855 research outputs found
IMPACTS OF GLOBALIZATION ON AGRICULTURAL COMPETITIVENESS: THE CASE OF NAFTA
Major components of agricultural competitiveness, including definitions, factors, and indicators of competitiveness, are discussed, The case of the North American Free Trade Agreement (NAFTA) is used to illustrate how factors have influenced the competitive position of the NAFTA countries. Traditional neoclassical trade theory is used to evaluate the impact of currency exchange rate fluctuations and trade preferences on agricultural competitiveness. Pre- and post-NAFTA market shares are evaluated for five agricultural commodities of importance to the southern United States. The results of these evaluations are compared with theoretical expectations and discussed with special emphasis on implications for future trade negotiations.agricultural competitiveness, exchange rates, international trade, NAFTA, International Relations/Trade, F14, Q17, Q18,
Atypical Particle Heating at a Supercritical Interplanetary Shock
We present the first observations at an interplanetary shock of large amplitude (> 100 mV/m pk-pk) solitary waves and large amplitude (approx.30 mV/m pk-pk) waves exhibiting characteristics consistent with electron Bernstein waves. The Bernstein-like waves show enhanced power at integer and half-integer harmonics of the cyclotron frequency with a broadened power spectrum at higher frequencies, consistent with the electron cyclotron drift instability. The Bernstein-like waves are obliquely polarized with respect to the magnetic field but parallel to the shock normal direction. Strong particle heating is observed in both the electrons and ions. The observed heating and waveforms are likely due to instabilities driven by the free energy provided by reflected ions at this supercritical interplanetary shock. These results offer new insights into collisionless shock dissipation and wave-particle interactions in the solar wind
Characteristics of Electron Distributions Observed During Large Amplitude Whistler Wave Events in the Magnetosphere
We present a statistical study of the characteristics of electron distributions associated with large amplitude whistler waves inside the terrestrial magnetosphere using waveform capture data as an addition of the study by Kellogg et al., [2010b]. We identified three types of electron distributions observed simultaneously with the whistler waves including beam-like, beam/flattop, and anisotropic distributions. The whistlers exhibited different characteristics dependent upon the observed electron distributions. The majority of the waveforms observed in our study have f/fce or = 8 nT pk-pk) whistler wave measured in the radiation belts. The majority of the largest amplitude whistlers occur during magnetically active periods (AE > 200 nT)
Kinetic Theory and Fast Wind Observations of the Electron Strahl
We develop a model for the strahl population in the solar wind -- a narrow,
low-density and high-energy electron beam centered on the magnetic field
direction. Our model is based on the solution of the electron drift-kinetic
equation at heliospheric distances where the plasma density, temperature, and
the magnetic field strength decline as power-laws of the distance along a
magnetic flux tube. Our solution for the strahl depends on a number of
parameters that, in the absence of the analytic solution for the full electron
velocity distribution function (eVDF), cannot be derived from the theory. We
however demonstrate that these parameters can be efficiently found from
matching our solution with observations of the eVDF made by the Wind
satellite's SWE strahl detector. The model is successful at predicting the
angular width (FWHM) of the strahl for the Wind data at 1 AU, in particular by
predicting how this width scales with particle energy and background density.
We find the strahl distribution is largely determined by the local temperature
Knudsen number , which parametrizes solar wind
collisionality. We compute averaged strahl distributions for typical Knudsen
numbers observed in the solar wind, and fit our model to these data. The model
can be matched quite closely to the eVDFs at 1 AU, however, it then
overestimates the strahl amplitude at larger heliocentric distances. This
indicates that our model may be improved through the inclusion of additional
physics, possibly through the introduction of "anomalous diffusion" of the
strahl electrons
THEMIS Observations of the Magnetopause Electron Diffusion Region: Large Amplitude Waves and Heated Electrons
We present the first observations of large amplitude waves in a well-defined
electron diffusion region at the sub-solar magnetopause using data from one
THEMIS satellite. These waves identified as whistler mode waves, electrostatic
solitary waves, lower hybrid waves and electrostatic electron cyclotron waves,
are observed in the same 12-sec waveform capture and in association with
signatures of active magnetic reconnection. The large amplitude waves in the
electron diffusion region are coincident with abrupt increases in electron
parallel temperature suggesting strong wave heating. The whistler mode waves
which are at the electron scale and enable us to probe electron dynamics in the
diffusion region were analyzed in detail. The energetic electrons (~30 keV)
within the electron diffusion region have anisotropic distributions with
T_{e\perp}/T_{e\parallel}>1 that may provide the free energy for the whistler
mode waves. The energetic anisotropic electrons may be produced during the
reconnection process. The whistler mode waves propagate away from the center of
the 'X-line' along magnetic field lines, suggesting that the electron diffusion
region is a possible source region of the whistler mode waves
Evaluating Rural Water System Pricing Strategies Using Mathematical Programming
Agricultural Economic
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