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Simultaneous two hemisphere observations of the presence of polar patches in the nightside ionosphere

first_imgThe presence of polar patches as observed simultaneously in the same magnetic meridian of opposite nightside ionospheres by coherent and incoherent scatter radars are described. The patches appear to be related to variations either in the Bz or By component of the interplanetary magnetic field which cause transient merging on the dayside magnetopause. The passage and characteristics of polar patches as they traverse the polar cap into the nightside auroral oval are not significantly affected by the occurrence of small substroms. This study illustrates how the observations of polar patches in the nightside high-latitude ionosphere could be of great value in determining their formation process.last_img

Polarization of radio waves transmitted through Antarctic ice shelves

first_imgThe polarization behaviour of radar waves transmitted through two Antarctic ice shelves has been investigated using a step frequency radar with a centre frequency of 300 MHz and a bandwidth of 150 MHz. One site was on Brunt Ice Shelf at a site near Halley station, and 17 sites were oil George VI Ice Shelf near the southern ice front. Birefringence in the ice dominated the behaviour oil Brunt Ice Shelf, where the anisotropy in the effective permittivity was found to be about 0.14%. On George VI Ice Shelf, a highly anisotropic reflecting surface was the controlling feature, suggesting a fluted ice-shelf base formed by oceanographic currents.last_img

Metabolic demand, oxygen supply, and critical temperatures in the Antarctic bivalve Laternula elliptica

first_imgOxygen consumption ((M) over dot o(2)), heartbeat rate and form, and circulating hemolymph oxygen content were measured in relation to temperature in the large Antarctic infaunal bivalve Laternula elliptica. After elevations in temperature from 0degrees to 3degrees, 6degrees, and then 9degreesC, (M) over dot o(2) and heartbeat rate rose to new levels, whereas. maximum circulating hemolymph oxygen content fell. At 0degreesC, (M) over dot o(2) was 19.6 mumol O-2 h(-1) for a standard animal of 2-g tissue. ash-free dry mass, which equates to a 8.95-g tissue dry-mass or 58.4-g tissue wet-mass animal. Elevation of metabolism following temperature change had acute Q(10) values between 4.1 and 5, whereas acclimated figures declined from 3.4 (between 0degrees and 3degreesC) to 2.2 (3degrees-6degreesC) and 1.9 (6degrees-9degreesC). Heartbeat rate showed no acclimation following temperature elevations, with Q(10) values of 3.9, 3.2, and 4.3, respectively. Circulating hemolymph oxygen content declined from 0degrees to 3degrees and 6degreesC but stayed at a constant Po-2 (73-78 mmHg) and constant proportion (similar to50%) of the oxygen content of the ambient water. At 9degreesC, (M) over dot o(2) and heartbeat rate both peaked at values 3.3 times those. measured at 0degreesC, which may indicate aerobic scope in this species. After these peaks, both measures declined rapidly over the ensuing 5 d to the lowest measured in the study, and the bivalves began to die. Hemolymph oxygen content fell dramatically at 9degreesC to values between 2% and 12% of ambient water O-2 content and had a maximum Po-2 of around 20 mmHg. These data indicate an experimental upper lethal temperature of 9degreesC and a critical temperature, where a long-term switch to anaerobic metabolism probably occurs, of around 6degreesC for L. elliptica. Concurrent measures of mitochondrial function in the same species had indicated strong thermal sensitivity in proton leakage costs, and our data support the hypothesis that as temperature rises, mitochondrial maintenance costs rapidly outstrip oxygen supply mechanisms in cold stenothermal marine species.last_img read more

Behaviour of tracer diffusion in simple atmospheric boundary layer models

first_img1-D profiles and time series from an idealised atmospheric boundary layer model are presented, which show agreement with boundary layer measurements of polar NOx. Diffusion models are increasingly being used as the framework for studying tropospheric air chemistry dynamics. Models based on standard boundary layer diffusivity profiles have an intrinsic behaviour that is not necessarily intuitive, due to the variation of turbulent diffusivity with height. The simple model presented captures the essence of the evolution of a trace gas released at the surface, and thereby provides both a programming and a conceptual tool in the analysis of observed trace gas evolution. A time scale inherent in the model can be tuned by fitting model time series to observations. This scale is then applicable to the more physically simple but chemically complex zeroth order or box models of chemical interactions.last_img read more

