Io plasma torus and the source of jovian narrow-band kilometric radiation

first_imgNarrow-band jovian kilometric radiation (nKOM) is distinguishable from broad-band jovian kilometric radiation (bKOM), both discovered by the Voyager spacecraft1–3, by its generally lower intensity, its more restricted range of centre frequency, its narrower bandwidth, and its temporally less sporadic nature4. When observed at northern and southern magnetic latitudes nKOM polarization was predominantly left-handed and right-handed respectively, opposite to bKOM4,5. At nearly the same longitude on consecutive jovian rotations nKOM sometimes lagged the magnetic field rotation4 by 3–5%; no such lag was detected for bKOM6,7. It was proposed that bKOM is produced within ˜2° of the magnetic equator in the outer lo plasma torus by conversion of electrostatic upper hybrid (ESUH) waves to ordinary (O) mode electromagnetic radiation via a radio window8,9. Here we show that nKOM seems to be produced by the same conversion process, also operating in the lo torus, but at latitudes ≥8°. The difference in latitude for nKOM and bKOM sources stems from the condition required for mode conversion that the plasma density gradient should be normal to the magnetic field vector. The difference in these locations allows an explanation of most of the similarities and differences between the two radiations.last_img read more

Stratigraphy and age of the Lower Cretaceous Pedersen Formation, northern Antarctic Peninsula

first_imgThe Pedersen Formation includes conglomerate-dominated successions exposed on Pedersen Nunatak (142 m thick) and southern Sobral Peninsula (750–1000 m thick). As re-defined here, it also includes mudstone and sandstone in tectonic contact with Nordenskjöld Formation strata on a nunatak north of the Sobral Peninsula conglomerate outcrops. 40Ar/39Ar ages and palynological data indicate an early Aptian age for the lower part of the formation on Sobral Peninsula. The Pedersen Nunatak strata have yielded conflicting age determinations, although an Early Cretaceous age seems likely. The Sobral Peninsula conglomerates are lithologically similar to, and possibly coeval with, basal Gustav Group strata (Lagrelius Point Formation) on James Ross Island. Although further field sampling is required to resolve the age of the Pedersen Nunatak strata, on present evidence the Pedersen Formation appears to form part of the same tectono-stratigraphic unit as the lower part of the Gustav Group, and we therefore propose that it be included in that group.last_img read more

Copepod hatching success in marine ecosystems with high diatom concentrations

first_imgDiatoms dominate spring bloom phytoplankton assemblages in temperate waters and coastal upwelling regions of the global ocean. Copepods usually dominate the zooplankton in these regions and are the prey of many larval fish species. Recent laboratory studies suggest that diatoms may have a deleterious effect on the success of copepod egg hatching(1-4). These findings challenge the classical view of marine food-web energy flow from diatoms to fish by means of copepods(5-7). Egg mortality is an important factor in copepod population dynamics(8), thus, if diatoms have a deleterious in situ effect, paradoxically, high diatom abundance could limit secondary production. Therefore, the current understanding of energy transfer from primary production to fisheries in some of the most productive and economically important marine ecosystems(9) may be seriously flawed(1,10). Here we present in situ estimates of copepod egg hatching success from twelve globally distributed areas, where diatoms dominate the phytoplankton assemblage. We did not observe a negative relationship between copepod egg hatching success and either diatom biomass or dominance in the microplankton in any of these regions. The classical model for diatom-dominated system remains valid.last_img read more

A simple method to reduce discharge of sewage microorganisms from an Antarctic research station

first_imgThe majority of coastal Antarctic stations release untreated sewage into the near-shore marine environment. This study examined bacterial reproduction within the temporary sewage-holding tanks of Rothera Research Station (Adelaide Island, Antarctic Peninsula) and monitored sewage pollution in the local marine environment. By continuously flushing the sewage-holding tanks with cold seawater we inhibited microbial reproduction and decreased the numbers of bacteria subsequently released into the sea by >90%. The widespread use of this simplemethod could significantly reduce the numbers of faecal coliform and other non-native microorganisms introduced into the Antarctic marine environmentlast_img read more

