MESSENGER observations of the dayside low‐latitude boundary layer in Mercury’s magnetosphere

Observations from MErcury Surface Space ENvironment GEochemistry, and Ranging (MESSENGER)’s Magnetometer and Fast Imaging Plasma Spectrometer instruments during the first orbital year have resulted in the identification of 25 magnetopause crossings in Mercury’s magnetosphere with significant low‐latitude boundary layers (LLBLs). Of these crossings 72% are observed dawnside and 65% for northward interplanetary magnetic field. The estimated LLBL thickness is 450 ± 56 km and increases with distance to noon. The Na+ group ion is sporadically present in 14 of the boundary layers, with an observed average number density of 22 ± 11% of the proton density. Furthermore, the average Na+ group gyroradii in the layers is 220 ± 34 km, the same order of magnitude as the LLBL thickness. Magnetic shear, plasma β and reconnection rates have been estimated for the LLBL crossings and compared to those of a control group (non‐LLBL) of 61 distinct magnetopause crossings which show signs of nearly no plasma inside the magnetopause. The results indicate that reconnection is significantly slower, or even suppressed, for the LLBL crossings compared to the non‐LLBL cases. Possible processes that form or impact the LLBL are discussed. Protons injected through the cusp or flank may be important for the formation of the LLBL. Furthermore, the opposite asymmetry in the Kelvin‐Helmholtz instability (KHI) as compared to the LLBL rules out the KHI as a dominant formation mechanism. However, the KHI and LLBL could be related to each other, either by the impact of sodium ions gyrating across the magnetopause or by the LLBL preventing the growth of KH waves on the dawnside.Key PointsInvestigation, characterization, and observation of the low‐latitude boundary layer of MercuryIs there a relation between the Kelvin‐Helmholtz instability and the low‐latitude boundary layerInvestigate for what surrounding conditions the low‐latitude boundary layer occursPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136336/1/jgra52122_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136336/2/jgra52122.pd

Use of ion beams in space

Ion beams of MeV energy are in routine use as depth microscopes to determine composition and impurity profiles with depth resolutions of 100-300 Å over near-surface regions. Backscattering spectrometry with He ions and proton-induced x-rays are simple to implement. These techniques have been used in studies of thin-film reactions, solid-phase epitaxy, metallurgy of integrated circuits and solar cells, oxidation and corrosion, and other near-surface phenomena. The Spacelab orbital environment provides the possibility of depositing contamination-free films on clean interfaces. Ion beam techniques for material analysis can then be used to evaluate thin-film interdiffusion, and compound formation in a contaminant-free ambient. In addition, the ion beam techniques would be available for rapid analysis of near-surface regions of other experiments, such as molecular-beam epitaxy. The instrumentation-semiconductor nuclear-particle detectors and multichannel analyzer for such measurements are simple and were used in early Surveyor lunar analyses. The accelerator is based on the tandem accelerator principle pumped by the vacuum of space. It consists of a series of eight light equispaced titanium concentric spheres which are supported on a single insulating hollow column. The largest sphere which is at the potential of the spacecraft has a diameter of 200 cm. The smallest sphere has a diameter of 30 cm and is maintained at l MV potential. Voltage is generated between the largest sphere and the smallest sphere by using an inductively charged stapled belt to physically transfer charge. The belt system operates in vacuum within the confines of the hollow insulating column and needs only energy to supply bearing losses and the work done against the electrostatic forces. A series of small holes located collinear on the concentric spheres create a region of uniform electrostatic field which accelerate negative particles to 1 MeV at the terminal. Here a small gas canal is used for stripping electrons from the particles, causing them to change sign from negative to positive. These positive particles are repelled from the terminal back to ground to give He^(++) particles with energies up to 3 MeV and H^+ of 2 MeV. Two types of ion sources would be provided with this device. The first, a simple Penning source, would produce H^- beams for proton-induced x-ray measurement. A second lithium exchange source would provide He^- for backscatter measurements

Transpolar arc observation after solar wind entry into the high-latitude magnetosphere

Recently, Cluster observations have revealed the presence of new regions of solar wind plasma entry at the high-latitude magnetospheric lobes tailward of the cusp region, mostly during periods of northward interplanetary magnetic field. In this study, observations from the Global Ultraviolet Imager (GUVI) experiment on board the TIMED spacecraft and Wideband Imaging Camera imager on board the IMAGE satellite are used to investigate a possible link between solar wind entry and the formation of transpolar arcs in the polar cap. We focus on a case when transpolar arc formation was observed twice right after the two solar wind entry events were detected by the Cluster spacecraft. In addition, GUVI and IMAGE observations show a simultaneous occurrence of auroral activity at low and high latitudes after the second entry event, possibly indicating a two-part structure of the continuous band of the transpolar arc

Argonne National Laboratory Reports

Report of the Argonne National Laboratory Chemical Engineering Division on fuel-cycle studies including pyro-chemical separation of plutonium and americium oxides from contaminated materials of construction such as steel, advanced solvent extraction techniques in the development of centrifugal contactors for use in Purex processes, and a review and evaluation of the encapsulation of high-level waste in a metal matrix

Complete Sequencing and Pan-Genomic Analysis of Lactobacillus delbrueckii subsp. bulgaricus Reveal Its Genetic Basis for Industrial Yogurt Production

Lactobacillus delbrueckii subsp. bulgaricus (Lb. bulgaricus) is an important species of Lactic Acid Bacteria (LAB) used for cheese and yogurt fermentation. The genome of Lb. bulgaricus 2038, an industrial strain mainly used for yogurt production, was completely sequenced and compared against the other two ATCC collection strains of the same subspecies. Specific physiological properties of strain 2038, such as lysine biosynthesis, formate production, aspartate-related carbon-skeleton intermediate metabolism, unique EPS synthesis and efficient DNA restriction/modification systems, are all different from those of the collection strains that might benefit the industrial production of yogurt. Other common features shared by Lb. bulgaricus strains, such as efficient protocooperation with Streptococcus thermophilus and lactate production as well as well-equipped stress tolerance mechanisms may account for it being selected originally for yogurt fermentation industry. Multiple lines of evidence suggested that Lb. bulgaricus 2038 was genetically closer to the common ancestor of the subspecies than the other two sequenced collection strains, probably due to a strict industrial maintenance process for strain 2038 that might have halted its genome decay and sustained a gene network suitable for large scale yogurt production

The Earth: Plasma Sources, Losses, and Transport Processes

This paper reviews the state of knowledge concerning the source of magnetospheric plasma at Earth. Source of plasma, its acceleration and transport throughout the system, its consequences on system dynamics, and its loss are all discussed. Both observational and modeling advances since the last time this subject was covered in detail (Hultqvist et al., Magnetospheric Plasma Sources and Losses, 1999) are addressed