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NASA NTRS2016

Magnetic-Island Contraction and Particle Acceleration in Simulated Eruptive Solar Flares

The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission in solar flares is not well understood. Drake et al. proposed a mechanism for accelerating electrons in contracting magnetic islands formed by kinetic reconnection in multi-layered current sheets (CSs). We apply these ideas to sunward-moving flux ropes (2.5D magnetic islands) formed during fast reconnection in a simulated eruptive flare. A simple analytic model is used to calculate the energy gain of particles orbiting the field lines of the contracting magnetic islands in our ultrahigh-resolution 2.5D numerical simulation. We find that the estimated energy gains in a single island range up to a factor of five. This is higher than that found by Drake et al. for islands in the terrestrial magnetosphere and at the heliopause, due to strong plasma compression that occurs at the flare CS. In order to increase their energy by two orders of magnitude and plausibly account for the observed high-energy flare emission, the electrons must visit multiple contracting islands. This mechanism should produce sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each magneto hydro dynamic-scale island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare CS is a promising candidate for electron acceleration in solar eruptions.

Guidoni, S. E.↗
NASA NTRS2013

The NASA Meter Class Autonomous Telescope: Ascension Island

The Meter Class Autonomous Telescope (MCAT) is the newest optical sensor dedicated to NASA s mission to characterize the space debris environment. It is the successor to a series of optical telescopes developed and operated by the JSC Orbital Debris Program Office (ODPO) to monitor and assess the debris environment in (1) Low Earth Orbit (LEO), (2) Medium Earth Orbit (MEO), and (3) Geosynchronous Orbit (GEO), with emphasis on LEO and GEO altitudes. A joint NASA-Air Force Research Labs project, MCAT is a 1.3m optical telescope dedicated to debris research. Its optical path and sensor yield a large survey fence at the cutting edge of current detector performance. It has four primary operational observing modes, two of which were not computationally feasible a decade ago. Operations are supported by a sophisticated software suite that monitors clouds and weather conditions, and controls everything from data collection to dome rotation to processing tens of GB of imagery data nightly. With fainter detection limits, precision detection, acquisition and tracking of targets, multi-color photometry, precision astrometry, automated reacquisition capability, and the ability to process all data at the acquisition rate, MCAT is capable of producing and processing a volume and quality of data far in excess of any current (or prior) ODPO operations. This means higher fidelity population inputs and eliminating the multi-year backlog from acquisition-to-product typical of optical campaigns. All of this is possible given a suitable observing location. Originally planned for the island of Legan, part of the Kwajalein Atoll Islands, recent developments have led to a change in venue. Specifically, the Ground-based Electro-Optical Deep Space Surveillance, or GEODSS, System of telescopes is the United States major tracking system for deep space. This network consists of telescopes in Maui, Hawaii; Diego Garcia (Indian Ocean), and Socorro, New Mexico. A fourth optical telescope, though smaller in size, has been operating in conjunction with this effort until recently in M.ron, Spain. With the M.ron site closing, a significant gap in longitude exists between the New Mexico and Diego Garcia sites. This longitudinal gap is well covered by placing a telescope on Ascension Island (7degrees 58'20" S, 14degrees 24'4"W), in the Atlantic Ocean. Ascension Island offers the benefits of both location and weather. The near equatorial location affords the opportunity to access under-sampled low-inclination orbits and new GEO longitudes, while simultaneously filling in the GEODSS longitudinal gap. Ascension Island is a volcanic, desert island, receiving only 7" of rain per year on average. With consistent trade winds blowing from the SSE direction off Africa, the combination of an island location with consistent winds will create the smooth laminar flow sought after by all astronomical sites, which creates stable atmospheric ('seeing') conditions. Finally, this low population island has minimal lighting, resulting in very dark skies, ideal for an observatory.

Lederer, S. M.↗
NASA NTRS1971

Analytical solution for the wind-driven circulation in a lake containing an island

An analysis was carried out to determine analytically the effect of an island on the wind driven currents in a shallow lake (or sea). A general analysis is developed that can be applied to a large class of lake and island geometries and bottom topographies. Detailed numerical results are obtained for a circular island located eccentrically or concentrically in a circular lake with a logarithmic bottom topography. It is shown that an island can produce volume flow (vertically integrated velocities) gyres that are completely different from those produced by a normal basin without an island. These gyres in the neighborhood of the island will produce different velocity patterns, which include the acceleration of flow near the island shore.

