Polarisation properties of Milky-Way-like galaxies

(Abridged) We study the polarisation properties, magnetic field strength, and synchrotron emission scale-height of Milky-Way-like galaxies in comparison with other spiral galaxies. We use our 3D-emission model of the Milky Way Galaxy for viewing the Milky Way from outside at various inclinations as spiral galaxies are observed. When seen edge-on the synchrotron emission from the Milky Way has an exponential scale-height of about 0.74 kpc, which is much smaller than the values obtained from previous models. We find that current analysis methods overestimate the scale-height of synchrotron emission of galaxies by about 10% at an inclination of 80 degree and about 40% at an inclination of 70 degree because of contamination from the disk. The observed RMs for face-on galaxies derived from high-frequency polarisation measurements approximate to the Faraday depths (FDs) when scaled by a factor of two. For edge-on galaxies, the observed RMs are indicative of the orientation of the large-scale magnetic field, but are not well related with the FDs. Assuming energy equipartition between the magnetic field and particles for the Milky Way results in an average magnetic-field strength, which is about two times larger than the intrinsic value for a K factor of 100. The number distribution of the integrated polarisation percentages of a large sample of unresolved Milky-Way-like galaxies peaks at about 4.2% at 4.8 GHz and at about 0.8% at 1.4GHz. Integrated polarisation angles rotated by 90 degree align very well with the position angles of the major axes, implying that unresolved galaxies do not have intrinsic RMs.Comment: 10 pages, 11 figures, accepted for publication in A&

Central-Pacific surface meteorology from the 2016 El Niño Rapid Response (ENRR) field campaign

During the early months of the 2015/2016 El Niño event, scientists led by the Earth System Research Laboratory's Physical Sciences Division conducted the National Oceanic and Atmospheric Administration's (NOAA's) El Niño Rapid Response (ENRR) field campaign. One component of ENRR involved in situ observations collected over the near-equatorial eastern–central Pacific Ocean. From 25 January to 28 March 2016, standard surface meteorology observations, including rainfall, were collected at Kiritimati Island (2.0° N, 157.4° E) in support of twice-daily radiosonde launches. From 16 February to 16 March 2016, continuous measurements of surface meteorology, sea surface temperature, and downwelling shortwave radiation were made by NOAA Ship Ronald H. Brown. These were largely done in support of the four to eight radiosondes launched each day as the ship travelled from Hawaii to TAO buoy locations along longitudes 140 and 125° W and then back to port in San Diego, California. The rapid nature of these remote field deployments led to some specific challenges in addition to those common to many surface data collection efforts. This paper documents the two deployments as well as the steps taken to evaluate and process the data. The results are two multi-week surface meteorology data products and one accompanying set of surface fluxes, all collected in the core of the eastern–central Pacific's extremely warm waters. These data sets, plus metadata, are archived at the NOAA's National Centers for Environmental Information (NCEI) and are free for public access: surface meteorology from Kiritimati Island (https://doi.org/10.7289/V51Z42H4); surface meteorology and some surface fluxes from NOAA Ship Ronald H. Brown (https://doi.org/10.7289/V5SF2T80; https://doi.org/10.7289/V58050VP)

Molecular scale contact line hydrodynamics of immiscible flows

From extensive molecular dynamics simulations on immiscible two-phase flows, we find the relative slipping between the fluids and the solid wall everywhere to follow the generalized Navier boundary condition, in which the amount of slipping is proportional to the sum of tangential viscous stress and the uncompensated Young stress. The latter arises from the deviation of the fluid-fluid interface from its static configuration. We give a continuum formulation of the immiscible flow hydrodynamics, comprising the generalized Navier boundary condition, the Navier-Stokes equation, and the Cahn-Hilliard interfacial free energy. Our hydrodynamic model yields interfacial and velocity profiles matching those from the molecular dynamics simulations at the molecular-scale vicinity of the contact line. In particular, the behavior at high capillary numbers, leading to the breakup of the fluid-fluid interface, is accurately predicted.Comment: 33 pages for text in preprint format, 10 pages for 10 figures with captions, content changed in this resubmissio

Propagation of cosmic-ray nucleons in the Galaxy

We describe a method for the numerical computation of the propagation of primary and secondary nucleons, primary electrons, and secondary positrons and electrons. Fragmentation and energy losses are computed using realistic distributions for the interstellar gas and radiation fields, and diffusive reacceleration is also incorporated. The models are adjusted to agree with the observed cosmic-ray B/C and 10Be/9Be ratios. Models with diffusion and convection do not account well for the observed energy dependence of B/C, while models with reacceleration reproduce this easily. The height of the halo propagation region is determined, using recent 10Be/9Be measurements, as >4 kpc for diffusion/convection models and 4-12 kpc for reacceleration models. For convection models we set an upper limit on the velocity gradient of dV/dz < 7 km/s/kpc. The radial distribution of cosmic-ray sources required is broader than current estimates of the SNR distribution for all halo sizes. Full details of the numerical method used to solve the cosmic-ray propagation equation are given.Comment: 15 pages including 23 ps-figures and 3 tables, latex2e, uses emulateapj.sty (ver. of 11 May 1998, enclosed), apjfonts.sty, timesfonts.sty. To be published in ApJ 1998, v.509 (December 10 issue). More details can be found at http://www.gamma.mpe-garching.mpg.de/~aws/aws.html Some references are correcte

