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Sample records for 2510p dell latitude

  1. The power of virtual integration: an interview with Dell Computer's Michael Dell. Interview by Joan Magretta.

    PubMed

    Dell, M

    1998-01-01

    Michael Dell started his computer company in 1984 with a simple business insight. He could bypass the dealer channel through which personal computers were then being sold and sell directly to customers, building products to order. Dell's direct model eliminated the dealer's markup and the risks associated with carrying large inventories of finished goods. In this interview, Michael Dell provides a detailed description of how his company is pushing that business model one step further, toward what he calls virtual integration. Dell is using technology and information to blur the traditional boundaries in the value chain between suppliers, manufacturers, and customers. The individual pieces of Dell's strategy--customer focus, supplier partnerships, mass customization, just-in-time manufacturing--may be all be familiar. But Michael Dell's business insight into how to combine them is highly innovative. Direct relationships with customers create valuable information, which in turn allows the company to coordinate its entire value chain back through manufacturing to product design. Dell describes how his company has come to achieve this tight coordination without the "drag effect" of ownership. Dell reaps the advantages of being vertically integrated without incurring the costs, all the while achieving the focus, agility, and speed of a virtual organization. As envisioned by Michael Dell, virtual integration may well become a new organizational model for the information age. PMID:10177868

  2. Streaking into Middle School Science: The Dell Streak Pilot Project

    ERIC Educational Resources Information Center

    Austin, Susan Eudy

    2012-01-01

    A case study is conducted implementing the Dell Streak seven-inch android device into eighth grade science classes of one teacher in a rural middle school in the Piedmont region of North Carolina. The purpose of the study is to determine if the use of the Dell Streaks would increase student achievement on standardized subject testing, if the…

  3. 75 FR 28657 - Dell Products LP-Parmer North Location, a Subsidiary of Dell, Inc., Including On-Site Leased...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-21

    ... in the Federal Register on March 5, 2010 (75 FR 10321). The workers are engaged in employment related... Capital, MagRabbit, Manpower and Spherion Corporation; Round Rock, TX; Dell Products LP--Parmer North One... Capital, MagRabbit, Manpower, and Spherion Corporation, Round Rock, Texas (TA-W-72,150) and Dell...

  4. Liven up Your Student Dramatics with Commedia dell' Arte.

    ERIC Educational Resources Information Center

    Potter, Jonathan

    1980-01-01

    Suggests using the ancient Commedia dell' Arte technique of establishing characters and a plot and then allowing the actors to create their own play. Indicates that this improves student performances even in more traditional plays. (TJ)

  5. High Latitude Polygons

    NASA Technical Reports Server (NTRS)

    2005-01-01

    26 September 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows polygonal patterned ground on a south high-latitude plain. The outlines of the polygons, like the craters and hills in this region, are somewhat enhanced by the presence of bright frost left over from the previous winter. On Earth, polygons at high latitudes would usually be attributed to the seasonal freezing and thawing cycles of ground ice. The origin of similar polygons on Mars is less certain, but might also be an indicator of ground ice.

    Location near: 75.3oS, 113.2oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  6. The Sinkholes at "Piano dell'Acqua

    NASA Astrophysics Data System (ADS)

    Iovine, G. G. R.; Parise, M.; Caloiero, T.; Lanza, G.; Suriano, S.

    2012-04-01

    Five sinkholes have recently been identified in the territory of San Basile (Northern Calabria, Southern Italy), in locality "Piano dell'Acqua". The sinkholes are located in a hilly setting, where the main landform is represented by a slight valley draining toward the east. The sinkholes are limited in size, with maximum diameter of 10 m, and maximum depth of 2.5 m. Two of them are elongated, whilst the remaining three are circular. The area where the sinkholes develop is characterized by Pliocene conglomerate and sand, likely dislocated by tectonic lines. The sinkholes were initially examined by means of multi-temporal aerial photos, and the outcomes from this analysis were checked in the field through geological, structural and geomorphological surveys. At the same time, an historical analysis was started in order to collect and critically evaluate the existing information and testimonies about age of occurrence of the phenomena. At this aim, several interviews with local inhabitants were performed, and a number of archives scrutinized. As a result, the study allowed to hypothesize that two sinkholes developed during the winter 2000-2001, with likely rapid formation. Two other cases probably originated during the 70's, as also suggested by the age of the vegetation hosted within the sinkholes. The last sinkhole, eventually, opened sometime between February 2001 and November 2007. According to the collected testimonies, a further phase of sinkhole development might have occurred in the first half of the past Century, but no field evidence of this older phase has been found so far. Analysis of the seismic catalogues showed that no earthquake can be identified as possible trigger of any of the sinkholes at Piano dell'Acqua. Therefore, the origin of the studied phenomena should be related to sub-cutaneous erosion, within an area that is rich in groundwater (as also shown by the site name, meaning "Water Plain"). Local changes in the water table, both related to

  7. Mid-latitude Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    7 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes on the floor of a southern mid-latitude impact crater. Craters are commonly the site of sand dunes, as sand may become trapped in these topographic depressions. In this case, the winds responsible for the dunes generally blew from the south/southeast (bottom/lower right),

    Location near: 51.8oS, 105.5oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  8. Mid-latitude Gullies

    NASA Technical Reports Server (NTRS)

    2005-01-01

    25 November 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of south mid-latitude gullies on a crater wall. Gullies such as these may have formed by runoff of liquid water.

    Location near: 38.0oS, 167.2oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  9. High Latitude Polygons

    NASA Technical Reports Server (NTRS)

    2004-01-01

    21 September 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows polygon patterned ground in the south polar region near 82.0oS, 90.8oW. Polygons are fairly common at high latitudes in both martian hemispheres, but they do not occur everywhere. On Earth, features such as these would be good indicators of the presence and freeze-thaw cycles of ground ice. On Mars, the same might (emphasis on might) also be true. This image covers an area approximately 3 km (1.9 mi) across and is illuminated by sunlight from the upper left. Seasonal frost enhances the contrast in the scene; the darkest areas have advanced the farthest in the springtime defrosting process.

  10. Playing Funny: An Introduction to "Commedia dell' Arte."

    ERIC Educational Resources Information Center

    Grantham, Barry

    2001-01-01

    Discusses the use of "Commedia," a way of performing inspired by the historical "Commedia dell' Arte." Notes that it has proved a fertile source of inspiration for all types of physical and stylized theatre and a useful training tool for performers in many fields. Presents a series of exercises designed to introduce the student to Commedia…

  11. Latitude dependence of eddy variances

    NASA Technical Reports Server (NTRS)

    Bowman, Kenneth P.; Bell, Thomas L.

    1987-01-01

    The eddy variance of a meteorological field must tend to zero at high latitudes due solely to the nature of spherical polar coordinates. The zonal averaging operator defines a length scale: the circumference of the latitude circle. When the circumference of the latitude circle is greater than the correlation length of the field, the eddy variance from transient eddies is the result of differences between statistically independent regions. When the circumference is less than the correlation length, the eddy variance is computed from points that are well correlated with each other, and so is reduced. The expansion of a field into zonal Fourier components is also influenced by the use of spherical coordinates. As is well known, a phenomenon of fixed wavelength will have different zonal wavenumbers at different latitudes. Simple analytical examples of these effects are presented along with an observational example from satellite ozone data. It is found that geometrical effects can be important even in middle latitudes.

  12. When Poetry became Ethnography and Other Flying Pig Tales in Honor of Dell Hymes

    ERIC Educational Resources Information Center

    Cahnmann-Taylor, Melisa

    2011-01-01

    Cahnmann-Taylor remembers her first encounter with Dell Hymes at an open mic event at the annual meeting of the American Anthropological Association. She puzzles his complex stance on the role ethnographic poems might play in one's ethnographic project. In Dell Hymes's honor, she shares a poetic rendering of a speech event from her bilingual…

  13. Enabling Customization through Web Development: An Iterative Study of the Dell Computer Corporation Website

    ERIC Educational Resources Information Center

    Liu, Chang; Mackie, Brian G.

    2008-01-01

    Throughout the last decade, companies have increased their investment in electronic commerce (EC) by developing and implementing Web-based applications on the Internet. This paper describes a class project to develop a customized computer website which is similar to Dell Computer Corporation's (Dell) website. The objective of this project is to…

  14. Latitudes: new Indian transnational cinema.

    PubMed

    Villarejo, Amy

    2014-01-01

    This article examines films and video art that speak to conditions of exile and displacement, including the work of Mona Hatoum, Sonali Gulati, and Onir. It proposes the term "latitude" to interrogate the aesthetic and formal properties of these artworks, seeking to understand how lesbian and same-sex eroticism and identities are central to their efficacy. PMID:24972281

  15. Streaking into middle school science: The Dell Streak pilot project

    NASA Astrophysics Data System (ADS)

    Austin, Susan Eudy

    A case study is conducted implementing the Dell Streak seven-inch android device into eighth grade science classes of one teacher in a rural middle school in the Piedmont region of North Carolina. The purpose of the study is to determine if the use of the Dell Streaks would increase student achievement on standardized subject testing, if the Streak could be used as an effective instructional tool, and if it could be considered an effective instructional resource for reviewing and preparing for the science assessments. A mixed method research design was used for the study to analyze both quantitative and qualitative results to determine if the Dell Streaks' utilization could achieve the following: 1. instructional strategies would change, 2. it would be an effective instructional tool, and 3. a comparison of the students' test scores and benchmark assessments' scores would provide statistically significant difference. Through the use of an ANOVA it was determined a statistically significant difference had occurred. A Post Hoc analysis was conducted to identify where the difference occurred. Finally a T-test determined was there was no statistically significance difference between the mean End-of-Grade tests and four quarterly benchmark scores of the control and the experimental groups. Qualitative research methods were used to gather results to determine if the Streaks were an effective instructional tool. Classroom observations identified that the teacher's teaching styles and new instructional strategies were implemented throughout the pilot project. Students had an opportunity to complete a questionnaire three times during the pilot project. Results revealed what the students liked about using the devices and the challenges they were facing. The teacher completed a reflective questionnaire throughout the pilot project and offered valuable reflections about the use of the devices in an educational setting. The reflection data supporting the case study was drawn

  16. High Latitude Mottling on Jupiter

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The familiar banded appearance of Jupiter at low and middle latitudes gradually gives way to a more mottled appearance at high latitudes in this striking true color image taken Dec. 13, 2000, by NASA's Cassini spacecraft.

    The intricate structures seen in the polar region are clouds of different chemical composition, height and thickness. Clouds are organized by winds, and the mottled appearance in the polar regions suggests more vortex-type motion and winds of less vigor at higher latitudes.

    The cause of this difference is not understood. One possible contributor is that the horizontal component of the Coriolis force, which arises from the planet's rotation and is responsible for curving the trajectories of ocean currents and winds on Earth, has its greatest effect at high latitudes and vanishes at the equator. This tends to create small, intense vortices at high latitudes on Jupiter. Another possibility may lie in that fact that Jupiter overall emits nearly as much of its own heat as it absorbs from the Sun, and this internal heat flux is very likely greater at the poles. This condition could lead to enhanced convection at the poles and more vortex-type structures. Further analysis of Cassini images, including analysis of sequences taken over a span of time, should help us understand the cause of equator-to-pole differences in cloud organization and evolution.

    By the time this picture was taken, Cassini had reached close enough to Jupiter to allow the spacecraft to return images with more detail than what's possible with the planetary camera on NASA's Earth-orbiting Hubble Space Telescope. The resolution here is 114 kilometers (71 miles) per pixel. This contrast-enhanced, edge-sharpened frame was composited from images take at different wavelengths with Cassini's narrow-angle camera, from a distance of 19 million kilometers (11.8 million miles). The spacecraft was in almost a direct line between the Sun and Jupiter, so the solar illumination on

  17. The Latitude, Longitude--Spell It Game.

    ERIC Educational Resources Information Center

    Kirman, Joseph M.

    1990-01-01

    Presents a classroom exercise entitled, "Latitude, Longitude, Spell It" designed to reinforce the concepts of latitude and longitude. Teachers divide the class into teams, provide them with a map and latitude-longitude coordinate cards, and ask them to record cities found within a given radius of each coordinate. Includes necessary materials and…

  18. Surviving Rescue: A Feminist Reading of Scott O'Dell's "Island of the Blue Dolphins"

    ERIC Educational Resources Information Center

    Baecker, Diann L.

    2007-01-01

    Scott O'Dell's "Island of the Blue Dolphins" tells the archetypal story of the young, virgin, orphan girl who is vulnerable to either debauchery or rescue. That such a girl must succumb to either one or the other is a necessary element of the archetype. In O'Dell's work--one intended, after all, for children--the heroine is rescued by a…

  19. South Mid-latitude Gullies

    NASA Technical Reports Server (NTRS)

    2005-01-01

    19 November 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows deep gullies cut into the wall of a south mid-latitude crater. Erosion has exposed layers in the upper wall of the crater; it is possible that groundwater seeping through a layer or layers in the wall led to the genesis of the gullies. The banked nature of the gully channels suggests that a liquid was involved.

    Location near: 35.5oS, 194.8oW Image width: width: 2 km (1.2 mi) Illumination from: upper left Season: Southern Spring

  20. High latitude pulsating aurorae revisited

    SciTech Connect

    Wu, Q.; Rosenberg, T.J. )

    1992-01-03

    Dayside auroral pulsations (10-40 s periods) have been studied for different levels of geomagnetic disturbance with N{sub 2}{sup +} 427.8 nm emission data obtained at South Pole station, Antarctica ({minus}74.2{degree} MLAT). The occurrence distribution exhibits a single peak at magnetic noon under geomagnetically quiet conditions (0 {le} Kp < 1). With increased Kp, the distribution shifts to earlier times, the peak occurring at 1000-1030 MLT for 1 {le} Kp < 4. At these higher Kp levels a secondary occurrence peak is evident in the afternoon sector between 1400 and 1600 MLT, occurring earlier as Kp increases. These results are compared with those obtained separately for pre-noon pulsations observed at Ny Alesund and post-noon pulsations observed at Ny Alesund and post-noon pulsations observed at Davis, northern and southern hemisphere sites at approximately the same magnetic latitude as South Pole. South Pole and Ny Alesund observe morning peaks at the same time and with a similar lack of Kp dependence; South Pole and Davis observe afternoon peaks with similar Kp dependence, though the peak occurs earlier at Davis. In contrast to the results from the earlier studies, the South Pole observations show larger pulsation amplitudes in the morning sector and significantly higher occurrence rates overall.

  1. Low-latitude ionospheric effects on SBAS

    NASA Astrophysics Data System (ADS)

    Arenas, J.; Sardón, E.; Sainz, A.; Ochoa, B.; Magdaleno, S.

    2016-06-01

    Satellite-based augmentation systems (SBAS) provide augmentation to Global Navigation Satellite Systems (GNSS) users in three areas: (1) broadcasting accurate corrections to GNSS satellite ephemeris, (2) providing a real-time empirical ionospheric model in the service area, and (3) providing integrity information in the form of estimates of the confidence of the ephemeris corrections and ionospheric delays. Ionospheric effects on SBAS are twofold: (a) the input data used by the SBAS will be affected by ionospheric effects, and (b) the more perturbed the ionosphere is, the more difficult it will be to provide accurate and reliable ionospheric information to the users. The ionosphere at low latitudes presents larger variability and more intense phenomena than at midlatitudes. Therefore, SBAS providing service to low-latitude regions will be more affected than those at other latitudes. From the different low-latitude ionospheric effects, this paper will focus on those having the largest impact on SBAS, which are total electron content temporal and spatial gradients, ionospheric scintillations, and depletions. This paper will present the impact of these effects on EGNOS (European Global Navigation Overlay System), the European SBAS. Although EGNOS can be considered as a midlatitude SBAS, it has to provide coverage down to rather low latitudes, so sometimes low-latitude ionospheric effects are observed in the EGNOS data. It will be shown how EGNOS performs under nominal conditions and how its performance is degraded when low-latitude ionospheric phenomena occur. Real EGNOS data affected by low-latitude ionospheric phenomena will be used.

  2. An Unintentional System of Gaps: A Phenomenological Reading of Scott O'Dell's "Island of the Blue Dolphins."

    ERIC Educational Resources Information Center

    Tarr, C. Anita

    1997-01-01

    Argues that, in "Island of the Blue Dolphins," Scott O'Dell offers a skeleton main character (Karana). Contends that O'Dell has sketched Karana as a stereotype and that readers complete her characterization, filling out the skeleton by perpetuating the stereotypes. Points out this trading of stereotype for true character development in his other…

  3. 75 FR 38128 - Ceva Freight, LLC, Dell Logistics Division, Including On-Site Leased Workers From Prologistix and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-01

    ..., LLC, Dell Logistics Division, including on-site leased workers from Prologistix, Winston-Salem, North Carolina. The notice was published in the Federal Register on April 23, 2010 (75 FR 21357). At the request... Employment and Training Administration Ceva Freight, LLC, Dell Logistics Division, Including On-Site...

  4. Low Latitude Plasma Blobs: A Review

    NASA Astrophysics Data System (ADS)

    Kim, Vitaly P.; Hegai, Valery V.

    2016-03-01

    In recent years, there has been renewed activity in the study of local plasma density enhancements in the low latitude F region ionosphere (low latitude plasma blobs). Satellite, all-sky airglow imager, and radar measurements have identified the characteristics of these blobs, and their coupling to Equatorial Plasma Bubbles (EPBs). New information related to blobs has also been obtained from the Communication/Navigation Outage Forecasting System (C/NOFS) satellite. In this paper, we briefly review experimental, theoretical and modeling studies related to low latitude plasma blobs.

  5. Jupiter's Temperatures--Broad Latitude

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This is one of the highest resolution images ever recorded of Jupiter's temperature field. It was obtained by NASA's Galileo mission, with its Photopolarimeter-Radiometer (PPR) experiment, during the seventh of its 10 orbits around Jupiter to date. This map, shown in the left panel, indicates the forces powering Jovian winds, and differentiates between areas of strongest upwelling and downwelling winds in the upper part of the atmosphere. A Hubble Space Telescope Planetary Camera color composite of this same region, taken within 10 hours of the PPR map, is shown in the right panel for the same region, as a reference to the visual clouds. An outline of the region mapped by the PPR is also shown.

    This atmospheric observation covered a broad latitude region, and it shows that the visually dark regions generally have warmer temperatures than the visually light ones, indicating that they are regions of downwelling, dry air which clear out cloud condensate particles. The 'little red spot' at the northernmost part of this image is colder than its surroundings, consistent with it being a region of upwelling and cooling gas. The smaller spots to its southeast (lower right) and other lighter spots in the HST image are all colder than their surroundings, consistent with regions of upwelling and cooling gas. The northern half of the brightest band in the map is brighter than the southern half, and it reveals some detailed structure, down to the 1900- kilometer (1200-mile) resolution of the PPR, which is not always readily correlated with variations of the visual cloud field.

    One surprise of this temperature map involved temperatures near the dark blue-gray feature in the map, an area like the one into which the Probe descended. While large regions of downwelling wind heat the local area elsewhere in Jupiter, this region of vigorous downwelling appears close to being thermally neutral. The drying, downwelling winds may be deeper in the atmosphere than sensed by the PPR

  6. Warming: mechanism and latitude dependence

    NASA Astrophysics Data System (ADS)

    Barkin, Yury

    2010-05-01

    flows distribution with respect the Earth's hemispheres in first caused by eccentric position of the Earth core with respect to the mantle (displaced in present geological epoch in direction to Brasil). Of course the asymmetric distribution of heat loss is a long-term phenomenon in the geological history. But in present epoch due to drift of the core to the North we must observe some increasing of the heat flow of the Northern hemisphere and decreasing of the heat flow of the Southern hemisphere. In reality mentioned changes of heat flows are contrast (asymmetrical) and can have general tendency of increasing heat flows in both hemispheres (due to activization of relative oscillations of the core and mantle relatively polar axis). Contrast secular warming of Northern and Southern hemispheres of the Earth in present epoch. Dependence of warming from latitude. And warm flows are asymmetrically, more intensively warm is redistributed in northern hemisphere of the Earth and less intensively in a southern hemisphere. From here it follows, that the phenomenon of more intensive warming up of northern hemisphere, rather than southern in present period should be observed. Data of climatic observations (in first temperature trends for various latitude belts). More detailed analysis shows, that the phenomenon of warming in different form is shown in various latitudinal belts of the Earth. This phenomenon is more clearly shown in latitudinal belts further situated on latitude from South Pole, i.e. in high northern latitudes. Really, the trend of increase of temperature in northern hemisphere is characterized by greater rate, than a trend of temperature in a southern hemisphere. And not only trend components of temperatures increase with increasing of latitudes from southern pole to northern pole, but also amplitudes of decade fluctuations of temperature in high northern breadthes are more bigger than in southern hemisphere. Thus again it is necessary to expect a contrast and

  7. Electrodynamics of the high-latitude mesosphere

    NASA Technical Reports Server (NTRS)

    Goldberg, Richard A.

    1989-01-01

    The discovery of apparent large (V/m) electric fields within the mesosphere suggests that this region is more active electrically than originally suspected. High-latitude observations have been particularly productive in developing new concepts regarding mesospheric electrodynamics. Several high-latitude observations of large mesospheric fields have been made under both quiet and aurorally active conditions but always below heights where enhanced ionizing radiations could significantly penetrate. Two measurements from Andoya, Norway, have also produced an anticorrelation of horizontal electric field directions with neutral wind velocities, leading to the theoretical description of a newly defined mechanism for V/m electric field generation involving wind-induced separation of charged aerosols. Evidence for mesospheric aerosols and winds exists at all latitudes but is most evident at high latitudes during the appearance of noctilucent and/or polar mesospheric clouds.

  8. Active Latitude Oscillations Observed on the Sun

    NASA Astrophysics Data System (ADS)

    Kilcik, A.; Yurchyshyn, V.; Clette, F.; Ozguc, A.; Rozelot, J.-P.

    2016-04-01

    We investigate periodicities in the mean heliographic latitudes of sunspot groups, called active latitudes, for the past six complete solar cycles (1945 - 2008). For this purpose, the multitaper method and Morlet wavelet analysis were used. We found that solar rotation periodicities (26 - 38 days) are present in active latitudes of both hemispheres for all the investigated cycles (18 to 23). Both in the northern and southern hemispheres, active latitudes drifted toward the equator from the beginning to the end of each cycle and followed an oscillating path. These motions are well described by a second-order polynomial. There are no meaningful periods of between 55 and about 300 days in either hemisphere for all cycles. A periodicity of 300 to 370 days appears in both hemispheres for Cycle 23, in the northern hemisphere for Cycle 20, and in the southern hemisphere for Cycle 18.

  9. Low Latitude Aurora: Index of Solar Activity

    NASA Astrophysics Data System (ADS)

    Bekli, M. R.; Aissani, D.; Chadou, I.

    2010-10-01

    Observations of aurora borealis at low latitudes are rare, and are clearly associated with high solar activity. In this paper, we analyze some details of the solar activity during the years 1769-1792. Moreover, we describe in detail three low latitude auroras. The first event was reported by ash-Shalati and observed in North Africa (1770 AD). The second and third events were reported by l'Abbé Mann and observed in Europe (1770 and 1777 AD).

  10. Tracer exchange between tropics and middle latitudes

    NASA Technical Reports Server (NTRS)

    Rood, Richard; Douglass, Anne; Weaver, Clark

    1992-01-01

    The interaction between the tropics and middle latitudes is studied using a tracer emitted at 50 hPa along a great circle route between Los Angeles, USA and Sydney, Australia. Though designed to examine the impact of stratospheric aircraft, the study more generally addresses the transport between tropics and middle latitudes for a three month period from January through March 1989. The results show that air is transported from the tropics to middle latitudes by planetary scale and tropospheric cyclonic scale waves. Except for intrusions by these wave events, the tropics are substantially isolated throughout the lower stratosphere. These waves draw material out of the tropics which ends up in the middle latitude westerly jets, with little material entering the winter polar latitudes prior to the springtime transition. The summer Southern Hemisphere is characterized by tracer being drawn out in streamers that extend from north and west to south and east. The material in the tropics is zonally asymmetric. The material that reaches the troposphere comes down in the synoptic scale eddies and is concentrated in the middle latitude jet stream. These characteristics are similar to those observed during the dispersion of volcanic clouds.

  11. Meteor scatter radio communication at high latitudes

    NASA Astrophysics Data System (ADS)

    Cannon, P. S.; Dickson, A. H.; Armstrong, M. H.

    1985-11-01

    A brief historical and physical description of the meteor burst communications (MBC) technique is given together with a discussion of the advantages of very high frequency MBC, with respect to conventional high frequency communication, when used at high latitudes. A recently deployed high latitude MBC propagation experiment, between Bodo in Norway and Wick in Scotland (UK) is described and some of the early data gathered at frequencies close to 40 MHz and 70 MHz is presented. A theoretical description of the effects of Polarisation Rotation in a linearly polarised MBC system is developed and it is shown that at 40 MHz Polarisation Rotation, due to excess D-region ionization may cause the system performance to differ from its ambient level. Corroborative experimental results, over a temperature latitude path, are presented. Based upon the early high latitude experimental results and on the theoretical calculations, it is suggested that frequencies close to 40 MHz, in common use in atemperate latitude linearly polarised MBC systems, are too low for high latitude operation.

  12. High Latitude Dust in the Earth System

    NASA Technical Reports Server (NTRS)

    Bullard, Joanna E.; Baddock, Matthew; Bradwell, Tom; Crusius, John; Darlington, Eleanor; Gaiero, Diego; Gasso, Santiago; Gisladottir, Gudrun; Hodgkins, Richard; McCulloch, Robert; McKenna-Neuman, Cheryl; Mockford, Tom; Stewart, Helena; Thorsteinsson, Throstur

    2016-01-01

    Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high-latitude (> or = 50degN and > or = 40degS) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo-aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high-nutrient, low-chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high-latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year-round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high-latitude sources cover >500,000 sq km and contribute at least 80-100 Tg/yr1 of dust to the Earth system (approx. 5% of the global dust budget); both are projected to increase under future climate change scenarios.

  13. Dell Hymes and the New Language Policy Studies: Update from an Underdeveloped Country

    ERIC Educational Resources Information Center

    McCarty, Teresa L.; Collins, James; Hopson, Rodney K.

    2011-01-01

    This essay updates Dell Hymes's "Report from an Underdeveloped Country" (the USA), positioning our analysis in the New Language Policy Studies. Taking up Hymes's call for comparative, critical studies of language use, we examine three cases, organizing our analysis around Hymes's questions: What "counts" as a language, a language problem, and…

  14. Dell H. Hymes: His Scholarship and Legacy in Anthropology and Education

    ERIC Educational Resources Information Center

    Hornberger, Nancy H., Ed.

    2011-01-01

    Dell Hathaway Hymes, linguistic anthropologist and educational visionary extraordinaire, passed away in November 2009, leaving behind a voluminous scholarship and inspirational legacy in the study of language and inequality, ethnography, sociolinguistics, Native American ethnopoetics, and education. This essay provides a brief account of Hymes's…

  15. Quiet time enhancements over African latitudes

    NASA Astrophysics Data System (ADS)

    Orford, Nicola; Katamzi, Zama; Buresova, Dalia

    2016-07-01

    F2 layer disturbances not related to geomagnetic activity are known as quiet time enhancements (QTEs). The phenomenon of QTEs has not yet been studied over African latitudes. We therefore explore the occurrence of QTEs over Africa in order to expand our knowledge on the behaviour of the ionosphere over this region. Several GPS stations in the middle to equatorial latitudes, during the solar minimum (2009) and near solar maximum (2013), are used. This data was examined for possible trends in variation with solar cycle, season and latitude as well as time of commencement of enhancements. Over the southern mid-latitude region of Africa we have observed that the QTEs are more likely to commence during the night in both solar minimum and maximum, however a slightly larger portion of daytime commencements during solar minimum than during solar maximum were observed. The total number of enhancements for the solar minimum period appears greater than during solar maximum. A seasonal trend is seen with the maximum number of enhancements occurring in summer during solar minimum and in winter during solar maximum. We explore further whether these trends are mirrored or different at low latitude/equatorial African regions.

  16. Temporal, latitude and altitude absorbed dose dependences

    NASA Astrophysics Data System (ADS)

    Stozhkov, Y.; Svirzhevsky, N.; Bazilevskaya, G.

    The regular balloon measurements in the Earth's atmosphere are carried on at the Lebedev Physical Institute since 1957. The regular balloon flights have been made at the high latitude stations (near Murmansk - northern hemisphere and Mi ny -r Antarctica) and at the middle latitude (Moscow). Based on these long-term measurements as well as on the latitude data obtained in the several Soviet Antarctic expeditions the calculations of absorbed doses were fulfilled for altitudes of 10, 15, 20 and 30 km. The absorbed dose dependences on the geomagnetic cutoff rigidities and the phase of the 11-year solar cycle were found. The evaluation of the solar proton events and energetic electron precipitation contributions to the absorbed dose enhancements was made.

  17. Investigating the Relationship between Latitude and Temperature

    ERIC Educational Resources Information Center

    McGivney-Burelle, Jean; McGivney, Raymond J.; McGivney, Katherine G.

    2008-01-01

    This article describes an engaging, data-gathering activity that allows students to explore relationships between latitude and average monthly temperatures of cities in the Western Hemisphere. This data-gathering activity covered interesting and important mathematical ground and engaged students from the start. While students searched for their…

  18. Latitude dependence of narrow bipolar pulse emissions

    NASA Astrophysics Data System (ADS)

    Ahmad, M. R.; Esa, M. R. M.; Cooray, V.; Baharudin, Z. A.; Hettiarachchi, P.

    2015-06-01

    In this paper, we present a comparative study on the occurrence of narrow bipolar pulses (NBPs) and other forms of lightning flashes across various geographical areas ranging from northern regions to the tropics. As the latitude decreased from Uppsala, Sweden (59.8°N) to South Malaysia (1.5°N), the percentage of NBP emissions relative to the total number of lightning flashes increased significantly from 0.13% to 12%. Occurrences of positive NBPs were more common than negative NBPs at all observed latitudes. However, as latitudes decreased, the negative NBP emissions increased significantly from 20% (Uppsala, Sweden) to 45% (South Malaysia). Factors involving mixed-phase region elevations and vertical extents of thundercloud tops are invoked to explain the observed results. These factors are fundamentally latitude dependent. Our results suggest that the NBP emission rate is not a useful measure to monitor thunderstorm severity because regular tropical thunderstorms, where relatively high NBP emissions occur, lack suitable conditions to become severe (i.e., there is modest convective available potential energy and a lack of baroclinity in such regions). Observations of significantly high negative NBP occurrences together with very rare occurrences of positive cloud-to-ground flashes and isolated breakdown pulses in tropical thunderstorms are indicative of a stronger negative screening layer magnitude and weaker lower positive charge region magnitude than those in northern regions.

  19. Higher Education in the High Latitudes.

    ERIC Educational Resources Information Center

    Bollag, Burton

    2002-01-01

    Describes how colleges in 16 countries have joined in a network to serve the educational and research needs of the circumpolar region; the University of the Arctic is a band of high-latitude colleges which seeks to serve indigenous people and preserve a fragile environment. (EV)

  20. ULTRAVIOLET EXTINCTION AT HIGH GALACTIC LATITUDES

    SciTech Connect

    Peek, J. E. G.; Schiminovich, David

    2013-07-01

    In order to study the properties and effects of high Galactic latitude dust, we present an analysis of 373,303 galaxies selected from the Galaxy Evolution Explorer All-Sky Survey and Wide-field Infrared Explorer All-Sky Data Release. By examining the variation in aggregate ultraviolet colors and number density of these galaxies, we measure the extinction curve at high latitude. We additionally consider a population of spectroscopically selected galaxies from the Sloan Digital Sky Survey to measure extinction in the optical. We find that dust at high latitude is neither quantitatively nor qualitatively consistent with standard reddening laws. Extinction in the FUV and NUV is {approx}10% and {approx}35% higher than expected, with significant variation across the sky. We find that no single R{sub V} parameter fits both the optical and ultraviolet extinction at high latitude, and that while both show detectable variation across the sky, these variations are not related. We propose that the overall trends we detect likely stem from an increase in very small silicate grains in the interstellar medium.

  1. Latitude for the Observer of Ptolemy's Catalog

    NASA Astrophysics Data System (ADS)

    Schaefer, B. E.

    1999-12-01

    For centuries, researchers have claimed that substantial portions of Ptolemy's Almagest have been taken from Hipparchus in Rhodes (latitude 36.2 north). A substantial portion of these claims rest on the catalog of 1028 stars purported to be observed by Ptolemy in Alexandria (latitude 31.2 north). Various peculiarities is the star positions are inconclusive. However, aspects of the star catalog related to the visibility of stars near the horizon have not been treated with modern techniques. I have extensive experience in the heliacal rise, extinction angle, and the probability of detection (see Schaefer 1993, Vistas in Astronomy, 36, 311 for a review) all of which are critical to the problem. Also, I have been producing my own modern naked-eye star catalog so as to obtain practical knowledge of star visibility (especially near the southern horizon), completeness, and probability of detection. Also, I have determined the seasonal extinction coefficients (both median and best possible) for the eastern Mediterranean in ancient times based on 4000 in situ observations from 9 sites in modern and premodern times, measures of modern pollution components, and global models. Three criteria have been used to determine the latitude of the observer of the star catalog: First, the limiting magnitude (at the 50% level) as a function of declination can be compared against my model to derive the latitude. Second, the most southerly declination (at the 50% level) as a function of magnitude can also be compared against my model. For the first two criteria, quadrants are considered independently as well as individually to account for varying seasonal extinction and precession effects on the completeness of the traditional southern constellations. Third, the cataloged magnitudes are compared with modern magnitudes as a function of declination and compared with my extinction model for various latitudes.

  2. Comparative study of high-latitude, mid-latitude and low-latitude ionosphere on basis of local empirical models

    NASA Astrophysics Data System (ADS)

    Ratovsky, K. G.; Shi, J. K.; Oinats, A. V.; Romanova, E. B.

    2014-08-01

    The analysis of the regular features of the high-, mid- and low-latitude ionosphere characteristics has been carried out using local empirical models. The local empirical models were derived from the manual scaled ionogram data recorded by DPS-4 Digisondes located at Norilsk (69 N, 88E), Irkutsk (52 N, 104E) and Hainan (19 N, 109E) for a 6-year period from December, 2002 to December, 2008. The technique used to build the local empirical model is described. Primary focuses are diurnal, seasonal and solar cycle variations of the peak electron density and the peak height under low solar activity and their changes with increasing solar activity. The main objective of the paper is to reveal both common and specific features of high-, mid- and low-latitude ionosphere. Based on earlier comparisons with the International Reference Ionosphere model, we analyze how the common and specific features are reproduced by this model.

  3. Seismic refraction studies at the Painter Street bridge site, Rio Dell, California

    SciTech Connect

    Heuze, F.E.; Swift, R.P.

    1991-09-01

    This report summarizes the results of seismic refraction P- and S-wave measurements, at the site of the Painter Street bridge, in Rio Dell, California. The bridge is spanning highway US 101, 4 miles south of Fortuna, in northwestern California. This study was performed to provide an estimate of material properties for the foundation of the bridge, in support of a seismic stability analysis of the bridge performed at LLNL by D. McCallen. The Rio Dell region is seismically active and the Painter Street bridge is one of only 2 bridges of its type in California, instrumented for strong motion recordings. Measurements were made using a 12-channel Geometric/Nimbus ES 1210 Signal Enhancement Seismograph. 3 refs., 21 figs., 1 tab.

  4. Altitude latitude mapping of plasma depletions

    NASA Astrophysics Data System (ADS)

    Rajesh, P.; Liu, J.; Sinha, H.; Banerje, S.

    2007-12-01

    Plasma depletions, if generated at the geomagnetic equator, are expected to appear in the all sky images as dark bands extending pole ward. The all sky observations conducted from Kavalur (12.5¢ªN, 78.8¢ªE; 4.6¢ªN, geomagnetic), INDIA, but showed dark patches in 630.0 nm entering the imager field of view (FOV) from the northern edge in the post-sunset period. These patches gradually extended towards equator and became fully extended dark bands in the North-South direction by midnight. The series of such images appeared to be the airglow signatures of irregularities that are probably generated at off-equatorial latitudes and mapped to the lower or equatorial latitudes. Similar features were observed in several nights. This appearance of depletions as dark patches from the northern edge of the FOV is explained in this work

  5. Substorm electric fields at nightside low latitude

    NASA Astrophysics Data System (ADS)

    Hashimoto, K. K.; Kikuchi, T.; Tomizawa, I.; Nagatsuma, T.

    2014-12-01

    The convection electric field penetrates from the polar ionosphere to low latitude and drives the DP2 currents in the global ionosphere with an intensified equatorial electrojet (EEJ). The electric field often reverses its direction, that is, the overshielding occurs and causes the equatorial counterelectrojet (CEJ) during storm and substorms. In this paper we report that the overshielding electric field is detected by the HF Doppler sounders at low latitude on the nightside. We analyzed the Doppler frequency of the HF radio signals propagated over 120 km in Japan at frequencies of 5 and 8 MHz and compared with the equatorial EEJ/CEJ during the substorm expansion phase. We found that the overshielding electric field reaches around 2 mV/m during major substorms (AL <-1800 nT). Taking the geometrical attenuation into account, we estimate the equatorial electric field to be about 1.5 mV/m. We also found that the correlation coefficient was 0.94 between the overshielding electric field and eastward equatorial electrojet at YAP on the night side. The electric field drives the eastward electrojets in the equatorial ionosphere on the night side. It is to be noted that the overshielding electric field is observed on the nightside at low latitude during the major substorms, while the convection electric field is dominant during smaller size substorms, as the CEJ flows on the dayside. These results suggest that the overshielding electric field associated with the Region-2 field-aligned currents becomes dominant during substorms at low latitude on the nightside as well as on the dayside.

  6. Formation of High-Latitude Pedestal Craters

    NASA Technical Reports Server (NTRS)

    Wrobel, K. E.; Schultz, P. H.; Crawford, D. A.

    2005-01-01

    Prior to and just after an impact on Mars, a small fraction of the total impact energy is directly coupled to the ambient atmosphere. A resulting hemispherical shock wave propagates outward leaving a signature that is dependent on initial atmospheric and surface conditions. Here we propose that the distinctive pedestal craters common at high latitudes on Mars are a direct consequence of extreme winds and elevated temperatures generated by this atmospheric blast.

  7. Spacecraft design project: High latitude communications satellite

    NASA Technical Reports Server (NTRS)

    Josefson, Carl; Myers, Jack; Cloutier, Mike; Paluszek, Steve; Michael, Gerry; Hunter, Dan; Sakoda, Dan; Walters, Wes; Johnson, Dennis; Bauer, Terry

    1989-01-01

    The spacecraft design project was part of AE-4871, Advanced Spacecraft Design. The project was intended to provide experience in the design of all major components of a satellite. Each member of the class was given primary responsibility for a subsystem or design support function. Support was requested from the Naval Research Laboratory to augment the Naval Postgraduate School faculty. Analysis and design of each subsystem was done to the extent possible within the constraints of an eleven week quarter and the design facilities (hardware and software) available. The project team chose to evaluate the design of a high latitude communications satellite as representative of the design issues and tradeoffs necessary for a wide range of satellites. The High-Latitude Communications Satellite (HILACS) will provide a continuous UHF communications link between stations located north of the region covered by geosynchronous communications satellites, i.e., the area above approximately 60 N latitude. HILACS will also provide a communications link to stations below 60 N via a relay Net Control Station (NCS), which is located with access to both the HILACS and geosynchronous communications satellites. The communications payload will operate only for that portion of the orbit necessary to provide specified coverage.

  8. Recurrent pulsations in Saturn's high latitude magnetosphere

    NASA Astrophysics Data System (ADS)

    Mitchell, D. G.; Carbary, J. F.; Bunce, E. J.; Radioti, A.; Badman, S. V.; Pryor, W. R.; Hospodarsky, G. B.; Kurth, W. S.

    2016-01-01

    Over the course of about 6 h on Day 129, 2008, the UV imaging spectrograph (UVIS) on the Cassini spacecraft observed a repeated intensification and broadening of the high latitude auroral oval into the polar cap. This feature repeated at least 5 times with about a 1 h period, as it rotated in the direction of corotation, somewhat below the planetary rotation rate, such that it moved from noon to post-dusk, and from roughly 77° to 82° northern latitudes during the observing interval. The recurring UV observation was accompanied by pronounced ∼1 h pulsations in auroral hiss power, magnetic perturbations consistent with small-scale field aligned currents, and energetic ion conics and electrons beaming upward parallel to the local magnetic field at the spacecraft location. The magnetic field and particle events are in phase with the auroral hiss pulsation. This event, taken in the context of the more thoroughly documented auroral hiss and particle signatures (seen on many high latitude Cassini orbits), sheds light on the possible driving mechanisms, the most likely of which are magnetopause reconnection and/or Kelvin Helmholtz waves.

  9. CCD technique for longitude/latitude astronomy

    NASA Astrophysics Data System (ADS)

    Damljanović, G.; Gerstbach, G.; de Biasi, M. S.; Pejović, N.

    2003-10-01

    We report about CCD (Charge Coupled Device) experiments with the isntruments of astrometry and geodesy for the longitude and latitude determinations. At the Techn. University Vienna (TU Vienna), a mobile zenith camera "G1" was developed, based on CCD MX916 (Starlight Xpress) and F=20 cm photo optic. With Hipparcos/Tycho Catalogue, the first results show accuracy up to 0."5 for latitude/longitude. The PC-guided observations can be completed within 10 minutes. The camera G1 (near 4 kg) is used for astrogeodesy (geoid, Earth's crust, etc.). At the Belgrade Astronomical Observatory (AOB), the accuracy of (mean value of) latitude/longitude determinations can be a few 0."01 using zenith stars, Tycho-2 Catalogue and a ST-8 of SBIG (Santa Barbara Instrument Group) with zenith-telescope BLZ (D=11 cm, F=128.7 cm). The same equipment with PIP instrument (D=20 cm and F=457.7 cm, Punta Indio PZT, near La Plata) yields a little better accuracy than the BLZ's one. Both instruments, BLZ and PIP, where in the list of Bureau International de l'Heure - BIH. The mentioned instruments have acquired good possibilities for semi or full-automatic observations.

  10. Photosynthetically active sunlight at high southern latitudes.

    PubMed

    Frederick, John E; Liao, Yixiang

    2005-01-01

    A network of scanning spectroradiometers has acquired a multiyear database of visible solar irradiance, covering wavelengths from 400 to 600 nm, at four sites in the high-latitude Southern Hemisphere, from 55 degrees S to 90 degrees S. Monthly irradiations computed from the hourly measurements reveal the character of the seasonal cycle and illustrate the role of cloudiness as functions of latitude. Near summer solstice, the combined influences of solar elevation and the duration of daylight would produce a monthly irradiation with little latitude dependence under clear skies. However, the attenuation associated with local cloudiness varies geographically, with the greatest effect at the most northern locations, Ushuaia, Argentina and Palmer Station on the Antarctic Peninsula. Near summer solstice, the South Pole experiences the largest monthly irradiation of the sites studied, where relatively clear skies contribute to this result. Scaling factors derived from radiative-transfer calculations combined with the measured 400-600 nm irradiances allow estimating irradiances integrated over the wavelength band 400-700 nm. This produces a climatology of photosynthetically active radiation for each month of the year at each site. PMID:15689179

  11. Breeding season of wolves, Canis lupus, in relation to latitude

    USGS Publications Warehouse

    Mech, L.D.

    2002-01-01

    A significant relationship was found between Wolf (Canis lupus) breeding dates and latitudes between 12 deg. and 80 deg. N, with Wolves breeding earlier at lower latitudes, probably because of differences in seasonality.

  12. Breeding season of Wolves, Canis lupus, in relation to latitude

    USGS Publications Warehouse

    Mech, L.D.

    2002-01-01

    A significant relationship was found between Wolf (Canis lupus) breeding dates and latitudes between 12?? and 80??N, with Wolves breeding earlier at lower latitudes, probably because of differences in seasonality.

  13. A high-latitude convective cloud feedback

    NASA Astrophysics Data System (ADS)

    Abbot, Dorian Schuyler

    Available data suggest that during the late Cretaceous and early Paleogene (˜100 to ˜35 million years ago) Earth had an "equable" climate: the equator to pole surface temperature difference and seasonal cycle in high-latitude surface temperature were both much smaller than they are today. The combination of much warmer high latitudes, particularly during winter, and only somewhat warmer tropics has traditionally been difficult to model in global climate models and to explain physically. In this thesis a positive feedback on high-latitude surface temperatures based on the onset of convection and convective clouds is proposed and investigated using a hierarchy of climate models. This feedback mechanism is based on an initial warming leading to destabilization of the high-latitude atmosphere to convection, causing convection, which results in convective clouds and increased atmospheric moisture, both of which trap outgoing longwave radiation and lead to further warming. It is also shown that this convective cloud feedback could be active in a future atmosphere with increased greenhouse gasses, increasing high-latitude climate uncertainty under global warming scenarios. A variety of climate models are used to understand the convective cloudfeedback in this thesis. Simple, analytical models are used in two chapters to understand more complex models and their underlying physics. A zonally-averaged, two-level model of the atmosphere without a seasonal cycle, but containing a hydrological cycle and parameterizations of convection, precipitation, and clouds, and a longwave radiation scheme that explicitly depends on CO 2, water vapor, and cloud fraction is constructed and used as an initial test of the feedback mechanism. The National Center for Atmospheric Research (NCAR) single column model (SCAM), which contains state-of-the-art atmospheric physics parameterizations, high vertical resolution, a full seasonal cycle, a thermodynamic sea ice model, and a mixed layer ocean

  14. Comparison of high-latitude and mid-latitude ionospheric electric fields

    NASA Technical Reports Server (NTRS)

    Carpenter, L. A.; Kirchhoff, V. W. J. H.

    1975-01-01

    Simultaneous measurements of the F region electric field by the incoherent scatter technique have been made at Chatanika, Alaska (65.1 deg N, 147.5 deg W), and Millstone Hill, Massachusetts (42.6 deg N, 71.5 deg W), on July 18-19 and Aug. 7-8, 1973. Good correlation was observed in the time variation of the perpendicular electric field at the two stations. Magnetic conditions for these days were relatively quiet with some variations evident from the high-latitude magnetograms and the Chatanika radar, but no distinct effect appeared on the mid-latitude magnetograms. Since magnetospheric electric fields are thought to be the source of high-latitude electric fields such as those observed at Chatanika, the good correlation in the perpendicular electric field for the two stations indicates that the magnetospheric originated electric fields have an appreciable effect down to at least L equals 3.2.

  15. Mid-Latitude Sedimentary Rock: Spallanzani Crater

    NASA Technical Reports Server (NTRS)

    2001-01-01

    [figure removed for brevity, see original site]

    Although most of the best examples of layered sedimentary rock seen on Mars are found at equatorial and sub-tropical latitudes, a few locations seen at mid- and high-latitudes suggest that layered rocks are probably more common than we can actually see from orbit. One extremely good example of these 'atypical' layered rock exposures is found in the 72 km-diameter (45 miles) crater, Spallanzani (58.4oS, 273.5oW). Located southeast of Hellas Planitia, the crater is named for the 18th Century Italian biologist, Lazzaro Spallanzani (1729-1799). Picture A presents a composite of the best Viking orbiter image (VO2-504B55) of the region with 4 pictures obtained June 1999 through January 2001 by the Mars Global Surveyor Mars Orbiter Camera (MOC). Each MOC narrow angle image is 3 km across. Taken in the MOC's 'survey mode,' all four images were acquired at roughly 12 meters (39 ft) per pixel. Picture B zooms-in on the portion of the composite image that includes the 4 MOC images (the 100%-size view is 20 m (66 ft) per pixel). Other craters in the region near Spallanzani show features--at Viking Orbiter scale--that are reminiscent of the layering seen in Spallanzani. Exactly what these layers are made of and how they came to be where we see them today are mysteries, but it is possible that they are similar to the materials seen in the many craters and chasms of the equatorial latitudes on Mars.

  16. Electrodynamics of the high latitude middle atmosphere

    NASA Technical Reports Server (NTRS)

    Goldberg, R. A.

    1987-01-01

    Atmospheric electrodynamics is reviewed. The discovery of apparent large (V/m) electric fields within the mesosphere invites the possibility for this region to be electrically active. Observations of the V/m field were made at high latitudes even under active conditions, but always below heights where significant enhancements in electrical conductivity are found to occur. Two measurements at Andoya (Norway) show anticorrelation of horizontal field directions with wind directions, suggesting a mechanism which involves mechanical separation of charged aerosols. Reported evidence for such aerosols makes this concept more viable. Noctilucent clouds and mesospheric turbulence, and their influence on the local electrical environment are mentioned.

  17. Magnetic latitude effects in the solar wind

    NASA Technical Reports Server (NTRS)

    Winge, C. R., Jr.; Coleman, P. J., Jr.

    1972-01-01

    The Weber-Davis model of the solar wind is generalized to include the effects of latitude. The principal assumptions of high electrical conductivity, rotational symmetry, the polytropic relation between pressure and density, and a flow-alined field in a system rotating with the sun, are retained. An approximate solution to the resulting equations for spherical boundary conditions at the base of the corona indicates a small component of latitudinal flow toward the solar poles at large distances from the sun as result of latitudinal magnetic forces.

  18. EGRET Sources at Intermediate Galactic Latitudes

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P.

    1998-01-01

    During the period 15 March 1992 through 31 October 1997, 12 papers using ROSAT data, supported in part by this grant, were published in referred journals, and one paper was published in a conference proceedings. Their bibliographical references are listed in the Appendix, and the abstracts of these papers are given in the next 13 sections of this report. Finally, a summary of the work completed to date on the newest project, for which ROSAT data are still being received, is given in the section entitled "EGRET Sources at Intermediate Galactic Latitude".

  19. The role of latitude in mobilism debates.

    PubMed

    Irving, Edward

    2005-02-01

    In the early 1920s, the continental displacement theory of Wegener, latitude studies of Koppen and Wegener, and Argand's ideas on mountain building led to the first mobilistic paleogeography. In the 1930s and 1940s, many factors caused its general abandonment. Mobilism was revived in the 1950s and 1960s by measurements of long-term displacement of crustal blocks relative to each other (tectonic displacement) and to Earth's geographic pole (latitudinal displacement). Also, short-term or current displacements can now be measured. I briefly outline the categories of tectonic and current displacement and focus on latitudinal displacement. Integration of tectonic and latitudinal displacement in the early 1970s completed the new mobilistic paleogeography, in which the transformation of rock magnetization directions into paleopoles and latitudes and the finite rotation of spherical plates about pivot points play complementary roles; this new synthesis now provides a quantitative basis for studying long-term evolution of Earth's surface features and climate, the changing environments in which life evolves. PMID:15684058

  20. Discovery of Temperate Latitude Clouds on Titan

    NASA Astrophysics Data System (ADS)

    Roe, H. G.; Bouchez, A. H.; Trujillo, C. A.; Schaller, E. L.; Brown, M. E.

    2005-01-01

    Until now, all the clouds imaged in Titan's troposphere have been found at far southern latitudes (60°-90° south). The occurrence and location of these clouds is thought to be the result of convection driven by the maximum annual solar heating of Titan's surface, which occurs at summer solstice (2002 October) in this south polar region. We report the first observations of a new recurring type of tropospheric cloud feature, confined narrowly to ~40° south latitude, which cannot be explained by this simple insolation hypothesis. We propose two classes of formation scenario, one linked to surface geography and the other to seasonally evolving circulation, which will be easily distinguished with continued observations over the next few years. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (US), the Particle Physics and Astronomy Research Council (UK), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina).

  1. Characteristics of High Latitude Ionosphere Scintillations

    NASA Astrophysics Data System (ADS)

    Morton, Y.

    2012-12-01

    As we enter a new solar maximum period, global navigation satellite systems (GNSS) receivers, especially the ones operating in high latitude and equatorial regions, are facing an increasing threat from ionosphere scintillations. The increased solar activities, however, also offer a great opportunity to collect scintillation data to characterize scintillation signal parameters and ionosphere irregularities. While there are numerous GPS receivers deployed around the globe to monitor ionosphere scintillations, most of them are commercial receivers whose signal processing mechanisms are not designed to operate under ionosphere scintillation. As a result, they may distort scintillation signal parameters or lose lock of satellite signals under strong scintillations. Since 2008, we have established and continuously improved a unique GNSS receiver array at HAARP, Alaska. The array contains high ends commercial receivers and custom RF front ends which can be automatically triggered to collect high quality GPS and GLONASS satellite signals during controlled heating experiments and natural scintillation events. Custom designed receiver signal tracking algorithms aim to preserve true scintillation signatures are used to process the raw RF samples. Signal strength, carrier phase, and relative TEC measurements generated by the receiver array since its inception have been analyzed to characterize high latitude scintillation phenomena. Daily, seasonal, and solar events dependency of scintillation occurrence, spectral contents of scintillation activities, and plasma drifts derived from these measurements will be presented. These interesting results demonstrate the feasibility and effectiveness of our experimental data collection system in providing insightful details of ionosphere responses to active perturbations and natural disturbances.

  2. Transient magnetic field signatures at high latitudes

    SciTech Connect

    Sibeck, D.G. )

    1993-01-01

    We survey GOES 2/5/6 geosynchronous and Huancayo, Peru, ground magnetometer observations at the times of 70 transient (2-10 min) events recorded at South Pole Station, Antarctica. The simultaneous observations indicate that most South Pole events correspond to sudden sharp variations in the equatorial magnetospheric and low-latitude ground magnetic field. The exceptions occur when the South Pole events have weak amplitudes and/or Huancayo and GOES 2/5/6 are far from local noon. The corresponding features observed at GOES 5 and GOES 6 are generally similar, with a lag indicating antisunward motion. A similar antisunward motion may be inferred from the ground observations themselves. On a case-by-case and statistical basis, the characteristics of the events observed in South Pole ground magnetograms resemble those previously interpreted as sudden impulse and sudden storm commencement signatures at other high-latitude stations. These observations suggest that the transient events at South Pole form part of the magnetospheric and ionospheric response to a sudden change in the fraction of the solar wind dynamic pressure applied to the magnetosphere. 57 refs., 14 figs.

  3. The role of latitude in mobilism debates

    PubMed Central

    Irving, Edward

    2005-01-01

    In the early 1920s, the continental displacement theory of Wegener, latitude studies of Köppen and Wegener, and Argand's ideas on mountain building led to the first mobilistic paleogeography. In the 1930s and 1940s, many factors caused its general abandonment. Mobilism was revived in the 1950s and 1960s by measurements of long-term displacement of crustal blocks relative to each other (tectonic displacement) and to Earth's geographic pole (latitudinal displacement). Also, short-term or current displacements can now be measured. I briefly outline the categories of tectonic and current displacement and focus on latitudinal displacement. Integration of tectonic and latitudinal displacement in the early 1970s completed the new mobilistic paleogeography, in which the transformation of rock magnetization directions into paleopoles and latitudes and the finite rotation of spherical plates about pivot points play complementary roles; this new synthesis now provides a quantitative basis for studying long-term evolution of Earth's surface features and climate, the changing environments in which life evolves. PMID:15684058

  4. Shabansky Orbits and High Latitude Chorus

    NASA Astrophysics Data System (ADS)

    McCollough, J. P.; Elkington, S. R.; Malaspina, D.; Spasojevic, M.

    2013-12-01

    High latitude chorus is a whistler-mode VLF emission that is observed on the dayside at high L-shells. Recent observations show presence of these waves in off- equatorial regions. In the presence of off-equatorial magnetic field minima, trapped par- ticles undergo so-called Shabansky orbits, which can lead to temperature anisotropies ooff the equator. Additionally, drift shell splitting (DSS) can produce anisotropies in a compressed dipole. We use a 3D particle tracing code in a tunable analytic compressed- dipole field to study the role of Shabansky orbits on generating a temperature anisotropy in relativistic electrons. By adjusting the dependence on L of the phase space density, we can distinguish between DSS and effects from Shabansky orbits. We use the computed anisotropy for both cases along with a cold plasma model to compute a linear convec- tive wave growth rate for waves in off-equatorial regions. By performing these simula- tions without energizing processes, we can definitively determine what roles Shabansky orbits DSS have in high latitude chorus wave growth. Comparisons of realistic field results with observations will be presented.

  5. Paleogeographic implications of high latitude and middle latitude affinities of the ammonoid Uraloceras

    SciTech Connect

    Spinosa, C.; Gallegos, D.M. ); Nassichuk, W.W. ); Snyder, W.S.

    1991-02-01

    The ammonoid genus Uraloceras characterized a Lower Permian Boreal paleogeographic realm. Reported Lower Permian Pangaean uraloceras occurrences have a Boreal or high-latitude distribution. Additional Lower Permian occurrences in Alaska, dominated by Boreal species, are compatible with and reinforce the Boreal distribution of the genus. In contrast, a new Uraloceras species from Nevada and from the Yukon, as well as representatives of the genus form Nei Monggol, inhabited regions of lower latitudes. The latter ammonoid faunas, geographically and paleoecologically transitional between boreal and equatorial realms, include the genus Uraloceras as well as abundant other ammonoid taxa and representatives of equatorial perinitid ammonoids. The lower assemblage of Wrangellia terrane in eastern Alaska, consisting of the Lower Permian Mankomen Group (Slana Spur and Eagle Creek formations), contains abundant Uraloceras and Paragastrioceras of high-latitude affinities. Published paleomagnetic data indicate that the Nikolai Greenstone is of equatorial origin, with paleolatitudes 10 to 17{degree}. The Nikolai Greenstone seems to have a far-traveled history incompatible with ammonoid evidence suggesting cool-water setting on the Pangaean continental shelf. A reinterpretation for the origin of Wrangellia or its magnetic signature may be in order. Alternative hypotheses suggest that the Eagle Creek Uraloceras-Paragastrioceras Boreal fauna was scraped off the craton at higher latitudes (possible 30-45{degree}) and carried with Wrangellia to its present location.

  6. A high-latitude, low-latitude boundary layer model of the convection current system

    SciTech Connect

    Siscoe, G.L. ); Lotko, W.; Sonnerup, B.U.O. )

    1991-03-01

    Observations suggest that both the high- and low-latitude boundary layers contribute to magnetospheric convection, and that their contributions are linked. In the interpretation pursued here, the high-latitude boundary layer (HBL) generates the voltage while the low-latitude boundary layer (LBL) generates the current for the part of the convection electric circuit that closes through the ionosphere. This paper gives a model that joins the high- and low-latitude boundary layers consistently with the ionospheric Ohm's law. It describes an electric circuit linking both boundary layers, the region 1 Birkeland currents, and the ionospheric Pedersen closure currents. The model works by using the convection electric field that the ionosphere receives from the HBL to determine two boundary conditions to the equations that govern viscous LBL-ionosphere coupling. The result provides the needed self-consistent coupling between the two boundary layers and fully specifies the solution for the viscous LBL-ionosphere coupling equations. The solution shows that in providing the current required by the ionospheric Ohm's law, the LBL needs only a tenth of the voltage that spans the HBL. The solution also gives the latitude profiles of the ionospheric electric field, parallel currents, and parallel potential. It predicts that the plasma in the inner part of the LBL moves sunward instead of antisunward and that, as the transpolar potential decreases below about 40 kV, reverse polarity (region 0) currents appear at the poleward border of the region 1 currents. A possible problem with the model is its prediction of a thin boundary layer ({approximately}1000 km), whereas thicknesses inferred from satellite data tend to be greater.

  7. EGRET sources at intermediate galactic latitude

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P. (Principal Investigator)

    1996-01-01

    This paper presents the abstracts of four papers (using ROSAT data) that are submitted to refereed journals during the current reporting period. The papers are: (1) Extreme x-ray variability in the narrow-line QSO PHL 1092; (2) The Geminga pulsar (soft x-ray variability and an EUVE observation); (3) a broad-band x-ray study of the geminga pulsar; and (4) Classification of IRAS-selected x-ray galaxies in the ROSAT all-sky survey. The abstracts of these papers are given in the next four sections of this report, and their status is given in the Appendix. Finally, two new projects (De-identifying a non-AGN and EGRET sources at intermediate galactic latitude) for which ROSAT data were recently received are currently being studied under this grant. A summary of work in progress on these new projects is given in the last two sections of this report.

  8. Dust transport into Martian polar latitudes

    NASA Technical Reports Server (NTRS)

    Murphy, J. R.; Pollack, J. B.

    1992-01-01

    The presence of suspended dust in the Martian atmosphere, and its return to the planet's surface, is implicated in the formation of the polar layered terrain and the dichotomy in perennial CO2 polar cap retention in the two hemispheres. A three dimensional model was used to study Martian global dust storms. The model accounts for the interactive feedbacks between the atmospheric thermal and dynamical states and an evolving radiatively active suspended dust load. Results from dust storm experiments, as well as from simulations in which there is interest in identifying the conditions under which surface dust lifting occurs at various locations and times, indicate that dust transport due to atmospheric eddy motions is likely to be important in the arrival of suspended dust at polar latitudes. The layered terrain in both polar regions of Mars is interpreted as the reality of cyclical episodes of volatile (CO2, H2O) and dust deposition.

  9. High latitude electromagnetic plasma wave emissions

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.

    1983-01-01

    The principal types of electromagnetic plasma wave emission produced in the high latitude auroral regions are reviewed. Three types of radiation are described: auroral kilometric radiation, auroral hiss, and Z mode radiation. Auroral kilometric radiation is a very intense radio emission generated in the free space R-X mode by electrons associated with the formation of discrete auroral arcs in the local evening. Theories suggest that this radiation is an electron cyclotron resonance instability driven by an enhanced loss cone in the auroral acceleration region at altitudes of about 1 to 2 R sub E. Auroral hiss is a somewhat weaker whistler mode emission generated by low energy (100 eV to 10 keV) auroral electrons. The auroral hiss usually has a V shaped frequency time spectrum caused by a freqency dependent beaming of the whistler mode into a conical beam directed upward or downward along the magnetic field.

  10. Electrodynamics of ionospheric weather over low latitudes

    NASA Astrophysics Data System (ADS)

    Abdu, Mangalathayil Ali

    2016-12-01

    The dynamic state of the ionosphere at low latitudes is largely controlled by electric fields originating from dynamo actions by atmospheric waves propagating from below and the solar wind-magnetosphere interaction from above. These electric fields cause structuring of the ionosphere in wide ranging spatial and temporal scales that impact on space-based communication and navigation systems constituting an important segment of our technology-based day-to-day lives. The largest of the ionosphere structures, the equatorial ionization anomaly, with global maximum of plasma densities can cause propagation delays on the GNSS signals. The sunset electrodynamics is responsible for the generation of plasma bubble wide spectrum irregularities that can cause scintillation or even disruptions of satellite communication/navigation signals. Driven basically by upward propagating tides, these electric fields can suffer significant modulations from perturbation winds due to gravity waves, planetary/Kelvin waves, and non-migrating tides, as recent observational and modeling results have demonstrated. The changing state of the plasma distribution arising from these highly variable electric fields constitutes an important component of the ionospheric weather disturbances. Another, often dominating, component arises from solar disturbances when coronal mass ejection (CME) interaction with the earth's magnetosphere results in energy transport to low latitudes in the form of storm time prompt penetration electric fields and thermospheric disturbance winds. As a result, drastic modifications can occur in the form of layer restructuring (Es-, F3 layers etc.), large total electron content (TEC) enhancements, equatorial ionization anomaly (EIA) latitudinal expansion/contraction, anomalous polarization electric fields/vertical drifts, enhanced growth/suppression of plasma structuring, etc. A brief review of our current understanding of the ionospheric weather variations and the

  11. Revisiting the question: Does high-latitude solar activity lead low-latitude solar activity in time phase?

    SciTech Connect

    Kong, D. F.; Qu, Z. N.; Guo, Q. L.

    2014-05-01

    Cross-correlation analysis and wavelet transform methods are used to investigate whether high-latitude solar activity leads low-latitude solar activity in time phase or not, using the data of the Carte Synoptique solar filaments archive from 1919 March to 1989 December. From the cross-correlation analysis, high-latitude solar filaments have a time lead of 12 Carrington solar rotations with respect to low-latitude ones. Both the cross-wavelet transform and wavelet coherence indicate that high-latitude solar filaments lead low-latitude ones in time phase. Furthermore, low-latitude solar activity is better correlated with high-latitude solar activity of the previous cycle than with that of the following cycle, which is statistically significant. Thus, the present study confirms that high-latitude solar activity in the polar regions is indeed better correlated with the low-latitude solar activity of the following cycle than with that of the previous cycle, namely, leading in time phase.

  12. [Valutazione delle guardie di sicurezza privata attraverso la Suicide Probability Scale e la Brief Symptom Inventory].

    PubMed

    Dogan, Bulent; Canturk, Gurol; Canturk, Nergis; Guney, Sevgi; Özcan, Ebru

    2016-01-01

    RIASSUNTO. Scopo. Lo scopo di questo studio è stato quello di investigare l'influenza della probabilità di suicidio, con le sue caratteristiche sociodemografiche, e di procurare i dati per la prevenzione del suicidio tra le guardie di sicurezza privata che lavorano in condizioni di stress, essendo a contatto ininterrottamente con eventi negativi e traumatici di vita durante il loro lavoro. Metodi. Hanno partecipato allo studio 200 guardie di sicurezza privata e 200 persone dell'Università di Ankara. Per raccogliere i dati sono stati utilizzati un questionario riguardante le condizioni sociodemografiche dei partecipanti, la Suicide Probability Scale (SPS) e la Brief Symptom Inventory (BSI). Risultati. Genere, stato civile, stipendio, credenze religiose, vivere una situazione di pericolo di vita, passato di tentativi di suicidio, fumare e non avere una malattia cronica hanno causato statisticamente una differenza significativa sui punteggi di SPS tra il gruppo di guardie di sicurezza privata e quello di controllo. In aggiunta, c'è stata una correlazione positiva statisticamente significativa tra i punteggi totali delle sottoscale di SPS e quelli di BSI. Conclusioni. Allo stesso modo degli agenti di polizia e dei gendarmi, le guardie di sicurezza privata sono ad alto rischio di commettere e tentare il suicidio trovandosi in condizioni stressanti di lavoro e anche soffrendo del trauma secondario. È necessario che essi siano consapevoli della propria tendenza al suicidio e avere controlli psichiatrici regolari. PMID:27183512

  13. Latitude and local time dependence of precipitated low energy electrons at high latitudes

    NASA Technical Reports Server (NTRS)

    Gustafsson, G.

    1972-01-01

    Data from particle detectors on board the satellite OGO-4 were used to study the precipitation of electrons in the energy range 0.7 to 24 keV. The latitude dependence of these particles in the local time region from midnight to dawn was investigated in detail. The analysis shows that the precipitation of particles of energies 2.3 to 24 keV is centered at an invariant latitude of about 68 deg at midnight with a clear shift in latitude with increasing local time and this shift is more pronounced for lower energies. The highest fluxes of particles in this energy interval are measured at midnight and they decrease rapidly with local time. The data in the energy range 2.3 to 24 keV support a theory where particles are injected in the midnight region from the tail gaining energy due to a betatron process and then drift eastwards in a combined electric and magnetic field. The main part of the electrons at 0.7 keV show a different behavior. They seem to undergo an acceleration process which is rather local, sometimes giving field aligned fluxes which may be super-imposed on the background precipitation.

  14. Reach a New Threshold of Freedom and Control with Dell's Flexible Computing Solution: On-Demand Desktop Streaming

    ERIC Educational Resources Information Center

    Technology & Learning, 2008

    2008-01-01

    When it comes to IT, there has always been an important link between data center control and client flexibility. As computing power increases, so do the potentially crippling threats to security, productivity and financial stability. This article talks about Dell's On-Demand Desktop Streaming solution which is designed to centralize complete…

  15. Viewing Indians: Native Encounters with Power, Tourism, and the Camera in the Wisconsin Dells, 1866-1907

    ERIC Educational Resources Information Center

    Hoelscher, Steven

    2003-01-01

    In the winter of 1883, the photographer H. H. Bennett decided to spice up his descriptive catalogue of stereo views with something new. Several years earlier, a simple listing of his photographs--mostly landscape views of the area surrounding the Wisconsin River Dells--brought the small-town studio photographer considerable renown and enhanced…

  16. 75 FR 57505 - Dell Products LP, Winston-Salem (WS-1) Division, Including On-Site Leased Workers From Adecco...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-21

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF LABOR Employment and Training Administration Dell Products LP, Winston-Salem (WS-1) Division, Including On- Site Leased Workers From Adecco, Spherion, Patriot Staffing, Manpower, Teksystems, APN, ICONMA, Staffing Solutions, South East and OMNI Resources...

  17. 76 FR 27366 - CEVA Freight, LLC, Dell Logistics Division, Including On-Site Leased Workers From Prologistix...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-11

    ... Carolina. The notice was published in the Federal Register on April 23, 2010 (75 FR 21357). The notice was... notice was published in the Federal Register on July 1, 2010 (75 FR 38128-38129). At the request of the... Employment and Training Administration CEVA Freight, LLC, Dell Logistics Division, Including On-Site...

  18. Characteristics of tropopause folds over Arctic latitudes

    NASA Astrophysics Data System (ADS)

    Rao, T. Narayana; Kirkwood, S.

    2005-09-01

    Characteristics of tropopause folds over Arctic latitudes have been studied using VHF radar measurements supplemented by balloon measurements. The variation of the radar parameters during the passage of tropopause folds is discussed in detail. To our knowledge, these observations constitute the first spaced antenna (SA) radar measurements during the passage of tropopause folds. This allows us to compare the parameters detectable using this mode with those observed using other configurations, such as the Doppler beam swinging (DBS) technique. In general, the structural characteristics, such as the slope of folds, seem to be similar at Arctic latitudes to that at midlatitudes; however, the height of the tropopause and the axis of the jet stream (and hence the folding) are found to be lower by 1-2 km than their counterparts in midlatitudes. In the case studies the radar-derived parameters, such as the signal-to-noise ratio (SNR) and vertical shear of horizontal wind, clearly show the upper-air frontal zone. The frontal circulation, conceived from vertical velocity, including the warm conveyer belt flow and the dry intrusion, is clearly visible in the first case, whereas it is masked by high-amplitude mountain lee waves in the second case. Further, the frontal zone seems to be acting as a critical layer to mountain lee wave activity by absorbing/filtering the wave activity. The aspect angles derived from the present analysis agree well with those estimated by vertical beam spectral width but are small in comparison with those estimated by the power ratio method. The mean full correlation analysis (FCA) turbulent velocity is estimated using the ESRAD data obtained during the passage of 15 tropopause folds. The mean eddy diffusion coefficients, Kz, near the tropopause and in the upper portion of the fold, where strong turbulence is seen in case studies, are found to be 3.54 and 6.4 m2 s-1, respectively. Utilizing the mean Kz and the mean ozone gradient (obtained from

  19. Magnetospheric resonances at low and middle latitudes

    NASA Astrophysics Data System (ADS)

    Streltsov, A. V.; Huba, J. D.

    2015-09-01

    We present results from a numerical study of structure and dynamics of dispersive Alfvén waves in the near-Earth magnetosphere containing proton radiation belt (near L = 1.5 dipole magnetic shell). The interest in this problem is motivated by numerous observations of magnetic oscillations with frequencies in the range of 0.1-4.0 Hz detected on the ground at low and middle latitudes. In a number of studies these oscillations interpreted as shear Alfvén waves standing inside the so-called ionospheric Alfvén resonator. We present results from two-dimensional, time-dependent simulations of the reduced two-fluid MHD model performed in the dipole magnetic field geometry with the realistic parameters of the magnetospheric plasma. These simulations show that these pulsations can be produced by the fundamental mode of the global field line resonator, spanning the entire magnetic field line in the low or middle magnetosphere. Simulations also show that even the waves with the highest considered frequencies (2.44 Hz) are not trapped inside the ionospheric resonator. Therefore, if these waves will be generated by some ionospheric source, then they can reach the equatorial magnetosphere and interact with energetic protons in the proton radiation belt.

  20. Magnetospheric Resonances at Low and Middle Latitudes

    NASA Astrophysics Data System (ADS)

    Streltsov, A. V.; Huba, J. D.

    2015-12-01

    We present results from a numerical study of structure and dynamics of dispersive Alfven waves in the near-earth magnetosphere containing proton radiation belt (near L=1.5 dipole magnetic shell). The interest in this problem is motivated by numerous observations of magnetic oscillations with frequencies in the range of 0.1-4.0 Hz detected on the ground at low and middle latitudes. In a number of studies these oscillations interpreted as shear Alfven waves standing inside the so-called ionopspheric Alfven resonator (IAR). We present results from two-dimensional, time dependent simulations of the reduced two-fluid MHD model performed in the dipole magnetic field geometry with the realistic parameters of the magnetospheric plasma. These simulations show that these pulsations can be produced by the fundamental mode of the global field line resonator (FLR), spanning the entire magnetic field line in the low or middle magnetosphere. Simulations also show that even the waves with the highest considered frequencies (2.44 Hz) are not trapped inside the ionospheric resonator. Therefore, if these waves will be generated by some ionospheric source, then they can reach the equatorial magnetosphere and interact with energetic protons in the proton radiation belt.