Numerical investigation of the effects of temporal variations in basal lubrication on englacial strain-rate distribution

first_imgThe effects of spatial and temporal variations in basal lubrication on the englacial strain rate and surface velocity distribution are investigated with a numerical ice-flow model. General aspects of the solutions are compared to measurements made on Lauteraargletscher, Switzerland, in 2001, that showed diurnal fluctuations in both surface velocity and englacial vertical strain. We find that spatial gradients in basal lubrication can set up variations in the deviatoric stress field that increases with distance to the bed and has a maximum value near the glacier surface. This stress field produces a significant strain rate near the surface. The temporal evolution of a slippery zone is identified as a possible cause of the observed diurnal variations in the vertical strain rate. Although general aspects of the measurements can be explained in this way, the calculated vertical strain rates are too small, suggesting that the modeled effective viscosity values using Glen’s flow law are too large near the surface.last_img read more

Multicolony tracking reveals potential threats to little auks wintering in the North Atlantic from marine pollution and shrinking sea ice cover

first_imgAim Extensive development of human activities in combination with ocean warming is rapidly modifying marine habitats in the Arctic and North Atlantic regions. To understand the potential impacts on marine biodiversity, there is an urgent need to determine distributions and habitat preferences of potentially vulnerable species and to identify sensitive hotspots that might require particular protection. Our aims were to track one of the most abundant seabirds of the world, the little auk (Alle alle), to provide a large, meta-population scale overview of its non-breeding distribution and to document potential threats to this species from human activities and other environmental changes. Location Arctic North Atlantic. Methods Using light-level geolocators, we investigated the 2010/11 non-breeding distribution of 65 little auks from four major colonies distributed throughout the Arctic North Atlantic. Bird distribution during the moulting, wintering and pre-breeding periods was compared with (1) the extent of the marginal ice zone and (2) the areas covered by the main shipping lanes and oil and gas activity licences. Results We identify several hotspots for this species, including two key areas located in the Greenland Sea and off Newfoundland. Crucially, we show that some of these hotspots overlap extensively with areas of intensive human activities, including oil and gas extraction and shipping. As little auks, which spend the major part of their time on the sea surface, are extremely vulnerable to marine pollution, our results emphasize the risk associated with the projected expansion of these activities. Main conclusions We conclude that management of further human enterprises in the Arctic needs to be based on more thorough risk assessment, requiring a substantial improvement in our knowledge of the distribution of sensitive species.last_img read more

The Southern Ocean in the Coupled Model Intercomparison Project phase 5

first_imgThe Southern Ocean is an important part of the global climate system, but its complex coupled nature makes both its present state and its response to projected future climate forcing difficult to model. Clear trends in wind, sea-ice extent and ocean properties emerged from multi-model intercomparison in the Coupled Model Intercomparison Project phase 3 (CMIP3). Here, we review recent analyses of the historical and projected wind, sea ice, circulation and bulk properties of the Southern Ocean in the updated Coupled Model Intercomparison Project phase 5 (CMIP5) ensemble. Improvements to the models include higher resolutions, more complex and better-tuned parametrizations of ocean mixing, and improved biogeochemical cycles and atmospheric chemistry. CMIP5 largely reproduces the findings of CMIP3, but with smaller inter-model spreads and biases. By the end of the twenty-first century, mid-latitude wind stresses increase and shift polewards. All water masses warm, and intermediate waters freshen, while bottom waters increase in salinity. Surface mixed layers shallow, warm and freshen, whereas sea ice decreases. The upper overturning circulation intensifies, whereas bottom water formation is reduced. Significant disagreement exists between models for the response of the Antarctic Circumpolar Current strength, for reasons that are as yet unclear.last_img read more

