38 research outputs found
Review article: MHD wave propagation near coronal null points of magnetic fields
We present a comprehensive review of MHD wave behaviour in the neighbourhood
of coronal null points: locations where the magnetic field, and hence the local
Alfven speed, is zero. The behaviour of all three MHD wave modes, i.e. the
Alfven wave and the fast and slow magnetoacoustic waves, has been investigated
in the neighbourhood of 2D, 2.5D and (to a certain extent) 3D magnetic null
points, for a variety of assumptions, configurations and geometries. In
general, it is found that the fast magnetoacoustic wave behaviour is dictated
by the Alfven-speed profile. In a plasma, the fast wave is focused
towards the null point by a refraction effect and all the wave energy, and thus
current density, accumulates close to the null point. Thus, null points will be
locations for preferential heating by fast waves. Independently, the Alfven
wave is found to propagate along magnetic fieldlines and is confined to the
fieldlines it is generated on. As the wave approaches the null point, it
spreads out due to the diverging fieldlines. Eventually, the Alfven wave
accumulates along the separatrices (in 2D) or along the spine or fan-plane (in
3D). Hence, Alfven wave energy will be preferentially dissipated at these
locations. It is clear that the magnetic field plays a fundamental role in the
propagation and properties of MHD waves in the neighbourhood of coronal null
points. This topic is a fundamental plasma process and results so far have also
lead to critical insights into reconnection, mode-coupling, quasi-periodic
pulsations and phase-mixing.Comment: 34 pages, 5 figures, invited review in Space Science Reviews => Note
this is a 2011 paper, not a 2010 pape
Stores healthy options project in remote indigenous communities (SHOP@RIC): a protocol of a randomised trial promoting healthy food and beverage purchases through price discounts and in-store nutrition education
BackgroundIndigenous Australians suffer a disproportionate burden of preventable chronic disease compared to their non-Indigenous counterparts – much of it diet-related. Increasing fruit and vegetable intakes and reducing sugar-sweetened soft-drink consumption can reduce the risk of preventable chronic disease. There is evidence from some general population studies that subsidising healthier foods can modify dietary behaviour. There is little such evidence relating specifically to socio-economically disadvantaged populations, even though dietary behaviour in such populations is arguably more likely to be susceptible to such interventions.This study aims to assess the impact and cost-effectiveness of a price discount intervention with or without an in-store nutrition education intervention on purchases of fruit, vegetables, water and diet soft-drinks among remote Indigenous communities.Methods/DesignWe will utilise a randomised multiple baseline (stepped wedge) design involving 20 communities in remote Indigenous Australia. The study will be conducted in partnership with two store associations and twenty Indigenous store boards. Communities will be randomised to either i) a 20% price discount on fruit, vegetables, water and diet soft-drinks; or ii) a combined price discount and in-store nutrition education strategy. These interventions will be initiated, at one of five possible time-points, spaced two-months apart. Weekly point-of-sale data will be collected from each community store before, during, and for six months after the six-month intervention period to measure impact on purchasing of discounted food and drinks. Data on physical, social and economic factors influencing weekly store sales will be collected in order to identify important covariates. Intervention fidelity and mediators of behaviour change will also be assessed.DiscussionThis study will provide original evidence on the effectiveness and cost-effectiveness of price discounts with or without an in-store nutrition education intervention on food and drink purchasing among a socio-economically disadvantaged population in a real-life setting