Goldstein, M. E.↗
NASA NTRS1982

The effect of islands on low frequency equatorial motions

A complete analytic solution is presented for the influence of equatorial islands on steady low-frequency waves. If the island is small (the meridional extent is much less than the equatorial radius of deformation, R), the waves pass it almost undisturbed, with the mass flux incident on the upstream side flowing around it nearly equally to the north and to the south and continuing on downstream in the lee of the island. For large islands (comparable in extent with R or larger), the principal response is organized as it would be if the island barrier were meridionally infinite. An incident Kelvin wave is largely reflected as long Rossby waves; symmetric long Rossby waves are reflected as equatorial Kelvin waves, while antisymmetric ones stop at the island barrier. In all cases, a boundary current composed of short Rossby waves forms at the eastern side of the island and accomplishes the required meridional redistribution of the zonal mass flux.

Cane, M. A.↗
NASA NTRS2002

Studies of Islands on Freely Suspended Bubbles of Smectic Liquid Crystal

We have constructed an optical system for observing the internal structure of freely suspended smectic liquid crystal bubbles using a reflected light microscope. Liquid crystal bubbles can have thicker circular regions (islands) which can easily be generated by shrinking the bubble diameter. The diameter of these islands is approximately 10 microns and they are typically up to five times thicker than the surrounding liquid crystal film (500 angstroms). In the Laboratory, the location of the islands is strongly influenced by gravity, which causes the majority of islands to migrate to the bottom half of the bubble. We will describe the size and thickness distributions of islands and their time evolution, and also discuss two-dimensional hydrodynamics and turbulence of smectic bubbles, the shapes of islands and holes affected by bubble vibrations, and the interactions between islands, which we have probed using optical tweezers.

Pattanaporkratana, A.↗
NASA NTRS2011

Digi Island: A Serious Game for Teaching and Learning Digital Circuit Optimization

Karnaugh maps, also known as K-maps, are a tool used to optimize or simplify digital logic circuits. A K-map is a graphical display of a logic circuit. K-map optimization is essentially the process of finding a minimum number of maximal aggregations of K-map cells. with values of 1 according to a set of rules. The Digi Island is a serious game designed for aiding students to learn K-map optimization. The game takes place on an exotic island (called Digi Island) in the Pacific Ocean . The player is an adventurer to the Digi Island and will transform it into a tourist attraction by developing real estates, such as amusement parks.and hotels. The Digi Island game elegantly converts boring 1s and Os in digital circuits into usable and unusable spaces on a beautiful island and transforms K-map optimization into real estate development, an activity with which many students are familiar and also interested in. This paper discusses the design, development, and some preliminary results of the Digi Island game.

Harper, Michael↗
NASA NTRS2016

MMS Observations of Ion-Scale Magnetic Island in the Magnetosheath Turbulent Plasma

In this letter, first observations of ion-scale magnetic island from the Magnetospheric Multiscale mission in the magnetosheath turbulent plasma are presented. The magnetic island is characterized by bipolar variation of magnetic fields with magnetic field compression, strong core field, density depletion, and strong currents dominated by the parallel component to the local magnetic field. The estimated size of magnetic island is about 8 di, where di is the ion inertial length. Distinct particle behaviors and wave activities inside and at the edges of the magnetic island are observed: parallel electron beam accompanied with electrostatic solitary waves and strong electromagnetic lower hybrid drift waves inside the magnetic island and bidirectional electron beams, whistler waves, weak electromagnetic lower hybrid drift waves, and strong broadband electrostatic noise at the edges of the magnetic island. Our observations demonstrate that highly dynamical, strong wave activities and electron-scale physics occur within ion-scale magnetic islands in the magnetosheath turbulent plasma..

Huang, S. Y.↗
NASA NTRS1971

Composition of island arcs and continental growth.

Island arc volcanism has contributed and is still contributing to continental growth, but the composition of island arcs differs from that of the upper continental crust in its lower abundance of Si, K, Rb, Ba, Sr and light rare earth elements. In their advanced stage of evolution, island arcs contain more than 80% of tholeiitic and 15% of ?island arc' calc-alkaline rocks with varied SiO2 contents. The larger proportion of tholeiitic rocks is in the lower crustal levels. The high stratigraphical levels of the island arcs are composed of tholeiitic plus calc-alkaline and/or high potash (shoshonitic) associations with higher abundances of K, Rb, Sr, and Ba. Stratification of the island arc crust is accentuated by another type of calc-alkaline volcanism (Andean type) originating at a late stage of arc evolution, probably by partial melting at the base of the crust. This causes enrichment of the upper crust in K, Rb, Ba and REE and accounts for upper crustal abundances of these elements as well as of SiO2.

