Modelling the ionospheric and plasmaspheric plasma

1989 ◽  
Vol 328 (1598) ◽  
pp. 255-270 ◽  
Keyword(s):  
Electric Fields ◽  
High Latitude ◽  
Thermal Plasma ◽  
Topside Ionosphere ◽  
Neutral Atmosphere ◽  
High Latitudes ◽  
Polar Wind ◽  
Low Latitude ◽  
Flux Tubes ◽  
Thermospheric Winds

Under magnetically quiet conditions, the outer plasmasphere is the equatorw ard boundary of the region in which high-latitude processes, such as convection, significantly affect the ionosphere. The low-latitude side of the ionospheric midlatitude trough is located in the plasmasphere. The behaviour of the nightside trough is influenced by field-aligned flows of plasma, as well as by convection drifts, thermospheric winds and particle precipitation. The modelling of field-aligned flow of thermal plasma at high latitudes (the polar wind) still presents problems. The composition of the background neutral atmosphere plays a role in causing the occasional dominance of He+ in the topside ionosphere. Penetration of magnetospheric electric fields into the outer plasmasphere can influence the rate of refilling of the upper reaches of the flux tubes.

scholarly journals Simultaneous high- and low-latitude reconnection: ESR and DMSP observations

2002 ◽  
Vol 20 (9) ◽  
pp. 1311-1320 ◽  
Author(s):  
F. Pitout ◽  
P. T. Newell ◽  
S. C. Buchert
Keyword(s):  
High Latitude ◽  
Time Interval ◽  
High Latitudes ◽  
Polar Ionosphere ◽  
Plasma Convection ◽  
Low Latitude ◽  
Svalbard Archipelago ◽  
Cusp Region ◽  
Ionosphere Plasma ◽  
Particle Measurement

Abstract. We present EISCAT Svalbard Radar and DMSP observations of a double cusp during an interval of predominantly northward IMF on 26 November 2000. In the cusp region, the ESR dish, pointing northward, recorded sun-ward ionospheric flow at high latitudes (above 82° GL), indicating reconnection occuring in the magnetospheric lobe. Meanwhile, the same dish also recorded bursts of poleward flow, indicative of bursty reconnection at the subsolar magnetopause. Within this time interval, the DMSP F13 satellite passed in the close vicinity of the Svalbard archipelago. The particle measurement on board exhibited a double cusp structure in which two oppositely oriented ion dispersions are recorded. We interpret this set of data in terms of simultaneous merging at low- and high-latitude magnetopause. We discuss the conditions for which such simultaneous high-latitude and low-latitude reconnection can be anticipated. We also discuss the consequences of the presence of two X-lines in the dayside polar ionosphere.Key words. Magnetospheric physics (solar wind-magnetosphere interactions) – Ionosphere (polar ionosphere; plasma convection)

ELECTRIC FIELDS AT HIGH LATITUDES IN THE TOPSIDE IONOSPHERE NEAR THE DAWN-DUSK MERIDIAN

1979 ◽  
pp. 343-346 ◽  
Author(s):  
W.J. Burke ◽  
R.C. Sagalyn ◽  
M. Smiddy ◽  
M.C. Kelley ◽  
S.T. Lai
Keyword(s):  
Electric Fields ◽  
Topside Ionosphere ◽  
High Latitudes

scholarly journals An Interhemispheric Four-Box Model of the Meridional Overturning Circulation

2011 ◽  
Vol 41 (3) ◽  
pp. 516-530 ◽  
Author(s):  
Peter H. Stone ◽  
Yuriy P. Krasovskiy
Keyword(s):  
High Latitude ◽  
General Circulation ◽  
Circulation Model ◽  
Meridional Overturning Circulation ◽  
High Latitudes ◽  
Stable States ◽  
Low Latitude ◽  
Overturning Circulation ◽  
High Latitude Region ◽  
Meridional Overturning