  1. Relative humidities in mid-latitude contrails

    NASA Astrophysics Data System (ADS)

    Krämer, M.; Kübbeler, M.; Meyer, J.; Schiller, C.; Gayet, J.-F.; Fiebig, M.; Hamburger, Th.; Petzold, A. Minikin (4), A.; Schlager, H.; Voigt, Ch.

    2009-04-01

    Aircraft contrails frequently occur in the upper troposphere. They consist of ice particles having the potential to directly affect the Earth's climate. The frequency, life time, ice crystal size spectra and thus radiative properties of contrails depend strongly on the ambient distribution of the relative humidity with respect to ice (RHi). In air with RHi below 100% contrails are believed to be short-lived, while persistent contrails require an ambient RHi of at least 100% (Gao et al., 2006, Atmospheric Environment). During the mid-latitude aircraft experiments CONCERT 2008 (CONtrail and Cirrus ExpeRimenT, 6 flights), CIRRUS 2006 (1 flight) and PAZI 2003 ('PArtikel und ZIrren', 2 flights), RHi inside of contrails were measured using the high precision Fast In-situ Stratospheric lyman-alpha Hygrometer FISH. We present results from about 1 hour of observation time in 52 contrails during the 9 flights. The peak of the RHi frequency distribution is around 90%, i.e. most of the contrails are observed in subsaturated air. There is indication that the age of the contrails is much larger than expected, implying that, to date, the lifetime of contrails below 100% RHi is underestimated. Further analysis of the observations is needed to confirm/explain these results.

  2. Empirical models of high latitude electric fields

    NASA Technical Reports Server (NTRS)

    Heppner, J. P.

    1976-01-01

    Model cross sections of the high latitude dawn-dusk electric field based on OGO-6 data are presented for the signature profiles, most frequently encountered for both + and -Y orientations of the interplanetary magnetic field. Line integrals give a total potential of 76 keV in each case. To illustrate extremes, examples of model cross-sections with total potentials of 23 keV and 140 keV are also given. Model convection patterns are also presented utilizing OGO-6 data on boundary locations at other magnetic local times. When this information is combined with characteristic field geometries in the region of the Harang discontinuity, and is supplemented by data from Ba+ cloud motions in the polar cap, it becomes possible to construct realistic convection patterns on the nightside which deviate from the usual sun-aligned patterns. The observational models presented are of limited applicability as a consequence of the variability of observed distributions. These limitations are emphasized with particular attention given to several types of recurrent deviations which have not previously been discussed.

  3. Low latitude middle atmosphere ionization studies

    NASA Technical Reports Server (NTRS)

    Bassi, J. P.

    1976-01-01

    Low latitude middle atmosphere ionization was studied with data obtained from three blunt conductivity probes and one Gerdien condenser. An investigation was conducted into the effects of various ionization sources in the 40 to 65 Km altitude range. An observed enhancement of positive ion conductivity taking place during the night can be explained by an atmsopheric effect, with cosmic rays being the only source of ionization only if the ion-ion recombination coefficient (alpha sub i) is small(10 to the -7 power cu cm/s) and varies greatly with altitude. More generally accepted values of alpha sub i ( approximately equal to 3x10 to the -7 power cu cm/s) require an additional source of ionization peaking at about 65 Km, and corresponding approximately to the integrated effect of an X-ray flux measured on a rocket flown in conjunction with the ionization measurements. The reasonable assumption of an alpha sub i which does not vary with altitude in the 50-70 Km range implies an even greater value alpha sub i and a more intense and harder X-ray spectrum.

  4. Bayesian Image Classification At High Latitudes

    NASA Astrophysics Data System (ADS)

    Bulgin, Claire E.; Eastwood, Steinar; Merchant, Chris J.

    2013-12-01

    The European Space Agency created the Climate Change Initiative (CCI) to maximize the usefulness of Earth Observations to climate science. Sea Surface Temperature (SST) is an essential climate variable to which satellite observations make a crucial contribution, and is one of the projects within the CCI program. SST retrieval is dependent on successful cloud clearing and identification of clear-sky pixels over ocean. At high latitudes image classification is more difficult due to the presence of sea-ice. Newly formed ice has a temperature close to the freezing point of water and a dark surface making it difficult to distinguish from open ocean using data at visible and infrared wavelengths. Similarly, melt ponds on the sea-ice surface make image classification more difficult. We present here a three- way Bayesian classifier for the AATSR instrument classifying pixels as ‘clear-sky over ocean', ‘clear-sky over ice' or ‘cloud' using the 0.6, 1.6, 11 and 12 micron channels. We demonstrate the ability of the classifier to successfully identify sea-ice and consider the potential for generating an ice surface temperature record from AATSR which could be extended using data from SLSTR.

  5. Mountains and arid climates of middle latitudes

    SciTech Connect

    Manabe, S.; Broccoli, A.J. )

    1990-01-12

    Simulations from a global climate model with and without orography have been used to investigate the role of mountains in maintaining extensive arid climates in middle latitudes of the Northern hemisphere. Dry climates similar to those observed were simulated over central Asia and western interior North America in the experiment with mountains, whereas relatively moist climates were simulated in these areas in the absence of orography. The experiments suggest that these interior regions are dry because general subsidence and relatively infrequent storm development occur upstream of orographically induced stationary wave troughs. Downstream of these troughs, precipitation-bearing storms develop frequently in association with strong jet streams. In contrast, both atmospheric circulation and precipitation were more zonally symmetric in the experiment without mountains. In addition, orography reduces the moisture transport into the continental interiors from nearby oceanic sources. The relative soil wetness of these regions in the experiment without mountains is consistent with paleoclimatic evidence of less aridity during the late Tertiary, before substantial uplift of the Rocky Mountains and Tibetan Plateau is believed to have occurred.

  6. Nighttime subvisual high-latitude auroras

    NASA Astrophysics Data System (ADS)

    Vorobjev, V. G.; Kornilov, I. A.; Kornilova, T. A.; Yagodkina, O. I.; Sandholt, P. E.; Lybekk, B.

    2008-10-01

    Special methods for processing TV images have been used to study the characteristics of nighttime auroras based on the observations at high-latitude observatories on Spitsbergen. Weak subvisual auroras (SVAs), originating 3°-4° north of brighter auroras in the auroral oval, have been detected in the interval 1900-0400 MLT. The average lifetime of SVAs is approximately 7 min, and the average velocity of the equatorward shift is ˜0.6 km/s. SVAs were observed during relatively quiet periods, when the IMF B z component is mainly positive. However, SVAs are not polar-cap auroras since they are oriented from east to west rather than toward the Sun. The optical observations indicate that the SVA intensity is 0.2-0.5 and 0.1-0.3 kR in the 630 and 557.7 nm emissions, respectively. The average ratio of the emission intensities ( I 5577/ I 6300) is about 0.5. According to the direct satellite observations, the SVA electron spectrum has a maximum at 0.4-1.0 keV. In this case the energy flux of precipitating electrons is approximately an order of magnitude as low as such a flux in brighter auroral arcs in the auroral oval.

  7. Latitude-correlated genetic polymorphisms: selection or gene flow?

    PubMed

    Ciminelli, B M; Jodice, C; Scozzari, R; Corbo, R M; Nahum, M; Pompei, F; Santachiara-Benerecetti, S A; Santolamazza, C; Morpurgo, G P; Modiano, G

    2000-08-01

    Latitude-correlated polymorphisms can be due to either selection-driven evolution or gene flow. To discriminate between them, we propose an approach that studies subpopulations springing from a single population that have lived for generations at different latitudes and have had a low genetic admixture. These requirements are fulfilled to a large extent by Ashkenazi and Sephardi Jews. The original population lived at a latitude of 35 degrees N, where the Sephardis still live. The Ashkenazis, however, moved to a latitude of 50 degrees N, starting about 10 centuries ago. The present study examines 3 latitude-correlated polymorphisms: PGP, PGM1, and AHSG. We found that PGP*2 and AHSG*2 alleles most likely underwent selection-driven evolution, but that PGM1*ts allele was not similarly affected. Since temperature might have been considered a reasonable selective factor, we also studied a population living at >800 m above sea level from Aosta Valley (Italy). PMID:11048786

  8. Latitude: How American Astronomers Solved the Mystery of Variation

    NASA Astrophysics Data System (ADS)

    Ray, Richard D.

    First longitude, now latitude. From Latitude's title we cannot help thinking of Dava Sobel's recent bestseller, Longitude. I suppose it's unlikely to be such a moneymaker, but this delightful new book by Bill and Merri Sue Carter, a father and daughter team, is similar to Sobel's book. Both are physically small, with short chapters, which makes for a quick read. And both have a clear hero: John Harrison and his chronometers for longitude; and Seth Carlo Chandler Jr. and his almucantar for latitude. Both books eschew academic-style footnoting, although Latitude does list a few useful sources for each chapter and provides a comprehensive list of Chandler's astronomical publications. Chandler's name is known to most AGU members for its association with the 14-month wobble of the Earth's pole. He also discovered the slightly smaller annual wobble, and an argument can be made that he was the principal discoverer of polar motion, or latitude variation, in general.

  9. Motion of the Heliospheric Termination Shock at High Heliographic Latitude

    NASA Technical Reports Server (NTRS)

    Barnes, Aaron

    1995-01-01

    We expect the mean distance of the heliospheric termination shock to be greater (smaller) at polar latitudes than at equatorial latitudes, depending on whether the mean dynamic pressure of the solar wind is greater or smaller at high latitudes. The heliospheric termination shock is expected to move in response to variation in upstream solar wind conditions, so that at any particular instant the termination shock will resemble a distorted asymmetric balloon with some parts moving inward and others moving outward. If the shock is a gasdynamic or magnetohydrodynamic shock the results of the analysis depend only very weakly on the nature of the upstream disturbance; typical speeds of the disturbed shock are approximately 100 to 200 km/s. In the absence of a significant latitude gradient of the typical magnitude of solar wind disturbances typical motions of the disturbed shock at polar latitudes would be about twice as fast, due to the higher speed of the high-latitude wind. If the dynamics of the termination shock are dominated by acceleration of the anomalous component of the cosmic rays, the motion of the shock in response to a given disturbance is substantially slower than in the gasdynamic case. Conceivably, particle acceleration might be a less important effect at higher latitudes, and we envision the possibility of a termination shock that is dominated by particle acceleration at lower latitudes and is an MHD shock at high latitudes. In this event high latitude solar wind disturbances would produce substantially larger inward and outward motions of the shock in the polar regions.

  10. Common origin of positive ionospheric storms at middle latitudes and the geomagnetic activity effect at low latitudes

    SciTech Connect

    Proelss, G.W. )

    1993-04-01

    The author looks for a correlation between two different atmospheric effects. They are a positive atmospheric storm (an anomalous increase in the F2 region ionization density), observed at middle latitudes, and the geomagnetic activity effect (the anomalous changes of temperature and gas density seen in the thermosphere), observed at low latitudes. A temporal correlation is sought to test the argument that both of these effects are the result of travelling atmospheric disturbances (TAD). A TAD is a pulselike atmospheric wave thought to be generated by substorm activity, and to propagate with high velocity (600 m/s) from polar latitudes toward equatorial latitudes. The author looks at data from five separate events correlating magnetic, ionospheric, and neutral atmospheric measurements. The conclusion is that there is a positive correlation between magnetic substorm activity at high latitudes, and positive ionospheric storms at middle latitudes and geomagnetic activity at low latitudes. The time correlations are consistent with high propagation speeds between these events. The author also presents arguments which indicate that the middle latitude positive ionospheric storms are not the result of electric field effects.

  11. Carbon cycling in high-latitude ecosystems

    NASA Technical Reports Server (NTRS)

    Townsend, Alan; Frolking, Stephen; Holland, Elizabeth

    1992-01-01

    The carbon-rich soils and peatlands of high-latitude ecosystems could substantially influence atmospheric concentrations of CO2 and CH4 in a changing climate. Currently, cold, often waterlogged conditions retard decomposition, and release of carbon back to the atmosphere may be further slowed by physical protection of organic matter in permafrost. As a result, many northern ecosystems accumulate carbon over time (Billings et al., 1982; Poole and Miller, 1982), and although such rates of accumulation are low, thousands of years of development have left Arctic ecosystems with an extremely high soil carbon content; Schlesinger's (1984) average value of 20.4 kg C/m(sup 2) leads to a global estimate of 163 x 10(exp 15) g C. All GCM simulations of a doubled CO2 climate predict the greatest warming to occur in the polar regions (Dickinson, 1986; Mitchell, 1989). Given the extensive northern carbon pools and the strong sensitivity of decomposition processes to temperature, even a slight warming of the soil could dramatically alter the carbon balance of Arctic ecosystems. If warming accelerates rates of decomposition more than rates of primary production, a sizeable additional accumulation of CO2 in the atmosphere could occur. Furthermore, CH4 produced in anaerobic soils and peatlands of the Arctic already composes a good percentage of the global efflux (Cicerone and Oremlund, 1988); if northern soils become warmer and wetter as a whole, CH4 emissions could dramatically rise. A robust understanding of the primary controls of carbon fluxes in Arctic ecosystems is critical. As a framework for a systematic examination of these controls, we discussed a conceptual model of regional-scale Arctic carbon turnover, including CH4 production, and based upon the Century soil organic matter model.

  12. Storm time electric field penetration observed at mid-latitude

    SciTech Connect

    Yeh, H.C.; Foster, J.C. ); Rich, F.J.; Swider, W. )

    1991-04-01

    During the height of the February 8-9, 1986, magnetic storm the Millstone Hill radar was in the evening local time sector (1600-2200 MLT). Radar observations indicate that high speed (>1,000 m s{sup {minus}1}) westward ion flow penetrated deeply below 50{degree} invariant latitude ({Lambda}) and persisted for 6 hours between 2100 UT on February 8 and 0300 UT on February 9. The double-peaked ion convection feature was pronounced throughout the period, and the separation in the dual maxima ranged from 4{degree} to 10{degree}. The latitude positions of the high-latitude ion drift peak and the convection reversal varied in unison. The low-latitude ion drift peak ({approximately}49{degree}{Lambda} or L =2.3) did not show significant universal time/magnetic local time (UT/MLT) variation in its latitude location but showed a decrease in magnitude during the initial recovery phase of the storm. Using simultaneous particle (30 eV-30 keV) precipitation data from the DMSP F6 and F7 satellites, the authors find the high-latitude ion drift peak to coincide with the boundary plasma sheet/central plasma sheet transition in the high ionospheric conductivity (>15 mho) region. The low-latitude ion drift peak lay between the equatorward edges of the electron and soft (< 1 keV) ion precipitation in the low conductivity region ({approximately}1 mho). A comparison between the low-altitude observations and simultaneous ring current observations from the high-altitude AMPTE satellite further suggests that the low-altitude ion drift peak is closely related to the maximum of the O{sup +} dominated ring current energy density in magnetic latitude. The low-latitude ion drift peak is the low-altitude signature of the electric field shielding effect associated with ring current penetration into the outer layer of the storm time plasmasphere.

  13. Ion temperature of low-latitude and mid-latitude topside ionosphere for high solar activity

    NASA Astrophysics Data System (ADS)

    Cai, Lei; Zhang, Donghe; Hao, Yongqiang; Xiao, Zuo

    The International Reference Ionosphere (IRI) describes the day and night latitudinal variation of ion temperature at 430 km with two functions using AEROS satellite measurements. The ion temperature at this height as one of the boundary parameters is used to make the ion temperature profile represented by a Booker-function. Since the low-latitude and mid-latitude topside ionospheric ion temperature has been measured with the Ionopsheric Plasma and Elec-trodynamics Instrument (IPEI) onboard Rocsat-1 satellite at about 600 km during the high solar activity years from 2000 to 2002, a new boundary at 600 km can be set for the ion temperature modeling. The latitudinal variation of ion temperature could be approximated by Epstein family of functions for different local time sectors. Furthermore, the longitudinal and seasonal variations are also taken into account to decide the fitting parameters. Only the magnetic quiet time data (Kp <3) are used for the statistical study. The results are compared with IRI-2007 model. In addition, events when Kp >4 are also analyzed to feature the ion temperature characteristic during the magnetic disturbance time condition. Combined with the IPEI field-aligned ion flow velocities and the plasma temperatures measured by the Special Sensors-Ions, Electrons, and Scintillation (SSIES) thermal plasma analysis package on board the DMSP F13 and F15 satellites, several feasible ion heating and heat loss mechanisms are summarized to interpret the ion temperature crests and toughs for different local time sectors, seasonal and longitudinal variations.

  14. Testing IRI-PLAS STEC Calculations Performance for Different Latitudes

    NASA Astrophysics Data System (ADS)

    Scidá, Luis

    2016-07-01

    Predicted values of slant total electron content (STEC) by IRI Plas have been compared to experimental data derived from Geostationary satellites for the North American sector and low latitude and equatorial regions. The results reveal that IRI-Plas gives good calculations for the North American sector and significant deviations for low latitude regions. The deviations can be due to the fact that IRI-Plas does not represent correctly the electron density topside profile and also the CCIR map, used by IRI for calculations, has much less data from equatorial and low latitude regions than to the North American sector where there is a higher density of sounding stations.

  15. Latitude dependence of co-rotating shock acceleration

    NASA Technical Reports Server (NTRS)

    Gold, R. E.; Lanzerotti, L. J.; Maclennan, C. G.; Krimigis, S. M.

    1985-01-01

    Energetic particle observations in the outer heliosphere (approx 12 A. U.) by the LECP instruments on the Voyager 1 and Voyager 2 spacecraft are discussed that show a definite latitude dependence of the number and intensity of particle enhancements produced by corotating interplanetary regions during an interval when no solar energetic particle events were observed. The particle enhancements are fewer in number and less intense at higher (approx 20 deg.) heliolatitudes. However, the similar spectral shapes of the accelerated particles at the two spacecraft indicate that the acceleration process is the same at the two latitudes, but less intense at the higher latitude.

  16. Quiet geomagnetic field representation for all days and latitudes

    USGS Publications Warehouse

    Campbell, W.H.; Schiffmacher, E.R.; Arora, B.R.

    1992-01-01

    Describes a technique for obtaining the quiet-time geomagnetic field variation expected for all days of the year and distribution of latitudes from a limited set of selected quiet days within a year at a discrete set of locations. A data set of observatories near 75??E longitude was used as illustration. The method relies upon spatial smoothing of the decomposed spectral components. An evaluation of the fidelity of the resulting model shows correlation coefficients usually above 0.9 at the lower latitudes and near 0.7 at the higher latitudes with variations identified as dependent upon season and field element. -from Authors

  17. Effect of high latitude filtering on NWP skill

    NASA Technical Reports Server (NTRS)

    Kalnay, E.; Takacs, L. L.; Hoffman, R. N.

    1984-01-01

    The high latitude filtering techniques commonly employed in global grid point models to eliminate the high frequency waves associated with the convergence of meridians, can introduce serious distortions which ultimately affect the solution at all latitudes. Experiments completed so far with the 4 deg x 5 deg, 9-level GLAS Fourth Order Model indicate that the high latitude filter currently in operation affects only minimally its forecasting skill. In one case, however, the use of pressure gradient filter significantly improved the forecast. Three day forecasts with the pressure gradient and operational filters are compared as are 5-day forecasts with no filter.

  18. Ultraviolet spectrum of the sky background at different galactic latitudes

    NASA Astrophysics Data System (ADS)

    Zvereva, A. M.; Severnyi, A. B.; Granitskii, L. V.; Hua, C. T.; Cruvellier, P.; Courtes, G.

    1982-12-01

    The intensity distributions of the sky background radiation in the 1100-1850 A range were measured in deep space (70,000-200,000 km from the earth) by the Prognoz-6 photoelectric spectrometer. Spectral distributions of UV background Ilambda, after subtraction of the stellar component, vary with galactic latitude in the range bII equals minus 58 to plus 27 deg. Ilambda decreases with increasing wavelength at high latitudes; the spectrum then becomes flat at intermediate latitudes, and there is a rapid decrease of Ilambda with lambda near and inside the Milky Way. The intensity I(lambda equals 1600) in the higher latitude range (the absolute value of bII higher than 30 deg) shows good correlation with soft X-ray brightness and neutral hydrogen (21-cm) density N(H I). However, there is appreciable UV emission near the galactic poles where N(H I) is approximately zero

  19. Low-Dimensional Chaos of High-Latitude Solar Activity

    NASA Astrophysics Data System (ADS)

    Li, Qi-Xiu; Li, Ke-Jun

    2007-10-01

    The chaos of high-latitude solar activity has been investigated by determining the behavior of the monthly averaged polar facula counts obtained from the National Astronomical Observatory of Japan (NAOJ) on the basis of nonlinear dynamics theories and methods. It is found that the high-latitude solar activity is also governed by a low-dimensional chaotic attractor in both the northern and southern solar hemispheres, which is the same as that of the low-latitude solar activity. However, their maximal Lyapunov exponents are different, showing different strength of chaos. The maximal Lyapunov exponent (MLE) of polar faculae in the southern solar hemisphere is about 0.0211 ± 0.0003 (month-1), which is nearly consistent with the low-latitude Wolf sunspot numbers, while the MLE in the northern one is approximately 0.0944 ± 0.0066 (month-1), which is obviously greater than the above two.

  20. Mapping high-latitude plasma convection with coherent HF radars

    NASA Technical Reports Server (NTRS)

    Ruohoniemi, J. M.; Greenwald, R. A.; Baker, K. B.; Villain, J.-P.; Hanuise, C.

    1989-01-01

    Several methods developed for mapping high-latitude plasma convection with a high-latitude HF radar are described, which utilize coherent backscatter from electron density irregularities at F-region altitudes to observe convective plasma motion. Several examples of two-dimensional convection-velocity maps are presented, showing instances of L-shell-aligned flow in the dusk sector, the reversal of convection near magnetic midnight, and counterstreaming in the dayside cleft.

  1. Dependence of the charge exchange lifetimes on mirror latitude

    NASA Technical Reports Server (NTRS)

    Smith, P. H.; Bewtra, N. K.

    1976-01-01

    The dependence of the charge exchange lifetimes on the mirror latitude for ions mirroring off the geomagnetic equator was re-computed using the improved hydrogen distribution models. The Chamberlain model was used to define the spatial distribution of the neutral hydrogen environment through which the ring current ions traverse. The resultant dependence of the charge exchange lifetime on mirror latitude is best fitted by the approximation that contains the charge exchange lifetime for equatorial particles.

  2. Cosmology with the WFIRST High Latitude Survey

    NASA Astrophysics Data System (ADS)

    Dore, Olivier

    Cosmic acceleration is the most surprising cosmological discovery in many decades. Testing and distinguishing among possible explanations requires cosmological measurements of extremely high precision that probe the full history of cosmic expansion and structure growth. The WFIRST-AFTA mission, as described in the Science Definition Team (SDT) reports (Spergel 2013, 2015), has the ability to improve these measurements by 1-2 orders of magnitude compared to the current state of the art, while simultaneously extending their redshift grasp, greatly improving control of systematic effects, and taking a unified approach to multiple probes that provide complementary physical information and cross-checks of cosmological results. We have assembled a team with the expertise and commitment needed to address the stringent challenges of the WFIRST dark energy program through the Project's formulation phase. After careful consideration, we have elected to address investigations A (Galaxy Redshift Survey) and C (Weak Lensing and Cluster Growth) of the WFIRST SIT NRA with a unified team, because the two investigations are tightly linked at both the technical level and the theoretical modeling level. The imaging and spectroscopic elements of the High Latitude Survey (HLS) will be realized as an integrated observing program, and they jointly impose requirements on instrument and telescope performance, operations, and data transfer. The methods for simulating and interpreting weak lensing and galaxy clustering observations largely overlap, and many members of our team have expertise in both areas. The team PI, Olivier Dore, is a cosmologist with a broad expertise in cosmic microwave background and large scale structures. Yun Wang and Chris Hirata will serve as Lead Co-Investigators for topics A and C, respectively. Many members of our team have been involved with the design and requirements of a dark energy space mission for a decade or more, including the Co-Chair and three

  3. 77 FR 10800 - Requested Administrative Waiver of the Coastwise Trade Laws: Vessel ALTERNATE LATITUDE...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-23

    ... LATITUDE; Invitation for Public Comments AGENCY: Maritime Administration, Department of Transportation... applicant the intended service of the vessel ALTERNATE LATITUDE is: Intended Commercial Use of...

  4. Space weather and myocardial infarction diseases at subauroral latitudes

    NASA Astrophysics Data System (ADS)

    Samsonov, Sergey; Kleimenova, Natalia; Petrova, Palmira

    The relationship of the number of calls for the emergency medical care in Yakutsk (subauroral latitudes) in connection with myocardial infarction diseases during years near the maximum (1992) and minimum (1998) of the 11-year geomagnetic disturbance cycle to space weather parameters has been studied. It is found that at subauroral latitudes, the increase of geomagnetic activity, namely, the occurrence of night magnetospheric substorms, plays the important role in the exacerbation of myocardial infarctions. Substorms are accompanied by Pi1 irregular geomagnetic pulsations with periods of (0.5-3.0) Hz, coinciding with heart rhythms of a human being, thus, these waves can be a biotropic factor negatively influencing on the occurrence of myocardial infarctions. The comparison of seasonal change of the number of calls for emergency medical care to patients at subauroral latitudes with a simultaneous seasonal change of fatal endings because of an infarction at low latitudes (Bulgaria) has shown their essential difference. Thus, in Bulgaria the maximum of infarctions have been marked in winter, and minimum - in summer, and in Yakutsk a few maxima coinciding with the sharp and considerable increases of the level of the planetary geomagnetic disturbances have been observed. In this case, in Bulgaria the infarctions could be connected with availability of the Pc1 geomagnetic pulsations. Thus, the stable quasi-sinusoidal Pc1 pulsations can be a biotropic factor influencing on the development of myocardial infarctions at middle latitudes and the Pi1 irregular geomagnetic pulsations, which do not propagate to the lower latitudes, could be a biotropic factor at subauroral latitudes.

  5. Storm time plasma transport at middle and high latitudes

    SciTech Connect

    Foster, J.C. )

    1993-02-01

    Associated with the large-scale enhancement of the ionospheric convection electric field during disturbed geomagnetic conditions, solar-produced F region plasma is transported to and through the noontime cleft from a source region at middle and low latitudes in the afternoon sector. As a result of the offset between the geomagnetic and geographic poles, the afternoon sector region of strong sunward convection is shifted to increasingly lower geographic latitude throughout the interval between 12 UT and 24 UT. A snowplow effect occurs in which the convection cell continually encounters fresh corotating ionospheric plasma along its equatorward edge, producing a latitudinally narrow region of storm-enhanced plasma density (SED) and increased total electron content which is advected toward higher latitudes in the noon sector. The Millstone Hill incoherent scatter radar regularly observes SED as a spatially continuous, large-scale feature spanning local times between noon and midnight and at latitudes between the polar cap and its mid- or low-latitude source region. For local times away from noon, the latitude of most probable SED occurrence moves equatorward by 6[degrees] for an increase of 2 in the Kp index. During strong disturbances the topside SED is observed to be convecting sunward at [approximately]750 m s[sup [minus]1] with a flux of 10[sup 14] m[sup [minus]2] s[sup [minus]1]. This feature accounts for the pronounced enhancement of ionospheric density near dusk at middle latitudes observed during the early stages of magnetic storms (called the dusk effect) and constitutes a source for the enhanced F region plasma observed in the polar cap during disturbed conditions. 34 refs., 13 figs., 1 tab.

  6. Climate response to imposed solar radiation reductions in high latitudes

    NASA Astrophysics Data System (ADS)

    MacCracken, M. C.; Shin, H.-J.; Caldeira, K.; Ban-Weiss, G. A.

    2012-07-01

    Increasing concentrations of greenhouse gases are the primary contributor to the 0.8 °C increase in the global average temperature since the late 19th century, shortening cold seasons and lengthening warm seasons. The warming is amplified in polar regions, causing retreat of sea ice, snow cover, permafrost, mountain glaciers, and ice sheets, while also modifying mid-latitude weather, amplifying global sea level rise, and initiating high-latitude carbon feedbacks. Model simulations in which we reduced solar insolation over high latitudes not only cooled those regions, but also drew energy from lower latitudes, exerting a cooling influence over much of the hemisphere in which the reduction was imposed. Our simulations, which used the National Center for Atmospheric Research's CAM3.1 atmospheric model coupled to a slab ocean, indicated that, on a normalized basis, high-latitude reductions in absorbed solar radiation have a significantly larger cooling influence than equivalent solar reductions spread evenly over the Earth. This amplified influence occurred because high-latitude surface cooling preferentially increased sea ice fraction and, therefore, surface albedo, leading to a larger deficit in the radiation budget at the top of the atmosphere than from an equivalent global reduction in solar radiation. Reductions in incoming solar radiation in one polar region (either north or south) resulted in increased poleward energy transport during that hemisphere's cold season and shifted the Inter-Tropical Convergence Zone (ITCZ) away from that pole, whereas equivalent reductions in both polar regions tended to leave the ITCZ approximately in place. Together, these results suggest that, until emissions reductions are sufficient to limit the warming influence of greenhouse gas concentrations, polar reductions in solar radiation, if they can be efficiently and effectively implemented, might, because of fewer undesirable side effects than for global solar radiation reductions

  7. High-latitude dust in the Earth system

    NASA Astrophysics Data System (ADS)

    Bullard, Joanna E.; Baddock, Matthew; Bradwell, Tom; Crusius, John; Darlington, Eleanor; Gaiero, Diego; Gassó, Santiago; Gisladottir, Gudrun; Hodgkins, Richard; McCulloch, Robert; McKenna-Neuman, Cheryl; Mockford, Tom; Stewart, Helena; Thorsteinsson, Throstur

    2016-06-01

    Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high-latitude (≥50°N and ≥40°S) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo-aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high-nutrient, low-chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high-latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year-round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high-latitude sources cover >500,000 km2 and contribute at least 80-100 Tg yr-1 of dust to the Earth system (~5% of the global dust budget); both are projected to increase under future climate change scenarios.

  8. AN ABSENCE OF FAST RADIO BURSTS AT INTERMEDIATE GALACTIC LATITUDES

    SciTech Connect

    Petroff, E.; Van Straten, W.; Bailes, M.; Barr, E. D.; Coster, P.; Flynn, C.; Keane, E. F.; Johnston, S.; Bates, S. D.; Keith, M. J.; Kramer, M.; Stappers, B. W.; Bhat, N. D. R.; Burgay, M.; Possenti, A.; Tiburzi, C.; Burke-Spolaor, S.; Champion, D.; Ng, C.; Levin, L.; and others

    2014-07-10

    Fast radio bursts (FRBs) are an emerging class of bright, highly dispersed radio pulses. Recent work by Thornton et al. has revealed a population of FRBs in the High Time Resolution Universe (HTRU) survey at high Galactic latitudes. A variety of progenitors have been proposed, including cataclysmic events at cosmological distances, Galactic flare stars, and terrestrial radio frequency interference. Here we report on a search for FRBs at intermediate Galactic latitudes (–15° latitudes. A revised rate estimate or another strong and heretofore unknown selection effect in Galactic latitude would provide closer agreement between the surveys' detection rates. The dearth of detections at low Galactic latitude disfavors a Galactic origin for these bursts.

  9. An Absence of Fast Radio Bursts at Intermediate Galactic Latitudes

    NASA Astrophysics Data System (ADS)

    Petroff, E.; van Straten, W.; Johnston, S.; Bailes, M.; Barr, E. D.; Bates, S. D.; Bhat, N. D. R.; Burgay, M.; Burke-Spolaor, S.; Champion, D.; Coster, P.; Flynn, C.; Keane, E. F.; Keith, M. J.; Kramer, M.; Levin, L.; Ng, C.; Possenti, A.; Stappers, B. W.; Tiburzi, C.; Thornton, D.

    2014-07-01

    Fast radio bursts (FRBs) are an emerging class of bright, highly dispersed radio pulses. Recent work by Thornton et al. has revealed a population of FRBs in the High Time Resolution Universe (HTRU) survey at high Galactic latitudes. A variety of progenitors have been proposed, including cataclysmic events at cosmological distances, Galactic flare stars, and terrestrial radio frequency interference. Here we report on a search for FRBs at intermediate Galactic latitudes (-15° latitudes. A revised rate estimate or another strong and heretofore unknown selection effect in Galactic latitude would provide closer agreement between the surveys' detection rates. The dearth of detections at low Galactic latitude disfavors a Galactic origin for these bursts.

  10. High-latitude upgrade to the Wideband ionospheric scintillation model

    NASA Astrophysics Data System (ADS)

    Secan, J. A.; Bussey, R. M.; Fremouw, E. J.; Basu, S.

    1997-07-01

    The high-latitude sections of the Wideband ionospheric scintillation model (WBMOD) have been upgraded extensively, based on analysis of scintillation data from the Defense Nuclear Agency Wideband, HiLat, and Polar BEAR satellite-beacon experiments. Data collected at Sondre Stromfjord, Greenland; Tromso, Norway; Fort Churchill, Canada; and Bellevue, Washington (United States) over a 4-year period were analyzed, and the results of these analyses were used to construct a completely new model for the behavior of the height-integrated irregularity-strength parameter (CkL) at high latitudes. The new high-latitude CkL model includes variations with sunspot number, geomagnetic activity (Kp), latitude, local time, longitude, and season. The new WBMOD CkL models (equatorial and high-latitude) have been implemented in a more versatile code, denoted SCINTMOD, which has the capability to generate a wide range of user-controlled maps of scintillation effects over large spatial areas. Examples of the types of graphical output that SCINTMOD can generate are presented.

  11. Spectral losses of high concentrator photovoltaic modules depending on latitude

    NASA Astrophysics Data System (ADS)

    Soria-Moya, Alberto; Fernández, Eduardo F.; Almonacid, Florencia; Mallick, Tapas K.

    2015-09-01

    High concentrator photovoltaic (HCPV) modules and systems are affected by changes on the incident solar spectrum. It is well known that among all the atmospheric parameters, the air mass has the largest impact on the spectral behavior of HCPV devices. The air mass can be considered as a geometrical parameter which depends entirely on the Sun's zenith angle (θ). Because of this, the yield of HCPV modules is affected by latitude. In this paper, a new method to estimate the gains/losses of energy due to the spectral impact has been introduced. Furthermore, the annual spectral losses depending on latitude have been calculated for several theoretical modules. For default values defined in the standard AM1.5d ASTM G-173-03 spectrum, results show that the spectral losses are almost independent of latitude for locations with low latitude values. Losses between 3% and 5% on the annual energy yield have been estimated for those areas. For high latitudes, the losses increase until they reach values between 10% and 14%. Results depend on the multi-junction solar cells and optical devices of the HCPV module considered.

  12. Polarization characteristics of hydromagnetic waves at low geomagnetic latitudes

    NASA Technical Reports Server (NTRS)

    Lanzerotti, L. J.; Medford, L. V.; Maclennan, C. G.; Hasegawa, T.; Acuna, M. H.; Dolce, S. R.

    1981-01-01

    A field campaign, using three magnetometer stations spaced in latitude around the equatorial magnetic field distance L approximately 1.9, was conducted in early 1979 to investigate the polarization characteristics of hydromagnetic waves at low geomagnetic latitudes. The magnetic pulsations are observed to have periods in the range approximately 20-25 s and to occur primarily in the local morning hours. Statistically, the polarizations at all three stations were predominantly left handed in the local morning hours and right handed in the local afternoon. At the highest-latitude station (L approximately 2) the orientation of the major axis of the polarization ellipse changed from a predominantly NW-SE direction in the local morning to a mixed NW-SE/NE-SW direction in the afternoon. These two statistical results are consistent with the excitation of the waves by the Kelvin-Helmholtz instability at the magnetopause. However, frequent changes in phase are often observed in the magnetic variations, which result in polarization variations on the time scale of minutes, a situation not readily reconcilable with the Kelvin-Helmholtz instability. The existence of the waves at very low latitudes, furthermore, places constraints on the damping rate of externally excited surface waves inside the magnetosphere. We conclude that present theories for hydromagnetic waves in the geomagnetosphere cannot readily incorporate all of these low-latitude results.

  13. Map of Martian Thorium at Mid-Latitudes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This gamma ray spectrometer map of the mid-latitude region of Mars is based on gamma-rays from the element thorium. Thorium is a naturally radioactive element that exists in rocks and soils in extremely small amounts. The region of highest thorium content, shown in red, is found in the northern part of Acidalia Planitia (50 degrees latitude, -30 degrees longitude). Areas of low thorium content, shown in blue, are spread widely across the planet with significant low abundances located to the north of Olympus Mons (near 55 degrees latitude, -155 degrees longitude), to the east of the Tharsis volcanoes (-10 degrees latitude, -80 degrees longitude) and to the south and east of Elysium Mons (20 degrees latitude, 160 degrees longitude). Contours of constant surface elevation are also shown. The long continuous contour line running from east to west marks the approximate separation of the younger lowlands in the north from the older highlands in the south.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The gamma ray spectrometer was provided by the University of Arizona, Tucson. Lockheed Martin Astronautics, Denver, Colo., is the prime contractor for the project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  14. CORAL REEFS. Genomic determinants of coral heat tolerance across latitudes.

    PubMed

    Dixon, Groves B; Davies, Sarah W; Aglyamova, Galina A; Meyer, Eli; Bay, Line K; Matz, Mikhail V

    2015-06-26

    As global warming continues, reef-building corals could avoid local population declines through "genetic rescue" involving exchange of heat-tolerant genotypes across latitudes, but only if latitudinal variation in thermal tolerance is heritable. Here, we show an up-to-10-fold increase in odds of survival of coral larvae under heat stress when their parents come from a warmer lower-latitude location. Elevated thermal tolerance was associated with heritable differences in expression of oxidative, extracellular, transport, and mitochondrial functions that indicated a lack of prior stress. Moreover, two genomic regions strongly responded to selection for thermal tolerance in interlatitudinal crosses. These results demonstrate that variation in coral thermal tolerance across latitudes has a strong genetic basis and could serve as raw material for natural selection. PMID:26113720

  15. Pc 3 pulsation eigenperiod determination at low latitudes

    SciTech Connect

    Hattingh, S.K.F.; Sutcliffe, P.R. )

    1987-11-01

    A realistic method of calculating the eigenperiod of Pc 3 pulsations at low latitudes is discussed. Solution of the problem requires a magnetic field model and a model for the plasma distribution along the resonating field line. The calculated eigenperiods obtained using the dipole field model and the IGRF model are found to be similar. The inclusion of the F region O{sup +} in the plasma distribution noticeably affects the calculated eigenperiod at low latitudes. This effect decreases with increasing L value. Pulsation periods obtained from recordings made at four stations lying on a geomagnetic meridian demonstrate the importance of including O{sup +} in the plasma model if realistic periods are to be calculated at low latitudes.

  16. Sea Ice, High-Latitude Convection, and Equable Climates

    NASA Astrophysics Data System (ADS)

    Abbot, D. S.; Tziperman, E.

    2007-12-01

    It is argued that deep atmospheric convection might occur during winter in ice-free high-latitude oceans, and that the surface radiative warming effects of the clouds and water vapor associated with this winter convection could keep high-latitude oceans ice-free through polar night. In such an ice-free high-latitude ocean the annual-mean SST would be much higher and the seasonal cycle would be dramatically reduced - making potential implications for equable climates manifest. The constraints that atmospheric heat transport, ocean heat transport, and CO2 concentration place on this mechanism are established. These ideas are investigated using a column model with state-of-the-art atmospheric physics, high vertical resolution, a full seasonal cycle, a thermodynamic sea ice model, and a mixed layer ocean (the SCAM).

  17. Heliomagnetic latitude dependence of the heliospheric magnetic field

    NASA Astrophysics Data System (ADS)

    Burton, M. E.; Smith, E. J.; Balogh, A.; Murphy, N.

    1996-07-01

    ICE and IMP-8 magnetic field data from 1984-1988 have been analyzed in a magnetic coordinate system defined by the orientation of the solar magnetic dipole. The heliomagnetic latitude dependence of the radial component of the magnetic field (Br) has then been investigated in a wide range of magnetic latitudes above and below the heliospheric current sheet (HCS). Br reverses sign abruptly across the current sheet, consistent with the solar magnetic field models of Pneuman and Kopp [1971] and Wolfson [1985] but inconsistent with the source surface models [Hoeksema, 1986]. No evidence is found for an asymmetry in the magnetic field suggested by earlier studies of interplanetary magnetic field data [Luhmann, 1987, Burton, 1990]. A slight (~.03 nT per degree) latitude gradient has been found which is consistent with the MHD model of Pneuman and Kopp and the recent model of Zhao and Hoeksema [1995].

  18. The Progress of Solar Cycle 24 at High Latitudes

    NASA Astrophysics Data System (ADS)

    Altrock, R. C.

    2010-06-01

    The "extended" solar cycle 24 began in 1999 near 70° latitude, similarly to cycle 23 in 1989 and cycle 22 in 1979. The extended cycle is manifested by persistent Fe XIV coronal emission appearing near 70° latitude and slowly migrating towards the equator, merging with the latitudes of sunspots and active regions (the "butterfly diagram") after several years. Cycle 24 began its migration at a rate 40% slower than the previous two solar cycles, thus indicating the possibility of a peculiar cycle. However, the onset of the "Rush to the Poles" of polar crown prominences and their associated coronal emission, which has been a precursor to solar maximum in recent cycles (cf. Altrock 2003), has just been identified in the northern hemisphere. Peculiarly, this "rush" is leisurely, at only 50% of the rate in the previous two cycles. The properties of the current "Rush to the Poles" yields an estimate of 2013 or 2014 for solar maximum.

  19. Understanding the Relation between Attitude Involvement and Response Latitude Using Item Response Theory

    ERIC Educational Resources Information Center

    Lake, Christopher J.; Withrow, Scott; Zickar, Michael J.; Wood, Nicole L.; Dalal, Dev K.; Bochinski, Joseph

    2013-01-01

    Adapting the original latitude of acceptance concept to Likert-type surveys, response latitudes are defined as the range of graded response options a person is willing to endorse. Response latitudes were expected to relate to attitude involvement such that high involvement was linked to narrow latitudes (the result of selective, careful…

  20. THEORY OF SOLAR MERIDIONAL CIRCULATION AT HIGH LATITUDES

    SciTech Connect

    Dikpati, Mausumi; Gilman, Peter A. E-mail: gilman@ucar.edu

    2012-02-10

    We build a hydrodynamic model for computing and understanding the Sun's large-scale high-latitude flows, including Coriolis forces, turbulent diffusion of momentum, and gyroscopic pumping. Side boundaries of the spherical 'polar cap', our computational domain, are located at latitudes {>=} 60 Degree-Sign . Implementing observed low-latitude flows as side boundary conditions, we solve the flow equations for a Cartesian analog of the polar cap. The key parameter that determines whether there are nodes in the high-latitude meridional flow is {epsilon} = 2{Omega}n{pi}H{sup 2}/{nu}, where {Omega} is the interior rotation rate, n is the radial wavenumber of the meridional flow, H is the depth of the convection zone, and {nu} is the turbulent viscosity. The smaller the {epsilon} (larger turbulent viscosity), the fewer the number of nodes in high latitudes. For all latitudes within the polar cap, we find three nodes for {nu} = 10{sup 12} cm{sup 2} s{sup -1}, two for 10{sup 13}, and one or none for 10{sup 15} or higher. For {nu} near 10{sup 14} our model exhibits 'node merging': as the meridional flow speed is increased, two nodes cancel each other, leaving no nodes. On the other hand, for fixed flow speed at the boundary, as {nu} is increased the poleward-most node migrates to the pole and disappears, ultimately for high enough {nu} leaving no nodes. These results suggest that primary poleward surface meridional flow can extend from 60 Degree-Sign to the pole either by node merging or by node migration and disappearance.

  1. Latitude variation of recurrent fluxes in the outer solar system

    NASA Technical Reports Server (NTRS)

    Christon, S. P.; Stone, E. C.

    1985-01-01

    Recurrent low energy (not less than 0.5 MeV) proton flux enhancements, reliable indicators of corotating plasma inteaction regions in interplanetary space, have been observed on the Voyager 1 and 2 and Pioneer 11 spacecraft in the heliographic latitude range 2 deg S to 23 deg N and the heliocentric radial range 11 to 20 AU. After a period of rather high correlation between fluxes at different latitudes in early 1983, distinct differences develop. The evolution of the fluxes appears to be related to the temporal and latitudinal dynamics of solar coronal holes, suggesting that information about the latitudinal structure of solar wind stream sources propagates to these distances.

  2. Effect of high latitude filtering on NWP skill

    NASA Technical Reports Server (NTRS)

    Kalnay, E.; Hoffman, R.; Takacs, L. L.

    1983-01-01

    An assessment is made of the extent to which polar filtering may seriously affect the skill of latitude-longitude NWP models, such as the U.S. Navy's NOGAPS, or the GLAS fourth-order model. The limited experiments which have been completed to date with the 4 x 5-deg, 9-level version of the latter model indicate that the high latitude filter currently in operation affects its forecasting skill very little, with only one exception in which the use of the PG filter significantly improved forecasting.

  3. High latitude regulation of low latitude thermocline ventilation and planktic foraminifer populations across glacial-interglacial cycles

    NASA Astrophysics Data System (ADS)

    Sexton, Philip F.; Norris, Richard D.

    2011-11-01

    One of the earliest discoveries in palaeoceanography was the observation in 1935 that the (sub)tropical planktic foraminifer Globorotalia menardii became absent or extremely rare in the Atlantic Ocean during glacials of the late Pleistocene. Yet a mechanistic explanation for G. menardii's extraordinary biogeographic behaviour has eluded palaeoceanographers for 75 years. Here we show that modern G. menardii, along with two other species that also suffer Atlantic population collapses during glacials, track poorly ventilated waters globally in their thermocline habitats. The ventilation states of low latitude thermoclines are 'set', to a first order, by intermediate water masses originating at high latitudes. In the modern Atlantic this control on low latitude thermocline ventilation is exerted by relatively poorly ventilated, southern-sourced Antarctic Intermediate Water (AAIW) and sub-Antarctic Mode Water (SAMW). We suggest that the glacial Atlantic foraminifer population collapses were a consequence of a low latitude thermocline that was better ventilated during glacials than it is today, in line with geochemical evidence, and driven primarily by a well-ventilated, northern-sourced intermediate water mass. A ventilation mechanism driving the glacial population collapses is further supported by our new constraints on the precise timing of these species' Atlantic proliferation during the last deglaciation — occurring in parallel with a wholesale, bipolar reorganisation of the Atlantic's thermocline-to-abyssal overturning circulation. Our findings demonstrate that a bipolar seesaw in the formation of high latitude intermediate waters has played an important role in regulating the population dynamics of thermocline-dwelling plankton at lower latitudes.

  4. L'anomalia sulla densità in latitudine delle macchie solari

    NASA Astrophysics Data System (ADS)

    Piovan, Luciano

    2004-01-01

    This paper presents the results of a study concerning the latitudinal migration of the sunspot active areas described by the usual butterfly diagrams. Data from the Marshall Space Flight Center were used to made new plots showing the latitudinal density of the sunspots. These plots revealed a peculiar shortage of sunspots around latitude 9/10° Sud. This anomaly was observed, with varying importance, up to the completion of the 20th cycle, while it disappeared in the following cycles.

  5. Redefining the Longitude/Latitude Experience with a Scaffolded Geocache

    ERIC Educational Resources Information Center

    Hammond, Thomas; Bozdin, Alec M.; Stanlick, Sarah E.

    2014-01-01

    Latitude and longitude are foundational concepts for geography education, yet they are typically poorly understood by students and receive indifferent attention from instructors and publishers' materials. Social studies teachers can take advantage of increasingly ubiquitous geolocating devices such as Global Positions Systems (GPS) to provide…

  6. Earth-Sun Relationships: Latitude, Longitude and Time.

    ERIC Educational Resources Information Center

    Thomas, Paul F.

    High school students learn about the sun's effects on the earth by examining the concepts of latitude and longitude, seasons, and time. Each of these topics is treated in a separate, but similarly organized, unit. Relevant vocabulary is introduced, and complex terms are clarified with diagrams and illustrations. In the unit on time, potentially…

  7. Teaching Latitude and Longitude in the Upper Elementary Grades.

    ERIC Educational Resources Information Center

    Johnson, Peter C.; Gondesen, Mark E.

    1991-01-01

    Discusses the desirability of teaching latitude and longitude concepts to upper elementary students. Includes a four-lesson unit on the topics. Employs hurricane tracking information available from the National Hurricane Center. Provides a foundation for future lessons on Middle and North American geography. (SG)

  8. Programmed Latitude and Longitude, Special Publication Number 10.

    ERIC Educational Resources Information Center

    Hoover, Jean C.

    Designed to measure skills involving latitude and longitude, this is a self-administering linear program for junior-high geography students. Students progress through 59 pages of fill-in-the-blank items, accompanied by appropriate line drawings, for which the correct answers are given below each question. Following the method of programmed…

  9. A solar cycle timing predictor - The latitude of active regions

    NASA Technical Reports Server (NTRS)

    Schatten, Kenneth H.

    1990-01-01

    A 'Spoerer butterfly' method is used to examine solar cycle 22. It is shown from the latitude of active regions that the cycle can now be expected to peak near November 1989 + or - 8 months, basically near the latter half of 1989.

  10. Bioerosion and carbonate mud production on high-latitude shelves

    NASA Astrophysics Data System (ADS)

    Farrow, George E.; Alan Fyfe, J.

    1988-11-01

    Low-latitude carbonate muds often are composed either of entire units of skeletons (e.g., algal muds) or of precipitates, whereas high-latitude carbonate muds are bioerosional or result from maceration. Bioerosion at high latitudes is most intense in the photic zone, particularly down to 25 m depth. Shelly substrata may be crushed, bitten, drilled, bored or scraped. Clionid sponges, endolithic algae, acmaeid gastropods and regular echinoids are the most significant agents. Clionids produce distinctive facetted carbonate silt chips when boring, which have been described from both high- and low-latitudes. Faecal pellets break down to yield mud-sized carbonate particles that are more irregular than those produced by maceration. Exhumed infaunal bivalves are often preferred to epifaunal organisms as substrata. Bioerosion occurs very rapidly; shells may be totally infested with boring algae in three months. A "moth-eaten" appearance therefore does not denote a relict grain. Reliable rates of fine sediment production are not yet available. The mud fraction of northwest European shelf sediment generally contains 10-20% CaCO 3, though an inshore and offshore belt with higher values may be identified. Some Holocene supratidal mud-flats exceed 50% CaCO 3. Much of the shelf represents a modern-day equivalent of the "calcareous shale" facies common in the geological record. Instances of synsedimentary cementation are not uncommon, particularly in association with heavily burrowed muds.

  11. The Brewer-Dobson circulation and higher latitude ozone changes

    NASA Astrophysics Data System (ADS)

    Budde, Martin; Weber, Mark

    2015-04-01

    The Brewer-Dobson Circulation (BDC) plays a major role in ozone transport from the tropics to the poles and by that it governs the global distribution of total column ozone. Climate models predict a strengthening of the BDC in times of climate change. This would lead to an accelerated recovery of ozone abundance in higher latitudes. However so far there is no clear evidence of this strengthening. The strength of the BDC is dependent on wave forcing which slows the meridional winds and by that disturbs the geostrophic balance of Coriolis force and pressure gradient force. A good measure for the wave forcing is the eddy heat flux in 100hPa. It is highly correlated with changes in the total ozone columns of the polar regions and the tropic. Another major driver of the global ozone distribution is the photochemical destruction of ozone, due to ozone depleting substances (ODS) such as chlorofluorocarbons (CFCs). A special case of this is the rapid depletion of ozone in the presence of polar stratospheric clouds (PSCs). These clouds build up inside the polar vortices, are highly temperature dependent and strengthen the efficiency of ODS. In order to analyse the evolution of the higher latitude ozone abundance as a function of dynamical changes and the change in the abundance of ODS it is necessary to quantify both effects separately. This work focusses on the influence of the mid-latitude 100hpa eddy heat flux on changes in ozone in higher latitudes.

  12. MID-LATITUDE NORTHERN HEMISPHERE BACKGROUND SULFATE CONCENTRATION IN RAINWATER

    EPA Science Inventory

    The pH is not sufficient to characterize the acidity of precipitation, but rather its acid-base components must be described. he chemistry of natural emission sources as well as the mechanism of precipitation formation determine the chemistry of precipitation at mid-latitude, Nor...

  13. Map of Martian Silicon at Mid-Latitudes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This gamma ray spectrometer map of the mid-latitude region of Mars is based on gamma-rays from the element silicon. Silicon is one of the most abundant elements on the surface of both Mars and Earth (second only to oxygen). The most extensive region of highest silicon content, shown in red, is located in the high latitudes north of Tharsis (centered near 45 degrees latitude, -120 degrees longitude). The area of lowest silicon content, shown in blue, lies just to the east of the Hellas Basin (-45 degrees latitude, 90 degrees longitude). Contours of constant surface elevation are also shown. The long continuous contour line running from east to west marks the approximate separation of the younger lowlands in the north from the older highlands in the south.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The gamma ray spectrometer was provided by the University of Arizona, Tucson. Lockheed Martin Astronautics, Denver, Colo., is the prime contractor for the project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  14. The diffuse interstellar bands and the Galactic latitude

    NASA Astrophysics Data System (ADS)

    McIntosh, Alan; Webster, Adrian

    1993-04-01

    Existing measurements of three of the diffuse interstellar bands are presented in a new way, in order to investigate how the relative strengths of different bands depend on the Galactic latitude of the stars in whose light they are seen. It is found that none of the three ratios of bandstrength amongst 4430, 5780, and 5797 A is constant, but all three are correlated with the modulus of the latitude. The abundance of the carrier of 4430 A relative to the others is found to be greatest at low latitude, while that of the carrier of 5797 A is greatest at high latitude. It is supposed that this dependence reflects a more basic dependence on height above and below the Galactic plane, the carrier of 4430 A evidently preferring conditions near the plane where the gas density is high and the carrier of 5797 A preferring the more tenuous gas further out. In terms of a recent theory in which the carriers are different hydrocarbon molecules and ions of the fullerane family, these results imply that, of the bands studied here, the carrier of 4430 A bears the most hydrogen atoms and that of 5797 A bears the fewest.

  15. Tropical and mid-latitude forcing of continental Antarctic temperatures

    NASA Astrophysics Data System (ADS)

    Turney, C. S. M.; Fogwill, C. J.; Klekociuk, A. R.; van Ommen, T. D.; Curran, M. A. J.; Moy, A. D.; Palmer, J. G.

    2015-12-01

    Future changes in atmospheric circulation and associated modes of variability are a major source of uncertainty in climate projections. Nowhere is this issue more acute than across the mid-latitudes to high latitudes of the Southern Hemisphere (SH), which over the last few decades have experienced extreme and regionally variable trends in precipitation, ocean circulation and temperature, with major implications for Antarctic ice melt and surface mass balance. Unfortunately there is a relative dearth of observational data, limiting our understanding of the driving mechanism(s). Here we report a new 130-year annually resolved record of δD - a proxy for temperature - from the geographic South Pole where we find a significant influence from extratropical pressure anomalies which act as "gatekeepers" to the meridional exchange of air masses. Reanalysis of global atmospheric circulation suggests these pressure anomalies play a significant influence on mid- to high-latitude SH climate, modulated by the tropical Pacific Ocean. This work adds to a growing body of literature confirming the important roles of tropical and mid-latitude atmospheric circulation variability on Antarctic temperatures. Our findings suggest that future increasing tropical warmth will strengthen meridional circulation, exaggerating current trends, with potentially significant impacts on Antarctic surface mass balance.

  16. Ulysses solar wind plasma observations at high latitudes

    SciTech Connect

    Riley, P.; Bame, S.J.; Barraclough, B.L.

    1996-10-01

    Ulysses reached its peak northerly heliolatitude of 80.2{degrees}N on July 31, 1995, and now is moving towards aphelion at 5.41 AU which it will reach in May, 1998. We summarize measurements from the solar wind plasma experiment, SWOOPS, emphasizing northern hemispheric observations but also providing southern and equatorial results for comparison. The solar wind momentum flux during Ulysses` fast pole-to- pole transit at solar minimum was significantly higher over the poles than at near-equatorial latitudes, suggesting a non-circular cross section for the heliosphere. Furthermore, modest asymmetries in the wind speed, density, and mass flux were observed between the two hemispheres during the fast latitude scan. The solar wind was faster and less dense in the north than in the south. These asymmetries persist in the most recent high- and mid-latitude data but are less pronounced. As of July 1, 1996 the northern fast solar wind has lacked any strong stream interactions or shocks and, although a comprehensive search has not yet been made, no CMEs have yet been identified during this interval. On the other hand, Alfv{acute e}nic, compressional, and pressure balanced features are abundant at high latitudes. The most recent data, at 4 AU and 32{degrees}N, has begun to show the effects of solar rotation modulated features in the form of recurrent compressed regions.

  17. DNA damage profiles induced by sunlight at different latitudes.

    PubMed

    Schuch, André Passaglia; Yagura, Teiti; Makita, Kazuo; Yamamoto, Hiromasa; Schuch, Nelson Jorge; Agnez-Lima, Lucymara Fassarella; MacMahon, Ricardo Monreal; Menck, Carlos Frederico Martins

    2012-04-01

    Despite growing knowledge on the biological effects of ultraviolet (UV) radiation on human health and ecosystems, it is still difficult to predict the negative impacts of the increasing incidence of solar UV radiation in a scenario of global warming and climate changes. Hence, the development and application of DNA-based biological sensors to monitor the solar UV radiation under different environmental conditions is of increasing importance. With a mind to rendering a molecular view-point of the genotoxic impact of sunlight, field experiments were undertaken with a DNA-dosimeter system in parallel with physical photometry of solar UVB/UVA radiation, at various latitudes in South America. On applying biochemical and immunological approaches based on specific DNA-repair enzymes and antibodies, for evaluating sunlight-induced DNA damage profiles, it became clear that the genotoxic potential of sunlight does indeed vary according to latitude. Notwithstanding, while induction of oxidized DNA bases is directly dependent on an increase in latitude, the generation of 6-4PPs is inversely so, whereby the latter can be regarded as a biomolecular marker of UVB incidence. This molecular DNA lesion-pattern largely reflects the relative incidence of UVA and UVB energy at any specific latitude. Hereby is demonstrated the applicability of this DNA-based biosensor for additional, continuous field experiments, as a means of registering variations in the genotoxic impact of solar UV radiation. PMID:22674547

  18. Heliomagnetic latitude dependence of the heliospheric magnetic field

    NASA Astrophysics Data System (ADS)

    Burton, M. E.; Smith, E. J.; Balogh, A.

    1995-06-01

    Previous studies have revealed systematic variations of the interplanetary magnetic field with heliographic latitude. Luhmann et al. (1987) modeled Pioneer Venus (PVO) and ISEE-3 observations by assuming an asymmetric dependence on heliolatitude with stronger fields in the northern hemisphere. In a subsequent study, using data from ISEE-3/ICE and IMP-8, Burton et al. (1990) found evidence for a similar asymmetry. However, neither model has been completely successful. The model derived from PVO/ICE observations agrees quite well near solar maximum but shows significant discrepancies during the descending phase of the solar cycle. The model derived from the ICE/IMP-8 comparison suffers from significant phase delays between the difference in field magnitude at the two spacecraft and their latitude difference. In an attempt to account for these phase shifts, the IMP-8 and ICE data have been reexamined in heliomagnetic coordinates which are defined by the orientation of the solar magnetic dipole. The latitude and longitude of the dipole inferred from the data have then been compared with those implicit in source surface calculations. The IMP/ICE correlations have been extended into the recent solar maximum and descending phase. Comparisons have also been carried out between IMP-8 and Ulysses as it traveled to -30 deg south heliographic latitude.

  19. The Ionospheric Mid-Latitude Summer Nighttime Anomaly

    NASA Astrophysics Data System (ADS)

    Lin, C.; Chen, C.; Hsu, M.; Liu, C. H.; Liu, J. G.; Burns, A. G.; Wang, W.

    2009-12-01

    This paper presents monthly variations of the mid-latitude summer nighttime anomaly (MSNA) of the ionosphere for the first time by using global observations of the FORMOSAT-3/COSMIC (F3/C), NASA TIMED-GUVI, ground-based radars and GPS receiver network. The MSNA is characterized by greater nighttime (19:00 LT - 24:00 LT, or period of larger solar zenith angles) ionospheric electron density than that during daytime (08:00 - 18:00 LT, or period of smaller solar zenith angles) at middle latitudes during solstices. The anomaly shown in the southern hemisphere during December solstice was previously known as the Weddell Sea Anomaly (WSA) occurring around the Antarctica and the nearby Pacific Ocean, while a WSA-like electron density structure also occurs in the northern hemisphere around June solstice. This study demonstrates that the anomalies occurred in both the northern and southern hemispheres share similar character of greater nighttime density. Moreover, the latitude-altitude cross-section plots of the electron density structure show very similar time-varying electron density evolutions of the MSNA. In both hemispheres, the anomalies with similar electron density characteristics and variations caused by the similar mechanism prompts us to name this phenomenon the mid-latitude summer nighttime anomaly.

  20. Electron spin resonance (ESR) dating of hominid-bearing deposits in the Caverna delle Fate, Ligure, Italy

    NASA Astrophysics Data System (ADS)

    Falgueres, Christophe; Yokoyama, Yuji; Bibron, Roland

    1990-07-01

    Stalagmitic floors interstratified with Mousterian deposits from the Caverna delle Fate (Italy) have been dated by the electron spin resonance (ESR) method. Three samples dated fall between 60,000 and 74,000 yr and indicate the age of the Mousterian deposits. They are in good agreement with ages determined by nondestructive γ-ray spectrometry of the human remains from 231Pa/ 235U and 230Th /234U ratios, which are, respectively, 75,000 -14,000+21,000 and 82,000 -25,000+36,000 yr. These dates are consistent with the morphological characteristics of the bones as Neanderthal remains.

  1. Cutoff latitude variation during solar proton events: Causes and consequences

    NASA Astrophysics Data System (ADS)

    Nesse Tyssøy, H.; Stadsnes, J.

    2015-01-01

    accurately quantify the effect of solar proton events (SPEs) on the atmosphere requires a good estimate of the particle energy deposition in the middle atmosphere (60-100 km) and how the energy is distributed globally. Protons in the energy range 1-20 MeV, depositing their energy in the middle atmosphere, are subject to more complex dynamics with strong day-night asymmetries compared to higher-energy particles. Our study targets six SPEs from 2003 to 2012. By using measurements from the Medium Energy Proton and Electron Detector on all available Polar Orbit Environment Satellites (POES), we show that in the main phase of geomagnetic storms the dayside cutoff latitudes are pushed poleward, while the nightside cutoff latitudes have the opposite response, resulting in strong day-night asymmetries in the energy deposition. These features cannot be measured by the frequently used Geostationary Operational Environmental Satellites (GOES). Assuming that the protons impact the polar atmosphere homogeneously above a fixed nominal latitude boundary will therefore give a significant overestimate of the energy deposited in the middle atmosphere during SPEs. We discuss the magnetospheric mechanisms responsible for the local time response in the cutoff latitudes and provide a simple applicable parameterization which includes both dayside and nightside cutoff latitude variability using only the Dst, the northward component of the interplanetary magnetic field, and solar wind pressure. The parameterization is utilized on the GOES particle fluxes, and the resulting energy deposition successfully captures the day-night asymmetry in good agreement with the energy deposition predicted from the POES measurement.

  2. Energetic Particles at High Latitudes of the Heliosphere

    SciTech Connect

    Zhang Ming

    2004-09-15

    Ulysses has by now made two complete out-of-ecliptic orbits around the sun. The first encounter of the solar poles occurred in 1994-1995, when the sun was near the minimum of its activity cycle, while the second one was in 2000-2001, when the sun was at solar maximum. To our surprise, energetic particles of all origins at high latitude are not much different from those we observe near the ecliptic for at least these two phases of solar cycle. The latitude gradients of galactic and anomalous cosmic rays are positive but small at the 1994-1995 solar minimum and almost zero at the 2000-2001 solar maximum, while temporal solar cycle variation dominates their flux variation at all latitudes. Solar energetic particles from all large gradual events can be seen at both Ulysses and Earth no matter how large their spatial separations from the solar event are, and the particle flux often reaches a uniform level in the entire inner heliosphere within a few days after event onset and remains so throughout the decay phase that can sometimes last over a month. Energetic particles accelerated by low-latitude CIRs can appear at high latitudes, far beyond the latitudinal range of CIRs. All these observations suggest that latitudinal transport of energetic particles is quite easy. In addition, because the average magnetic field is radial at the pole, The Ulysses observations indicate that parallel diffusion and drift in the radial direction need to be reduced at the poles relative to their equatorial values. To achieve such behaviors of particle transport, the heliospheric magnetic field needs a significant latitudinal component at the poles. A non-zero latitudinal magnetic field component can be produced by latitudinal motion of the magnetic field line in solar corona, which can be in form of either random walk suggested by Jokipii or large scale systematic motion suggested by Fisk.

  3. Changing climate cues differentially alter zooplankton dormancy dynamics across latitudes.

    PubMed

    Jones, Natalie T; Gilbert, Benjamin

    2016-03-01

    In seasonal climates, dormancy is a common strategy that structures biodiversity and is necessary for the persistence of many species. Climate change will likely alter dormancy dynamics in zooplankton, the basis of aquatic food webs, by altering two important hatching cues: mean temperatures during the ice-free season, and mean day length when lakes become ice free. Theory suggests that these changes could alter diversity, hatchling abundances and phenology within lakes, and that these responses may diverge across latitudes due to differences in optimal hatching cues and strategies. To examine the role of temperature and day length on hatching dynamics, we collected sediment from 25 lakes across a 1800 km latitudinal gradient and exposed sediment samples to a factorial combination of two photoperiods (12 and 16 h) and two temperatures (8 and 12 °C) representative of historical southern (short photoperiod, warm) and northern (long photoperiod, cool) lake conditions. We tested whether sensitivity to these hatching cues varies by latitudinal origin and differs among taxa. Higher temperatures advanced phenology for all taxa, and these advances were greatest for cladocerans followed by copepods and rotifers. Although phenology differed among taxa, the effect of temperature did not vary with latitude. The latitudinal origin of the egg bank influenced egg abundance and hatchling abundance and diversity, with these latter effects varying with taxa, temperature and photoperiod. Copepod hatchling abundances peaked at mid-latitudes in the high temperature and long photoperiod treatments, whereas hatchling abundances of other zooplankton were greatest at low latitudes and high temperature. The overall diversity of crustacean zooplankton (copepods and cladocerans) also reflected distinct responses of each taxa to our treatments, with the greatest diversity occurring at mid-latitudes (~56 °N) in the shorter photoperiod treatment. Our results demonstrate that hatching cues

  4. Geographic control of Titan's mid-latitude clouds

    NASA Astrophysics Data System (ADS)

    Roe, H. G.; Brown, M. E.; Schaller, E. L.; Bouchez, A. H.; Trujillo, C. A.

    2005-08-01

    Observations of tropospheric clouds (1-6) and the recent Huygens images of channels show that Titan has an active methane hydrological cycle. Titan's south polar clouds are now well known (3-5) and thought to be driven by small seasonal variations in surface temperature (3). The recent discovery (6) and continued observations (7) of significant cloud activity at 40oS latitude led to the suggestion that these mid-latitude clouds are the result of either seasonally evolving global circulation or surface geography (6). We report here further observations of Titan that clearly link the formation of the mid-latitude clouds to a region of Titan's surface centered at ˜350oW longitude, ˜40oS latitude. Analysis of the complete dataset does not support the earlier suggestion (6) that these clouds are a new phenomenon related to seasonal change. The strong link between geographic location and cloud formation along with the lack of evidence for seasonal change in the mid-latitude clouds leads to the conclusion that a geological mechanism is responsible for the formation of these clouds. We propose that geysers or cryovolcanism are sporadically active near ˜350oW longitude, ˜40oS latitude. The implied rate of volatile release would easily supply enough methane to balance the loss to photolytic chemistry in the upper atmosphere. 1. Griffith, C.A., Owen, T., Miller, G.A., Geballe, T., Nature 395, 575-578 (1998). 2. Griffith, C.A., Hall, J.L., Geballe, T.R., Science 290, 509-513 (2000). 3. Brown, M.E., Bouchez, A.H., Griffith, C.A., Nature 420, 795-797 (2002). 4. Roe, H.G., de Pater, I., Macintosh, B.A., McKay, C.P., ApJ 581, 1399-1406 (2002). 5. Bouchez, A.H., Brown, M.E., ApJ 618, L53-L56 (2005). 6. Roe, H.G., Bouchez, A.H., Trujillo, C.A., Schaller, E.L., Brown, M.E., ApJ 618, L49-L52 (2005). 7. Porco, C.C., et al., Nature 434, 159-168 (2005). HGR is supported by an NSF Astronomy & Astrophysics Postdoctoral Fellowship (NSF AST-0401559). ELS is supported by an NSF Graduate

  5. Maritime User Requirements at High Latitudes - the MARENOR Project

    NASA Astrophysics Data System (ADS)

    Behlke, R.

    2014-12-01

    The ionosphere at high latitudes is characterised by a great variety of spatial and temporal variations that influence radio signals. In addition to navigation solutions that are based on Global Navigation Satellite Systems (GNSS), satellite communication systems also suffer from ionospheric degradation. This is worsened by harsh weather conditions, insufficient coverage by geostationary satellites and the absence of land-based augmentation infrastructure. Climate change will lead to a decrease in sea ice extent and thus to an increased use of trans-polar shipping routes, presence of gas and oil industries in the High Arctic and higher focus on Search-and-Rescue (SAR) as well as sovereignty issues. These moments usually require navigation and communication solutions that are accurate and reliable. We describe requirements presented by industrial operators on and around Svalbard. In addition, we present the MARENOR project that aims on evaluating navigation and communication systems at high latitudes including first results

  6. An energy principle for high-latitude electrodynamics

    NASA Technical Reports Server (NTRS)

    Barbosa, D. D.

    1984-01-01

    A theoretical model for mid- and high-latitude electric fields and currents is constructed using Fourier analysis methods. A two-dimensional planar ionosphere with an enhanced conductivity auroral belt and field-aligned currents at the edges is employed. The postulate that the electric field and currents adjust self-consistently to minimize the global Joule dissipation rate defines a theoretical relation between the primary and secondary field-aligned currents. This so-called minimal dissipation configuration is examined using several input field-aligned current models, and graphical solutions for the electric field and ionospheric current are shown. A detailed discussion and interpretation of the solutions with relation to diverse observations and high-latitude phenomenology are included.

  7. Neutral winds above 200 km at high latitudes.

    NASA Technical Reports Server (NTRS)

    Meriwether, J. W.; Heppner, J. P.; Stolarik, J. D.; Wescott, E. M.

    1973-01-01

    Electrically neutral, luminous clouds are a by-product of chemical releases conducted to create barium ion clouds for the measurement of electric fields. Wind measurements provided by the motions of these clouds are particularly valuable in that the motions can be directly compared with convective ion drift motions to test the importance of ion drag forces. Motion from multiple releases between 200 and 300 km from 15 rockets launched from four high-latitude locations is analyzed in this paper. The observations in the evening and midnight hours at magnetic latitudes above 65 deg strongly suggest that in these regions ion drag is the dominant force in driving neutral winds between 200 and 300 km. In the morning sector, it is evident that neutral wind observations cannot be directly interpreted in terms of ion drag; other factors must be considered.

  8. Orbital control of low-latitude seasonality during the Eemian

    USGS Publications Warehouse

    Winter, A.; Paul, A.; Nyberg, J.; Oba, T.; Lundberg, J.; Schrag, D.; Taggart, B.

    2003-01-01

    We used Sr/Ca and stable isotope data from well dated and preserved corals from the northeastern Caribbean to determine the seasonal environmental conditions for four continuous years during the Eemian, the last time the Earth was in a prolonged warm phase. We determined that the seasonal range in SST during the Eemian was 25??-30?? C. This is ???1-2?? larger than at present and caused primarily by winter cooling and, only to a small degree, by summer warming. As climate modeling studies indicate, the bias towards colder winters can be explained by changes in low latitude insolation induced by altered orbital parameters, modulated by atmospheric CO2 levels that were lower than today. Milankovitch forcing at higher latitudes was probably less important.

  9. High-Latitude Ionospheric Dynamics During Conditions of Northward IMF

    NASA Technical Reports Server (NTRS)

    Sharber, J. R.

