Modeling Kelvin-Helmholtz Instability at the High-Latitude Boundary Layer in a Global Magnetosphere Simulation.

The Kelvin-Helmholtz instability at the magnetospheric boundary plays a crucial role in solar wind-magnetosphere-ionosphere coupling, particle entry, and energization. The full extent of its impact has remained an open question due, in part, to global models without sufficient resolution to capture waves at higher latitudes. Using global magnetohydrodynamic simulations, we investigate an event when the Magnetospheric Multiscale (MMS) mission observed periodic low-frequency waves at the dawn-flank, high-latitude boundary layer. We show the layer to be unstable, even though the slow solar wind with the draped interplanetary magnetic field is seemingly unfavorable for wave generation. The simulated velocity shear at the boundary is thin ( ∼ 0.65 R E ) and requires commensurately high spatial resolution. These results, together with MMS observations, confirm for the first time in fully three-dimensional global geometry that KH waves can grow in this region and thus can be an important process for energetic particle acceleration, dynamics, and transport.

Ballooning-Interchange Instability in the Near-Earth Plasma Sheet and Auroral Beads: Global Magnetospheric Modeling at the Limit of the MHD Approximation.

Explosive magnetotail activity has long been understood in the context of its auroral manifestations. While global models have been used to interpret and understand many magnetospheric processes, the temporal and spatial scales of some auroral forms have been inaccessible to global modeling creating a gulf between observational and theoretical studies of these phenomena. We present here an important step toward bridging this gulf using a newly developed global magnetosphere-ionosphere model with resolution capturing ≲ 30 km azimuthal scales in the auroral zone. In a global magnetohydrodynamic (MHD) simulation of the growth phase of a synthetic substorm, we find the self-consistent formation and destabilization of localized magnetic field minima in the near-Earth magnetotail. We demonstrate that this destabilization is due to ballooning-interchange instability which drives earthward entropy bubbles with embedded magnetic fronts. Finally, we show that these bubbles create localized field-aligned current structures that manifest in the ionosphere with properties matching observed auroral beads.

Further evidence that a mouse chromosome 4 locus influences cerebellar folial pattern.

The cerebellar folial pattern of mice displays marked variation among inbred strains. Previous studies of progeny of crosses of C57BL/6 mice with DBA/2J and BALB/cByJ mice indicated a multifactorial mode of inheritance in both cases. The cross with DBA/2J led to the mapping, to Chromosome 4, of a locus (Cfp-1) that influences the frequency of the intraculminate fissure. Here we report that Cfp-1 influences the frequency of the declival sulcus, and appears to influence the frequency of the intraculminate and precentral fissures, in F2 hybrid offspring from crosses of C57BL/6J and BALB/cByJ mice.

Genetic analysis of cerebellar folial pattern in crosses of C57BL/6J and DBA/2J inbred mice.

Variation in the cerebellar folial pattern of mice is influenced by genetic elements [Inouye, M. and Oda, S., J. Comp. Neurol., 190 (1980) 357-362]. In crosses of C57BL/6J and DBA/2J inbred mice, the presence or absence of a specific fissure, the intraculminate fissure, is largely determined by a single genetic locus (Cfp-1), which is located on distal Chromosome 4 [Neumann et al., Brain Res., 524 (1990) 85-89]. In the present study, the mid-sagittal cerebellar folial pattern has been examined in crosses of C57BL/6J and DBA/2J mice and in BXD recombinant inbred strains. At least three loci, including Cfp-1, are involved in variation in vermian pattern formation. Genetic variation in thyroid hormone function may be involved in the inheritance of folial pattern. A locus (Cfp-2) that appears to be partially responsible for this negative genetic correlation in mice may be linked to Afp on Chromosome 5. This hypothesis was suggested by the negative correlation between neonatal serum T4 level and the number of folia in rats given neonatal injections of thyroxine or propylthiouracil [Lauder, J.M. et al., Brain Res., 76 (1974) 33-40].

MR imaging of phenylketonuria.

Cranial MR imaging was performed on nine patients (13-27 years old) with classical phenylketonuria in order to define the spectrum of abnormal findings and to determine if these could be related to clinical or biochemical findings. MR abnormalities consistent with demyelination were found in varying degrees in a distribution corresponding to previous histopathologic studies. Specifically, increased signal was seen on T2-weighted sequences, most marked in the periventricular deep cerebral white matter. These changes were more prominent posteriorly, especially about the optic radiations. Comparison with clinical history and MR findings in this small series revealed that patients with adequate dietary control of phenylalanine levels had less severe white matter abnormalities than did patients with poorly controlled phenylalanine intake.