Abstract The authors introduce a four-box interhemispheric model of the meridional overturning circulation. A single box represents high latitudes in each hemisphere, and in contrast to earlier interhemispheric box models, low latitudes are represented by two boxes—a surface box and a deep box—separated by a thermocline in which a balance is assumed between vertical advection and vertical diffusion. The behavior of the system is analyzed with two different closure assumptions for how the low-latitude upwelling depends on the density contrast between the surface and deep low-latitude boxes. The first is based on the conventional assumption that the diffusivity is a constant, and the second on the assumption that the energy input to the mixing is constant. There are three different stable equilibrium states that are closely analogous to the three found by Bryan in a single-basin interhemispheric ocean general circulation model. One is quasi-symmetric with downwelling in high latitudes of both hemispheres, and two are asymmetric solutions, with downwelling confined to high latitudes in one or the other of the two hemispheres. The quasi-symmetric solution becomes linearly unstable for strong global hydrological forcing, while the two asymmetric solutions do not. The qualitative nature of the solutions is generally similar for both the closure assumptions, in contrast to the solutions in hemispheric models. In particular, all the stable states can be destabilized by finite amplitude perturbations in the salinity or the hydrological forcing, and transitions are possible between any two states. For example, if the system is in an asymmetric state, and the moisture flux into the high-latitude region of downwelling is slowly increased, for both closure assumptions the high-latitude downwelling decreases until a critical forcing is reached where the system switches to the asymmetric state with downwelling in the opposite hemisphere. By contrast, in hemispheric models with the energy constraint, the downwelling increases and there is no loss of stability.

Behavior of ionized plasma in the high latitude topside ionosphere: The polar wind

1987 ◽  
Vol 35 (6) ◽  
pp. 703-714 ◽  
Author(s):  
Supriya B. Ganguli ◽  
H.G. Mitchell ◽  
P.J. Palmadesso
Keyword(s):  
High Latitude ◽  
Topside Ionosphere ◽  
Polar Wind

scholarly journals Distributions of Arctic and Northwest Atlantic killer whales inferred from oxygen isotopes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Cory J. D. Matthews ◽  
Fred J. Longstaffe ◽  
Jack W. Lawson ◽  
Steven H. Ferguson
Keyword(s):  
Oxygen Isotopes ◽  
North Atlantic ◽  
High Latitude ◽  
Newfoundland And Labrador ◽  
Killer Whales ◽  
Low Latitude ◽  
Northwest Atlantic ◽  
Oxygen And Carbon Isotope ◽  
Stable Oxygen ◽  
Morphological Differences

AbstractKiller whales (Orcinus orca) are distributed widely in all oceans, although they are most common in coastal waters of temperate and high-latitude regions. The species’ distribution has not been fully described in the northwest Atlantic (NWA), where killer whales move into seasonally ice-free waters of the eastern Canadian Arctic (ECA) and occur year-round off the coast of Newfoundland and Labrador farther south. We measured stable oxygen and carbon isotope ratios in dentine phosphate (δ18OP) and structural carbonate (δ18OSC, δ13CSC) of whole teeth and annual growth layers from killer whales that stranded in the ECA (n = 11) and NWA (n = 7). Source δ18O of marine water (δ18Omarine) at location of origin was estimated from dentine δ18OPvalues, and then compared with predicted isoscape values to assign individual distributions. Dentine δ18OPvalues were also assessed against those of other known-origin North Atlantic odontocetes for spatial reference. Most ECA and NWA killer whales had mean δ18OPand estimated δ18Omarinevalues consistent with18O-depleted, high-latitude waters north of the Gulf Stream, above which a marked decrease in baseline δ18O values occurs. Several individuals, however, had relatively high values that reflected origins in18O-enriched, low-latitude waters below this boundary. Within-tooth δ18OSCranges on the order of 1–2‰ indicated interannual variation in distribution. Different distributions inferred from oxygen isotopes suggest there is not a single killer whale population distributed across the northwest Atlantic, and corroborate dietary and morphological differences of purported ecotypes in the region.