    1996-01-01

    In order to better understand the physical processes operating during conditions of northward interplanetary magnetic field (IMF), in situ measurements from the Dynamics Explorer-2 (low altitude) polar satellite and simultaneous observations from the auroral imager on the Dynamics Explorer-1 (high altitude) satellite were used to investigate the relationships between optical emissions, particle precipitation, and convective flows in the high-latitude ionosphere. Field aligned current and convective flow patterns during IMF north include polar cap arcs, the theta aurora or transpolar arc, and the 'horse-collar' aurora. The initial part of the study concentrated on the electrodynamics of auroral features in the horse-collar aurora, a contracted but thickened emission region in which the dawn and dusk portions can spread to very high latitudes, while the latter part focused on the evolution of one type of IMF north auroral pattern to another, specifically the quiet-time horse-collar pattern to a theta aurora.

  10. Electron temperature measurements in mid-latitude sporadic E layers

    NASA Technical Reports Server (NTRS)

    Schutz, S. R.; Smith, L. G.

    1976-01-01

    By using rocket-borne Langmuir probes, electron temperature profiles have been obtained in five mid-latitude sporadic E layers. The data show the electron temperature within the layers to be lower than the electron temperature at the adjacent altitudes. This is consistent with the layers' being maintained by a vertical redistribution of ionization. The magnitude of the observed electron temperature variation is, however, larger than expected.

  11. Actividad de LOS Hoyos Coronales Solares de Baja Latitud

    NASA Astrophysics Data System (ADS)

    Bravo, S.; Mendoza, B.; Pirez-Enriquez, R.; Valdes-Galicia, J.

    1987-05-01

    Strong variations of the coronal holes of mid and low latitudes during the ascending and descending phase of the solar cycle have been observed by means of IPS records (the interplanetary scintillation of small diameter radio sources). This variations induce the propagation of disturbances in the interplanetary medium which produce the IPS and are also responsible of cosmic ray modulation. We suggest that the 11 years modulation is influenced by such a coronal hole behaviour.

  12. Probing high latitude ionospheric irregularities by GPS: Results and analysis

    NASA Astrophysics Data System (ADS)

    Krankowski, Andrzej; Shagimuratov, Irk; Ephishov, I. I.; Sieradzki, Rafal

    The GPS measurements of IGS network were used to study the occurrence of TEC fluctuations at northern and southern high latitude ionosphere during severe geomagnetic disturbances of 22-28 July 2004. For the northern hemisphere we selected 20 GPS stations located higher than 55 degrees of Corrected Geomagnetic Latitude. For the southern hemisphere, Antarctic permanent GPS stations were used. Dual-frequency GPS measurements along individual satellite passes served as row data. As a measure a fluctuation activity the rate of TEC (ROT) was used, and fluctuation intensity was evaluated using ROTI index. Using daily GPS measurements from all the selected stations, the images of spatial and temporal behavior of TEC fluctuations (in Corrected Geomagnetic Coordinate and local geomagnetic time) were formed. Similarly to the auroral oval the images demonstrate an irregularities oval. The occurrence of irregularities oval relates with the auroral oval and polar caps. During the storm, TEC fluctuation activity and intensity essentially increased. The irregularities oval expands equatorward with increasing magnetic activity. As a whole, the dynamics of the irregularities ovals in both hemispheres are similar during the storm time, however we found some difference in development of TEC fluctuations between northern and southern ionosphere. They may be caused by seasonal features of excitation of irregularities at high latitude ionosphere. Daily pattern of the irregularities oval was controlled by the motion of the station location into auroral oval. Maximal intensity of TEC fluctuations took place over polar stations. The strong TEC fluctuations were associated with the polar patches. Their study showed that the existing high-latitude GPS stations can provide a permanent monitoring of the irregularities oval in near real-time.

  13. Arctic Amplification and Potential Mid-Latitude Weather Linkages

    NASA Astrophysics Data System (ADS)

    Overland, J. E.

    2014-12-01

    Increasing temperatures and other changes continued in the Arctic over the last decade, even though the rate of global warming has decreased in part due to a cool Pacific Ocean. Thus Arctic temperatures have increased at least 3 times the rate of mid-latitude temperatures. Credibility for persistent Arctic change comes from multiple indicators which are now available for multiple decades. Further, the spatial pattern of Arctic Amplification differs from patterns of natural variability. The role of the Arctic in the global climate system is based on multiple interacting feedbacks represented by these indicators as a causal basis for Arctic Amplification driven by modest global change. Many of these processes act on a regional basis and their non-linear interactions are not well captured by climate models. For example, future loss of sea ice due to increases in CO2 are demonstrated by these models but the rates of loss appear slow. It is reasonable to suspect that Arctic change which can produce the largest temperature anomalies on the planet and demonstrate recent extremes in the polar vortex could be linked to mid-latitude weather, especially as Arctic change will continue over the next decades. The meteorological community remains skeptical, however, in the sense of "not proven." Natural variability in chaotic atmospheric flow remains the main dynamic process, and it is difficult to determine whether Arctic forcing of a north-south linkage is emerging from the most recent period of Arctic change since 2007. Nonetheless, such a hypothesis is worthy of investigation, given the need to further understand Arctic dynamic atmospheric processes, and the potential for improving mid-latitude seasonal forecasts base on high-latitude forcing. Several AGU sessions and other forums over the next year (WWRP, IASC,CliC) address this issue, but the topic is not ready for a firm answer. The very level of controversy indicates the state of the science.

  14. Center is at Latitude 30 Degrees North, Longitude 30 Degrees

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Center of the orthographic projection is at latitude 30 degrees N., longitude 30 degrees. The north polar residual ice cap, which is cut by spiral-patterned troughs, is located at the top. The central part is characterized by a dark depression, Chryse basin, where several large outflow channels terminate. The lower-left corner is marked by a vast system of canyons, Valles Marineris, which extends eastward for several thousand kilometers.

  15. Center is at Latitude 30 Degrees South., Longitude 330 Degrees

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Center of the orthographic projection is at latitude 30 degrees S., longitude 330 degrees. Heavily cratered highlands dominate this view. Toward the lower right, a conspicuous light-colored circular depression marks the ancient large Hellas impact basin. Directly northeast of Hellas, several large ancient impacts dot the landscape, including Cassini, Schiaparelli, and Huygens. Several large outflow channels are located in the upper left-hand corner. The permanent, residual south polar ice cap is located near the bottom.

  16. Center is at Latitude 30 Degrees South, Longitude 210 Degrees

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Center of the orthographic projection is at latitude 30 degrees S., longitude 210 degrees. Toward the top, the lowland plains of Elysium and Utopia Planitiae are separated from the darker heavily cratered highlands by a broad escarpment. The far bottom left is marked by the large light-colored ancient Hellas impact basin. The permanent south polar residual ice cap is located near the bottom.

  17. Simulating Children's Retrieval Errors in Picture-Naming: A Test of Foygel and Dell's (2000) Semantic/Phonological Model of Speech Production

    ERIC Educational Resources Information Center

    Budd, Mary-Jane; Hanley, J. Richard; Griffiths, Yvonne

    2011-01-01

    This study investigated whether Foygel and Dell's (2000) interactive two-step model of speech production could simulate the number and type of errors made in picture-naming by 68 children of elementary-school age. Results showed that the model provided a satisfactory simulation of the mean error profile of children aged five, six, seven, eight and…

  18. High-latitude space weather monitoring in Finland

    NASA Astrophysics Data System (ADS)

    Ulich, Th.

    2009-04-01

    Today, space weather is of important concern in many respects. Space weather phenomena are subject of extensive scientific research programmes and the consequences of space weather events are of great operational concern for a number of technologies including satellites, humans in space, and global positioning and communications. Due to the Earth's magnetic field, the high latitudes are most strongly affected by space weather phenomena. Naturally, monitoring and understanding of the high-latitude space environment is important for forecasting and modelling operational conditions. The Sodankylä Geophysical Observatory (SGO) was established as a magnetic observatory in 1913. With the sole exception of a year at the end of WWII, the record of geomagnetic field variations is continuous. Since the IGY in 1957, many other routine measurements have been added to the observatory's operations and today SGO is a highly versatile observatory. Here we will present examples of high-latitude space weather data from a selection of instruments including the Sodankylä ionosonde, the Finnish Riometer Chain, and the Tomography (GNSS) receiver chain. We invite collaboration and use of our data products. We will further outline the current EU Framework VII "Access to Research Infrastructures" project of SGO "LAPBIAT2."

  19. Latitude-for-Time Proxy for Climate Change in Lakes

    NASA Astrophysics Data System (ADS)

    Laval, B.; Vagle, S.; Morrison, J.; Carmack, E.

    2014-12-01

    While the full interpretation of climate signals in lake systems requires an understanding of lake-specific physical forcing and response mechanisms, we propose that insight into the response of a lake at a specific latitude to climate change can be acquired by comparing the present conditions of a morphologically and dynamically similar lake at lower latitude. The latitude-for-time shift comes from swapping current latitudinal gradients of air temperature with predicted air temperature trends due to climate change. Of interest is the potential transition of a lake from one mictic state to another, with consequences to the resupply of nutrients to the euphotic zone, and to the phenology of spring and fall phytoplankton blooms. Here we compare the annual thermal histories in seven deep, intermontane lakes in western Canada along a north-south transect from 49o to 61o N, and use predicted trends in air temperature to estimate commensurate changes in duration of summer stratification period. While the actual response of lakes to climate change is likely to be much more complex, this simple model offers support that field observations in large lakes spanning the full range of present day climatic conditions offers a valuable tool for assessing the response of lake dynamics to climate warming.

  20. Electrodynamic structure of the morning high-latitude trough region

    NASA Astrophysics Data System (ADS)

    Vanhamäki, H.; Aikio, A.; Voiculescu, M.; Juusola, L.; Nygrén, T.; Kuula, R.

    2016-03-01

    We describe the electrodynamics of a postmidnight, high-latitude ionospheric trough, observed with the European Incoherent Scatter radar in northern Scandinavia on 24-25 June 2003 around 22:00-02:30 UT during quiet conditions. The UHF radar made meridian scans with a 30 min cadence resulting in nine cross sections of ionospheric parameters. The F region electric field was also determined with the tristatic system. Ionospheric equivalent currents, calculated from ground magnetometer data, mostly show an electrojet-like current that is reasonably uniform in the longitudinal direction. Combined analysis of the conductances and equivalent current with a local Kamide-Richmond-Matsushita (KRM) method yields the ionospheric electric field and field-aligned current (FAC) in a 2-D (latitude-longitude) area around the radar. We conclude that the most likely scenario is one where the trough is initially created poleward of the auroral oval by downward FAC that evacuates the F region, but as the trough moves to lower latitudes during the early morning hours, it becomes colocated with the westward electrojet. There the electron density further decreases due to increased recombination caused by enhanced ion temperature, which in turn is brought about by a larger convection speed. Later in the morning the convection speed decreases and the trough is filled by increasing photoionization.

  1. Mid-latitude afforestation shifts general circulation and tropical precipitation

    PubMed Central

    Swann, Abigail L. S.; Fung, Inez Y.; Chiang, John C. H.

    2012-01-01

    We show in climate model experiments that large-scale afforestation in northern mid-latitudes warms the Northern Hemisphere and alters global circulation patterns. An expansion of dark forests increases the absorption of solar energy and increases surface temperature, particularly in regions where the land surface is unable to compensate with latent heat flux due to water limitation. Atmospheric circulation redistributes the anomalous energy absorbed in the northern hemisphere, in particular toward the south, through altering the Hadley circulation, resulting in the northward displacement of the tropical rain bands. Precipitation decreases over parts of the Amazon basin affecting productivity and increases over the Sahel and Sahara regions in Africa. We find that the response of climate to afforestation in mid-latitudes is determined by the amount of soil moisture available to plants with the greatest warming found in water-limited regions. Mid-latitude afforestation is found to have a small impact on modeled global temperatures and on global CO2, but regional heating from the increase in forest cover is capable of driving unintended changes in circulation and precipitation. The ability of vegetation to affect remote circulation has implications for strategies for climate mitigation. PMID:22190490

  2. Ionosphere Scintillation at Low and High Latitudes (Modelling vs Measurement)

    NASA Astrophysics Data System (ADS)

    Béniguel, Yannick

    2016-04-01

    This paper will address the problem of scintillations characteristics, focusing on the parameters of interest for a navigation system. Those parameters are the probabilities of occurrence of simultaneous fading, the bubbles surface at IPP level, the cycle slips and the fades duration statistics. The scintillation characteristics obtained at low and high latitudes will be compared. These results correspond to the data analysis performed after the ESA Monitor ionosphere measurement campaign [1], [2]. A second aspect of the presentation will be the modelling aspect. It has been observed that the phase scintillation dominates at high latitudes while the intensity scintillation dominates at low latitudes. The way it can be reproduced and implemented in a propagation model (e.g. GISM model [3]) will be presented. Comparisons of measurements with results obtained by modelling will be presented on some typical scenarios. References [1] R. Prieto Cerdeira, Y. Beniguel, "The MONITOR project: architecture, data and products", Ionospheric Effects Symposium, Alexandria (Va), May 2011 [2] Y. Béniguel, R Orus-Perez , R. Prieto-Cerdeira , S. Schlueter , S. Scortan, A. Grosu "MONITOR 2: ionospheric monitoring network in support to SBAS and other GNSS and scientific purposes", IES Conference, Alexandria (Va), May 2015-05-22 [3] Y. Béniguel, P. Hamel, "A Global Ionosphere Scintillation Propagation Model for Equatorial Regions", Journal of Space Weather Space Climate, 1, (2011), doi: 10.1051/swsc/2011004

  3. High latitude TEC fluctuations and irregularity oval during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Shagimuratov, I. I.; Krankowski, A.; Ephishov, I.; Cherniak, Yu.; Wielgosz, P.; Zakharenkova, I.

    2012-06-01

    GPS measurements obtained by the global IGS network were used to study the occurrence of TEC fluctuations in the northern and southern high-latitude ionosphere during severe geomagnetic storms. In the northern hemisphere, GPS stations located higher than 55N Corrected Geomagnetic Latitude (CGL) at different longitudes were selected. In the southern hemisphere, Antarctic permanent GPS stations were used. Dual-frequency GPS measurements for individual satellite passes served as raw data. As a measure of fluctuation activity the rate of TEC (ROT) was used, and the fluctuation intensity was evaluated using the ROTI index. Using daily GPS measurements from all selected stations, images of the spatial and temporal behavior of TEC fluctuations were formed (in Corrected Geomagnetic Coordinates—CGC and geomagnetic local time—GLT). Similarly to the auroral oval, these images demonstrate an irregularity oval. The occurrence of the irregularity oval relates to the auroral oval, cusp and polar cap. During a storm, the intensity of TEC fluctuations essentially increased. The irregularity oval expands equatorward with an increase of magnetic activity. The study showed that the existing high-latitude GPS stations can provide a permanent monitoring tool for the irregularity oval in near real-time. In this paper, the features of the development of phase fluctuations at the geomagnetic conjugate points, and inter-hemispheric differences and similarities during winter and summer conditions, are discussed.

  4. Recent Advances in Mid-latitude Ionosphere/Thermosphere Science

    NASA Astrophysics Data System (ADS)

    Kelley, Michael

    One of the original reasons for building a National Ionospheric Observatory (now the National Astronomy and Ionospheric Center or NAIC) near Arecibo, Puerto Rico was the location, which is in the best behaved region of the ionosphere. At 30° magnetic latitude and 19° geographic latitude, it is well equatorward of the auroral and sub-auroral zones and poleward of the equatorial anomalies most of the time. The island thus has some of the best weather and space weather on the planet. However, similar to an occasional hurricane striking the island, the ionosphere overhead has occasional ionospheric and thermospheric disturbances. Some of these space weather phenomena, e.g., mesoscale TIDs and unstable sporadic E layers, are endemic to the region and, prior to the advent of airglow imagers and GPS networks, were difficult to visualize using radiowave data alone. Other weather events are caused by infringement on this zone from processes in more active weather regions. For example, neutral waves launched from the auroral oval (large scale TIDs) pass through the region; electric fields penetrate from the solar wind and create both plasma uplifts, causing positive ionospheric storms, and stormenhanced density plumes, coursing through the region. From the south, convective equatorial ionospheric storms create plasma bubbles that can reach mid-latitudes. Examples of data obtained during these phenomena, and possibly more, will be presented and discussed in light of our present understanding.

  5. Mid-latitude afforestation shifts general circulation and tropical precipitation.

    PubMed

    Swann, Abigail L S; Fung, Inez Y; Chiang, John C H

    2012-01-17

    We show in climate model experiments that large-scale afforestation in northern mid-latitudes warms the Northern Hemisphere and alters global circulation patterns. An expansion of dark forests increases the absorption of solar energy and increases surface temperature, particularly in regions where the land surface is unable to compensate with latent heat flux due to water limitation. Atmospheric circulation redistributes the anomalous energy absorbed in the northern hemisphere, in particular toward the south, through altering the Hadley circulation, resulting in the northward displacement of the tropical rain bands. Precipitation decreases over parts of the Amazon basin affecting productivity and increases over the Sahel and Sahara regions in Africa. We find that the response of climate to afforestation in mid-latitudes is determined by the amount of soil moisture available to plants with the greatest warming found in water-limited regions. Mid-latitude afforestation is found to have a small impact on modeled global temperatures and on global CO(2), but regional heating from the increase in forest cover is capable of driving unintended changes in circulation and precipitation. The ability of vegetation to affect remote circulation has implications for strategies for climate mitigation. PMID:22190490

  6. Ionospheric signatures of cusp latitude Pc 3 pulsations

    NASA Technical Reports Server (NTRS)

    Engebretson, M. J.; Anderson, B. J.; Cahill, L. J., Jr.; Arnoldy, R. L.; Rosenberg, T. J.

    1990-01-01

    Search coil magnetometer, riometer, photometer, and ELF-VLF receiver data obtained at South Pole Station and McMurdo, Antarctica during selected days in March and April 1986 are compared. Narrow-band magnetic pulsations in the Pc 3 period range are observed simultaneously at both stations in the dayside sector during times of low IMF cone angle, but are considerably stronger at South Pole, which is located at a latitude near the nominal foot point of the dayside cusp/cleft region. Pulsations in auroral light at 427.8 nm wavelength are often observed with magnetic pulsations at South Pole, but such optical pulsations are not observed at McMurdo. The observations suggest that precipitating magnetosheathlike electrons at nominal dayside cleft latitudes are at times modulated with frequencies similar to those of upstream waves. These particles may play an important role, via modification of ionospheric currents and conductivities, in the transmission of upstream wave signals into the magnetosphere and in the generation of dayside high-latitude Pc 3 pulsations.

  7. Mid-latitude lidar observations of large sporadic sodium layers

    SciTech Connect

    Senft, D.C.; Collins, R.L.; Gardner, C.S. )

    1989-07-01

    During the early morning of October 31, 1988 two large sporadic Na (Na{sub s}) layers were observed near the mesopause above Urbana, IL (40{degree}N, 88{degree}W) with a Na lidar system. The layers began forming near 102 km at 0026 LST and 0110 LST and moved downward with vertical velocities as high as 4 ms{sup {minus}1} before dissipating between 94 and 96 km. The duration of each layer was approximately 80 min. The layers were narrow ({approximately} 1 km FWHM) and dense with maximum densities approaching 7,800 cm{sup {minus}3}. The characteristics of these two Na{sub s} layers are very similar to those of similar phenomena observed recently at Andoya, Norway and Mauna Kea, Hawaii. Lidar observations of the mesospheric Na layer have been conducted routinely by several groups at mid-latitudes for almost 20 years. Although large Na{sub s} layers now appear to be relatively common at low- and high-latitudes, to our knowledge the two layers described in this letter are only the second observation of this puzzling phenomenon at mid-latitudes.

  8. Geophysical investigations at the Paleolitic site Grotta delle Veneri near Parabita (Lecce, Italy)

    NASA Astrophysics Data System (ADS)

    Carrozzo, M. T.; Leucci, G.; Negri, S.; Nuzzo, L.

    2003-04-01

    The human presence in Apulia (southern Italy) is documented since 80.000 years before present. In 1966 near Parabita (Lecce, Italy) in a cave subsequently named "Grotta delle Veneri" human remains belonging to Homo Sapiens Neanderthalensis (Neanderthal) and Homo Sapiens-Sapiens (Cro-Magnon) were recovered together with two small statues of pregnant women ("Veneri") referable to 12.000--10.000 b.C. The local Archaeological Superintendence was interested in assessing the possibility to reconstruct by means of geophysical methods the planimetric position of the cave and further development of its burrows beyond those accessible to speleologists and reported in the underground topographic survey. Both electromagnetic (EM) and electric methods were tested using Ground Penetrating Radar (GPR) with 200 and 500 MHz antennas, GEM300 multi-frequency EM induction device and 2D Electrical Resistivity Tomography (ERT). Despite the rough surface and the presence of numerous obstacles (trees, stone walls and stone piles) limiting the accessible survey area and often preventing a good ground-coupling, the GPR survey successfully located the top of the karstic cave and identified zones of high density of diffraction hyperbolas, interpreted as highly fractured and karstified limestone, in a layer ranging from about 2 m to 6 m below ground. Zones characterised by high density of diffractions due to presence of voids were found also outside the known development of the cave. By means of the GEM 300, both in-phase and quadrature components of the induced EM signal were simultaneously collected at 8 frequencies, from 2025 to 19975 Hz, respectively related to the magnetic susceptibility and apparent conductivity of the soil down to a depth decreasing as the frequency increase. A presumable low contrast in the sought parameter between the highly fractured rock and karstic voids or refilled cavities as well as the presence of metallic debris on the ground allowed a difficult identification

  9. Microphysical Ice Crystal Properties in Mid-Latitude Frontal Cirrus

    NASA Astrophysics Data System (ADS)

    Schlage, Romy; Jurkat, Tina; Voigt, Christiane; Minikin, Andreas; Weigel, Ralf; Molleker, Sergej; Klingebiel, Marcus; Borrmann, Stephan; Luebke, Anna; Krämer, Martina; Kaufmann, Stefan; Schäfler, Andreas

    2015-04-01

    Cirrus clouds modulate the climate by reflection of shortwave solar radiation and trapping of longwave terrestrial radiation. Their net radiative effect can be positive or negative depending on atmospheric and cloud parameters including ice crystal number density, size and shape. Latter microphysical ice crystal properties have been measured during the mid-latitude cirrus mission ML-CIRRUS with a set of cloud instruments on the new research aircraft HALO. The mission took place in March/April 2014 with 16 flights in cirrus formed above Europe and the Atlantic. The ice clouds were encountered at altitudes from 7 to 14 km in the typical mid-latitude temperature range. A focus of the mission was the detection of frontal cirrus linked to warm conveyor belts (WCBs). Within WCBs, water vapor is transported in the warm sector of an extra-tropical cyclone from the humid boundary layer to the upper troposphere. Cirrus cloud formation can be triggered in the WCB outflow region at moderate updraft velocities and additionally at low updrafts within the high pressure system linked to the WCB. Due to their frequent occurrence, WCBs represent a major source for regions of ice supersaturation and cirrus formation in the mid-latitudes. Here, we use data from the Cloud and Aerosol Spectrometer with detection for POLarization (CAS-POL) and the Cloud Combination Probe (CCP), combining a Cloud Droplet Probe (CDP) and a greyscale Cloud Imaging Probe (CIPgs) to investigate the ice crystal distribution in the size range from 0.5 µm to 1 mm. We derive microphysical cirrus properties in mid-latitude warm front cirrus. Further, we investigate their variability and their dependence on temperature and relative humidity. Finally, we compare the microphysical properties of these frontal cirrus to cirrus clouds that formed at low updrafts within high pressure systems or at high updraft velocities in lee waves. We quantify statistically significant differences in cirrus properties formed in these

  10. Titan's Stratospheric Condensibles at High Northern Latitudes During Northern Winter

    NASA Technical Reports Server (NTRS)

    Anderson, Carrie; Samuelson, R.; Achterberg, R.

    2012-01-01

    The Infrared Interferometer Spectrometer (IRIS) instrument on board Voyager 1 caught the first glimpse of an unidentified particulate feature in Titan's stratosphere that spectrally peaks at 221 per centimeter. Until recently, this feature that we have termed 'the haystack,' has been seen persistently at high northern latitudes with the Composite Infrared Spectrometer (CIRS) instrument onboard Cassini, The strength of the haystack emission feature diminishes rapidly with season, becoming drastically reduced at high northern latitudes, as Titan transitions from northern winter into spring, In contrast to IRIS whose shortest wavenumber was 200 per centimeter, CIRS extends down to 10 per centimeter, thus revealing an entirely unexplored spectral region in which nitrile ices have numerous broad lattice vibration features, Unlike the haystack, which is only found at high northern latitudes during northern winter/early northern spring, this geometrically thin nitrile cloud pervades Titan's lower stratosphere, spectrally peaking at 160 per centimeter, and is almost global in extent spanning latitudes 85 N to 600 S, The inference of nitrile ices are consistent with the highly restricted altitude ranges over which these features are observed, and appear to be dominated by a mixture of HCN and HC3N, The narrow range in altitude over which the nitrile ices extend is unlike the haystack, whose vertical distribution is significantly broader, spanning roughly 70 kilometers in altitude in Titan's lower stratosphere, The nitrile clouds that CIRS observes are located in a dynamically stable region of Titan's atmosphere, whereas CH4 clouds, which ordinarily form in the troposphere, form in a more dynamically unstable region, where convective cloud systems tend to occur. In the unusual situation where Titan's tropopause cools significantly from the HASI 70.5K temperature minimum, CH4 should condense in Titan's lower stratosphere, just like the aforementioned nitrile clouds, although

  11. Spectral effects on latitude-tilt and vertical PV modules as affected by latitude, air mass, and climate

    NASA Astrophysics Data System (ADS)

    Gueymard, Christian A.

    2007-09-01

    Using the same SMARTS radiative code as for the development of improved reference spectra for PV rating, an analysis of the spectral sensitivity of specific PV technologies to varying air mass and other factors is presented. To the difference of previous studies, the approach taken here considers realistic atmospheric conditions, as measured at five North- American sites from widely different climatic zones. Two different PV applications (latitude-tilted flat-plates and vertical building-integrated modules) are showcased with seven possible materials, including a-Si, m-Si, and triple junctions. Considering the most frequent clear-sky conditions around the summer solstice at the selected sites, the Spectral Enhancement Factor (SEF) is calculated both for a fixed air mass (1.5) and daily-average spectral conditions. This analysis provides a preliminary assessment of how latitude, local climatic conditions, and PV geometry affect the relative merits of different technologies relatively to standard rating conditions. In particular, it is shown that, in summer, latitude-tilt PV modules experience bluer incident spectra than the reference spectrum, therefore favoring the a-Si modules (SEF > 1). For vertical-tilt PV systems, the SEF is generally lower than for latitude-tilt systems, with the notable exception of m- Si. When considering daily-average results, the effective SEF can become extremely low in the case of a-Si (down to 0.65) and moderately high for m-Si (up to 1.09). It is concluded that the effects of location, season, and PV material on the spectral effect needs to be investigated in detail, particularly for applications involving vertical building-integrated systems.

  12. Storm time heavy ion outflow at mid-latitudes

    SciTech Connect

    Yeh, H.C.; Foster, J.C. )

    1990-06-01

    Local ionospheric observations with the Millstone Hill incoherent scatterradar reveal an upward ion bulk velocity in excess of 3 km s{sup {minus} 1} at 1,000 km altitude during the very large magnetic storm on February 8, 1986. The upward flux of O{sup +} ions exceeded 3 {times} 10{sup 9} cm{sup {minus}2} s{sup {minus}1} at 42{degree} geodetic latitude (55{degree} {Lambda}) for a 3-hour period around 18 MLT during the event. Frictinal ion heating with ion temperatures in excess of 4,000 K at 500 km altitude was observed by the radar in the vicinity of the ion outflow event. Satellite observations place the ion outflow event within a region of intense ion and electron precipitation on field lines associated with the storm-perturbed ring current. For a one-dimensional analysis of the observed plasma profiles, continuity considerations indicate a region of intense O{sup +} production (200 cm{sup {minus}3} s{sup {minus}1}) as well as significant upward acceleration (5-10 m s{sup {minus}2}) in the region between 600 km and 800 km altitude where the outflow approaches supersonic speed. Ionizing collisions involving fast backsplash neutral O atoms (Torr et al., 1974) produced by ring current heavy ion precipitation can provide sufficient upward momentum to account for the acceleration in the observed outflowing thermal O{sup +} fluxes. Alternatively, the outflow event can be explained in terms of a time-dependent diffusion process triggered by a sudden change in the frictional heating rate in the collision-dominated F region (St.-Maurice, 1989). The concurrence of rapid ion convection and energetic ring current precipitation is unique at mid-latitudes during intense magnetic storms. Under these conditions, the observations indicate that the mid-latitude ionosphere constitutes a significant source of upflowing thermal O{sup +} fluxes to the overlying magnetosphere.

  13. Models for the positive latitude e{-}e{+} annihilation feature

    NASA Astrophysics Data System (ADS)

    von Ballmoos, P.; Guessoum, N.; Jean, P.; Knödlseder, J.

    2003-01-01

    Galactic maps of e-e+ annihilation radiation based on CGRO-OSSE, SMM and TGRS data have indicated the existence of an extended component at positive Galactic latitudes (l~ -2 deg, b~ 7 deg), in addition to the emission from the galactic bulge and disk (Purcell et al. \\cite{Purcell97}; Cheng et al. \\cite{Cheng97}; Milne et al. \\cite{Milne00}; Milne et al. \\cite{Milne01}). This Positive Latitude Enhancement (PLE) was first attributed to an ``annihilation fountain" in the Galactic center (Dermer & Skibo \\cite{Dermer97}) but has since been the object of several models. After discussing the observational evidence for the PLE, we investigate various models for the PLE: besides the scenarios proposed in the literature, we have introduced a number of models requiring relatively modest positron rates due to a local origin of the e-e+ emission (local galactic-, solar system-, earth- and spacecraft-environment origins). The various scenarios for the PLE are constrained in the light of the latest OSSE-SMM-TGRS data analysis results: we have looked at the possible positron production mechanisms as well as the annihilation conditions in the different physical environments (temperature and dust grain content) proposed for the positive-latitude region. By constraining those parameters, based on the recent limits for the line width and the positronium fraction, we found that some of the models can essentially be discarded. A number of other scenarios will have to await further measurements and maps, such as will be possible with INTEGRAL's SPI and IBIS instruments. We present a table/checklist of model-falsification criteria.

  14. Equatorial to Mid-Latitude Connections in Eastern Boundary Currents

    NASA Astrophysics Data System (ADS)

    Strub, T.

    2002-12-01

    Over twenty years ago, Enfield and Allen (1980, J. Phys. Oceaogr., 10, 557-578) used tide-gauge sea level height data to show the connection between the equator and the mid-latitude coastal ocean in the eastern Pacific. Careful selection of tide gauges and quality control of the data allowed both seasonal and interannual time scales to be examined over a period of 24 years. Today, 10 years of TOPEX/POSEIDON altimeter data allow us to re-examine the seasonal and non-seasonal connections between the equator and higher latitudes in the eastern boundary currents (EBC's) along the coasts of the Pacific and Atlantic Oceans. We present the seasonal progressions in both basins and hemispheres, showing the low-to-high latitude development of the seasonal cycle and also the offshore propagation of annual Rossby waves. This brings out several general tendencies: 1) The signals are stronger in the Northern Hemisphere basins, due to the fact that the ITCZ is located north of the equator in both basins; 2) The signals are stronger in the NE Pacific than in any of the other basins; and 3) There is an annual signal of high sea surface height that propagates down both Southern Hemisphere EBC's in austral spring (September-November) as the SW trade winds weaken along the equator and the equatorial cold tongue collapses. This last feature is somewhat like an annual "El Ni¤o" effect and acts to suppress the onset of wind driven upwelling in the Peru-Chile and Benguela Current Systems.

  15. A mid-latitude ozone model for the US standard atmosphere, 1975 (summary)

    NASA Technical Reports Server (NTRS)

    Krueger, A. J.; Minzner, R. A.

    1974-01-01

    A mid-latitude, Northern-Hemisphere model of the daytime ozone distribution in the troposphere, stratosphere, and lower mesosphere was constructed. Data from rocket soundings in the latitude range 45 deg N + or - 15 deg, results of balloon soundings at altitudes from 41 to 47 deg N, and latitude gradients from satellite ozone observations were combined to produce estimates of the annual mean ozone concentration and its variability at heights to 72 km for an effective latitude of 45 deg N. The model is a revision, for heights above 26 km, of the tentative Mid-Latitude Ozone Model.

  16. Ulysses solar wind plasma observations from peak southerly latitude through perihelion and beyond

    SciTech Connect

    Phillips, J.L.; Bame, S.J.; Feldman, W.C.; Gosling, J.T.; McComas, D.J.; Goldstein, B.E.; Neugebauer, M.; Hammond, C.M.

    1996-07-01

    We present Ulysses solar wind plasma data from the peak southerly latitude of {minus}80.2{degree} through +64.9{degree} latitude on June 7, 1995. Ulysses encountered fast wind throughout this time except for a 43{degree} equatorial band. Mass flux was nearly constant with latitude, while speed (density) had positive (negative) poleward gradients. Momentum flux was highest at high latitudes, suggesting a latitudinal asymmetry in the heliopause cross section. Solar wind energy flux density was also highest at high latitudes. {copyright} {ital 1996 American Institute of Physics.}

  17. Ulysses solar wind plasma observations from peak southerly latitude through perihelion and beyond

    SciTech Connect

    Phillips, J.L.; Bame, S.J.; Feldman, W.C.; Gosling, J.T.; McComas, D.J.; Goldstein, B.E.; Neugebauer, M.; Hammond, C.M.

    1995-09-01

    We present Ulysses solar wind plasma data from the peak southerly latitude of {minus}80.2{degrees} through +64.9{degrees} latitude on June 7, 1995. Ulysses encountered fast wind throughout this time except for a 43{degrees} band centered on the solar equator. Median mass flux was nearly constant with latitude, while speed and density had positive and negative poleward gradients, respectively. Solar wind momentum flux was highest at high latitudes, suggesting a latitudinal asymmetry in the heliopause cross section. Solar wind energy flux density was also highest at high latitudes.

  18. Source effects in mid-latitude geomagnetic transfer functions

    NASA Astrophysics Data System (ADS)

    Araya Vargas, Jaime; Ritter, Oliver

    2016-01-01

    Analysis of more than 10 yr of vertical magnetic transfer function (VTF) estimates obtained at 12 mid-latitude sites, located in different continents and tectonic settings, reveals significant temporal variations for a period range between approximately 250 and 2000 s. The most ubiquitous pattern is a seasonal modulation of the VTF element that relates the vertical to the horizontal north-south magnetic components (Tx), which shows a high peak around the June solstice (and a low peak around the December solstice) regardless of the location of the site. To quantify the influence of this source effect on the amplitude of VTFs, we modelled the temporal variations of VTFs using a function with dependence on season and magnetic activity indexes. The model shows that differences between VTF estimates obtained at seasonal peaks can reach 0.08 of Tx absolute values and that the effect increases with latitude and period. Seasonal variations are observed also in the VTF component relating vertical to horizontal east-west magnetic components (Ty), but here the pattern with respect to the geographic distribution is less clear. In addition to seasonal trends, we observe long-term modulations correlating with the 11-yr solar cycle at some sites. The influence of these external source effects should be taken into account, before attempting a geological interpretation of the VTFs. It can be misleading, for example, to combine or compare VTFs obtained from long-period geomagnetic data acquired at different seasons or years. An effective method to estimate and remove these source effects from VTFs is by comparison with temporal variations of VTFs from synchronously recorded data at sites located at similar latitude (<5° of difference) and longitude (<10° of difference). Source effects in temporal variations of VTFs can be identified as those patterns that exhibit similar amplitudes and significant correlation with the geomagnetic activity at all compared sites. We also provide a

  19. The brightest high-latitude 12-micron IRAS sources

    NASA Technical Reports Server (NTRS)

    Hacking, P.; Beichman, C.; Chester, T.; Neugebauer, G.; Emerson, J.

    1985-01-01

    The Infrared Astronomical Satellite (IRAS) Point Source catalog was searched for sources brighter than 28 Jy (0 mag) at 12 microns with absolute galactic latitude greater than 30 deg excluding the Large Magellanic Cloud. The search resulted in 269 sources, two of which are the galaxies NGC 1068 and M82. The remaining 267 sources are identified with, or have infrared color indices consistent with late-type stars some of which show evidence of circumstellar dust shells. Seven sources are previously uncataloged stars. K and M stars without circumstellar dust shells, M stars with circumstellar dust shells, and carbon stars occupy well-defined regions of infrared color-color diagrams.

  20. A computer model of high-latitude scintillation

    NASA Astrophysics Data System (ADS)

    Fremouw, E. J.

    1982-01-01

    The DNA Wideband satellite experiment provided extensive data on scintillation produced in high-altitude structured plasmas. A computer program, WBMOD, is being developed to summarize those data in an applications-oriented way. The program contains the phase-screen scattering theory of Rino and a morphological description of ionospheric irregularities (thus far only at auroral latitudes) based on Wideband observations. It permits a user to compute scintillation indices for both phase and intensity as a function of system operating parameters and solar-ionospheric disturbance level. Correction is made for multiple scatter, and the user may choose either one-way (communication) or two-way (radar) propagation.

  1. High-latitude dayside electric field and particle measurements

    NASA Technical Reports Server (NTRS)

    Maynard, N. C.; Johnstone, A. D.

    1973-01-01

    Two rockets carrying electric field and low energy particle instrumentation were launched near noon at 80 deg magnetic latitude. One flight encountered polar cap conditions only while the other traversed part of the polar cusp. Although weak particle precipitation was measured on both flights, bursts of intense magnetosheath-type electron fluxes were detected on the latter. Strong electric fields such as would result from anti-sunward convection were observed during both flights. The measurements are compared with results obtained by other types of space craft and interpreted in the light of those data.

  2. How Altitude and Latitude Control Dune Morphometry on Titan

    NASA Technical Reports Server (NTRS)

    Le Gall, A.; Hayes, A.; Ewing, R.; Janssen, M. A.; Radebaugh, J.; Savage, C.; Encrenaz, P.

    2011-01-01

    Dune fields are one of the dominant landforms and represent the largest known organic reservoir on Titan. SAR-derived topography show that Titan's dune terrains tend to occupy the lowest altitude areas in equatorial regions occurring at mean elevations between approx.-400 and 0 m. In elevated dune terrains, there is a definite trend towards a smaller dune to interdune ratio, interpreted as due to limited sediment availability. A similar linear correlation is observed with latitude, suggesting that the quantity of windblown sand in the dune fields tends to decrease as one moves farther north. These findings place important constraints on Titan's geology and climate.

  3. Low latitude geomagnetic field line resonance: Experiment and modeling

    SciTech Connect

    Waters, C.L.; Menk, F.W.; Fraser, B.J.

    1994-09-01

    The authors describe work to detect field line resonances, or the observation of Pc 3-5 geomagnetic pulsation events, at low latitude sites. These signals are extracted from ground based magnetometer arrays. The authors found one field line resonance structure in 5 weeks of data at L=1.8. At L=2.8 they were able to observe up to 4 harmonics concurrently. They compare these frequency spectra with the results of two different models of the plasma density in the lower ionosphere.

  4. Ionospheric storm effects at subauroral latitudes: A case study

    SciTech Connect

    Proelss, G.W. ); Brace, L.H.; Mayr, H.G. ); Carignan, G.R.; Killeen, T.L. ); Klobuchar, J.A. )

    1991-02-01

    An attempt is made to classify ionospheric storm effects at subauroral latitudes according to their presumed origin. The storm of December 7/8, 1982, serves as an example. It is investigated using ionosonde, electron content, and DE 2 satellite data. The following effects are distinguished: (1) positive storm effects caused by traveling atmospheric disturbances, (2) positive storm effects caused by changes in the large-scale thermospheric wind circulation, (3) positive storm effects caused by the expansion of the polar ionization enhancement, (4) negative storm effects caused by perturbations of the neutral gas composition, and (5) negative storm effects caused by the equatorward displacement of the trough region.

  5. Analytical model of ionospheric convection at subauroral latitudes

    NASA Astrophysics Data System (ADS)

    Deminov, M. G.; Kim, V. P.; Shubin, V. N.; Khegai, V. V.

    An analytical model of plasma convection in the subauroral ionosphere is developed, assuming that the electric shielding of the inner magnetosphere is controlled by polarization of the hot ion zone situated behind the inner boundary of the plasma sheet. It is shown that, at subauroral latitudes at night, the plasma drifts eastward, while during the day it shifts westward. Thus, in the predmidnight sector, the direction of convection in the subauroral ionosphere is opposite to that of auroral convection. In general, the electric field, with a strength of 10 mV/m, has a meridional direction.

  6. A survey of formaldehyde in high Galactic latitudes

    NASA Technical Reports Server (NTRS)

    Heithausen, A.; Mebold, U.; De Vries, H. W.

    1987-01-01

    The discovery of formaldehyde (H2CO) in four out of 15 CO-clouds observed in high Galactic latitudes is reported. For one of these a velocity-integrated formaldehyde map is presented. The clouds are clearly connected to CO clouds described by de Vries et al. (1986), to Lynds bright and dark nebulae (Lynds, 1963), and to the Galactic infrared cirrus (Low et al., 1984). The distribution of CO and H2CO clouds is compared. The depths of the l(10-11)H2CO lines show no correlation to the integrated J = l-0(C-12)O line intensities.

  7. Observations of plasma structure and transport at high latitudes

    SciTech Connect

    Weber, E.J.; Buchau, J.

    1985-01-01

    Radio and optical diagnostics from the AFGL Airborne Ionospheric Observatory are used to study the structure and motion of regions of enhanced F-region density at high latitudes. Plasma flow can be tracked from the poleward edge of the dayside cusp, across the polar cap and into the nightside auroral zone. Simultaneous satellite amplitude and phase scintillation measurements define the degree of structuring or intensity of sub-kilometer ionospheric irregularities within these regions. The combined measurements are used to track large scale plasma flow, and to infer plasma source regions.

  8. Computer model of high-latitude scintillation. [WBMOD program

    SciTech Connect

    Fremouw, E.J.

    1982-01-01

    The DNA Wideband satellite experiment provided extensive data on scintillation produced in high-altitude structured plasmas. A computer program, WBMOD, is being developed to summarize those data in an applications-oriented way. The program contains the phase-screen scattering theory of Rino and a morphological description of ionospheric irregularities (thus far only at auroral latitudes) based on Wideband observations. It permits a user to compute scintillation indices for both phase and intensity as a function of system operating parameters and solar-ionospheric disturbance level. Correction is made for multiple scatter, and the user may choose either one-way (communication) or two-way (radar) propagation.

  9. Center is at Latitude 30 Degrees South, Longitude 90 Degrees

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Center of the orthographic projection is at latitude 30 degrees S., longitude 90 degrees. The top half is dominated by the Tharsis Montes volcanoes, the large Alba Patera shield volcano, the dark Chryse basin, and a vast canyon system, Valles Marineris. In the central part, a prominent physiographic feature, Thaumasia plateau, includes a complex array of small- and large-scale faults and ridges and ancient volcanoes. The large conspicuous Argyre basin, southeast of the Thaumasia plateau, contains a broad expanse of light-colored plains 800 km across. The permanent south polar ice cap is located near the bottom.

  10. Center is at Latitude 30 Degrees North, Longitude 150 Degrees

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Center of the orthographic projection is at latitude 30 degrees N., longitude 150 degrees. The north polar residual ice cap, which is cut by spiral-patterned troughs and surrounded by the dark lowland plains of Vastitas Borealis, is located at the top. The right-central part is dominated by the Tharsis Montes volcanoes. The most prominent of the Tharsis Montes volcanoes is the largest known volcano in the solar system, Olympus Mons. The light-colored lowland plains of Amazonis, Elysium, and Arcadia Planitiae lies north and west of Olympus Mons. The heavily cratered highlands dominate the lower one-third.

  11. Ionospheric storm effects at subauroral latitudes - A case study

    NASA Technical Reports Server (NTRS)

    Proelss, G. W.; Brace, L. H.; Mayr, H. G.; Carignan, G. R.; Killeen, T. L.

    1991-01-01

    An attempt is made to classify ionospheric storm effects at subauroral latitudes according to their presumed origin. The storm of December 7/8, 1982, serves as an example. It is investigated using ionosonde, electron content, and DE 2 satellite data. The following effects are distinguished: (1) positive storm effects caused by traveling atmospheric disturbances, (2) positive storm effects caused by changes in the large-scale thermospheric wind circulation, (3) positive storm effects caused by the expansion of the polar ionization enhancement, (4) negative storm effects caused by perturbations of the neutral gas composition, and (5) negative storm effects caused by the equatorward displacement of the trough region.

  12. Double-peaked sodium layers at high latitudes

    NASA Technical Reports Server (NTRS)

    Von Zahn, U.; Goldberg, R. A.; Stegman, J.; Witt, G.

    1989-01-01

    Na lidar observations indicate that at high latitudes in summer the neutral Na layer frequently attains a double-peaked structure. The main layer with a maximum near 90 km altitude is supplemented by a secondary, narrow layer near 95 km altitude. Results are presented concerning secondary sodium layers. It appears likely that the formation of secondary Na layers observed frequently above the lidar site is not solely a 'sodium phenomenon', but part of a more comprehensive layering process for metal atoms and ions. Na(+)/Na density ratios close to 0.5 near the peaks of both the main and secondary layers are derived.

  13. Interconnect Performance Evaluation of SGI Altix 3700 BX2, Cray X1, Cray Opteron Cluster, and Dell PowerEdge

    NASA Technical Reports Server (NTRS)

    Fatoohi, Rod; Saini, Subbash; Ciotti, Robert

    2006-01-01

    We study the performance of inter-process communication on four high-speed multiprocessor systems using a set of communication benchmarks. The goal is to identify certain limiting factors and bottlenecks with the interconnect of these systems as well as to compare these interconnects. We measured network bandwidth using different number of communicating processors and communication patterns, such as point-to-point communication, collective communication, and dense communication patterns. The four platforms are: a 512-processor SGI Altix 3700 BX2 shared-memory machine with 3.2 GB/s links; a 64-processor (single-streaming) Cray XI shared-memory machine with 32 1.6 GB/s links; a 128-processor Cray Opteron cluster using a Myrinet network; and a 1280-node Dell PowerEdge cluster with an InfiniBand network. Our, results show the impact of the network bandwidth and topology on the overall performance of each interconnect.

  14. Can evolutionary constraints explain the rarity of nitrogen-fixing trees in high-latitude forests?

    PubMed

    Menge, Duncan N L; Crews, Timothy E

    2016-09-01

    Contents 1195 I. 1195 II. 1196 III. 1196 IV. 1200 1200 References 1200 SUMMARY: The rarity of symbiotic nitrogen (N)-fixing trees in temperate and boreal ('high-latitude') forests is curious. One explanation - the evolutionary constraints hypothesis - posits that high-latitude N-fixing trees are rare because few have evolved. Here, we consider traits necessary for high-latitude N-fixing trees. We then use recent developments in trait evolution to estimate that > 2000 and > 500 species could have evolved from low-latitude N-fixing trees and high-latitude N-fixing herbs, respectively. Evolution of N-fixing from nonfixing trees is an unlikely source of diversity. Dispersal limitation seems unlikely to limit high-latitude N-fixer diversity. The greater number of N-fixing species predicted to evolve than currently inhabit high-latitude forests suggests a greater role for ecological than evolutionary constraints. PMID:27411210

  15. MEASUREMENTS OF THE SUN'S HIGH-LATITUDE MERIDIONAL CIRCULATION

    SciTech Connect

    Rightmire-Upton, Lisa; Hathaway, David H.; Kosak, Katie E-mail: david.hathaway@nasa.gov

    2012-12-10

    The meridional circulation at high latitudes is crucial to the buildup and reversal of the Sun's polar magnetic fields. Here, we characterize the axisymmetric flows by applying a magnetic feature cross-correlation procedure to high-resolution magnetograms obtained by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. We focus on Carrington rotations 2096-2107 (2010 April to 2011 March)-the overlap interval between HMI and the Michelson Doppler Imager (MDI). HMI magnetograms averaged over 720 s are first mapped into heliographic coordinates. Strips from these maps are then cross-correlated to determine the distances in latitude and longitude that the magnetic element pattern has moved, thus providing meridional flow and differential rotation velocities for each rotation of the Sun. Flow velocities were averaged for the overlap interval and compared to results obtained from MDI data. This comparison indicates that these HMI images are rotated counterclockwise by 0.{sup 0}075 with respect to the Sun's rotation axis. The profiles indicate that HMI data can be used to reliably measure these axisymmetric flow velocities to at least within 5 Degree-Sign of the poles. Unlike the noisier MDI measurements, no evidence of a meridional flow counter-cell is seen in either hemisphere with the HMI measurements: poleward flow continues all the way to the poles. Slight north-south asymmetries are observed in the meridional flow. These asymmetries should contribute to the observed asymmetries in the polar fields and the timing of their reversals.

  16. Seedling mortality from litterfall increases with decreasing latitude.

    PubMed

    Gillman, Len N

    2016-02-01

    Global patterns in ecology need to be identified and interpreted if macroecological processes are to be fully understood. Facilitating effects on seedlings such as that of nurse plants and competitive effects such as allelopathy have been well recognized but the importance of plants acting as killers through physical damage by the litterfall they produce has received relatively little attention. Here I examine latitudinal patterns of physical disturbance to seedlings (microdisturbance) due to litterfall and discuss the macroecological implications in light of current research. Analyses of results from published studies show that both the risk of litterfall disturbance, as measured using artificial model seedlings, and the proportion of seedling mortalities due to litterfall decrease significantly with increasing latitude. Patterns of microdisturbance appear to be driven by the dynamic interaction between macro-litterfall, safe sites with protective overhead vegetation, topography, and animal activity. However, we are informed on this subject by few studies. There is evidence, again from a limited number of studies, for considerable spatial heterogeneity in microdisturbance intensity and for seedling resilience to litterfall damage to differ substantially among species. Therefore, differential survival among microsites may produce regeneration niche diversity. However, more focused studies are required across a range of forest types and latitudes before these results can be generalized. Therefore, there is fertile ground for researchers to use comparable multifactorial methods to investigate the implications of microdisturbance at macro-ecological scales. PMID:27145626

  17. Ulysses observations of auroral hiss at high Jovian latitudes

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Macdowall, R. J.; Desch, M. D.; Kaiser, M. L.; Stone, R. G.; Kellogg, P. J.; Lin, N.; Cornilleau-Wehrlin, N.; Canu, P.; Bame, S. J.

    1993-01-01

    During the Ulysses flyby of Jupiter, a whistler-mode emission was periodically detected by the unified Radio and Plasma wave (URAP) experiment during intervals when the spacecraft extended to high magnetic latitudes. The signal was detected between the local electron plasma frequency and lower hybrid resonance and appears as a funnel-shaped structure on frequency-versus-time spectrograms; these characteristics are very reminiscent of whistler-mode auroral hiss observed at high latitudes at Earth. Ray tracing of the emission occurrences suggests the emission source is on magnetic field lines extending out to at least 65 R(sub J). This location associates the emission with the boundary between open and closed field lines -- not the Io torus. The emission radiates about 10(exp 7) W of power. Consequently, the auroral input power derived from the solar wind to drive the emission is believed to be 10(exp 10-12) W (or about 1% of the energy associated with Io torus electrical processes).

  18. SIMULATED FARADAY ROTATION MEASURES TOWARD HIGH GALACTIC LATITUDES

    SciTech Connect

    Akahori, Takuya; Kim, Jongsoo; Ryu, Dongsu; Gaensler, B. M. E-mail: akahori@physics.usyd.edu.au E-mail: ryu@canopus.cnu.ac.kr

    2013-04-20

    We study the Faraday rotation measure (RM) due to the Galactic magnetic field (GMF) toward high Galactic latitudes. The RM arises from the global, regular component as well as from the turbulent, random component of the GMF. We model the former based on observations and the latter using the data of magnetohydrodynamic turbulence simulations. For a large number of different GMF models, we produce mock RM maps around the Galactic poles and calculate various statistical quantities with the RM maps. We find that the observed medians of RMs toward the north and south Galactic poles, {approx}0.0 {+-} 0.5 rad m{sup -2} and {approx} + 6.3 {+-} 0.5 rad m{sup -2}, are difficult to explain with any of our many alternate GMF models. The standard deviation of observed RMs, {approx}9 rad m{sup -2}, is clearly larger than that of simulated RMs. The second-order structure function of observed RMs is substantially larger than that of simulated RMs, especially at small angular scales. We discuss other possible contributions to RM toward high Galactic latitudes. Besides observational errors and the intrinsic RM of background radio sources against which RM is observed, we suggest that the RM due to the intergalactic magnetic field may account for a substantial fraction of the observed RM. Finally, we note that reproducing the observed medians may require additional components or/and structures of the GMF that are not present in our models.

  19. Low-latitude field-aligned currents deduced by Swarm

    NASA Astrophysics Data System (ADS)

    Lühr, Hermann; Kervalishvili, Guram; Rauberg, Jan

    2015-04-01

    ESA's constellation mission Swarm was successfully launched on 22 November 2013. The three satellites are orbiting the Earth at 470 km and 520 km altitude. The lower pair Swarm-A and C is flying side-by-side separated by only 1.4° in latitude. Magnetic field readings of this pair are used to determine for the first time field-aligned currents (FAC) uniquely in the ionosphere. Of particular interest for this presentation are FACs at low and equatorial latitudes. Indications for several of such current systems have been deduced from CHAMP observations. Examples to be studied are meridional and vertical currents driven by the F-region dynamo. They are expected to show opposite polarities between noon and sunset. Likewise there are FACs expected to balance the electric potential differences between the foci of the Sq current vortices in the two hemispheres, which should be most prominent during solstice seasons. Another example is the FAC associated with equatorial plasma bubbles. They are expected to flow along the walls of the electron density depleted volume. Due to the limited amount of suitable Swarm data we will focus on June solstice and September equinox 2014 for this presentation.

  20. Structure of High Latitude Currents in Magnetosphere-Ionosphere Models

    NASA Astrophysics Data System (ADS)

    Wiltberger, M.; Rigler, E. J.; Merkin, V.; Lyon, J. G.

    2016-07-01

    Using three resolutions of the Lyon-Fedder-Mobarry global magnetosphere-ionosphere model (LFM) and the Weimer 2005 empirical model we examine the structure of the high latitude field-aligned current patterns. Each resolution was run for the entire Whole Heliosphere Interval which contained two high speed solar wind streams and modest interplanetary magnetic field strengths. Average states of the field-aligned current (FAC) patterns for 8 interplanetary magnetic field clock angle directions are computed using data from these runs. Generally speaking the patterns obtained agree well with results obtained from the Weimer 2005 computing using the solar wind and IMF conditions that correspond to each bin. As the simulation resolution increases the currents become more intense and narrow. A machine learning analysis of the FAC patterns shows that the ratio of Region 1 (R1) to Region 2 (R2) currents decreases as the simulation resolution increases. This brings the simulation results into better agreement with observational predictions and the Weimer 2005 model results. The increase in R2 current strengths also results in the cross polar cap potential (CPCP) pattern being concentrated in higher latitudes. Current-voltage relationships between the R1 and CPCP are quite similar at the higher resolution indicating the simulation is converging on a common solution. We conclude that LFM simulations are capable of reproducing the statistical features of FAC patterns.

  1. INTERMEDIATE-VELOCITY MOLECULAR GAS AT HIGH NORTHERN GALACTIC LATITUDES

    SciTech Connect

    Magnani, Loris; Smith, Allison J.

    2010-10-20

    We surveyed the CO(1-0) transition in 16 regions at Galactic latitudes >45{sup 0} which contain compact dust cores less than half a degree in size with E(B - V) values {approx} 0.1 mag. We discovered three new intermediate-velocity molecular clouds and two high-latitude molecular clouds with more typical local standard of rest velocity ({approx}0 km s{sup -1}). The three intermediate-velocity molecular clouds (detected in CO emission in 11 lines of sight) nearly double the number of previously known, CO-emitting clouds. In order to detect the CO(1-0) line, N(H{sub 2}) values of at least 10{sup 19} cm{sup -2} are necessary, implying that the molecular/atomic fraction of these objects is significant and is in contrast to the primarily atomic lines of sight with log N(H{sub 2}) < 17.3 detected in absorption by FUSE. The three molecular clouds are projected on and likely associated with a previously known intermediate-velocity H I feature known as the Intermediate Velocity Spur that may extend to the Galactic halo.

  2. Evapotranspiration Cycles in a High Latitude Agroecosystem: Potential Warming Role.

    PubMed

    Ruairuen, Watcharee; Fochesatto, Gilberto J; Sparrow, Elena B; Schnabel, William; Zhang, Mingchu; Kim, Yongwon

    2015-01-01

    As the acreages of agricultural lands increase, changes in surface energetics and evapotranspiration (ET) rates may arise consequently affecting regional climate regimes. The objective of this study was to evaluate summertime ET dynamics and surface energy processes in a subarctic agricultural farm in Interior Alaska. The study includes micrometeorological and hydrological data. Results covering the period from June to September 2012 and 2013 indicated consistent energy fractions: LE/Rnet (67%), G/Rnet (6%), H/Rnet (27%) where LE is latent heat flux, Rnet is the surface net radiation, G is ground heat flux and H is the sensible heat flux. Additionally actual surface evapotranspiration from potential evaporation was found to be in the range of 59 to 66%. After comparing these rates with those of most prominent high latitude ecosystems it is argued here that if agroecosystem in high latitudes become an emerging feature in the land-use, the regional surface energy balance will significantly shift in comparison to existing Arctic natural ecosystems. PMID:26368123

  3. Population differences in finger-length ratios: ethnicity or latitude?

    PubMed

    Loehlin, John C; McFadden, Dennis; Medland, Sarah E; Martin, Nicholas G

    2006-12-01

    The relative length of the second and fourth fingers (the 2D:4D ratio) has been taken to be an indicator of prenatal exposure to testosterone, and hence possibly relevant to sexual orientation and other sex-differentiated behaviors. Studies have reported a difference in this ratio between Caucasian males in Britain and in the U.S.: higher average 2D:4D ratios were obtained in Britain. This raises the question of whether differences among different Caucasian gene pools were responsible or whether some environmental variable associated with latitude might be involved (e.g., exposure to sunlight or different day-length patterns). This question was explored by examining 2D:4D ratios for an Australian adolescent sample. The Australians were predominantly of British ancestry, but lived at distances from the equator more like those of the U.S. studies. The Australian 2D:4D ratios resembled those in Britain rather than those in the U.S., tending to exclude hypotheses related to latitude and making differences in gene pools a plausible explanation. PMID:16688484

  4. Tropical and mid-latitude forcing of continental Antarctic temperatures

    NASA Astrophysics Data System (ADS)

    Turney, C. S. M.; Fogwill, C. J.; Klekociuk, A.; van Ommen, T. D.; Curran, M. A. J.; Moy, A. D.; Palmer, J. G.

    2015-07-01

    Future changes in atmospheric circulation and associated modes of variability are a major source of uncertainty in climate projections. Nowhere is this issue more acute than across the mid- to high-latitudes of the Southern Hemisphere (SH) which over the last few decades has experienced extreme and regional variable trends in precipitation, ocean circulation, and temperature, with major implications for Antarctic ice melt and surface mass balance. Unfortunately there is a relative dearth of observational data, limiting our understanding of the driving mechanism(s). Here we report a new 130-year annually-resolved record of δ D - a proxy for temperature - from the South Geographic Pole where we find a significant influence from extra-tropical pressure anomalies which act as "gatekeepers" to the meridional exchange of air masses. Reanalysis of global atmospheric circulation suggests these pressure anomalies play a considerably larger influence on mid- to high-latitude SH climate than hitherto believed, modulated by the tropical Pacific Ocean. Our findings suggest that future increasing tropical warmth will strengthen meridional circulation, exaggerating current trends, with potentially significant impacts on Antarctic surface mass balance.

  5. The interchange instability in high-latitude plasma blobs

    SciTech Connect

    Chaturvedi, P.K.; Huba, J.D. )

    1987-04-01

    The stability of high-latitude plasma density enhancements (blobs) is analyzed with regard to the interchange mode (driven by neutral wind or equilibrium transverse electric field acting on the density gradient at the walls of the blobs). The effects arising from the finite parallel length of the blobs along the magnetic field lines are included in the analysis. Plasma regions of differing collisionalities, to which the blobs extend in altitude, are considered. The authors find that the finite parallel blob size results in a modest reduction in the growth rates of the small ({approx lt}1 km) and intermediate (1-10 km) scale sizes but severely reduces the growth rates for the large scale sizes (> 10 km) for the observed parallel blob lengths ({approximately}300-600 km). Further, it is found that the instability growth rates show a moderate reduction at higher altitudes (where ion-inertial effects may be dominant over the ion-neutral collisional effects). Thus the E{times} B instability is considered a plausible candidate for the scintillation-causing irregularities (1-10 km) associated with the high-latitude blobs.

  6. Interchange instability in high-latitude plasma blobs. Memorandum report

    SciTech Connect

    Chaturvedi, P.K.; Huba, J.D.

    1986-12-30

    The stability of high-latitude plasma-density enhancements (blobs) is analyzed with regard to the interchange model (driven by a neutral wind or transverse electric field acting on the density gradient at the walls of the blobs). The effects arising from the finite parallel length of the blobs along the magnetic field lines are included in the analysis. Plasma regions of differing collisionalities, to which the blobs extend in altitude, are considered. It was found that the finite-parallel blob size results in a modest reduction in the growth rates of the small somewhat < 1 km) and intermediate (1-10 km) scale sizes, but severely reduces the growth rates, for the large scale sizes (> 10 kms) for the observed parallel blob lengths (approx. 300-600 kms). Further, it is found that the instability growth rates show a moderate reduction at higher altitudes (where ion-inertial effects may be dominant over the ion-neutral collisional effects). Thus, the E x B instability is considered a plausible candidate for the scintillation causing irregularities (1-10 kms) associated with the high-latitude blobs.

  7. Map of Martian Potassium at Mid-Latitudes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This gamma ray spectrometer map of the mid-latitude region of Mars is based on gamma-rays from the element potassium. Potassium, having the chemical symbol K, is a naturally radioactive element and is a minor constituent of rocks on the surface of both Mars and Earth. The region of highest potassium content, shown in red, is concentrated in the northern part of Acidalia Planitia (centered near 55 degrees N, -30 degrees). Several areas of low potassium content, shown in blue, are distributed across the mid-latitudes, with two significant low concentrations, one associated with the Hellas Basin (centered near 35 degrees S, 70 degrees) and the other lying southeast of Elysium Mons (centered near 10 degrees N, 160 degrees). Contours of constant surface elevation are also shown. The long continuous line running from east to west marks the approximate separation of the younger lowlands in the north from the older highlands in the south.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The gamma ray spectrometer was provided by the University of Arizona, Tucson. Lockheed Martin Astronautics, Denver, is the prime contractor for the project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  8. Evapotranspiration Cycles in a High Latitude Agroecosystem: Potential Warming Role

    PubMed Central

    Ruairuen, Watcharee

    2015-01-01

    As the acreages of agricultural lands increase, changes in surface energetics and evapotranspiration (ET) rates may arise consequently affecting regional climate regimes. The objective of this study was to evaluate summertime ET dynamics and surface energy processes in a subarctic agricultural farm in Interior Alaska. The study includes micrometeorological and hydrological data. Results covering the period from June to September 2012 and 2013 indicated consistent energy fractions: LE/Rnet (67%), G/Rnet (6%), H/Rnet (27%) where LE is latent heat flux, Rnet is the surface net radiation, G is ground heat flux and H is the sensible heat flux. Additionally actual surface evapotranspiration from potential evaporation was found to be in the range of 59 to 66%. After comparing these rates with those of most prominent high latitude ecosystems it is argued here that if agroecosystem in high latitudes become an emerging feature in the land-use, the regional surface energy balance will significantly shift in comparison to existing Arctic natural ecosystems. PMID:26368123

  9. Geomagnetic response to IMF and solar wind over different latitudes

    NASA Astrophysics Data System (ADS)

    Aslam, A. M.; Tripathi, Sharad Chandra; Mansoori, Azad Ahmad; Waheed, Malik Abdul

    2016-07-01

    In this paper a study on the response of geomagnetic field characteristics to the solar wind variation during three solar cycles (SC 21, SC 22, SC 23) have been conducted in a long term scale. The difference in the response of two different latitudinal characteristic indices has been investigated. For the purpose we have considered the high latitude index AE and the mid-latitude aa index and both gives the knowledge about the perturbations in the geomagnetic field conditions. Eventually we can infer the idea about the ionospheric current system changes in response to the solar wind conditions. The variation found in the AE and aa indices have been found to follow a 11 year cycle as similar to the sunspot variation. Also the correlation between the annual means of the solar wind parameters velocity V, magnetic filed B and the composite parameters BV and BV ^{2 } have been calculated . A difference was found between the correlations obtained for the AE and aa indices. We could also see that the difference in correlation follows a cyclic pattern i.e. the large difference is found during the solar maxima while a small difference is observed during the minima.

  10. The Low-latitude Ionospheric Sensor Network: The Initial Campaigns

    NASA Astrophysics Data System (ADS)

    Doherty, P. H.; Valladares, C. E.; Carrano, C.

    2009-05-01

    The Low-latitude Ionospheric Sensor Network (LISN) is a distributed observatory designed to provide regional coverage in South America and high-temporal resolution measurements to diagnose the initiation and development of plasma structures and the state and dynamics of the low latitude ionosphere. It combines inexpensive GPS receivers and state-of-the-art radars such as the Vertical Incidence Pulsed Ionospheric Radar (VIPIR) ionosondes and magnetometers. This paper describes the characteristics of the LISN distributed observatory and discusses the results of the first two campaigns. LISN will be comprised of nearly 70 GPS receivers with the capability to measure Total Electron Content (TEC), amplitude and phase scintillation and Traveling Ionospheric Disturbances (TIDs). LISN will also include 5 ionosondes able to measure nighttime E-region densities and 5 collocated magnetometers that will be placed along the same magnetic meridian. The first campaign was dedicated to detect medium-scale (~100 km) TIDs and was conducted at Huancayo, Peru in July 2008 using 3 GPS receivers spaced by 4-5 km arranged in a triangular configuration. TEC data corresponding to 3 consecutive days indicate that the TIDs phase velocity was close to 120 m/s and directed northward during the early evening hours. The second campaign was conducted in February 2009 using 3 GPS receivers installed near Ancon and coordinated with the VIPIR ionosonde running in an interferometer mode. We will discuss the implications of these new results within the frame of the current theories of plasma bubble onset.

  11. Anomalous variations of tropopause height in low latitude regions

    NASA Astrophysics Data System (ADS)

    Ramkumar, T. K.; Narayana Rao, D.

    Successful attempts have been made in early 1990s to link the possible influence of equatorial stratospheric quasi-biennial-oscillation QBO on tropopause dynamics at longer period scales leading ultimately to the evolution of strong El Nino events of global economic importance Gray et al 1992 GRL JMSJ As a result of this influence it is possible that the tropopause height may be increasing instead of decreasing with latitude from the equator in tropical regions during particular phase of QBO say westerly phase over the equator In the present work we report such observations using radiosonde data obtained from fourteen different tropical 30 N to 30 S radio-sounding stations located in the wide longitudinal zone of South East Asia South Pacific and Africa in the year 2004 The daily tropopause height determined at 00 00 and 12 00 hrs GMT is averaged for each month separately The tropopause height Cold Point Tropopause CPT is determined by noting the height of minimum temperature between 12 and 20 km It is observed further that the latitude variation of tropopause height in southern Hemisphere is much less when compared to that in the Northern Hemisphere The reason for this asymmetric characteristic of tropopause about the equator may be that greater fraction of the northern hemisphere is covered with land and it is ocean in the southern hemisphere Because of large variations in topography of the land and the associated thermal conductivity it is possible that convection activities of the

  12. Springtime photochemistry at northern mid and high latitudes

    NASA Astrophysics Data System (ADS)

    Wang, Yuhang; Ridley, Brian; Fried, Alan; Cantrell, Christopher; Davis, Douglas; Chen, Gao; Snow, Julie; Heikes, Brian; Talbot, Robert; Dibb, Jack; Flocke, Frank; Weinheimer, Andrew; Blake, Nicola; Blake, Donald; Shetter, Richard; Lefer, Barry; Atlas, Elliot; Coffey, Michael; Walega, Jim; Wert, Brian

    2003-02-01

    Physical and chemical properties of the atmosphere at 0-8 km were measured during the Tropospheric Ozone Production about the Spring Equinox (TOPSE) experiments from February to May 2000 at mid (40°-60°N) and high latitudes (60°-80°N). The observations were analyzed using a diel steady state box model to examine HOx and O3 photochemistry during the spring transition period. The radical chemistry is driven primarily by photolysis of O3 and the subsequent reaction of O(1D) and H2O, the rate of which increases rapidly during spring. Unlike in other tropospheric experiments, observed H2O2 concentrations are a factor of 2-10 lower than those simulated by the model. The required scavenging timescale to reconcile the model overestimates shows a rapid seasonal decrease down to 0.5-1 day in May, which cannot be explained by known mechanisms. This loss of H2O2 implies a large loss of HOx resulting in decreases in O3 production (10-20%) and OH concentrations (20-30%). Photolysis of CH2O, either transported into the region or produced by unknown chemical pathways, appears to provide a significant HOx source at 6-8 km at high latitudes. The rapid increase of in situ O3 production in spring is fueled by concurrent increases of the primary HOx production and NO concentrations. Long-lived reactive nitrogen species continue to accumulate at mid and high latitudes in spring. There is a net loss of NOx to HNO3 and PAN throughout the spring, suggesting that these long-term NOx reservoirs do not provide a net source for NOx in the region. In situ O3 chemical loss is dominated by the reaction of O3 and HO2, and not that of O(1D) and H2O. At midlatitudes, there is net in situ chemical production of O3 from February to May. The lower free troposphere (1-4 km) is a region of significant net O3 production. The net production peaks in April coinciding with the observed peak of column O3 (0-8 km). The net in situ O3 production at midlatitudes can explain much of the observed column O3

  13. Recent low-latitude freeze thaw on Mars

    NASA Astrophysics Data System (ADS)

    Page, David P.

    2007-07-01

    Outside polar latitudes, features corresponding to surface thaw have yet to be identified on Mars. The youthful gully landforms observed at mid-high latitude [Malin, M., Edgett, K., 2000. Science 288, 2330-2335] are the nearest candidate, but the source (and nature) of the gully carving agent remains controversial [e.g., Musselwhite, D.S., Swindle, T.D., Lunine, J.I., 2001. Geophys. Res. Lett. 28, 1283-1285; Mellon, M.T., Phillips, R.J., 2001. J. Geophys. Res. 106, 1-15; Knauth, L.P., Burt, D.M., 2002. Icarus 158, 267-271; Costard, F., Forget, F., Mangold, N., Peulvast, J.P., 2002. Science 295, 110-113; Christensen, P.R., 2003. Nature 422, 45-48; Treiman, A.H., 2003. J. Geophys. Res. 108]. At higher obliquity than the present epoch, near-surface ground ice should be present globally [Mellon, M.T., Jakosky, B.M., 1995. J. Geophys. Res. 100 (E6), 11781-11799], populated by condensation of atmospheric water vapour in the top few metres of the regolith, or emplaced as dusty ice sheets reaching down towards the equator. The latitudinal restriction of these gullies to regions poleward of ±30° appears to argue against a thaw component to their formation—since ground ice is present and stable at all latitudes at high obliquity, the current (low) obliquity regime should result in ground ice thaw at low latitudes, where insolation and daytime temperatures are currently greatest, and this is not observed. A previously undescribed meltwater sequence in the Cerberus plains, at 20° N/187° E, shows that comparable, but much more continuous, and mappable melting and surface runoff have occurred in the geologically recent past at near-equatorial latitudes on Mars. Polygonal ground in the Cerberus plains is seen by the Mars Global Surveyor Mars Orbiter Camera (MOC) to suffer sequential, regional-scale volatile-loss consistent with thaw of near-surface ground ice under periglacial conditions. This degradation is continuously sampled by a single MOC strip, showing an icy

  14. Latitude dependency of solar flare index-temperature relation occuring over middle and high latitudes of Atlantic-Eurasian region

    NASA Astrophysics Data System (ADS)

    Kilcik, A.; Özgüç, A.; Rozelot, J. P.

