Magnetopause current as seen by Cluster

The four-spacecraft, magnetic field measurements on Cluster can be combined to produce an accurate determination of the electric current in the magnetopause boundary during stable magnetopause crossings. For events that are planar on the scale of the spacecraft configuration, the thickness of the current layer can be accurately estimated from its magnetic profile at each spacecraft and the corresponding boundary crossing times. The latter, give a determination of boundary motion relative to the Cluster array. We use the estimates of all these properties, for a range of spacecraft separation distances, to show, firstly, that the estimate of electric current density is representative even when the spatial scale of the configuration of Cluster spacecraft approaches the thickness of the current layer. Secondly, we show that the estimated current lies in the plane of the boundary and demonstrate this for crossings occurring during large-scale ripples on the magnetopause. Thirdly, we show that the magnitude of the current is accurately represented, averaged over the extent of the current layer, by comparing to the change in the boundary-parallel magnetic field component divided by the estimated current layer thickness. We demonstrate this last point using a range of crossings each having a different thickness and crossing speed, different changes in the magnetic field component and different current densities

Summarised findings from Australian poultry odour research (2005–2018)

D&E related to odour is integral to addressing community concerns, reducing the potential for odour impacts and supporting sustainable growth of the chicken meat industry. By necessity, the industry is typically established on the urban fringe, which increases the potential for amenity impacts. Odour RD&E has involved several research teams, including government agencies, universities, and consultancy businesses. The industry must now undertake the important tasks of broadly reviewing the overall knowledge that has been developed to date, taking stock of the achievements and challenges, and planning the path forward to address emerging and unresolved issues. This project summarises the odour-related RD&E that has been supported by the Australian chicken meat industry (through AgriFutures Australia or the Poultry CRC) since 2005. It was funded by industry revenue, the Australian Government, and the Queensland Government Department of Agriculture and Fisheries

First Cluster results of the magnetic field structure of the mid- and high-altitude cusps

International audienceMagnetic field measurements from the four Cluster spacecraft from the mid- and high-altitude cusp are presented. Cluster underwent two encounters with the mid-altitude cusp during its commissioning phase (24 August 2000). Evidence for field-aligned currents (FACs) was seen in the data from all three operating spacecraft from northern and southern cusps. The extent of the FACs was of the order of 1 RE in the X-direction, and at least 300 km in the Y-direction. However, fine-scale field structures with scales of the order of the spacecraft separation (300 km) were observed within the FACs. In the northern crossing, two of the spacecraft appeared to lie along the same magnetic field line, and observed very well matched signals. However, the third spacecraft showed evidence for structuring transverse to the field on scales of a few hundred km. A crossing of the high-altitude cusp from 13 February 2001 is presented. It is revealed to be a highly dynamic structure with the boundaries moving with velocities ranging from a few km/s to tens of km/s, and having structure on timescales ranging from less than one minute up to several minutes. The cusp proper is associated with the presence of a very disordered magnetic field, which is entirely different from the magnetosheath turbulence

Water addition, evaporation and water holding capacity of poultry litter

Litter moisture content has been related to ammonia, dust and odour emissions as well as bird health and welfare. Improved understanding of the water holding properties of poultry litter as well as water additions to litter and evaporation from litter will contribute to improved litter moisture management during the meat chicken grow-out. The purpose of this paper is to demonstrate how management and environmental conditions over the course of a grow-out affect the volume of water A) applied to litter, B) able to be stored in litter, and C) evaporated from litter on a daily basis. The same unit of measurement has been used to enable direct comparison—litres of water per square metre of poultry shed floor area, L/m2, assuming a litter depth of 5 cm. An equation was developed to estimate the amount of water added to litter from bird excretion and drinking spillage, which are sources of regular water application to the litter. Using this equation showed that water applied to litter from these sources changes over the course of a grow-out, and can be as much as 3.2 L/m2/day. Over a 56 day grow-out, the total quantity of water added to the litter was estimated to be 104 L/m2. Litter porosity, water holding capacity and water evaporation rates from litter were measured experimentally. Litter porosity decreased and water holding capacity increased over the course of a grow-out due to manure addition. Water evaporation rates at 25 °C and 50% relative humidity ranged from 0.5 to 10 L/m2/day. Evaporation rates increased with litter moisture content and air speed. Maintaining dry litter at the peak of a grow-out is likely to be challenging because evaporation rates from dry litter may be insufficient to remove the quantity of water added to the litter on a daily basis

Litter management strategies to reduce odour emissions from poultry litter

Litter conditions in meat chicken sheds are important for providing a healthy and comfortable environment for the birds and to regulate the emission of odours, which can impact on the surrounding community. Litter is considered the primary source of odour in meat chicken sheds. Mismanagement of litter odour control can result in public annoyances and possible breach of regulations. Odour emissions from poultry litter are complex due to: - The existence of multiple odorant sources within litter (i.e. fresh excreta, friable litter and cake); - Formation and emission of numerous odorants; and - Significant spatial and temporal variability of moisture content, porosity, pH, ventilation air-flow, temperature, humidity, and bird activity. To date, there still exists a big knowledge gap in the relationship between specific litter conditions and odour emissions. To address this knowledge gap as well as to help tailor effective litter odour management strategies, this project pursued the following objectives: - Investigate how odour emissions from litter, in terms of chemical composition and emission rates, were affected by different litter conditions. Special attention was paid to water as it affects many of the chemical, physical, and microbial properties of litter. - Review, quantify, and evaluate application of common litter management practices on the formation and emission of odours and odorants from poultry litter