Magnetic structure of our Galaxy: A review of observations

The magnetic structure in the Galactic disk, the Galactic center and the Galactic halo can be delineated more clearly than ever before. In the Galactic disk, the magnetic structure has been revealed by starlight polarization within 2 or 3 kpc of the Solar vicinity, by the distribution of the Zeeman splitting of OH masers in two or three nearby spiral arms, and by pulsar dispersion measures and rotation measures in nearly half of the disk. The polarized thermal dust emission of clouds at infrared, mm and submm wavelengths and the diffuse synchrotron emission are also related to the large-scale magnetic field in the disk. The rotation measures of extragalactic radio sources at low Galactic latitudes can be modeled by electron distributions and large-scale magnetic fields. The statistical properties of the magnetized interstellar medium at various scales have been studied using rotation measure data and polarization data. In the Galactic center, the non-thermal filaments indicate poloidal fields. There is no consensus on the field strength, maybe mG, maybe tens of uG. The polarized dust emission and much enhanced rotation measures of background radio sources are probably related to toroidal fields. In the Galactic halo, the antisymmetric RM sky reveals large-scale toroidal fields with reversed directions above and below the Galactic plane. Magnetic fields from all parts of our Galaxy are connected to form a global field structure. More observations are needed to explore the untouched regions and delineate how fields in different parts are connected.Comment: 10+1 pages. Invited Review for IAU Symp.259: Cosmic Magnetic Fields: From Planets, to Stars and Galaxies (Tenerife, Spain. Nov.3-7, 2009). K.G. Strassmeier, A.G. Kosovichev & J.E. Beckman (eds.

Ignition and combustion characteristics of hydrotreated pyrolysis oil in a combustion research unit

Biomass-derived fuels are promising in reducing life-cycle CO2 emissions and achieving the goal of sustainable mobility in the future. This work investigates the ignition behavior and combustion process of hydrotreated pyrolysis oil (HPO) derived from various biomass resources. They are tested in a combustion research unit based on constant volume combustion technology, which imitates the ignition behavior in compression ignition engines. Various conditions are tested and HPO are benchmarked with commericially avalable biofuels and fossile fuels: hydrotreated vegetable oil (HVO) and fatty acid methyl ester (FAME), diesel, and marine gas oil. The results showed that the igntiion delay time follows an order of folloing: HPO &gt; diesel-like fuels &gt; HVO. Both the biomass type and after-treatment have a small influence on the ignition delay of HPO. Two combustion regimes are observed at different chamber temperature range. It also revealed that blending HPO into HVO can extend the ignition delay of HVO. And ignition delay of HVO/HPO increases as the HPO blend ratio increases. At 75 vol% HPO blend ratio, the HPO/HVO blend shows identical ignition and combustion behavior as diesel. In addition, the viscosity of HPO/HVO blends and diesel are also quite similar. The results indicated the possibility of using 100% bio-fuel in a modern marine engine to provide power to future mobility.</p