Ocean tides in the Weddell Sea: New observations on the Filchner-Ronne and Larsen C ice shelves and model validation

first_imgOcean tides under the large Weddell Sea ice shelves are among the least well observed on Earth. Here we present new, spatially extensive observations of the vertical tidal motion of the Filchner-Ronne and Larsen C ice shelves using Global Positioning System (GPS) data spanning a few weeks to years. We pay particular attention to the major tidal constituents (M2, S2, O1, K1) as well as important GRACE aliasing periods (K2 and S1). We compare the estimated constituents with recent global and regional tide models and find that no single model is the most accurate across all constituents or ice shelves. The root-sum-square errors are 7-8 cm (CATS2008a and TPXO7.2) and 11-12 cm (GOT4.7 and FES2004) with the energetic M2 (RMSE = 4-8 cm) and S2 (4-5 cm) generally dominating these statistics. The FES2004 K1 is particularly inaccurate near the Larsen C Ice Shelf, with errors approaching 20 cm, meaning that GRACE Release 4 estimates of mass change in the northern Antarctic Peninsula will be biased. We find tidal energy at 3, 4, 5, 6 and, weakly, at 7 cycles per day at all of our sites. The largest amplitudes within these bands are at M4, MO3 and SP3 and approach 30 mm, although significant spatial variations exist. We show that they generally do not appear to originate in areas of reduced water column in ice shelf grounding zones. Comparing model estimates with our M4, MS4 and MN4 values shows that models do not accurately represent these terms.last_img read more

An improved model for tidally modulated grounding-line migration

first_imgUnderstanding grounding-line dynamics is necessary for predictions of long-term ice-sheetstability. However, despite growing observations of the tidal influence on grounding-line migration, thisshort-timescale migration is poorly understood, with most modeling attempts assuming beam theory tocalculate displacements. Here we present an improved model of tidal grounding-line migration thattreats migration as an elastic fracture problem, forced by the additional ocean water pressure from thetide. This new model predicts that the grounding line cannot be assumed to be in hydrostaticequilibrium and, furthermore, that migration is inherently asymmetric and nonlinear, with migrationdistances that are not proportional to the tidal load. Specifically, for constant surface slope, thegrounding line migrates upstream approximately ten times further as the tide rises from mean sea levelto high tide than it migrates downstream as the tide falls from mean sea level to low tide, and migrationdistances are substantially larger than simple flotation arguments suggest. Numerical tests also showthat the dependence of migration distance on elastic moduli and ice-sheet thickness are inconsistentwith predictions of beam theory for a range of realistic values. Finally, applying the new model toobservations in Antarctica results in new estimates of bed slopes, though these estimates remainuncertain due to imperfect knowledge of the relevant rheological parameters.last_img read more

Magnetic local time‐resolved examination of radiation belt dynamics during high speed solar wind speedtTriggered substorm clusters

first_imgParticle observations from low Earth orbiting satellites are used to undertake superposed epoch analysis around clusters of substorms, in order to investigate radiation belt dynamical responses to mild geomagnetic disturbances. Medium energy electrons and protons have drift periods long enough to discriminate between processes occurring at different MLT, such as magnetopause shadowing, plasma wave activity, and substorm injections. Analysis shows that magnetopause shadowing produces clear loss in proton and electron populations over a wide range of L‐shells, initially on the dayside, which interact with nightside substorm‐generated flux enhancements following charge‐dependent drift directions. Inner magnetospheric injections recently identified as an important source of 10’s to 100’s keV electrons at low L (L<3), occurring during similar solar wind‐driving conditions as recurrent substorms, show similar but more enhanced geomagnetic AU‐index signatures. Two‐fold increases in substorm occurrence at the time of the sudden particle enhancements at low L shells (SPELLS), suggests a common linkage.last_img read more

Confronting Arctic Troposphere, Clouds, and Surface Energy Budget Representations in Regional Climate Models With Observations

first_imgA coordinated regional climate model (RCM) evaluation and intercomparison project based on observations from a July–October 2014 trans‐Arctic Ocean field experiment (ACSE‐Arctic Clouds during Summer Experiment) is presented. Six state‐of‐the‐art RCMs were constrained with common reanalysis lateral boundary forcing and upper troposphere nudging techniques to explore how the RCMs represented the evolution of the surface energy budget (SEB) components and their relation to cloud properties. We find that the main reasons for the modeled differences in the SEB components are a direct consequence of the RCM treatment of cloud and cloud‐radiative interactions. The RCMs could be separated into groups by their overestimation or underestimation of cloud liquid. While radiative and turbulent heat flux errors were relatively large, they often invoke compensating errors. In addition, having the surface sea‐ice concentrations constrained by the reanalysis or satellite observations limited how errors in the modeled radiative fluxes could affect the SEB and ultimately the surface evolution and its coupling with lower tropospheric mixing and cloud properties. Many of these results are consistent with RCM biases reported in studies over a decade ago. One of the six models was a fully coupled ocean‐ice‐atmosphere model. Despite the biases in overestimating cloud liquid, and associated SEB errors due to too optically thick clouds, its simulations were useful in understanding how the fully coupled system is forced by, and responds to, the SEB evolution. Moving forward, we suggest that development of RCM studies need to consider the fully coupled climate system.last_img read more

