Multipoint Observations of Solar Type III Radio Bursts from STEREO and Wind

The twin STEREO and the Wind spacecraft make remote multipoint measurements of interplanetary radio sources of solar origin from widely separated vantage points. One year after launch, the angular separation between the STEREO spacecraft reached 45°, which was ideal for locating solar type III radio sources in the heliosphere by three-spacecraft triangulation measurements from STEREO and Wind. These triangulated source locations enable intrinsic properties of the radio source, such as its beaming characteristics, to be deduced. We present the first three-point measurements of the beaming characteristics for two solar type III radio bursts that were simultaneously observed by the three spacecraft in December of 2007 and in January of 2008. These analyses suggest that individual type III bursts exhibit a wide beaming pattern that is approximately beamed along the direction tangent to the Parker spiral magnetic field line at the source location.     

An instrument for the quantitative separation and size-classification of air-borne particulate matter down to 0.2 micron

Summary The theory and experimental design of an instrument for the quantitative separation and size-classification of air-borne particulate matter down to diameter of 2.10^–5 cm and its performance characteristics are described.The basic operating principle of the instrument consists of exerting a high centrifugal acceleration (ca. 20000 g) on a continuosLaminar flow of the aerosol, so that the trajectories of the air-borne particles (nuclei) in the flow follow Stokes'law, and the locus of their deposition becomes predictable.This principle is realized by a rotor, driven electrically at ca. 400 Hertz, which carries a helical channel the peripheral wall of which forms the removable envelope of a cone—and thus the place of particle deposition. The movement of the air relative to the channel is caused by the impeller-action (viscous drag) of the rotating helix. The relative flow velocity is kept in the laminar range (Reynold's number 800) by control of the flow resistance of the channel.The so resulting particle deposit is arranged in accordance with the equivalent to the «Stokes diameters», hence counts and chemical analyses of individual sizeclasses are possible, solely with reference to the locus of deposition on the channel wall. Examples taken from city air and automobile exhausts are briefly discussed.     

Acoustically estimated size distribution of sperm whales (Physeter macrocephalus) off the east coast of New Zealand

ABSTRACT

The length-frequency distribution of sperm whales (Physeter macrocephalus) was studied on the east coast of NZ using passive acoustic recorders moored offshore of Kaikoura, Cape Palliser and Castlepoint. Sperm whale’s echolocation signals are unique among odontocete species. Their clicks are composed by multiple pulses resulting from the sound transmission within the whale head. The total length of the whales can be estimated by measuring the time delay between these pulses. A total of 997 length measurements were obtained from click trains using cepstral analysis (mean?=?14.6?m; min?=?9.6?m; max?=?18.3?m; std?=?1?m). The size-frequency distributions at all three locations were similar, although animals smaller than 12?m were not present offshore of Kaikoura. Animals of various sizes appeared to be present all year round, with no apparent seasonality in the occurrence of any size class.     

Could surface roughness be a poor proxy for landslide age? Results from the Swabian Alb,Germany

The potential of surface roughness to quantify geomorphological landforms and processes has been enhanced with the availability of high‐resolution digital terrain models (DTM). Recent studies that attempt to identify landslide features with surface roughness have suggested that this measure of topographic heterogeneity may also be applied to estimate the relative age of landslides. This is a provisional study that explores the potential of this relationship by assessing the ability of surface roughness to act as a proxy for relative landslide age. The surface roughness for a set of 12 dated landslides in the Swabian Alb that occurred between 1789 and 1985 was calculated from a 1 m² spatial resolution LiDAR DTM with three algorithms: root‐mean‐square‐height (RMSH), standard deviation of slope (SDS), and direction cosine eigenvalue ratios (DCE). Scale‐dependence was analysed by calculating surface roughness for a range of moving window sizes (3 × 3, 5 × 5, 9 × 9 and 15 × 15), and surface roughness for each landslide was summarized by the median and upper quartile. Only weak correlations (best Spearman's rho 0.58) were present between landslide age and surface roughness. This correlation becomes weaker with increasing moving window size. Given weak observed associations and discussed challenges pertaining to the complexities of landslide morphology change over time, we currently find that surface roughness alone may not be justifiable to act as a proxy for landslide age for our study region. Furthermore, we recommend future studies should focus on addressing possible natural and anthropogenic factors such as land use change that may alter surface roughness. These studies may focus on one of the three roughness measures used here as they are strongly correlated. Copyright © 2014 John Wiley & Sons, Ltd.     

