Rocket investigation of the auroral green line

Dissociative excitation and recombination reactions of atomic oxygen by auroral electrons, related to auroral green lin

Differential electron flux as determined by auroral observations of the N2 positive and N2/+/ systems

Measurement of relative emission rates of auroral system

Deactivation of N2A 3 Sigma u plus molecules in the aurora

Analysis of N2A 3 Sigma u positive molecule deactivation in auroras using atmospheric model based on mass spectrometer measurement

Ion composition and ion chemistry in an aurora

Auroral ion distribution and conversion of oxygen protons to nitric oxide proton

Radionuclide measurements by accelerator mass spectrometry at Arizona

Over the past years, Tandem Accelerator Mass Spectrometry (TAMS) has become established as an important method for radionuclide analysis. In the Arizona system the accelerator is operated at a thermal voltage of 1.8MV for C-14 analysis, and 1.6 to 2MV for Be-10. Samples are inserted into a cesium sputter ion source in solid form. Negative ions sputtered from the target are accelerated to about 25kV, and the injection magnet selects ions of a particular mass. Ions of the 3+ charge state, having an energy of about 9MeV are selected by an electrostatic deflector, surviving ions pass through two magnets, where only ions of the desired mass-energy product are selected. The final detector is a combination ionization chamber to measure energy loss (and hence, Z), and a silicon surface-barrier detector which measures residual energy. After counting the trace iosotope for a fixed time, the injected ions are switched to the major isotope used for normalization. These ions are deflected into a Faraday cup after the first high-energy magnet. Repeated measurements of the isotope ratio of both sample and standards results in a measurement of the concentration of the radionuclide. Recent improvements in sample preparation for C-14 make preparation of high-beam current graphite targets directly from CO2 feasible. Except for some measurements of standards and backgrounds for Be-10 measurements to date have been on C-14. Although most results have been in archaeology and quaternary geology, studies have been expanded to include cosmogenic C-14 in meteorites. The data obtained so far tend to confirm the antiquity of Antarctic meteorites from the Allan Hills site. Data on three samples of Yamato meteorites gave terrestrial ages of between about 3 and 22 thousand years

Magneto-resistance in a lithography defined single constrained domain wall spin valve

We have measured domain wall magnetoresistance in a single lithographically constrained domain wall. An H-shaped Ni nano-bridge was fabricated by e-beam lithography with the two sides being single magnetic do- mains showing independent magnetic switching. The connection between the sides constraining the domain wall when the sides line up anti-parallel. The magneto-resistance curve clearly identifies the magnetic con- figurations that are expected from a spin valve-like structure. The value of the magneto-resistance at room temperature is around 0.1% or 0.4 ­. This value is shown to be in agreement with a theoretical formulation based on spin accumulation. Micromagnetic simulations show it is possible to reduce the size of the domain wall further by shortening the length of the bridge

The quantum-mechanical basis of an extended Landau-Lifshitz-Gilbert equation for a current-carrying ferromagnetic wire

An extended Landau-Lifshitz-Gilbert (LLG) equation is introduced to describe the dynamics of inhomogeneous magnetization in a current-carrying wire. The coefficients of all the terms in this equation are calculated quantum-mechanically for a simple model which includes impurity scattering. This is done by comparing the energies and lifetimes of a spin wave calculated from the LLG equation and from the explicit model. Two terms are of particular importance since they describe non-adiabatic spin-transfer torque and damping processes which do not rely on spin-orbit coupling. It is shown that these terms may have a significant influence on the velocity of a current-driven domain wall and they become dominant in the case of a narrow wall.Comment: 19 pages, 1 figur