Spacecraft-induced plasma energization and its role in flow phenomena

Plasma instabilities induced by orbiting vehicles can cause many important phenomena ranging from electron and ion heating and suprathermal electron tail energization, to enhanced ionization and optical emissions. We outline the basic collective processes leading to plasma energization near plasma sheaths and in regions of neutral gas streaming through plasma, and discuss the role of the induced collective effects in producing the optical emission spectra

Physiotherapy effectiveness on muscle strength, flexibility, pain and function in patients with patellofemoral pain syndrome

Study objectives: To evaluate the effectiveness on muscle strength, flexibility, pain and function of a six-week physiotherapy treatment for patients with Patellofemoral Pain Syndrome delivered in a district North-West Wales National Health Service Hospital. Methods: 26 patients with Patellofemoral Pain Syndrome (9 males, 16 females) who were referred to the NHS physiotherapy department where asked to complete an AKP Scale and two VASs along with a series of clinical tests that measure lower limb isometric strength and flexibility in two different occasions; The first occasion took place directly after the first treatment session with the physiotherapist; the second occasion took place directly after the last physiotherapy visit which was approximately after 5-8 weeks. Results: The data showed that physiotherapy treatment in patients with PFPS did not improve strength (measured by the lower limb isometric strength tests or flexibility (measured by the modified Thomas and hamstrings flexibility test) however; pain measured by two VASs (one for usual pain and one for pain on the day of the assessment) and function measured by the AKP Scale function, were significantly improved (VASs p<0.02 & AKP Scale p<0.01 ). Conclusions: This study reported that physiotherapy treatment in patients with PFPS works, not through strength and flexibility but through other components. There are several possible explanations for the results of this study. Future studies should aim to identify the different treatment components and which of these really work for patients with PFPS

Absence of Electron Surfing Acceleration in a Two-Dimensional Simulation

Electron acceleration in high Mach number perpendicular shocks is investigated through two-dimensional electrostatic particle-in-cell (PIC) simulation. We simulate the shock foot region by modeling particles that consist of three components such as incident protons and electrons and reflected protons in the initial state which satisfies the Buneman instability condition. In contrast to previous one-dimensional simulations in which strong surfing acceleration is realized, we find that surfing acceleration does not occur in two-dimensional simulation. This is because excited electrostatic potentials have a two-dimensional structure that makes electron trapping impossible. Thus, the surfing acceleration does not work either in itself or as an injection mechanism for the diffusive shock acceleration. We briefly discuss implications of the present results on the electron heating and acceleration by shocks in supernova remnants.Comment: 12 pages, 4 figures, accepted for publication in ApJ

A theory of solar type 3 radio bursts

Energetic electrons propagating through the interplanetary medium are shown to excite the one dimensional oscillating two stream instability (OTSI). The OTSI is in turn stabilized by anomalous resistivity which completes the transfer of long wavelength Langmuir waves to short wavelengths, out of resonance with the electrons. The theory explains the small energy losses suffered by the electrons in propagating to 1 AU, the predominance of second harmonic radiation, and the observed correlation between radio and electron fluxes

Nonlinear stability of solar type 3 radio bursts. 1: Theory

A theory of the excitation of solar type 3 bursts is presented. Electrons initially unstable to the linear bump-in-tail instability are shown to rapidly amplify Langmuir waves to energy densities characteristic of strong turbulence. The three-dimensional equations which describe the strong coupling (wave-wave) interactions are derived. For parameters characteristic of the interplanetary medium the equations reduce to one dimension. In this case, the oscillating two stream instability (OTSI) is the dominant nonlinear instability, and is stablized through the production of nonlinear ion density fluctuations that efficiently scatter Langmuir waves out of resonance with the electron beam. An analytical model of the electron distribution function is also developed which is used to estimate the total energy losses suffered by the electron beam as it propagates from the solar corona to 1 A.U. and beyond

Nonlinear stability of solar type 3 radio bursts. 2: Application to observations near 1 AU

A set of rate equations including strong turbulence effects and anomalous resitivity are solved using parmeters which model several solar type 3 bursts. Exciter distributions observed at 1 AU are excitation of the linear bump-in-tail instability, amplifying Langmuir waves above the threshold for the oscillating two stream instability (OTSI). The OTSI, and the attendant anomalous resistivity produce a rapid spectral transfer of Langmuir waves to short wavelengths, out of resonance with the electron exciter. Further energy loss of the beam is thus precluded. The various parameters needed to model the bursts are extrapolated inside 1 AU with similar results. Again, the OTSI is excited and decouples the electron beam from the Langmuir radiation. Reabsorption of the Langmuir waves by the beam is shown to be unimportant in all cases, even at 0.1 AU. The theory provides a natural explanation for the observed realationship between radio flux, and the electron flux

Stabilization of electron streams in type 3 solar radio bursts

It is shown that the electron streams that give rise to Type 3 solar radio bursts are stable and will not be decelerated while propagating out of the solar corona. The stabilization mechanism depends on the parametric oscillating two stream instability. Radiation is produced near the fundamental and second harmonic of the local electron plasma frequency. Estimates of the emission at the second harmonic indicate that the wave spectra created by the oscillating two stream instability can account for the observed intensities of Type 3 bursts

Pairing of 1-hexyl-3-methylimidazolium and tetrafluoroborate ions in n-pentanol

Molecular dynamics simulations are obtained and analyzed to study pairing of 1-hexyl-3-methylimidazolium and tetrafluoroborate ions in n-pentanol, in particular by evaluating the potential-of-mean-force between counter ions. The present molecular model and simulation accurately predicts the dissociation constant Kd in comparison to experiment, and thus the behavior and magnitudes for the ion-pair pmf at molecular distances, even though the dielectric constant of the simulated solvent differs from the experimental value by about 30%. A naive dielectric model does not capture molecule structural effects such as multiple conformations and binding geometries of the Hmim+ and BF4- ion-pairs. Mobilities identify multiple time-scale effects in the autocorrelation of the random forces on the ions, and specifically a slow, exponential time-decay of those long-ranged forces associated here with dielectric friction effects.Comment: 5 pages, 7 figures. V2: Figs. 4 & 7 redrawn for better visual clarity with log-scales. No change in results. In press J. Chem. Phys. 201