SUU Football Visits No. 14/15 Montana State Saturday

first_img Brad James FacebookTwitterLinkedInEmailBOZEMAN, Mont.-Saturday, Southern Utah (2-7, 1-4 in Big Sky Conference play) heads northward in hopes of upsetting the No. 14 (The Associated Press poll)/No. 15 (AFCA Coaches poll) Montana State Bobcats (5-2, 2-2 in Big Sky play) at Bobcat Stadium.The Thunderbirds have had a rough season, but achieved highly last Saturday in downing the Idaho State Bengals 59-34 at Eccles Coliseum, earning their first Big Sky win of the season.SUU ranks 63rd nationally in scoring offense (26.6 points per game).Redshirt sophomore signal-caller Chris Helbig completes 64.7 percent of his passes on the season (17th nationally) for 2,284 yards (12th nationally), 13 touchdowns and 10 interceptions to pace the Thunderbirds. Helbig has also run for six scores on the season.Redshirt junior tailback James Felila (89 car, 337 yards, 2 TD’s) and sophomore running mate Thomas Duckett (51 car, 231 yards, 2 TD’s) are the Thunderbirds’ rushing leaders.Sophomore tailback Lance Lawson (67 rec, 634 yards, 3 TD’s) and freshman receiver Zach Nelson (13 rec, 200 yards, 3 TD’s) lead the Thunderbirds in scoring receptions. Senior receiver Carlos Baker (10 rec, 242 yards, TD) leads SUU in yards per reception (24.2 yards).Junior kicker Manny Berz has made 3 of his 5 field goals on the season with redshirt junior kicker/punter Kekoa Sasaoka having made 29 of his 30 PAT’s on the season.The Thunderbirds’ scoring defense continues to rank among the worst in the nation and is currently in 116th place (38.1 points per game).Sophomore defensive lineman Aaron Romero (4.5 sacks, forced fumble) remains SUU’s overall defensive leader.Redshirt freshman Carlton Johnson (3 interceptions) is the reigning Big Sky/ROOT Sports defensive player of the week after his pick-six in the aforementioned win against Idaho State last Saturday.Redshirt sophomore safety AJ Stanley, redshirt sophomore linebacker Quaid Murray, sophomore defensive end Francis Bemiy, redshirt senior safety Kyle Hannemann, in addition to Romero, each have a forced fumble on the season.The Bobcats come into Saturday’s game, the losers of two straight. Montana State has fallen to Sacramento State (21-34) and at North Dakota (12-16).Montana State ranks 42nd nationally (30.3 points per game) in scoring offense.Sophomore quarterback Tucker Rovig completes 57.3 percent of his passes on the season (75-131) for 833 yards,  7 touchdowns and 3 interceptions on the season for the Bobcats.The Bobcats rank 10th nationally in rushing offense (243.5 yards per game on the ground).Senior tailback Logan Jones (70 car, 483  yards, 5 TD’s) ranks 10th nationally with 6.8 yards per carry for Montana State. Other Bobcats to impress on the ground include senior receiver Travis Jonsen (34 rec, 384 yards, TD; 58 car, 339 yards, 5 TD’s, 5.8 yards per carry) and sophomore tailback Isaiah Ifanse (42 car, 270 yards, 6.4 yards per carry).Senior receiver Kevin Kassis leads the Bobcats in catches (36), yards (433) and scoring receptions (3).Senior kicker Tristan Bailey has made 7 of his 12 field goals on the season for the Bobcats and has made all 30 of his PAT’s.Montana State ranks 45th nationally in scoring defense (25.8 points per game), tied with Monmouth, North Carolina Central and Southern Illinois.Senior defensive end Bryce Sterk (9.5 sacks) is tied for fifth nationally in sacks with Sacramento State’s George Obinna.Junior defensive lineman Amandre Williams, senior cornerback JoJo Henderson (a Snow College product out of Salt Lake City), junior cornerback Tyrel Thomas, senior safety Jahque Alleyne and senior cornerback Damien Washington each have an interception apiece for the Bobcats.Junior linebacker Michael Jobman, junior defensive end Chase Benson, Henderson and Alleyne each have a forced fumble on the season for the Bobcats.The series is tied 3-3 all-time and 2-2 at Bozeman, Mont. Written by October 31, 2019 /Sports News – Local SUU Football Visits No. 14/15 Montana State Saturday Tags: Montana State Football/SUU Footballlast_img read more

