1,783 research outputs found
Magnetothermodynamics: Measuring equations of state in a relaxed magnetohydrodynamic plasma
We report the first measurements of equations of state of a fully relaxed
magnetohydrodynamic (MHD) laboratory plasma. Parcels of magnetized plasma,
called Taylor states, are formed in a coaxial magnetized plasma gun, and are
allowed to relax and drift into a closed flux conserving volume. Density, ion
temperature, and magnetic field are measured as a function of time as the
Taylor states compress and heat. The theoretically predicted MHD and double
adiabatic equations of state are compared to experimental measurements. We find
that the MHD equation of state is inconsistent with our data.Comment: 4 pages, 4 figure
Measuring The Equations Of State In A Relaxed Magnetohydrodynamic Plasma
We report measurements of the equations of state of a fully relaxed magnetohydrodynamic (MHD) laboratory plasma. Parcels of magnetized plasma, called Taylor states, are formed in a coaxial magnetized plasma gun, and are allowed to relax and drift into a closed flux conserving volume. Density, ion temperature, and magnetic field are measured as a function of time as the Taylor states compress and heat. The theoretically predicted MHD and double adiabatic equations of state are compared to experimental measurements. We find that the MHD equation of state is inconsistent with our data
Magnetothermodynamics: Measurements Of The Thermodynamic Properties In A Relaxed Magnetohydrodynamic Plasma
We have explored the thermodynamics of compressed magnetized plasmas in laboratory experiments and we call these studies ‘magnetothermodynamics’. The experiments are carried out in the Swarthmore Spheromak eXperiment device. In this device, a magnetized plasma source is located at one end and at the other end, a closed conducting can is installed. We generate parcels of magnetized plasma and observe their compression against the end wall of the conducting cylinder. The plasma parameters such as plasma density, temperature and magnetic field are measured during compression using HeNe laser interferometry, ion Doppler spectroscopy and a linear dot{B} probe array, respectively. To identify the instances of ion heating during compression, a PV diagram is constructed using measured density, temperature and a proxy for the volume of the magnetized plasma. Different equations of state are analysed to evaluate the adiabatic nature of the compressed plasma. A three-dimensional resistive magnetohydrodynamic code (NIMROD) is employed to simulate the twisted Taylor states and shows stagnation against the end wall of the closed conducting can. The simulation results are consistent to what we observe in our experiments
Geological Evidence of Paleotsunamis at Torre degli Inglesi (northeast Sicily)
Two layers of fine sand of marine origin occur in a
sequence of organic rich colluvia in an archaeological
excavation at Torre degli Inglesi, on Capo Peloro, northeast
Sicily. Stratigraphic and micropaleontologic analyses
support the hypothesis that these layers are related to
deposition due to paleotsunami waves. Their ages are
constrained both with radiocarbon and archaeological
datings. The age of the oldest layer is coincident with the
17 A.D. earthquake that hit Reggio Calabria but for which
no tsunami was previously reported. The age of the
youngest layer can be only constrained in the range 3rd–
19th century and is tentatively associated to the 6 Feb. 1783
event
Characterisation of flow dynamics within and around an isolated forest, through measurements and numerical simulations
The case study of ‘Bosco Fontana’, a densely-vegetated forest located in the north of Italy, is analysed both
experimentally and numerically to characterise the internal ventilation of a finite forest with a vertically
non-homogeneous canopy. Measurements allow for the evaluation of the turbulent exchange across the forest
canopy. The case study is then reproduced numerically via a two-dimensional RANS simulation, successfully
validated against experimental data. The analysis of the internal ventilation leads to the identification of
seven regions of motion along the predominate-wind direction, for whose definition a new in-canopy stability
parameter was introduced. In the vertical direction, the non-homogeneity of the canopy leads to the separation
of the canopy layer into an upper foliage layer and a lower bush layer, characterised respectively by an
increasing streamwise velocity and turbulence intensity, and a weak backflow. The conclusions report an
improved description of the dynamic layer and regions of motion presented in the literature
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