113 research outputs found
The UK's global gas challenge
A UKERC Research Report exploring the UK's global gas challenge. This report takes an interdisciplinary perspective, which marries energy security insights from politics and international relations, with detailed empirical understanding from energy studies and perspectives from economic geography that emphasise the spatial distribution of actors, networks and resource flows that comprise the global gas industry. Natural gas production in the UK peaked in 2000, and in 2004 it became a net importer. A decade later and the UK now imports about half of the natural gas that it consumes. The central thesis of the project on which this report is based is that as the UKâs gas import dependence has grown, it has effectively been âglobalisingâ its gas security; consequently UK consumers are increasingly exposed to events in global gas markets. - See more at: http://www.ukerc.ac.uk/publications/the-uk-s-global-gas-challenge.html#sthash.wEP831Zn.dpu
Variability of the Accretion Stream in the Eclipsing Polar EP Dra
We present the first high time resolution light curves for six eclipses of
the magnetic cataclysmic variable EP Dra, taken using the superconducting
tunnel junction imager S-Cam2. The system shows a varying eclipse profile
between consecutive eclipses over the two nights of observation. We attribute
the variable stream eclipse after accretion region ingress to a variation in
the amount and location of bright material in the accretion stream. This
material creates an accretion curtain as it is threaded by many field lines
along the accretion stream trajectory. We identify this as the cause of
absorption evident in the light curves when the system is in a high accretion
state. We do not see direct evidence in the light curves for an accretion spot
on the white dwarf; however, the variation of the stream brightness with the
brightness of the rapid decline in flux at eclipse ingress indicates the
presence of some form of accretion region. This accretion region is most likely
located at high colatitude on the white dwarf surface, forming an arc shape at
the foot points of the many field lines channeling the accretion curtain.Comment: Accepted for publication in MNRAS (7 pages
Rethinking Energy Geopolitics: Towards a Geopolitical Economy of Global Energy Transformation
We are in the midst of a global energy system transformation (GEST) which is rewiring the world economy, opening new axes of political contestation, and revolutionising the energetic basis of human civilisation. Energy geopolitics has not yet reconciled itself to this challenge. The field has traditionally been preoccupied with the dependence of Western states on cross-border flows of fossil fuels. More recently, efforts have been made to prospectively map out what the geopolitics of a fully renewable world might look like. What both literatures miss, however, is the very fact of the GEST: that we are living through a changing and contested process of global transformation, across interacting high- and low-emissions systems, whose contours are open and actively constructed over time. In this paper, we start to develop a provisional framework to make sense of the GEST, that is able to capture the full scale of the transformation, and its dynamic, contingent, constructed nature. We attend to three areas of geopolitical economy: the wide-ranging material dimensions of the transformation, its geographical space-making, and its conflict-ridden political economy. We then apply this framework to two case studies, one looking at the fraught role of fossil gas as a âtransition fuelâ, the other at lithium-ion batteries
Accretion stream mapping with genetically modified "fire-flies"
We apply an eclipse mapping technique using `genetically modified fire-flies'
to the eclipse light curves of HU Aqr and EP Dra. The technique makes as few
assumptions as possible about the location of accretion stream material,
allowing the emission to be located anywhere within the Roche lobe of the white
dwarf. We model two consecutive eclipses in the UBVR_c band for HU Aqr, and
four consecutive `white'-light eclipses for EP Dra, to determine the changing
brightness distribution of stream material. We find fire-fly distributions
which are consistent with accretion through a curtain of material in both HU
Aqr and EP Dra, and show that the previously assumed two part ballistic and
magnetic trajectory is a good approximation for polars. Model fits to the
colour band data of HU Aqr indicate that the material confined to the magnetic
field lines is brightest, and most of the emission originates from close to the
white dwarf. There is evidence for emission from close to a calculated
ballistic stream in both HU Aqr and EP Dra.We propose that a change in the
stream density causes a change in the location of the bright material in the
accretion stream in EP Dra.Comment: accepted for publication in MNRA
XMM-Newton observations of the eclipsing polar EP Dra
We present XMM-Newton observations of the eclipsing polar EP Dra which cover
nearly 3 binary orbital cycles. The X-ray and UV data show evidence for a
prominent dip before the eclipse which is due to the accretion stream obscuring
the accretion region. The dip ingress is rapid in hard X-rays suggesting there
is a highly collimated core of absorption. We find that a different level of
absorption column density is required to match the observed count rates in
different energy bands. We propose that this is due to the fact that different
absorption components should be used to model the reprocessed X-rays, the
shocked X-ray component and the UV emission and explore the affect that this
has on the resulting fits to the spectrum. Further, there is evidence that
absorption starts to obscure the softer X-rays shortly after the onset of the
bright phase. This suggests that material is threaded by an unusually wide
range of magnetic field lines, consistent with the suggestion of Bridge et al.
We find that the period is slightly greater than that determined by Schwope &
Mengel.Comment: Accepted for publication MNRAS, 6 page
Rethinking energy geopolitics : towards a geopolitical economy of global energy transformation
We are in the midst of a global energy system transformation (GEST) which is rewiring the world economy, opening new axes of political contestation, and revolutionising the energetic basis of human civilisation. Energy geopolitics has not yet reconciled itself to this challenge. The field has traditionally been preoccupied with the dependence of Western states on cross-border flows of fossil fuels. More recently, efforts have been made to prospectively map out what the geopolitics of a fully renewable world might look like. What both literatures miss, however, is the very fact of the GEST: that we are living through a changing and contested process of global transformation, across interacting high- and low-emissions systems, whose contours are open and actively constructed over time. In this paper, we start to develop a provisional framework to make sense of the GEST, that is able to capture the full scale of the transformation, and its dynamic, contingent, constructed nature. We attend to three areas of geopolitical economy: the wide-ranging material dimensions of the transformation, its geographical space-making, and its conflict-ridden political economy. We then apply this framework to two case studies, one looking at the fraught role of fossil gas as a âtransition fuelâ, the other at lithium-ion batteries
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