    2010-12-01

    By applying multitaper methods and Pearson test on the surface air temperature and flare index used as a proxy data for possible solar sources of climate-forcing, we investigated the signature of these variables on middle and high latitudes of the Atlantic-Eurasian region (Turkey, Finland, Romania, Ukraine, Cyprus, Israel, Lithuania, and European part of Russia). We considered the temperature and flare index data for the period ranging from January 1975 to the end of December 2005, which covers almost three solar cycles, 21st, 22nd, and 23rd.We found significant correlations between solar activity and surface air temperature over the 50-60° and 60-70° zones for cycle 22, and for cycle 23, over the 30-40°, 40-50°, and 50-60° zones.The most pronounced power peaks for surface air temperature found by multitaper method are around 1.2, 1.7, and 2.5 years which were reported earlier for some solar activity indicators. These results support the suggestion that there is signature of solar activity effect on surface air temperature of mid-latitudes.

  15. Tropical influence on boreal summer mid-latitude stationary waves

    NASA Astrophysics Data System (ADS)

    Douville, Hervé; Bielli, S.; Cassou, C.; Déqué, M.; Hall, N. M. J.; Tyteca, S.; Voldoire, A.

    2011-11-01

    While organized tropical convection is a well-known source of extratropical planetary waves, state-of-the-art climate models still show serious deficiencies in simulating accurately the atmospheric response to tropical sea surface temperature (SST) anomalies and the associated teleconnections. In the present study, the remote influence of the tropical atmospheric circulation is evaluated in ensembles of global boreal summer simulations in which the Arpege-Climat atmospheric General Circulation Model (GCM) is nudged towards 6-h reanalyses. The nudging is applied either in the whole tropical band or in a regional summer monsoon domain. Sensitivity tests to the experimental design are first conducted using prescribed climatological SST. They show that the tropical relaxation does not improve the zonal mean extratropical climatology but does lead to a significantly improved representation of the mid-latitude stationary waves in both hemispheres. Low-pass filtering of the relaxation fields has no major effect on the model response, suggesting that high-frequency tropical variability is not responsible for extratropical biases. Dividing the nudging strength by a factor 10 only decreases the magnitude of the response. Model errors in each monsoon domain contribute to deficiencies in the model's mid-latitude climatology, although an exaggerated large-scale subsidence in the central equatorial Pacific appears as the main source of errors for the representation of stationary waves in the Arpege-Climat model. Case studies are then conducted using either climatological or observed SST. The focus is first on summer 2003 characterized by a strong and persistent anticyclonic anomaly over western Europe. This pattern is more realistic in nudging experiments than in simulations only driven by observed SST, especially when the nudging domain is centred over Central America. Other case studies also show a significant tropical forcing of the summer mid-latitude stationary waves and

  16. Ionospheric vertical drift response at a mid-latitude station

    NASA Astrophysics Data System (ADS)

    Kouba, Daniel; Koucká Knížová, Petra

    2016-07-01

    Vertical plasma drift data measured at a mid-latitude ionospheric station Pruhonice (50.0 ° N, 14.6 ° E) were collected and analysed for the year 2006, a year of low solar and geomagnetic activity. Hence these data provide insight into the drift behaviour during quiet conditions. The following typical diurnal trend is evident: a significant decay to negative values (downward peak) at dawn; generally less pronounced downward peak at dusk hours. Magnitude of the downward drift varies during the year. Typically it reaches values about 20 ms-1 at dawn hours and 10 ms-1 at dusk hours. Maximum dawn magnitude of about 40 ms-1 has been detected in August. During daytime the vertical drifts increases from the initial small downward drifts to zero drift around noon and to small upward drifts in the afternoon. Night-time drift values display large variability around a near zero vertical drift average. There is a significant trend to larger downward drift values near dawn and a less pronounced decrease of the afternoon upward vertical drifts near sunset. Two regular downward peaks of the drift associated with the dawn and dusk are general characteristics of the analysed data throughout the year 2006. Their seasonal course corresponds to the seasonal course of the sunrise and sunset. The duration of prevailing negative drift velocities forming these peaks and thus the influence of the dawn/dusk on the drift velocity is mostly 1.5-3 h. The dawn effect on vertical drift tends to be larger than the effect of the dusk. The observed magnitude of the sunrise and sunset peaks show significant annual course. The highest variability of the magnitude is seen during winter. High variability is detected till March equinox and again after September equinox. Around solstice, both peaks reaches lowest values. After that, the magnitudes of the drift velocity increase smoothly till maxima in summer (August). The vertical drift velocity course is smooth between June solstice and September

  17. Solar transients disturbing the terrestrial magnetic environment at higher latitudes

    NASA Astrophysics Data System (ADS)

    Khan, Parvaiz A.; Tripathi, Sharad C.; Troshichev, O. A.; Waheed, Malik A.; Aslam, A. M.; Gwal, A. K.

    2014-02-01

    Geomagnetic field variations during five major Solar Energetic Particle (SEP) events of solar cycle 23 have been investigated in the present study. The SEP events of 1 October 2001, 4 November 2001, 22 November 2001, 21 April 2002 and 14 May 2005 have been selected to study the geomagnetic field variations at two high-latitude stations, Thule (77.5∘ N, 69.2∘ W) and Resolute Bay (74.4∘ E, 94.5∘ W) of the northern polar cap. We have used the GOES proton flux in seven different energy channels (0.8-4 MeV, 4-9 MeV, 9-15 MeV, 15-40 MeV, 40-80 MeV, 80-165 MeV, 165-500 MeV). All the proton events were associated with geoeffective or Earth directed CMEs that caused intense geomagnetic storms in response to geospace. We have taken high-latitude indices, AE and PC, under consideration and found fairly good correlation of these with the ground magnetic field records during the five proton events. The departures of the H component during the events were calculated from the quietest day of the month for each event and have been represented as Δ H THL and Δ H RES for Thule and Resolute Bay, respectively. The correspondence of spectral index, inferred from event integrated spectra, with ground magnetic signatures Δ H THL and Δ H RES along with Dst and PC indices have been brought out. From the correlation analysis we found a very strong correlation to exist between the geomagnetic field variation (Δ Hs) and high-latitude indices AE and PC. To find the association of geomagnetic storm intensity with proton flux characteristics we derived the correspondence between the spectral indices and geomagnetic field variations (Δ Hs) along with the Dst and AE index. We found a strong correlation (0.88) to exist between the spectral indices and Δ Hs and also between spectral indices and AE and PC.

  18. Climatology of GNSS ionospheric scintillation at high latitudes

    NASA Astrophysics Data System (ADS)

    Spogli, L.; Alfonsi, L.; de Franceschi, G.; Romano, V.; Aquino, M.; Dodson, A.; Mitchell, C. N.

    2009-12-01

    Under perturbed conditions caused by intense solar wind magnetosphere coupling, the ionosphere may become highly turbulent and irregularities, typically enhancements or depletions of the electron density embedded in the ambient ionosphere, can form. Such irregularities cause diffraction effects, mainly due to the random fluctuations of the refractive index of the ionosphere, on the satellites signals passing through them and consequent perturbations may cause GNSS navigation errors and outages, abruptly corrupting its performance. Due to the morphology of the geomagnetic field, whose lines are almost vertical at high latitude, polar areas are characterized by the presence of significant ionospheric irregularities having scale sizes ranging from hundreds of kilometers down to a few centimeters and with highly dynamic structures. The understanding of the effect of such phenomena is important, not only in preparation for the next solar cycle (24), whose maximum is expected in 2012, but also for a deeper comprehension of the dynamics of the high-latitude ionosphere. We analyze the fluctuations in the carrier frequency of the radio waves received on the ground, commonly referred to as ionospheric amplitude and phase scintillations, to investigate the physical processes causing them. The phase scintillations on GNSS signals are likely caused by ionospheric irregularities of scale size of hundreds of meters to few kilometers. The amplitude scintillations on GNSS signals are caused by ionospheric irregularities of scale size smaller than the Fresnel radius, which is of the order of hundreds of meters for GNSS signals, typically embedded into the patches. The Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the Institute of Engineering Surveying and Space Geodesy (IESSG) of the University of Nottingham manage the same kind of GISTM (GPS Ionospheric Scintillation and TEC Monitor) receivers over the European high and mid latitude regions and over Antarctica. The

  19. A new species of the South East Asian genus Sarax Simon, 1892 (Arachnida: Amblypygi: Charinidae) and synonymization of Sarax mediterraneus Delle Cave, 1986.

    PubMed

    Seiter, Michael; Wolff, Jonas; Hörweg, Christoph

    2015-01-01

    A new species of the whip spider genus Sarax Simon, 1892 from Cebu Island in the Philippines is described: Sarax huberi sp. nov. With the description of this species, the diversity of the genus is increased to three species in the Philippines. Some additional data on their natural environment and their specific habitat are presented and compared with sibling species. The synonymization of Sarax mediterraneus Delle Cave, 1986 with Sarax buxtoni (Gravely, 1915) is carried out. PMID:26623874

  20. A mathematical model of the middle and high latitude ionosphere

    NASA Technical Reports Server (NTRS)

    Schunk, R. W.

    1988-01-01

    A time-dependent three-dimensional model of the middle and high latitude ionosphere is described. The density distributions of six ion species NO(+), O(2+), N(2+), O(+), N(+), He(+), and the electron and ion temperatures are obtained from a numerical solution of the appropriate continuity, momentum, and energy equations. The equations are solved as a function of height for an inclined magnetic field at E and F region altitudes. The three-dimensional nature of the model is obtained by following flux tubes of plasma as they convect or corotate through a moving neutral atmosphere. The model takes account of field-aligned diffusion, cross-field electrodynamic drifts, thermospheric winds, polar wind escape, energy-dependent chemical reactions, neutral composition changes, ion production due to solar EUV radiation and auroral precipitation, thermal conduction, diffusion-thermal heat flow and local heating and cooling processes. The model also takes account of the offset between the geomagnetic and geographic poles.

  1. Rotational effects on convection simulated at different latitudes

    NASA Technical Reports Server (NTRS)

    Pulkkinen, Pentti; Tuominen, Ilkka; Brandenburg, Axel; Nordlund, Ake; Stein, Robert F.

    1993-01-01

    We simulate numerically convection inside the solar convection zone under the influence of rotation at different latitudes. The computational domain is a small rectangular box with stress-free upper and lower boundaries, and with periodicity assumed in the lateral directions. We study the transport of angular momentum, which is important for the generation of differential rotation. The sign and the latitudinal dependence of the horizontal Reynolds stress component turn out to be in good agreement with correlation measurements of sunspot proper motions and with predictions from the theory of the Lambda effect. We also investigate the other components of the Reynolds stress as well as the eddy heat flux tensor, both of which are needed in mean field models of differential rotation.

  2. Stratospheric flights with large polyethylene baloons from equatorial latitudes

    NASA Astrophysics Data System (ADS)

    Redkar, R. T.

    Starting with average 50% success for stratospheric balloon flights during 1959-1969 and attaining 100% success during 1972-1973, the success record dropped to 50% during 1974-1979. Through a critical analysis of 59 flights made from Hyderabad and 21 flights made from other equatorial bases, revised design criteria were proposed for balloons to be flown from equatorial latitudes, which were accepted by M/s Winzen International, Inc. (WII), U.S.A. and have again raised the success record to 93% for 15 flights made since April 1980. A revised analysis for 71 flights made from 1965 to 1984 has been presented. Stratospheric circulation over Hyderabad indicating predominance of easterlies with mesospheric westerlies descending occasionally into stratosphere has been discussed.

  3. CONDITIONED ANALYSIS OF HIGH-LATITUDE SOLAR WIND INTERMITTENCY

    SciTech Connect

    D'Amicis, R.; Consolini, G.; Bavassano, B.; Bruno, R.

    2012-08-10

    The solar wind is a turbulent medium displaying intermittency. Its intermittent features have been widely documented and studied, showing how the intermittent character is different in fast and slow wind. In this paper, a statistical conditioned analysis of the solar wind intermittency for a period of high-latitude fast solar wind is presented. In particular, the intermittent features are investigated as a function of the Alfvenic degree of fluctuations at a given scale. The results show that the main contribution to solar wind intermittency is due to non-Alfvenic structures, while Alfvenic increments are found to be characterized by a smaller level of intermittency than the previous ones. Furthermore, the lifetime statistics of Alfvenic periods are discussed in terms of a multiscale texture of randomly oriented flux tubes.

  4. Do wintering Harlequin Ducks forage nocturnally at high latitudes?

    USGS Publications Warehouse

    Rizzolo, D.J.; Esler, Daniel; Roby, D.D.; Jarvis, R.L.

    2005-01-01

    We monitored radio-tagged Harlequin Ducks (Histrionicus histrionicus) to determine whether nocturnal feeding was part of their foraging strategy during winter in south-central Alaska. Despite attributes of our study site (low ambient temperatures, harsh weather, short day length) and study species (small body size, high daytime foraging rates) that would be expected to favor nocturnal foraging, we found no evidence of nocturnal dive-feeding. Signals from eight radio-tagged Harlequin Ducks never exhibited signal loss due to diving during a total of 780 minutes of nocturnal monitoring. In contrast, the same eight birds exhibited signal loss during 62 ± 7% (SE) of 5-minute diurnal monitoring periods (total of 365 minutes of monitoring). Our results suggest that Harlequin Ducks in south-central Alaska face a stringent time constraint on daytime foraging during midwinter. Harlequin Ducks wintering at high latitudes, therefore, may be particularly sensitive to factors that increase foraging requirements or decrease foraging efficiency.

  5. A CCD survey for faint high-latitude carbon stars

    NASA Technical Reports Server (NTRS)

    Green, Paul J.; Margon, Bruce; Anderson, Scott F.; Cook, Kem H.

    1994-01-01

    We describe a wide-area CCD survey to search for faint high-latitude carbon (FHLC) stars. Carbon giants provide excellent probes of the structure and kinematics of the outer Galactic halo. We use two-color photometric selection with large-format CCDs to cover 52 sq deg of sky to a depth of about V = 18. Of 94 faint C star candidates from our own CCD survey, one highly ranked V = 17 candidate was found to have a strong carbon and CN bands. We estimate that, to a depth of V = 18, the surface density of FHLC stars is 0.02 deg(exp -2). An updated FHLC sample is used to constrain halo kinematic and structural parameters. Although larger samples are needed, the effective radius of FHLC giants, assuming a de Vancouleurs law distribution, is larger than that for Galactic globular clusters.

  6. High latitude equivalent current systems during extremely quiet times

    NASA Technical Reports Server (NTRS)

    Rostoker, G.; Chen, A. J.; Yasuhara, F.; Akasofu, S.-I.; Kawasaki, K.

    1974-01-01

    The magnetic perturbation patterns in the polar cap and auroral zone regions are obtained for extremely quiet days using two different techniques. It is shown that the form of the equivalent current flow pattern is extremely sensitive to the level of quietness, and that even so-called quiet days are at times disturbed by substorm activity. Certain characteristic equivalent flow not typically observed during substorms is noted in the polar cap, and this flow appears to be associated with effects of polar cap perturbations discussed by Svalgaard (1973). A region of equatorward flow at high latitudes near the dawn meridian, appears to be Hall current driven by an eastward electric field. The dayside sub-auroral zone is dominated by the Sq-current system, while the nightside shows no significant current flow in the absence of substorm activity.

  7. VELOCITY SPECTRUM FOR H I AT HIGH LATITUDES

    SciTech Connect

    Chepurnov, A.; Lazarian, A.; Stanimirovic, S.; Heiles, Carl; Peek, J. E. G.

    2010-05-10

    In this paper, we present the results of the statistical analysis of high-latitude H I turbulence in the Milky Way. We have observed H I in the 21 cm line, obtained with the Arecibo{sup 3} L-Band Feed Array receiver at the Arecibo radio telescope. For recovering velocity statistics, we have used the velocity coordinate spectrum (VCS) technique. In our analysis, we have used direct fitting of the VCS model, as its asymptotic regimes are questionable for Arecibo's resolution, given the restrictions from thermal smoothing of the turbulent line. We have obtained a velocity spectral index of 3.87 {+-} 0.11, an injection scale of 140 {+-} 80 pc, and an H I cold phase temperature of 52 {+-} 11 K. The spectral index is steeper than the Kolmogorov index and can be interpreted as being due to shock-dominated turbulence.

  8. Anisotropy of high-latitude nighttime F region irregularities

    SciTech Connect

    Livingston, R.C.; Rino, C.L.; Owen, J.; Tsunoda, R.T.

    1982-12-01

    The anisotropy of intermediate-scale, F region irregularities in the nighttime auroral zone is described. The study is based upon spaced-receiver phase scintillation measurements made with the Wideband satellite at Poker Flat, Alaska. A systematic dependence of irregularity anisotropy with local time and magnetic latitude is observed, suggesting convective control. Sheetlike irregularities are confined to the zone of east-west drift near the equatorward boundary of the auroral zone, and at the flow reversal, or Harang discontinuity, the cross-field extension of the sheets is reduced. The extension of rodlike irregularities, which are observed poleward of the zonal convection boundary, also shows apparent convection dominance. Mechanisms for convection control of the anisotropy are discussed.

  9. High-latitude irregularity spectra deduced from scintillation measurements

    SciTech Connect

    Wernik, A.W.; Gola, M.; Liu, C.H.; Franke, S.J. Illinois Univ., Urbana )

    1990-10-01

    High-latitude scintillation data show that the strength and spectral index of intensity scintillation are dependent on the propagation geometry. It is shown here that anisotropic irregularity spectra, with different indices along and across the magnetic field, lead to geometrical effects similar to those observed. In general, the spectrum along the magnetic field is steeper than that across the field, and the difference is more pronounced for nighttime conditions. Spectral anisotropy can be interpreted as a size-dependent irregularity anisotropy. It is found that large-scale irregularities in the daytime and nighttime ionosphere are almost isotropic, while small-scale irregularities are anisotropic and considerably more so at night than during the day. It is shown that anisotropic irregularity spectra could account for the observed scintillation and in situ temporal spectra with frequency-dependent slope. 26 refs.

  10. Center is at Latitude 30 Degrees North, Longitude 270 Degrees

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Center of the orthographic projection is at latitude 30 degrees N., longitude 270 degrees. The north polar residual ice cap of the Planum Boreum region, which is cut by spiral-patterned troughs, is located at top. The upper part is marked by a large depression, Isidis basin, which contains light-colored plains. The upper part also includes the light-colored smooth plains of Elysium Planitia and dark plains of Vastitas Borealis. Together, these form a vast expanse of contiguous plains. Toward the bottom, on the other hand, the southern hemisphere is almost entirely made up of heavily cratered highlands. At bottom left, a conspicuous, relatively bright circular depression marks the ancient large Hellas impact basin.

  11. Theoretical predictions of latitude dependencies in the solar wind

    NASA Technical Reports Server (NTRS)

    Winge, C. R., Jr.; Coleman, P. J., Jr.

    1974-01-01

    Results are presented which were obtained with the Winge-Coleman model for theoretical predictions of latitudinal dependencies in the solar wind. A first-order expansion is described which allows analysis of first-order latitudinal variations in the coronal boundary conditions and results in a second-order partial differential equation for the perturbation stream function. Latitudinal dependencies are analytically separated out in the form of Legendre polynomials and their derivative, and are reduced to the solution of radial differential equations. This analysis is shown to supply an estimate of how large the coronal variation in latitude must be to produce an 11 km/sec/deg gradient in the radial velocity of the solar wind, assuming steady-state processes.

  12. First order latitude effects in the solar wind

    NASA Technical Reports Server (NTRS)

    Winge, C. R., Jr.; Coleman, P. J., Jr.

    1974-01-01

    The Weber-Davis model of the solar wind is generalized to include the effects of latitude. The principal assumptions of perfect electrical conductivity, rotational symmetry, a polytropic relation between pressure and density, and a flow aligned magnetic field in a system rotating with the Sun, are retained. The original three dimensional magnetohydrodynamic flow problem is reduced to a two dimensional hydrodynamic flow problem. The solution at 1 Au is most sensitive to a latitudinal dependence in the coronal boundary temperature and least sensitive to a latitudinal dependence in the magnetic field magnitude. A solution obtained for an approximate dipolar variation in the coronal magnetic field magnitude predicts that the latitudinal flow is initially toward the equator due to magnetic channeling; however, this effect is rapidly overcome and the latitudinal flow at 1 Au is toward the pole and not significantly different from the solution for constant boundary conditions.

  13. Electron density distributions in the high-latitude magnetosphere

    NASA Technical Reports Server (NTRS)

    Persoon, Ann M.

    1988-01-01

    Electron density profiles were constructed to study the plasma density depletions in the nightside auroral zone and the density variations with increasing altitude in the polar cap, using electric field spectrum measurements from the plasma wave instrument on DE-1. Sharply defined regions of depleted plasma densities were commonly observed on nightside auroral field lines, in which electron densities were strongly depleted in relation to the adjacent plasmaspheric and polar densities, forming a low-density cavity at about 70 deg invariant latitude. A correlation was found between low auroral plasma densities, upflowing ion distributions, and an energetic precipitating electron population, indicating that electron density depletions in the nightside auroral zone are directly associated with auroral acceleration processes.

  14. Singular Plasma Disturbance in the Low-Latitude F Region

    NASA Technical Reports Server (NTRS)

    Singh, Sardul; Johnson, F. S.; Heelis, R. A.

    1999-01-01

    We describe here a new phenomenon characterized by unusual patterns of ion drifts inside ion density depletion regions observed by the AE-E satellite in the low-latitude F region. In about 30 depletions, vertical ion drift relative to the background was upward on the western sides, downward on the eastern sides, and zero near the middle where the density depletion was greatest. These drift characteristics are distinct from those observed in plasma bubble depletions. The structures reported here were observed on circular orbits below 300 km altitude and had density depletions of up to 2 orders of magnitude or more below the ambient ion density. The upward and downward drift excursions were up to 200 m/s relative to the background. Almost all these structures were observed over oceans or near coasts and largely between +/- 10 deg and +/- 30 deg clip latitude. The structures were observed mostly as isolated, single depletion regions with the majority of them about 250 km wide in the east-west direction. They occurred during quiet magnetic conditions with near-equal occurrence frequencies in the premidnight and postmidnight periods. The characteristic density and drift signatures indicate westward propagating disturbances in which the bottomside F layer is first lifted and then returned back to its original position, leaving the ionosphere undisturbed after the disturbance passes by. The estimated speed of these disturbances is of the order of 200 m/s. These unique solitary plasma disturbances, which we designate as singular plasma disturbances, are associated with a propagating source of E x B drift, not driven by neutral perturbations at the altitude of observation.

  15. On the surface composition of Triton's southern latitudes

    NASA Astrophysics Data System (ADS)

    Holler, B. J.; Young, L. A.; Grundy, W. M.; Olkin, C. B.

    2016-03-01

    We present the results of an investigation to determine the longitudinal (zonal) distributions and temporal evolution of ices on the surface of Triton. Between 2002 and 2014, we obtained 63 nights of near-infrared (0.67-2.55 μ m) spectra using the SpeX instrument at NASA's Infrared Telescope Facility (IRTF). Triton has spectral features in this wavelength region from N2, CO, CH4, CO2, and H2O. Absorption features of ethane (C2H6) and 13CO are coincident at 2.405 μ m, a feature that we detect in our spectra. We calculated the integrated band area (or fractional band depth in the case of H2O) in each nightly average spectrum, constructed longitudinal distributions, and quantified temporal evolution for each of the chosen absorption bands. The volatile ices (N2, CO, CH4) show significant variability over one Triton rotation and have well-constrained longitudes of peak absorption. The non-volatile ices (CO2, H2O) show poorly-constrained peak longitudes and little variability. The longitudinal distribution of the 2.405 μ m band shows little variability over one Triton rotation and is 97 ± 44 ° and 92 ± 44 ° out of phase with the 1.58 μ m and 2.35 μ m CO bands, respectively. This evidence indicates that the 2.405 μ m band is due to absorption from non-volatile ethane. CH4 absorption increased over the period of the observations while absorption from all other ices showed no statistically significant change. We conclude from these results that the southern latitudes of Triton are currently dominated by non-volatile ices and as the sub-solar latitude migrates northwards, a larger quantity of volatile ice is coming into view.

  16. Naturally occurring allele diversity allows potato cultivation in northern latitudes.

    PubMed

    Kloosterman, Bjorn; Abelenda, José A; Gomez, María del Mar Carretero; Oortwijn, Marian; de Boer, Jan M; Kowitwanich, Krissana; Horvath, Beatrix M; van Eck, Herman J; Smaczniak, Cezary; Prat, Salomé; Visser, Richard G F; Bachem, Christian W B

    2013-03-14

    Potato (Solanum tuberosum L.) originates from the Andes and evolved short-day-dependent tuber formation as a vegetative propagation strategy. Here we describe the identification of a central regulator underlying a major-effect quantitative trait locus for plant maturity and initiation of tuber development. We show that this gene belongs to the family of DOF (DNA-binding with one finger) transcription factors and regulates tuberization and plant life cycle length, by acting as a mediator between the circadian clock and the StSP6A mobile tuberization signal. We also show that natural allelic variants evade post-translational light regulation, allowing cultivation outside the geographical centre of origin of potato. Potato is a member of the Solanaceae family and is one of the world's most important food crops. This annual plant originates from the Andean regions of South America. Potato develops tubers from underground stems called stolons. Its equatorial origin makes potato essentially short-day dependent for tuberization and potato will not make tubers in the long-day conditions of spring and summer in the northern latitudes. When introduced in temperate zones, wild material will form tubers in the course of the autumnal shortening of day-length. Thus, one of the first selected traits in potato leading to a European potato type is likely to have been long-day acclimation for tuberization. Potato breeders can exploit the naturally occurring variation in tuberization onset and life cycle length, allowing varietal breeding for different latitudes, harvest times and markets. PMID:23467094

  17. Improved fire radiative energy estimation in high latitude ecosystems

    NASA Astrophysics Data System (ADS)

    Melchiorre, A.; Boschetti, L.

    2014-12-01

    Scientists, land managers, and policy makers are facing new challenges as fire regimes are evolving as a result of climate change (Westerling et al. 2006). In high latitudes fires are increasing in number and size as temperatures increase and precipitation decreases (Kasischke and Turetsky 2006). Peatlands, like the large complexes in the Alaskan tundra, are burning more frequently and severely as a result of these changes, releasing large amounts of greenhouse gases. Remotely sensed data are routinely used to monitor the location of active fires and the extent of burned areas, but they are not sensitive to the depth of the organic soil layer combusted, resulting in underestimation of peatland greenhouse gas emissions when employing the conventional 'bottom up' approach (Seiler and Crutzen 1980). An alternative approach would be the direct estimation of the biomass burned from the energy released by the fire (Fire Radiative Energy, FRE) (Wooster et al. 2003). Previous works (Boschetti and Roy 2009; Kumar et al. 2011) showed that the sampling interval of polar orbiting satellite systems severely limits the accuracy of the FRE in tropical ecosystems (up to four overpasses a day with MODIS), but because of the convergence of the orbits, more observations are available at higher latitudes. In this work, we used a combination of MODIS thermal data and Landsat optical data for the estimation of biomass burned in peatland ecosystems. First, the global MODIS active fire detection algorithm (Giglio et al. 2003) was modified, adapting the temperature thresholds to maximize the number of detections in boreal regions. Then, following the approach proposed by Boschetti and Roy (2009), the FRP point estimations were interpolated in time and space to cover the full temporal and spatial extent of the burned area, mapped with Landsat5 TM data. The methodology was tested on a large burned area in Alaska, and the results compared to published field measurements (Turetsky et al. 2011).

  18. Implementing high-latitude biogeochemical processes into Earth System Models

    NASA Astrophysics Data System (ADS)

    Brovkin, Victor; Kleinen, Thomas; Cresto-Aleina, Fabio; Kloster, Silvia; Ilyina, Tatiana

    2016-04-01

    Projections of future climate changes suggest that air temperatures in the Arctic could rise to the levels unprecedented in the last million years. Sensitivity of carbon storages on land and shelves to climate change of that scale is highly uncertain. Earth System models (ESMs), consisting of atmosphere, ocean, land, and cryosphere components are the main tools to understand interactions between carbon cycle and climate. However, ESM representation of ecological and biogeochemical processes in the Arctic is extremely simplistic. For example, all ESMs agree that tree cover in the future warming scenarios will move northwards to the Arctic coast, but they ignore interactions between vegetation, permafrost, and disturbances such as fires, which are critical for vegetation dynamics in this region. Improving modeling of interactions between model components and their evaluation against growing observational evidence is a promising research area. The first attempts to account for the permafrost carbon dynamics in the ESM framework suggest that CO2 and CH4 emissions from high-latitude regions in the 21st century are relatively small, but they become much more significant afterwards due to committed climate changes. Therefore, extension of ESM simulations beyond 2100 is essential to estimate a proper scale of frozen carbon pool response to human-induced climate change. Additionally, inclusion of sub-sea permafrost component into ESMs is an active research area that brings together terrestrial and marine biogeochemical communities, as well as geologists analyzing climate proxies on glacial timescales. Another challenging aspect of biogeochemical interactions in Arctic is an extreme land surface heterogeneity. A mixture of wetlands, lakes, and vegetation-covered surfaces on fine local scale is not properly reflected in the model structure. A promising approach of dealing with scaling gaps in modeling high-latitude biogeochemical processes in ESMs will be presented.

  19. Satellite-based Wetland Mapping in High Latitudes

    NASA Astrophysics Data System (ADS)

    Shah, C. A.; Sheng, Y.; Smith, L. C.; Li, J.; Lyons, E.; Hinkel, K. M.; Winston, B.

    2008-12-01

    The flat terrain with poor drainage in high-latitude regions yields excessive wetlands characterized by saturated soil and riparian vegetation. These wetlands have long been recognized for their importance in the global carbon and hydrological cycles and continue to receive substantial attention. As a part of our NASA THP (Terrestrial Hydrology Program) project to assess recent terrestrial water storage change in Arctic lakes and wetlands, this paper addresses wetland mapping using remote sensing. Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) have been widely used in wetland mapping to quantify vegetation and underlying surface water. However, the performance of such indices is limited by the "mixed pixel" effect due to the fact that a wetland pixel comprises of mixed spectral responses of water and vegetation. Hence, we propose to estimate the abundance of each of these surface materials within a pixel through a spectral unmixing approach. The general assumption in spectral unmixing is that the observed pixel spectrum is a linear combination of several endmembers denoting pure material spectra available in existing spectral libraries. The limited and poor availability of ground truth in regional-scale research however prohibits the use of library spectra, necessitating the use of unsupervised spectral unmixing techniques. The proposed research applies independent component analysis (ICA) to perform a non-orthogonal linear transformation of the multi-spectral Landsat images for an unsupervised spectral unmixing to obtain water and vegetation abundances, which are crucial to wetland mapping. The method is highly efficient with a high-level of replicability and automation. Performance of the proposed approach is evaluated quantitatively, and a high accuracy is achieved in high-latitude wetland mapping.

  20. Speciation, Ecological Opportunity, and Latitude (American Society of Naturalists Address).

    PubMed

    Schluter, Dolph

    2016-01-01

    Evolutionary hypotheses to explain the greater numbers of species in the tropics than the temperate zone include greater age and area, higher temperature and metabolic rates, and greater ecological opportunity. These ideas make contrasting predictions about the relationship between speciation processes and latitude, which I elaborate and evaluate. Available data suggest that per capita speciation rates are currently highest in the temperate zone and that diversification rates (speciation minus extinction) are similar between latitudes. In contrast, clades whose oldest analyzed dates precede the Eocene thermal maximum, when the extent of the tropics was much greater than today, tend to show highest speciation and diversification rates in the tropics. These findings are consistent with age and area, which is alone among hypotheses in predicting a time trend. Higher recent speciation rates in the temperate zone than the tropics suggest an additional response to high ecological opportunity associated with low species diversity. These broad patterns are compelling but provide limited insights into underlying mechanisms, arguing that studies of speciation processes along the latitudinal gradient will be vital. Using threespine stickleback in depauperate northern lakes as an example, I show how high ecological opportunity can lead to rapid speciation. The results support a role for ecological opportunity in speciation, but its importance in the evolution of the latitudinal gradient remains uncertain. I conclude that per capita evolutionary rates are no longer higher in the tropics than the temperate zone. Nevertheless, the vast numbers of species that have already accumulated in the tropics ensure that total rate of species production remains highest there. Thus, tropical evolutionary momentum helps to perpetuate the steep latitudinal biodiversity gradient. PMID:26814593

  1. Recent low-latitude freeze thaw on Mars

    NASA Astrophysics Data System (ADS)

    Page, David P.

    2007-07-01

    Outside polar latitudes, features corresponding to surface thaw have yet to be identified on Mars. The youthful gully landforms observed at mid-high latitude [Malin, M., Edgett, K., 2000. Science 288, 2330-2335] are the nearest candidate, but the source (and nature) of the gully carving agent remains controversial [e.g., Musselwhite, D.S., Swindle, T.D., Lunine, J.I., 2001. Geophys. Res. Lett. 28, 1283-1285; Mellon, M.T., Phillips, R.J., 2001. J. Geophys. Res. 106, 1-15; Knauth, L.P., Burt, D.M., 2002. Icarus 158, 267-271; Costard, F., Forget, F., Mangold, N., Peulvast, J.P., 2002. Science 295, 110-113; Christensen, P.R., 2003. Nature 422, 45-48; Treiman, A.H., 2003. J. Geophys. Res. 108]. At higher obliquity than the present epoch, near-surface ground ice should be present globally [Mellon, M.T., Jakosky, B.M., 1995. J. Geophys. Res. 100 (E6), 11781-11799], populated by condensation of atmospheric water vapour in the top few metres of the regolith, or emplaced as dusty ice sheets reaching down towards the equator. The latitudinal restriction of these gullies to regions poleward of ±30° appears to argue against a thaw component to their formation—since ground ice is present and stable at all latitudes at high obliquity, the current (low) obliquity regime should result in ground ice thaw at low latitudes, where insolation and daytime temperatures are currently greatest, and this is not observed. A previously undescribed meltwater sequence in the Cerberus plains, at 20° N/187° E, shows that comparable, but much more continuous, and mappable melting and surface runoff have occurred in the geologically recent past at near-equatorial latitudes on Mars. Polygonal ground in the Cerberus plains is seen by the Mars Global Surveyor Mars Orbiter Camera (MOC) to suffer sequential, regional-scale volatile-loss consistent with thaw of near-surface ground ice under periglacial conditions. This degradation is continuously sampled by a single MOC strip, showing an icy

  2. Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

    NASA Astrophysics Data System (ADS)

    Grocott, A.; Wild, J. A.; Milan, S. E.; Yeoman, T. K.

    2008-12-01

    Using data from the Super Dual Auroral Radar Network (SuperDARN) we investigate the ionospheric convection response to magnetospheric substorms. Substorms were identified using the Far Ultraviolet (FUV) instrument on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, and were then grouped according to the magnetic latitude of their onset. A superposed epoch analysis of the ionospheric convection patterns for each latitude group was then performed using radar data for the interval 60 minutes before onset to 90 minutes after. It is found that lower latitude onset substorms are associated with generally more enhanced convection than the higher latitude substorms, although they suffer from the most significant localised suppression of the flow in the midnight sector during the expansion phase. On the other hand, the higher-latitude events are associated with a significant and rapid increase in the nightside convection following substorm onset. These results suggest differences in the electrodynamics associated with substorms occurring at different latitudes.

  3. Precipitation correlation between convective available potential energy, convective inhibition and saturation fraction in middle latitudes

    NASA Astrophysics Data System (ADS)

    Barkiđija, Sanda; Fuchs, Željka

    2013-04-01

    Saturation fraction (SF), convective inhibition (CIN) and convective available potential energy (CAPE) are discussed to see with which of these parameters' precipitation rate is better correlated in the middle latitudes. The study is based on measurements from 20 European stations for the period of 1972-2009. We also use the results of the Global Forecasting System (GFS) model to see how mentioned parameters behave in numerical models. Our research results indicate that CAPE is not a good measure of precipitation rate for all latitudes, although, in model results, CAPE and precipitation rate are found to be better correlated for middle latitudes then in higher latitudes and tropical regions. The best correlation with precipitation rate in middle latitudes is one with SF. Our results suggest that moisture is underestimated in numerical models for middle latitudes and encourage further work in including SF or similar parameter into precipitation parameterization in addition to the current one.

  4. Low- and mid-latitude ionospheric electric fields during the January 1984 GISMOS campaign

    NASA Technical Reports Server (NTRS)

    Fejer, B. G.; Kelley, M. C.; Senior, C.; De La Beaujardiere, O.; Lepping, R.

    1990-01-01

    The electrical coupling between the high-, middle-, and low-latitude ionospheres during January 17-19, 1984 is examined, using interplanetary and high-latitude magnetic field data together with F region plasma drift measurements from the EISCAT, Sondre Stromfjord, Millstone Hill, Saint-Santin, Arecibo, and Jicamarca incoherent scatter radars. The penetration both the zonal and meridional electric field components of high-latitude origin into the low-latitude and the equatorial ionospheres are studied. The observations in the postmidnight sector are used to compare the longitudinal variations of the zonal perturbation electric field with predictions made from global convection models. The results show that the meridional electric field perturbations are considerably more attenuated with decreasing latitude than the zonal fluctuations. It is concluded that variations in the meridional electric field at low latitudes are largely due to dynamo effects.

  5. Multi-spacecraft observations of heliographic latitude-longitude structure in the solar wind

    NASA Technical Reports Server (NTRS)

    Rhodes, E. J., Jr.; Smith, E. J.

    1981-01-01

    The heliographic latitude-longitude structure of high speed solar winds observed prior to the maximum of sunspot cycle 20 is investigated by multi-spacecraft comparisons. It is shown that differences in solar wind structures are due to two different kinds of spatial structures. One structure is found to be consistent with the simultaneous existence of a single, broad stream at latitudes above 7 deg N and a series of narrow streams at lower latitudes, while the other is consistent with the existence of a latitudinally sloping stream boundary near the solar equator. For latitude separations less than 3.5 deg, cross-correlations of Explorer-Mariner velocities show only previously reported systematic increases in velocity with latitude, and for latitude separations from 3.5 to 6.2 deg, differences in high speed streams shift in longitude and/or amplitude are also identified on a timescale of one solar rotation.

  6. A two-dimensional array study of low-latitude PC 5 geomagnetic pulsations

    SciTech Connect

    Ziesolleck, C.W.S.; Chamalaun, F.H.

    1993-08-01

    The authors report a study of Pc 5 wave activity made using the Australia Wide Array of Geomagnetic Stations, to study such wave activity at low latitudes. They filtered the signals to look at polarization properties. They found little frequency variation across the latitude or longitude range sampled. There was a general amplitude decrease toward lower latitudes, a variation in the polarization on a daily basis, and phase variations across the array.

  7. Additional measurements of the high-latitude sunspot rotation rate /Research note/

    NASA Technical Reports Server (NTRS)

    Landman, D. A.; Takushi, J. T.

    1981-01-01

    Sunspot rotation rate measurements at high sunspot latitudes are reported for the period 1966-68, based on ten spots at latitudes greater than about 28 deg from H-alpha patrol records for this period. A sidereal rotation rate of 13.70 + or - 0.07 deg/day was found on the average, at 31.05 + or - 0.01 deg. Taken together, the full set of measurements in this latitude regime yield a rotation rate that is in excellent agreement with the result derived by Newton and Nunn (1951) from recurrent spots at lower latitudes throughout the six cycles from 1878 to 1944.

  8. Additional measurements of the high-latitude sunspot rotation rate /Research note/

    NASA Astrophysics Data System (ADS)

    Landman, D. A.; Takushi, J. T.

    1981-10-01

    Sunspot rotation rate measurements at high sunspot latitudes are reported for the period 1966-68, based on ten spots at latitudes greater than about 28 deg from H-alpha patrol records for this period. A sidereal rotation rate of 13.70 + or - 0.07 deg/day was found on the average, at 31.05 + or - 0.01 deg. Taken together, the full set of measurements in this latitude regime yield a rotation rate that is in excellent agreement with the result derived by Newton and Nunn (1951) from recurrent spots at lower latitudes throughout the six cycles from 1878 to 1944.

  9. Determination of solar proton fluxes and energies at high solar latitudes by UV radiation measurements

    NASA Technical Reports Server (NTRS)

    Witt, N.; Blum, P. W.; Ajello, J. M.

    1981-01-01

    The latitudinal variation of the solar proton flux and energy causes a density increase at high solar latitudes of the neutral gas penetrating the heliosphere. Measurements of the neutral density by UV resonance radiation observations from interplanetary spacecraft thus permit deductions on the dependence of the solar proton flux on heliographic latitude. Using both the results of Mariner 10 measurements and of other off-ecliptic solar wind observations, the values of the solar proton fluxes and energies at polar heliographic latitudes are determined for several cases of interest. The Mariner 10 analysis, together with IPS results, indicate a significant decrease of the solar proton flux at polar latitudes.

  10. High latitude hydrological changes during the Eocene Thermal Maximum 2

    NASA Astrophysics Data System (ADS)

    Krishnan, Srinath; Pagani, Mark; Huber, Matthew; Sluijs, Appy

    2014-10-01

    -enriched signals at the base of the event, including (1) intense local drying and cooling leading to evaporative 2H-enrichment; (2) changes in frequency/intensity of storm events and its impact on high latitude amount effects; and (3) changes in low-latitude temperatures. Evidence for hydrological shifts at the base of both hyperthermals suggests that hydrological change or the factors promoting hydrological change played a role in triggering the release of greenhouse gases. Generation of similar high-resolution isotopic- and temperature records at other latitudes is crucial for understanding the causal links between temperature and hydrological changes and may help constrain the source and mechanism of carbon release that triggered the early Eocene hyperthermals.

  11. Distance to northern high-latitude HI shells

    NASA Astrophysics Data System (ADS)

    Puspitarini, L.; Lallement, R.

    2012-09-01

    Context. A detailed three-dimensional (3D) distribution of interstellar matter in the solar neighborhood is increasingly necessary. It would allow a more realistic computation of photons and cosmic rays propagation, which is of prime importance for microwave and gamma-ray background emission interpretation, as well as a better understanding of the chain of phenomena that gave rise to the main local structures. Aims: As part of a 3D mapping program, we aim at assigning a precise distance to the high-latitude HI gas, in particular the northern part (b ≥ 55°) of the shell associated with the conspicuous radio continuum Loop I. This shell is thought to be the expanding boundary of an interstellar bubble inflated and recently reheated by the strong stellar winds of the nearby Scorpius-Centaurus OB associations. Methods: We recorded high-resolution spectra of 30 A-type target stars located at various distances in the direction of the northern part of Loop I. Interstellar neutral sodium and singly ionized calcium absorptions (NaI 5889-5895 and CaII K-H 3934-3968 Å) are modeled and compared with the HI emission spectra from the LAB Survey. Results: About two-thirds of our stellar spectra possess narrow interstellar lines, while the remaining spectra show no absorption at all. Narrow lines are located at the velocity of the main, low-velocity Loop 1 HI shell ([-6, +1] km s-1 in the LSR). Using Hipparcos distances to the target stars, we show that the closest boundary of the b ≥ + 70° part of this low-velocity Loop I arch is located at of 98 ± 6 pc. The corresponding interval for the lower-latitude part (55 ≤ b ≤ 70°) is 95-157 pc. However, since the two structures are apparently connected, the lower limit is more likely. At variance with this shell, the second HI structure (b ≥ +85°), which is characterized by LSR Doppler velocities centered at -30 km s-1, is NOT detected in any of the optical spectra. It is located beyond 200 parsecs or totally depleted in

  12. Trends in column ozone based on TOMS data - Dependence on month, latitude, and longitude

    NASA Technical Reports Server (NTRS)

    Niu, Xufeng; Frederick, John E.; Stein, Michael L.; Tiao, George C.

    1992-01-01

    On the basis of the TOMS satellite column ozone data in latitudes 70 deg S-70 deg N from November 1978 to May 1990, a statistical model is used to estimate the trends in ozone as a function of latitude, longitude, and month. The trends in the TOMS ozone data are highly seasonal and dependent on location. Near the equator, the estimated monthly trends are not significantly different from zero. For high latitudes, most of the estimated monthly trends are negative. In January, February, and March, there are some positive trend estimates in the western hemisphere around latitude 60 deg N. The most negative trends for these three months also appear in the high latitudes of the northern hemisphere. Starting in June, more negative trends appear in the latitudes 50 deg S-70 deg S than the trends in the rest of the world considered. A large depletion develops during the spring time (September to November) in the southern high-latitude region, and the area of peak ozone decline is moving eastward during the period. The largest negative trends (about -29 percent per decade) for the area considered in this study appear in October around the latitude 70 deg S and longitudes 20 deg W-100 deg W region. For the northern hemisphere, the year-round trend estimates for latitudes 30 deg N-70 deg N range from -0.96 percent to -7.43 percent per decade. In the latitudes 30 deg N-50 deg N, the winter trend estimates are more negative than those for the summer and the fall. However, this pattern did not hold for latitudes 50 deg N-70 deg N.

  13. Autonomous, continuously recording broadband seismic stations at high-latitude

    NASA Astrophysics Data System (ADS)

    Beaudoin, B.; Parker, T.; Bonnett, B.; Tytgat, G.; Anderson, K.; Fowler, J.

    2009-04-01

    IRIS PASSCAL is in the third year of an NSF funded development and acquisition effort to establish a pool of cold-hardened seismic stations specifically for high-latitude broadband deployments. We have two complete years of field trials and have successfully recorded continuous seismic data during both years with data recovery rates of ~90%. Our design is premised on a 2W autonomous system recording to local media, capable of lasting two years without service. The system is composed of four new design elements: a heavily insulated station enclosure; a state-of-health (SOH) Iridium modem; a light weight, easily deployed solar panel mount; and a power system that includes power switching between primary (Lithium Thionyl Chloride) and secondary batteries. The station enclosures have proved most critical in keeping our data acquisition systems operating within manufacturer specifications and primary batteries within a 50-70% efficiency range. Enclosures with 2.5cm-thick vacuum panels and 5cm of foam insulation have kept interior enclosure temperatures 25-30°C above background (typically below -50°C). This austral summer we are deploying version three of our enclosures. Significant changes in the design include thicker vacuum panels (5cm), more robust construction, and simplified cable routing. An important aspect of our station design is easy installation and minimal weight. To simplify installation our station enclosures are packed with datalogger, SOH communications and batteries in the lab or base camp, so that access to the internal components is not necessary at the remote site. Bulkhead connectors allow a user to fully interact with the system without ever having to open the enclosure. Solar panel mounts are also fully constructed prior to deployment. Once on site, digging two large holes (one for the enclosure and one for the broadband seismometer) and constructing the site takes roughly 2 hours. A station designed to record continuously for 12-14 months is

  14. Paleoclimate records at high latitude in Arctic during the Paleogene

    NASA Astrophysics Data System (ADS)

    Salpin, Marie; Schnyder, Johann; Baudin, François; Suan, Guillaume; Labrousse, Loïc; Popescu, Speranta; Suc, Jean-Pierre

    2015-04-01

    Paleoclimate records at high latitude in Arctic during the Paleogene SALPIN Marie1,2, SCHNYDER Johann1,2, BAUDIN François1,2, SUAN Guillaume3, LABROUSSE Loïc1,2, POPESCU Speranta4, SUC Jean-Pierre1,4 1: Sorbonne Universités, UPMC Univ Paris 06, UMR 7193, Institut des Sciences de la Terre Paris (iSTeP), F 75005, Paris, France 2: CNRS, UMR 7193, Institut des Sciences de la Terre Paris (iSTeP), F 75005 Paris, France 3: UCB Lyon 1, UMR 5276, LGLTPE, 69622 Villeurbanne Cedex, France 4: GEOBIOSTRATDATA.CONSULTING, 385 Route du Mas Rillier 69140 Rillieux la Pape, France The Paleogene is a period of important variations of the Earth climate system either in warming or cooling. The climatic optima of the Paleogene have been recognized both in continental and marine environment. This study focus on high latitudes of the northern hemisphere, in the Arctic Basin. The basin has had an influence on the Cenozoic global climate change according to its polar position. Is there a specific behaviour of the Arctic Basin with respect to global climatic stimuli? Are there possible mechanisms of coupling/decoupling of its dynamics with respect to the global ocean? To answer these questions a unique collection of sedimentary series of Paleogene age interval has been assembled from the Laurentian margin in Northern Yukon (Canada) and from the Siberian margin (New Siberian Islands). Selected continental successions of Paleocene-Eocene age were used to study the response of the Arctic system to known global events, e.g. the climatic optima of the Paleogene (the so-called PETM, ETM2 or the Azolla events). Two sections of Paleocene-Eocene age were sampled near the Mackenzie delta, the so-called Coal Mine (CoMi) and Caribou Hills (CaH) sections. The aim of the study is to precise the climatic fluctuations and to characterise the source rock potential of the basin, eventually linked to the warming events. This study is based on data of multi-proxy analyses: mineralogy on bulk and clay

  15. Statistical studies of impulsive events at high latitudes

    NASA Technical Reports Server (NTRS)

    Lin, Z. M.; Bering, E. A.; Benbrook, J. R.; Liao, B.; Lanzerotti, L. J.; Maclennan, C. G.; Wolfe, A. N.; Friis-Christensen, E.

    1995-01-01

    A statistical study has been made of the high-latitude impulsive events that were observed during the 1985-1986 South Pole Balloon Campaign. The events were selected by searching for unipolar pulses greater than or equal to 10 nT above background in the vertical component of the magnetic field on the ground and/or pedestal or 'W' shaped horizontal electric field perturbations greater than or equal to 10 mV/m in amplitude and accompanied by perturbations in the vertical electric field at balloon altitude. A main event list comprising 112 events was compiled from the 468 hours of data available. Three aspects of the events were examined: the solar wind conditions prior to the event, local time of observation, and intrinsic properties of the events. The local time distribution was obtained from the 112 entry main event list and was found to be nearly uniform across the dayside, with no midday gap. The event rate found using our low-amplitude selection criteria was 0.7 event/hr, comparable to expectations based on in situ studies of the magnetopause. A total of 42 events were found for which data were available from Interplanetary Monitoring Platform (IMP) 8. Of these events, 12 occurred when the Z(sub GSM) component (B(sub Z)) of the interplanetary magnetic field (IMF) was northward and 30 occurred when B(sub Z) was southward or fluctuating. Only three of the B(sub Z) northward cases and only five of the B(sub Z) southward cases were preceded by pressure pulses greater than 0.4 nPa in amplitude. Ten of the events were studied in detail by means of a model-fitting method discussed elsewhere. This method infers values of several parameters, including the total current flowing in a coaxial or monopole system and a two-dimensional dipole system. The intrinsic properties of the events showed that only approximately 10% of the total current contributed to momentum transfer to the high-latitude ionosphere, that the direction of the motion depended more on local time of

  16. Exposed Ice in the Northern Mid-Latitudes of Mars

    NASA Technical Reports Server (NTRS)

    Allen, Carlton C.

    2007-01-01

    Ice-Rich Layer: Polygonal features with dimensions of approximately 100 meters, bounded by cracks, are commonly observed on the martian northern plains. These features are generally attributed to thermal cracking of ice-rich sediments, in direct analogy to polygons in terrestrial polar regions. We mapped polygons in the northern mid-latitudes (30 to 65 N) using MOC and HiRISE images. Polygons are scattered across the northern plains, with a particular concentration in western Utopia Planitia. This region largely overlaps the Late Amazonian Astapus Colles unit, characterized by polygonal terrain and nested pits consistent with periglacial and thermokarst origins. Bright and Dark Polygonal Cracks: An examination of all MOC images (1997 through 2003) covering the study area demonstrated that, at latitudes of 55 to 65 N, most of the imaged polygons show bright bounding cracks. We interpret these bright cracks as exposed ice. Between 40 and 55 N, most of the imaged polygons show dark bounding cracks. These are interpreted as polygons from which the exposed ice has been removed by sublimation. The long-term stability limit for exposed ice, even in deep cracks, apparently lies near 55 N. Bright and Dark Spots: Many HiRISE and MOC frames showing polygons in the northern plains also show small numbers of bright and dark spots, particularly in western Utopia Planitia. Many of the spots are closely associated with collapse features suggestive of thermokarst. The spots range from tens to approximately 100 meters in diameter. The bright spots are interpreted as exposed ice, due to their prevalence on terrain mapped as ice rich. The dark spots are interpreted as former bright spots, which have darkened as the exposed ice is lost by sublimation. The bright spots may be the martian equivalents of pingos, ice-cored mounds found in periglacial regions on Earth. Terrestrial pingos from which the ice core has melted often collapse to form depressions similar to the martian dark spots

  17. Impact of Solar Proton Events on High Latitude Ionospheric Conditions

    NASA Astrophysics Data System (ADS)

    Aslam, A. M.; Gwal, Ashok Kumar; Mansoori, Azad Ahmad

    2016-07-01

    We investigate the ionospheric response to the solar protons which are accelerated to different energies (MeV-GeV) and thought to be originated at the solar atmosphere during the various energetic phenomena knows as solar transients viz. Solar Flares, Coronal Mass Ejections (CMEs). These transients are believed to be a manifestation of same energy release processes from a highly complex condition in the magnetic field configuration on the solar surface. We have taken six solar proton events (SPE) of solar cycle 23rd for analysis in the various energy bands of the protons. In order to find the ionospheric responses to these incoming solar protons ionospheric total electron content (TEC) is taken as the characteristic parameter. We have taken the data observed by GOES satellites which provides the data for different energy channels (0.8-4 MeV, 4-9 MeV, 9-15 MeV, 15-40 MeV, 40-80 MeV, 80-165 MeV, and 165-500 MeV). The enhancement in peak TEC (∆TEC) was then obtained for the high latitude station Davis (Lat-68.35, Lon 77.58). To find the association of this enhancement with proton flux characteristics we derived the correspondence between spectral indices and ∆TEC. We obtained a strong correlation (0.84) to exist between the spectral indices and ∆TEC.

  18. Ectotherm thermal stress and specialization across altitude and latitude.

    PubMed

    Buckley, Lauren B; Miller, Ethan F; Kingsolver, Joel G

    2013-10-01

    Gradients of air temperature, radiation, and other climatic factors change systematically but differently with altitude and latitude. We explore how these factors combine to produce altitudinal and latitudinal patterns of body temperature, thermal stress, and seasonal overlap that differ markedly from patterns based solely on air temperature. We use biophysical models to estimate body temperature as a function of an organism's phenotype and environmental conditions (air and surface temperatures and radiation). Using grasshoppers as a case study, we compare mean body temperatures and the incidence of thermal extremes along altitudinal gradients both under past and current climates. Organisms at high elevation can experience frequent thermal stress despite generally cooler air temperatures due to high levels of solar radiation. Incidences of thermal stress have increased more rapidly than have increases in mean conditions due to recent climate change. Increases in air temperature have coincided with shifts in cloudiness and solar radiation, which can exacerbate shifts in body temperature. We compare altitudinal thermal gradients and their seasonality between tropical and temperate mountains to ask whether mountain passes pose a greater physiological barrier in the tropics (Janzen's hypothesis). We find that considering body temperature rather than air temperature generally increases the amount of overlap in thermal conditions along gradients in elevation and thus decreases the physiological barrier posed by tropical mountains. Our analysis highlights the limitations of predicting thermal stress based solely on air temperatures, and the importance of considering how phenotypes influence body temperatures. PMID:23620253

  19. Latitude-Dependent Temperature Variations at the Solar Limb

    NASA Astrophysics Data System (ADS)

    Fivian, M. D.; Hudson, H. S.; Lin, R. P.; Zahid, H. J.

    2009-12-01

    We use observations from the solar aspect sensor of RHESSI to characterize the latitude dependence of the temperature of the photosphere at the solar limb. Previous observations have suggested the presence of a polar temperature excess as large as 1.5 K. The RHESSI observations, made with a rotating telescope in space, have great advantages in the rejection of systematic errors in the very precise photometry required for such an observation. This photometry is differential, i.e. relative to a mean limb-darkening function. The data base consists of about 1,000 images per day from linear CCDs with 1.73 arc sec square pixels, observing a narrow band (12nm FWHM) at 670 nm. Each image shows a chord crossing the disk at a different location as the spacecraft rotates and precesses around its average solar pointing. We fit an average limb-darkening function and reassemble the residuals into synoptic maps of differential intensity variations as function of position angle. We further mask these images against SOHO/EIT 284A images in order to eliminate magnetic regions. The analysis establishes a limit on the quadrupole dependence of temperature (brightness) on position angle of 0.04 +/- 0.02 K. This results in a possible correction of our precise measurement of the solar oblateness which is smaller than its rms error of 0.14 mas.

  20. Equatorial and Low-Latitudes Ionospheric Reaction to Solar Flares

    NASA Astrophysics Data System (ADS)

    Nicoli Candido, C. M.; Becker-Guedes, F.; Paula, E. R.; Takahashi, H.

    2015-12-01

    Solar X-ray and extreme ultraviolet (EUV) photons are responsible for ionizing the terrestrial atmosphere and create the ionosphere. During solar flares, a fast increase in the electron density at different altitude regions takes place due to the abrupt enhance of the X-ray and EUV fluxes reaching Earth. With these changes in the ionosphere, radio communication and navigation can be drastically affected. The magnitudes of these Space Weather events can be related to the X-ray peak brightness and duration, which drive the intensity of the ionosphere response when the associated electromagnetic wave hit the sunlit side of the Earth's atmosphere. Other aspects defining these changes in a particular region are the local time, the solar zenith angle, and the position of the flare in the solar disc for each event. In order to improve the understand of radio signal degradation and loss in the Brazilian sector due to solar abrupt electromagnetic emissions, total electron content (TEC) data obtained by a GPS network formed by tents of dual-frequency receivers spread all over Brazilian territory were analyzed. It was observed different ionospheric local changes during several X-ray events identified by GOES satellite regarding the 0.1-0.8 nm range, and some case studies were ponder for a more detailed analysis of these effects. Considering the results, we have made an estimation of the ionospheric disturbances range for a particular event with great chance to affect space based communications in the equatorial and low-latitude regions.

  1. The single event upset environment for avionics at high latitude

    SciTech Connect

    Sims, A.J.; Dyer, C.S.; Peerless, C.L. . Space and Communications Dept.); Johansson, K.; Pettersson, H. ); Farren, J. . Harwell Lab.)

    1994-12-01

    Modern avionic systems for civil and military applications are becoming increasingly reliant upon embedded microprocessors and associated memory devices. The phenomenon of single event upset (SEU) is well known in space systems and designers have generally been careful to use SEU tolerant devices or to implement error detection and correction (EDAC) techniques where appropriate. In the past, avionics designers have had no reason to consider SEU effects but is clear that the more prevalent use of memory devices combined with increasing levels of IC integration will make SEU mitigation an important design consideration for future avionic systems. To this end, it is necessary to work towards producing models of the avionics SEU environment which will permit system designers to choose components and EDAC techniques which are based on predictions of SEU rates correct to much better than an order of magnitude. Measurements of the high latitude SEU environment at avionics altitude have been made on board a commercial airliner. Results are compared with models of primary and secondary cosmic rays and atmospheric neutrons. Ground based SEU tests of static RAMs are used to predict rates in flight.

  2. Modelling the low-latitude boundary layer with reconnection entry

    NASA Technical Reports Server (NTRS)

    Song, P.; Holzer, T. E.; Russell, C. T.; Wang, Z.

    1994-01-01

    We develop a one-dimensional Low Latitude Boundary Layer (LLBL) model for northward interplanetary magnetic field (IMF). The boundary layer in this model is uniform in the direction normal to the magnetopause, a 'plateau-type' boundary layer. The boundary layer motion is decoupled from the magnetosheath motion and driven by the plasma pressure associated with the incoming solar wind plasma near local noon, which has become entrained on closed field lines as a result of reconnection in the cusp region. Dissipation in the ionosphere at the feet of the boundary layer field lines opposes this motion. There are two physical solutions for the model. In one, the boundary layer reaches a terminal velocity in the tail as the boundary layer plasma effectively joins the solar wind flow. In the other solution, the flow is nearly stopped in the far tail. In combination with other mechanisms, this latter solution may correspond to the case in which the boundary layer plasma participates in magnetospheric convection and returns sunward. The density, velocity, and thickness as functions of distance from local noon are studied, assuming that the magnetopause hasa elliptical shape and the magnetospheric field is dipolar.

  3. Latitude, elevational climatic zonation and speciation in New World vertebrates.

    PubMed

    Cadena, Carlos Daniel; Kozak, Kenneth H; Gómez, Juan Pablo; Parra, Juan Luis; McCain, Christy M; Bowie, Rauri C K; Carnaval, Ana C; Moritz, Craig; Rahbek, Carsten; Roberts, Trina E; Sanders, Nathan J; Schneider, Christopher J; VanDerWal, Jeremy; Zamudio, Kelly R; Graham, Catherine H

    2012-01-01

    Many biodiversity hotspots are located in montane regions, especially in the tropics. A possible explanation for this pattern is that the narrow thermal tolerances of tropical species and greater climatic stratification of tropical mountains create more opportunities for climate-associated parapatric or allopatric speciation in the tropics relative to the temperate zone. However, it is unclear whether a general relationship exists among latitude, climatic zonation and the ecology of speciation. Recent taxon-specific studies obtained different results regarding the role of climate in speciation in tropical versus temperate areas. Here, we quantify overlap in the climatic distributions of 93 pairs of sister species of mammals, birds, amphibians and reptiles restricted to either the New World tropics or to the Northern temperate zone. We show that elevational ranges of tropical- and temperate-zone species do not differ from one another, yet the temperature range experienced by species in the temperate zone is greater than for those in the tropics. Moreover, tropical sister species tend to exhibit greater similarity in their climatic distributions than temperate sister species. This pattern suggests that evolutionary conservatism in the thermal niches of tropical taxa, coupled with the greater thermal zonation of tropical mountains, may result in increased opportunities for allopatric isolation, speciation and the accumulation of species in tropical montane regions. Our study exemplifies the power of combining phylogenetic and spatial datasets of global climatic variation to explore evolutionary (rather than purely ecological) explanations for the high biodiversity of tropical montane regions. PMID:21632626

  4. IRAS galaxies at low galactic and high supergalactic latitudes

    SciTech Connect

    Dow, M.W.; Lu, N.Y.; Houck, J.R.; Salpeter, E.E.; Lewis, B.M.

    1988-01-01

    Based on IR colors, 371 IRAS point sources with absolute value of b = 2-16 deg (b = galactic latitude) were selected for study at H I 21 cm as potential galaxies: 25 percent (93) of these sources are galaxies with redshifts less than 8000 km/s based on H I spectra. Most of the detected galaxies are at redshifts between 2000 and 7500 km/s. Fifty-five of these lie in an area about 40 deg away from the junction of the Pisces-Perseus and Lynx-Ursa Major superclusters, and show a distribution of systemic velocities very similar to these superclusters. There is an enhanced density of galaxies near 6000 km/s with galactic longitude l about 40 deg and b about 0 deg. The two regions surveyed, centered at l about 192 deg and l about 54 deg, lie outside the plane of the Local Supercluster and do not show any preference for galaxies with low velocity widths. 16 references.

  5. IRAS galaxies at low galactic and high supergalactic latitudes

    NASA Technical Reports Server (NTRS)

    Dow, M. W.; Lu, N. Y.; Houck, J. R.; Salpeter, E. E.; Lewis, B. M.

    1988-01-01

    Based on IR colors, 371 IRAS point sources with absolute value of b = 2-16 deg (b = galactic latitude) were selected for study at H I 21 cm as potential galaxies: 25 percent (93) of these sources are galaxies with redshifts less than 8000 km/s based on H I spectra. Most of the detected galaxies are at redshifts between 2000 and 7500 km/s. Fifty-five of these lie in an area about 40 deg away from the junction of the Pisces-Perseus and Lynx-Ursa Major superclusters, and show a distribution of systemic velocities very similar to these superclusters. There is an enhanced density of galaxies near 6000 km/s with galactic longitude l about 40 deg and b about 0 deg. The two regions surveyed, centered at l about 192 deg and l about 54 deg, lie outside the plane of the Local Supercluster and do not show any preference for galaxies with low velocity widths.

  6. Sun position calculator (SPC) for Landsat imagery with geodetic latitudes

    NASA Astrophysics Data System (ADS)

    Seong, Jeong C.

    2015-12-01

    Landsat imagery comes with sun position information such as azimuth and sun elevation, but they are available only at the center of a scene. To aid in the use of Landsat imagery for various solar radiation applications such as topographic correction, solar power, urban heat island, agriculture, climate and vegetation, it is necessary to calculate the sun position information at every pixel. This research developed a PC application that creates sun position data layers in ArcGIS at every pixel in a Landsat scene. The SPC program is composed of two major routines - converting universal transverse Mercator (UTM) projection coordinates to geographic longitudes and latitudes, and calculating sun position information based on the Meeus' routine. For the latter, an innovative method was also implemented to account for the Earth's flattening on an ellipsoid. The Meeus routine implemented in this research showed about 0.2‧ of mean absolute difference from the National Renewable Energy Laboratory (NREL) Solar Position Algorithm (SPA) routine when solar zenith and azimuth angles were tested with every 30 min data at four city locations (Fairbanks, Atlanta, Sydney and Rio Grande) on June 30, 2014. The Meeus routine was about ten times faster than the SPA routine. Professionals who need the Sun's position information for Landsat imagery will benefit from the SPC application.

  7. Low Latitude Pulsations Associated with Different Phases of Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Bulusu, J.; Vankayala, R. C.; Sinha, A. K.; Vichare, G.; Thomas, N.

    2014-12-01

    During geomagnetic storm lot of free energy is available in the magnetosphere and this energy can act as feeder to electromagnetic waves in different frequency bands. A classical geomagnetic storm consists mainly of four phases i.e. SSC (Sudden Storm commencement), initial Phase, main phase and recovery phase. In this paper, we investigate the characteristics of electromagnetic waves in ULF (ultra low frequency) band associated with different phases of geomagnetic storms. Electromagnetic waves in ULF band (Period~ 10-100s) in the Earth's magnetosphere are generally termed as geomagnetic pulsations. A detailed statistical analysis has been performed over ten years of geomagnetic data from low latitude ground stations in Indian and Japanese sectors. The study reveals that storms in general, are accompanied with continuous pulsations of different frequency bands during different phases. In particular, the main phase of 91 % of intense storms was accompanied with pulsations in Pc5 band (frequency~ 2-7 mHz). However, the occurrence of these pulsations was less frequent during main phase of weak to moderate storms. Further, the amplitude of these pulsations increased with the intensity of storm.

  8. Boulder movement at high northern latitudes of Mars

    NASA Astrophysics Data System (ADS)

    Orloff, T.; Kreslavsky, M.; Asphaug, E.; Korteniemi, J.

    2011-11-01

    We examine a narrow latitudinal band (60°N-70°N) on Mars to place constraints on the seasonally averaged velocity Q of boulder movements over patterned ground. These latitudes comprise a region of the northern lowlands where patterned ground covers nearly every surface. Here boulders meters in diameter are consistently found to be concentrated at or near the cracks that define the polygonal networks, indicating a mobilization process. Because impact craters are the source for many boulders, we can use craters and their degradation to estimate the time scales for boulder movement. We study and catalog 1018 degraded impact craters (100 m < D < 1 km) in 55 High Resolution Imaging Science Experiment (HiRISE) images. We find that crater degradation occurs on a time scale <˜1 Ma, which is too recent for melting-related mechanisms in a past, warmer epoch. Clustering of boulders occurs at a time scale of a few Ma or shorter, which means that boulders on 5-20 m diameter polygons move at seasonal velocities Q ˜1-10 μm/yr or faster.

  9. Global marine bacterial diversity peaks at high latitudes in winter

    PubMed Central

    Ladau, Joshua; Sharpton, Thomas J; Finucane, Mariel M; Jospin, Guillaume; Kembel, Steven W; O'Dwyer, James; Koeppel, Alexander F; Green, Jessica L; Pollard, Katherine S

    2013-01-01

    Genomic approaches to characterizing bacterial communities are revealing significant differences in diversity and composition between environments. But bacterial distributions have not been mapped at a global scale. Although current community surveys are way too sparse to map global diversity patterns directly, there is now sufficient data to fit accurate models of how bacterial distributions vary across different environments and to make global scale maps from these models. We apply this approach to map the global distributions of bacteria in marine surface waters. Our spatially and temporally explicit predictions suggest that bacterial diversity peaks in temperate latitudes across the world's oceans. These global peaks are seasonal, occurring 6 months apart in the two hemispheres, in the boreal and austral winters. This pattern is quite different from the tropical, seasonally consistent diversity patterns observed for most macroorganisms. However, like other marine organisms, surface water bacteria are particularly diverse in regions of high human environmental impacts on the oceans. Our maps provide the first picture of bacterial distributions at a global scale and suggest important differences between the diversity patterns of bacteria compared with other organisms. PMID:23514781

  10. High-latitude circulation in giant planet magnetospheres

    NASA Astrophysics Data System (ADS)

    Southwood, D. J.; Chané, E.

    2016-06-01

    We follow-up the proposal by Cowley et al. (2004) that the plasma circulation in the magnetospheres of the giant planets is a combination of two cycles or circulation systems. The Vasyliunas cycle transports heavy material ionized deep within the magnetosphere eventually to loss in the magnetotail. The second cycle is driven by magnetic reconnection between the planetary and the solar wind magnetic fields (the Dungey cycle) and is found on flux tubes poleward of those of the Vasyliunas cycle. We examine features of the Dungey system, particularly what occurs out of the equatorial plane. The Dungey cycle requires reconnection on the dayside, and we suggest that at the giant planets the dayside reconnection occurs preferentially in the morning sector. Second, we suggest that most of the solar wind material that enters through reconnection on to open flux tubes on the dayside never gets trapped on closed field lines but makes less than one circuit of the planet and exits down tail. In its passage to the nightside, the streaming ex-solar wind material is accelerated centrifugally by the planetary rotation primarily along the field; thus, in the tail it will appear very like a planetary wind. The escaping wind will be found on the edges of the tail plasma sheet, and reports of light ion streams in the tail are likely due to this source. The paper concludes with a discussion of high-latitude circulation in the absence of reconnection between the solar wind and planetary field.

  11. The role of superthermal electrons in high latitude ionospheric outflows

    NASA Astrophysics Data System (ADS)

    Glocer, A.; Khazanov, G. V.; Liemohn, M. W.; Toth, G.; Gombosi, T. I.

    2014-12-01

    It is well accepted that the ionosphere is a critical source of plasma for the magnetosphere, providing O+, H+, and He+ which can have wide ranging consequences for the space environment system. Changing ion composition affects magnetic reconnection in the magnetosphere, the ring current, and the wave environment which is important for high energy radiation belt electrons. Of the myriad of mechanisms that are important in determining the ionospheric outflow solution at high latitudes, we focus on the role of superthermal electron populations. It has been demonstrated in multiple studies that even small concentrations of superthermal electrons can have a dramatic effect on the outflow solution. In this presentation, we present simulation results using our Polar Wind Outflow Model (PWOM) and our SuperThermal Electron Transport (STET) code. We describe recent results on superthermal electrons role in defining the quiet time solar wind solution with comparisons to observations. We also discuss preliminary results that combine the PWOM and STET codes for a more comprehensive treatment of the impact of superthermal electrons.

  12. Habitable periglacial landscapes in martian mid-latitudes

    NASA Astrophysics Data System (ADS)

    Ulrich, M.; Wagner, D.; Hauber, E.; de Vera, J.-P.; Schirrmeister, L.

    2012-05-01

    Subsurface permafrost environments on Mars are considered to be zones where extant life could have survived. For the identification of possible habitats it is important to understand periglacial landscape evolution and related subsurface and environmental conditions. Many landforms that are interpreted to be related to ground ice are located in the martian mid-latitudinal belts. This paper summarizes the insights gained from studies of terrestrial analogs to permafrost landforms on Mars. The potential habitability of martian mid-latitude periglacial landscapes is exemplarily deduced for one such landscape, that of Utopia Planitia, by a review and discussion of environmental conditions influencing periglacial landscape evolution. Based on recent calculations of the astronomical forcing of climate changes, specific climate periods are identified within the last 10 Ma when thaw processes and liquid water were probably important for the development of permafrost geomorphology. No periods could be identified within the last 4 Ma which met the suggested threshold criteria for liquid water and habitable conditions. Implications of past and present environmental conditions such as temperature variations, ground-ice conditions, and liquid water activity are discussed with respect to the potential survival of highly-specialized microorganisms known from terrestrial permafrost. We conclude that possible habitable subsurface niches might have been developed in close relation to specific permafrost landform morphology on Mars. These would have probably been dominated by lithoautotrophic microorganisms (i.e. methanogenic archaea).

  13. Coordinated observations of high-latitude ionospheric turbulence

    SciTech Connect

    Basu, S.; Basu, S.; Valladares, C.E.; Weber, E.J.; Buchau, J.

