flow, are the same of the erodible bed material. According to the relation between E/E0 and d/d0, erosion rate, E, can be estimated by using Egashira's formula for E0. Therefore, the validity of erosion rate formula for E0 is tested by solving numerically for debris flow characteristics in terms of governing equations. In addition, critical size of bed sediment entrainment is discussed by introducing non-dimensional effective bed shear stress which is formulated by using fluid shear stress (total shear stress minus yield stress), bed sediment size, d, specific weight of sediment particle in water and acceleration due to gravity, and it is found that the critical non-dimensional effective shear stress takes a value similar to critical Shields parameter for bed load movement.</div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 9","pages":"Pages 645-650"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(01)00062-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90728929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 149

Rainfall intermittency and the sampling error of tipping-bucket rain gauges 降雨的间歇性与翻斗式雨量计的抽样误差

Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science Pub Date : 2001-01-01 DOI: 10.1016/S1464-1917(01)95018-4

A. Molini, P. La Barbera, L.G. Lanza, L. Stagi

{"title":"Rainfall intermittency and the sampling error of tipping-bucket rain gauges","authors":"A. Molini, P. La Barbera, L.G. Lanza, L. Stagi","doi":"10.1016/S1464-1917(01)95018-4","DOIUrl":"10.1016/S1464-1917(01)95018-4","url":null,"abstract":"<div>This work amplifies upon the influence of rainfall intermittency on pluviometric time series. Intermittency is here defined as the percentage of no-rain periods within a rainfall event, and can be interpreted as a sort of ‘stochastic intermittency’. When measuring an intermittent or, in general, ‘erratic’ signal, a relevant source of error is associated with the sampling procedure. By using numerical simulation of intermittent rainfall events, we focus on the deriving pattern of sampling errors within rainfall measurements obtained from any classic tipping-bucket rain gauge. The analysis, performed in both the time and frequency domain, reveals a strong inverse linear dependence between rainfall intermittency and the sampling errors, while a weak dependence on the autocorrelation of synthetic rainfall events is shown. The average absolute error is around 30% for the events analysed while the error at each sampling period peaks values higher than 100%. A direct influence of intermittency on the statistical characteristics of measured rainfall events is observed.</div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 10","pages":"Pages 737-742"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(01)95018-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89451300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 50

Experimental investigations and simulations of quasi-steady potential drops in plasmas 等离子体准稳定电位降的实验研究与模拟

Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science Pub Date : 2001-01-01 DOI: 10.1016/S1464-1917(00)00093-3

S. Torvén, M. Wendt

{"title":"Experimental investigations and simulations of quasi-steady potential drops in plasmas","authors":"S. Torvén, M. Wendt","doi":"10.1016/S1464-1917(00)00093-3","DOIUrl":"10.1016/S1464-1917(00)00093-3","url":null,"abstract":"<div>Magnetic-field-aligned potential drops in the auroral zone have recently been interpreted in terms of “quasi-steady” states which are evaluated for a fixed, given ion density profile. Here we present experimental studies of such states, observed when a voltage drop is suddenly applied to an inhomogeneous plasma column with a homogeneous, axial magnetic field. The quasi-steady potential drops have a spatial extension related to the gradient length of the initial ion density and the potential profile steepens slowly to a U-shaped double layer on the ion time scale. They exist only when the applied voltage drop does not exceed a critical value which depends on the maximum difference in ion density. Higher voltage drops concentrate in a cathode sheath. Results from PIC-simulations and from a theoretical model, based on steady electron motion, are also presented. They agree excellently for times up to about an ion plasma period (ωpi−1). The theoretical current-voltage characteristic, which is determined by electron reflection at a virtual cathode formed in the plasma, agrees with the experiments up to about one ωpi−1. However, already at about 4ωpi−1 the measured currents have dropped much below the theoretical values, and also the measured average potential profiles are inconsistent with steady acceleration of the electrons. The increased resistivity is associated with strong fluctuations.</div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 1","pages":"Pages 71-80"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(00)00093-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90812247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A national network for snow monitoring in Norway: Snow pillow verification using observations and models 挪威全国积雪监测网络:利用观测和模式验证雪枕

Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science Pub Date : 2001-01-01 DOI: 10.1016/S1464-1917(01)95016-0

H.K. Sorteberg, R.V. Engeset, H.C. Udnæs

{"title":"A national network for snow monitoring in Norway: Snow pillow verification using observations and models","authors":"H.K. Sorteberg, R.V. Engeset, H.C. Udnæs","doi":"10.1016/S1464-1917(01)95016-0","DOIUrl":"10.1016/S1464-1917(01)95016-0","url":null,"abstract":"<div>Snowmelt makes a substantial contribution to spring floods in Norway. The most severe floods, such as the flood in southeast Norway in 1995, are fed from extensive snowcovered high-mountain areas. However, monitoring of the temporal and spatial variability of snow on a real-time basis is particularly difficult due to the vast extent, remote location and high-frequency variability of snow. To monitor the temporal evolution of the snow mass and its water content during winter and spring, a network of 23 snow pressure pillows has been established in Norway, covering 58°N–71°N, 6°E–28°E, and 30–1400 m above sea level. Hourly data are supplied twice a day to government agencies.During the 1998/1999 winter and spring, extensive manual sampling was conducted on a monthly basis to verify the measurements obtained from the snow pillows. Furthermore, nearby meteorological data were used to simulate snow accumulation and ablation using a snow model. To investigate the performance of the snow pillow network, manual snow surveys (depth and density, liquid water, stratigraphy and grain size), snow models (SWE, snow runoff, LWC) and nearby air temperature and precipitation data were analysed. The results are important for snow pillow deployment and maintenance, as well as snowmodelling in terms of historical simulations and spatial-temporal variation in model performance and parameter settings. The results show that snow accumulation was well simulated using the model. Snowmelt was not so easy to simulate. The snow pillow performance was not as good as expected, and it was obvious that the snow pillows did not respond well during periods of repeated melting and refreezing. Discrepancies were also observed between snow pillow and manual observations during the melting period in spring, which may be attributable to difficulties during the snow survey sampling.</div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 10","pages":"Pages 723-729"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(01)95016-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74873046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 22

Debris flow magnitude in the Eastern Italian Alps: data collection and analysis 意大利东部阿尔卑斯地区泥石流震级:数据收集与分析

Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science Pub Date : 2001-01-01 DOI: 10.1016/S1464-1917(01)00064-2

V. D'Agostino , L. Marchi

引用次数: 49

Calibration of tipping bucket hyetographs 倾卸斗温度计校正

Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science Pub Date : 2001-01-01 DOI: 10.1016/S1464-1917(01)95017-2

H. Bergmann, H. Breinhälter, O. Hable, R. Krainer

{"title":"Calibration of tipping bucket hyetographs","authors":"H. Bergmann, H. Breinhälter, O. Hable, R. Krainer","doi":"10.1016/S1464-1917(01)95017-2","DOIUrl":"10.1016/S1464-1917(01)95017-2","url":null,"abstract":"<div>The Institute for Hydraulics and Hydrology of the Technical University Graz, Austria operates two hydrological observation nets - one in the area of Eastern Styria and the other one in the city of Graz. Precipitation, meteorological and runoff data are collected.Comparative measurements of the tipping bucket hyetographs have shown the deviation between the recorded and the real precipitation intensity. Aim of the presented project was to get calibration curves for all tested precipitation gauges.The following steps were necessary:a) Development of a micro processor controlled calibration system. The calibration instrument is able to record a series of measurements for determining calibration factors.b) Development of a control software for the calibration device, that is able to take over the menu control with a laptop and store the determined values in an MS Excel worksheet. These values are used for calculating correction values and to display them in an adequate graphical way.c) Development of a practicable application software for correction of the measured precipitation data.The determined correction factors permit to consider the source of failure (e.g. location, ageing and wear of the material) and make available improved hydrological data.</div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 10","pages":"Pages 731-736"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(01)95017-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73604377","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7