We present an experimental study of the development and structure of bow shocks produced by the interaction of a magnetised, collisional, super-Alfv enic plasma flow with conducting cylindrical obstacles. The plasma flow with an embedded, frozen-in magnetic field (Re M $ 20) is produced by the current-driven ablation of fine aluminium wires in an inverse, exploding wire array z-pinch. We show that the orientation of the embedded field with respect to the obstacles has a dramatic effect on the bow shock structure. When the field is aligned with the obstacle, a sharp bow shock is formed with a global structure that is determined simply by the fast magneto-sonic Mach number. When the field is orthogonal to the obstacle, magnetic draping occurs. This leads to the growth of a magnetic precursor and the subsequent development of a magnetised bow shock that is mediated by two-fluid effects, with an opening angle and a stand-off distance, that are both many times larger than in the parallel geometry. By changing the field orientation, we change the fluid regime and physical mechanisms that are responsible for the development of the bow shocks. MHD simulations show good agreement with the structure of well-developed bow shocks. However, collisionless, two-fluid effects will need to be included within models to accurately reproduce the development of the shock with an orthogonal B-field. Published by AIP Publishing.

This work presents a magnetic reconnection experiment in which the kinetic, magnetic and thermal properties of the plasma each play an important role in the overall energy balance and structure of the generated reconnection layer. Magnetic reconnection occurs during the interaction of continuous and steady flows of super-Alfvénic, magnetized, aluminum plasma, which collide in a geometry with two-dimensional symmetry, producing a stable and long-lasting reconnection layer. Optical Thomson scattering measurements show that when the layer forms, ions inside the layer are more strongly heated than electrons, reaching temperatures of T i~Z ̅ T e ≳ 300 eVmuch greater than can be expected from strong shock and viscous heating alone. Later in time, as the plasma density in the layer increases, the electron and ion temperatures are found to equilibrate, and a constant plasma temperature is achieved through a balance of the heating mechanisms and radiative losses of the plasma. Measurements from Faraday rotation polarimetry also indicate the presence of significant magnetic field pile-up occurring at the boundary of the reconnection region, which is consistent with the super-Alfvénic velocity of the inflows.

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Purpose -The purpose of this paper is to explore the demand and supply relationship between urban and non-urban land, the latter's diminishing supply, arguments for and against its preservation, methods in which preservation might be achieved and one method in particular, with which the authors have considerable experience, that involves the purchase of development rights and density credits. Design/methodology/approach -The research design involved meetings with farmers, city and county officials and members of several land conservation organizations, bringing together several hundred agricultural and residential real estate transactions, quantitative analysis of the transaction data using descriptive and hedonic methods, developing property attribute values and thereby determining the value of agricultural development rights and urban density credits. Findings -Agricultural development rights were valued, on average, at $9,000 per acre. Commercial development rights were valued, on average, at $9.00 per square foot of floor area (FAR). Practical implications -By acquiring agricultural development rights the process of agricultural land being converted to urban purposes can be slowed or halted. Valuing and selling development rights is a straightforward means of permitting urban density that is understood by developers and easily, objectively and transparently quantified. It is also a good method of raising funds for the acquisition of agricultural development rights. Originality/value -The valuation process developed and employed does away with the need for individual appraisals of rights to be acquired and sold. Therefore this is a very efficient process. Also, it shows how farmers, preservationists and planners can be brought together to solve a common problem.

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