Author Correction: Long-term field comparison of multiple low-cost particulate matter sensors in an outdoor urban environment

Correction to: Scientific Reports https://doi.org/10.1038/s41598-019-43716-3, published online 16 May 2019. This Article contains a typographical error in the Acknowledgements section. “Natural Environmental Research Council grant number [NE/L002531/1]” should read: “Natural Environment Research Council: NE/N012070/1”

Central-Pacific surface meteorology from the 2016 El Nino Rapid Response (ENRR) field campaign

During the early months of the 2015/2016 El Niño event, scientists led by the Earth System Research Laboratory's Physical Sciences Division conducted the National Oceanic and Atmospheric Administration's (NOAA's) El Niño Rapid Response (ENRR) field campaign. One component of ENRR involved in situ observations collected over the near-equatorial eastern–central Pacific Ocean. From 25 January to 28 March 2016, standard surface meteorology observations, including rainfall, were collected at Kiritimati Island (2.0° N, 157.4° E) in support of twice-daily radiosonde launches. From 16 February to 16 March 2016, continuous measurements of surface meteorology, sea surface temperature, and downwelling shortwave radiation were made by NOAA Ship Ronald H. Brown. These were largely done in support of the four to eight radiosondes launched each day as the ship travelled from Hawaii to TAO buoy locations along longitudes 140 and 125° W and then back to port in San Diego, California. The rapid nature of these remote field deployments led to some specific challenges in addition to those common to many surface data collection efforts. This paper documents the two deployments as well as the steps taken to evaluate and process the data. The results are two multi-week surface meteorology data products and one accompanying set of surface fluxes, all collected in the core of the eastern–central Pacific's extremely warm waters. These data sets, plus metadata, are archived at the NOAA's National Centers for Environmental Information (NCEI) and are free for public access: surface meteorology from Kiritimati Island (https://doi.org/10.7289/V51Z42H4); surface meteorology and some surface fluxes from NOAA Ship Ronald H. Brown (https://doi.org/10.7289/V5SF2T80; https://doi.org/10.7289/V58050VP)

Third-Party Strategy under Plurality Rule: The British Liberal Democrats and the New Zealand Social Credit Party

This paper examines the strategic options facing small centrist third parties in two-party parliamentary systems operating under the single-member district plurality (SMDP) electoral system. It uses a spatial model to show that centrist third parties are better off targeting the 'safe' districts of a major party rather than marginal districts. Furthermore, it is optimal to target one party's districts, not both, to benefit from tactical and protest voting. The paper also questions the implicit conclusion of the median-legislator theorem that pivotality-seeking is the best strategy for a third party, at least under SMDP, because that would usurp voters' ability to select the executive directly, a key feature of two-partism. Finally, the paper shows that third parties can damage themselves if they 'flip' from opposition to one major party to support for it. Evidence is provided for the British Liberal Democrats and New Zealand?s historic Social Credit Party

Ship- and island-based soundings from the 2016 El Niño Rapid Response (ENRR) field campaign

As the 2015/2016 El Niño was gathering strength in late 2015, scientists at the Earth System Research Laboratory's Physical Sciences Division proposed and led the implementation of the National Oceanic and Atmospheric Administration's (NOAA's) El Niño Rapid Response (ENRR) Field Campaign. ENRR observations included wind and thermodynamic profiles of the atmosphere over the near-equatorial eastern central Pacific Ocean, many of which were collected from two field sites and transmitted in near-real time for inclusion in global forecasting models. From 26 January to 28 March 2016, twice-daily rawinsonde observations were made from Kiritimati (pronounced Christmas) Island (2.0° N, 157.4° E; call sign CXENRR). From 16 February to 16 March 2016, three to eight radiosondes were launched each day from NOAA Ship Ronald H. Brown (allocated call sign WTEC) as it travelled southeast from Hawaii to service Tropical Atmosphere Ocean (TAO) buoys along longitudes 140 and 125° W and then north to San Diego, California. Both the rapid and remote nature of these deployments created particular difficulties in collecting and disseminating the soundings; these are described together with the methods used to reprocess the data after the field campaign finished. The reprocessed and lightly quality-controlled data have been put into an easy-to-read text format, qualifying them to be termed Level 2 soundings. They are archived and freely available for public access at NOAA's National Centers for Environmental Information (NCEI) in the form of two separate data sets: one consisting of 125 soundings from Kiritimati (https://doi.org/10.7289/V55Q4T5K), the other of 193 soundings from NOAA Ship Ronald H. Brown (https://doi.org/10.7289/V5X63K15). Of the Kiritimati soundings, 94 % reached the tropopause and 88 % reached 40 hPa, while 89 % of the ship's soundings reached the tropopause and 87 % reached 40 hPa. The soundings captured the repeated advance and retreat of the Intertropical Convergence Zone (ITCZ) at Kiritimati, a variety of marine tropospheric environments encountered by the ship, and lower-stratospheric features of the 2015–2016 QBO (quasi-biennial oscillation), all providing a rich view of the local atmosphere's response to the eastern central Pacific's extremely warm waters during the 2015/16 El Niño