The 13th and 14th Workshops on Antarctic Meteorology and Climate

first_imgIn July 2018, the Antarctic community came together to meet at the 13th Workshop on Antarctic Meteorology and Cli-mate (WAMC) in Madison, Wisconsin, USA (Fig. 1); and in the following year in June 2019, the 14th WAMC was held inCharleston, South Carolina, USA (Fig. 2). With a growing history, the WAMC addresses the topics of Antarctic meteoro-logy and climate (Kameda et al., 2008; Colwell et al., 2016; Lazzara et al., 2018) as well as weather-related issues of scientif-ic and operational support. The workshops bring together researchers, operational forecasters, numerical modelers, observa-tional specialists, and students. The themes of both workshops included Antarctic meteorological observations, Antarctic at-mospheric numerical modeling, Antarctic meteorological and climate research, and Antarctic weather forecasting and opera-tional services. The 2018 and 2019 WAMC were both followed by a one-day focus on the Year of Polar Prediction-South-ern Hemisphere (YOPP-SH), when preparations and follow-up discussions were made with regard to the YOPP Special Ob-serving Period from 16 November 2018 to 15 February 2019.last_img read more

UVU and Weber State Softball To Meet in Postseason Tournament

first_img Written by Tags: Las Vegas/Nevada/UC Riverside/UNLV/UVU Softball/Weber State Softball FacebookTwitterLinkedInEmailLAS VEGAS-Monday, Utah Valley and Weber State softball were invited to the National Invitational Softball Championships after missing out on the NCAA Tournament Sunday night.Incidentally, in the Wednesday tournament opener, in the Las Vegas regional, the Wolverines and Wildcats will square off against each other.This is the second time the Wolverines’ softball program has played in a postseason tournament in program history.This regional will run from May 16-18 at Eller Media Softball Stadium, UNLV’s softball stadium.The Wildcats are in the NISC for the second consecutive year and are coming off the heels of a deep run in this tournament.In 2017, Weber State hosted a regional and made it all the way to the championship round at Liberty, Va.The winner of the Wildcats-Wolverines tilt will play host UNLV later that evening at 7:00 pm MDT. Also in this pod are the UC Riverside Highlanders of the Big West Conference and the Nevada Wolf Pack of the Mountain West.The loser of the UVU-Weber State game will play Thursday at 1:00 pm MDT against the loser of the UC Riverside-Nevada game.The host Rebels are one of Nevada’s Mountain West rivals. May 14, 2018 /Sports News – Local UVU and Weber State Softball To Meet in Postseason Tournament Brad Jameslast_img read more

Utah Men’s Basketball Hosts USC Thursday

first_imgSenior guard Sedrick Barefield (16.8 points per game), freshman forward Timmy Allen (11.7 points, 5.1 rebounds per game) and sophomore forward Donnie Tillman (10.2 points, 5.4 rebounds per game) all lead the Utes. The Utes score 75.5 points per game and surrender 74.6 points per contest. The Utes currently find themselves third in the Pac-12 standings. If the Pac-12 tournament were to start today, Utah would be the #4 seed and have a first-round bye. Written by The Trojans are the third-highest scoring team in the Pac-12 (76.7 points per game) and surrender 72.6 points per game. March 4, 2019 /Sports News – Local Utah Men’s Basketball Hosts USC Thursday Senior forward Bennie Boatwright (18.5 points, 6.7 rebounds per game), junifor forward Nick Rakocevic (14.8 points, 9.3 rebounds per game) and junior guard Jonah Mathews (12.6 points per game) all lead the Trojans. Tags: Bennie Boatwright/Donnie Tillman/Nick Rakocevic/Sedrick Barefield/Timmy Allen/USC Trojans/Utah Men’s Basketball FacebookTwitterLinkedInEmailSALT LAKE CITY-Thursday, the Utah men’s basketball squad (15-13, 9-7 in Pac-12 play) commences its last homestand of the regular season by hosting the USC Trojans (15-14, 8-8 in conference play). The Utes lead the Trojans 23-19 all-time and Utah is 12-6 all-time at Salt Lake City in the series. Utah’s regular season concludes Saturday at home against UCLA. Brad Jameslast_img read more