    1988-01-01

    A coordinated data set comprised of scintillation, ionosonde, incoherent scatter radar and optical measurements obtained on two nights during the CEDAR/WITS campaign of February, 1988 was selected for the study of two distinct classes of high latitude plasma turbulence. Under IMP Bz northward conditions, the polar cap arc detected by the all-sky imaging photometer (ASIP) in this phase of low solar activity (SSN=40) was found to be associated with a total electron content enhancement of only 2x10 to the 16th power/sq. m and weak amplitude scintillations (S sub 4 about = 0.35) at 250 MHz. The photometer and scintillation measurements indicated that in addition to the dawn to dusk motion of 200/ms in the inertial frame, there existed enhanced plasma motion of about 400/ms along the arc. The second data set conforming to IMF Bz southward condition showed the existence of ionization patches in the polar cap and their anti-sunward motion towards the auroral oval. The polar cap patches detected deep within the polar cap with electron contents as large as 10x10 to the 16th power/sq. m caused 15 dB scintillations at 250 MHz. These patches detected close to the auroral oval also caused strong scintillations which indicated that the patches get continually structured during their convection through the winter polar cap.

  14. Inner Plasma Structure of the Low-Latitude Reconnection Layer

    NASA Technical Reports Server (NTRS)

    Zhang, Q.-H.; Dunlop, M. W.; Lockwood, M.; Lavraud, B.; Bogdanova, Y. V.; Hasegawa, H.; Yang, H. -G.; Liu, R. -Y.; Hu, H. -Q.; Zhang, B. -C.; Pu, Z. -Y.; Yang, Z. -W.; Wang, J.; Taylor, M. G. G. T.; Berchem, J.; Constantinescu, D.; Volwerk, M.; Frey, H.; Fazakerley, A. N.; Shen, C.; Shi, J. -K.; Sibeck, D.; Escoubet, P.; Wild, J. A.

    2012-01-01

    We report a clear transition through a reconnection layer at the low-latitude magnetopause which shows a complete traversal across all reconnected field lines during northwestward interplanetary magnetic field (IMF) conditions. The associated plasma populations confirm details of the electron and ion mixing and the time history and acceleration through the current layer. This case has low magnetic shear with a strong guide field and the reconnection layer contains a single density depletion layer on the magnetosheath side which we suggest results from nearly field-aligned magnetosheath flows. Within the reconnection boundary layer, there are two plasma boundaries, close to the inferred separatrices on the magnetosphere and magnetosheath sides (Ssp and Ssh) and two boundaries associated with the Alfvén waves (or Rotational Discontinuities, RDsp and RDsh). The data are consistent with these being launched from the reconnection site and the plasma distributions are well ordered and suggestive of the time elapsed since reconnection of the field lines observed. In each sub-layer between the boundaries the plasma distribution is different and is centered around the current sheet, responsible for magnetosheath acceleration. We show evidence for a velocity dispersion effect in the electron anisotropy that is consistent with the time elapsed since reconnection. In addition, new evidence is presented for the occurrence of partial reflection of magnetosheath electrons at the magnetopause current layer.

  15. Environmental conditions for alternative tree cover states in high latitudes

    NASA Astrophysics Data System (ADS)

    Abis, Beniamino; Brovkin, Victor

    2016-04-01

    Previous analysis of the vegetation cover from remote sensing revealed the existence of three alternative modes in the frequency distribution of boreal tree cover: a sparsely vegetated treeless state, a savanna-like state, and a forest state. Identifying which are the regions subject to multimodality, and assessing which are the main factors underlying their existence, is important to project future change of natural vegetation cover and its effect on climate. We study the impact on the forest cover fraction distribution of seven globally-observed environmental factors: mean annual rainfall, mean minimum temperature, growing degree days above 0, permafrost distribution, soil moisture, wildfire occurrence frequency, and thawing depth. Through the use of generalised additive models, regression trees, and conditional histograms, we find that the main factors determining the forest distribution in high latitudes are: permafrost distribution, mean annual rainfall, mean minimum temperature, soil moisture, and wildfire frequency. Additionally, we find differences between regions within the boreal area, such as Eurasia, Eastern North America, and Western North America. Furthermore, using a classification based on these factors, we show the existence and location of alternative tree cover states under the same climate conditions in the boreal region. These are areas of potential interest for a more detailed analysis of land-atmosphere interactions.

  16. Comparing ionospheric models with mid-latitude ionosonde observations

    NASA Astrophysics Data System (ADS)

    Al-Ubaidi, Najat M. R.

    2009-06-01

    The purpose of this research work is to validate the ionospheric models (IRI and CHIU) to assess its suitability and usefulness as an operational tool. The ionospheric model is a computer model designed to predict the state of the global ionosphere for 24 h. The scope was limited to conduct comparisons between the predicted F2 layer critical frequencies (f0F2) against observed ionosonde data. The ionospheric prediction model (IPM) was designed to predict by using monthly median sunspot number, while the observation data are taken from two digital ionospheric sounding stations (Okinawa, 26.28N, 127.8E and Wakkanai, 45.38N, 141.66E) which lies within the mid-latitude region of the globe. Analysis of the f0F2 data from stations for year (2001) with high solar activity and year (2004) with low solar activity, four months (March, June, September and December) chosen based primarily on data availability. From results it seen that the ratio between monthly median predicted and observed f0F2 values for each model used in this research work and for the chosen months was nonlinear with local time, so the empirical formula for applying correction factors were determined, these formula can be used to correct the error occurred in predicted f0F2 value.

  17. Low-latitude Ionospheric Heating during Solar Flares

    NASA Astrophysics Data System (ADS)

    Klenzing, J.; Chamberlin, P. C.; Qian, L.; Haaser, R. A.; Burrell, A. G.; Earle, G. D.; Heelis, R. A.; Simoes, F. A.

    2013-12-01

    The advent of the Solar Dynamics Observatory (SDO) represents a leap forward in our capability to measure rapidly changing transient events on the sun. SDO measurements are paired with the comprehensive low latitude measurements of the ionosphere and thermosphere provided by the Communication/Navigation Outage Forecast System (C/NOFS) satellite and state-of-the-art general circulation models to discuss the coupling between the terrestrial upper atmosphere and solar radiation. Here we discuss ionospheric heating as detected by the Coupled Ion-Neutral Dynamics Investigation (CINDI) instrument suite on the C/NOFS satellite during solar flares. Also discusses is the necessity of decoupling the heating due to increased EUV irradiance and that due to geomagnetic storms, which sometimes occur with flares. Increases in both the ion temperature and ion density in the subsolar topside ionosphere are detected within 77 minutes of the 23 Jan 2012 M-class flare, and the observed results are compared with the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) using the Flare Irradiance Spectral Model (FISM) as an input.

  18. The CH fraction of carbon stars at high Galactic latitudes

    NASA Astrophysics Data System (ADS)

    Goswami, Aruna; Karinkuzhi, Drisya; Shantikumar, N. S.

    2010-02-01

    CH stars form a distinct class of objects with characteristic properties like iron deficiency, enrichment of carbon and overabundance of heavy elements. These properties can provide strong observational constraints for the theoretical computation of nucleosynthesis at low metallicity. An important issue is the relative surface density of CH stars, which can provide valuable input to our understanding of the role of low- to intermediate-mass stars in early Galactic chemical evolution. Spectroscopic characterization provides an effective way of identifying CH stars. The present analysis aims at a quantitative assessment of the fraction of CH stars in a sample using a set of spectral classification criteria. The sample consists of 92 objects selected from a collection of candidate faint high-latitude carbon stars from the Hamburg/ESO survey. Medium-resolution (λ/δλ ~ 1300) spectra for these objects were obtained using the Optomechanics Research (OMR) spectrograph at the Vainu Bappu Observatory (VBO), Kavalur and the Himalaya Faint Object Spectrograph (HFOSC) at the Himalayan Chandra Telescope (HCT), Indian Astronomical Observatory, Hanle, during 2007-2009, spanning a wavelength range 3800-6800Å. Spectral analysis shows 36 of the 92 objects to be potential CH stars; combined with our earlier studies this implies ~37 per cent (of 243 objects) as the CH fraction. We present spectral descriptions of the newly identified CH star candidates. Estimated effective temperatures, 12C/13C isotopic ratios and their locations on the two-colour J - H versus H - K plot are used to support their identification.

  19. Paleoclimatic significance of high-latitude loess deposits

    SciTech Connect

    Beget, J.E.

    1992-03-01

    Loess deposits reflect changing environmental conditions in terrestrial regions, and contain long paleoclimatic records analogous to those found in marine sediments, lacustrine sediments, and ice sheets. Alaskan loess was deposited at rates of ca. 0.05-0.5 mm yr-l during the last 2-3 x 106 years; loess deposits contain some of the longest and most complete proxy climate records yet found. New analytical methods are used to reconstruct changes in climate and atmospheric regime including wind intensity, storminess, temperature, and precipitation. Loess also contains a history of permafrost and paleosol formation, volcanic eruptions, and paleoecologic changes in high latitude regions, as well as Quaternary fossils and early man sites and artifacts. Time-series analysis of proxy climate data from loess supports the astronomic model of climate change, although some transient climate events recorded in loess records are too short to be explained by orbital insolation forcing, and may instead correlate with rapid, short-term changes in atmospheric C02 and CH4 content.

  20. GPS derived ionospheric TEC response to geomagnetic storm on 24 August 2005 at Indian low latitude stations

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjay; Singh, A. K.

    2011-02-01

    Results pertaining to the response of the low latitude ionosphere to a major geomagnetic storm that occurred on 24 August 2005 are presented. The dual frequency GPS data have been analyzed to retrieve vertical total electron content at two Indian low latitude stations (IGS stations) Hyderabad (Geographic latitude 17°20‧N, Geographic longitude 78°30‧E, Geomagnetic latitude 8.65°N) and Bangalore (Geographic latitude 12°58‧N, Geographic longitude 77°33‧E, Geomagnetic latitude 4.58°N). These results show variation of GPS derived total electron content (TEC) due to geomagnetic storm effect, local low latitude electrodynamics response to penetration of high latitude convection electric field and effect of modified fountain effect on GPS-TEC in low latitude zone.

  1. "Michael Jackson World Tour:" Maps and Globes--Latitude and Longitude.

    ERIC Educational Resources Information Center

    Benscoter, Gloria Dee

    1988-01-01

    Presents a mapping activity which helps students understand the purpose of latitude and longitude lines. Gives students an opportunity to use longitude and latitude in a meaningful way by asking them to plan a world concert tour for a rock star. Includes a reproducible activity page. (LS)

  2. Decision latitude and workload demand: implications for full and partial absenteeism.

    PubMed

    Zavala, Silvana K; French, Michael T; Zarkin, Gary A; Omachonu, Vincent K

    2002-01-01

    This research examined the relative importance of two components of job stress--decision latitude and workload demand--on employee absenteeism. The analysis was based on confidential self-reported data from employees at two worksites, which were collected in three independent cross-sections beginning in 1995. The negative binomial technique was used to estimate the effects of decision latitude and workload demand on employee attendance, while controlling for employee demographics and other workplace characteristics. Estimation results show that high decision latitude was negatively and significantly related to number of full days absent from work (full absenteeism) and number of days arriving late to work or leaving work early (partial absenteeism). Conversely, the coefficient estimates for low decision latitude were positive in every model and significantly related to partial absenteeism. Low workload demand was negatively and significantly related to partial absenteeism, but not full days absent. The interaction effects of decision latitude and workload demand on absenteeism were not statistically significant. Several recent studies have estimated a significant relationship between decision latitude, workload demand, and medical problems such as cardiovascular disease. The current findings suggest that decision latitude and workload demand are also related to workplace attendance. Employers and occupational hygienists should consider decision latitude and workload demand as a means to improve workplace productivity and employee health. PMID:12325290

  3. Latitude-Dependence of Median Grain Size in the Lunar Regolith

    NASA Astrophysics Data System (ADS)

    Jeong, M.; Kim, S. S.; Garrick-Bethell, I.; Park, S. M.; Sim, C. K.; Jin, H.; Min, K. W.

    2015-11-01

    We conducted polarimetric observations of the Moon and constructed a grain size map of the lunar regolith. The grain size is found to be larger at higher latitude. This is thought to be a result of reduced space weathering effects at high latitudes.

  4. Comments on slow latitude variations and secular motion of the Earth's pole.

    NASA Astrophysics Data System (ADS)

    Korsun', A. A.; Yatskiv, Ya. S.

    Re-reduced latitude and time observations based on the HIPPARCOS frame were analysed in connection with the problem of existence of secular polar motion. It is shown that there are large non-polar variations of mean latitudes and longitudes which could hamper the determination of secular polar motion.

  5. Environmental variation, vegetation distribution, carbon dynamics and water/energy exchange at high latitudes

    USGS Publications Warehouse

    McGuire, A.D.; Wirth, C.; Apps, M.; Beringer, J.; Clein, J.; Epstein, H.; Kicklighter, D.W.; Bhatti, J.; Chapin, F. S., III; De Groot, B.; Efremov, D.; Eugster, W.; Fukuda, M.; Gower, T.; Hinzman, L.; Huntley, B.; Jia, G.J.; Kasischke, E.; Melillo, J.; Romanovsky, V.; Shvidenko, A.; Vaganov, E.; Walker, D.

    2002-01-01

    The responses of high latitude ecosystems to global change involve complex interactions among environmental variables, vegetation distribution, carbon dynamics, and water and energy exchange. These responses may have important consequences for the earth system. In this study, we evaluated how vegetation distribution, carbon stocks and turnover, and water and energy exchange are related to environmental variation spanned by the network of the IGBP high latitude transects. While the most notable feature of the high latitude transects is that they generally span temperature gradients from southern to northern latitudes, there are substantial differences in temperature among the transects. Also, along each transect temperature co-varies with precipitation and photosynthetically active radiation, which are also variable among the transects. Both climate and disturbance interact to influence latitudinal patterns of vegetation and soil carbon storage among the transects, and vegetation distribution appears to interact with climate to determine exchanges of heat and moisture in high latitudes. Despite limitations imposed by the data we assembled, the analyses in this study have taken an important step toward clarifying the complexity of interactions among environmental variables, vegetation distribution, carbon stocks and turnover, and water and energy exchange in high latitude regions. This study reveals the need to conduct coordinated global change studies in high latitudes to further elucidate how interactions among climate, disturbance, and vegetation distribution influence carbon dynamics and water and energy exchange in high latitudes.

  6. Occurrence climatology of the electron density irregularities in the mid-latitude E region

    NASA Astrophysics Data System (ADS)

    Kwak, Y.; Yang, T.; Kil, H.

    2013-12-01

    Electron density irregularities in the ionosphere interrupt the propagation of electromagnetic waves and are problematic for navigation and communication systems. For this practical importance, significant efforts have been made to establish information on the occurrence climatology of such irregularities, to understand the onset conditions of such irregularities, and to predict or avoid the impact of these irregularities on the society. While the irregularities occur in all latitudes, less attention has been paid to the irregularities in middle latitudes. This may be because the irregularities in middle latitudes are not as severe as those in other latitude regions. However, middle latitudes are also the place where various forms of irregularities occur. A 40.8 MHz VHF radar was built at Daejeon (36.18°N, 127.14°E, 26.7°N dip latitude) in South Korea aiming at continuous monitoring of the behavior of the middle-latitude electron density irregularities in the Far East Asian sector. The radar has been continuously operated by the Korea Astronomy and Space Science Institute (KASI) since December 2009. Using the Daejeon VHF radar data acquired since December 2009, we examine the occurrence types of the irregularities and the dependence of the irregularities on geophysical conditions (local time, altitude, season, solar cycle, and magnetic activity). These results can be used as a tool for investigating the onset conditions of the middle-latitude irregularities.

  7. Energetic particles and coronal mass ejections in the high latitude heliosphere: Ulysses-LET observations

    SciTech Connect

    Bothmer, V.; Marsden, R. G.; Sanderson, T. R.; Trattner, K. J.; Wenzel, K.-P.; Balogh, A.; Forsyth, R. J.; Goldstein, B. E.; Uchida, Y.; Hudson, H. S.

    1996-07-20

    We have investigated energetic ions of non-corotating nature in the high latitude heliosphere. Major particle events were observed by Ulysses up to latitudes of 60 deg. S. All were associated with passage of coronal mass ejections (CMEs) over the spacecraft. The relationship of these events with solar activity was investigated using Yohkoh soft X-ray images.

  8. Coronal mass ejections in the solar wind at high solar latitudes: An overview

    NASA Technical Reports Server (NTRS)

    Gosling, Jack T.

    1994-01-01

    Ulysses provided the first direct measurements of coronal mass ejections (CME's) in the solar wind at high heliographic latitudes. An overview of new results from the plasma experiment on Ulysses and magnetic field measurements, during the spacecraft's first excursion to high solar latitudes are summarized. A striking aspect of the high-latitude CME's observed is that they all had high speeds, with the overall average speed being 730 km/sec. A new class of forward-reverse shock pairs, associated with expansion of CME's was discovered at high latitudes. Of six certain CME's observed at high latitudes, three have associated shock pairs of this nature. Combined Ulysses and Yohkoh observations suggest that the flux rope topology characteristic of some CME's results from reconnection within the legs of neighboring magnetic loops embedded within the escaping CME's.

  9. Spörer's law and relationship between the latitude and amplitude parameters of solar activity

    NASA Astrophysics Data System (ADS)

    Ivanov, V. G.; Miletsky, E. V.

    2014-12-01

    The equatorward drift of average sunspot latitudes (Spörer's law) and its relationship with other characteristics of the 11-year solar cycle are analyzed. The notion of cycle latitude phase (CLP) is introduced, which is calculated from behavior of average sunspot latitudes. The latter are shown to be expressed, with known accuracy, as a universal monotonic decreasing function of the CLP and to be independent of the cycle strength. The same applies to the latitudinal drift velocity of the sunspot generating zone. The shifts in the CLP reference times relative to the cycle minima are, on the contrary, well correlated with the amplitudes of the corresponding cycles. Solar activity in the declining phase of the solar cycle is found to be tightly related to the average sunspot latitude and CLP. The relationships found in the study can be used to reconstruct average sunspot latitudes in the pre-Greenwich epoch based on the available information on cycle amplitudes.

  10. Latitude-dependent sensitivity to stationary perturbations in simple climate models

    NASA Technical Reports Server (NTRS)

    Salmun, H.; Cahalan, R. F.; North, G. R.

    1980-01-01

    The steady-state zonally averaged climate is perturbed by adding a latitude-dependent heat source to an energy balance equation of the simplified Budyko-Sellers type. The latitude of the ice edge, which is attached to an isotherm, becomes dependent on the strength of the perturbation. This dependence is given in terms of the well-known iceline-solar constant relation, and the latitude dependence of the perturbed temperature field is then uniquely determined. The exact analytical solution is linearized and expressed in terms of a superposition of line sources at various latitudes. The main features are: (1) The total temperature response is a sum of the direct effect of the perturbation and an indirect ice-albedo effect proportional to the solar ice-edge sensitivity; and (2) the indirect feedback effect produces an enhanced response in polar latitudes.

  11. Coronal mass ejections in the solar wind at high solar latitudes: An overview

    SciTech Connect

    Gosling, J.T.

    1994-10-01

    Ulysses has provided the first direct measurements of coronal mass ejections, CMES, in the solar wind at high heliographic latitudes. This paper provides an overview of new and unexpected results from the plasma experiment on Ulysses, supplemented with magnetic field measurements, during the spacecraft`s first excursion to high solar latitudes. A striking aspect of the high-latitude CMEs observed is that they all had high speeds, with the overall average speed being 730 km s{sup {minus}1}. A new class of forward-reverse shock pairs, associated with expansion of CMES, has been discovered at high latitudes. Of six certain CMEs observed at high latitudes, three have associated shock pairs of this nature. Combined Ulysses and Yohkoh observations suggest that the flux rope topology characteristic of some CMEs results from reconnection within the legs of neighboring magnetic loops embedded within the escaping CMES.

  12. On the latitude dependence of drift velocity of the geomagnetic main field and its secular variation

    NASA Astrophysics Data System (ADS)

    Yukutake, Takesi; Shimizu, Hisayoshi

    2016-08-01

    There is an apparent difference in the westward drift between the geomagnetic main field and its time derivative, secular variation. The drift velocity of the main field is about 0.2°/year, definitely lower than that of the secular variation, 0.3°/year. The drift velocity of the main field appears to change with latitude, being low at high latitudes and higher at low latitudes, whereas the velocity of the secular variation is nearly constant irrespective of latitude. This paper examines what causes this difference by adopting the drifting and standing field model that assumes the geomagnetic field consists of the field steadily drifting westwards and the field remaining at nearly the same location. In this study, we confirm that the existence of the non-drifting standing field significantly affects the estimate of the drift velocity of the total field (i.e., the main field), and makes it slower than that of the secular variation. The drifting field is intense in low latitudes with its maximum at the equator, while the standing field dominates in higher latitudes. As a consequence, reduction of the apparent drifting velocity of the total field by the standing field is conspicuous in higher latitudes and less so in low latitudes. This creates the observed latitudinal structure of the drift velocity of the main field. On the other hand, the drift velocity of the secular variation is less affected by existence of the standing field, and mostly reflects the velocity of the drifting field that is almost constant with latitude. The velocity of the secular variation thus becomes almost uniform independent of latitude. The observed difference between the main field and the secular variation is naturally derived from the drifting and standing field model. This implies that physical mechanisms to generate the drifting and standing fields can be considered independently.

  13. Polarization analysis of Pc 1 geomagnetic pulsations at multi-point ground observations at middle latitudes

    NASA Astrophysics Data System (ADS)

    Nomura, R.; Shiokawa, K.; Shevtsov, B. M.

    2008-12-01

    Pc 1 geomagnetic pulsations propagate from the high-latitude source region to middle latitudes in the ionosphere. The high-latitude source region links to the magnetosphere where ion cyclotron instability occurs around the plasmapause. Since Pc 1 pulsation observed by ground magnetometers at middle latitudes can be a mixture of waves from several high-latitude source regions, the polarization analysis of Pc 1 pulsations enables us to understand the spatial structure and time variations of the high-latitude source region. In order to investigate spectral and propagation characteristics of the Pc 1 at mid-latitudes, we have installed three induction magnetometers at Paratunka (PTK, 53.0N, 158.2E, magnetic latitude (MLAT): 45.8N), Moshiri (MSR, 44.4N, 142.3E, MLAT: 35.7N) and Sata (STA, 31.0N, 130.7E, MLAT: 22.0N). The observations with a 64-Hz sample recording have been started on July 5, 2007, at MSR, on August 21, 2007, at PTK, and on September 5, 2007, at STA and will be started at Magadan (MGD, 59.7N, 151.0E, MLAT: 50.6N) on November 2008. Polarization analysis with these multi-point data indicates that the Pc 1 polarization directions on November 11, 2007 depend on frequency with a difference of ~30 degree. For December 17, 2007 event, the polarization angle varies in time for ~30 deg/hour. These facts may indicate either the structure and motion of the high-latitude Pc 1 source region or the effects of the duct propagations in the inhomogeneous ionosphere. In this presentation, we also show the statistical results of these polarization analyses using 1-year data of middle latitude Pc 1 observations.

  14. Hydrated Sulfates in the Southern High Latitudes of Mars

    NASA Astrophysics Data System (ADS)

    Ackiss, S. E.; Wray, J. J.

    2012-12-01

    Sulfates on Mars appear largely concentrated in sedimentary rocks dating to the Late Noachian or Hesperian [e.g., 1], but they are also abundant in Amazonian sand dunes around the north polar cap [2]. The gypsum in those dunes derives from the polar layered deposits [e.g., 3], where it may form when sunlight causes minor melting and weathering of embedded dust. We are investigating whether such processes might have also contributed to sulfate formation elsewhere, specifically in regions surrounding the south polar terrain. Our study regions to date include the Sisyphi Montes (20W-40E and 55-75S) and other mountainous areas near the Thyles Rupes (110-140E and 55-75S), the Ulyxis Rupes (150-180E and 55-70S), and Chamberlin Crater (110-150W and 55-75S). We searched for sulfates using the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). TRR3 images were evaluated using standard CRISM procedures, including the "volcano scan" atmospheric correction. We used spectral parameters to identify regions of interest, from which we extracted spectra, which we divided by spectrally neutral regions in the same scene to remove systematic artifacts. The resulting ratio spectra were visually compared to library spectra to identify possible hydrated mineral constituents. Some sulfates in the southern high latitudes appear localized to mountains of the Sisyphi Montes, which have been interpreted as volcanoes that erupted under a Hesperian ice sheet [4]. These sulfates might have formed via volcanic hydrothermal or acid fog alteration. We found that nearly 50% of the images on putative volcanoes in the Sisyphi Montes show a 1.9 μm absorption consistent with hydration. The percentage for images on the plains between volcanoes is actually higher; i.e., hydration is not unique to the volcanoes. Nevertheless, the three locations at which we found the strongest absorptions are all on volcanoes. In the Thyles Rupes region, 25% of the images on putative volcanoes are hydrated with

  15. Exposed Ice in the Northern Mid-Latitudes of Mars

    NASA Astrophysics Data System (ADS)

    Allen, C. C.

    2007-12-01

    Ice-Rich Layer: Polygonal features with dimensions of approximately 100 meters, bounded by cracks, are commonly observed on the martian northern plains. These features are generally attributed to thermal cracking of ice-rich sediments, in direct analogy to polygons in terrestrial polar regions [1,2]. We mapped polygons in the northern mid-latitudes (30 to 65 N) using MOC and HiRISE images [3]. Polygons are scattered across the northern plains, with a particular concentration in western Utopia Planitia. This region largely overlaps the Late Amazonian Astapus Colles unit, characterized by polygonal terrain and nested pits consistent with periglacial and thermokarst origins [4]. Bright and Dark Polygonal Cracks: An examination of all MOC images (1997 through 2003) covering the study area demonstrated that, at latitudes of 55 to 65 N, most of the imaged polygons show bright bounding cracks. We interpret these bright cracks as exposed ice. Between 40 and 55 N, most of the imaged polygons show dark bounding cracks [5]. These are interpreted as polygons from which the exposed ice has been removed by sublimation. The long-term stability limit for exposed ice, even in deep cracks, apparently lies near 55 N. Bright and Dark Spots: Many HiRISE and MOC frames showing polygons in the northern plains also show small numbers of bright and dark spots, particularly in western Utopia Planitia. Many of the spots are closely associated with collapse features suggestive of thermokarst. The spots range from tens to approximately 100 meters in diameter. The bright spots are interpreted as exposed ice, due to their prevalence on terrain mapped as ice rich. The dark spots are interpreted as former bright spots, which have darkened as the exposed ice is lost by sublimation. The bright spots may be the martian equivalents of pingos, ice-cored mounds found in periglacial regions on Earth [6,7,8,9, 10]. Terrestrial pingos from which the ice core has melted often collapse to form depressions

  16. Low-latitude Coronal Holes during Solar Maximum

    NASA Astrophysics Data System (ADS)

    Miralles, M.; Cranmer, S.; Kohl, J.

    Analyses of in situ observations have shown that some small coronal holes are sources of slow solar wind near solar maximum when polar coronal holes become smaller and disappear. However, not all coronal holes at solar maximum produce slow wind. The Ultraviolet Coronagraph Spectrometer (UVCS) aboard SOHO has been used to observe large low-latitude coronal holes during solar maximum that produced fast solar wind. UVCS observations show that large equatorial holes at solar maximum have plasma properties that seem to bridge the gap between solar minimum polar coronal holes and streamers. The ion kinetic temperatures in equatorial holes are about 2 times larger than those in a solar minimum equatorial streamer, and about a factor of 2 smaller than those in polar coronal holes above 2 R . The outflow speeds for the large equatorial holes observed by UVCS are only about 100 km s-1 , a factor of 4 smaller than those in polar holes, at 3 R . However, in situ data corresponding to these equatorial coronal holes showed asymptotic wind speeds of 600-700 km s-1 . These wind speeds are similar to those observed over polar coronal holes at solar minimum. In contrast to the polar coronal holes, the bulk of the solar wind acceleration in large equatorial coronal holes at solar maximum must occur above 3 R . Thus, the combination of spectroscopic measurements in the extended corona, where the primary solar wind acceleration occurs, and in situ measurements made in the solar wind can be used to obtain the solar wind acceleration as a function of heliocentric distance. These observations provide detailed empirical constraints for theoretical models and may be key to understanding how the various types of solar wind plasma are heated and accelerated. This work is supported by NASA under Grant NAG5-11420 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency and by PRODEX (Swiss contribution).

  17. On the Frozen Soil Scheme for High Latitude Regions

    NASA Astrophysics Data System (ADS)

    Ganji, A.; Sushama, L.

    2014-12-01

    Regional and global climate model simulated streamflows for high-latitude regions show systematic biases, particularly in the timing and magnitude of spring peak flows. Though these biases could be related to the snow water equivalent and spring temperature biases in models, a good part of these biases is due to the unaccounted effects of non-uniform infiltration capacity of the frozen ground and other related processes. In this paper, the frozen scheme in the Canadian Land Surface Scheme (CLASS), which is used in the Canadian regional and global climate models, is modified to include fractional permeable area, supercooled liquid water and a new formulation for hydraulic conductivity. Interflow is also included in these experiments presented in this study to better explain the steamflows after snow melt season. The impact of these modifications on the regional hydrology, particularly streamflow, is assessed by comparing three simulations, performed with the original and two modified versions of CLASS, driven by atmospheric forcing data from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data (ERA-Interim), for the 1990-2001 period, over a northeast Canadian domain. The two modified versions of CLASS differ in the soil hydraulic conductivity and matric potential formulations, with one version being based on formulations from a previous study and the other one is newly proposed. Results suggest statistically significant decreases in infiltration for the simulation with the new hydraulic conductivity and matric potential formulations and fractional permeable area concept, compared to the original version of CLASS, which is also reflected in the increased spring surface runoff and streamflows in this simulation with modified CLASS, over most of the study domain. The simulated spring peaks and their timing in this simulation is also in better agreement to those observed.

  18. Sponge bioerosion accelerated by ocean acidification across species and latitudes?

    NASA Astrophysics Data System (ADS)

    Wisshak, M.; Schönberg, C. H. L.; Form, A.; Freiwald, A.

    2014-06-01

    In many marine biogeographic realms, bioeroding sponges dominate the internal bioerosion of calcareous substrates such as mollusc beds and coral reef framework. They biochemically dissolve part of the carbonate and liberate so-called sponge chips, a process that is expected to be facilitated and accelerated in a more acidic environment inherent to the present global change. The bioerosion capacity of the demosponge Cliona celata Grant, 1826 in subfossil oyster shells was assessed via alkalinity anomaly technique based on 4 days of experimental exposure to three different levels of carbon dioxide partial pressure ( pCO2) at ambient temperature in the cold-temperate waters of Helgoland Island, North Sea. The rate of chemical bioerosion at present-day pCO2 was quantified with 0.08-0.1 kg m-2 year-1. Chemical bioerosion was positively correlated with increasing pCO2, with rates more than doubling at carbon dioxide levels predicted for the end of the twenty-first century, clearly confirming that C. celata bioerosion can be expected to be enhanced with progressing ocean acidification (OA). Together with previously published experimental evidence, the present results suggest that OA accelerates sponge bioerosion (1) across latitudes and biogeographic areas, (2) independent of sponge growth form, and (3) for species with or without photosymbionts alike. A general increase in sponge bioerosion with advancing OA can be expected to have a significant impact on global carbonate (re)cycling and may result in widespread negative effects, e.g. on the stability of wild and farmed shellfish populations, as well as calcareous framework builders in tropical and cold-water coral reef ecosystems.

  19. Controlling high-latitude Southern Ocean convection in climate models

    NASA Astrophysics Data System (ADS)

    Stössel, Achim; Notz, Dirk; Haumann, F. Alexander; Haak, Helmuth; Jungclaus, Johann; Mikolajewicz, Uwe

    2015-02-01

    Earth System Models (ESMs) generally suffer from a poor simulation of the High-Latitude Southern Ocean (HLSO). Here we aim at a better understanding of the shortcomings by investigating the sensitivity of the HLSO to the external freshwater flux and the horizontal resolution in forced and coupled simulations with the Max-Planck-Institute Ocean Model (MPIOM). Forced experiments reveal an immediate reduction of open-ocean convection with additional freshwater input. The latter leads to a remarkably realistic simulation of the distinct water-mass structure in the central Weddell Sea featuring a temperature maximum of +0.5 °C at 250 m depth. Similar, but more modest improvements occur over a time span of 40 years after switching from a forced to a coupled simulation with an eddy-resolving version of MPIOM. The switch is accompanied with pronounced changes of the external freshwater flux and the wind field, as well as a more realistic heat flux due to coupling. Similar to the forced freshwater-flux experiments, a heat reservoir develops at depth, which in turn decreases the vertically integrated density of the HLSO and reduces the Antarctic Circumpolar Current to rather realistic values. Coupling with a higher resolution version of the atmosphere model (ECHAM6) yields distinct improvements of the HLSO water-mass structure and sea-ice cover. While the coupled simulations reveal a realistic amount of Antarctic runoff, its distribution appears too concentrated along the coast. Spreading the runoff over a wider region, as suggested in earlier studies to mimic the effect of freshwater transport through icebergs, also leads to noticeable improvements of the HLSO water-mass properties, predominantly along the coast. This suggests that the spread of the runoff improves the representation of Antarctic Bottom Water formation through enhanced near-boundary convection rather than weakened open-ocean convection.

  20. Classical astrometry longitude and latitude determination by using CCD technique

    NASA Astrophysics Data System (ADS)

    Damljanović, G.; de Biasi, M. S.; Gerstbach, G.

    At the AOB, it is the zenith-telescope (D=11 cm, F=128.7 cm, denoted by BLZ in the list of Bureau International de l'Heure - BIH), and at Punta Indio (near La Plata) it is the photographic zenith tube (D=20 cm, F=457.7 cm, denoted by PIP in the list of BIH). At the AOB there is a CCD camera ST-8 of Santa Barbara Instrument Group (SBIG) with 1530×1020 number of pixels, 9×9 microns pixel size and 13.8×9.2 mm array dimension. We did some investigations about the possibilities for longitude (λ) and latitude (φ) determinations by using ST-8 with BLZ and PIP, and our predicted level of accuracy is few 0."01 from one CCD zenith stars processing with Tycho-2 Catalogue. Also, astro-geodesy has got new practicability with the CCDs (to reach a good accuracy of geoid determination via astro-geodesy λ and φ observations). At the TU Wien there is the CCD MX916 of Starlight Xpress (with 752×580 pixels, 11×12 microns, 8.7×6.5 mm active area). Our predicted level of accuracy for λ and φ measurements is few 0."1 from one CCD MX916 processing of zenith stars, with small optic (20 cm focus length because of not stable, but mobile instrument) and Tycho-2. A transportable zenith camera with CCD is under development at the TU Wien for astro-geodesy subjects.

  1. HIGH ECLIPTIC LATITUDE SURVEY FOR SMALL MAIN-BELT ASTEROIDS

    SciTech Connect

    Terai, Tsuyoshi; Takahashi, Jun; Itoh, Yoichi

    2013-11-01

    Main-belt asteroids have been continuously colliding with one another since they were formed. Their size distribution is primarily determined by the size dependence of asteroid strength against catastrophic impacts. The strength scaling law as a function of body size could depend on collision velocity, but the relationship remains unknown, especially under hypervelocity collisions comparable to 10 km s{sup –1}. We present a wide-field imaging survey at an ecliptic latitude of about 25° for investigating the size distribution of small main-belt asteroids that have highly inclined orbits. The analysis technique allowing for efficient asteroid detections and high-accuracy photometric measurements provides sufficient sample data to estimate the size distribution of sub-kilometer asteroids with inclinations larger than 14°. The best-fit power-law slopes of the cumulative size distribution are 1.25 ± 0.03 in the diameter range of 0.6-1.0 km and 1.84 ± 0.27 in 1.0-3.0 km. We provide a simple size distribution model that takes into consideration the oscillations of the power-law slope due to the transition from the gravity-scaled regime to the strength-scaled regime. We find that the high-inclination population has a shallow slope of the primary components of the size distribution compared to the low-inclination populations. The asteroid population exposed to hypervelocity impacts undergoes collisional processes where large bodies have a higher disruptive strength and longer lifespan relative to tiny bodies than the ecliptic asteroids.

  2. Crossing latitudes--long-distance tracking of an apex predator.

    PubMed

    Ferreira, Luciana C; Thums, Michele; Meeuwig, Jessica J; Vianna, Gabriel M S; Stevens, John; McAuley, Rory; Meekan, Mark G

    2015-01-01

    Tiger sharks (Galeocerdo cuvier) are apex predators occurring in most tropical and warm temperate marine ecosystems, but we know relatively little of their patterns of residency and movement over large spatial and temporal scales. We deployed satellite tags on eleven tiger sharks off the north-western coast of Western Australia and used the Brownian Bridge kernel method to calculate home ranges and analyse movement behaviour. One individual recorded one of the largest geographical ranges of movement ever reported for the species, travelling over 4000 km during 517 days of monitoring. Tags on the remainder of the sharks reported for shorter periods (7-191 days). Most of these sharks had restricted movements and long-term (30-188 days) residency in coastal waters in the vicinity of the area where they were tagged. Core home range areas of sharks varied greatly from 1166.9 to 634,944 km2. Tiger sharks spent most of their time in water temperatures between 23°-26°C but experienced temperatures ranging from 6°C to 33°C. One shark displayed seasonal movements among three distinct home range cores spread along most of the coast of Western Australia and generalized linear models showed that this individual had different patterns of temperature and depth occupancy in each region of the coast, with the highest probability of residency occurring in the shallowest areas of the coast with water temperatures above 23°C. These results suggest that tiger sharks can migrate over very large distances and across latitudes ranging from tropical to the cool temperate waters. Such extensive long-term movements may be a key element influencing the connectivity of populations within and among ocean basins. PMID:25671609

  3. High-latitude geomagnetic disturbances during ascending solar cycle 24

    NASA Astrophysics Data System (ADS)

    Peitso, Pyry; Tanskanen, Eija; Stolle, Claudia; Berthou Lauritsen, Nynne; Matzka, Jürgen

    2015-04-01

    High-latitude regions are very convenient for study of several space weather phenomena such as substorms. Large geographic coverage as well as long time series of data are essential due to the global nature of space weather and the long duration of solar cycles. We will examine geomagnetic activity in Greenland from magnetic field measurements taken by DTU (Technical University of Denmark) magnetometers during the years 2010 to 2014. The study uses data from 13 magnetometer stations located on the east coast of Greenland and one located on the west coast. The original measurements are in one second resolution, thus the amount of data is quite large. Magnetic field H component (positive direction towards the magnetic north) was used throughout the study. Data processing will be described from calibration of original measurements to plotting of long time series. Calibration consists of determining the quiet hour of a given day and reducing the average of that hour from all the time steps of the day. This normalizes the measurements and allows for better comparison between different time steps. In addition to the full time line of measurements, daily, monthly and yearly averages will be provided for all stations. Differential calculations on the change of the H component will also be made available for the duration of the full data set. Envelope curve plots will be presented for duration of the time line. Geomagnetic conditions during winter and summer will be compared to examine seasonal variation. Finally the measured activity will be compared to NOAA (National Oceanic and Atmospheric Administration) issued geomagnetic space weather alerts from 2010 to 2014. Calculations and plotting of measurement data were done with MATLAB. M_map toolbox was used for plotting of maps featured in the study (http://www2.ocgy.ubc.ca/~rich/map.html). The study was conducted as a part of the ReSoLVE (Research on Solar Long-term Variability and Effects) Center of Excellence.

  4. Two dimensional hydrodynamic modeling of a high latitude braided river

    NASA Astrophysics Data System (ADS)

    Humphries, E.; Pavelsky, T.; Bates, P. D.

    2014-12-01

    Rivers are a fundamental resource to physical, ecologic and human systems, yet quantification of river flow in high-latitude environments remains limited due to the prevalence of complex morphologies, remote locations and sparse in situ monitoring equipment. Advances in hydrodynamic modeling and remote sensing technology allow us to address questions such as: How well can two-dimensional models simulate a flood wave in a highly 3-dimensional braided river environment, and how does the structure of such a flood wave differ from flow down a similar-sized single-channel river? Here, we use the raster-based hydrodynamic model LISFLOOD-FP to simulate flood waves, discharge, water surface height, and velocity measurements over a ~70 km reach of the Tanana River in Alaska. In order to use LISFLOOD-FP a digital elevation model (DEM) fused with detailed bathymetric data is required. During summer 2013, we surveyed 220,000 bathymetric points along the study reach using an echo sounder system connected to a high-precision GPS unit. The measurements are interpolated to a smooth bathymetric surface, using Topo to Raster interpolation, and combined with an existing five meter DEM (Alaska IfSAR) to create a seamless river terrain model. Flood waves are simulated using varying complexities in model solvers, then compared to gauge records and water logger data to assess major sources of model uncertainty. Velocity and flow direction maps are also assessed and quantified for detailed analysis of braided channel flow. The most accurate model output occurs with using the full two-dimensional model structure, and major inaccuracies appear to be related to DEM quality and roughness values. Future work will intercompare model outputs with extensive ground measurements and new data from AirSWOT, an airborne analog for the Surface Water and Ocean Topography (SWOT) mission, which aims to provide high-resolution measurements of terrestrial and ocean water surface elevations globally.

  5. Study of the low latitude ionospheric turbulence observed by DEMETER

    NASA Astrophysics Data System (ADS)

    Li, F.; Lefeuvre, F.; Parrot, M.

    Following previous works from Molchanov et al 2002a 2002b 2004a 2004b and Hobara et al 2005 data bases dedicated to the systematic analysis of the power and spectral indices of the electric field have been elaborated Two data bases are considered one for the survey mode and the other for the burst mode For the survey mode estimations of the turbulence parameters are performed from the 8 first Fourier components of the averaged power spectra 0-150 Hz frequency band A single slope power law model f - alpha is assumed A quality factor allows to test that hypothesis For the burst mode the power spectra are derived from the waveforms One and two slope models are systematically tested Results are presented and the possibility to use these data bases for correlation with seismic activity is discussed Y Hobara F Lefeuvre M Parrot and O A Molchanov Low-latitude ionospheric turbulence observed by Aureol-3 satellite Annales Geophysicae 23 1259--1270 2005 Molchanov O A Hayakawa M Afonin V V Akentieva O A and Mareev E A Possible influence of seismicity by gravity waves on ionospheric equatorial anomaly from data of IK-24 satellite 1 Search for idea of seismo-ionosphere coupling Seismo Electromagnetics Lithosphere-Atmosphere-Ionosphere Coupling edited by Hayakawa M and Molchanov O A TERRAPUB Tokyo 275--285 2002a Molchanov O A Hayakawa M Afonin V V Akentieva O A Mareev E A and Trakhtengerts V Yu Possible influence of seismicity by gravity waves on ionospheric

  6. Under-Ice Operations with AUVS in High Latitudes

    NASA Astrophysics Data System (ADS)

    Ferguson, J.; Kaminski, C. D.

    2012-12-01

    In 2010 and 2011, ISE Explorer Autonomous Underwater Vehicles (AUV), built for Natural Resources Canada (NRCan), were deployed to Canada's high Arctic. The mission was to undertake under-ice bathymetric surveys supporting Canada's submission under the United Nations Convention on the Law of the Sea (UNCLOS). During these deployments several under-ice records were broken and several new technologies were demonstrated. The NRCan AUV is a 5000 meter depth rated vehicle, with several innovative additions to make it suitable for arctic survey work. Most notable are a depth rated variable ballast system, a 1300 Hz long-range homing system, and under-ice charging and data transfer capabilities. The Explorer's range was extended to approximately 450 km by adding a hull section to accommodate extra batteries. The scientific payload onboard included a Seabird SBE49 Conductivity-Temperature-Depth (CTD) sensor, Knudsen singlebeam echosounder, and a Kongsberg Simrad EM2000 multibeam echosounder. In 2010, operations were conducted from an ice camp near Borden Island (78°14'N, 112°39'W) operating through an ice hole. Following several test missions, the AUV spent 10 days surveying under ice before being successfully recovered. In total, close to 1100 km of under-ice survey was undertaken at depths to 3160 meters. A further set of operations was carried out in August and September 2011 from the Canadian Icebreaker CCGS Louis St. Laurent operating with the American Icebreaker USCGS Healy. Here the operations were much further north to latitudes of 88°30' N and to depths of 3500 meters. In this paper, the 2010 ice camp and the 2011 icebreaker missions are described, with an outline of technology developments that were undertaken, the preparations that were necessary for the success of the missions and finally, the outcome of the missions themselves.

  7. EDITORIAL: Northern Hemisphere high latitude climate and environmental change

    NASA Astrophysics Data System (ADS)

    Groisman, Pavel; Soja, Amber

    2007-10-01

    High Northern Hemisphere latitudes are undergoing rapid and significant change associated with climate warming. Climatic change in this region interacts with and affects the rate of the global change through atmospheric circulation, biogeophysical, and biogeochemical feedbacks. Changes in the surface energy balance, hydrologic cycle, and carbon budget feedback to regional and global weather and climate systems. Two-thirds of the Northern Hemisphere high latitude land mass resides in Northern Eurasia (~20% of the global land mass), and this region has undergone sweeping socio-economic change throughout the 20th century. How this carbon-rich, cold region component of the Earth system functions as a regional entity and interacts with and feeds back to the greater global system is to a large extent unknown. To mitigate the deficiencies in understanding these feedbacks, which may in turn hamper our understanding of the global change rates and patterns, an initiative was formed. Three years ago the Northern Eurasia Earth Science Partnership Initiative (NEESPI) was established to address large-scale and long-term manifestations of climate and environmental change in this region. The NEESPI Science Plan and its Executive Summary have been published at the NEESPI web site (neespi.org). Since 2004, NEESPI participants have been able to seed several waves of research proposals to international and national funding agencies and institutions and also contribute to the International Polar Year. Currently, NEESPI is widely recognized and endorsed by several Earth System Science Partnership (ESSP) programmes and projects: the International Geosphere and Biosphere Programme, the World Climate Research Programme through the Global Energy and Water Cycle Experiment and Climate and Cryosphere Projects, the Global Water System Project, Global Carbon Project, Global Land Project, and the Integrated Land Ecosystem—Atmosphere Processes Study. Through NEESPI, more than 100 individually

  8. Ionospheric F2 layer responses to total solar eclipses at low and mid-latitude

    NASA Astrophysics Data System (ADS)

    Adekoya, B. J.; Chukwuma, V. U.

    2016-02-01

    In this article, we presented ionospheric F2 responses to total solar eclipses on the basis of the data obtained from five (5) equatorial/low-latitude and twenty-seven (27) mid-latitude ionosonde stations, which are within the obscuration percentage of 50-100% of the path of the total solar eclipses progression. Statistically, the diurnal changes in the F2 layer peak height hmF2 and electron density NmF2, as well as the latitudinal and hemispheric dependence and the contribution of both magnetic and solar activities during the eclipse window were investigated. The estimation of the solar ionizing radiation that remains unmasked during the eclipse window was as well carried out. Plasma diffusion processes dominate the F2 region plasma, and determine the height at which the F2 peak formed at mid-latitude. The electron density decreased during the eclipse window, closely following the variation in the local solar radiation at the mid-latitude. However, at equatorial/low-latitude, the plasma distribution during total solar eclipse depends on combine effect of solar radiation and the background nighttime ionospheric irregularities mechanism. The uncertainty level of the estimated solar ionizing radiation was <±0.3 at mid-latitude and greater±0.3 at equatorial/low-latitude. Their correlation ranges from (0.42-0.99). The ionospheric F2 layer eclipse effect is latitudinal and hemispheric dependent. The effect is largest at mid-latitude and relatively small at equatorial/low-latitudes. It is more pronounced at the equator, and decreases toward the equatorial ionospheric anomaly (EIA) region. The better correlation of 0.5840 and 0.6435 between geographic latitude and E(t) and electron density justifies the latitudinal relationship. The increase in percentage deviation of electron density increases with latitude and delay time (∆T) in the northern hemisphere of the mid-latitude. Conversely, in the southern hemisphere the percentage deviation decreases with an increase in

  9. Comparative sequence stratigraphy of low-latitude versus high-latitude lacustrine rift basins: Seismic data examples from the East African and Baikal rifts

    USGS Publications Warehouse

    Scholz, C.A.; Moore, T.C., Jr.; Hutchinson, D.R.; Golmshtok, A. Ja; Klitgord, Kim D.; Kurotchkin, A.G.

    1998-01-01

    Lakes Baikal, Malawi and Tanganyika are the world's three largest rift valley lakes and are the classic modem examples of lacustrine rift basins. All the rift lakes are segmented into half-graben basins, and seismic reflection datasets reveal how this segmentation controls the filling of the rift basins through time. In the early stages of rifting, basins are fed primarily by flexural margin and axial margin drainage systems. At the climax of syn-rift sedimentation, however, when the basins are deeply subsided, almost all the margins are walled off by rift shoulder uplifts, and sediment flux into the basins is concentrated at accommodation zone and axial margin river deltas. Flexural margin unconformities are commonplace in the tropical lakes but less so in high-latitude Lake Baikal. Lake levels are extremely dynamic in the tropical lakes and in low-latitude systems in general because of the predominance of evaporation in the hydrologic cycle in those systems. Evaporation is minimized in relation to inflow in the high-latitude Lake Baikal and in most high-latitude systems, and consequently, major sequence boundaries tend to be tectonically controlled in that type of system. The acoustic stratigraphies of the tropical lakes are dominated by high-frequency and high-amplitude lake level shifts, whereas in high-latitude Lake Baikal, stratigraphic cycles are dominated by tectonism and sediment-supply variations.

  10. Modeling the above and below ground carbon and nitrogen stocks in northern high latitude terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    ElMasri, B.; Jain, A. K.

    2012-12-01

    Climate change is expected to cause warming in the northern high latitudes, but it is still uncertain what the respond of the northern high latitudes ecosystem will be to such warming. One of the biggest scientific questions is to determine whether northern high latitude ecosystem are or will act as a terrestrial carbon sink or source. Therefore, it is essential to understand and quantify the biogeochemical cycle of the northern high latitude ecosystems in order to predict their respond to climate change. Using a land surface model, the Integrated Science Assessment Model (ISAM) with its coupled carbon-nitrogen cycle, we provide a detail quantification of the carbon and nitrogen in the vegetation pools and the soil carbon for the northern high latitude ecosystems. We focus on soil carbon and vegetation carbon and nitrogen, though we provide results for gross primary production (GPP), autotrophic respiration (Ra), net primary production (NPP), net ecosystem exchange (NEE), and heterotrophic respiration (Rh). In addition, we examine the effect of nitrogen limitation on the carbon fluxes and soil carbon. We present the results for several flux tower sites representative of the tundra and the boreal ecosystems as well as for the northern high latitude region. Our results provide a comprehensive assessment of below and above ground carbon and nitrogen pools in the northern high latitude and the model calibrated parameters can be used to improve the results of other land surface models.

  11. Does greater thermal plasticity facilitate range expansion of an invasive terrestrial anuran into higher latitudes?

    PubMed Central

    Winwood-Smith, Hugh S.; Alton, Lesley A.; Franklin, Craig E.; White, Craig R.

    2015-01-01

    Temperature has pervasive effects on physiological processes and is critical in setting species distribution limits. Since invading Australia, cane toads have spread rapidly across low latitudes, but slowly into higher latitudes. Low temperature is the likely factor limiting high-latitude advancement. Several previous attempts have been made to predict future cane toad distributions in Australia, but understanding the potential contribution of phenotypic plasticity and adaptation to future range expansion remains challenging. Previous research demonstrates the considerable thermal metabolic plasticity of the cane toad, but suggests limited thermal plasticity of locomotor performance. Additionally, the oxygen-limited thermal tolerance hypothesis predicts that reduced aerobic scope sets thermal limits for ectotherm performance. Metabolic plasticity, locomotor performance and aerobic scope are therefore predicted targets of natural selection as cane toads invade colder regions. We measured these traits at temperatures of 10, 15, 22.5 and 30°C in low- and high-latitude toads acclimated to 15 and 30°C, to test the hypothesis that cane toads have adapted to cooler temperatures. High-latitude toads show increased metabolic plasticity and higher resting metabolic rates at lower temperatures. Burst locomotor performance was worse for high-latitude toads. Other traits showed no regional differences. We conclude that increased metabolic plasticity may facilitate invasion into higher latitudes by maintaining critical physiological functions at lower temperatures. PMID:27293695

  12. A computer program for converting rectangular coordinates to latitude-longitude coordinates

    USGS Publications Warehouse

    Rutledge, A.T.

    1989-01-01

    A computer program was developed for converting the coordinates of any rectangular grid on a map to coordinates on a grid that is parallel to lines of equal latitude and longitude. Using this program in conjunction with groundwater flow models, the user can extract data and results from models with varying grid orientations and place these data into grid structure that is oriented parallel to lines of equal latitude and longitude. All cells in the rectangular grid must have equal dimensions, and all cells in the latitude-longitude grid measure one minute by one minute. This program is applicable if the map used shows lines of equal latitude as arcs and lines of equal longitude as straight lines and assumes that the Earth 's surface can be approximated as a sphere. The program user enters the row number , column number, and latitude and longitude of the midpoint of the cell for three test cells on the rectangular grid. The latitude and longitude of boundaries of the rectangular grid also are entered. By solving sets of simultaneous linear equations, the program calculates coefficients that are used for making the conversion. As an option in the program, the user may build a groundwater model file based on a grid that is parallel to lines of equal latitude and longitude. The program reads a data file based on the rectangular coordinates and automatically forms the new data file. (USGS)

  13. Latitude distribution of track and field elite athletes in China mainland

    NASA Astrophysics Data System (ADS)

    Li, Cheng-Zhang; Liu, Timon Cheng-Yi; Cui, Li-Ping; Xu, Xiao-Yang; Jin, Hua

    2006-01-01

    The civilization theories prevailed among people are the theories paying attention to the geographical factors. In this paper, the latitude distribution of track and field elite athletes in China mainland has been studied in terms of the biological effects of sunlight. The China mainland is divided into seven latitude zones according to the absolute latitude value so that the larger the zone number is, the larger the distance from the Equator. The elite athletes are classified into speed-type, jump-type, strength-type and endurance-type so that the latitude distribution can be discussed in terms of exercise physiology. The latitude distribution shows that the elite athletes of speed-type or jump-type prefer to the zones of low latitude, and the elite athletes of strength-type or endurance-type prefer to the zones of high latitude. These phenomena can be understood by the effects of sunlight on exercise physiological index such as skeletal muscle fibre types.

  14. On an energy-latitude dispersion pattern of ion precipitation potentially associated with magnetospheric EMIC waves

    NASA Astrophysics Data System (ADS)

    Liang, Jun; Donovan, E.; Ni, B.; Yue, C.; Jiang, F.; Angelopoulos, V.

    2014-10-01

    Ion precipitation mechanisms are usually energy dependent and contingent upon magnetospheric/ionospheric locations. Therefore, the pattern of energy-latitude dependence of ion precipitation boundaries seen by low Earth orbit satellites can be implicative of the mechanism(s) underlying the precipitation. The pitch angle scattering of ions led by the field line curvature, a well-recognized mechanism of ion precipitation in the central plasma sheet (CPS), leads to one common pattern of energy-latitude dispersion, in that the ion precipitation flux diminishes at higher (lower) latitudes for protons with lower (higher) energies. In this study, we introduce one other systematically existing pattern of energy-latitude dispersion of ion precipitation, in that the lower energy ion precipitation extends to lower latitude than the higher-energy ion precipitation. Via investigating such a "reversed" energy-latitude dispersion pattern, we explore possible mechanisms of ion precipitation other than the field line curvature scattering. We demonstrate via theories and simulations that the H-band electromagnetic ion cyclotron (EMIC) wave is capable of preferentially scattering keV protons in the CPS and potentially leads to the reversed energy-latitude dispersion of proton precipitation. We then present detailed event analyses and provide support to a linkage between the EMIC waves in the equatorial CPS and ion precipitation events with reversed energy-latitude dispersion. We also discuss the role of ion acceleration in the topside ionosphere which, together with the CPS ion population, may result in a variety of energy-latitude distributions of the overall ion precipitation.

  15. Cantico Delle Creature: A microtonal original composition for soprano and string quartet to a text by St. Francis of Assisi, including analytical commentary

    NASA Astrophysics Data System (ADS)

    Sabol, Jason A.

    Cantico delle Creature is an original piece of music for soprano and string quartet composed in 72 tone per octave equal temperament, dividing each semitone into six equal parts called twelfth-tones. This system of tuning makes it possible to combine just intonation and spectral principles based on the harmonic series with real imitation, modulation, and polyphony. Supplemental text discusses several aspects of microtonal structure and pedagogy, including the representation of the first 64 partials of the harmonic series in 72 tone equal temperament, performance of natural string harmonics, the relationship between interval size and vibration ratio, pitch to frequency conversion, and analysis of several passages in the musical score.

  16. In situ measurements constraining the role of sulphate aerosols in mid-latitude ozone depletion

    NASA Technical Reports Server (NTRS)

    Fahey, D. W.; Kawa, S. R.; Woodbridge, E. L.; Tin, P.; Wilson, J. C.; Jonsson, H. H.; Dye, J. E.; Baumgardner, D.; Borrmann, S.; Toohey, D. W.

    1993-01-01

    In situ measurements of stratospheric sulphate aerosol, reactive nitrogen and chlorine concentrations at middle latitudes confirm the importance of aerosol surface reactions that convert active nitrogen to a less active, reservoir form. This makes mid-latitude stratospheric ozone less vulnerable to active nitrogen and more vulnerable to chlorine species. The effect of aerosol reactions on active nitrogen depends on gas phase reaction rates, so that increases in aerosol concentration following volcanic eruptions will have only a limited effect on ozone depletion at these latitudes.

  17. Variability of Winter Air Temperature in Mid-Latitude Europe

    NASA Technical Reports Server (NTRS)

    Otterman, J.; Ardizzone, J.; Atlas, R.; Bungato, D.; Cierniewski, J.; Jusem, J. C.; Przybylak, R.; Schubert, S.; Starr, D.; Walczewski, J.

    2002-01-01

    The aim of this paper is to report extreme winter/early-spring air temperature (hereinafter temperature) anomalies in mid-latitude Europe, and to discuss the underlying forcing to these interannual fluctuations. Warm advection from the North Atlantic in late winter controls the surface-air temperature, as indicated by the substantial correlation between the speed of the surface southwesterlies over the eastern North Atlantic (quantified by a specific Index Ina) and the 2-meter level air temperatures (hereinafter Ts) over Europe, 45-60 deg N, in winter. In mid-March and subsequently, the correlation drops drastically (quite often it is negative). This change in the relationship between Ts and Ina marks a transition in the control of the surface-air temperature: absorption of insolation replaces the warm advection as the dominant control. This forcing by maritime-air advection in winter was demonstrated in a previous publication, and is re-examined here in conjunction with extreme fluctuations of temperatures in Europe. We analyze here the interannual variability at its extreme by comparing warm-winter/early-spring of 1989/90 with the opposite scenario in 1995/96. For these two December-to-March periods the differences in the monthly mean temperature in Warsaw and Torun, Poland, range above 10 C. Short-term (shorter than a month) fluctuations of the temperature are likewise very strong. We conduct pentad-by-pentad analysis of the surface-maximum air temperature (hereinafter Tmax), in a selected location, examining the dependence on Ina. The increased cloudiness and higher amounts of total precipitable water, corollary effects to the warm low-level advection. in the 1989/90 winter, enhance the positive temperature anomalies. The analysis of the ocean surface winds is based on the Special Sensor Microwave/Imager (SSM/I) dataset; ascent rates, and over land wind data are from the European Centre for Medium-Range Weather Forecasts (ECMWF); maps of 2-m temperature, cloud

  18. High-Latitude Ionospheric Structuring at Kilometer Scales

    NASA Astrophysics Data System (ADS)

    Bust, G. S.; Datta-Barua, S.; Su, Y.; Deshpande, K.; Hampton, D.

    2014-12-01

    Ionospheric observations in the polar and auroral zones have been made regularly with radar chains and optical imaging at larger spatio-temporal cadence. However, the observation of kilometer scale variations at sub-second cadence has not been practically realizable until recently. Quantifying the irregularities at these sizes and scales is necessary for an understanding of the dynamics leading to fine scale phenomena in the high latitude environment. We present measurements of kilometer-scale plasma variations made at the northern auroral zone using an array of specialized Global Positioning System (GPS) receivers. These 6 CASES receivers (plus 1 from ASTRA, LLC) are sited at the Poker Flat Research Range, Alaska, and have been collecting data since late 2013. The array monitors for ionospheric scintillations, fluctuations in phase and amplitude of the GPS L-band signals received due to ionospheric variations. The array spans 2 km east-west and about 1 km north-south, with a variety of intermediate baseline lengths down to about 200 m. In addition to measuring amplitude and phase scintillation with the S4 and sigma_phi indices at 100-s cadence, these receivers also record 100 Hz raw power and phase measurements from GPS baseband signal processing. These low-rate data are publicly available for download through a web portal at http://apollo.tbc.iit.edu/~spaceweather/ with high rate available upon request. A detailed case study is presented from the December 8, 2013, 0300-0400 UT time period. During this period several interesting scintillation periods were observed. We use array cross-correlation processing methods to first estimate direct ground parameters of the array including a) estimate the 2D drift velocity on the ground; b) estimate a de-correlation (or turbulent) speed; and c) parameters of correlation elliptical coordinates (axial ratio and tilt angle). We then use these results and cross-correlation measurements to derive the ground 2D spatial spectrum of

  19. Northern high latitude climate variability of the last millennium

    NASA Astrophysics Data System (ADS)

    Andres, Heather J.

    This work explores the causes of northern high-latitude climate variations over the last millennium, and industrial and future periods. Attribution studies are performed on a suite of global climate simulations, and four historical reconstructions of Greenland surface temperatures and precipitation (two of which are new to this work). The simulations followed the protocols of the Palaeoclimate Modelling Intercomparison Project 3 and Coupled Model Intercomparison Project 5. At least half of the multi-decadal variability in simulated Greenland climate variations over the last millennium is reproduced by a linear, empirically-generated model including terms for volcanic emissions, solar insolation changes (including total solar irradiance and orbital components) and an index associated with latitudinal shifts in the North Atlantic jet. Empirical model parameters are obtained by regressing simulated Greenland temperatures and precipitation against time series for each of the response variables. Greenhouse gas radiative forcing changes are unimportant to simulated Greenland conditions over the last millennium, although they dominate after the mid-20th century. Most of the historical Greenland climate reconstructions are restricted to the industrial period, due to a lack of spatially-comprehensive climate records. They exhibit substantial differences in the timing, phasing and amplitudes of past climate variations, due to regional sensitivities in the source data and the reconstruction methodologies. Reconstructions indicate that Greenland temperatures did not begin to follow hemispheric greenhouse gas warming patterns until the mid-1990s. This discrepancy indicates either that the warming hiatus was associated with internal climate variability, or that the simulations are missing processes important to Greenland climate. For example, indirect effects of anthropogenic aerosols are not captured in the climate model employed here. All of the external climate forcings

  20. Exchange across the shelf break at high southern latitudes

    NASA Astrophysics Data System (ADS)

    Klinck, J. M.; Dinniman, M. S.

    2010-05-01

    Exchange of water across the Antarctic shelf break has considerable scientific and societal importance due to its effects on circulation and biology of the region, conversion of water masses as part of the global overturning circulation and basal melt of glacial ice and the consequent effect on sea level rise. The focus in this paper is the onshore transport of warm, oceanic Circumpolar Deep Water (CDW); export of dense water from these shelves is equally important, but has been the focus of other recent papers and will not be considered here. A variety of physical mechanisms are described which could play a role in this onshore flux. The relative importance of some processes are evaluated by simple calculations. A numerical model for the Ross Sea continental shelf is used as an example of a more comprehensive evaluation of the details of cross-shelf break exchange. In order for an ocean circulation model to simulate these processes at high southern latitudes, it needs to have high spatial resolution, realistic geometry and bathymetry. Grid spacing smaller than the first baroclinic radius of deformation (a few km) is required to adequately represent the circulation. Because of flow-topography interactions, bathymetry needs to be represented at these same small scales. Atmospheric conditions used to force these circulation models also need to be known at a similar small spatial resolution (a few km) in order to represent orographically controlled winds (coastal jets) and katabatic winds. Significantly, time variability of surface winds strongly influences the structure of the mixed layer. Daily, if not more frequent, surface fluxes must be imposed for a realistic surface mixed layer. Sea ice and ice shelves are important components of the coastal circulation. Ice isolates the ocean from exchange with the atmosphere, especially in the winter. Melting and freezing of both sea ice and glacial ice influence salinity and thereby the character of shelf water. These water

  1. Exchange across the shelf break at high southern latitudes

    NASA Astrophysics Data System (ADS)

    Klinck, J. M.; Dinniman, M. S.

    2010-01-01

    Exchange of water across the Antarctic shelf break has considerable scientific and societal importance due to its effects on circulation and biology of the region, conversion of water masses as part of the global overturning circulation and basal melt of glacial ice and the consequent effect on sea level rise. The focus in this paper is the onshore transport of warm, oceanic Circumpolar Deep Water (CDW); export of dense water from these shelves is equally important, but has been the focus of other recent papers and will not be considered here. A variety of physical mechanisms are described which could play a role in this onshore flux. The relative importance of some processes are evaluated by simple calculations. A numerical model for the Ross Sea continental shelf is used as an example of a more comprehensive evaluation of the details of cross-shelf break exchange. In order for an ocean circulation model simulate these processes at high southern latitudes, it needs to have high spatial resolution, realistic geometry and bathymetry. Grid spacing smaller than the first baroclinic radius deformation (a few km) is required to adequately represent the circulation. Because of flow-topography interactions, bathymetry needs to be represented at these same small scales. Atmospheric conditions used to force these circulation models also need to be known at a similar small spatial resolution (a few km) in order to represent orographically controlled winds (coastal jets) and katabatic winds. Significantly, time variability of surface winds strongly influences the structure of the mixed layer. Daily, if not more frequent, surface fluxes must be imposed for a realistic surface mixed layer. Sea ice and ice shelves are important components of the coastal circulation. Ice isolates the ocean from exchange with the atmosphere, especially in the winter. Melting and freezing of both sea ice and glacial ice influence salinity and thereby the character of shelf water. These water mass

  2. Intercomparison of mid latitude storm diagnostics (IMILAST) - project update

    NASA Astrophysics Data System (ADS)

    Neu, Urs

    2014-05-01

    The analysis of the occurrence of mid-latitude storms is of great socio-economical interest due to their vast and destructive impacts. However, a unique definition of cyclones is missing as they are complex systems which may have very diverse characteristics. Thus, the definition of what a cyclone is as well as quantifying its strength contains subjective choices. Existing automatic cyclone identification and tracking algorithms are based on different definitions and use diverse characteristics. These methods generally differ in the following aspects: data transformation (e.g., grid transformation, smoothing, etc.), metrics used for cyclone identification (e.g. sea level pressure or vorticity), cyclone identification procedures, different tracking methods (e.g. near neighborhood search), and elimination criteria (e.g., requiring a certain pressure minimum or minimum life time). The different choices made in these algorithms can lead to substantial differences in cyclone climatologies, temporal trends of the frequency, strength, or other characteristics of cyclones. These differences render the interpretation and comparison of cyclone studies rather difficult. The project IMILAST systematically compares different cyclone detection and tracking methods (currently 15 different algorithms), with the aim to comprehensively assess systematic uncertainties in mid-latitudinal storm identification and tracking. As a common data basis the ERA-interim reanalysis data set is used in all IMILAST studies. A first study presented a general overview of differences between the methods with respect to number, track density, life cycle characteristics, and trend patterns for a 20 year period of ERA-Interim. In a second study, potential differences of the long-term climate change signal of cyclonic activity between the methods were assessed. Currently, the intercomparison is extended to a 30 year period from 1979 to 2009 and focuses on more specific aspects, such as parameter

  3. Intercomparison of mid latitude storm diagnostics (IMILAST) - project update

    NASA Astrophysics Data System (ADS)

    Neu, Urs

    2013-04-01

    The detection of the occurrence of mid-latitude storms, which are of high societal interest due to their impacts, is less straightforward than it might seem. Since cyclones are complex systems with very diverse characteristics, the definition of what a cyclone is and what should be considered as describing the strength of a cyclone contains subjective choices. Thus, existing analysis methods, especially automatic algorithms, are based on different definitions and use diverse identification and tracking (i.e. detecting the path of an individual cyclone over time) methodologies. The different choices made in different cyclone identification and tracking algorithms can lead to critical differences in temporal trends of the frequency, strength or life cycle of cyclones. These differences render the interpretation and comparison of cyclone trend studies difficult. The project IMILAST performs a systematic intercomparison of different existing cyclone detection and tracking methods (currently 15 different algorithms), with the aim of a comprehensive assessment of methodological uncertainties in mid-latitudinal storm tracking and an overview of advantages and restrictions of different schemes. As input data all calculations used the same ERA-interim reanalysis data set. The methods generally differ in the following aspects: data transformation (e.g. grid transformation, smoothing), metrics used for cyclone identification (e.g. sea level pressure or vorticity), cyclone identification procedures, different tracking methods (how to combine the cyclone centers at different times to a track), and elimination criteria (e.g. requiring a certain pressure minimum or minimum life time). After a first experiment comparing cyclone tracks for a 20 year test period for both the northern and southern hemispheres, now the detection of a set of 22 individual extreme storms by the different methods has been analysed. In addition, more specific analysis, as for example the influence of

  4. Intercomparison of mid latitude storm diagnostics (IMILAST) - project update

    NASA Astrophysics Data System (ADS)

    Neu, U.

    2012-04-01

    The detection of the occurrence of mid-latitude storms, which are of high societal interest due to their impacts, is less straightforward than it might seem. Since cyclones are complex systems with very diverse characteristics, the definition of what a cyclone is and what should be considered as describing the strength of a cyclone contains subjective choices. Thus, existing analysis methods, especially automatic algorithms, are based on different definitions and use diverse identification and tracking (i.e. detecting the path of an individual cyclone over time) methodologies. The different choices made in different cyclone identification and tracking algorithms can lead to critical differences in temporal trends of the frequency, strength or life cycle of cyclones. These differences render the interpretation and comparison of cyclone trend studies difficult. The project IMILAST performs a systematic intercomparison of different existing cyclone detection and tracking methods, with the aim of a comprehensive assessment of methodological uncertainties in mid-latitudinal storm tracking and an overview of advantages and restrictions of different schemes. The intensive discussions of first results have already pointed out a number of important issues that have to be carefully considered, and where some harmonization might make sense, like e.g. the arbitrary choice of thresholds like minimum life time or the elimination of cyclone tracks over high terrain. Currently, cyclone tracks for a 20 year test period for both the northern and southern hemispheres have been calculated with 15 different methodologies. As input data all calculations used the same ERA-interim reanalysis data set. The methods generally differ in the following aspects: data transformation (e.g. grid transformation, smoothing), metrics used for cyclone identification (e.g. sea level pressure or vorticity), cyclone identification procedures, different tracking methods (how to combine the cyclone centers

  5. Intercomparison of mid latitude storm diagnostics (IMILAST) - project update

    NASA Astrophysics Data System (ADS)

    Neu, Urs

    2015-04-01

    The analysis of the occurrence of mid-latitude storms is of great socio-economical interest due to their vast and destructive impacts. However, a unique definition of cyclones is missing, and therefore the definition of what a cyclone is as well as quantifying its strength contains subjective choices. Existing automatic cyclone identification and tracking algorithms are based on different definitions and use diverse characteristics. These methods generally differ in the following aspects: data transformation (e.g., grid transformation, smoothing, etc.), metrics used for cyclone identification (e.g. sea level pressure or vorticity), cyclone identification procedures, different tracking methods (e.g. near neighborhood search), and elimination criteria (e.g., requiring a certain pressure minimum or minimum life time). The different choices made in these algorithms can lead to substantial differences in cyclone climatologies, temporal trends of the frequency, strength, or other characteristics of cyclones. The project IMILAST systematically compares different cyclone detection and tracking methods (currently 15 different algorithms), with the aim to comprehensively assess systematic uncertainties in mid-latitudinal storm identification and tracking. IMILAST uses the ERA-interim reanalysis data set as a common data basis in all studies. The first two intercomparison experiments focused on differences between the methods with respect to number, track density, life cycle characteristics, and trend patterns on the one hand and potential differences of the long-term climate change signal of cyclonic activity between the methods on the other hand. For current analysis activities, the intercomparison period is extended to a 30 year period from 1979 to 2009 and focuses on more specific aspects, such as parameter sensitivities, the comparison of automated to manual tracking sets, regional analysis (regional trends, Arctic and Antarctic cyclones, cyclones in the Mediterranean

  6. New Findings on Ice Nucleation in Mid-latitude Cirrus

    NASA Astrophysics Data System (ADS)

    Mishra, S.; Mitchell, D. L.; Lawson, P.; Baker, B. A.

