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

Historical, archeological and geological records of strong earthquakes at Capo Peloro (southern Italy)

During the 4th century AD southern Calabria and eastern Sicily were hit by an earthquake documented by archaeoseismic analyses, which was interpreted by Guidoboni et al. (2000) as the predecessor of the well-know 1908 earthquake, located in Messina Strait, whereas Galli and Bosi (2002) interpreted this event as the precedessor of the 1783 earthquake. The purpose of this paper is to find further evidence of these earthquakes in Messina area by a multidisciplinary study aimed to recognize and date historical and paleo-earthquakes. For this goal we have analyzed historical, archaeological and geological information of excavations performed at Capo Peloro near the Torre del Faro village (Fig. 1) in the Torre degli Inglesi (English Tower), built on an abandoned Roman tower

A unique 4000 year long geological record of multiple tsunami inundations in the Augusta Bay (eastern Sicily, Italy)

We present the geological evidence for a 4000 year long record of multiple tsunami inundations along the coast of the Augusta Bay (eastern Sicily)and discuss its implications. The research was carried out through a multi-theme approach which benefited from an extraordinarily long historical record that we used to guide detailed geomorphologic and geologic surveys, coring campaigns and laboratory analyses. Two sites, named the Augusta Hospital and Priolo Reserve, were selected and investigated in detail along the 25 km-long coastline of Augusta Bay. We found evidence for six (possibly seven) tsunami deposits; three of them may be tentatively associated with the 1693 and 365 AD Ionian Sea historical tsunamis and the ~3600 BP Santorini event. The other three (possibly four) deposits are evidence for unknown paleo-inundations dated at about 650–770 AD, 600–400 BC and 975–800 BC (at Augusta Hospital site), and 800–600 BC (at Priolo Reserve site). We use these ages to extend further back the historical record of tsunamis available for this coastal area. The exceptional number of tsunami deposits found with this study allowed us to derive an average geologic tsunami recurrence interval in the Augusta Bay of about 600 years for the past 4 ka. Conversely, the historical tsunami data for the past millennium suggest an average tsunami recurrence interval of about 250 years. This difference in the average recurrence intervals suggests that only the strongest inundations may leave recognizable geological signatures at the investigated sites (i.e. the evidence for the 1908 and 1169 tsunamis is missing) but also that the geomorphological setting of the site and its erosional/depositional history are critical aspects for the data recording. Thus, an average recurrence interval derived from the geological record should be considered as a minimum figure. The identification and age estimation of tsunami deposits represent a new and independent contribution to tsunami scenarios and modeling for coastal hazard assessment in Civil Protection applications. Furthermore, our study cases provide new elements on tsunami deposit recognition related to exceptionally large events that occurred in the Aegean Sea