High Latitude Dust: contemporary emissions and geomorphic interactions

2021 ◽  
Author(s):  
Joanna Bullard
Keyword(s):  
Remote Sensing ◽  
Environmental Change ◽  
High Latitude ◽  
Cold Climate ◽  
Sediment Supply ◽  
Future Research ◽  
Similar Proportion ◽  
High Latitudes ◽  
Dust Emissions ◽  
Dust Sources

<div> <p>The world’s largest contemporary dust sources are in low-lying, hot, arid regions, however the processes of dust production and emission also operate in cold climate regions at high latitudes and altitudes.  This lecture focuses on contemporary dust emissions originating from the high latitudes (≥50°N and ≥40°S) and explores three themes before setting out an integrated agenda for future research.  The first theme considers how much dust originates from the high latitudes and methods for determining this.  Estimates from field studies, remote sensing and modelling all suggest around 5% of contemporary global dust emissions originate in the high latitudes, a similar proportion to that from the USA (excluding Alaska) or Australia.  This estimate is a proportion of a highly uncertain figure as quantification of dust emissions from Eurasian high latitudes is limited, and the contribution of local and regional emissions (from any latitude) to the global total is thought to be considerably under-estimated.  Emissions are particularly likely to be under-estimated where dust sources are topographically constrained, and where cold climates reduce vertical mixing of dust plumes restricting the altitudes to which the dust can rise, because both these characteristics present particular challenges for modelling and remote sensing approaches. The second theme considers the drivers of contemporary high latitude dust emissions that reflect complex interactions among sediment supply, sediment availability and transport capacity across different geomorphic sub-systems.  These interactions determine the magnitude, frequency and timing of dust emissions at a range of time scales (diurnal, seasonal, decadal) but both the drivers and response can be nonlinear and hard to predict.  The third and final theme explores the importance of high latitude dust cycling for facilitating cross-boundary material fluxes and its impact in the atmosphere, cryosphere, and terrestrial and marine ecosystems.  This is influenced not only by the quantity and timing of dust emissions but also by dust properties such as particle-size and geochemistry.  Landscape sensitivity, spatial environmental transitions and temporal environmental change are highlighted for their importance in determining how the interactions among drivers and cycles are likely to change in response to future environmental change.</p> </div>

Fossil flower of Staphylea L. from the Miocene amber of Mexico: New evidence of the Boreotropical Flora in low-latitude North America

2017 ◽  
Vol 108 (4) ◽  
pp. 471-478 ◽  
Author(s):  
Ana L. Hernández-Damián ◽  
Sergio R. S. Cevallos-Ferriz ◽  
Alma R. Huerta-Vergara
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
Fossil Record ◽  
First Record ◽  
High Latitudes ◽  
Low Latitude ◽  
Southern Mexico ◽  
Apparent Lack ◽  
History Of ◽  
New Evidence

ABSTRACTA new flower preserved in amber in sediments of Simojovel de Allende, México, is identified as an extinct member of Staphyleaceae, a family of angiosperms consisting of only three genera (Staphylea, Turpinia and Euscaphis), which has a large and abundant fossil record and is today distributed over the Northern Hemisphere. Staphylea ochoterenae sp. nov. is the first record of a flower for this group, which is small, pedicelled, pentamer, bisexual, with sepals and petals with similar size, dorsifixed anthers and superior ovary. Furthermore, the presence of stamens with pubescent filaments allows close comparison with extant flowers of Staphylea bulmada and S. forresti, species currently growing in Asia. However, their different number of style (one vs. three) and the apparent lack of a floral disc distinguish them from S. ochoterenae. The presence of Staphyleaceae in southern Mexico ca. 23 to 15My ago is evidence of the long history of integration of vegetation in low-latitude North America, in which some lineages, such as Staphylea, could move southwards from high latitudes of the Northern Hemisphere, as part of the Boreotropical Flora. In Mexico it grew in association with tropical elements, as suggested by the fossil record of the area.

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