    2011-12-01

    Recent GCM simulations (CESM1) show a global aerosol indirect effect of -1.39 W m-2 with -2.02 W m-2 from shortwave and +0.63 W m-2 from longwave cloud forcing, the longwave being due to homogeneous nucleation of ice crystals. However, the extent of homogeneous nucleation in ice clouds is poorly understood. This study uses results from a recent field campaign, SPARTICUS (Small PARTicles In CirrUS), to evaluate the impact of homogeneous nucleation on the ice particle size distribution (PSD) shape, as well as ice particle concentration, shape, PSD effective size and fall speed. While earlier measurements were difficult to evaluate for ice nucleation effects due to the problem of ice particle shattering, recent in-situ measurements using the 2 dimensional-stereo (2D-S) probe have greatly reduced this problem resulting in provocative findings for both synoptic and anvil cirrus sampled during SPARTICUS. For mid-latitude synoptic and anvil cirrus around -40°C, these new measurements show that clear changes in the ice PSD and its properties occur regarding (1) PSD shape, (2) total number concentration-to-ice water content ratio (N/IWC), (3) PSD mean size, (4) PSD mean area ratio and (5) the mass-weighted fall velocity (Vm). These changes are consistent with a change in ice nucleation mechanism, with heterogeneous nucleation processes active at temperatures warmer than -40°C and homogeneous freezing nucleation at temperatures colder than -40°C. The change in Vm implies that cirrus colder than -40°C will have longer lifetimes and greater cloud coverage than warmer cirrus clouds, all other relevant factors remaining equal. The increase in N/IWC with colder temperatures (T < -40°C) appears consistent with homogeneous nucleation theory. Figure 1 shows normalized frequency distribution of PSD area ratios for temperatures above and below -40°C. Area ratios (ice particle projected area/area of circle defined by particle maximum dimension) are a measure of ice particle shape

  7. Galactic dust polarized emission at high latitudes and CMB polarization

    NASA Astrophysics Data System (ADS)

    Prunet, S.; Sethi, S. K.; Bouchet, F. R.; Miville-Deschenes, M.-A.

    1998-11-01

    With recent instrumental advances, it might become possible to measure the polarization of the Cosmic Microwave Background (CMB), e.g. by future space missions like MAP and Planck Surveyor. In this paper, we estimate the dust polarized emission in our galaxy which is the major foreground to cope with for measuring the CMB polarization in the Wien part of CMB spectrum. We model the dust polarized emission in the galaxy using the three-dimensional HI maps of the Leiden/Dwingeloo survey at high galactic latitudes. We use the fact that the dust emission, for a wide range of wavelengths, has a tight correlation with the HI emission maps of this survey (Boulanger et al. 1996). Assuming the dust grains to be oblate with axis ratio =~ 2/3, which recent studies support, we determine the intrinsic dust polarized emissivity. The distribution of magnetic field with respect to the dust grain distribution is quite uncertain, we thus consider three extreme cases: (1) The magnetic field is aligned with the major axis of the dust structure, (2) the magnetic field has a random direction in the plane perpendicular to the direction of major axis of the dust structure, and (3) the magnetic field is unidirectional throughout. We further assume, as recent observations and theoretical analyses support, that the dust grains align with the magnetic field independently of its strength. The polarization reduction factor from misalignment of the direction of polarization from the plane of the sky and the differential polarization along a line of sight is calculated using these maps, to construct two-dimensional maps of dust polarized emission. We calculate the angular power spectrum of dust polarized emission from these maps and cast it in variables which allow a direct comparison with the polarized component of the CMB. Our results, at frequencies =~ 100 GHz, suggest that: (a) This foreground contamination is smaller than the scalar-induced polarization of the CMB at l ga 200 while the tensor

  8. Modeling the effects of snowpack on heterotrophic respiration across northern temperate and high latitude regions: Comparison with measurements of atmospheric carbon dioxide in high latitudes

    USGS Publications Warehouse

    McGuire, A.D.; Melillo, J.M.; Randerson, J.T.; Parton, W.J.; Heimann, Martin; Meier, R.A.; Clein, J.S.; Kicklighter, D.W.; Sauf, W.

    2000-01-01

    Simulations by global terrestrial biogeochemical models (TBMs) consistently underestimate the concentration of atmospheric carbon dioxide (CO2) at high latitude monitoring stations during the nongrowing season. We hypothesized that heterotrophic respiration is underestimated during the nongrowing season primarily because TBMs do not generally consider the insulative effects of snowpack on soil temperature. To evaluate this hypothesis, we compared the performance of baseline and modified versions of three TBMs in simulating the seasonal cycle of atmospheric CO2 at high latitude CO2 monitoring stations; the modified version maintained soil temperature at 0 ??C when modeled snowpack was present. The three TBMs include the Carnegie-Ames-Stanford Approach (CASA), Century, and the Terrestrial Ecosystem Model (TEM). In comparison with the baseline simulation of each model, the snowpack simulations caused higher releases of CO2 between November and March and greater uptake of CO2 between June and August for latitudes north of 30??N. We coupled the monthly estimates of CO2 exchange, the seasonal carbon dioxide flux fields generated by the HAMOCC3 seasonal ocean carbon cycle model, and fossil fuel source fields derived from standard sources to the three-dimensional atmospheric transport model TM2 forced by observed winds to simulate the seasonal cycle of atmospheric CO2 at each of seven high latitude monitoring stations, in comparison to the CO2 concentrations simulated with the baseline fluxes of each TBM, concentrations simulated using the snowpack fluxes are generally in better agreement with observed concentrations between August and March at each of the monitoring stations. Thus, representation of the insulative effects of snowpack in TBMs generally improves simulation of atmospheric CO2 concentrations in high latitudes during both the late growing season and nongrowing season. These simulations highlight the global importance of biogeochemical processes during the

  9. The latitude dependencies of the solar wind. [of interplanetary magnetic field polarity and configurations

    NASA Technical Reports Server (NTRS)

    Rosenberg, R. L.; Winge, C. R., Jr.

    1974-01-01

    The motion of spacecraft following the earth's orbit occurs within the solar latitude range of 7 deg 15 min N on approximately September 7 to 7 deg 15 min S on approximately March 6. The latitude dependencies so far detected within this range have shown that the photospheric dipole-like field of the sun makes very important contributions to the interplanetary magnetic field (IMF) observed near the ecliptic. Changes in geomagnetic activity from even to odd numbered 11-year solar cycles are related to changes in the sun's dipolar field. The north-south IMF component and meridional, nonradial flow are important to a complete understanding of steady-state solar wind dynamics. Coronal conditions must be latitude-dependent in a way that accounts for the observed latitude dependence of the velocity and density of the solar wind.

  10. Understanding the Latitude Structure of Nitric Oxide in the Mesosphere and Lower Thermosphere

    NASA Technical Reports Server (NTRS)

    Fuller-Rowell, T.J.

    1997-01-01

    The goal of the proposed work was to understand the latitude structure of nitric oxide in the mesosphere and lower thermosphere. The problem was portrayed by a clear difference between predictions of the nitric oxide distribution from chemical/dynamical models and data from observations made by the Solar Mesosphere Explorer (SMEE) in the early to mid eighties. The data exhibits a flat latitude structure of NO, the models tend to produce at equatorial maximum. The first task was to use the UARS-HALOE data to confirm the SME observations. The purpose of this first phase was to verify the UARS-NO structure is consistent with the SME data. The next task was to determine the cause of the discrepancy between modeled and observed nitric oxide latitude structure. The result from the final phase indicated that the latitude structure in the Photo-Electron (PE) production rate was the most important.

  11. Stratospheric transport from the tropics to middle latitudes by planetary-wave mixing

    NASA Astrophysics Data System (ADS)

    Randel, W. J.; Gille, J. C.; Roche, A. E.; Kumer, J. B.; Mergenthaler, J. L.; Waters, J. W.; Fishbein, E. F.; Lahoz, W. A.

    1993-10-01

    TRANSPORT of air from the troposphere to the stratosphere takes place mainly in the tropics1. By studying satellite records of the dispersal of volcanic aerosols from tropical eruptions, Trepte and Hitchman2 concluded that there is a barrier inhibiting the transport of stratospheric air from the tropics to middle latitude, raising the question of how stratospheric material that has been transported from the troposphere is subsequently conveyed to higher latitudes. Here we present global maps of nitrous oxide and water mixing ratios obtained by the Upper Atmosphere Research Satellite. We see strong latitudinal gradients in these trace species, confirming the existence of a barrier to transport. But superimposed on this background structure we also see planetary-scale `tongues' of tropical stratospheric air extending out into middle latitudes, and time sequences show irreversible mixing from the tropics into middle latitudes. Such episodes could be responsible for transporting significant quantities of stratospheric air across the tropical barrier.

  12. HIGH-LATITUDE SOLAR TORSIONAL OSCILLATIONS DURING PHASES OF CHANGING MAGNETIC CYCLE AMPLITUDE

    SciTech Connect

    Rempel, M.

    2012-05-01

    Torsional oscillations are variations of the solar differential rotation that are strongly linked to the magnetic cycle of the Sun. Helioseismic inversions have revealed significant differences in the high-latitude branch of torsional oscillations between cycle 23 and cycle 24. Here we employ a non-kinematic flux-transport dynamo model that has been used previously to study torsional oscillations and simulate the response of the high-latitude branch to a change in the amplitude of the magnetic cycle. It is found that a reduction of the cycle amplitude leads to an increase in the amplitude of differential rotation that is mostly visible as a drop in the high-latitude rotation rate. Depending on the amplitude of this adjustment the high-latitude torsional oscillation signal can become temporarily hidden due to the unknown changing mean rotation rate that is required to properly define the torsional oscillation signal.

  13. Can genetically based clines in plant defence explain greater herbivory at higher latitudes?

    PubMed

    Anstett, Daniel N; Ahern, Jeffrey R; Glinos, Julia; Nawar, Nabanita; Salminen, Juha-Pekka; Johnson, Marc T J

    2015-12-01

    Greater plant defence is predicted to evolve at lower latitudes in response to increased herbivore pressure. However, recent studies question the generality of this pattern. In this study, we tested for genetically based latitudinal clines in resistance to herbivores and underlying defence traits of Oenothera biennis. We grew plants from 137 populations from across the entire native range of O. biennis. Populations from lower latitudes showed greater resistance to multiple specialist and generalist herbivores. These patterns were associated with an increase in total phenolics at lower latitudes. A significant proportion of the phenolics were driven by the concentrations of two major ellagitannins, which exhibited opposing latitudinal clines. Our analyses suggest that these findings are unlikely to be explained by local adaptation of herbivore populations or genetic variation in phenology. Rather greater herbivory at high latitudes can be explained by latitudinal clines in the evolution of plant defences. PMID:26482702

  14. Lean production tools and decision latitude enable conditions for innovative learning in organizations: a multilevel analysis.

    PubMed

    Fagerlind Ståhl, Anna-Carin; Gustavsson, Maria; Karlsson, Nadine; Johansson, Gun; Ekberg, Kerstin

    2015-03-01

    The effect of lean production on conditions for learning is debated. This study aimed to investigate how tools inspired by lean production (standardization, resource reduction, visual monitoring, housekeeping, value flow analysis) were associated with an innovative learning climate and with collective dispersion of ideas in organizations, and whether decision latitude contributed to these associations. A questionnaire was sent out to employees in public, private, production and service organizations (n = 4442). Multilevel linear regression analyses were used. Use of lean tools and decision latitude were positively associated with an innovative learning climate and collective dispersion of ideas. A low degree of decision latitude was a modifier in the association to collective dispersion of ideas. Lean tools can enable shared understanding and collective spreading of ideas, needed for the development of work processes, especially when decision latitude is low. Value flow analysis played a pivotal role in the associations. PMID:25479999

  15. Relationships between cosmic ray neutron flux and rain flows in dependence on different latitudes and altitudes

    NASA Astrophysics Data System (ADS)

    Velinov, Peter; Velinov, Peter; Belov, Anatolii; Yanke, Viktor; Eroshenko, Evgenia; Mishev, Alexander; Tassev, Yordan

    A convenient tool for investigation of primary cosmic ray variations is the registration of secondary cosmic ray neutrons. A network of neutron monitors, aiming the studies of cosmic ray variations exists. At the same time cosmic ray variations may be related to some atmospheric processes. In this connection, using the data from Moskow neutron monitor (latitude 55 degree) and lead free neutron monitor at BEO Moussala (latitude 42 degree and latitude 2971 m above see level), we studied the correlations between rain flows and neutron flux. In this study we used daily averages on the basis of 10 min data for the neutron flux, corrected for barometric pressure and data for local meteo-stations. The measured data permitted to study such effect at different observation levels and latitudes. The preliminary studies permits to observe correlation between rain flows and neutron flux in several cases.

  16. Bringing feedback and resilience of high-latitude ecosystems into the corporate boardroom.

    PubMed

    Whiteman, Gail; Forbes, Bruce C; Niemelä, Jari; Chapin, F Stuart

    2004-08-01

    This paper discusses the role of companies in high-latitude regions, which are conceptualized as socially and economically mediated ecosystems, and identifies a number of important social actors within the business environment. We present three examples of corporate activity at high latitudes and discuss a variety of common threads. Notably, we argue that business theory and practice needs to move beyond a narrow social or economic concept of organizational resilience and embrace the ecological resilience of high-latitude regions as a business management goal. We also suggest that regional ecosystem resilience needs to become a meaningful measure of sustainable corporate governance, one that corporate boards of directors can review and commit to. The paper concludes with a call for a detailed research agenda on the role of transnational and national companies within high-latitude regions. PMID:15387077

  17. On causes of the origin of systematic errors in latitude determination with the Moscow PZT.

    NASA Astrophysics Data System (ADS)

    Volchkov, A. A.; Gutsalo, G. A.

    Peculiarities of eye response during visual measurements of star positions on photographic plates are considered. It is shown that variations of the plate background density can be a source of systematic errors during latitude determinations with a PZT.

  18. A simplified indexing of F-region geophysical noise at low latitudes

    NASA Technical Reports Server (NTRS)

    Aggarwal, S.; Lakshmi, D. R.; Reddy, B. M.

    1979-01-01

    A simple method of deriving an F-region index that can warn the prediction users at low latitudes as to the specific months when they have to be more careful in using the long term predictions is described.

  19. Radiative Forcing of the Pinatubo Aerosol as a Function of Latitude and Time

    NASA Technical Reports Server (NTRS)

    Bergstrom, R. W.; Kinne, S.; Russell, P. B.; Bauman, J. J.; Minnis, P.

    1996-01-01

    We present calculations of the radiative forcing of the Mt. Pinatubo aerosols as a function of latitude and time after the eruption and compare the results with GOES satellite data. The results from the model indicate that the net effect of the aerosol was to cool the earth-atmosphere system with the most significant radiative effect in the tropics (corresponding to the location of the tropical stratospheric reservoir) and at latitudes greater than 60 deg. The high-latitude maximum is a combined effect of the high-latitude peak in optical depth (Trepte et al 1994) and the large solar zenith angles. The comparison of the predicted and measured net flux shows relatively good agreement, with the model consistently under predicting the cooling effect of the aerosol.

  20. A model of diurnally forced vertical current structure near 30° latitude

    NASA Astrophysics Data System (ADS)

    Craig, Peter D.

    1989-11-01

    At 30° latitude, the inertial frequency is equal to the frequency of the diurnal tide, or diurnal winds such as a sea breeze. The extension of Ekman's (1905, Arkiv foer Matematik, Astronomi och Fysik, 2, 11) theory to incorporate oscillatory forcing indicates that at the latitude where the inertial and forcing frequencies are the same, the sense of rotation of the current profile with depth will change. The coastal-ocean model of BATTISTI and CLARKE (1982, Journal of Physical Oceanography, 12, 8-16) is extended to include cross-shore wind stress and a constant eddy viscosity model of vertical current structure. The model is used to demonstrate the latitude-dependence of the tidally and wind-forced current structure near 30° latitude. The results are best interpreted in a fixed reference frame, rather than the rotating f-plane.

  1. THE LATITUDE DISTRIBUTION OF SMALL-SCALE MAGNETIC ELEMENTS IN SOLAR CYCLE 23

    SciTech Connect

    Jin, C. L.; Wang, J. X. E-mail: wangjx@nao.cas.cn

    2012-01-20

    With the unique data set from full-disk observations provided by Michelson Doppler Imager on board the Solar and Heliospheric Observatory in the interval embodying solar cycle 23, we have found that the cyclic variations of numbers and total flux of these small-scale magnetic elements covering fluxes of (2.9-32.0) Multiplication-Sign 10{sup 18} Mx and (4.27-38.01) Multiplication-Sign 10{sup 19} Mx show anticorrelation and correlation with sunspots, respectively. In this study, the time-latitude distributions of these anticorrelated and correlated elements are analyzed. The following results are disclosed: (1) for the correlated elements, the cyclic variations of the total flux in low-latitude and middle-latitude regions show a longer duration of cyclic maximum phase than that of an active region (AR) in the corresponding latitude region; the total flux of these elements shows the accordant south-north asymmetry with that of AR; the time-latitude distribution of their number displays a similar butterfly diagram but with a latitude distribution that is twice as wide as that of sunspots. (2) For the anticorrelated elements, the time-latitude distribution of number shows a solar cycle variation different from the sunspot butterfly diagram; in each latitude, the distribution of anticorrelated elements always shows the anticorrelated variation with that of sunspots; during solar cycle 23, the average speed of the peak latitudinal migration for anticorrelated elements reaches 7.5 deg year{sup -1}, almost three times that for sunspots. These results seem to imply that the correlated elements are the debris of decayed sunspots, and the anticorrelated elements have a different source but are affected or modulated by sunspot magnetic field.

  2. Altitude and latitude variations in avionics SEU and atmospheric neutron flux

    SciTech Connect

    Normand, E.; Baker, T.J. )

    1993-12-01

    The direct cause of single event upsets in SRAMs at aircraft altitudes by the atmospheric neutrons has previously been documented. The variation of the in-flight SEU rate with latitude is demonstrated by new data over a wide range of geographical locations. New measurements and models of the atmospheric neutron flux are also evaluated to characterize its variation with altitude, latitude and solar activity.

  3. Latitudinal TEC gradients over polar ionosphere using high latitude GPS measurements

    NASA Astrophysics Data System (ADS)

    Shagimuratov, Irk; Cherniak, Iurii; Zakharenkova, Irina; Tepenitsyna, Nadezhda; Yakimova, Galina; Ephishov, I. I.

    The GPS observations of Greenland network were used to analyze the latitudinal variations of TEC at the high-latitudes ionosphere. This network provides unique opportunity to monitor TEC variability in polar ionosphere on a regular base. GPS stations are arranged along the latitude over the range 60-83°N (65°-87° Corrected Geomagnetic Latitude) near of 30°-40° longitudes. More than 20 GPS stations are located closely with one another along latitude. The distance between stations is about 1°-2°.Such spatial resolution provides the possibility to analyze the detailed structure of latitudinal TEC profiles. The standard procedure of processing GPS observations was used for TEC estimation. On this base it was obtained the diurnal TEC variations over all Greenland stations. The TEC data is used to form latitudinal profiles (TEC section) covered subauroral, auroral and polar ionosphere. In the report the observations of TEC for quiet and disturbed ionosphere during several geomagnetic storms occurred in September 2011 are presented. During quiet conditions in the night-time TEC profiles demonstrated invariable values about of 4-6 TECU in latitudinal region of 60°-75°N; then it presented THE increase towards the higher latitude and reached the value of 10 TECU near 80°N. The daytime profiles revealed TEC decrease toward high latitude in keeping with 0.8 TECU/degree. During storm the structure of latitudinal TEC profiles was essentially changed with agreement to the development of geomagnetic storm. The positive effect was observed at subauroral and auroral latitudes, negative effect was prevailed at the polar region. During the night time the ionospheric trough can be observed. In the report features of the behavior of latitudinal profiles at high-latitude ionosphere for September 2011 events were discussed.

  4. Higher latitude and lower solar radiation influence on anaphylaxis in Chilean children

    PubMed Central

    Hoyos-Bachiloglu, Rodrigo; Morales, Pamela S.; Cerda, Jaime; Talesnik, Eduardo; González, Gilberto; Camargo, Carlos A.; Borzutzky, Arturo

    2014-01-01

    Background Recent studies suggest an association between higher latitude, a proxy of vitamin D (VD) status, and allergic diseases. Chile provides an ideal setting to study this association due to its latitude span and high rates of VD deficiency in southern regions. The aim of this study is to explore the associations of latitude and solar radiation with anaphylaxis admission rates. Methods We reviewed anaphylaxis admissions in Chile’s hospital discharge database between 2001 and 2010 and investigated associations with latitude and solar radiation. Results 2316 anaphylaxis admissions were registered. Median age of patients was 41 years; 53% were female. National anaphylaxis admission rate was 1.41 per 100,000 persons per year. We observed a strong north-south increasing gradient of anaphylaxis admissions (β 0.04, P=0.01), with increasing rates south of latitude 34°S. A significant association was also observed between solar radiation and anaphylaxis admissions (β −0.11, P=0.009). Latitude was associated with food-induced (β 0.05, P=0.02), but not drug-induced (β −0.002, P=0.27), anaphylaxis. The association between latitude and food-induced anaphylaxis was significant in children (β 0.01, P=0.006), but not adults (β 0.003, P=0.16). Anaphylaxis admissions were not associated with regional sociodemographic factors like poverty, rurality, educational level, ethnicity, or physician density. Conclusions Anaphylaxis admission rates in Chile are highest at higher latitudes and lower solar radiation, used as proxies of VD status. The associations appear driven by food-induced anaphylaxis. Our data support a possible role of VD deficiency as an etiological factor in the high anaphylaxis admission rates found in southern Chile. PMID:24628618

  5. Far-ultraviolet studies. VII - The spectrum and latitude dependence of the local interstellar radiation field

    NASA Technical Reports Server (NTRS)

    Henry, R. C.; Anderson, R. C.; Fastie, W. G.

    1980-01-01

    A direct measurement has been made of the spectrum (1180-1680 A) and Gould-latitude dependence of the local interstellar radiation field, over about one-third of the sky. The result is corrected to give expected values for the entire sky. The average local 1180-1680 A energy density is 5.8 x 10 to the -17th ergs/cu cm A. The surface brightness falls off toward high latitudes much more steeply than published models predict.

  6. The Latitude Distribution of Small-scale Magnetic Elements in Solar Cycle 23

    NASA Astrophysics Data System (ADS)

    Jin, C. L.; Wang, J. X.

    2012-01-01

    With the unique data set from full-disk observations provided by Michelson Doppler Imager on board the Solar and Heliospheric Observatory in the interval embodying solar cycle 23, we have found that the cyclic variations of numbers and total flux of these small-scale magnetic elements covering fluxes of (2.9-32.0) × 1018 Mx and (4.27-38.01) × 1019 Mx show anticorrelation and correlation with sunspots, respectively. In this study, the time-latitude distributions of these anticorrelated and correlated elements are analyzed. The following results are disclosed: (1) for the correlated elements, the cyclic variations of the total flux in low-latitude and middle-latitude regions show a longer duration of cyclic maximum phase than that of an active region (AR) in the corresponding latitude region; the total flux of these elements shows the accordant south-north asymmetry with that of AR; the time-latitude distribution of their number displays a similar butterfly diagram but with a latitude distribution that is twice as wide as that of sunspots. (2) For the anticorrelated elements, the time-latitude distribution of number shows a solar cycle variation different from the sunspot butterfly diagram; in each latitude, the distribution of anticorrelated elements always shows the anticorrelated variation with that of sunspots; during solar cycle 23, the average speed of the peak latitudinal migration for anticorrelated elements reaches 7.5 deg year-1, almost three times that for sunspots. These results seem to imply that the correlated elements are the debris of decayed sunspots, and the anticorrelated elements have a different source but are affected or modulated by sunspot magnetic field.

  7. Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

    NASA Astrophysics Data System (ADS)

    Grocott, A.; Wild, J. A.; Milan, S. E.; Yeoman, T. K.

    2009-02-01

    Using data from the Super Dual Auroral Radar Network (SuperDARN) we investigate the ionospheric convection response to magnetospheric substorms. Substorms were identified using the Far Ultraviolet (FUV) instrument on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, and were then binned according to the magnetic latitude of their onset. A superposed epoch analysis of the ionospheric convection patterns for each onset-latitude bin was then performed using radar data for the interval 60 min before onset to 90 min after. It is found that lower onset-latitude substorms are associated with generally more enhanced convection than the higher latitude substorms, although they suffer from a significant localised reduction of the flow in the midnight sector during the expansion phase. Higher-latitude substorms are associated with a significant and rapid increase in the nightside convection following substorm onset, with all onset-latitude bins showing an enhancement over onset values by ~60 min into the expansion phase. A rudimentary inspection of the concurrent auroral evolution suggests that the duration of the flow reduction following substorm onset is dependent on the strength and duration of the expansion phase aurora and its associated conductivity enhancement.

  8. The effect of space weather on human heart diseases in subauroral latitudes

    NASA Astrophysics Data System (ADS)

    Samsonov, S. N.; Kleimenova, N. G.; Kozyreva, O. V.; Petrova, P. G.

    2014-12-01

    In this work the relationship between emergency medical calls for myocardial infarction in Yakutsk (subauroral geomagnetic latitudes) and parameters of the space weather near maximum (1992) and minimum (1998) geomagnetic activity is studied. The comparison of the seasonal behavior of the number of calls with the simultaneous seasonal behavior of deaths from myocardial infarctions at low latitudes (Bulgaria) exhibited significant differences. Namely, in Bulgaria, the maximum and minimum of infarctions were observed in winter and in summer, respectively; in Yakutsk, several observed maximums coincided with the sharp and considerable increase in planetary geomagnetic activity. An analysis of experimental results made it possible to suppose that, in subauroral latitudes, unlike low latitudes, a major role in the increase in the number of infarctions is played by the increase in geomagnetic activity, namely, by the appearance of night magnetospheric substorms, which are also observed in subauroral latitudes in magnetically disturbed times. Substorms are always accompanied by irregular geomagnetic Pi1 pulsations with periods of 0.5-3 Hz. These pulsations can be biotropic, like stable quasi-sinusoidal geomagnetic Pc1 pulsations in middle and low latitudes.

  9. How much does latitude modify temperature-mortality relationship in 13 eastern US cities?

    PubMed

    Xiao, Jianpeng; Peng, Ji; Zhang, Yonghui; Liu, Tao; Rutherford, Shannon; Lin, Hualiang; Qian, Zhengmin; Huang, Cunrui; Luo, Yuan; Zeng, Weilin; Chu, Cordia; Ma, Wenjun

    2015-03-01

    Although several studies have documented that latitude might be an effect modifier of the association between temperature and mortality, little is known about how much latitude modifies the temperature-mortality relationship. In this study, we examined this research question using a distributed lag non-linear model and meta-regression analysis based on data from 13 large cities of eastern US from the US National Morbidity, Mortality, and Air Pollution Study. We found that cold effects lasted about 1 month while hot effects were acute and short-term. Meta-regression analysis showed that latitude modified both the cold and hot effects with statistical significance. The cold effect decreased with the latitude increment, with -0.11 % change of mortality effect for 1° increment, while the hot effect increased with the latitude increment, with 0.18 % change of mortality effect for 1° increment. This finding indicates the importance of latitude on temperature-related mortality risk, which is helpful for city to develop localized effective adaptation strategy in the context of climate change. PMID:24880926

  10. Characteristics of the Afternoon E-region Plasma Density Irregularities in Middle Latitudes

    NASA Astrophysics Data System (ADS)

    Kwak, Y. S.; Yang, T. Y.; Kil, H.; Otsuka, Y.

    2014-12-01

    In middle latitudes, radar probing of E-region ionospheric electron density irregularities has been carried out for several decades. However, no the afternoon (i.e., from noon to pre-sunset time) E-region field-aligned irregularities (FAIs) in middle latitude have been reported yet. On the other hand, a 40.8 MHz VHF radar operated continuously since December 2009 at Daejeon (36.18°N, 127.14°E, 26.7°N dip latitude) in South Korea has often observed the E-region FAIs in the afternoon. In this presentation, therefore, we report firstly the afternoon observations of the mid-latitude E-region FAIs made by the Daejeon radar. We present the characteristics and statistical morphology of the mid-latitude afternoon E-region FAIs based on the continuous and long-term radar observations. And also, to investigate the afternoon E-region FAIs - Sporadic E (Es) relationship, the FAIs have been also compared with Es parameters based on observations made from an ionosonde located at Icheon (37.14°N, 127.54°E, 27.7°N dip latitude), which is 100 km north of Daejeon.

  11. Water vapour variability in the high-latitude upper troposphere - Part 2: Impact of volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Sioris, Christopher E.; Zou, Jason; McElroy, C. Thomas; Boone, Chris D.; Sheese, Patrick E.; Bernath, Peter F.

    2016-02-01

    The impact of volcanic eruptions on water vapour in the high-latitude upper troposphere is studied using deseasonalized time series based on observations by the Atmospheric Chemistry Experiment (ACE) water vapour sensors, namely MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) and the Fourier Transform Spectrometer (ACE-FTS). The two eruptions with the greatest impact on the high-latitude upper troposphere during the time frame of this satellite-based remote sensing mission are chosen. The Puyehue-Cordón Caulle volcanic eruption in June 2011 was the most explosive in the past 24 years and is shown to be able to account for the observed (50 ± 12) % increase in water vapour in the southern high-latitude upper troposphere in July 2011 after a minor adjustment for the simultaneous influence of the Antarctic oscillation. Eyjafjallajökull erupted in the spring of 2010, increasing water vapour in the upper troposphere at northern high latitudes significantly for a period of ˜ 1 month. These findings imply that extratropical volcanic eruptions in windy environments can lead to significant perturbations to high-latitude upper tropospheric humidity mostly due to entrainment of lower tropospheric moisture by wind-blown plumes. The Puyehue-Cordón Caulle eruption must be taken into account to properly determine the magnitude of the trend in southern high-latitude upper tropospheric water vapour over the last decade.

  12. Intermediate time error growth and predictability: tropics versus mid-latitudes

    NASA Astrophysics Data System (ADS)

    Straus, David M.; Paolino, Dan

    2009-10-01

    The evolution of identical twin errors from an atmospheric general circulation model is studied in the linear range (small errors) through intermediate times and the approach to saturation. Between forecast day 1 and 7, the normalized error variance in the tropics is similar to that at higher latitudes. After that, tropical errors grow more slowly. The predictability time τ taken for tropical errors to reach half their saturation values is larger than that for mid-latitudes, especially for the planetary waves, thus implying greater potential predictability in the tropics. The discrepancy between mid-latitude and tropical τ is more pronounced at 850 hPa than at 200 hPa, is largest for the planetary waves, and is more pronounced for errors arising from wave phase differences (than from wave amplitude differences). The spectra of the error in 200 hPa zonal wind show that for forecast times up to about 5 d, the tropical error peaks at much shorter scales than the mid-latitude errors, but that subsequently tropical and mid-latitude error spectra look increasingly similar. The difference between upper and lower level tropical τ may be due to the greater influence of mid-latitudes at the upper levels.

  13. The OH morphology during Solar Proton Events - footprints of the cutoff latitudes

    NASA Astrophysics Data System (ADS)

    Nesse Tyssøy, Hilde; Stadsnes, Johan; Zawedde, Annet Eva

    2015-04-01

    To accurately quantify the effect of Solar Proton Events (SPEs) on the atmosphere requires a good estimate of the particle energy deposition in the middle atmosphere (60-100 km) and how the energy is distributed globally. Protons in the energy range 1-20 MeV, depositing their energy in the middle atmosphere, are subject to more complex dynamics with strong day-night asymmetries compared to higher energy particles. By using measurements from the Medium Energy Proton and Electron Detector (MEPED) on all available Polar Orbit Environment Satellites (POES), we show that in the main phase of geomagnetic storms the dayside cutoff latitudes are pushed poleward, while the nightside cutoff latitudes have the opposite response, resulting in strong day-night asymmetries in the energy deposition. In 2005 the polar orbiting sun-synchronous satellites, NOAA/POES-16 (N16) and Aura, covered approximately the same local times. In other words, the particle fluxes measured by MEPED/N16 deposited their energy close in both time and space to the OH and ozone measurements performed by MLS/Aura. The January 2005 SPE caused a clear increase in the OH density above 56o CGM latitude. We investigate to what extent the lower latitude boundary of the increased OH and ozone density fits the proton cutoff latitude. Previous studies have investigated if OH can be used as an indicator of solar proton precipitation in the high latitude atmosphere. OH data were reduced to daily means and/or averaged over a latitude interval. In this study we take advantage of the fact that N16 and Aura are close in both time and space and evaluate the measurements on shorter time scales. We investigate the correlation and evaluate the production efficiency and lifetime of OH produced by energetic proton precipitation at different altitudes between 60 and 80 km.

  14. Influence of high latitude ice cover on the marine Intertropical Convergence Zone

    NASA Astrophysics Data System (ADS)

    Chiang, John C. H.; Bitz, Cecilia M.

    2005-10-01

    We investigate the causes for a strong high latitude imposed ice (land or sea) influence on the marine Intertropical Convergence Zone (ITCZ) in the Community Climate Model version 3 coupled to a 50-m slab ocean. The marine ITCZ in all the ocean basins shift meridionally away from the hemisphere with an imposed added ice cover, altering the global Hadley circulation with an increased tropical subsidence in the hemisphere with imposed ice and uplift in the other. The effect appears to be independent of the longitudinal position of imposed ice. The anomalous ice induces a rapid cooling and drying of the air and surface over the entire high- and midlatitudes; subsequent progression of cold anomalies occurs in the Pacific and Atlantic northeasterly trade regions, where a wind-evaporation-sea surface temperature (SST) feedback initiates progression of a cold SST ‘front’ towards the ITCZ latitudes. Once the cooler SST reaches the ITCZ latitude, the ITCZ shifts southwards, aided by positive feedbacks associated with the displacement. The ITCZ displacement transports moisture away from the colder and drier hemisphere into the other hemisphere, resulting in a pronounced hemispheric asymmetric response in anomalous specific humidity; we speculate that the atmospheric humidity plays a central role in the hemispheric asymmetric nature of the climate response to high latitude ice cover anomalies. From an energy balance viewpoint, the increased outgoing radiative flux at the latitudes of the imposed ice is compensated by an increased radiative energy flux at the tropical latitudes occupied by the displaced ITCZ, and subsequently transported by the altered Hadley and eddy circulations to the imposed ice latitudes. The situation investigated here may be applicable to past climates like the Last Glacial Maximum where hemispheric asymmetric changes to ice cover occurred. Major caveats to the conclusions drawn include omission of interactive sea ice physics and ocean dynamical

  15. The large volcanic eruptions at different latitude bands and patterns of winter temperature changes over China

    NASA Astrophysics Data System (ADS)

    Hao, Zhixin; Sun, Di

    2016-04-01

    Based on the chronology of 29 large volcanic eruptions events (Volcanic Explosivity Index≥4) since 1951 and gridded temperature dataset from China Meteorological Data Sharing Service System, we identified the patterns of winter temperature changes over China after the large volcanic eruptions, comparing with the mean temperature within the five years before, then we analyzed the related dynamic mechanisms of different patterns by NCEP reanalysis data and model output data from Community Earth System Model (CESM). The results showed that the winter temperature decreased more than 1°C in East China after volcanic eruptions on middle-lower latitudes and equatorial bands. After volcanic eruptions on different latitudes, the temperature spatial patterns were summarized as two types, which included that temperature was cooling centered on Northeast and warming in Tibets, and its opposite pattern. The first pattern was usually detected after tropical volcanic eruptions in spring/summer and it also appeared after volcanic eruptions on high latitudes in spring/autumn. After middle-lower latitude volcanic eruptions, the variation of geopotential height on 500hPa showed that the positive anomaly was existed at the East of Ural mountain, which caused the temperature decreased in Northwest , Central East and Southeast when east asian trough was intensified. After high latitudes volcanic eruptions, the zonal circulation was more obvious at middle latitudes, the cold air was not easy to transport,therefore winter temperature increased in China except for the Yangtze River Basin. The result of full forcing experiments by CESM showed that temperature decreased at most regions after large volcanic eruptions on equatorial /high bands, and troughs and wedges were developed on 500 hPa. The variation of geopotential height was nearly reversed after volcanic eruptions on high latitudes, only the temperature of Tibetan Plateau decreased. But how the variation of geopotential height

  16. The large volcanic eruptions at different latitude bands and patterns of winter temperature changes over China

    NASA Astrophysics Data System (ADS)

    Sun, D.; Hao, Z.; Zheng, J.

    2015-12-01

    Based on the chronology of 29 large volcanic eruptions events (Volcanic Explosivity Index≥4) since 1951 and gridded temperature dataset from China Meteorological Data Sharing Service System, we identified the patterns of winter temperature changes over China after the large volcanic eruptions, comparing with the mean temperature within the five years before, then we analyzed the related dynamic mechanisms of different patterns by NCEP reanalysis data and model output data from Community Earth System Model (CESM). The results showed that the winter temperature decreased more than 1°C in East China after volcanic eruptions on middle-lower latitudes and equatorial bands. After volcanic eruptions on different latitudes, the temperature spatial patterns were summarized as two types, which included that temperature was cooling centered on Northeast and warming in Tibets, and its opposite pattern. The first pattern was usually detected after equatorial volcanic eruptions in spring/summer and it also appeared after volcanic eruptions on high latitudes in spring/autumn. After middle-lower latitude volcanic eruptions, the variation of geopotential height on 500hPa showed that the positive anomaly was existed at the East of Ural mountain, which caused the temperature decreased in Northwest , Central East and Southeast when east asian trough was intensified. After high latitudes volcanic eruptions, the zonal circulation was more obvious at middle latitudes, the cold air was not easy to transport therefore winter temperature increased in China except for the Yangtze River Basin. The result of full forcing experiments by CESM showed that temperature decreased at most regions after large volcanic eruptions on equatorial /high bands, and troughs and wedges were developed on 500 hPa. The variation of geopotential height was nearly reversed after volcanic eruptions on high latitudes, only the temperature of Tibetan Plateau decreased. But how the variation of geopotential height

  17. Observations of ionospheric convection from the Wallops SuperDARN radar at middle latitudes

    NASA Astrophysics Data System (ADS)

    Baker, J. B. H.; Greenwald, R. A.; Ruohoniemi, J. M.; Oksavik, K.; Gjerloev, J. W.; Paxton, L. J.; Hairston, M. R.

    2007-01-01

    During geomagnetic storms the ability of the Super Dual Auroral Radar Network (SuperDARN) to measure ionospheric convection becomes limited when the radars suffer from absorption and the auroral disturbance expands equatorward of the radar sites. To overcome these shortcomings, it was decided to construct a SuperDARN radar at middle latitudes on the grounds of the NASA Wallops Flight Facility. This paper presents the first comprehensive analysis of Doppler measurements from the Wallops radar, which commenced operations in May 2005. Wallops measurements are compared with the Goose Bay radar during the onset of a geomagnetic storm on 31 August 2005: Goose Bay measured the onset of geomagnetic activity at high latitude while Wallops monitored the expansion of convection to middle latitudes. Average convection patterns binned by the Kp geomagnetic index are also presented. During weak-moderate geomagnetic activity (Kp ≤ 3) the Wallops radar observes ionospheric irregularities between 50° and 60° magnetic latitude drifting westward across much of the nightside. When these measurements are incorporated into the calculation of an average SuperDARN convection pattern, the streamlines of polar cap outflow on the nightside become kinked in a manner reminiscent of the Harang discontinuity. This morphology arises quite naturally when the two-cell convection at high latitudes merges with the prevailing westward convection at middle latitudes. During increased geomagnetic activity (Kp ≥ 3), Wallops is able to measure the expansion of auroral electric fields to middle latitudes and the average SuperDARN cross-polar cap potential is increased by 25%.

  18. Theoretically modeling the low-latitude, ionospheric response to large geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Anderson, D.; Anghel, A.; Araujo, E.; Eccles, V.; Valladares, C.; Lin, C.

    2006-10-01

    In the low-latitude, ionospheric F region, the primary transport mechanism that determines the electron and ion density distributions is the magnitude of the daytime, upward E × B drift velocity. During large geomagnetic storms, penetration of high-latitude electric fields to low latitudes can often produce daytime, vertical E × B drift velocities in excess of 50 m/s. Employing a recently developed technique, we can infer these daytime, upward E × B drift velocities from ground-based magnetometer observations at Jicamarca and Piura, Peru, as a function of local time (0700-1700 LT). We study the ionospheric response in the Peruvian longitude sector to these large upward drifts by theoretically calculating electron and ion densities as a function of altitude, latitude, and local time using the time-dependent Low-Latitude Ionospheric Sector (LLIONS) model. This is a single-sector ionosphere model capable of incorporating data-determined drivers, such as E × B drift velocities. For this study, we choose three large storms in 2003 (29 and 30 October and 20 November) when daytime E × B drift velocities approached or exceeded 50 m/s. Initial results indicate that the large, upward E × B drift velocities on 29 October produced equatorial anomaly crests in ionization at ±20° dip latitude rather than the usual ±16° dip latitude. We compare the theoretically calculated results with a variety of ground-based and satellite observations for these three periods and discuss the implications of these comparisons as they relate to the capabilities of current theoretical models and our ability to infer ionospheric drivers such as E × B drifts (Anderson et al., 2002).

  19. Viking magnetic and electric field observations of Pc 1 waves at high latitudes

    SciTech Connect

    Erlandson, R.E.; Zanetti, L.J.; Potemra, T.A. ); Block, L.P. ); Holmgren, G. )

    1990-05-01

    Magnetic and electric field fluctuations in the Pc 1 frequency range (0.2-5 Hz) have been observed by the polar-orbiting Viking satellite. The fluctuations, interpreted here as electromagnetic ion cyclotron (EMIC) waves, were observed during 21 of 450 orbits surveyed between 0900 and 1400 MLT, near 3 R{sub E} geocentric altitude, and at invariant latitudes from 59{degree} to 77{degree}. The frequency structure of the waves is investigated, using spectral analysis and by determining the distribution of the wave frequency as a function of invariant latitude. At invariant latitudes from 59{degree} to 72{degree}, EMIC waves were observed in the frequency range below the equatorial He{sup +} gyrofrequency, while from 70{degree} to 77{degree} invariant latitude, EMIC waves were observed in the frequency range above the equatorial He{sup +} gyrofrequency. This latitude structure of the wave frequency is discussed in terms of the linear growth rate dependence of the waves on the heavy ion density, ion anisotropy, and ion energy. The propagation characteristics of these waves were also investigated, using minimum variance analysis and polarization analysis, and by estimating the Poynting flux based on the observed magnetic and electric field. The waves had Poynting vectors directed downward toward Earth and reached magnitudes between 0.01 and 0.1 erg/cm{sup 2} s. The polarization of the waves was found to vary between linear, left-hand, and right-hand as a function of time or latitude. This variation is interpreted as the structure of spatially localized Pc 1 waves at high latitudes above the ionosphere.

  20. Relative Contributions of Heating and Momentum Forcing to High-Latitude Lower Thermospheric Winds

    NASA Astrophysics Data System (ADS)

    Kwak, Y. S.; Richmond, A. D.

    2015-12-01

    At high latitudes the thermospheric dynamics are gov­erned by various heat and momentum sources. Recently several modeling studies have been attempt­ed to understand the physical process that control the high-latitude lower thermospheric dynamics. Kwak and Richmond [2007] and Kwak et al. [2007] studied the momentum forcing bal­ance that are mainly responsible for maintaining the high-latitude lower thermospheric wind system by using the National Center for Atmospheric Research Thermo­sphere Ionosphere Electrodynamics General Circulation Model (NCAR TIE-GCM). Kwak and Richmond [2014] analyzed the divergence and vorticity of the high-latitude neutral wind field in the lower thermosphere during the south­ern summertime. In this study, we extend previous works by Kwak and Rich­mond [2007, 2014] and Kwak et al. [2007], which helped to better understand the physical processes maintaining thermospheric dynamics at high latitudes, and here perform a "term analysis of the potential vorticity equation" for the high-latitude neu­tral wind field in the lower thermosphere, on the basis of numerical simulations using the NCAR TIE-GCM. These analyses can provide insight into the relative strength of the heating and the momentum forcing responsible for driving rotational winds at the high-latitude lower thermosphere. The heating is the net heat including the heat transfer by downward molecular and eddy heat conduction, the absorption of solar ultraviolet (UV) and extreme ultraviolet (EUV) ra­diation, auroral heating by particles, Joule dissipation of ionospheric currents, release of chemical energy by the atomic oxygen recombination, and radiative CO2, NO and O infrared emissions. The momentum forcing is associated with the viscous force and the frictional drag force from convecting ions.

  1. Reversed energy-latitude dependence of ion precipitation boundary: observations and possible mechanisms

    NASA Astrophysics Data System (ADS)

    Liang, J.; Donovan, E.; Ni, B.; Angelopoulos, V.

    2013-12-01

    A previous survey by Donovan et al. [2003] revealed that there exist two typical patterns in terms of the energy-latitude dependence of the ion precipitation boundary. In one common pattern, the precipitation flux diminishes at higher (lower) latitudes for protons with lower (higher) energies. Correspondently, at a fixed latitude, the isotropic ratio, defined as the ratio between the precipitation flux and the trapped flux, tends to be higher (lower) for protons with higher (lower) energies. This pattern conforms to the scenario of the pitch-angle scattering of protons led by the field line curvature in the equatorial magnetosphere, which is well recognized as a major mechanism leading to the precipitation of plasma sheet protons. The second pattern, albeit less common than the first one, features distinctly 'reversed' energy-latitude dependences of the ion precipitation boundary, namely that, (a) the isotropic ratio diminishes at higher (lower) latitudes for protons with higher (lower) energies; (b) at a fixed latitude the isotropic ratio tends to be lower (higher) for protons with higher (lower) energies. Donovan et al. [2003] further noted that latter "reversed-type" events predominantly occur in midnight-morning MLT sectors, while their underlying mechanisms remain to be explored. In this study, we present detailed analyses of a few events with this 'reversed' energy-latitude dependence of the ion precipitation boundary, based upon joint observations from low-Earth-orbit satellites and THEMIS in-situ probes. We explore two potential mechanisms: the ion acceleration led by downward parallel electric field in the topside ionosphere, and the pitch-angle scattering of plasma sheet protons by electromagnetic ion cyclotron (EMIC) waves in the equatorial tail. Both mechanisms may act to enhance the precipitation fluxes of protons in energy range mainly between a few hundred eV and several keV; when they are operative in a region southward/earthward of the b2i boundary

  2. Weapon allometry varies with latitude in the New Zealand giraffe weevil.

    PubMed

    Painting, C J; Buckley, T R; Holwell, G I

    2014-12-01

    Animal body size commonly shows a relationship with latitude to the degree that this phenomenon is one of the few 'rules' discussed in evolutionary ecology: Bergmann's rule. Although exaggerated secondary sexual traits frequently exhibit interesting relationships with body size (allometries) and are expected to evolve rapidly in response to environmental variation, the way in which allometry might interact with latitude has not been addressed. We present data showing latitudinal variation in body size and weapon allometry for the New Zealand giraffe weevil (Lasiorhynchus barbicornis). Males display an extremely elongated rostrum used as a weapon during fights for access to females. Consistent with Bergmann's rule, mean body size increased with latitude. More interestingly, weapon allometry also varied with latitude, such that lower latitude populations exhibited steeper allometric slopes between weapon and body size. To our knowledge, this is the first study to document a latitudinal cline in weapon allometry and is therefore a novel contribution to the collective work on Bergmann's rule and secondary sexual trait variation. PMID:25303121

  3. Is plant migration restrained by available nitrogen supply in high latitudes?

    NASA Astrophysics Data System (ADS)

    Lee, E.; Schlosser, C. A.; Felzer, B.; Kicklighter, D.; Cronin, T.; Melillo, J.; Prinn, R. G.

    2008-12-01

    Recent studies suggest that growth and distribution of natural vegetation in high latitudes may be controlled by the amount of available nitrogen. Yet few studies have examined the role of available nitrogen on plant migration in response to anticipated climate change. We use a modeling approach to explore this issue. With a projected climate dataset (GFDL CM 2.0) from the IPCC AR4 archive, we first estimate net nitrogen mineralization values for natural plant functional types in high latitudes (north of 52N), using the Terrestrial Ecosystem Model (TEM). Previous work with TEM indicates that warming increases the rates of net nitrogen mineralization in high latitudes (e.g. 10 percent increase in boreal forests), which may help support a pattern of increased woodiness in northern systems such as boreal woodlands filling in with trees and tundra becoming more shrubby. Constrained with the available nitrogen for each vegetation type, a simple rule- based model, which describes the migration process and adopts processes of climatic tolerances of trees from the BIOME biogeography model, is used to generate a newly projected vegetation map for high latitudes. Our study emphasizes the significance of the role of nitrogen in the high latitude plant distribution. We also investigate the climatic consequences of the changing albedo, resulting from shifts in the vegetation distribution.

  4. Coupling of the high-latitude thermospheric wind with magnetospheric drivers

    NASA Astrophysics Data System (ADS)

    Förster, Matthias; Haaland, Stein E.; Doornbos, Eelco

    The high-latitude thermospheric wind is strongly influenced by varying solar wind conditions via electromagnetic coupling with the magnetosphere. In this study we present a statistical study of both magnetospheric plasma convection measured by the EDI instruments on board Cluster and neutral wind measurements obtained from cross-track acceleration measurements of the CHAMP satellite at high geomagnetic latitudes. These data sets are analyzed in their dependence on the strength and orientation of the interplanetary magnetic field (IMF). The spatially distributed Cluster/EDI measurements are mapped to a common reference level at ionospheric F-region heights in a magnetic latitude/MLT grid at both hemispheres. The cross-track wind component observations of CHAMP are similarly sampled and binned into the high-latitude geomagnetic grid for the Northern and Southern hemisphere separately. Thus, we obtained both regular thermospheric wind and plasma drift patterns in their dependence on the different solar wind IMF conditions. Vorticity analyses of these 2D vector patterns reveal the close relation between the ionospheric plasma convection and neutral wind via collisional coupling between the ions and neutrals (ion drag). The magnetospheric driving processes are mediated via field-aligned current (FAC) re-sponses to magnetic reconnection in terms of the vorticity of the ionospheric plasma convection. Similar pattern can be seen in the high-latitude neutral wind vorticity and its IMF dependency. FAC closure in the ionosphere further acts via Joule heating as an important energy source of the whole magnetosphere-ionosphere-thermosphere system.

  5. Decelerated Magnetoshealth Plasma Flow at High Latitudes Behind the Cusp Region: Interball Tail Observations

    NASA Technical Reports Server (NTRS)

    Avanov, L. A.; Chandler, M. O.; Smirnov, V. N.; Vaisberg, O. L.

    2002-01-01

    On May 25, 1996 the Interball Tail spacecraft was moving through the northern hemisphere of the high-latitude magnetosphere on its outbound trajectory. It successively crossed lobe field lines followed by the high latitude magnetopause, then entering the magnetoshealth proper near the cusp region covering magnetic local time from 8h20m to 9h30m at magnetic latitudes of about 770. IMF observed by WIND was northward during the time interval of interest and favorable for reconnection at high latitude magnetopause. The well-defined De Hoffmann Teller frame and stress balance indicate that the magnetopause was a rotational discontinuity with ongoing reconnection. After the magnetopause crossing, the spacecraft observed decelerated magnetoshealth flow in the sub-Alvinic regime. A gradually increasing of the flow velocity is observed and the plasma flow regime changed from sub-Alfvnic through Alfinic to super-Alfvnic one. We explain these results by direct passing of the Interball Tail through the secondary stagnation point, which has been predicted by theoretical and semiempirical models of the high latitude magnetopause.

  6. Large-scale energy transformations in the high latitudes of the Northern Hemisphere

    NASA Technical Reports Server (NTRS)

    Kung, E. C.; Masters, S. E.; Corte-Real, J. A. M.

    1983-01-01

    The kinetic energy balance and kinetic energy sources are studied for high latitudes north of 55 deg N with twice daily upper air observations during a seven-year period from 1973 to 1979. Energy variables are presented for 5 deg latitudinal zones from 55 to 75 deg N and for the polar cap north of 75 deg N. Spatial distributions of important energy variables are also presented. The upper level maximum of the cross-isobaric generation in high latitudes is observed in th lower stratosphere above the tropopause level in the winter and becomes insignificant during the summer. The flux convergence of potential energy from the source in lower latitudes is identified as the single major source for kinetic energy in higher latitudes. The contribution of the baroclinic conversion is minor. Examination during the First GARP Global Experiment winter indicates that the cold air outbreaks of the Asian winter monsoon are associated with noticeable changes in the hemispherical distributions of the fields of vertical motion and energetics in the high latitudes.

  7. Syntheses of wetland methane emissions at high latitudes: exploring sensitivities to climate change and permafrost thaw.

    NASA Astrophysics Data System (ADS)

    Olefeldt, D.; Turetsky, M. R.

    2014-12-01

    Climate change and associated permafrost thaw has the potential to increase methane emissions from high latitude wetlands, thus amplifying human-caused climate change. Methane monitoring at high latitude wetlands have been carried out since the 1970s, and at this time there are published data from a large number of sites and some individual sites have data that span more than a decade. By synthesizing data both across and within sites it is possible to improve our understanding of environmental and physical controls on methane emissions. It is clear from comparing mean growing season methane emissions across sites that site wetness, soil temperature and vegetation composition have strong and interacting effects. At individual sites it is also evident that soil temperatures and wetness co-vary at inter-annual scales as a result of physical processes, with compounding influences on methane emissions. Further the presence of certain sedge species, often found in fens at high latitudes strongly influence sensitivities to soil temperature and wetness. Shifts in functional relationships as related to ecosystem structure is central for methane emissions at high latitude wetlands, given the hydrological and ecological changes that occur with permafrost thaw and thermokarst landform development. Hence, in order to more accurately project future methane emissions from high latitudes at a pan-arctic scale, it is necessary to include a spatial representation of thermokarst development as well as ecosystem-appropriate functional relationships between emissions and environmental variables.

  8. Mid-Latitude Ionospheric Disturbances Due to Geomagnetic Storms at ISS Altitudes

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Willis, Emily M.; Parker, Linda Neergaard

    2014-01-01

    Spacecraft charging of the International Space Station (ISS) is dominated by the interaction of the high voltage US solar arrays with the F2-region ionospheric plasma environment. We are working to fully understand the charging behavior of the ISS solar arrays and determine how well future charging behavior can be predicted from in-situ measurements of plasma density and temperature. One aspect of this work is a need to characterize the magnitude of electron density and temperature variations that may be encountered at ISS orbital altitudes (approximately 400 km), the latitudes over which they occur, and the time periods for which the disturbances persist. We will present preliminary results from a study of ionospheric disturbances in the "mid-latitude" region defined as the approximately 30 - 60 degree extra-equatorial magnetic latitudes sampled by ISS. The study is focused on geomagnetic storm periods because they are well known drivers for disturbances in the high-latitude and mid-latitude ionospheric plasma. Changes in the F2 peak electron density obtained from ground based ionosonde records are compared to in-situ electron density and temperature measurements from the CHAMP and ISS spacecraft at altitudes near, or above, the F2 peak. Results from a number of geomagnetic storms will be presented and their potential impact on ISS charging will be discussed.

  9. A statistical study on characteristics of high latitude Pi 3 pulsations

    NASA Technical Reports Server (NTRS)

    Suzuki, A.; Kim, J. S.; Sugiura, M.; Nagano, H.

    1981-01-01

    The latitude and magnetic local time distributions of Pi 3 pulsations relative to polarization and the position of maximum intensity are presented using data from the high-latitude North American International Magnetospheric Study magnetometer network. These distributions are compared with those of Pc 5 and Pi 2 pulsations. The locus of Pi 3 maximum amplitude and the corresponding curve for Pc 5 are similar in general shape, but the former is located at considerably lower geomagnetic latitudes than the latter. For Pi 2 pulsations, the latitude of maximum amplitude is found to agree well with the auroral oval, whereas the locus of Pi 3 amplitude maximum deviates from the auroral oval appreciably in the dawn and dusk regions and is near the poleward border of the auroral oval in the premidnight region where the equatorward boundary of the oval is lowest in latitude. It is concluded that dayside Pi 3 pulsations may have a different generation mechanism from that for nightside Pi 3 events.

  10. Solar activity and human health at middle and low geomagnetic latitudes in Central America

    NASA Astrophysics Data System (ADS)

    Mendoza, Blanca; Sánchez de La Peña, Salvador

    2010-08-01

    The study of the possible effect of solar variability on living organisms is one of the most controversial issues of present day science. It has been firstly and mainly carried on high latitudes, while at middle and low latitudes this study is rare. In the present review we focused on the work developed at middle and low geomagnetic latitudes of America. At these geomagnetic latitudes the groups consistently dedicated to this issue are mainly two, one in Cuba and the other in Mexico. The Cuban and Mexican studies show that at such latitudes there are biological consequences to the solar/geomagnetic activity, coinciding in four points: (1) the male population behave differently from the female population, (2) the most vulnerable age group to geomagnetic perturbations is that of ⩾65 years old, (3) there is a tendency for myocardial infarctions (death or occurrence) to increase one day after a geomagnetic Ap index large value or during the day of the associated Forbush decrease, and (4) the myocardial infarctions (death or occurrence) increase as the geomagnetic perturbation increases. Additionally, the Cuban group found seasonal periodicities from their data, and also that increases of female myocardial infarctions occurred before and after the day of the geomagnetic disturbance. The Mexican group found that the male sex is more vulnerable to geomagnetic perturbations and that the myocardial infarction deaths present the conspicuous cycle of ˜7 days.

  11. Low-Latitude Auroras: The Magnetic Storm of 14-15 May 1921

    NASA Technical Reports Server (NTRS)

    Silverman, S. M.; Cliver, E. W.

    2001-01-01

    We review solar geophysical data relating to the great magnetic storm of 14-15 May 1921, with emphasis on observations of the low-latitude visual aurora. From the reports we have gathered for this event the lowest geomagnetic latitude of definite overhead aurora (coronal form) was 40 deg and the lowest geomagnetic latitude from which auroras were observed on the poleward horizon in the northern hemisphere was 30 deg. For comparison, corresponding overhead/low-latitude values of 48 deg/32 deg and 41 deg/20 deg were reported for the great auroras on 28-29 August and 1-2 September 1859, respectively. However for the 1921 event, there is a report of aurora from Apia, Samoa, in the southern hemisphere, within 13 deg of the geomagnetic equator. This report by professional observers appears to be credible, based on the aurora description and timing, but is puzzling because of the discrepancy with the lowest latitude of observation in the northern hemisphere and the great implied aurora height (approximately 2000 km, assuming overhead aurora at Auckland, New Zealand). We discuss various possibilities that might account for this observation.

  12. Theoretically Modeling the Ionospheric Response at Low Latitudes to the Great Storms in October, 2003

    NASA Astrophysics Data System (ADS)

    Anderson, D. N.; Anghel, A.; Eccles, V.; Valladares, C.; Chau, J.; Veliz, O.

    2004-05-01

    In the low latitude, ionospheric F region, the primary transport mechanism that determines the electron and ion density distributions is the magnitude of the daytime, upward ExB drift velocity. During the geomagnetic storms on Oct. 29 and 30, 2003, we have inferred these upward ExB drift velocities from ground-based magnetometer observations at Jicamarca and Piura, Peru as a function of local time (0700 - 1700LT). On both days these ExB drifts exceeded 80 m/sec which is about four times greater than the normal, quiet time value of 20 m/sec. We study the ionospheric response in the Peruvian longitude sector to these large upward drifts by theoretically-calculating electron and ion densities as a function of altitude, latitude and local time using the time-dependent Low-Latitude Ionospheric Sector model (LLIONS). This is a single sector ionosphere model capable of incorporating data-determined drivers. Initial results indicate that the large, upward ExB drift velocities on Oct. 29 produce equatorial anomaly crests in ionization at +/- 22° dip latitude rather than the usual +/- 16° dip latitude. We compare the theoretically-calculated results with a variety of ground-based and satellite observations for Oct. 28, 29, 30 and 31 and discuss the implications of these comparisons as they relate to the capabilities of current theoretical models and our ability to infer ionospheric drivers such as ExB drifts.

  13. Spectroscopic Detection of COCLF in the Tropical and Mid-Latitude Lower Stratosphere

    NASA Technical Reports Server (NTRS)

    Rinsland, Curtis P.; Nassar, Ray; Boone, Chris D.; Bernath, Peter; Chiou, Linda; Weisenstein, Debra K.; Mahieu, Emmanuel; Zander, Rodolphe

    2006-01-01

    We report retrievals of COClF (carbonyl chlorofluoride) based on atmospheric chemistry experiment (ACE) solar occultation spectra recorded at tropical and mid-latitudes during 2004-2005. The COClF molecule is a temporary reservoir of both chlorine and fluorine and has not been measured previously by remote sensing. A maximum COClF mixing ratio of 99.7+/- 48.0 pptv per unit volume, (10 (exp -12)I sigma) is measured at 28km for tropical and subtropical occultations (latitudes below 20 degrees in both hemispheres) with lower mixing ratios at both higher and lower altitudes. Northern hemisphere mid-latitude mixing ratios (30-50 degrees N) resulted in an average profile with a peak mixing ratio of 51.7 +/1 32.1 pptv, 1 sigma, at 27 km, also decreasing above and below that altitude. We compare the measured average profiles with the one reported set of in situ lower stratospheric mid-latitude measurements from 1986 and 1987, a previous two-dimensional (2-D) model calculation for 1987 and 1993, and a 2-D-model prediction for 2004. The measured average tropical profile is in close agreement with the model prediction; the northern mid-latitude profile is also consistent, although the peak in the measured profile occurs at a higher altitude (2.5-4.5km offset) than in the model prediction. Seasonal average 2-D-model predictions of the COClF stratospheric distribution for 2004 are also reported.

  14. Mid-latitude scintillation model. Technical report, 1 November 1985-31 October 1986

    SciTech Connect

    Robins, R.E.; Secan, J.A.; Fremouw, E.J.

    1986-10-31

    Radiowave scintillation in the presence of ionospheric disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report describes development of a model characterizing the plasma density irregularities that produce scintillation in the naturally disturbed mid-latitude F layer. The model will be incorporated into Program WBMOD, which includes subroutines for computing both link geometry and scintillation indices, the latter by means of phase screen diffraction theory. Earlier versions of WBMOD, were based on extensive analysis of scintillation data collected in the auroral and equatorial zones in Wideband Satellite Mission. The model described herein is based on similarly extensive analysis of Wideband data from one mid latitude station and of data collected from HiLat satellite at another mid latitude station. The model describes irregularities at an effective height of 350 km that are isotropic across the geomagnetic field and elongated by a factor of 10 along the field and whose one-dimensional spatial power spectrum obeys a single regime power law with a (negative) spectral index of 1.5. The height-integrated spectral strength of the irregularities is modeled as a function apex latitude of the point. The report highlights a disagreement by a factor of approximately three between irregularity strength inferred from the two satellites in a region of overlap between the two mid-latitude stations.

  15. Extreme high-latitude activity from high-speed stream embedded Alfvén waves

    NASA Astrophysics Data System (ADS)

    Tanskanen, Eija; Mursula, Kalevi; Hynönen, Reko; Snekvik, Kristian; Slavin, James; Goldstein, Melvyn

    2016-04-01

    Geomagnetic activity is known to be driven by interplanetary coronal mass ejections (ICME), interaction regions and high-speed streams (HSS). Storm activity in low-latitudes is mainly driven by ICMEs while substorm activity in high-latitudes is strongly modulated by high-speed streams. In this work we explore what makes high-speed streams more powerful in modulating high-latitudes than ICMEs. We identified Alfvén waves from 1995 to 2011. Alfvén waves are found throughout the solar cycle, but they are fastest, most frequent and most geo-effective in the declining phase of the solar cycle 23, when the number of high-speed streams at the Eart&hacute;s vicinity increases rapidly. HSS embedded Alfvén waves were found to carry twice as much Alfvénicity than ICME embedded Alfvén waves. Furthermore, we found a rapid transition from predominance of slow Alfvén waves in 2002 to fast Alfvén waves in 2003, which coincide with the 40% increase in substorm number and 30% increase in substorm strength. We conclude that Alfvénic fluctuations embedded to high-speed streams make them more powerful in modulating high-latitudes than ICMEs, and thus cause largest threat to high-latitude infrastructure during declining solar cycle phases.

  16. Spectroscopic Detection of COClF in the Tropical and Mid-Latitude Lower Stratosphere

    NASA Technical Reports Server (NTRS)

    Rinsland, Curtis P.; Nassar, Ray; Boone, Chris D.; Bernath, Peter; Chiou, Linda; Weisenstein, Debra K.; Mahieu, Emmanuel; Zander, Rodolphe

    2007-01-01

    We report retrievals of COClF (carbonyl chlorofluoride) based on atmospheric chemistry experiment (ACE) solar occultation spectra recorded at tropical and mid-latitudes during 2004-2005. The COClF molecule is a temporary reservoir of both chlorine and fluorine and has not been measured previously by remote sensing. A maximum COClF mixing ratio of 99.7+/-48.0 pptv (10(exp -12) per unit volume, 1 sigma) is measured at 28km for tropical and subtropical occultations (latitudes below 20deg in both hemispheres) with lower mixing ratios at both higher and lower altitudes. Northern hemisphere mid-latitude mixing ratios (30-50degN) resulted in an average profile with a peak mixing ratio of 51.7+/-32.1 pptv, 1 sigma, at 27 km, also decreasing above and below that altitude. We compare the measured average profiles with the one reported set of in situ lower stratospheric mid-latitude measurements from 1986 and 1987, a previous two-dimensional (2-D) model calculation for 1987 and 1993, and a 2-D-model prediction for 2004. The measured average tropical profile is in close agreement with the model prediction; the northern mid-latitude profile is also consistent, although the peak in the measured profile occurs at a higher altitude (2.5-4.5km offset) than in the model prediction. Seasonal average 2-D-model predictions of the COClF stratospheric distribution for 2004 are also reported.

  17. Latitude measures of Jupiter in the 0.89 micron methane band

    NASA Technical Reports Server (NTRS)

    Minton, R. B.

    1973-01-01

    Jupiter has been photographed by the Lunar and Planetary Laboratory in the 0.89 micron methane band since October 1968. A photometric evaluation of these photographs has not yet been carried out, but a visual study of this collection and a comparison with the color records has been made. This comparison, together with diameter and latitude measures of the methane records, shows that the albedos and latitudes of most features shown in 0.89 micron vary with time and the albedos and latitudes of most features shown in 0.89 micron vary with time and that there is no simple correlation between the visual color and/or intensity of a feature and its intensity in the methane band. The latitudes of the Red Spot and South Tropical Zone have remained unchanged, while those of the Equatorial Zone, North Tropical Zone, and South Polar Hood have changed. Measures of images taken near opposition show the polar diameter to be within 0.5% of the American Ephemeris Value, but the equatorial diameter as 1.3% smaller. Measures near quadrature suggest a phase defect 3.5 times greater in value than the American Ephemeris value. The large phase defect and bright South Polar Hood contribute to the circular appearance of Jupiter in methane. Latitude variations of the North edge of the South Polar Hood support the 1964 Munch and Younkin hypothesis that this feature is composed of frozen methane.

  18. Spectral characteristics of geomagnetic field variations at low and equatorial latitudes

    USGS Publications Warehouse

    Campbell, W.H.

    1977-01-01

    Geomagnetic field spectra from eight standard observations at geomagnetic latitudes below 30?? were studied to determine the field characteristics unique to the equatorial region. Emphasis was placed upon those variations having periods between 5 min and 4 hr for a selection of magnetically quiet, average, and active days in 1965. The power spectral density at the equator was about ten times that the near 30?? latitude. The initial manifestation of the equatorial electrojet as evidenced by the east-west alignment of the horizontal field or the change in vertical amplitudes occurred below about 20?? latitude. Induced current effects upon the vertical component from which the Earth conductivity might be inferred could best be obtained at times and latitudes unaffected by the electrojet current. Values of about 1.6 ?? 103 mhos/m for an effective skin depth of 500-600 km were determined. The spectral amplitudes increased linearly with geomagnetic activity index, Ap. The spectral slope had a similar behavior at all latitudes. The slope changed systematically with Ap-index and showed a diurnal variation, centered on local noon, that changed form with geomagnetic activity.

  19. Imaging-based observations of low-latitude auroras during 2001-2004 at Nayoro, Japan

    NASA Astrophysics Data System (ADS)

    Suzuki, Hidehiko; Chino, Haruka; Sano, Yasuo; Kadokura, Akira; Ejiri, Mitsumu K.; Taguchi, Makoto

    2015-07-01

    Color images of six low-latitude auroral events observed using color digital cameras at Nayoro (142.5° E, 44.4° N), Hokkaido, Japan, from 2001 to 2004, were analyzed to determine the events' locations and times of occurrence. Geographical azimuthal and elevation angles of the images' pixels were determined precisely by using the positions of the stars captured in the images. Horizontal regions covered by these auroral events were directly indicated by mapping the color images onto geographical maps and assuming that the emission layer's altitude is the lowest or highest value of a visible-level red aurora, as determined by the OI 630.0nm emission. The estimated geomagnetic latitudes and L values of these low-latitude auroral events were in the 39-50° range and below L < 2.5, respectively. This investigation indicates that four of the six auroral events were the same as those that were reported previously based on high-sensitivity optical observations at other sites on Hokkaido (Rikubetsu and Moshiri). Although the previous study is lacking information about the maximal brightness level of the red auroral events, the present investigation suggests that these four low-latitude auroral events reached the visible level. In addition, two new events were reported in this study. The present work provides essential information such as the morphology and appearance of visible auroras, which are extremely rare in mid- or low-latitude regions.

  20. [Modello di Management (Mo.Ma) del paziente affetto da schizofrenia: controllo della crisi, mantenimento, prevenzione delle ricadute e recovery con gli antipsicotici LAI].

    PubMed

    Brugnoli, Roberto; Rapinesi, Chiara; Kotzalidis, Georgios D; Marcellusi, Andrea; Mennini, Francesco S; De Filippis, Sergio; Carrus, Dario; Ballerini, Andrea; Francomano, Antonio; Ducci, Giuseppe; Del Casale, Antonio; Girardi, Paolo

    2016-01-01

    RIASSUNTO. La schizofrenia colpisce circa l'1% della popolazione e rappresenta un grave disturbo mentale con un notevole impatto anche sul funzionamento sociale, lavorativo e sulle attività della vita quotidiana. Le persone con schizofrenia hanno un tasso di mortalità superiore di 2-2,5 rispetto a quello della popolazione generale. La non aderenza ai farmaci antipsicotici è uno dei più importanti fattori di rischio per le ricadute e le ospedalizzazioni, sia nei pazienti con disturbo cronico sia al primo episodio, e conseguentemente contribuisce all'aumento dei costi sanitari. Gli antipsicotici atipici LAI possono migliorare l'aderenza al trattamento contribuendo a diminuire i tassi di ricaduta nei pazienti affetti da schizofrenia fin dall'esordio. Gli obiettivi primari nella gestione dei pazienti schizofrenici sono diretti, non solo alla riduzione dei sintomi nel breve termine, ma anche al mantenimento fisico e della funzionalità mentale, migliorando la qualità della vita e promuovendo il recupero del paziente. Scopo. Proporre un modello integrato, basato sulle evidenze, che fornisca un algoritmo efficace per il recupero del paziente schizofrenico e indagare l'efficacia e la sicurezza degli antipsicotici LAI nel trattamento, nel mantenimento, nella prevenzione delle ricadute e nella recovery dei pazienti affetti da schizofrenia. Metodi. Dopo un'accurata analisi di letteratura abbiamo identificato, raccolto e analizzato gli elementi qualificanti per un'ottimale gestione del paziente schizofrenico, definendo un modello di gestione e selezione delle alternative terapeutiche. Conclusioni. Il modello di gestione della schizofrenia proposto potrebbe consentire un migliore recupero funzionale del paziente grazie alla scelta di iniziare il percorso terapeutico, fin dalle prime fasi del disturbo soprattutto se in giovane età e al primo episodio, con un farmaco atipico LAI. All'interno dei farmaci antipsicotici atipici la formulazione LAI rappresenta una scelta

  1. On the Connection Between Solar Activity and Low-Latitude Aurorae in the Period 1715 - 1860

    NASA Astrophysics Data System (ADS)

    Vázquez, M.; Vaquero, J. M.; Curto, J. J.

    2006-11-01

    Observations of aurorae borealis at low latitudes are very rare and are clearly associated with strong geomagnetic storms. Morphologically, they are characterized by a diffuse red colour with no rapid motions. The main aim of this paper is to analyse two hitherto ignored aurorae that were observed at two low-latitude sites, Tenerife (28°N 18°W) and Mexico City (19°N 99°W), in 1770 and 1789, respectively. These observations can give supplementary information about the level of solar activity at those times where direct solar observations were rather scarce. Studying also the behaviour of the heliosphere during this period using different proxies, we find that the open magnetic field better describes auroral occurrences. The variation over time in geomagnetic latitude at the two sites is also calculated.