SUU Men’s Basketball Returns To Action At Johnson City, Tenn.

first_img Written by November 21, 2019 /Sports News – Local SUU Men’s Basketball Returns To Action At Johnson City, Tenn. Tags: Charleston Southern Men’s Basketball/Delaware State Men’s Basketball/East Tennessee State Men’s Basketball/Maui Invitational/SUU Men’s Basketball FacebookTwitterLinkedInEmailJOHNSON CITY, Tenn.-Saturday and Sunday, Southern Utah men’s basketball (2-2) concludes its Maui on the Mainland tournament slate by facing the Charleston State Buccaneers (1-4) at Johnson City, Tenn. Saturday.Sunday, the Thunderbirds will face either Delaware State (0-5) or host school East Tennessee State (3-1).Presently, in his fourth season at the helm of the SUU program, head coach Todd Simon is 38-65 (.369) at Cedar City.The Thunderbirds score 78.3 points per game, ranking them 99th nationally in scoring offense.Junior guard John Knight III (13 points, 3.3 rebounds per game, a team-best 12 assists) is SUU’s statistical leader.Redshirt senior forward Dwayne Morgan (12.8 points, 5.3 rebounds per game), and redshirt senior guard/forward Cameron Oluyitan (10.3 points, 5.5 rebounds per game) are also stalwarts for the Thunderbirds. Morgan’s five blocked shots also lead SUU. Morgan and Oluyitan’s seven steals apiece lead the Thunderbirds on the season.Junior guard Dre Marin and redshirt junior guard Jakolby Long also score in double figures for SUU, averaging 10 points per game apiece.The Thunderbirds rank 239th nationally in scoring defense, surrendering 72 points per game. They are tied with Buffalo and NJIT in this category.In his 15th season at Charleston Southern, head coach Barclay Radebaugh is 194-242 (.445) as the Buccaneers’ head coach.Charleston Southern scores 60.4 points per game as they are tied for 323rd nationally in scoring offense with North Carolina-Central.Sophomore guard Dontrell Shuler (18.8 points, 2.5 rebounds per game, a team-best 15 assists) is the only Buccaneer to score on-average in double figures on the season.Junior guard Phlandrous Fleming Jr. (a team-best 6.8 rebounds per game and team bests in steals (8) and blocks (3).The Buccaneers are tied for 328th nationally in scoring defense, surrendering 81.8 points per game, with Cleveland State.The Thunderbirds lead the Buccaneers 1-0 all-time as they prevailed 91-79 over Charleston Southern December 31, 1988.Delaware State is coached by Eric Skeeters, who is 6-29 (.171) in his second season at the helm of the Hornets’ program.The Hornets score 64.8 points per game as they rank 266th nationally in scoring offense.Senior guard John Crosby (19.8 points, 4.4 rebounds per game), junior forward Ameer Bennett (12.4 points, a team-best 6.6 rebounds per game) and sophomore guard John Stansbury (11.2 points, 5.4 rebounds per game) all score on-average in double figures for Delaware State. Crosby and Stansbury each have six steals apiece to lead the Hornets in that category.Junior point guard Johquin “Pinky” Wiley has a team-best 18 assists to pace Delaware State.Delaware State surrenders 91.6 points per game, ranking them 347th nationally in scoring defense.Bennett, freshman guard-forward Omari Peek-Green and sophomore forward Ronald Lucas have two blocks apiece to lead the Hornets in this category.The East Tennessee State Buccaneers are coached by Steve Forbes, who is 103-40 (.720) in his fifth season at the helm.The Buccaneers score 73.8 points per game, ranking them 159th nationally in scoring offense as they are tied with Texas-El Paso in this category.Junior guard Bo Hodges (17 points, 6.8 rebounds, a team-best 9 blocks), senior guard Tray Boyd III (12.5 points per game) and redshirt junior guard Patrick Good (11.3 points per game) all score in double figures for the Buccaneers.Sophomore guard Daivien Williamson has a team-best 13 assists for East Tennessee State on the season.The Buccaneers surrender 64.5 points on the season, tying them for 126th nationally in scoring defense with California and Minnesota.Senior guard Isaiah Tisdale has a team-best eight steals on the season to pace the Buccaneers in that category. Brad Jameslast_img read more