WIND observations of coherent electrostatic waves in the solar wind

The time domain sampler (TDS) experiment on WIND measures electric and magnetic wave forms with a sampling rate which reaches 120 000 points per second. We analyse here observations made in the solar wind near the Lagrange point L1. In the range of frequencies above the proton plasma frequency f_pi and smaller than or of the order of the electron plasma frequency f_pe, TDS observed three kinds of electrostatic (e.s.) waves: coherent wave packets of Langmuir waves with frequencies f ≃ f_pe, coherent wave packets with frequencies in the ion acoustic range f_pi ≥ f ≥ f_pe, and more or less isolated non-sinusoidal spikes lasting less than 1 ms. We confirm that the observed frequency of the low frequency (LF) ion acoustic wave packets is dominated by the Doppler effect: the wavelengths are short, 10 to 50 electron Debye lengths λ_D. The electric field in the isolated electrostatic structures (IES) and in the LF wave packets is more or less aligned with the solar wind magnetic field. Across the IES, which have a spatial width of the order of ≃25_D, there is a small but finite electric potential drop, implying an average electric field generally directed away from the Sun. The IES wave forms, which have not been previously reported in the solar wind, are similar, although with a smaller amplitude, to the weak double layers observed in the auroral regions, and to the electrostatic solitary waves observed in other regions in the magnetosphere. We have also studied the solar wind conditions which favour the occurrence of the three kinds of waves: all these e.s. waves are observed more or less continuously in the whole solar wind (except in the densest regions where a parasite prevents the TDS observations). The type (wave packet or IES) of the observed LF waves is mainly determined by the proton temperature and by the direction of the magnetic field, which themselves depend on the latitude of WIND with respect to the heliospheric current sheet.     

Towards generating highly detailed 3D CityGML models from OpenStreetMap

About one decade has passed since US vice president Al Gore articulated his vision of Digital Earth (DE). Within this decade, a global multi-resolution and three-dimensional (3D) representation of the Earth, which sums up the DE vision, increasingly gained interest in both public and science. Due to the desired high resolution of the available data, highly detailed 3D city models comprise a huge part of DE and they are becoming an essential and useful tool for a range of different applications. In the past as well as at present, 3D models normally come from a range of different sources generated by professionals, such as laser scans or photogrammetry combined with 2D cadaster data. Some models are generated with semi-automated or fully automated approaches, but in most cases manual fine tuning or even manual construction from architectural plans is required. Further beyond outdoor city models, DE additionally envisages the provision of indoor information. That is, the interior structure of public or publically accessible buildings, such as airports or shopping malls, is represented and made available in 3D; however, at the moment, such models are mostly created by hand and essentially based on professional data sources. In contrast to such professional data, which is mainly captured by surveyors or companies, the last few years revealed the phenomenon of crowdsourced geodata, which receives an increasing attractiveness as an alternative data source for many Geographic Information Systems (GIS). Former research already demonstrated the power and richness of such geodata – especially OpenStreetMap (OSM) – and it has also been proved that this non-standardized, crowdsourced geodata can be combined with international standards of the Open Geospatial Consortium (OGC). For example, CityGML Level-of-Detail 1 (LoD1) and LoD2 models have already been created automatically from OSM. The research presented in this article will further continue on the automated generation of CityGML models from OpenStreetMap. Essentially, a method for the creation of highly detailed CityGML LoD4 models with interior structures will be explained. By applying the invented approach on existing OSM data, limitations and restrictions of the IndoorOSM mapping proposal, the available data and the developed approach are revealed and discussed.     

Groundwater recharge in a confined paleovalley setting,Northeast British Columbia,Canada

Hydrogeology Journal - Ancient river channels or subglacial drainage networks infilled with younger sediments can include significant deposits of highly permeable sands and gravels. Despite being...     

A simultaneous X-ray and optical study of TT Arietis

Prelimary results of an extended program of coordinated X-ray and optical observations of TT Ari are presented. The object was observed on August 21/22 1985 both in X-rays (EXOSAT) and optical range, about 100 days after the return to the active state. The first detailed simultaneous study of TT Ari in active state indicates the presence of strongly absorbing structure in the system.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

Response of Nebraska Sand Hills Natural Vegetation to Drought, Fire, Grazing, and Plant Functional Type Shifts as Simulated by the Century Model

The Nebraska Sand Hills exist in a semi-arid climatic environment and the land surface is grassland growing on sandy soils. These soils have been periodically active throughout the Holocene, but are currently stabilized by the vegetation. However, a shift in climate could cause grassland death and eventual sand dune remobilization. Our studies used the CENTURY nutrient cycling and ecosystem model to investigate the impacts of drought, plant functional type, fire, grazing, and erosion on Nebraska Sand Hills vegetation and dune stability. Fire and grazing alone had little impact on the vegetation, but when combined with mild drought, biomass decreased. Overall biomass increased if one plant functional type was allowed to dominate the ecosystem. Addition of as little as 1 mm of erosion per year under current climate conditions decreases vegetation as much as a drought 20 percent drier than the worst of the 1930s drought years in Nebraska.