  2. In-situ measurements of nitric oxide in the high latitude upper stratosphere

    NASA Technical Reports Server (NTRS)

    Horvath, J. J.; Frederick, J. E.

    1985-01-01

    The vertical profiles of nitric acid were measured over Poker Flat, Alaska, in August 1984 and January and February 1985 using a rocket-launched parachute-deployed chemiluminescence sensor. Results for the altitude range 35-45 km indicate a large seasonal variation, with wintertime mixing ratios being a factor of two above summer values. The winter profiles contain sharp positive vertical gradients persisting through the highest altitudes observed. Above the stratopause, the mixing ratio observed in February increases rapidly and between 52 and 53 km reaches 148.9 ppbv, an order of magnitude greater than typical mid-latitude values measured with this instrument. Such behavior is consistent with the idea that nitric oxide produced at greater altitudes reaches the high-latitude upper stratosphere or lower mesosphere in winter. The results support the existence of a vertical coupling between diverse regions of the atmosphere in the high-latitude winter.

  3. Green house gas flux at high latitudes - constraints and susceptibility to a changing climate

    NASA Astrophysics Data System (ADS)

    Nilsson, M. B.

    2015-12-01

    High latitude boreal forests and peatlands contribute importantly to the land-atmosphere exchange of both carbon dioxide and methane. High latitude biomes are also identified as most vulnerable to changing climate. High latitudes are characterized by a strong seasonality in incoming solar radiation, weather conditions and biogeochemical processes. The strong seasonality in incoming solar radiation, not to change in response to a changing climate, constitute firm constraints on how changes in air temperature, evapotranspiration and precipitation will affect biogeochemical processes underlying the land atmosphere exchange of green house gases. Timing of the soil frost thaw and plant phenology thus constitutes two master controls on how fluxes of both CO2 and CH4 will be affected by weather conditions. In addition also the wintertime conditions importantly affect GHG fluxes both during winter time as well as during the succeeding summer. Examples will primarily be given for peatlands and coniferous forests.

  4. Quantifying Transport Between the Tropical and Mid-Latitude Lower Stratosphere

    PubMed

    Volk; Elkins; Fahey; Salawitch; Dutton; Gilligan; Proffitt; Loewenstein; Podolske; Minschwaner; Margitan; Chan

    1996-06-21

    Airborne in situ observations of molecules with a wide range of lifetimes (methane, nitrous oxide, reactive nitrogen, ozone, chlorinated halocarbons, and halon-1211), used in a tropical tracer model, show that mid-latitude air is entrained into the tropical lower stratosphere within about 13.5 months; transport is faster in the reverse direction. Because exchange with the tropics is slower than global photochemical models generally assume, ozone at mid-latitudes appears to be more sensitive to elevated levels of industrial chlorine than is currently predicted. Nevertheless, about 45 percent of air in the tropical ascent region at 21 kilometers is of mid-latitude origin, implying that emissions from supersonic aircraft could reach the middle stratosphere. PMID:8662478

  5. High latitude proton precipitation and light-ion density profiles during the magnetic storm initial phase

    NASA Technical Reports Server (NTRS)

    Burch, J. L.

    1973-01-01

    Measurements of precipitating protons and light ion densities by experiments on OGO-4 indicate that widespread proton precipitation occurs in predawn hours during the magnetic storm initial phase from the latitude of the high-latitude ion trough, or plasmapause , up to Lambda 75 deg. A softening of the proton spectrum is apparent as the plasmapause is approached. The separation of the low-latitude precipitation boundaries for 7.3 kev and 23.8 kev protons is approximately 1 deg, compared with a 3.6 deg separation which has been computed using the formulas of Gendrin and Eather and Carovillano. Consideration of probable proton drift morphology leads to the conclusion that protons ase injected in predawn hours, with widespread precipitation occurring in the region outside the plasmapause. Protons less energetic than approximately 7 kev drift eastward, while the more energetic protons drift westward, producing the observed dawn-dusk asymmetry for the lower-energy protons.

  6. High-latitude eruptions cast shadow over the African monsoon and the flow of the Nile

    NASA Astrophysics Data System (ADS)

    Oman, Luke; Robock, Alan; Stenchikov, Georgiy L.; Thordarson, Thorvaldur

    2006-09-01

    Nile River records indicate very low flow following the 1783-1784 Laki volcanic eruption, as well as after other high-latitude volcanic eruptions. As shown by climate model simulations of the Laki eruption, significant cooling (-1° to -3°C) of the Northern Hemisphere land masses during the boreal summer of 1783 resulted in a strong dynamical effect of weakening the African and Indian monsoon circulations, with precipitation anomalies of -1 to -3 mm/day over the Sahel of Africa, thus producing the low Nile flow. Future high-latitude eruptions would significantly impact the food and water supplies in these areas. Using observations of the flow of the Nile River, this new understanding is used to support a date of 939 for the beginning of the eruption of the Eldgjá volcano in Iceland, the largest high-latitude eruption of the past 1500 years.

  7. Observed mid-to-high latitude interchange of atmospheric angular momentum and some implications

    NASA Technical Reports Server (NTRS)

    Taylor, H. A., Jr.; Kramer, L.

    1990-01-01

    Graphic illustration of midlatitude interchange of atmospheric angular momentum between distant regions is presented. An examination is conducted of the global distribution of atmospheric angular momentum during 1977-1978 and 1982-1983 in order to identify evidence of prominent short-term interchanges of relavitive atmospheric angular momentum between mid and high latitude zones in both hemispheres. Thirty-day detrended angular momentum time series, prepared from the NMC global zonal wind data, are examined in latitude bands. The results confirm that momentum can be selectively redistributed between tropical, temperate, and high latitudes in patterns indicative of the development and dissipation of interacting regions, described variously in studies on the index cycle, seesaws, and telecommunications.

  8. Solar wind entry into the high-latitude terrestrial magnetosphere during geomagnetically quiet times.

    PubMed

    Shi, Q Q; Zong, Q-G; Fu, S Y; Dunlop, M W; Pu, Z Y; Parks, G K; Wei, Y; Li, W H; Zhang, H; Nowada, M; Wang, Y B; Sun, W J; Xiao, T; Reme, H; Carr, C; Fazakerley, A N; Lucek, E

    2013-01-01

    An understanding of the transport of solar wind plasma into and throughout the terrestrial magnetosphere is crucial to space science and space weather. For non-active periods, there is little agreement on where and how plasma entry into the magnetosphere might occur. Moreover, behaviour in the high-latitude region behind the magnetospheric cusps, for example, the lobes, is poorly understood, partly because of lack of coverage by previous space missions. Here, using Cluster multi-spacecraft data, we report an unexpected discovery of regions of solar wind entry into the Earth's high-latitude magnetosphere tailward of the cusps. From statistical observational facts and simulation analysis we suggest that these regions are most likely produced by magnetic reconnection at the high-latitude magnetopause, although other processes, such as impulsive penetration, may not be ruled out entirely. We find that the degree of entry can be significant for solar wind transport into the magnetosphere during such quiet times. PMID:23403567

  9. Effect of Latitude and Seasonal Variation on Scrub Typhus, South Korea, 2001-2013.

    PubMed

    Jeung, Ye Sul; Kim, Choon-Mee; Yun, Na Ra; Kim, Seok-Won; Han, Mi Ah; Kim, Dong-Min

    2016-01-01

    In South Korea, scrub typhus is one of the most common rickettsial diseases. The number of scrub typhus patients has increased in South Korea, a total of 69,210 cases were reported from 2001 to 2013. The seasonality and relation of scrub typhus cases to latitude were analyzed in this article using data obtained from the National Notifiable Diseases Surveillance System website of the Korea Centers for Disease Control and Prevention. The incidence of scrub typhus tended to increase in the later months of the year, especially in October-December. In general, lower latitudes were associated with a later peak incidence. Our results suggest for the first time that the monthly observed incidence tended to increase in the later months of the year as the latitude decreased, and on a yearly basis in Korea. PMID:26503283

  10. On transpolar arc formation correlated with solar wind entry at high latitude magnetosphere

    NASA Astrophysics Data System (ADS)

    Mailyan, B. G.; Shi, Q.; Maggiolo, R.; Zong, Q.; Fu, S.; Zhang, Y.; Yao, Z.; Sun, W.

    2014-12-01

    Recently, Cluster observations revealed the existence of new regions of solar wind plasma entry at the high latitudes of the Earth's magnetosphere, at the lobes tailward of the cusp region, mostly during periods of northward IMF. Such periods of northward IMF are associated with the presence of transpolar arcs. Observations from Global Ultraviolet Imager (GUVI) instrument onboard TIMED spacecraft are used to investigate a possible link between solar wind entry in the high latitude magnetosphere and the formation of transpolar arcs. Data from IMAGE and DMSP spacecraft are also used to investigate the time evolution and particle characteristics of the transpolar arc.We present a case study of a theta aurora correlated with the solar wind entry. The observations show a simultaneous occurrence of aurora activity at the magnetotail and high latitudes, suggesting two-part structure of the apparent continuous band of the transpolar arc.

  11. Quantifying transport between the tropical and mid-latitude lower stratosphere

    SciTech Connect

    Volk, C.M.; Dutton, G.S.; Gilligan, J.M.

    1996-06-21

    Airborne in situ observations of molecules with a wide range of lifetimes (methane, nitrous oxide, reactive nitrogen, ozone, chlorinated halocarbons, and halon-1211), used in a tropical tracer model, show that mid-latitude air is entrained into the tropical lower stratosphere within about 13.5 months; transport is faster in the reverse direction. Because exchange with the tropics is slower than global photochemical models generally assume, ozone at mid-latitudes appears to be more sensitive to elevated levels of industrial chlorine than is currently predicted. Nevertheless, about 45 percent of air in the tropical ascent region at 21 kilometers is of mid-latitude origin, implying that emissions from supersonic aircraft could reach the middle stratosphere. 49 refs., 5 figs.

  12. Multistation study of nighttime scintillations in low latitudes: evidence of control by equatorial F region irregularities

    SciTech Connect

    Somayajulu, Y.V.; Garg, S.C.; Dabas, R.S.; Singh, L.

    1984-05-01

    Equatorial spread F (ESF) and VHF scintillations have only in recent years been related to large-scale upwelling plumelike irregularity structures identified on VHF backscatter radar intensity maps. The present investigation is concerned with the results of an experiment of VHF scintillations recorded at a meridian chain of stations in India extending from close to the magnetic equator to 24.8 deg N magnetic latitude. It is found that the latitudinal development of scintillation-producing irregularities during high solar activity conditions is controlled by the development of ESF irregularities over the magnetic equator. Scintillations at all the stations equatorward of 21 deg N magnetic latitude are saturated, and their onset in the postsunset hours is almost abrupt. The occurrence of scintillations at latitudes away from the equator is dependent on their prior occurrence near the magnetic equator. 57 references.

  13. Latitude measures of Jupiter in the 0.89-micron methane band.

    NASA Technical Reports Server (NTRS)

    Minton, R. B.

    1973-01-01

    Jupiter has been photographed by the Lunar and Planetary Laboratory in the 0.89-micron methane band since October 1968. A photometric evaluation of these photographs has not yet been carried out, but a visual study of this collection and a comparison with the color records has been made. This comparison, together with diameter and latitude measures of the methane records, shows that the albedos and latitudes of most features shown at 0.89 micron vary with time and that there is no simple correlation between the visual color and/or intensity of a feature and its intensity in the methane band. The latitudes of the Red Spot and South Tropical Zone have remained unchanged, while those of the Equatorial Zone, North Tropical Zone, and South Polar Hood have changed.

  14. High and low latitude types of the downstream influences of the North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

    Song, Jie; Li, Chongyin; Zhou, Wen

    2014-02-01

    Using reanalysis data, we find that the downstream-propagating quasi-stationary Rossby wave train associated with the North Atlantic Oscillation (NAO) generally propagates along a high (low)-latitude pathway during warm (cold) El Niño-Southern Oscillation (ENSO) boreal winters. Consistent with the different propagation directions of the NAO-related downstream wave train, during the warm (cold) ENSO winters, the NAO is associated with significant 300 hPa geopotential height anomalies over eastern Siberia (the Arabian Sea, the east coast of Asia at around 40°N, and the North Pacific), and the near-surface air temperature perturbations associated with the NAO over the high latitudes of Asia are relatively strong (weak). Based on these differences, we argue that the NAO has two distinct types of downstream influence: a high-latitude type and a low-latitude type. Furthermore, we argue that the two types of NAO's downstream influence are modulated by the intensity of the subtropical potential vorticity (PV) meridional gradient over Africa. When this gradient is weak (strong), as in the warm (cold) ENSO winters, the NAO's downstream influence tends to be of the high (low)-latitude type. These results are further supported by analysis of intraseasonal NAO events. We separate NAO events into two categories in terms of the intensity of the subtropical PV gradient over Africa. Composites of the NAO events accompanied by a weak (strong) subtropical PV gradient show that the NAO-related downstream wave train tends to propagate along a high (low)-latitude pathway.

  15. The Latitude and Epoch for the Origin of the Astronomical Lore of Eudoxus

    NASA Astrophysics Data System (ADS)

    Schaefer, B. E.

    2003-12-01

    The earliest presentation of the ancient Greek constellations that survives to today is the poem titled Phaenomena by Aratus which is a reasonable copy of a book of the same name by Eudoxus (c. 366 BC) which has not survived. Hipparchus' sole surviving work (his Commentaries) also gives many direct quotes from Eudoxus' book. Eudoxus reports on many astronomical lore items such as that the head of Draco skims the northern horizon and that Orion sets when Scorpius rises. Many of these lore items have their validity depend on the latitude and epoch of the observations on which the lore is based, so for example the two lore items just quoted will each yield rather fuzzy simultaneous constraints on the latitude and epoch of the observer. In all, I have found 172 useful constraints for Eudoxus' lore, and the large number can be used to greatly increase the accuracy of the final joint constraint. My results are; (1) All lore reported by Eudoxus were based on observations from the year 1130 ± 80 BC and at a latitude of 36.0 ± 0.9 degrees north. (2) My derived date and latitude correspond only to the peak of the Assyrian culture. (3) The typical accuracy of the lore is 4-8 degrees, even though 1 degree accuracy is easy to be gotten by primitive methods. (4) About half the rise/set pairs recorded in the Mesopotamian MUL.APIN tablets are also given in Eudoxus' lore. (5) The MUL.APIN tablets have been independently determined to be based on observations from roughly 1000 BC at a latitude of 36 degrees north, which is consistent within uncertainties to my results for Eudoxus. Given the close match in date/latitude/content, I conclude that both Eudoxus' lore and MUL.APIN were derived from the same old Assyrian observations. This research was made possible with the support of the Herbert C. Pollack Award from the Dudley Observatory.

  16. Chromosome numbers in three species groups of freshwater flatworms increase with increasing latitude.

    PubMed

    Lorch, Sven; Zeuss, Dirk; Brandl, Roland; Brändle, Martin

    2016-03-01

    Polyploidy in combination with parthenogenesis offers advantages for plasticity and the evolution of a broad ecological tolerance of species. Therefore, a positive correlation between the level of ploidy and increasing latitude as a surrogate for environmental harshness has been suggested. Such a positive correlation is well documented for plants, but examples for animals are still rare. Species of flatworms (Platyhelminthes) are widely distributed, show a remarkably wide range of chromosome numbers, and offer therefore good model systems to study the geographical distribution of chromosome numbers. We analyzed published data on counts of chromosome numbers and geographical information of three flatworm "species" (Phagocata vitta, Polycelis felina and Crenobia alpina) sampled across Europe (220 populations). We used the mean chromosome number across individuals of a population as a proxy for the level of ploidy within populations, and we tested for relationships of this variable with latitude, mode of reproduction (sexual, asexual or both) and environmental variables (annual mean temperature, mean diurnal temperature range, mean precipitation and net primary production). The mean chromosome numbers of all three species increased with latitude and decreased with mean annual temperature. For two species, chromosome number also decreased with mean precipitation and net primary production. Furthermore, high chromosome numbers within species were accompanied with a loss of sexual reproduction. The variation of chromosome numbers within individuals of two of the three species increased with latitude. Our results support the hypothesis that polyploid lineages are able to cope with harsh climatic conditions at high latitudes. Furthermore, we propose that asexual reproduction in populations with high levels of polyploidization stabilizes hybridization events. Chromosomal irregularities within individuals tend to become more frequent at the extreme environments of high

  17. Vulnerability of high-latitude soil organic carbon in North America to disturbance

    NASA Astrophysics Data System (ADS)

    Grosse, Guido; Harden, Jennifer; Turetsky, Merritt; McGuire, A. David; Camill, Philip; Tarnocai, Charles; Frolking, Steve; Schuur, Edward A. G.; Jorgenson, Torre; Marchenko, Sergei; Romanovsky, Vladimir; Wickland, Kimberly P.; French, Nancy; Waldrop, Mark; Bourgeau-Chavez, Laura; Striegl, Robert G.

    2011-12-01

    This synthesis addresses the vulnerability of the North American high-latitude soil organic carbon (SOC) pool to climate change. Disturbances caused by climate warming in arctic, subarctic, and boreal environments can result in significant redistribution of C among major reservoirs with potential global impacts. We divide the current northern high-latitude SOC pools into (1) near-surface soils where SOC is affected by seasonal freeze-thaw processes and changes in moisture status, and (2) deeper permafrost and peatland strata down to several tens of meters depth where SOC is usually not affected by short-term changes. We address key factors (permafrost, vegetation, hydrology, paleoenvironmental history) and processes (C input, storage, decomposition, and output) responsible for the formation of the large high-latitude SOC pool in North America and highlight how climate-related disturbances could alter this pool's character and size. Press disturbances of relatively slow but persistent nature such as top-down thawing of permafrost, and changes in hydrology, microbiological communities, pedological processes, and vegetation types, as well as pulse disturbances of relatively rapid and local nature such as wildfires and thermokarst, could substantially impact SOC stocks. Ongoing climate warming in the North American high-latitude region could result in crossing environmental thresholds, thereby accelerating press disturbances and increasingly triggering pulse disturbances and eventually affecting the C source/sink net character of northern high-latitude soils. Finally, we assess postdisturbance feedbacks, models, and predictions for the northern high-latitude SOC pool, and discuss data and research gaps to be addressed by future research.

  18. Local endemicity and high diversity characterise high-latitude coral- Symbiodinium partnerships

    NASA Astrophysics Data System (ADS)

    Wicks, L. C.; Sampayo, E.; Gardner, J. P. A.; Davy, S. K.

    2010-12-01

    Obligate symbiotic dinoflagellates ( Symbiodinium) residing within the tissues of most reef invertebrates are important in determining the tolerance range of their host. Coral communities living at high latitudes experience wide fluctuations in environmental conditions and thus provide an ideal system to gain insights into the range within which the symbiotic relationship can be sustained. Further, understanding whether and how symbiont communities associated with high-latitude coral reefs are different from their tropical counterparts will provide clues to the potential of corals to cope with marginal or changing conditions. However, little is known of the host and symbiont partnerships at high latitudes. Symbiodinium diversity and specificity of high-latitude coral communities were explored using denaturing gradient gel electrophoresis (PCR-DGGE) analysis of the internal transcribed spacer regions (ITS1 and ITS2) of the ribosomal DNA at Lord Howe Island (31°S; Australia), and the Kermadec Islands (29°S; New Zealand). All but one host associated with clade C Symbiodinium, the exception being a soft coral ( Capnella sp.) that contained Symbiodinium B1. Besides ‘host-generalist’ Symbiodinium types C1 and C3, approximately 72% of the Symbiodinium identified were novel C types, and zonation of symbionts in relation to environmental parameters such as depth and turbidity was evident in certain host species. The high-latitude Symbiodinium communities showed little overlap and relatively high diversity compared with communities sampled on the tropical Great Barrier Reef. Although host specificity was maintained in certain species, others shared symbionts and this potential reduction of fidelity at high-latitude locations may be the result of locally challenging and highly variable environmental conditions.

  19. The effect of latitude on the risk and seasonal variation in hip fracture in Sweden.

    PubMed

    Odén, Anders; Kanis, John A; McCloskey, Eugene V; Johansson, Helena

    2014-10-01

    Although the optimal requirement of vitamin D for skeletal health in the general community is controversial, vitamin D deficiency impairs bone mineralization and increases bone turnover via secondary hyperparathyroidism, thus accelerating bone loss and increasing fracture risk. Support for a role of vitamin D deficiency in the epidemiology of hip fracture is found in the seasonal variation of hip fracture incidence that is reported in several studies. If the association were causal, then the incidence and amplitude of the seasonal variation in hip fracture risk should vary by latitude. We addressed this hypothesis by examining the incidence of hip fracture in men and women aged 50 years or more from Sweden (latitudes 55 to 69°) between 1987 and 2009. In order to reduce double counting, only one fracture in a period of a year was counted per individual. Men contributed 104,888 fractures in 33,313,065 person years and women 264,362 fractures in 38,387,660 person years. The effects of season and latitude were examined by Poisson regression. As expected, hip fracture rates were higher in women than in men. After adjustment for age, season and population density, hip fracture incidence increased by 3.0% (95% CI: 2.7-3.2%) per degree increase in latitude for men and by 1.9% (95% CI: 1.8-2.1%) for women. There was a marked seasonal variation of hip fracture with the highest risk in February and lower by 37.5% in men and by 23.5% women during the summer. There were significant interactions of amplitude of the seasonal variation with latitude (p < 0.001 for both men and women), indicating that seasonal variation during the year was more pronounced in the north of Sweden than in the south. The associations found with latitude and season is consistent with a role of vitamin D in hip fracture causation. PMID:24715585

  20. Simultaneous measurement of aurora-related, irregular magnetic pulsations at northern and southern high latitudes

    SciTech Connect

    Arnoldy, R.L.; Rajashekar, R. ); Cahill, L.J. Jr. ); Engebretson, M.J. ); Rosenberg, T.J. ); Mende, S.B. )

    1987-11-01

    A dominant feature of high-latitude magnetic pulsations is large-amplitude irregular pulsations (Pi) which are closely correlated with the movement of the observing station under particle precipitation, producing the dayside auroral and the high-latitude expansion of nightside aurora. The dayside Pi-1 pulsation maximum centered about local magnetic noon has no strong seasonal dependence, indicating that the dayside aurora illuminates both hemispheres independent of the latitude of the subsolar point. The summer noon pulsation maximum has, however, a greater longitudinal extent than the winter noon maximum, as measured at 74{degree}-75{degree} invariant latitude. The nightside magnetic pulsations are bursts of Pi (PiB) having an average duration of 15 min. From Defense Meteorological Satellite Program photos the auroral forms related to the high-latitude PiB can be identified as the poleward discrete arc generally having a large longitudinal extent. If the auroral forms are very similar in both hemispheres, then the large longitudinal extent coupled with movement of the auroral could explain why 85% of the PiB events have onsets within 10 min at opposite hemisphere sites (South Pole, Antarctica, and Sondre Stromfjord, Greenland) separated in local magnetic time by about 1.5 hours. There is no seasonal dependence in the statistical occurrence of PiB, nor in its simultaneity in opposite hemispheres. Apparently, the seasonal distortion of the tail plasma sheet has little effect on the acceleration of high-latitude auroral beams. The actual several minute time difference in opposite hemisphere onsets of PiB is probably due to the westward/poleward motion of the longitudinally extended aurora.

  1. Water vapour variability in the high-latitude upper troposphere - Part 2: Impact of volcanic emissions

    NASA Astrophysics Data System (ADS)

    Sioris, C. E.; Zou, J.; McElroy, C. T.; Boone, C. D.; Sheese, P. E.; Bernath, P. F.

    2015-09-01

    The impact of volcanic eruptions on water vapour in the region of the high latitude tropopause is studied using deseasonalized time series based on observations by the Atmospheric Chemistry Experiment (ACE) water vapour sensors, namely MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) and the Fourier Transform Spectrometer (ACE-FTS). The three eruptions with the greatest impact on the high latitude upper troposphere during the time frame of this satellite-based remote sensing mission are chosen. The Puyehue-Cordón Caulle volcanic eruption in June 2011 was the most explosive eruption in the past 24 years and resulted in an observed (50 ± 12) % increase in water vapour in the southern high-latitude upper troposphere in July 2011 that persisted into September 2011. A pair of Northern Hemisphere volcanoes, namely Eyjafjallajökull and Nabro, erupted in 2010 and 2011 respectively, increasing water vapour in the upper troposphere at northern high latitudes significantly for a period of ~ 3 months following each eruption. Both had a volcanic explosivity index of 4. Nabro led to a statistically significant increase of ~ 1 ppm in lower stratospheric (13.5-15.5 km) water vapour at northern high-latitudes (60-90° N) in September 2011, when the brunt of its plume arrived in the Arctic. These findings imply that steam emitted into the high-latitude, upper troposphere during volcanic eruptions must be taken into account to properly determine the magnitude of the trend in water vapour over the last decade.

  2. Export of Ozone-Poor Air from the Lower Tropical Stratosphere to Mid-latitudes

    NASA Astrophysics Data System (ADS)

    Spackman, J. R.; Weinstock, E. M.; Anderson, J. G.

    2002-05-01

    Analysis of ozonesonde profiles shows a decline in ozone of 7 to 9%/decade during the past 20 to 30 years in the northern mid-latitude lower stratosphere [Logan et al., 1999], exposing the large population at these latitudes to increased health risks. Heterogeneous processing leading to halogen-catalyzed ozone loss is not expected to occur in the mid-latitude lower stratosphere because in situ measurements indicate the air is consistently undersaturated and low in ClO in this region [Smith et al., 2001]. Furthermore, in situ measurements acquired aboard the NASA ER-2 aircraft during SOLVE (SAGE III Ozone Loss and Validation Experiment) suggest that equatorward mixing of ozone-depleted air from the Arctic vortex does not contribute significantly to declines in mid-latitude lower stratospheric ozone. Instead, tracer-tracer correlations from SOLVE indicate that rapid isentropic transport from the lower tropical stratosphere coupled with diabatic descent in mid-latitudes delivers very young, ozone-poor air to the lowermost stratosphere (θ < 380 K) during northern winter. Given this result, we hypothesize that the seasonal and interannual variability in the strength of this transport from the lower tropical stratosphere modulates mid-latitude lower stratospheric ozone. We investigate methods of using in situ observations to test this hypothesis. Logan, J.A., et al., Trends in the vertical distribution of ozone: A comparison of two analyses of ozonesonde data, Journal of Geophysical Research, 104, 26373-26399, 1999. Smith, J.B., et al., Mechanisms for midlatitude ozone loss: Heterogeneous chemistry in the lowermost stratosphere?, Journal of Geophysical Research, 106, 1297-1309, 2001.

  3. The Oweniidae (Annelida; Polychaeta) from Lizard Island (Great Barrier Reef, Australia) with the description of two new species of Owenia Delle Chiaje, 1844.

    PubMed

    Parapar, Julio; Moreira, Juan

    2015-01-01

    Study of the Oweniidae specimens (Annelida; Polychaeta) from Lizard Island (Great Barrier Reef, Australia) stored at the Australian Museum, Sydney and newly collected in August 2013 revealed the presence of three species, namely Galathowenia quelis Capa et al., 2012 and two new species belonging to the genus Owenia Delle Chiaje, 1844. Owenia dichotoma n. sp. is characterised by a very short branchial crown of about 1/3 of thoracic length which bears short, dichotomously-branched tentacles provided with the major division close to the base of the crown. Owenia picta n. sp. is characterised by a long branchial crown of about 4/5 of thoracic length provided with no major divisions, ventral pigmentation on thorax and the presence of deep ventro-lateral groove on the first thoracic chaetiger. A key of Owenia species hitherto described or reported in South East Asia and Australasia regions is provided based on characters of the branchial crown. PMID:26624080

  4. Patterns of cold-air drainage and microclimate in mid-latitude versus high-latitude mountains: contrasts and implications for climate change (Invited)

    NASA Astrophysics Data System (ADS)

    Pepin, N. C.

    2009-12-01

    Predictions of current spatial patterns of climate are difficult in areas of complex relief in all parts of the world, because of the interweaving influences of topography, elevation and aspect. These influences vary temporally as a result of the seasonal and diurnal cycles in radiation balance. In periods of negative energy balance, surface decoupling can occur as cold air drainage develops low-level temperature inversions, and the surface temperature regime beneath the inversion becomes divorced from free atmospheric forcing. Both the spatial scale and temporal persistence of this decoupling vary according to latitude, and although the physical processes that influence inversion formation are similar in polar areas and mid-latitude mountains, the contrasting seasonal and diurnal forcings make the end results very different. Examples are contrasted from detailed field temperature measurements (~50 sites per field area) taken over several years in areas of complex relief in the eastern Pyrenees (~42.5 deg N), the Oregon Cascades (also ~42.5 deg N) and Finnish Lapland (70 deg N and above the Arctic circle). In the former two locations decoupling is mostly diurnally driven, and small-scale topography is important in mediating the effects. Summer decoupling is brief and spatially limited, whereas winter decoupling can be more spatially extensive. There are strong relationships between synoptic conditions, as measured by objective flow indices at the 700 mb level (derived from NCEP/NCAR reanalysis fields) and the patterns of decoupling, which allow us to assess the effects of past and potential future circulation change on spatial patterns of future climate warming. In Finnish Lapland the decoupling regime most clearly approaches the mid-latitude pattern around the equinoxes when there are clear day and night periods. In winter and summer however (the polar night and polar day) with the muting of the diurnal cycle, processes are more poorly understood. Winter cold

  5. Present-day Exposures of Water Ice in the Northern Mid-latitudes of Mars

    NASA Technical Reports Server (NTRS)

    Allen, Carlton C.; Kanner, Lisa C.

    2007-01-01

    Water ice is exposed in the martian north polar cap, but is rarely exposed beyond the cap boundary. Orbital gamma ray spectrometry data strongly imply the presence of water ice within meters of the surface at latitudes north of approximately 60deg. We have examined mid-latitude areas of the northern plains displaying residual ice-rich layers, and report evidence of present-day surface exposures of water ice. These exposures, if confirmed, could con-strain the latitudinal and temporal stability of surface ice on Mars.

  6. Particle and field characteristics of the high-latitude plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Parks, G. K.; Mccarthy, M.; Fitzenreiter, R. J.; Ogilvie, K. W.; Etcheto, J.; Anderson, K. A.; Lin, R. P.; Anderson, R. R.; Eastman, T. E.; Frank, L. A.

    1984-01-01

    Particle and field data obtained by eight ISEE spacecraft experiments are used to define more precisely the characteristics of the high-latitude boundary region of the plasma sheet. A region immediately adjacent to the high-latitude plasma sheet boundary has particle and field characteristics distinctly different from those observed in the lobe and deeper in the central plasma sheet. Electrons over a broad energy interval are 'field-aligned' and bidirectional, whereas in the plasma sheet the distributions are more isotropic. The region supports intense ion flows, large-amplitude electric fields, and enhanced broad-band electrostatic noise.

  7. Dependence of the High Latitude Middle Atmosphere Ionization on Structures in Interplanetary Space

    NASA Technical Reports Server (NTRS)

    Bremer, J.; Lauter, E. A.

    1984-01-01

    The precipitation of high energetic electrons during and after strong geomagnetic storms into heights below 100 km in middle and subauroral latitudes is markedly modulated by the structure of the interplanetary magnetic field (IMF). Under relative quiet conditions the D-region ionization caused by high energetic particle precipitation (energies greater than 20 to 50 keV) depends on changes of the interplanetary magnetic field and also on the velocity of the solar wind. To test this assumption, the influence of the IMF-sector boundary crossings on ionospheric absorption data of high and middle latitudes by the superposed-epoch method was investigated.

  8. Increased process latitude in absorbance-modulated lithography via a plasmonic reflector

    NASA Astrophysics Data System (ADS)

    Holzwarth, Charles W.; Foulkes, John E.; Blaikie, Richard J.

    2011-08-01

    Absorbance-modulated lithography is a relatively new optical patterning method where a thin layer of photochromic molecules is placed between the far-field optics and photoresist. These molecules can be made transparent or opaque by illuminating with wavelengths λ1 or λ2, respectively. By simultaneously illuminating this layer with patterns of both wavelengths it is possible to create an absorption mask capable of subwavelength resolution. This resolution comes at the price of limited contrast and depth-of-focus resulting in poor process latitude. Here it is shown that by using TM polarization for λ1 and integrating a plasmonic reflector process latitude is increased by up to 66%.

  9. Evidence of the mid-latitude impact of Antarctic ozone depletion

    NASA Technical Reports Server (NTRS)

    Atkinson, Roger J.; Matthews, W. Andrew; Newman, Paul A.; Plumb, R. Alan

    1989-01-01

    Record low ozone values found over Australia and New Zealand during December 1987 following the record low Antarctic values of October 1987 are analyzed. The sudden decline of ozone amounts in midmonth rule out photochemical effects as a cause and permit the underlying processes to be investigated on a case study basis. Using data from ozone sondes, radiosondes, the Nimbus-7 total ozone mapping spectrometer, and meteorological analyses from the National Meteorological Center, it is argued that these low values resulted from transport of ozone-poor air from higher latitudes. Thus, it seems that the chemical destruction of ozone over Antarctica in early spring is having an impact on lower latitudes.

  10. Multi-Year Radar Observations of Planetary Waves at High Conjugate Latitudes (Invited)

    NASA Astrophysics Data System (ADS)

    Fritts, D. C.; Iimura, H.; Janches, D.; Mitchell, N. J.; Singer, W.

    2013-12-01

    Meteor radars at nearly conjugate latitudes from ~54o to 68o S and N are enabling multi-year studies of planetary wave (PW) structure and seasonal, interannual, and inter-hemispheric variability. The various PWs exhibit dramatically different seasonal and inter-hemispheric variability, strongly variable amplitude and phase structures with altitude, latitude, and time, and episodic maxima in E-P flux components. This talk will review these features defined with meteor radars at Rothera Station and Ferraz Base (62 and 68 S), on Tierra del Fuego (54 S), and at Juliusruh, Germany and Esrange, Sweden (55 and 68 N).

  11. Evidence for Amazonian mid-latitude glaciation on Mars from impact crater asymmetry

    NASA Astrophysics Data System (ADS)

    Conway, Susan J.; Mangold, Nicolas

    2013-07-01

    We find that crater slopes in the mid-latitudes of Mars have a marked north-south asymmetry, with the pole-facing slopes being shallower. We mapped impact craters in two southern hemisphere sites (Terra Cimmeria and Noachis Terra) and one northern hemisphere site (Acidalia Planitia) and used elevation data from the High Resolution Stereo Camera (HRSC) onboard Mars Express to find the maximum slope of impact crater walls in the four cardinal directions. Kreslavsky and Head (Kreslavsky, M.A., Head, J.W. [2003]. Geophys. Res. Lett. 30), using Mars Orbiter Laser Altimeter (MOLA) track data, also found that, in general, conjugate slopes are shallower in the pole-facing direction, but over a narrower (˜10°) and more constrained latitude band. They linked the asymmetry to active-layer formation (thaw) at high obliquity. However, Parsons and Nimmo (Parsons, R.A., Nimmo, F. [2009]. J. Geophys. Res. 114) studied crater asymmetry using MOLA gridded data and found no evidence of a relationship between crater asymmetry and latitude. Our work supports the observations of Kreslavsky and Head (Kreslavsky, M.A., Head, J.W. [2003]. Geophys. Res. Lett. 30), and shows that asymmetry is also found on conjugate crater slopes below the resolution of MOLA, over a wider latitude band than found in their work. We do not systematically find a sudden transition to asymmetric craters with latitude as expected for thaw-related processes, such as solifluction, gelifluction, or gully formation. The formation of gullies should produce the opposite sense of asymmetry to our observations, so cannot explain them despite the mid-latitude location and pole-facing preferences of gullies. We instead link this asymmetry to the deposition of ice-rich crater deposits, where the base of pole-facing slopes receive ten to hundreds of meters of additional net deposition, compared to equator-facing ones over the mid-latitudes. In support of this hypothesis we found that craters in Terra Cimmeria that have

  12. Heating of the high-latitude thermosphere during magnetically quiet periods

    NASA Technical Reports Server (NTRS)

    Reber, C. A.; Hedin, A. E.

    1974-01-01

    A persistent mid- to high-latitude heating phenomenon is observed in both hemispheres in data from the Ogo 6 quadrupole mass spectrometer. The phenomenon is evidenced by an increase in N2 density (indicative of a thermospheric temperature rise) and a depletion in helium (indicating an upwelling of air). The composition changes maximize near 0900 and 2100 UT, appear to corotate with the local magnetic pole, and are larger near equinox than near the summer solstice. The variation in latitude of the peak in the winter helium density (as a function of UT) is a specific manifestation of this general heating phenomenon.

  13. Investigating fossil hydrothermal systems by means of fluid inclusions and stable isotopes in banded travertine: an example from Castelnuovo dell'Abate (southern Tuscany, Italy)

    NASA Astrophysics Data System (ADS)

    Rimondi, Valentina; Costagliola, Pilario; Ruggieri, Giovanni; Benvenuti, Marco; Boschi, Chiara; Brogi, Andrea; Capezzuoli, Enrico; Morelli, Guia; Gasparon, Massimo; Liotta, Domenico

    2016-03-01

    Southern Tuscany (Italy) hosts geothermal anomalies with associated widespread CO2 gas-rich manifestations and active travertine-deposing thermal springs. Geothermal anomalies have been active since the Late Miocene and have led to the formation of widespread Late Miocene-Pleistocene travertine deposits and meso- and epithermal mineralizations. This study investigates the travertine deposit exposed in the Castelnuovo dell'Abate area of southern Tuscany. Here, a fissure-ridge type travertine deposit and its feeding conduits, currently filled with banded calcite veins (i.e. banded travertine), represent a spectacular example of fossil hydrothermal circulation in the peripheral area of the exploited Monte Amiata geothermal field. The Castelnuovo dell'Abate travertine deposit and associated calcite veins were analysed to establish the characteristics of the parent hydrothermal fluids, and the age of this circulation. The focus of the study was on fluid inclusions, rarely considered in travertine studies, but able to provide direct information on the physico-chemical characteristics of the original fluid. Uranium-thorium geochronological data provided further constraints on the: (1) age of tectonic activity; (2) age of the hydrothermal circulation; and (3) evolution of the Monte Amiata geothermal anomaly. Results indicate that brittle deformation (NW- and SE-trending normal to oblique-slip faults) was active during at least the Middle Pleistocene and controlled a hydrothermal circulation mainly characterized by fluids of meteoric origin, and as old as 300-350 ka. This is the oldest circulation documented to date in the Monte Amiata area. The fluid chemical composition is comparable to that of fluids currently exploited in the shallow reservoir of the Monte Amiata geothermal field, therefore suggesting that fluid composition has not changed substantially over time. These fluids, however, have cooled by about 70 °C in the last 300-350 ka, corresponding to a cooling rate

  14. Inverting x,y grid coordinates to obtain latitude and longitude in the vanderGrinten projection

    NASA Technical Reports Server (NTRS)

    Rubincam, D. P.

    1980-01-01

    The latitude and longitude of a point on the Earth's surface are found from its x,y grid coordinates in the vanderGrinten projection. The latitude is a solution of a cubic equation and the longitude a solution of a quadratic equation. Also, the x,y grid coordinates of a point on the Earth's surface can be found if its latitude and longitude are known by solving two simultaneous quadratic equations.

  15. Preference and performance in plant-herbivore interactions across latitude--a study in U.S. Atlantic salt marshes.

    PubMed

    Ho, Chuan-Kai; Pennings, Steven C

    2013-01-01

    High-latitude plants are often more palatable to herbivores than low-latitude conspecifics. Does increased plant palatability lead to better herbivore performance? Our field and laboratory work investigated (A) whether high-latitude plants have traits indicating that they should be higher-quality foods for herbivores; (B) whether geographic differences in plant quality are more important than local adaptation of herbivores. We studied 3 plant species and 6 invertebrate herbivores in U.S. Atlantic Coast. Past studies had shown high-latitude individuals of these plants are more palatable than low-latitude conspecifics. We documented plant traits and herbivore performance (body size) in the field across latitude. We collected individuals from different latitudes for factorial (plant region x herbivore region) laboratory experiments, examining how herbivore performance was affected by plant region, herbivore region, and their interaction (i.e., local adaptation). Field surveys suggested high-latitude plants were likely of higher quality to herbivores. Leaf nitrogen content in all plant species increased toward high latitudes, consistent with lower leaf C/N and higher leaf chlorophyll content at high latitudes. Furthermore, leaf toughness decreased toward higher latitudes in 1 species. The body size of 4 herbivore species increased with latitude, consistent with high-latitude leaves being of higher quality, while 2 grasshopper species showed the opposite pattern, likely due to life-history constraints. In the laboratory, high-latitude plants supported better performance in 4 herbivore species (marginal in the 5th). The geographic region where herbivores were collected affected herbivore performance in all 6 species; however, the pattern was mixed, indicating a lack of local adaptation by herbivores to plants from their own geographic region. Our results suggest that more-palatable plants at high latitudes support better herbivore growth. Given that geographic origin of

  16. Suggestions for Teaching 4th Grade LD Students the Concept of Longitude and Latitude in Geography.

    ERIC Educational Resources Information Center

    Holley, Cherie M.

    The paper suggests appropriate activities for teaching learning disabled fourth graders in a regular class the concepts of geographical latitude and longitude. Application of the learning principles identified in a review of the literature suggests the need to include visual, auditory, kinesthetic, and tactile activities of benefit to the entire…

  17. Digital elevation model (DEM) of Cascadia, latitude 39N-53N, longitude 116W-133W

    USGS Publications Warehouse

    Haugerud, Ralph A.

    1999-01-01

    This report contains a 250-meter digital elevation model (DEM) for Cascadia (latitude 39N - 53N, longitude 116W - 133W), a region that encompasses the Cascade volcanic arc, the Cascadia subduction zone, and the Juan de Fuca Ridge system. The DEM is distributed as file cascdem.tar.gz (39 MB; 78MB uncompressed).

  18. Suicide and Homicide Rates: Their Relationship to Latitude and Longitude and to the Weather.

    ERIC Educational Resources Information Center

    Lester, David

    1986-01-01

    Explored variation of suicide and homicide rates in the major standard metropolitan statistical areas of the United States to see whether regional variations in temperature and precipitation could account for some of the variation. Only the correlation between precipitation and homicide rates survived controls for latitude and longitude.…

  19. Is a high-latitude, second, reversed meridional flow cell the Sun's common choice?

    NASA Astrophysics Data System (ADS)

    Dikpati, M.

    2012-04-01

    Observations of surface Doppler meridional flow show that a high-latitude, reversed (equatorward) meridional flow cell, along with a poleward primary flow-cell, occurred during cycles 20, 21 and 22. The reversed cell vanished during most of cycle 23, but is reappearing in the current cycle 24. We explore theoretically what the Sun's natural choice of polar-region flow can be. We build a hydrodynamical model for computing and understanding the Sun's large-scale high latitude flows that includes Coriolis forces, turbulent diffusion of momentum and gyroscopic pumping. We solve for the meridional flow in a spherical 'polar cap' with a boundary at about 60-degree latitude. We find that there always exists at least one node in the latitudinal flow profile if the turbulent viscosity in the Sun's convection zone is 1010 to 1015 cm2 s-1. The Sun's turbulent viscosity is generally thought to be in the range of 1012 - 1013 cm2 s-1. For certain combinations of turbulent viscosity values and flow-speeds at the polar-cap boundary, our model exhibits 'node merging', producing only one flow-cell going all the way to the pole from the equator. These results suggest that it is more natural for the Sun to have one or more high-latitude reversed cells, but occasionally a single, unusually long primary cell, as was observed in cycle 23.

  20. Calculation of Latitude and Longitude for Points on Perimeter of a Circle on a Sphere

    SciTech Connect

    Morris, Heidi E.

    2015-08-14

    This document describes the calculation of the Earth-Centered Earth Fixed (ECEF) coordinates for points lying on the perimeter of a circle. Here, the perimeter of the circle lies on the surface of the sphere and the center of the planar circle is below the surface. These coordinates are converted to latitude and longitude for mapping fields on the surface of the earth.

  1. First-principles-based modeling of geomagnetically induced currents at mid- and low- latitudes

    NASA Astrophysics Data System (ADS)

    Pulkkinen, A.; Buzulukova, N.; Rastaetter, L.; Kuznetsova, M.; Viljanen, A.; Pirjola, R.

    2008-12-01

    Recently, Pulkkinen et al. (2007, Annales Geophysicae) introduced an approach to predict geomagnetically induced current (GIC) flow in high-voltage power transmission systems based on first-principles modeling of the near-space plasma environment. Their approach that has already been implemented as an experimental real-time system providing forecasts of GIC in the North American power transmission system, however, is applicable only to high-latitude situations. The accumulating new evidence is indicating that GIC is not only a high-latitude phenomenon but is important also at lower latitudes. Consequently, new tools and approaches are called for to address the newly appreciated truly global nature of GIC. In this paper we will briefly describe the current implementation of the experimental real-time GIC forecasting system operated at Community Coordinated Modeling Center (CCMC) at NASA/GSFC and address the shortcomings of the system. We will introduce the approach we have chosen to attack the problem of first- principles-based mid- and low-latitude GIC. The approach not only requires more comprehensive modeling of the near-space plasma environment by means of coupling global magnetohydrodynamic models to kinetic models of the inner magnetosphere (presented in a paper by Buzulukova et al., fall AGU 2008) but also more complex modeling of the geomagnetic induction process. We will present preliminary results generated by using the new GIC modeling capability and we will discuss the means to transfer the new approach into a real-time GIC forecasting system.

  2. Geomagnetic Field Variation during CME Events at High Latitude in European Zone

    NASA Astrophysics Data System (ADS)

    Chandel, Babita

    Geomagnetic Field Variation during CME Events at High Latitude in European Zone Babita Chandel, Shailendra Saini ,Sneha Yadav and A.K.Gwal Space Science Laboratory, Department of Physics, Barkatullah University, Bhopal-462026, India Abstract: The concerning results, are the variation of Geomagnetic Field Component in European Zone during CME events. The geomagnetic events selected for this study occurred during 2003-2006, a period of declining phase of solar cycle 23rd at European zone (Tromso, Sodankyla and Rorvik with Geomagnetic Latitude 69.39o N and Long. 18.56o E, Geomagnetic Latitude 67.360o N and Long. 26.363o E and Geomagnetic Latitude 64.56o N and Long.10.59 o E). From this study it is observed that the strength of a geomagnetic storm depends on the interplanetary-magnetospheric coupling parameter VBz. Higher the value of VBz, higher will be the strength of geomagnetic storm. Magnitude of variation at Rorvik is more as compared to Tromso and magnitude of variation is more at Tromso as compared to Sodankyla. Variation in vertical component is less as compared to the north-south and east-west component. Geomagnetic field components shows the variation when either interplanetary magnetic field orientes southward or remains southward for few hours.

  3. The domination of Saturn's low-latitude ionosphere by ring 'rain'.

    PubMed

    O'Donoghue, J; Stallard, T S; Melin, H; Jones, G H; Cowley, S W H; Miller, S; Baines, K H; Blake, J S D

    2013-04-11

    Saturn's ionosphere is produced when the otherwise neutral atmosphere is exposed to a flow of energetic charged particles or solar radiation. At low latitudes the solar radiation should result in a weak planet-wide glow in the infrared, corresponding to the planet's uniform illumination by the Sun. The observed electron density of the low-latitude ionosphere, however, is lower and its temperature higher than predicted by models. A planet-to-ring magnetic connection has been previously suggested, in which an influx of water from the rings could explain the lower-than-expected electron densities in Saturn's atmosphere. Here we report the detection of a pattern of features, extending across a broad latitude band from 25 to 60 degrees, that is superposed on the lower-latitude background glow, with peaks in emission that map along the planet's magnetic field lines to gaps in Saturn's rings. This pattern implies the transfer of charged species derived from water from the ring-plane to the ionosphere, an influx on a global scale, flooding between 30 to 43 per cent of the surface of Saturn's upper atmosphere. This ring 'rain' is important in modulating ionospheric emissions and suppressing electron densities. PMID:23579676

  4. Focus shift and process latitude of contact holes on attenuated phase-shifting masks

    NASA Astrophysics Data System (ADS)

    Wong, Alfred K. K.; Ferguson, Richard A.; Martino, Ronald M.; Neureuther, Andrew R.

    1995-05-01

    Focus shift and process latitude of contact features on both dark-field and light-field attenuated phase-shifting masks and binary intensity masks were examined using experimentally measured aerial images from the Ziess MSM-100 with IBM AIMS software, the scalar and thin-mask approximation in SPLAT, and the rigorous electromagnetic simulator TEMPEST. The dark-field attenuated phase-shifting mask (aPSM) contact holes show the most severe amount of focus shift, although the shift is not much different from that of space openings. Exposure latitude of dark field aPSM features shows a 12% improvement (from 33% to 45%) over conventional binary intensity mask. Depth-of-focus is also improved. under biasing of the mask features can also improve the process latitude of dark-field masks, whereas the contrary is true for light-field mask features. In general, the process latitude of light-field contact features is worse than that of dark-field features, indicating the need for positive deep-UV photoresist technology.

  5. GNSS Phase Scintillation and Cycle Slips Occurrence at High Latitudes: Climatology and Forecasting

    NASA Astrophysics Data System (ADS)

    Prikryl, Paul; Jayachandran, Periyadan T.; Chadwick, Richard; Kelly, Todd D.

    2014-05-01

    Space weather impacts the operation of modern technology that relies on Global Navigation Satellite Systems (GNSS). Ionospheric scintillation (rapid fluctuation of radio wave amplitude and phase) degrades GPS positional accuracy and causes cycle slips leading to loss of lock that affects performance of radio communication and navigation systems. At high latitudes, GPS scintillation and total electron content has been monitored by the Canadian High Arctic Ionospheric Network (CHAIN). GPS phase scintillation and cycle slips, as a function of magnetic latitude and local time, occur on the dayside in the ionospheric cusp, in the nightside auroral oval, and in the polar cap. Interplanetary coronal mass ejections and corotating interaction regions on the leading edge of high-speed streams are closely correlated with the occurrence of scintillation at high latitudes. Results of a superposed epoch analysis of time series of phase scintillation and cycle slips occurrence keyed by arrival times of high speed solar wind streams and interplanetary coronal mass ejections are presented. Based on these results, a method of probabilistic forecasting of high-latitude phase scintillation occurrence is proposed.

  6. Extension growth rates in two coral species from high-latitude reefs of Bermuda

    NASA Astrophysics Data System (ADS)

    Logan, A.; Tomascik, T.

    1991-09-01

    Mean annual growth rates (skeletal linear extension) in the hermatypic corals Porites astreoides Lamarck and Diploria labyrinthiformis (L.) were investigated mainly by X-radiography from a variety of localities at various depths on the high-latitude coral reefs of Bermuda. Growth rates of both species show an inverse curvilinear relationship with depth, with highest growth rates in the shallow inshore waters of Castle Harbour and lowest at the edge of the Bermuda platform and on the adjacent fore-reef slope. Annual density bands form seasonal couplets, with narrow, high density bands appearing to form in the spring-summer months and wider, low density bands over the rest of the year in both species. Comparison of the growth rates of P. astreoides from Bermuda with those from lower latitude West Indian localities, particularly Jamaica, indicates an inverse relationship with latitude and a similar inverse curvilinear relationship with depth at both geographic locations. Growth rate-locality differences in Bermuda for both species are suggested to be controlled mainly by local differences in wave energy and food supply and possibly seasonal water temperature fluctuations; growth rate-depth differences by decreasing illumination with depth; and growth rate-latitudinal differences by reduction in winter water temperatures and light levels with increasing latitude.

  7. The speeds of coronal mass ejections in the solar wind at mid heliographic latitudes: Ulysses

    NASA Technical Reports Server (NTRS)

    Gosling, J. T.; Bame, S. J.; Mccomas, D. J.; Phillips, J. L.; Goldstein, B. E.; Neugebauer, M.

    1994-01-01

    Six CMEs (coronal mass ejections) have been detected in the Ulysses plasma observations poleward of S31 deg. The most striking aspect of these mid-latitude CMEs was their high speeds; the overall average speed of these CMEs was approximately 740 km/s, which was comparable to that of the rest of the solar wind at these latitudes. This average CME speed is much higher than average CME speeds observed in the solar wind in the ecliptic or in the corona close to the Sun. The evidence indicates that the CMEs were not pushed up to high speeds in interplanetary space by interaction with trailing high-speed plasma. Rather, they simply seem to have received the same basic acceleration as the rest of the solar wind at these mid-latitudes. Our results suggest that the basic acceleration process for many CMEs at all latitudes is essentially the same as for the normal solar wind. Frequently most of this acceleration must occur well beyond 6 solar radii from Sun center.

  8. Morphology and phenomenology of the high-latitude E and F regions

    NASA Technical Reports Server (NTRS)

    Hunsucker, R. D.

    1979-01-01

    Results obtained at high latitude observatories on the behavior of E and F region ionization are presented including a bibliography. Behavior of E and F region ionization during day and night for quiet and disturbed conditions in the auroral and polar regions is described. Daily, seasonal and sunspot variations are also outlined.

  9. LOCATION AND MAGNETOSPHERIC MAPPING OF SATURN'S MID-LATITUDE INFRARED AURORAL OVAL

    SciTech Connect

    Stallard, Tom; Melin, Henrik; Cowley, Stanley W. H.; Miller, Steve; Lystrup, Makenzie B.

    2010-10-10

    Previous observations of Saturn's infrared aurorae have shown that a mid-latitude aurora exists significantly equatorward of the main auroral oval. Here, we present new results using data from four separate observing runs in 1998, 2003, 2008, and 2010. When combined, these provide a view of the mid-latitude aurora under a considerable range of viewing conditions, allowing the first calculation of the latitudinal position of this aurora to be made. This has shown that the mid-latitude aurora is located at the magnetic footprint of the region within the magnetosphere where the initial breakdown in corotation occurs, between 3 R {sub S} and the orbit of Enceladus ({approx}3.95 R {sub S}). We also confirm that this aurora is a continuous stable feature over a period of more than a decade and that an oval morphology is likely. When combined, these results indicate that the mid-latitude auroral oval is formed by currents driven by the breakdown process within the magnetosphere, in turn caused by mass loading from the torus of Enceladus, analogous with the volcanic moon Io's dominant role in the formation of Jupiter's main auroral oval.

  10. A forward propagation model of GPS scintillations to characterize high latitude ionospheric irregularities

    NASA Astrophysics Data System (ADS)

    Deshpande, K.; Bust, G. S.; Clauer, C. R.

    2012-12-01

    Complex magnetosphere-ionosphere coupling mechanisms result in high latitude irregularities that are difficult to characterize using only GPS scintillation measurements. GPS observations combined with physical parameters such as width, height of the irregularity etc. derived from modeling can be used to study the physics of these irregularities. We have recently developed a full 3D EM wave propagation model to simulate GPS scintillations in ionosphere. The model is applicable to high latitudes as it accounts for a more complicated geometry of magnetic field lines in high latitude regions. In this work, we present a parametric study to determine the sensitivity of the model towards different input parameters such as spectral index of the irregularity spectrum, outer scale of the irregularity, height, thickness and drift velocity of the irregularity etc. The parameters to which this model is most sensitive are determined from this study, and are focused on during our preliminary comparison with GPS scintillation data from 24 January 2012 storm from CASES GPS receiver on an AAL-PIP station at the South Pole, Antarctica. As a following step, we used our model and an inverse method for GPS scintillation observations from CASES and Novatel receivers at the South Pole in conjunction with ancillary observations from other instruments such as SuperDARN. We believe that such inverse method can be used to derive certain characteristics of the irregularity causing the scintillations and further achieve an improved understanding of the physics of these high latitude irregularities.

  11. Eastward propagation of transient field-aligned currents and Pi 2 pulsations at auroral latitudes

    SciTech Connect

    Webster, D.J.; Samson, J.C.; Rostoker, G. )

    1989-04-01

    Transient field-aligned currents associated with the substorm expansive phase produce the damped, quasisinusoidal, geomagnetic pulsations called Pi 2's. Mid-latitude and auroral latitude measurements of the fields of these pulsations have indicated that they are produced, for the most part, by westward propagating field-aligned currents at auroral latitudes, although some studies have shown hints of eastward propagation, particularly far to the east of the longitude of the onset of the expansive phase. This study uses data from the University of Alberta magnetometer array to identify the characteristics of the eastward propagating mode at high latitudes by measuring polarizations and apparent group and phase velocities in regions far to the east of the expansive phase. The results show that eastward propagating Pi 2's have very high phase velocities (typically 40 km/s) which are comparable with those of the westward propagating mode. The polarizations and field configurations are compatible with a field-aligned and ionospheric current model which is very similar to that for the westward propagating component. These current models suggest that Pi 2's may be caused by shear Alfven waves produced by an azimuthally expanding, fast mode wave. The shear Alfven waves are reflected from the auroral ionosphere to produce the latitudinally localized field-aligned and ionospheric currents in the eastward (and westward) propagating modes.

  12. Modulation of total electron content by global Pc5 waves at low latitudes

    NASA Astrophysics Data System (ADS)

    Vorontsova, E.; Pilipenko, V.; Fedorov, E.; Sinha, A. K.; Vichare, G.

    2016-01-01

    Earlier studies have successfully demonstrated that the GPS-TEC technique is a powerful method to study the propagation pattern of transient disturbances in the ionosphere. This technique has turned out to be sensitive enough to detect ionospheric signatures of ULF waves as well, particularly at high latitudes. It has already been reported earlier that during the recovery phase of the strong magnetic storm on Oct. 31, 2003, intense Pc5 geomagnetic activity was accompanied with distinct pulsations of the same periodicity in the TEC data from high-latitude GPS receiving stations. The present study reveals the identical features in geomagnetic and TEC data at low-latitude stations in the Indian sector as well. However, the presented observational results on TEC modulation by global Pc5 waves at low latitudes cannot be interpreted on the basis of the Alfven mode concept. The most promising mechanism that can explain the present observations is the plasma compression by fast magnetosonic mode. Theoretical order-of-magnitude estimates of the ratio between pulsation amplitudes in TEC and geomagnetic field based on the proposed mechanism is found to be about the same as the observed values.

  13. Long-term Statistical Analysis of the Simultaneity of Forbush Decrease Events at Middle Latitudes

    NASA Astrophysics Data System (ADS)

    Lee, Seongsuk; Oh, Suyeon; Yi, Yu; Evenson, Paul; Jee, Geonhwa; Choi, Hwajin

    2015-03-01

    Forbush Decreases (FD) are transient, sudden reductions of cosmic ray (CR) intensity lasting a few days, to a week. Such events are observed globally using ground neutron monitors (NMs). Most studies of FD events indicate that an FD event is observed simultaneously at NM stations located all over the Earth. However, using statistical analysis, previous researchers verified that while FD events could occur simultaneously, in some cases, FD events could occur non-simultaneously. Previous studies confirmed the statistical reality of non-simultaneous FD events and the mechanism by which they occur, using data from high-latitude and middle-latitude NM stations. In this study, we used long-term data (1971-2006) from middle-latitude NM stations (Irkutsk, Climax, and Jungfraujoch) to enhance statistical reliability. According to the results from this analysis, the variation of cosmic ray intensity during the main phase, is larger (statistically significant) for simultaneous FD events, than for non-simultaneous ones. Moreover, the distribution of main-phase-onset time shows differences that are statistically significant. While the onset times for the simultaneous FDs are distributed evenly over 24- hour intervals (day and night), those of non-simultaneous FDs are mostly distributed over 12-hour intervals, in daytime. Thus, the existence of the two kinds of FD events, according to differences in their statistical properties, were verified based on data from middle-latitude NM stations.

  14. Latitude Hooks and Azimuth Kings: How To Build and Use 18 Traditional Navigational Tools.

    ERIC Educational Resources Information Center

    Fisher, Dennis

    This book contains directions for building and using 18 different traditional navigational tools. Each of the devices discussed has at one time or another been used for the practical business of navigation. Devices featured in this book include the Latitude Hook, Kamal, Astrolabe, Quadrant, Astronomical Ring, Sundial, Nocturnal, Cross Staff,…

  15. Solar Radiation Disinfection of Drinking Water at Temperate Latitudes: Inactivation rates for an optimized reactor configuration

    EPA Science Inventory

    Solar radiation-driven inactivation of bacteria, virus and protozoan pathogen models was quantified in simulated drinking water at a temperate latitude (34°S). The water was seeded with Enterococcus faecalis, Clostridium sporogenes spores, and P22 bacteriophage, each at ca 1 x 10...

  16. Sex differences in lizard escape decisions vary with latitude, but not sexual dimorphism.

    PubMed

    Samia, Diogo S M; Møller, Anders Pape; Blumstein, Daniel T; Stankowich, Theodore; Cooper, William E

    2015-04-22

    Sexual selection is a powerful evolutionary mechanism that has shaped the physiology, behaviour and morphology of the sexes to the extent that it can reduce viability while promoting traits that enhance reproductive success. Predation is one of the underlying mechanisms accounting for viability costs of sexual displays. Therefore, we should expect that individuals of the two sexes adjust their anti-predator behaviour in response to changes in predation risk. We conducted a meta-analysis of 28 studies (42 species) of sex differences in risk-taking behaviour in lizards and tested whether these differences could be explained by sexual dichromatism, by sexual size dimorphism or by latitude. Latitude was the best predictor of the interspecific heterogeneity in sex-specific behaviour. Males did not change their escape behaviour with latitude, whereas females had increasingly reduced wariness at higher latitudes. We hypothesize that this sex difference in risk-taking behaviour is linked to sex-specific environmental constraints that more strongly affect the reproductive effort of females than males. This novel latitudinal effect on sex-specific anti-predator behaviour has important implications for responses to climate change and for the relative roles of natural and sexual selection in different species. PMID:25788595

  17. Enhanced antisunward convection and F region scintillations at mid-latitudes during storm onset

    SciTech Connect

    Foster, J.C. ); Aarons, J. )

    1988-10-01

    Millstone Hill radar observations over a wide span of latitudes detail the onset of 300 m/s antisunward (westward) convection at mid and low latitudes in the morning sector as a region of storm-enhanced sunward convection retreats poleward. Ring current observations reported by Lui et al. (1987) suggest that the magnetospheric shielding layer was coincident with the observed reversal between sunward and antisunward convection. A strong southward component of the F region neutral wind is observed at latitudes equatorward of the convection reversal. These observations are in agreement with the model of Spiro et al. (1988), who find that storm-enhanced neutrral winds at latitudes equatorward of the shielding layer can generate a long-lived perturbation electric field in the inner magnetosphere. The observations show the growth of the subauroral electric field as the shielding boundary moves poleward. They observe 136-MHz scintillations in both the auroral sunwarrd convection region and the region of subauroral antisunward convection when the convection electric fields exceed 5 mV/m.

  18. Latitude, Energy, and Time Variations of Energetic Neutral Atom Spectral indices Measured by IBEX

    NASA Astrophysics Data System (ADS)

    Desai, Mihir; Heerikhuisen, Jacob; McComas, David; Funsten, Herbert; Pogorelov, Nikolai; Zank, Gary; Schwadron, Nathan; Fuselier, Stephen; Allegrini, Frederic; Dayeh, Maher A.

    2016-07-01

    We investigate the latitude, energy, and time variations of the globally distributed 0.5-6 keV energetic neutral atom (ENA) spectra measured by the Interstellar Boundary Explorer (IBEX) during the first 5 years of the mission. Our previous results based on the first 3 years of IBEX observations showed that the ENA spectral indices at the two lowest energies (0.89 and 1.47 keV) exhibit no clear trend with ecliptic latitude θ, while those at ˜2.29 and ˜3.41 keV exhibit a clear latitudinal pattern; flatter spectra occur above 60° latitude and steeper spectra occur within ±30° of the equator. While these results confirmed the previously reported latitudinal organization of the ENA spectra and their remarkable similarity to that of the solar wind (SW) speed observed by Ulysses in the inner heliosphere, we also showed that, unlike previous reports, the ˜0.5-6 keV globally distributed ENA spectral indices could not be represented as single power laws over much of the sky, and that they depend on energy and latitude. In this paper we extend the above results to include years 4 and 5 of IBEX observations and investigate if the spectral indices vary as a function of time. Finally, we discuss implications of our results on models and simulations that seek to map the IBEX ENA observations back to the latitudinal profile of the SW speed structure observed in the inner heliosphere.

  19. Relocation, high-latitude warming and host genetic identity shape the foliar fungal microbiome of poplars.

    PubMed

    Bálint, Miklós; Bartha, László; O'Hara, Robert B; Olson, Matthew S; Otte, Jürgen; Pfenninger, Markus; Robertson, Amanda L; Tiffin, Peter; Schmitt, Imke

    2015-01-01

    Micro-organisms associated with plants and animals affect host fitness, shape community structure and influence ecosystem properties. Climate change is expected to influence microbial communities, but their reactions are not well understood. Host-associated micro-organisms are influenced by the climate reactions of their hosts, which may undergo range shifts due to climatic niche tracking, or may be actively relocated to mitigate the effects of climate change. We used a common-garden experiment and rDNA metabarcoding to examine the effect of host relocation and high-latitude warming on the complex fungal endophytic microbiome associated with leaves of an ecologically dominant boreal forest tree (Populus balsamifera L.). We also considered the potential effects of poplar genetic identity in defining the reactions of the microbiome to the treatments. The relocation of hosts to the north increased the diversity of the microbiome and influenced its structure, with results indicating enemy release from plausible pathogens. High-latitude warming decreased microbiome diversity in comparison with natural northern conditions. The warming also caused structural changes, which made the fungal communities distinct in comparison with both low-latitude and high-latitude natural communities, and increased the abundance of plausible pathogens. The reactions of the microbiome to relocation and warming were strongly dependent on host genetic identity. This suggests that climate change effects on host-microbiome systems may be mediated by the interaction of environmental factors and the population genetic processes of the hosts. PMID:25443313

  20. Sex differences in lizard escape decisions vary with latitude, but not sexual dimorphism

    PubMed Central

    Samia, Diogo S. M.; Møller, Anders Pape; Blumstein, Daniel T.; Stankowich, Theodore; Cooper, William E.

    2015-01-01

    Sexual selection is a powerful evolutionary mechanism that has shaped the physiology, behaviour and morphology of the sexes to the extent that it can reduce viability while promoting traits that enhance reproductive success. Predation is one of the underlying mechanisms accounting for viability costs of sexual displays. Therefore, we should expect that individuals of the two sexes adjust their anti-predator behaviour in response to changes in predation risk. We conducted a meta-analysis of 28 studies (42 species) of sex differences in risk-taking behaviour in lizards and tested whether these differences could be explained by sexual dichromatism, by sexual size dimorphism or by latitude. Latitude was the best predictor of the interspecific heterogeneity in sex-specific behaviour. Males did not change their escape behaviour with latitude, whereas females had increasingly reduced wariness at higher latitudes. We hypothesize that this sex difference in risk-taking behaviour is linked to sex-specific environmental constraints that more strongly affect the reproductive effort of females than males. This novel latitudinal effect on sex-specific anti-predator behaviour has important implications for responses to climate change and for the relative roles of natural and sexual selection in different species. PMID:25788595

  1. Flight phenology of male Cactoblastis cactorum (Lepidoptera: Pyralidae) at different latitudes in the southeastern United States

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Long term trapping studies of the invasive moth Cactoblastis cactorum (Berg) were conducted at various latitudes from Puerto Rico to South Carolina. Three flight periods per year were identified at the five temperate sties studied, which covered the majority of the insects’ mainland United States i...

  2. Dependence of the duration of geomagnetic polarity reversals on site latitude.

    PubMed

    Clement, Bradford M

    2004-04-01

    An important constraint on the processes governing the geodynamo--the flow in the outer core responsible for generating Earth's magnetic field--is the duration of geomagnetic polarity reversals; that is, how long it takes for Earth's magnetic field to reverse. It is generally accepted that Earth's magnetic field strength drops to low levels during polarity reversals, and the field direction progresses through a 180 degrees change while the field is weak. The time it takes for this process to happen, however, remains uncertain, with estimates ranging from a few thousand up to 28,000 years. Here I present an analysis of the available sediment records of the four most recent polarity reversals. These records yield an average estimate of about 7,000 years for the time it takes for the directional change to occur. The variation about this mean duration is not random, but instead varies with site latitude, with shorter durations observed at low-latitude sites, and longer durations observed at mid- to high-latitude sites. Such variation of duration with site latitude is predicted by simple geometrical reversal models, in which non-dipole fields are allowed to persist while the axial dipole decays through zero and then builds in the opposite direction, and provides a constraint on numerical dynamo models. PMID:15071591

  3. The speeds of coronal mass ejections in the solar wind at mid heliographic latitudes: Ulysses

    SciTech Connect

    Gosling, J.T.; Bame, S.J.; McComas, D.J.; Phillips, J.L.; Goldstein, B.E.; Neugebauer, M.

    1994-06-15

    Six CMEs have been detected in the Ulysses plasma observations poleward of S31{degrees}. The most striking aspect of these mid-latitude CMEs was their high speeds; the overall average speed of these CMEs was {approximately}740 km s{sup {minus}1}, which was comparable to that of the rest of the solar wind at these latitudes. This average CME speed is much higher than average CME speeds observed in the solar wind in the ecliptic or in the corona close to the Sun. The evidence indicates that the CMEs were not pushed up to high speeds in interplanetary space by interaction with trailing high-speed plasma. Rather, they simply seem to have received the same basic acceleration as the rest of the solar wind at these mid-latitudes. These results suggest that the basic acceleration process for many CMEs at all latitudes is essentially the same as for the normal solar wind. Frequently most of this acceleration must occur well beyond 6 solar radii from Sun`sj center. 18 refs., 4 figs.

  4. Latitude, Energy, and Time Variations of Energetic Neutral Atom Spectral indices Measured by IBEX

    NASA Astrophysics Data System (ADS)

    Desai, M. I.; McComas, D. J.; Dayeh, M. A.; Funsten, H. O.; Schwadron, N.; Heerikhuisen, J.; Fuselier, S. A.; Allegrini, F.; Pogorelov, N.; Zank, G. P.

    2015-12-01

    We investigate the latitude, energy, and time variations of the globally distributed ~0.5-6 keV energetic neutral atom (ENA) spectra measured by the Interstellar Boundary Explorer (IBEX) during the first 5 years of the mission. Our previous results based on the first 3 years of IBEX observations showed that the ENA spectral indices at the two lowest energies (~0.89 and 1.47 keV) exhibit no clear trend with ecliptic latitude θ, while those at ~2.29 and ~3.41 keV exhibit a clear latitudinal pattern; flatter spectra occur above 60° latitude and steeper spectra occur ±30° of the equator. While these results confirmed the previously reported latitudinal organization of the ENA spectra and their remarkable similarity to that of the solar wind (SW) speed observed by Ulysses in the inner heliosphere, we also showed that, unlike previous reports, the ~0.5-6 keV globally distributed ENA spectral indices could not be represented as single power laws over much of the sky, and that they depend on energy and latitude. In this work we extend the above results to include years 4 and 5 of IBEX observations and investigate if the spectral indices vary as a function of time. Finally, we discuss implications of our results on models and simulations that seek to map the IBEX ENA observations back to the latitudinal profile of the SW speed structure observed in the inner heliosphere.

  5. A CME-driven solar wind distrubance observed at both low and high heliographic latitudes

    SciTech Connect

    Gosling, J.T.; McComas, D.J.; Phillips, J.L.

    1995-07-01

    A solar wind disturbance produced by a fast coronal mass ejection, CME, that departed from the Sun on Feburary 20, 1994 was observed in the ecliptic plane at 1 AU by IMP 8 and at high heliographic latitudes at 3.53 AU by Ulysses. In the ecliptic the disturbance included a strong forward shock but no reverse shock, while at high latitudes the disturbance was bounded by a relatively weak forward-reverse shock pair. It is clear that the disturbance in the ecliptic plane was driven primarily by the relative speed between the CME and a slower ambient solar wind ahead, whereas at higher latitudes the disturbance was driven by expansion of the CME. The combined IMP 8 and Ulysses observations thus provide a graphic illustration of how a single fast CME can produce very different types of solar wind disturbances at low and high heliographic latitudes. Simple numerical simulations help explain observed differences at the two spacecraft. 12 refs., 3 figs.

  6. THE ROTATION PROFILE OF SOLAR MAGNETIC FIELDS BETWEEN {+-}60 Degree-Sign LATITUDES

    SciTech Connect

    Shi, X. J.; Xie, J. L.

