Electron Signatures of Reconnection in a Global eVlasiator Simulation.

Geospace plasma simulations have progressed toward more realistic descriptions of the solar wind-magnetosphere interaction from magnetohydrodynamic to hybrid ion-kinetic, such as the state-of-the-art Vlasiator model. Despite computational advances, electron scales have been out of reach in a global setting. eVlasiator, a novel Vlasiator submodule, shows for the first time how electromagnetic fields driven by global hybrid-ion kinetics influence electrons, resulting in kinetic signatures. We analyze simulated electron distributions associated with reconnection sites and compare them with Magnetospheric Multiscale (MMS) spacecraft observations. Comparison with MMS shows that key electron features, such as reconnection inflows, heated outflows, flat-top distributions, and bidirectional streaming, are in remarkable agreement. Thus, we show that many reconnection-related features can be reproduced despite strongly truncated electron physics and an ion-scale spatial resolution. Ion-scale dynamics and ion-driven magnetic fields are shown to be significantly responsible for the environment that produces electron dynamics observed by spacecraft in near-Earth plasmas.

Kinetic Generation of Whistler Waves in the Turbulent Magnetosheath.

The Earth's magnetosheath (MSH) is governed by numerous physical processes which shape the particle velocity distributions and contribute to the heating of the plasma. Among them are whistler waves which can interact with electrons. We investigate whistler waves detected in the quasi-parallel MSH by NASA's Magnetospheric Multiscale mission. We find that the whistler waves occur even in regions that are predicted stable to wave growth by electron temperature anisotropy. Whistlers are observed in ion-scale magnetic minima and are associated with electrons having butterfly-shaped pitch-angle distributions. We investigate in detail one example and, with the support of modeling by the linear numerical dispersion solver Waves in Homogeneous, Anisotropic, Multicomponent Plasmas, we demonstrate that the butterfly distribution is unstable to the observed whistler waves. We conclude that the observed waves are generated locally. The result emphasizes the importance of considering complete 3D particle distribution functions, and not only the temperature anisotropy, when studying plasma wave instabilities.

Structure of a Perturbed Magnetic Reconnection Electron Diffusion Region in the Earth's Magnetotail.

We report in situ observations of an electron diffusion region (EDR) and adjacent separatrix region in the Earth's magnetotail. We observe significant magnetic field oscillations near the lower hybrid frequency which propagate perpendicularly to the reconnection plane. We also find that the strong electron-scale gradients close to the EDR exhibit significant oscillations at a similar frequency. Such oscillations are not expected for a crossing of a steady 2D EDR, and can be explained by a complex motion of the reconnection plane induced by current sheet kinking propagating in the out-of-reconnection-plane direction. Thus, all three spatial dimensions have to be taken into account to explain the observed perturbed EDR crossing. These results shed light on the interplay between magnetic reconnection and current sheet drift instabilities in electron-scale current sheets and highlight the need for adopting a 3D description of the EDR, going beyond the two-dimensional and steady-state conception of reconnection.

Extraoral traction and class III treatment.

True Class III malocclusions are difficult to treat because they reflect basal bone discrepancies and there are many limitations to conventional treatment mechanisms. For example, Class III elastics may adversely affect the inclination of the occlusal plane and bite depth. On the other hand, extraoral appliances can be used advantageously. One important application is to move a retrognathically positioned maxilla forward orthopedically by means of the facial mask of Delaire. In addition, extraoral appliances placed against the lower incisor segment can also be used to retract the mandibular incisors and control bite depth during the retraction procedure.

In vivo effect of oral environment on etched enamel: a scanning electron microscopic study.

After etching the enamel in teeth of young children with 50% buffered phosphoric acid and allowing the teeth to remain in the oral environment for a few months, an irregular enamel surface similar to the morphology of recently etched enamel was noted by means of scanning electron microscopy. In addition, the enamel surfaces were covered with plaque. Accordingly, observations by other authors, that etched human enamel takes on a normal appearance after short exposure in the oral cavity, could not be confirmed. However, when the surface of the etched enamel was pumiced, the enamel reacquired both the shine and appearance of non-etched enamel.