3,153 research outputs found
Emergence of District-Heating Networks; Barriers and Enablers in the Development Process
Infrastructure provision business models that promise resource efficiencies and additional benefits, such as job
creation, community cohesion and crime reduction exist at sub-national scales. These local business models,
however, exist only as isolated cases of good practice and their expansion and wider adoption has been limited in
the context of many centralised systems that are currently the norm. In this contribution, we present a conceptual
agent based model for analysing the potential for different actors to implement local infrastructure provision business
models. The model is based on agentsâ ability to overcome barriers that occur throughout the development (i.e.
feasibility, business case, procurement, and construction), and operation and maintenance of alternative business
models. This presents a novel approach insofar as previous models have concentrated on the acceptance of
alternative value provision models rather than the emergence of underlying business models. We implement the
model for the case study of district heating networks in the UK, which have the potential to significantly contribute to
carbon emission reductions, but remain under-developed compared with other European countries
Detailed Structure and Dynamics in Particle-in-Cell Simulations of the Lunar Wake
The solar wind plasma from the Sun interacts with the Moon, generating a wake
structure behind it, since the Moon is to a good approximation an insulator,
has no intrinsic magnetic field and a very thin atmosphere. The lunar wake in
simplified geometry has been simulated via a 1-1/2-D electromagnetic
particle-in-cell code, with high resolution in order to resolve the full phase
space dynamics of both electrons and ions. The simulation begins immediately
downstream of the moon, before the solar wind has infilled the wake region,
then evolves in the solar wind rest frame. An ambipolar electric field and a
potential well are generated by the electrons, which subsequently create a
counter-streaming beam distribution, causing a two-stream instability which
confines the electrons. This also creates a number of electron phase space
holes. Ion beams are accelerated into the wake by the ambipolar electric field,
generating a two stream distribution with phase space mixing that is strongly
influenced by the potentials created by the electron two-stream instability.
The simulations compare favourably with WIND observations.Comment: 10 pages, 13 figures, to be published in Physics of Plasma
Magnetic fluctuation power near proton temperature anisotropy instability thresholds in the solar wind
The proton temperature anisotropy in the solar wind is known to be
constrained by the theoretical thresholds for pressure anisotropy-driven
instabilities. Here we use approximately 1 million independent measurements of
gyroscale magnetic fluctuations in the solar wind to show for the first time
that these fluctuations are enhanced along the temperature anisotropy
thresholds of the mirror, proton oblique firehose, and ion cyclotron
instabilities. In addition, the measured magnetic compressibility is enhanced
at high plasma beta () along the mirror instability
threshold but small elsewhere, consistent with expectations of the mirror mode.
The power in this frequency (the 'dissipation') range is often considered to be
driven by the solar wind turbulent cascade, an interpretation which should be
qualified in light of the present results. In particular, we show that the
short wavelength magnetic fluctuation power is a strong function of
collisionality, which relaxes the temperature anisotropy away from the
instability conditions and reduces correspondingly the fluctuation power.Comment: 4 pages, 4 figure
Kinetic Scale Density Fluctuations in the Solar Wind
We motivate the importance of studying kinetic scale turbulence for
understanding the macroscopic properties of the heliosphere, such as the
heating of the solar wind. We then discuss the technique by which kinetic scale
density fluctuations can be measured using the spacecraft potential, including
a calculation of the timescale for the spacecraft potential to react to the
density changes. Finally, we compare the shape of the density spectrum at ion
scales to theoretical predictions based on a cascade model for kinetic
turbulence. We conclude that the shape of the spectrum, including the ion scale
flattening, can be captured by the sum of passive density fluctuations at large
scales and kinetic Alfven wave turbulence at small scales
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