    2013-08-10

    Through a cross-correlation analysis of the Carrington synoptic maps of solar photospheric magnetic fields from Carrington Rotation Nos. 1625 to 2129 (from 1975 February to 2012 October), the sidereal rotation rates of solar magnetic fields between {+-}60 Degree-Sign latitudes are investigated. It seems that the temporal variation of rotation rates should be related to the solar cycle phase. The rotation profile of magnetic fields is obtained: the sidereal rotation rates decrease from the equator to mid-latitude and reach their minimum values of about 13.16 deg day{sup -1} (13.17 deg day{sup -1}) at 53 Degree-Sign (54 Degree-Sign ) latitude in the northern (southern) hemisphere, then increase toward higher latitudes. This rotation profile is different from the differential rotation law obtained by Snodgrass from a cross-correlation analysis of daily magnetograms, in which the rotation rates show a steep decrease from the equator to the poles. However, it is much closer to the quasi-rigid rotation law derived by Stenflo from an auto-correlation analysis of daily magnetograms. Some possible interpretations are discussed for the resulting rotation profile.

  7. High-latitude proton precipitation and light ion density profiles during the magnetic storm initial phase.

    NASA Technical Reports Server (NTRS)

    Burch, J. L.

    1973-01-01

    Measurements of precipitating protons and light ion densities by experiments on Ogo 4 indicate that widespread proton precipitation occurs in predawn hours during the magnetic storm initial phase from the latitude of the high-latitude ion trough, or plasmapause, up to latitudes greater than 75 deg. A softening of the proton spectrum is apparent as the plasmapause is approached. The separation of the low-latitude precipitation boundaries for 7.3-keV and 23.8-keV protons is less than about 1 deg, compared with a 3.6-deg separation that has been computed by using the formulas of Gendrin and Eather and Carovillano. Consideration of probable proton drift morphology leads to the conclusion that protons are injected in predawn hours, widespread precipitation occurring in the region outside the plasmapause. Protons less energetic than 7 keV drift eastward, whereas the more energetic protons drift westward, producing the observed dawn-dusk asymmetry for the lower-energy protons.

  8. Response of High Latitude Wetland Fluxes of Methane to Changes in Temperature and Water

    NASA Astrophysics Data System (ADS)

    Worden, J.; Bloom, A. A.; Bowman, K. W.; Lee, M.; Frankenberg, C.; Schimel, D.

    2014-12-01

    High latitude methane fluxes represent between 5 - 20% of the total methane budget. This large range in methane emissions estimates are due to poor knowledge of wetland extent, dependency of emissions to temperature and water, the seasonal cycle of freezing and thawing, and a poor measurement network. In turn, these uncertainties limit our ability to predict future methane fluxes in response to a warming climate. Temperature and rainfall at high-latitudes changed dramatically between 2009 and 2010, likely in response to variations in ENSO and the Arctic Anomaly. We might therefore expect that high-latitude methane fluxes significantly changed between 2009 and 2010 because these methane fluxes primarily depend on these environmental parameters. In this study, we implement several wetland models and their corresponding methane fluxes for 2009 and 2010 into the GEOS-Chem global chemistry model. We evaluate whether satellite measurements such as total column measurement from GOSAT or TROP-OMI can distinguish between these models, allowing for better estimates of the magnitude and timing of wetland fluxes and improved process understanding of high-latitude methane emissions.

  9. Status of High Latitude Precipitation Estimates: The Role of GPM in Advancing our Current Understanding

    NASA Astrophysics Data System (ADS)

    Behrangi, A.; Richardson, M.; Christensen, M.; Huffman, G. J.; Adler, R. F.; Stephens, G. L.; Lambrigtsen, B.

    2015-12-01

    This presentation reviews the current status of precipitation estimation from observation and reanalysis at high latitudes and discusses new insights gained by GPM. An intercomparison of high-latitude precipitation characteristics from observation-based and reanalysis products is performed. Precipitation products from GPM and the cloud profiling radar on the CloudSat satellite provide an independent assessment to other products which have already been widely used, these being the observationally-based GPCP, GPCC and CMAP and the reanalyses ERA-Interim, MERRA and NCEP-DOE. Seasonal and annual total precipitation in both hemispheres poleward of 55° latitude is considered in all products, and GPM and CloudSat products are used to assess frequency of precipitation occurrence by phase, defined as rain, snow or mixed phase. Estimates of snowfall over Antarctica and Greenland are compared from various products. A number of disagreements on regional or seasonal scales are identified which will be reported and discussed. These estimates from observations and reanalyses provide useful insights for diagnostic assessment of precipitation products in high latitudes, quantifying the current uncertainties among observations and reanalyses, and establishing a benchmark for assessment of climate models.

  10. Three-dimensional electron density along the WSA and MSNA latitudes probed by FORMOSAT-3/COSMIC

    NASA Astrophysics Data System (ADS)

    Chang, F. Y.; Liu, J. Y.; Chang, L. C.; Lin, C. H.; Chen, C. H.

    2015-09-01

    In this paper, we employ electron density profiles derived by the GPS radio occultation experiment aboard the FORMOSAT-3/COSMIC (F3/C) satellites to examine the electron density on geographic latitudes of 40° to 80° in the Southern hemisphere and 30° to 60° in the Northern hemisphere at various global fixed local times from February 2009 to January 2010. The results reveal that an eastward shift of a single-peak plasma density feature occurs along the Weddell Sea Anomaly (WSA) latitudes, while a double-peak plasma density feature appears along the northern Mid-latitude Summer Nighttime Anomaly (MSNA) latitudes. A cross-comparison between three-dimensional F3/C electron density and HWM93 simulation confirms that the magnetic meridional effect and vertical effect caused by neutral winds exhibit the eastward shifts. Furthermore, we find that the eastward shift of the peaks when viewed as a function of local time suggests that they could be interpreted as being comprised of different tidal components with distinct zonal phase velocities in local time.

  11. Interplanetary gas. XX - Does the radial solar wind speed increase with latitude

    NASA Technical Reports Server (NTRS)

    Brandt, J. C.; Harrington, R. S.; Roosen, R. G.

    1975-01-01

    The astrometric technique used to derive solar wind speeds from ionic comet-tail orientations has been used to test the suggestion that the radial solar wind speed is higher near the solar poles than near the equator. We find no evidence for the suggested latitude variation.

  12. The Influence of Arctic Amplification on Mid-Latitude Atmospheric Circulation and Extreme Weather Events

    NASA Astrophysics Data System (ADS)

    Vavrus, S. J.; Francis, J. A.

    2012-12-01

    We expand on our recent work that provided evidence for a mechanism linking Arctic Amplification to changes in mid-latitude circulation patterns that favor extreme weather events (Francis and Vavrus, 2012). Here we analyze greenhouse-forced projections from the Community Climate System Model (CCSM4) to assess the future evolution of Arctic change on Northern Hemisphere weather patterns. We hypothesize that remote impacts of changes in the energy budget of the Arctic surface will influence the atmospheric circulation in middle latitudes through changes in large-scale, deep-tropospheric, meridional thickness gradients that induce generally weaker zonal flow and higher amplitude large-scale waves aloft. Because such features are slow-moving and associated with persistent weather conditions, they favor more frequent and severe extreme weather episodes resulting from prolonged cold-air outbreaks, heat waves, droughts, and heavy precipitation. The primary physical mechanism driving this change is an enhanced and seasonally varying Arctic heating: in fall/winter it is ocean-based due to substantial sea ice loss, while in warmer months it is land-based due to earlier snow melt and reduced soil moisture. Simulations by CCSM4 support our hypothesized linkages, as the projected climate changes depict a seasonally varying circulation response hinging on the enhanced warming and resulting geopotential height increases aloft in the Arctic. During boreal autumn and winter, sea ice loss leads to upper-air height increases mainly over the Arctic Ocean with compensating decreases over mid-latitudes, which reduces the poleward gradient. During spring and summer, however, the band of maximum ridging shifts southward over high-latitude land. This behavior resembles the upper-air circulation changes induced by prescribed reductions in sea ice and snow cover in previous versions of the model. The associated seasonal changes in mid-tropospheric zonal winds exhibit a nearly symmetrical

  13. Mid-Latitude versus Polar-Latitude Transitional Impact Craters: Geometric Properties from Mars Orbiter Laser Altimeter (MOLA) Observations and Viking Images

    NASA Technical Reports Server (NTRS)

    Matias, A.; Garvin, J. B.; Sakimoto, S. E. H.

    1998-01-01

    One intriguing aspect of martian impact crater morphology is the change of crater cavity and ejecta characteristics from the mid-latitudes to the polar regions. This is thought to reflect differences in target properties such as an increasing presence of ice in the polar regions. Previous image-based efforts concerning martian crater morphology has documented some aspects of this, but has been hampered by the lack of adequate topography data. Recent Mars Orbiter Laser Altimeter (MOLA) topographic profiles provide a quantitative perspective for interpreting the detailed morphologies of martian crater cavities and ejecta morphology. This study is a preliminary effort to quantify the latitude-dependent differences in morphology with the goal of identifying target-dependent and crater modification effects from the combined of images and MOLA topography. We combine the available MOLA profiles and the corresponding Viking Mars Digital Image Mosaics (MDIMS), and high resolution Viking Orbiter images to focus on two transitional craters; one on the mid-latitudes, and one in the North Polar region. One MOLA pass (MGS Orbit 34) traverses the center of a 15.9 km diameter fresh complex crater located at 12.8degN 83.8degE on the Hesperian ridge plains unit (Hvr). Viking images, as well as MOLA data, show that this crater has well developed wall terraces and a central peak with 429 m of relative relief. Three MOLA passes have been acquired for a second impact crater, which is located at 69.5degN 41degE on the Vastitas Borealis Formation. This fresh rampart crater lacks terraces and central peak structures and it has a depth af 579 m. Correlation between images and MOLA topographic profiles allows us to construct basic facies maps of the craters. Eight main units were identified, four of which are common on both craters.

  14. Review of Ionospheric Scintillation Models and proposing a Novel Model for Characterizing High Latitude Irregularities

    NASA Astrophysics Data System (ADS)

    Deshpande, K.; Bust, G. S.; Clauer, C. R.

    2013-12-01

    The study of ionospheric scintillations of radio signal involves a problem of electromagnetic (EM) wave propagation in random media and has been a subject of interest for more than last 5 decades. Some of the representative works are by Booker et. al (1950), Ratcliffe (1956), Wernik and Liu (1975), Yeh and Liu (1982), Secan et. al (1995), Costa and Basu (2002), Rino and Carrano (2011). Many of the scintillation models employ a phase screen model introduced by Rino (1979). Beniguel and Hamel (2011) implemented a global ionospheric scintillation model for equatorial regions showing a good agreement of the model with measurements. Implementing these models in the study of ionospheric scintillations of radio signals at high latitudes could be challenging since the path of satellite signal to ground has a variable angle of incidence, in addition to the complicated geometry of magnetic field lines at high latitude and polar regions, and complex magnetosphere-ionosphere coupling mechanisms creating the irregularities. We have developed a high fidelity 3-dimensional Global Positioning System Ionospheric Scintillation Model (3D-GPSISM) which is a full 3D EM wave propagation model to simulate GPS scintillations in high latitude ionosphere. The results from this model can form a basic framework on the use of inverse method to understand the physics of high latitude irregularities using GPS scintillations. We are using our model and an inverse method for selected scintillation observations during 2010 - 2013 from GPS receivers at South Pole, McMurdo and remote stations on Antarctica in conjunction with ancillary observations from SuperDARN, magnetometers, All Sky Imagers etc. We believe that such inverse method can be used to derive certain characteristics of the irregularity causing the scintillations and further achieve an improved understanding of the physics of high latitude irregularities.

  15. Low-latitude ionosphere dynamics as deduced from meridional ionosonde chain: Ionospheric ceiling

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi; Uemoto, Junpei; Tsugawa, Takuya; Supnithi, Pornchai; Ishii, Mamoru; Komolmis, Tharadol

    Interest in the equatorial anomaly in the ionosphere has been focused mostly on f_oF_2, and not much attention was paid to h_mF_2 except for the time rate of change of it in connection with the vertical plasma drift velocity. There have been few climatological studies on h_mF_2 variations associated with development of the equatorial anomaly. In this paper, we revisit the equatorial anomaly in terms of height variations. For this purpose, we analyzed scaled ionogram parameters from three stations located along the magnetic meridian that is a primary component of Southeast Asia low-latitude ionospheric network (SEALION); one at the magnetic equator and the others at conjugate off-equatorial latitudes near 10 degrees magnetic latitude. The daytime h_mF_2 was investigated for each season during the solar minimum period, 2006-2007 and 2009. The peak height increased for approximately 3 hr after sunrise at all locations, as expected from the daytime upward E×B drift. The apparent upward drift ceased before noon at the magnetic equator, while the layer continued to increase at the off-equatorial latitudes, reaching altitudes higher than the equatorial height around noon. The noon time restricted layer height at the magnetic equator did not depend much on the season, while the maximum peak height at the off-equatorial latitudes largely varied with season. The daytime specific limiting height of the equatorial ionosphere was termed ionospheric ceiling. Numerical modeling using the SAMI2 code reproduced the features of the ionospheric ceiling quite well. Dynamic parameters provided by the SAMI2 modeling were investigated and it was shown that the ionospheric ceiling is another aspect of the fountain effect, in which increased diffusion of plasma at higher altitudes has a leading role.

  16. Climate Effects on High Latitude Daphnia via Food Quality and Thresholds.

    PubMed

    Przytulska, Anna; Bartosiewicz, Maciej; Rautio, Milla; Dufresne, France; Vincent, Warwick F

    2015-01-01

    Climate change is proceeding rapidly at high northern latitudes and may have a variety of direct and indirect effects on aquatic food webs. One predicted effect is the potential shift in phytoplankton community structure towards increased cyanobacterial abundance. Given that cyanobacteria are known to be a nutritionally poor food source, we hypothesized that such a shift would reduce the efficiency of feeding and growth of northern zooplankton. To test this hypothesis, we first isolated a clone of Daphnia pulex from a permafrost thaw pond in subarctic Québec, and confirmed that it was triploid but otherwise genetically similar to a diploid, reference clone of the same species isolated from a freshwater pond in southern Québec. We used a controlled flow-through system to investigate the direct effect of temperature and indirect effect of subarctic picocyanobacteria (Synechococcus) on threshold food concentrations and growth rate of the high latitude clone. We also compared the direct effect of temperature on both Daphnia clones feeding on eukaryotic picoplankton (Nannochloropsis). The high latitude clone had a significantly lower food threshold for growth than the temperate clone at both 18 and 26°C, implying adaptation to lower food availability even under warmer conditions. Polyunsaturated fatty acids were present in the picoeukaryote but not the cyanobacterium, confirming the large difference in food quality. The food threshold for growth of the high latitude Daphnia was 3.7 (18°C) to 4.2 (26°C) times higher when fed Synechococcus versus Nannochloropsis, and there was also a significant negative effect of increased temperature and cyanobacterial food on zooplankton fatty acid content and composition. The combined effect of temperature and food quality on the performance of the high latitude Daphnia was greater than their effects added separately, further indicating the potentially strong indirect effects of climate warming on aquatic food web processes. PMID

  17. F2 region response to geomagnetic disturbances across Indian latitudes: O(1S) dayglow emission

    NASA Astrophysics Data System (ADS)

    Upadhayaya, A. K.; Gupta, Sumedha; Brahmanandam, P. S.

    2016-03-01

    The morphology of ionospheric storms has been investigated across equatorial and low latitudes of Indian region. The deviation in F2 region characteristic parameters (foF2 and h'F) along with modeled green line dayglow emission intensities is examined at equatorial station Thiruvananthapuram (8.5°N, 76.8°E, 0.63°S geomagnetic latitude) and low-latitude station Delhi (28.6°N, 77.2°E,19.2°N geomagnetic latitude) during five geomagnetic storm events. Both positive and negative phases have been noticed in this study. The positive storm phase over equatorial station is found to be more frequent, while the drop in ionization in most of the cases was observed at low-latitude station. It is concluded that the reaction as seen at different ionospheric stations may be quite different during the same storm depending on both the geographic and geomagnetic coordinates of the station, storm intensity, and the storm onset time. Modulation in the F2 layer critical frequency at low and equatorial stations during geomagnetic disturbance of 20-23 November 2003 was caused by the storm-induced changes in O/N2. It is also found that International Reference Ionosphere 2012 model predicts the F2 layer characteristic (foF2 and h'F) parameters at both the low and equatorial stations during disturbed days quite reasonably. A simulative approach in GLOW model developed by Solomon is further used to estimate the changes in the volume emission rate of green line dayglow emission under quiet and strong geomagnetic conditions. It is found that the O(1S) dayglow thermospheric emission peak responds to varying geomagnetic conditions.

  18. Tracking Jupiter’s Quasi-Quadrennial Oscillation and Mid-Latitude Zonal Waves: Initial Results

    NASA Astrophysics Data System (ADS)

    Greathouse, Thomas K.; Orton, Glenn S.; Morales-Juberias, Raul; Fletcher, Leigh N.; DeWitt, Curtis N.; Cosentino, Rick; Richter, Matthew J.; Lacy, John H.

    2014-11-01

    We report on initial results of a long term observational study to track the temporal and 3-dimensional evolution of the Quasi-Quadrennial Oscillation (QQO) and the propagation and evolution of mid-latitude zonal waves in Jupiter’s stratosphere. These wave-driven phenomena affect variations in Jupiter’s vertical and horizontal temperature field, which can be inferred by measuring methane emission in the thermal infrared at 1245 cm-1. Using TEXES, the Texas Echelon cross-dispersed Echelle Spectrograph, mounted on the NASA Infrared Telescope Facility we observed high-spectral resolution (R=75,000) scan maps of Jupiter’s mid-latitudes in January and October 2012, February 2013, and February 2014. These initial datasets were taken using several different observing strategies in an attempt to optimize efficiency and mapping accuracy in preparation for our prime study period (2014-2019). We will present the zonally averaged inferred thermal structure over ±30° latitude and between 10 and 0.01 mbar, showing the QQO’s downward progression along with inferred 3-dimensional thermal maps (latitude, longitude, pressure) displaying a multitude of vertically isolated waves and eddies. These results set the stage for an unprecedented dataset that will: 1) significantly improve the determination of the period and vertical descent velocity of Jupiter’s QQO and map its 3-dimensional spatial structure; 2) measure the zonal wavenumbers, vertical wavelengths, zonal group velocities and lifetimes of transient mid-latitude waves that are impossible to obtain from historic mid-infrared imaging datasets due to their lack of vertical resolution; and 3) record the thermal state of Jupiter’s stratosphere in detail prior to, during, and after Juno’s prime mission to assist in analysis of Juno Mission observations from the Waves, JIRAM, and UVS instruments.

  19. Climate Effects on High Latitude Daphnia via Food Quality and Thresholds

    PubMed Central

    Przytulska, Anna; Bartosiewicz, Maciej; Rautio, Milla; Dufresne, France; Vincent, Warwick F.

    2015-01-01

    Climate change is proceeding rapidly at high northern latitudes and may have a variety of direct and indirect effects on aquatic food webs. One predicted effect is the potential shift in phytoplankton community structure towards increased cyanobacterial abundance. Given that cyanobacteria are known to be a nutritionally poor food source, we hypothesized that such a shift would reduce the efficiency of feeding and growth of northern zooplankton. To test this hypothesis, we first isolated a clone of Daphnia pulex from a permafrost thaw pond in subarctic Québec, and confirmed that it was triploid but otherwise genetically similar to a diploid, reference clone of the same species isolated from a freshwater pond in southern Québec. We used a controlled flow-through system to investigate the direct effect of temperature and indirect effect of subarctic picocyanobacteria (Synechococcus) on threshold food concentrations and growth rate of the high latitude clone. We also compared the direct effect of temperature on both Daphnia clones feeding on eukaryotic picoplankton (Nannochloropsis). The high latitude clone had a significantly lower food threshold for growth than the temperate clone at both 18 and 26°C, implying adaptation to lower food availability even under warmer conditions. Polyunsaturated fatty acids were present in the picoeukaryote but not the cyanobacterium, confirming the large difference in food quality. The food threshold for growth of the high latitude Daphnia was 3.7 (18°C) to 4.2 (26°C) times higher when fed Synechococcus versus Nannochloropsis, and there was also a significant negative effect of increased temperature and cyanobacterial food on zooplankton fatty acid content and composition. The combined effect of temperature and food quality on the performance of the high latitude Daphnia was greater than their effects added separately, further indicating the potentially strong indirect effects of climate warming on aquatic food web processes. PMID

  20. Growth Pattern Responses to Photoperiod across Latitudes in a Northern Damselfly

    PubMed Central

    Śniegula, Szymon; Nilsson-Örtman, Viktor; Johansson, Frank

    2012-01-01

    Background Latitudinal clines in temperature and seasonality impose strong seasonal constraints on ectotherms. Studies of population differentiation in phenotypic plasticity of life history traits along latitudinal gradients are important for understanding how organisms have adapted to seasonal environments and predict how they respond to climate changes. Such studies have been scarce for species with a northern distribution. Methodology/Principle Finding Larvae of the northern damselfly Coenagrion johanssoni originating from semivoltine central, partivoltine northern, and partivoltine northernmost Swedish populations were reared in the laboratory. To investigate whether larvae use photoperiodic cues to induce compensatory growth along this latitudinal gradient, larvae were reared under two different photoperiods corresponding to a northern and southern latitude. In addition, field adult size was assessed to test the strength of possible compensatory growth mechanisms under natural conditions and hatchling size was measured to test for maternal effects. We hypothesized that populations originating from lower latitudes would be more time constrained than high-latitude populations because they have a shorter life cycle. The results showed that low-latitude populations had higher growth rates in summer/fall. In general northern photoperiods induced higher growth rates, but this plastic response to photoperiod was strongest in the southernmost populations and negligible in the northernmost population. During spring, central populations grew faster under the southern rather than the northern photoperiod. On the other hand, northern and northernmost populations did not differ between each other and grew faster in the northern rather than in the southern photoperiod. Field sampled adults did not differ in size across the studied regions. Conclusion/Significance We found a significant differentiation in growth rate across latitudes and latitudinal difference in growth rate

  1. Interaction of mid-latitude air masses with the polar dome area during RACEPAC and NETCARE

    NASA Astrophysics Data System (ADS)

    Bozem, Heiko; Hoor, Peter; Koellner, Franziska; Kunkel, Daniel; Schneider, Johannes; Schulz, Christiane; Herber, Andreas; Borrmann, Stephan; Wendisch, Manfred; Ehrlich, Andre; Leaitch, Richard; Willis, Megan; Burkart, Julia; Thomas, Jennie; Abbatt, Jon

    2016-04-01

    We present aircraft based trace gas measurements in the Arctic during RACEPAC (2014) and NETCARE (2014 and 2015) with the Polar 6 aircraft of Alfred Wegener Institute (AWI) covering an area from 134°W to 17°W and 68°N to 83°N. We focus on cloud, aerosol and general transport processes of polluted air masses into the high Arctic. Based on CO and CO2 measurements and kinematic 10-day back trajectories as well as Flexpart particle dispersion modeling we analyze the transport regimes of mid-latitude air masses traveling to the high Arctic prevalent during spring (RACEPAC 2014, NETCARE 2015) and summer (NETCARE 2014). In general more northern parts of the high Arctic (Lat > 75°N) were relatively unaffected from mid-latitude air masses. In contrast, regions further south are influenced by air masses from Asia and Russia (eastern part of Canadian Arctic and European Arctic) as well as from North America (central and western parts of Canadian Arctic). The transition between the mostly isolated high Arctic and more southern regions indicated by tracer gradients is remarkably sharp. This allows for a chemical definition of the Polar dome based on the variability of CO and CO2 as a marker. Isentropic surfaces that slope from the surface to higher altitudes in the high Arctic form the polar dome that represents a transport barrier for mid-latitude air masses to enter the lower troposphere in the high Arctic. Synoptic-scale weather systems frequently disturb this transport barrier and foster the exchange between air masses from the mid-latitudes and polar regions. This can finally lead to enhanced pollution levels in the lower polar troposphere. Mid-latitude pollution plumes from biomass burning or flaring entering the polar dome area lead to an enhancement of 30% of the observed CO mixing ratio within the polar dome area.

  2. Soil frost-induced soil moisture precipitation feedback over high northern latitudes

    NASA Astrophysics Data System (ADS)

    Hagemann, Stefan; Blome, Tanja; Ekici, Altug; Beer, Christian

    2016-02-01

    Permafrost or perennially frozen ground is an important part of the terrestrial cryosphere; roughly one quarter of Earth's land surface is underlain by permafrost. The impact of the currently observed warming, which is projected to persist during the coming decades due to anthropogenic CO2 input, certainly has effects for the vast permafrost areas of the high northern latitudes. The quantification of these effects, however, is scientifically still an open question. This is partly due to the complexity of the system, where several feedbacks are interacting between land and atmosphere, sometimes counterbalancing each other. Moreover, until recently, many global circulation models (GCMs) and Earth system models (ESMs) lacked the sufficient representation of cold region physical soil processes in their land surface schemes, especially of the effects of freezing and thawing of soil water for both energy and water cycles. Therefore, it will be analysed in the present study how these processes impact large-scale hydrology and climate over northern hemisphere high latitude land areas. For this analysis, the atmosphere-land part of MPI-ESM, ECHAM6-JSBACH, is driven by prescribed observed SST and sea ice in an AMIP2-type setup with and without newly implemented cold region soil processes. Results show a large improvement in the simulated discharge. On one hand this is related to an improved snowmelt peak of runoff due to frozen soil in spring. On the other hand a subsequent reduction of soil moisture leads to a positive land atmosphere feedback to precipitation over the high latitudes, which reduces the model's wet biases in precipitation and evapotranspiration during the summer. This is noteworthy as soil moisture - atmosphere feedbacks have previously not been in the research focus over the high latitudes. These results point out the importance of high latitude physical processes at the land surface for the regional climate.

  3. Global, low-latitude, vertical E × B drift velocities inferred from daytime magnetometer observations

    NASA Astrophysics Data System (ADS)

    Anderson, David; Anghel, Adela; Chau, Jorge L.; Yumoto, Kiyohumi

    2006-08-01

    Navigation and communication, Department of Defense and civilian, customers rely on accurate, low-latitude specification of ionospheric parameters, globally, that are not currently realistic on a day-to-day basis. This paper describes, demonstrates, and speculates about the data sets that are required inputs to the operational ionospheric models that will correct these deficiencies. In order to investigate quiet time, vertical E × B drift velocities at two different longitude sectors, magnetometer observations were obtained for the period between January 2001 and December 2004 from the magnetometers at Jicamarca (0.8°N dip latitude) and Piura (6.8°N dip latitude) in Peru and from Davao (1.4°S dip latitude) and Muntinlupa (6.3°N dip latitude) in the Philippine sector. We choose only geomagnetically "quiet" days, when the 3-hourly Kp value never exceeds a value of 3 over the entire day, and when the daily Ap value is less than 10. These are "binned" into three seasons, December solstice, equinox, and June solstice periods. A neural network trained for the Peruvian sector was applied to each of the days in both the Peruvian and Philippine sectors, providing ΔH-inferred vertical E × B drift velocities between 0700 and 1700 local time. For each season, the average E × B drift velocity curves are compared with the Fejer-Scherliess, climatological E × B drift velocity curves in both the Peruvian and Philippine sectors. In the Peruvian sector, the comparisons are excellent, and in the Philippine sector they are very good. We demonstrate that realistic magnetometer-inferred E × B drifts can be obtained in the Peruvian sector on a day-to-day basis and speculate that on the basis of the average, quiet day comparisons, realistic E × B drifts can be obtained on quiet days in the Philippine sector.

  4. Ungulate Reproductive Parameters Track Satellite Observations of Plant Phenology across Latitude and Climatological Regimes

    PubMed Central

    Stoner, David C.; Sexton, Joseph O.; Nagol, Jyoteshwar; Bernales, Heather H.; Edwards, Thomas C.

    2016-01-01

    The effect of climatically-driven plant phenology on mammalian reproduction is one key to predicting species-specific demographic responses to climate change. Large ungulates face their greatest energetic demands from the later stages of pregnancy through weaning, and so in seasonal environments parturition dates should match periods of high primary productivity. Interannual variation in weather influences the quality and timing of forage availability, which can influence neonatal survival. Here, we evaluated macro-scale patterns in reproductive performance of a widely distributed ungulate (mule deer, Odocoileus hemionus) across contrasting climatological regimes using satellite-derived indices of primary productivity and plant phenology over eight degrees of latitude (890 km) in the American Southwest. The dataset comprised > 180,000 animal observations taken from 54 populations over eight years (2004–2011). Regionally, both the start and peak of growing season (“Start” and “Peak”, respectively) are negatively and significantly correlated with latitude, an unusual pattern stemming from a change in the dominance of spring snowmelt in the north to the influence of the North American Monsoon in the south. Corresponding to the timing and variation in both the Start and Peak, mule deer reproduction was latest, lowest, and most variable at lower latitudes where plant phenology is timed to the onset of monsoonal moisture. Parturition dates closely tracked the growing season across space, lagging behind the Start and preceding the Peak by 27 and 23 days, respectively. Mean juvenile production increased, and variation decreased, with increasing latitude. Temporally, juvenile production was best predicted by primary productivity during summer, which encompassed late pregnancy, parturition, and early lactation. Our findings offer a parsimonious explanation of two key reproductive parameters in ungulate demography, timing of parturition and mean annual production

  5. Latitude-Dependent Effects in the Stellar Wind of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Smith, Nathan; Davidson, Kris; Gull, Theodore R.; Ishibashi, Kazunori; Hillier, D. John

    2002-01-01

    The Homunculus reflection nebula around eta Carinae provides the rare opportunity to observe the spectrum of a star from more than one direction. In the case of eta Car, the nebula's geometry is known well enough to infer how wind profiles vary with latitude. We present STIS spectra of several positions in the Homunculus, showing directly that eta Car has an aspherical and axisymmetric stellar wind. P Cygni absorption in Balmer lines depends on latitude, with relatively high velocities and strong absorption near the polar axis. Stronger absorption at high latitudes is surprising, and it suggests higher mass flux toward the poles, perhaps resulting from equatorial gravity darkening on a rotating star. Reflected profiles of He I lines are more puzzling, and offer clues to eta Car's wind geometry and ionization structure. During eta Car's high-excitation state in March 2000, the wind had a fast, dense polar wind, with higher ionization at low latitudes. Older STIS data obtained since 1998 reveal that this global stellar-wind geometry changes during eta Car's 5.5 year cycle, and may suggest that this star s spectroscopic events are shell ejections. Whether or not a companion star triggers these outbursts remains ambiguous. The most dramatic changes in the wind occur at low latitudes, while the dense polar wind remains relatively undisturbed during an event. The apparent stability of the polar wind also supports the inferred bipolar geometry. The wind geometry and its variability have critical implications for understanding the 5.5 year cycle and long-term variability, but do not provide a clear alternative to the binary hypothesis for generating eta Car s X-rays.

  6. First Tomographic Observations of the Mid-latitude Summer Nighttime Anomaly (MSNA) over Japan

    NASA Astrophysics Data System (ADS)

    Yamamoto, M.; Thampi, S.; Lin, C.; Liu, H.

    2009-12-01

    Recently, a chain of digital beacon receivers has been established over Japan, mainly for the tomographic imaging of the ionosphere. These receivers are installed at Shionomisaki (33.45°N, 135.8°E), Shigaraki (34.85°N, 136.1°E) and Fukui (36.06°N,136°E), which continuously track the Low Earth Orbiting Satellites (LEOS), and the simultaneous line-of-sight relative Total Electron Content (TEC) data are used for tomographic reconstruction. In the images obtained during July 2008, it is seen that the nighttime electron densities exceed the daytime values on almost all days over latitudes >33-34°N. On several days, these northern latitudes show enhanced electron densities compared to the low-latitude region during nighttime. These are the prominent features of the ‘Mid-latitude Summer Nighttime Anomaly (MSNA)’ that is recently observed in the northern hemisphere and is considered similar to the nighttime Weddell Sea Anomaly (WSA). This is the first study of the MSNA using tomographic technique, and found its significant day-to-day variability. The Formosat3/COSMIC occultation measurements, ionosonde data from Wakkanai (45.4°N, 141.7° E), ground-based GPS TEC observations using the GEONET, and CHAMP in situ electron density measurements are also used to confirm the presence of MSNA over this region and to examine its variability. It is seen that in general, during the local summer period, electron density over the northern latitudes is highest at ~2000-2100 LT and the latitudinal enhancement in electron density also begins to appear around the same time, which continues to exist even at later hours. This feature is explained by considering the neutral wind effect in the geomagnetic frame.

  7. Ungulate Reproductive Parameters Track Satellite Observations of Plant Phenology across Latitude and Climatological Regimes.

    PubMed

    Stoner, David C; Sexton, Joseph O; Nagol, Jyoteshwar; Bernales, Heather H; Edwards, Thomas C

    2016-01-01

    The effect of climatically-driven plant phenology on mammalian reproduction is one key to predicting species-specific demographic responses to climate change. Large ungulates face their greatest energetic demands from the later stages of pregnancy through weaning, and so in seasonal environments parturition dates should match periods of high primary productivity. Interannual variation in weather influences the quality and timing of forage availability, which can influence neonatal survival. Here, we evaluated macro-scale patterns in reproductive performance of a widely distributed ungulate (mule deer, Odocoileus hemionus) across contrasting climatological regimes using satellite-derived indices of primary productivity and plant phenology over eight degrees of latitude (890 km) in the American Southwest. The dataset comprised > 180,000 animal observations taken from 54 populations over eight years (2004-2011). Regionally, both the start and peak of growing season ("Start" and "Peak", respectively) are negatively and significantly correlated with latitude, an unusual pattern stemming from a change in the dominance of spring snowmelt in the north to the influence of the North American Monsoon in the south. Corresponding to the timing and variation in both the Start and Peak, mule deer reproduction was latest, lowest, and most variable at lower latitudes where plant phenology is timed to the onset of monsoonal moisture. Parturition dates closely tracked the growing season across space, lagging behind the Start and preceding the Peak by 27 and 23 days, respectively. Mean juvenile production increased, and variation decreased, with increasing latitude. Temporally, juvenile production was best predicted by primary productivity during summer, which encompassed late pregnancy, parturition, and early lactation. Our findings offer a parsimonious explanation of two key reproductive parameters in ungulate demography, timing of parturition and mean annual production, across

  8. Experimental investigation of mechanisms of mid-latitude ionosphere and geophysical fields perturbation

    NASA Astrophysics Data System (ADS)

    Gavrilov, Boris; Zetzer, Julius; Egorov, Dmitry

    The investigations are carried out to study mechanisms and channels of the mid-latitude ionosphere, near-Earth electric field and current perturbations, and their connection to high-latitude and magnetospheric events. The basis of these investigations is a measurement of the geophysical fields in the Geophysical Observatory Mikhnevo (54.9 N, 37,8 E) of the Institute of Geospheres Dynamics RAS situated at 80 km to the south from Moscow. The observatory includes a set of measuring complexes for radiophysics, magnetic, electrical, optic, infrasound, seismic, and other investigations. All of them are controlled by the united computer centre in the common scale of time. Our approach bases on well known conception that the main reasons of the mid-latitude perturbations are the processes in the auroral regions. But auroral phenomena impact on mid-latitudes by means of different physical mechanisms and agents of disturbances. Fortunately, they differ from each other in the time of their generation and velocities of their propagation. For example, the typical velocity of propagation of thermosphere winds is about 100 m/s, the acoustic gravity wave propagate with a velocity of about 400 m/s, and a prompt penetration of the magnetospheric electric field affects the mid-latitude practically instantly. If we can determine a time lag between the action of the perturbation source and mid-latitude ionosphere response, we can determine the velocity of perturbation propagation and recognize the dominating mechanisms and channels of disturbances. The important requirements for the organization of such investigation is a positioning of different measuring facilities in one place and organization of coordinated and synchronous registration of the ionosphere parameters and geophysical fields variations with high temporal resolution. The Mikhnevo observatory gives us such ability. As an indicator and marker of high latitude events (magnetic storms and substorms) we use AE-index. The

  9. Carbon Exchange in the Northern High Latitude Terrestrial Ecosystems Over the Last Three Decades

    NASA Astrophysics Data System (ADS)

    Jain, Atul; El-Masri, Bassil; Barman, Rahul

    2013-04-01

    The dynamics of carbon fluxes in the permafrost region is likely to have tremendous impacts for the future global climate. Recently, several ecosystem and land surface models have demonstrated improved permafrost modeling capabilities by incorporating deep soil layers, organic soils, and parameterizing the effects of wind compaction and depth hoar formations, which influence high latitude soil biogeophysics. However, no global study has yet incorporated the combined effects of these biogeophysical improvements. Additionally, the primary focus has been on modeling biogeophysical fluxes rather than on how biogeochemical processes and feedbacks are impacted. In this study, we evaluate how biogeochemistry (carbon and nitrogen dynamics) responds to improved biogeophysics in the high latitudes. We employ a land surface model, the Integrated Science Assessment Model (ISAM), to model the fluxes of water, energy and carbon, as well as the change in active layer depths during the historical period. The ISAM represents fully prognostic carbon and nitrogen cycles, coupled with biogeophysics schemes. Additionally, biogeophysical improvements such as the inclusion of deep soils, organic soils, wind compaction and depth hoar formation effects, which are critical for high-latitude soil thermal dynamics, have been incorporated into the model. The performance of the model is evaluated using observations for active layer depths and carbon fluxes, together with recent estimates for total soil carbon amount in the permafrost region. The soil decomposition module in the ISAM was calibrated with field experiment data, which includes representation of nitrogen mineralization processes.The ISAM modeled carbon, nitrogen and energy fluxes were evaluated for several flux tower sites representative of the tundra and the boreal ecosystems as well as for the northern high latitude region. This is one of the first studies to explore the combined effects of improvements in biogeophysics, coupled

  10. Paleosecular variation analysis of high-latitude paleomagnetic data from the volcanic island of Jan Mayen

    NASA Astrophysics Data System (ADS)

    Cromwell, G.; Tauxe, L.; Staudigel, H.; Pedersen, L. R.; Constable, C.; Pedersen, R.; Duncan, R. A.; Staudigel, P.

    2009-12-01

    Recent investigation of high-latitude paleomagnetic data from the Erebus Volcanic Province (EVP), Antarctica shows a departure from magnetic dipole predictions for paleointensity data for the period 0-5 Ma. The average EVP paleointensity (31.5 +/- 2.4 μT) is equivalent to low-latitude measurements (1) or approximately half the strength predicted for a dipole at high-latitude. Also, paleosecular variation models (e.g., 2,3) predict dispersions of directions that are much lower than the high latitude observations. Observed low intensity values may be the result of reduced convective flow inside the tangent cylinder of the Earth’s core or insufficient temporal sampling (1). More high-latitude paleomagnetic data are necessary in order to investigate the cause of the depressed intensity values and to provide better geographic and temporal resolution for future statistical paleosecular variation models. To address this, we carried out two field seasons, one in Spitzbergen (79°N, 14°E) and one on the young volcanic island of Jan Mayen (71°N, 8°W). The latter sampling effort was guided by age analyses of samples obtained by P. Imsland (unpublished and 4). We will present new paleodirectional and paleointensity data from a total of 25 paleomagnetic sites. These data enhance the temporal resolution of global paleomagnetic data and allow for a more complete evaluation of the time-averaged magnetic field from 0-5 Ma. We will present a new analysis of paleosecular variation based on our new data, in combination with other recently published data sets. (1) Lawrence, K.P., L.Tauxe, H. Staudigel, C.G. Constable, A. Koppers, W. MacIntosh, C.L. Johnson, Paleomagnetic field properties at high southern latitude. Geochemistry Geophysics Geosystems 10 (2009). (2) McElhinny, M.W., P.L. McFadden, Paleosecular variation over the past 5 Myr based on a new generalized database. Geophysics Journal International 131 (1997), 240-252. (3) Tauxe, L., Kent, D.V., A simplified statistical

  11. Upper mesospheric lunar tides over middle and high latitudes during sudden stratospheric warming events

    NASA Astrophysics Data System (ADS)

    Chau, J. L.; Hoffmann, P.; Pedatella, N. M.; Matthias, V.; Stober, G.

    2015-04-01

    In recent years there have been a series of reported ground- and satellite-based observations of lunar tide signatures in the equatorial and low latitude ionosphere/thermosphere around sudden stratospheric warming (SSW) events. This lower atmosphere/ionosphere coupling has been suggested to be via the E region dynamo. In this work we present the results of analyzing 6 years of hourly upper mesospheric winds from specular meteor radars over a midlatitude (54°N) station and a high latitude (69°N) station. Instead of correlating our results with typical definitions of SSWs, we use the definition of polar vortex weaking (PVW) used by Zhang and Forbes. This definition provides a better representation of the strength in middle atmospheric dynamics that should be responsible for the waves propagating to the E region. We have performed a wave decomposition on hourly wind data in 21 day segments, shifted by 1 day. In addition to the radar wind data, the analysis has been applied to simulations from Whole Atmosphere Community Climate Model Extended version and the thermosphere-ionosphere-mesosphere electrodynamics general circulation model. Our results indicate that the semidiurnal lunar tide (M2) enhances in northern hemispheric winter months, over both middle and high latitudes. The time and magnitude of M2 are highly correlated with the time and associated zonal wind of PVW. At middle/high latitudes, M2 in the upper mesosphere occurs after/before the PVW. At both latitudes, the maximum amplitude of M2 is directly proportional to the strength of PVW westward wind. We have found that M2 amplitudes could be comparable to semidiurnal solar tide amplitudes, particularly around PVW and equinoxes. Besides these general results, we have also found peculiarities in some events, particularly at high latitudes. These peculiarities point to the need of considering the longitudinal features of the polar stratosphere and the upper mesosphere and lower thermosphere regions. For

  12. The Role of Vegetation In High-Latitude Warming During the Latest Cretaceous

    NASA Astrophysics Data System (ADS)

    Shellito, L. J.; Upchurch, G. R.; Shields, C. A.; Kiehl, J. T.

    2010-12-01

    We present results from new climate modeling experiments that evaluate the role of vegetation in maintaining high latitude warmth during the latest Cretaceous (Maastrichtian). We employed the NCAR Community Climate System Model (CCSM) (v.4) with Cretaceous topography and 2x preindustrial CO2 in two sets of experiments. One set of experiments compared climate in two scenarios, one with Cretaceous vegetation (VEG) reconstructed from the fossil and pollen record and another with bare ground (BG). The second set of experiments was similar but used modified liquid clouds to simulate the effect of reduced cloud condensation nuclei in the pre-anthropogenic world. In the first set of experiments, vegetation increases global mean annual temperature by 2°C. Northern high latitude and Arctic mean annual temperatures warm by 8-10°C, while Antarctica warms by 3-6°C. The VEG scenario warms the northern high latitudes sufficiently to inhibit the formation of Arctic sea by more than 50%, due to reduced albedo and enhanced greenhouse effect resulting from higher atmospheric water vapor. Overall, vegetation and reduced sea ice have the effect of reducing global albedo by 2%, accounting for much of the temperature difference between the VEG and BG experiments. However, temperatures in the Arctic and Northern Hemisphere high latitudes are too low relative to proxies, and the latitudinal gradient of temperature is too steep. In the second set of experiments, vegetation increases global mean annual temperature by only 1°C. Pre-anthropogenic liquid clouds increase global mean annual temperature by 5°C in the bare-ground case and 4°C in the vegetated case. The increase in radiative forcing from pre-anthropogenic liquid clouds eliminates nearly all sea ice in both experiments. Mean annual temperature at high latitudes and in the Arctic matches the record of climate proxies, as does the latitudinal gradient of temperature. Given an estimated value of atmospheric pCO2 of ~500 ppm for

  13. Toward improving the representation of the water cycle at High Northern Latitudes

    NASA Astrophysics Data System (ADS)

    Lahoz, William; Svendby, Tove; Hamer, Paul; Blyverket, Jostein; Kristiansen, Jørn; Luijting, Hanneke

    2016-04-01

    The rapid warming at northern latitude regions in recent decades has resulted in a lengthening of the growing season, greater photosynthetic activity and enhanced carbon sequestration by the ecosystem. These changes are likely to intensify summer droughts, tree mortality and wildfires. A potential major climate change feedback is the release of carbon-bearing compounds from soil thawing. These changes make it important to have information on the land surface (soil moisture and temperature) at high northern latitude regions. The availability of soil moisture measurements from several satellite platforms provides an opportunity to address issues associated with the effects of climate change, e.g., assessing multi-decadal links between increasing temperatures, snow cover, soil moisture variability and vegetation dynamics. The relatively poor information on water cycle parameters for biomes at northern high latitudes make it important that efforts are expended on improving the representation of the water cycle at these latitudes. In a collaboration between NILU and Met Norway, we evaluate the soil moisture observations over Norway from the ESA satellite SMOS (Soil Moisture and Ocean Salinity) using in situ ground based soil moisture measurements, with reference to drought and flood episodes. We will use data assimilation of the quality-controlled SMOS soil moisture observations into a land surface model and a numerical weather prediction model to assess the added value from satellite observations of soil moisture for improving the representation of the water cycle at high northern latitudes. This presentation provides first results from this work. We discuss the evaluation of SMOS soil moisture data (and from other satellites) against ground-based in situ data over Norway; the performance of the SMOS soil moisture data for selected drought and flood conditions over Norway; and the first results from data assimilation experiments with land surface models and numerical

  14. A High-Latitude Winter Continental Low Cloud Feedback Suppresses Arctic Air Formation in Warmer Climates

    NASA Astrophysics Data System (ADS)

    Cronin, T.; Tziperman, E.; Li, H.

    2015-12-01

    High latitude continents have warmed much more rapidly in recent decades than the rest of the globe, especially in winter, and the maintenance of warm, frost-free conditions in continental interiors in winter has been a long-standing problem of past equable climates. It has also been found that the high-latitude lapse rate feedback plays an important role in Arctic amplification of climate change in climate model simulations, but we have little understanding of why lapse rates at high latitudes change so strongly with warming. To better understand these problems, we study Arctic air formation - the process by which a high-latitude maritime air mass is advected over a continent during polar night, cooled at the surface by radiation, and transformed into a much colder continental polar air mass - and its sensitivity to climate warming. We use a single-column version of the WRF model to conduct two-week simulations of the cooling process across a wide range of initial temperature profiles and microphysics schemes, and find that a low cloud feedback suppresses Arctic air formation in warmer climates. This cloud feedback consists of an increase in low cloud amount with warming, which shields the surface from radiative cooling, and increases the continental surface air temperature by roughly two degrees for each degree increase of the initial maritime surface air temperature. The time it takes for the surface air temperature to drop below freezing increases nonlinearly to ~10 days for initial maritime surface air temperatures of 20 oC. Given that this is about the time it takes an air mass starting over the Pacific to traverse the north American continent, this suggests that optically thick stratus cloud decks could help to maintain frost-free winter continental interiors in equable climates. We find that CMIP5 climate model runs show large increases in cloud water path and surface cloud longwave forcing in warmer climates, consistent with the proposed low-cloud feedback

  15. Origin and evolution of sinkholes in an alluvial setting: the case study of Piano dell'Acqua (San Basile, Northern Calabria, Italia)

    NASA Astrophysics Data System (ADS)

    Iovine, Giulio G. R.; Parise, Mario; Caloiero, Tommaso; Ferraro, Giuseppe; Lanza, Giuseppe; Nicolino, Nicola; Suriano, Stefania

    2010-05-01

    Five sinkholes have recently been identified at "Piano dell'Acqua", in the territory of San Basile (Northern Calabria, Southern Italy). They are located in a hilly setting, where the main landform is represented by a slight valley draining toward the east. The sinkholes are limited in size, with maximum diameter of 10 m, and maximum depth of 2.5 m. Two of them present elongated shapes, whilst the remaining three are circular. The area where the sinkholes developed is characterized by Pliocene conglomerate and sand, dislocated by tectonic lines. Sinkhole phenomena were initially investigated in the whole territory by means of multi-temporal aerial photos; the outcomes from this analysis were checked in the field through geological, structural and geomorphological surveys. Historical analysis was started in order to collect and critically evaluate the existing information and testimonies about the age of occurrence of the surveyed phenomena; several interviews with local inhabitants were performed, and a number of archives scrutinized. As a result, it may be assumed that two out of the five identified sinkholes developed during the winter 2000-2001 (period "a"), with likely rapid formation; two of the other cases probably originated during the 70's (period "b"), as also suggested by the age of the vegetation hosted within the sinkholes; c) the last sinkhole opened sometime between February 2001 and November 2007 (period "c"). According to the collected testimonies, a further phase of sinkhole development might have occurred in the first half of the past Centruty, but no field evidence of this older phase has been found. Analysis of the seismic catalogues showed that no earthquake can be identified as possible trigger of any of the sinkholes at Piano dell'Acqua. Therefore, the origin of the studied phenomena may be related to sub-cutaneous erosion, within an area that is rich in groundwater. Local changes in the water table, both related to climate and man

  16. High and Mid-Latitude Wetlands, Climate Change, and Carbon Storage

    NASA Technical Reports Server (NTRS)

    Peteet, Dorothy

    2000-01-01

    Pollen and macrofossil stratigraphy from wetlands associated with AMS chronology provides a vegetational and climatic history over thousands of years. From these records we establish a record of climate change which can be compared with independent records of carbon accumulation rates in these same wetlands. In this way, inferences can be made concerning carbon storage during different climatic regimes. One focus of our research has been high-latitude regions such as Alaskan and Siberian tundra, from which we have paleorecords which span the last 10,000 years. We will present records from the Malaspina Glacier region, Alaska and the Pur-Taz region of Western Siberia. A second focus of our research is in mid-latitude eastern North America. We will present paleorecords from wetlands in Vermont, New York, and Virginia showing the relationship between carbon accumulation rates and climatic changes since the late Pleistocene.

  17. Sea surface temperature anomalies, planetary waves, and air-sea feedback in the middle latitudes

    NASA Technical Reports Server (NTRS)

    Frankignoul, C.

    1985-01-01

    Current analytical models for large-scale air-sea interactions in the middle latitudes are reviewed in terms of known sea-surface temperature (SST) anomalies. The scales and strength of different atmospheric forcing mechanisms are discussed, along with the damping and feedback processes controlling the evolution of the SST. Difficulties with effective SST modeling are described in terms of the techniques and results of case studies, numerical simulations of mixed-layer variability and statistical modeling. The relationship between SST and diabatic heating anomalies is considered and a linear model is developed for the response of the stationary atmosphere to the air-sea feedback. The results obtained with linear wave models are compared with the linear model results. Finally, sample data are presented from experiments with general circulation models into which specific SST anomaly data for the middle latitudes were introduced.

  18. Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars

    USGS Publications Warehouse

    Head, J.W.; Neukum, G.; Jaumann, R.; Hiesinger, H.; Hauber, E.; Carr, M.; Masson, P.; Foing, B.; Hoffmann, H.; Kreslavsky, M.; Werner, S.; Milkovich, S.; Van Gasselt, S.

    2005-01-01

    Images from the Mars Express HRSC (High-Resolution Stereo Camera) of debris aprons at the base of massifs in eastern Hellas reveal numerous concentrically ridged lobate and pitted features and related evidence of extremely ice-rich glacier-like viscous flow and sublimation. Together with new evidence for recent ice-rich rock glaciers at the base of the Olympus Mons scarp superposed on larger Late Amazonian debris-covered piedmont glaciers, we interpret these deposits as evidence for geologically recent and recurring glacial activity in tropical and mid-latitude regions of Mars during periods of increased spin-axis obliquity when polar ice was mobilized and redeposited in microenvironments at lower latitudes. The data indicate that abundant residual ice probably remains in these deposits and that these records of geologically recent climate changes are accessible to future automated and human surface exploration.

  19. An Investigation of the Low-Latitude Boundary Layer at Mid-Altitudes in the Cusp

    NASA Technical Reports Server (NTRS)

    Chandler, Michael O.; Avanov, Levon A.

    2006-01-01

    We have begun an investigation of the nature of the low-latitude boundary layer in the mid-altitude cusp region using data from the Polar spacecraft. This region has been routinely sampled for about three months each year for the periods 1999-2001 and 2004-2006. The low-to-mid-energy ion instruments frequently observed dense, magnetosheath-like plasma deep (in terms of distance from the magnetopause and in invariant latitude) in the magnetosphere. We seek to understand the morphology of the LLBL as it projects from the sub-solar region into the cusp and determine the influences on this morphology. An initial survey of the data is ongoing and we present here an overview of our intended study and some preliminary results.

  20. Model of Semidiurnal Pseudo Tide in the High-Latitude Upper Mesosphere

    NASA Technical Reports Server (NTRS)

    Talaat, E. R.; Mayr, H. G.

    2011-01-01

    We present numerical results for the m = 1 meridional winds of semi diurnal oscillations in the high-latitude upper mesosphere, which are generated in the Numerical Spectral Model (NSM) without solar excitations of the tides. Identified with heuristic computer runs, the pseudo tides attain amplitudes that are, at times, as large as the non-migrating tides produced with standard solar forcing. Under the influence of parameterized gravity waves, the nonlinear NSM generates internal oscillations like the quasi-biennial oscillation, that are produced with periods favored by the dynamical properties of the system. The Coriolis force would favor at polar latitudes the excitation of the 12-hour periodicity. This oscillation may help explain the large non-migrating semidiurnal tides that are observed in the region with ground-based and satellite measurements.

  1. The middle and high latitude winter ionosphere at the Ariel 4 satellite altitude

    NASA Technical Reports Server (NTRS)

    Tulunay, Y. K.; Grebowsky, J. M.

    1983-01-01

    The electron (0+) density variations over the northern and southern winter high latitude ionosphere are comprehensively analyzed using the technique of Brinton et al. (1978). Two-hour Magnetic Local Time (MLT) arithmetic means of electron densities are studied in terms of invariant magnetic latitude and in terms of magnetic activity as classified by the three-hour planetary magnetic activity index. It is found that the southern hemisphere densities are significantly lower than those in the northern hemisphere. Further, the maximum electron densities observed in the northern hemisphere are located in a MLT range symmetrical about the 14-02 MLT meridian, whereas in the southern hemisphere the maxima are observed about the noon midnight magnetic meridian. A deep localized ionization hole on the nightside of the polar cap is not observed although the polar cavity is apparent.

  2. Geologic isolation of nuclear waste at high latitudes: the role of ice sheets

    USGS Publications Warehouse

    Person, M.; McIntosh, J.; Iverson, N.; Neuzil, C.E.; Bense, V.

    2012-01-01

    Geologic isolation of high-level nuclear waste from the biosphere requires special consideration in countries at high latitudes (>40°N) owing to the possibility of future episodes of continental glaciation (Talbot 1999). It is now widely recognized that Pleistocene continental glaciations have had a profound effect on rates of sediment erosion (Cuffey & Paterson 2010) and deformation including tectonic thrusting (Pedersen 2005) as well as groundwater flow (Person et al. 2007; Lemieux et al. 2008a,b,c). In addition, glacial mechanical loads may have generated anomalous, or fossil, pore pressures within certain clay-rich confining units (e.g. Vinard et al. 2001). Because high-level nuclear wastes must be isolated from the biosphere as long as 1 million years (McMurry et al. 2003), the likelihood of one or more continental ice sheets overrunning high-latitude sites must be considered.

  3. Mapping electrodynamic features of the high-latitude ionosphere from localized observations - Technique

    NASA Technical Reports Server (NTRS)

    Richmond, A. D.; Kamide, Y.

    1988-01-01

    This paper describes a novel procedure for mapping high-latitude electric fields and currents and their associated magnetic variations, using sets of localized observational data derived from different types of measurements. The technique provides a formalism for incorporating simultaneously such different classes of data as electric fields from radars and satellites, electric currents from radars, and magnetic perturbations at the ground and at satellite heights; the technique also uses available statistical information on the averages and variances of electrodynamic fields. The technique provides a more rigorous way of quantitatively estimating high-latitude electric field and current patterns than other methods and has a capability to quantify the errors in the mapped fields, based on the distribution of available data, their errors, and the statistical variances of the fields. The technique is illustrated by an application to a substorm which was analyzed by Kamide et al. (1982) by an earlier technique.

  4. The influence of polar heterogeneous processes on reactive chlorine at middle latitudes - Three dimensional model implications

    NASA Astrophysics Data System (ADS)

    Douglass, Anne R.; Rood, Richard B.; Kaye, Jack A.; Stolarki, Richard S.; Allen, Dale J.

    1991-01-01

    Three-dimensional model calculations with the NASA/GSFC chemistry and transport model have been designed to consider the impact of heterogeneous processes occurring on polar stratospheric clouds (PSCs) in the Arctic vortex on the HCl distribution. By examining the HCl concentration for a calculation with PSCs relative to a calculation with gas phase chemistry only, the impact of polar processing on reactive chlorine species at middle latitudes is inferred. Results from the chemistry and transport model reproduce basic features of the ClO measurements (Toohey et al., 1991), which were made on the ferry flights of the ER-2 from Stavanger, Norway to Moffett Field, California via Wallops Island, Virginia on February 20 and 21, 1989. The model indicates that perturbed air which is contained within the polar vortex during winter is not homogeneously mixed, and that the ferry flights were made through air with the largest conversion of HCl to reactive chlorine that is seen at middle latitudes.

  5. Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars.

    PubMed

    Holt, John W; Safaeinili, Ali; Plaut, Jeffrey J; Head, James W; Phillips, Roger J; Seu, Roberto; Kempf, Scott D; Choudhary, Prateek; Young, Duncan A; Putzig, Nathaniel E; Biccari, Daniela; Gim, Yonggyu

    2008-11-21

    Lobate features abutting massifs and escarpments in the middle latitudes of Mars have been recognized in images for decades, but their true nature has been controversial, with hypotheses of origin such as ice-lubricated debris flows or glaciers covered by a layer of surface debris. These models imply an ice content ranging from minor and interstitial to massive and relatively pure. Soundings of these deposits in the eastern Hellas region by the Shallow Radar on the Mars Reconnaissance Orbiter reveal radar properties entirely consistent with massive water ice, supporting the debris-covered glacier hypothesis. The results imply that these glaciers formed in a previous climate conducive to glaciation at middle latitudes. Such features may collectively represent the most extensive nonpolar ice yet recognized on Mars. PMID:19023078

  6. Longitudinal Variations of Low-Latitude Gravity Waves and Their Impacts on the Ionosphere

    NASA Astrophysics Data System (ADS)

    Cullens, C. Y.; England, S.; Immel, T. J.

    2014-12-01

    The lower atmospheric forcing has important roles in the ionospheric variability. However, influences of lower atmospheric gravity waves on the ionospheric variability are still not clear due to the simplified gravity wave parameterizations and the limited knowledge of gravity wave distributions. In this study, we aim to study the longitudinal variations of gravity waves and their impacts of longitudinal variations of low-latitude gravity waves on the ionospheric variability. Our SABER results show that longitudinal variations of gravity waves at the lower boundary of TIME-GCM are the largest in June-August and January-February. We have implemented these low-latitude gravity wave variations from SABER instrument into TIME-GCM model. TIME-GCM simulation results of ionospheric responses to longitudinal variations of gravity waves and physical mechanisms will be discussed.

  7. Improvement of Accuracy of Proper Motions of Hipparcos Catalogue Stars Using Optical Latitude Observations

    NASA Astrophysics Data System (ADS)

    Damljanovic, G.

    2009-09-01

    Commission 19 (Earth Rotation) of the International Astronomical Union (IAU) established the Working Group on Earth Rotation in the Hipparcos Reference Frame (WG ERHRF) in 1995 to collect the optical observations of latitude and universal time variations, made during 1899.7 -- 1992.0 in line with the Earth orientation programmes (to derive Earth Orientation Parameters -- EOP), with Dr. Jan Vondrák (Astronomical Institute of Academy of Sciences of the Czech Republic, Prague) as the head of WG ERHRF. We participated in this international project using Belgrade Visual Zenith -- Telescope (BLZ) latitude data for the period 1949.0 -- 1986.0, after a new reduction of BLZ data made in my MSc thesis, finished in 1997 at the Faculty of Mathematics of University of Belgrade. Dr. Vondrák collected 4.4 million optical observations of latitude/universal time variations made at 33 observatories. The data were used for the EOP investigations, Hipparcos satellite Catalogue -- radio sources connection, etc. Nowadays, it is customary to correct the positions and proper motions of stars of Hipparcos Catalogue (as an optical reference frame) using ground -- based observations of some Hipparcos stars. In this PhD thesis we use the latitude observations made with several types of classical astrometric instruments: visual (ZT) and floating zenith -- telescope (FZT), visual zenith tube (VZT) and photographic zenith tube (PZT); 26 different instruments located at many observatories all over the world (used in the programs of monitoring the Earth orientation during the 20th century). We received the data from Dr. Vondrák via private communication. The observatories and instruments are: International Latitude Service -- ILS (Carloforte -- CA ZT, Cincinnati -- CI ZT, Gaithersburg -- GT ZT, Kitab -- KZ ZT, Mizusawa -- MZZ ZT, Tschardjui -- TS ZT and Ukiah -- UK ZT), Belgrade (BLZ ZT), Blagoveschtschensk (BK ZT), Irkutsk (IRZ ZT), Poltava (POL ZT), Pulkovo (PU and PUZ ZT), Varsovie (VJZ ZT

  8. SAS-2 observations of gamma rays from the galactic plane. [noting longitude and latitude observation

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Bignami, G. F.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.

    1974-01-01

    Preliminary data are given for the SAS-2 high energy galactic gamma ray observation. These data include both latitude and longitude distributions. The longitude distribution shows a high density region. The latitude distributions toward the center and the anti-center are markedly different, the former showing a two-component structure of half-widths of approximately 3 and 6 deg. The energy spectrum in the range 35 to 200 MeV is hard, consistent with cosmic ray interactions with interstellar matter, including neutral pions decay and emission from energetic electron interactions. The data is consistent with an interpretation in terms of the confinement of the cosmic rays in the spiral arms.

  9. High latitude f-region drift studies. Technical report, October 1985-September 1986

    SciTech Connect

    Reinisch, B.W.; Buchau, J.; Weber, E.J.; Dozois, C.G.; Bibl, K.

    1986-12-01

    The large-scale, high-latitude ionospheric-convection pattern is driven by the interaction of the solar wind and the interplanetary magnetic field with the earth's magnetosphere. Ground-based digital ionosondes, with spaced receiving antennas, have been developed and deployed at the high latitude stations of Thule, Greenland and Goose Bay, Labrador. Results from these stations demonstrate that the ionospheric convection can be measured for the bottomside ionosphere. Data from Thule consistently show the predominant antisunward convection. The data from Goose Bay indicate the sunward return flows of the polar plasma convection and the switch over when the station rotates from the dusk into the dawn cell. These data also illustrate the potential for systematic study of the convection patterns that is possible with a network of ground-based digital ionosondes.

  10. Proton albedo spectrum observation in low latitude region at Hyderabad, India

    NASA Technical Reports Server (NTRS)

    Verma, S. D.; Kothari, S. K.

    1985-01-01

    The flux and the energy spectrum of low energy (30-100 MeV) proton albedos, have been observed for the first time in a low latitude region, over Hyderabad, India. The preliminary results, based on the quick look data acquisition and display system are presented. A charged particle telescope, capable of distinguishing singly charged particles such as electrons, muons, protons in low energy region, records the data of both upward as well as downward moving particles. Thus spectra of splash and re-entrant albedo protons have been recorded simultaneously in a high altitude Balloon flight carried out on 8th December, 1985, over Hyderabad, India. Balloon floated at an latitude of approx. 37 km (4 mb).

  11. a Study of Ionospheric Low Latitude Velocity and Density Irregularity Correlations during Solar Minimum

    NASA Astrophysics Data System (ADS)

    Haaser, R. A.; Earle, G. D.; Heelis, R. A.; Klenzing, J. H.; Coley, W. R.; Stoneback, R. A.; Burrell, A. B.

    2010-12-01

    The C/NOFS satellite has measured ionospheric plasma density irregularities at low latitudes on scales larger than 10 km over a full set of seasons. The focus of this study is on data from the Ion Velocity Meter (IVM) from Jan-Dec 2009 for pre-midnight and post-midnight times when the data are most reliable. Correlations between the normalized changes in density and velocity (dni/n and dv-horz,vert) during spread-F events (plasma bubbles through the f-peak) and localized plasma enhancements associated with those events are analyzed and compared to investigate seasonal, spatial, and temporal properties during the 2009 solar minimum conditions. The correlations presented and their relationship to the unusually quiescent background conditions in this epoch challenge our understanding and add significantly to our knowledge of ionospheric irregularity events and distribution statistics at low latitudes during solar minimum.

  12. Spatially resolved methane band photometry of Saturn. II - Cloud structure models at four latitudes

    NASA Technical Reports Server (NTRS)

    West, R. A.

    1983-01-01

    Saturn's cloud vertical structures in the Equatorial Zone, South Equatorial Belt, and North and South Temperate Regions near + or - 30 deg latitudes are determined by means of an analysis of spatially resolved reflectivity measurements in the 6190, 7250, and 8996 A methane bands. Radiative transfer models are computed for a structure whose parameters are the methane column abundance in an aerosol-free layer at the top of the atmosphere, and the specific abundance of methane in a semiinfinite homogeneous gas-and-cloud mixture deep in the atmosphere. The structure for the South Equatorial Belt resembles that for the North Temperate Region. The level where unit cloud optical depth occurs in the South Temperate Region is deeper than the corresponding level at other latitudes. The differences between model parameters derived by means of different absorption bands are discussed.

  13. Empirical evidence for latitude dependence and asymmetry of geomagnetic spatial variation in mainland China

    NASA Astrophysics Data System (ADS)

    Lu, Shikun; Zhang, Hao; Li, Xihai; Liu, Daizhi; Wang, Xiqin

    2016-05-01

    Spatiotemporal geomagnetic variation is a significant research topic of geomagnetism and space physics. Generated by convection and flows within the fluid outer core, latitude dependence and asymmetry, as the inherent spatiotemporal properties of geomagnetic field, have been extensively studied. We apply and modify an extension of existing method, Hidden Markov Model (HMM), which is an efficient tool for modeling the statistical properties of time series. Based on ground magnetic measurement data set in mainland China, first, we find the parameters of HMM can be used as the geomagnetic statistical signature to represent the spatiotemporal geomagnetic variations for each site. The results also support the existence of the geomagnetic latitude dependence more apparently. Furthermore, we provide solid empirical evidence for geomagnetic asymmetry relying on such ground magnetic measurement data set.

  14. Ionospheric scintillation modeling for high- and mid-latitude using B-spline technique

    NASA Astrophysics Data System (ADS)

    Priyadarshi, S.

    2015-09-01

    Ionospheric scintillation is a significant component of space-weather studies and serves as an estimate for the level of perturbation in the satellite radio wave signal caused due to small-scale ionospheric irregularities. B-spline functions are used on the GPS ground based data collected during the year 2007-2012 for modeling high- and mid-latitude ionospheric scintillation. Proposed model is for Hornsund, Svalbard and Warsaw, Poland. The input data used in this model were recorded by GSV 4004b receivers. For validation, results of this model are compared with the observation and other existing models. Physical behavior of the ionospheric scintillation during different seasons and geomagnetic conditions are discussed well. Model is found in good coherence with the ionospheric scintillation theory as well as to the accepted scintillation mechanism for high- and mid-latitude.

  15. Direct observation of closed magnetic flux trapped in the high-latitude magnetosphere.

    PubMed

    Fear, R C; Milan, S E; Maggiolo, R; Fazakerley, A N; Dandouras, I; Mende, S B

    2014-12-19

    The structure of Earth's magnetosphere is poorly understood when the interplanetary magnetic field is northward. Under this condition, uncharacteristically energetic plasma is observed in the magnetotail lobes, which is not expected in the textbook model of the magnetosphere. Using satellite observations, we show that these lobe plasma signatures occur on high-latitude magnetic field lines that have been closed by the fundamental plasma process of magnetic reconnection. Previously, it has been suggested that closed flux can become trapped in the lobe and that this plasma-trapping process could explain another poorly understood phenomenon: the presence of auroras at extremely high latitudes, called transpolar arcs. Observations of the aurora at the same time as the lobe plasma signatures reveal the presence of a transpolar arc. The excellent correspondence between the transpolar arc and the trapped closed flux at high altitudes provides very strong evidence of the trapping mechanism as the cause of transpolar arcs. PMID:25525244

  16. Kilometric type 3 radio bursts observed from high southern ecliptic latitudes by Ulysses

    NASA Technical Reports Server (NTRS)

    Reiner, M. J.; Fainberg, J.; Stone, R. G.

    1995-01-01

    The Ulysses URAP experiment has provided the first measurements of remote and in-situ wave phenomena from high southern latitudes. Remote sensing of type 3 solar radio bursts constitute an important component of the Ulysses observations. Type 3 radio emissions, which have never before been viewed from outside the ecplitic plane, have been observed by Ulysses to its maximum southern latitude (approximately 80 deg S), although their frequency of occurrence has generally diminished due to the declining phase of the solar cycle. In addition, the Ulysses radio receiver measures both the direction of arrival and the complete polarization state of incident radiation. These physical parameters provide information on the origin and nature of the radio emission. Preliminary analyses have indicated that kilometric type 3 radiation is often approximately 10-20% circularly polarized at the highest URAP frequencies. New directional information provides crucial information on the effects of beaming and scattering of the radiation in the interplanetary medium.

  17. Effect of sudden solar wind dynamic pressure changes at subauroral latitudes - Change in magnetic field

    NASA Technical Reports Server (NTRS)

    Le, G.; Russell, C. T.; Petrinec, S. M.; Ginskey, M.

    1993-01-01

    The observations obtained during the International Magnetospheric Study (IMS) from the magnetometers of the IGS network extending from Cambridge, England, to Tromso, Norway, are used to study the response of subauroral current systems to sudden changes in solar wind dynamic pressure. Observations show that the response is very strong at subauroral latitudes. The preliminary response in the H component is a brief, small increase in the dayside morning sector and a decrease in the aftenoon and night sectors. The main response in the horizontal field (the H and D components) is toward the pole except in the dayside morning sector. The inferred ionospheric current is mainly a circulatory system flowing counterclockwise when viewed from the north pole everywhere at subauroral latitudes except the dayside morning sector.

  18. Transpolar arc observation after solar wind entry into the high-latitude magnetosphere

    NASA Astrophysics Data System (ADS)

    Mailyan, B.; Shi, Q. Q.; Kullen, A.; Maggiolo, R.; Zhang, Y.; Fear, R. C.; Zong, Q.-G.; Fu, S. Y.; Gou, X. C.; Cao, X.; Yao, Z. H.; Sun, W. J.; Wei, Y.; Pu, Z. Y.

    2015-05-01

    Recently, Cluster observations have revealed the presence of new regions of solar wind plasma entry at the high-latitude magnetospheric lobes tailward of the cusp region, mostly during periods of northward interplanetary magnetic field. In this study, observations from the Global Ultraviolet Imager (GUVI) experiment on board the TIMED spacecraft and Wideband Imaging Camera imager on board the IMAGE satellite are used to investigate a possible link between solar wind entry and the formation of transpolar arcs in the polar cap. We focus on a case when transpolar arc formation was observed twice right after the two solar wind entry events were detected by the Cluster spacecraft. In addition, GUVI and IMAGE observations show a simultaneous occurrence of auroral activity at low and high latitudes after the second entry event, possibly indicating a two-part structure of the continuous band of the transpolar arc.

  19. The X-ray shadow of the high-latitude molecular cloud MBM 12

    NASA Technical Reports Server (NTRS)

    Snowden, S. L.; Mccammon, D.; Verter, F.

    1993-01-01

    ROSAT XRT/PSPC observations show a deep shadow cast by the high-latitude molecular cloud MBM 12 in the 3/4 keV diffuse background. Modeling of the shadow implies that less than 20 percent of the typical high-latitude 3/4 keV diffuse background intensity is emitted in front of the cloud (D = 60-70 pc). A weaker shadow consistent with the lower optical depth at higher energies was observed in the 1.5 keV band. Since little shadowing was seen in the 1/4 keV band, this observation places strong constraints on the amount of 0.5-2 keV emission that is intermixed with the source of the observed 1/4 keV flux.

  20. Homogeneity of coral reef communities across 8 degrees of latitude in the Saudi Arabian Red Sea.

    PubMed

    Roberts, May B; Jones, Geoffrey P; McCormick, Mark I; Munday, Philip L; Neale, Stephen; Thorrold, Simon; Robitzch, Vanessa S N; Berumen, Michael L

    2016-04-30

    Coral reef communities between 26.8 °N and 18.6 °N latitude in the Saudi Arabian Red Sea were surveyed to provide baseline data and an assessment of fine-scale biogeography of communities in this region. Forty reefs along 1100 km of coastline were surveyed using depth-stratified visual transects of fish and benthic communities. Fish abundance and benthic cover data were analyzed using multivariate approaches to investigate whether coral reef communities differed with latitude. A total of 215 fish species and 90 benthic categories were recorded on the surveys. There were no significant differences among locations in fish abundance, species richness, or among several diversity indices. Despite known environmental gradients within the Red Sea, the communities remained surprisingly similar. The communities do, however, exhibit subtle changes across this span of reefs that likely reflect the constrained distributions of several species of reef fish and benthic fauna. PMID:26608504