Jakes, P.↗
NASA NTRS1990

Horizontal variability of the marine boundary layer structure upwind of San Nicolas Island during FIRE, 1987

During the months of June and July 1987, the Marine Stratocumulus Intensive Field Observation Experiment of First ISCCP Regional Experiment (FIRE) was conducted in the Southern California offshore area in the vicinity of San Nicolas Island (SNI). The Naval Ocean Systems Center (NOSC) airborne platform was utilized during FIRE to investigate the upwind low level horizontal variability of the marine boundary layer structure to determine the representativeness of SNI-based measurements to upwind open ocean conditions. The NOSC airborne meteorological platform made three flights during FIRE, two during clear sky conditions (19 and 23 July), and one during two stratus conditions (15 July). The boundary layer structure variations associated with the stratus clouds of 15 July 1987 are discussed. Profiles of air temperature (AT) and relative humidity (RH) taken 'at' and 'upwind' of SNI do show differences between the so-called open ocean conditions and those taken near the island. However, the observed difference cannot be uniquely identified to island effects, especially since the upwind fluctuations of AT and RH bound the SNI measurements. Total optical depths measures at SNI do not appear to be greatly affected by any surface based aerosol effects created by the island and could therefore realistically represent open ocean conditions. However, if one were to use the SNI aerosol measurements to predict ship to ship EO propagation conditions, significant errors could be introduced due to the increased number of surface aerosols observed near SNI which may not be, and were not, characteristic of open ocean conditions. Sea surface temperature measurements taken at the island will not, in general, represent those upwind open ocean conditions. Also, since CTT's varied appreciably along the upwind radials, measurements of CTT over the island may not be representative of actual open ocean CTT's.

Jensen, Douglas R.↗
NASA NTRS1994

A GIS approach to urban heat island research: The case of Huntsville, Alabama

The urban heat island represents a case of inadvertent human modification of climate in an urban environment. Urbanization changes the nature of the surface and atmospheric properties of a region. As a result, radiation balance in the urban areas is altered and sensible heat is added to the point that urban areas are warmer than surrounding rural areas. At the boundary between the rural and urban area, a sharp rise in temperature occurs, culminating to a peak temperature at the central business district of the city, hence the name 'urban heat island'. The extent and intensity of the urban heat island are a function of population size, land use, and topography. Because the urban heat island exhibits spatial variations of temperatures, the use of Geographic Information System (GIS) is appropriate. The research on the urban heat island focuses on the acquisition of 15 bands of visible and thermal infrared data (ranging from 0.45 to 12.2 microns) from an aerial platform using NASA's ATLAS (Airborne Thermal/Visible Land Application Sensor) over Huntsville, Alabama. The research reported in this paper is an analysis of the impact of population, land use, and topography on the shape of the urban heat island that could be developed in Huntsville using the GIS approach. The outcome of this analysis can then be verified using the acquired remotely sensed data.

Lo, Chor Pong↗
NASA NTRS1995

Analyses of TIMS and AVIRIS data, integrated with field and laboratory spectra, for lithological and mineralogical interpretation of Vulcano Island, Italy

Vulcano Island is part of the Eolian archipelago, located about 25 km from the northeast coast of Sicily. The archipelago comprises seven major volcanic islands, two of which are active volcanoes (Vulcano and Stromboli). Vulcano covers an area of about 50 square km, and is about 10 km long. Explosive volcanic activity has predominated in the geological evolution of Vulcano Island, and there is no evidence that this pattern has ceased. Rather, the current situation is one of unrest, so a strict regimen of continuous geophysical and geochemical monitoring has been undertaken over the last decade. Though the year-round population of Vulcano is small (under 1000), during the summer the island becomes a very popular resort, and has thousands of additional tourists at any time throughout the high season, thus substantially increasing the number of people potentially at risk from an explosive eruption or other hazards such as noxious gas emissions (e.g., CO2, H2S, SO2). During the past ten years, remote sensing data have been repetitively acquired with optical and microwave airborne sensors. The present work shows the preliminary results of a study based on the integration of various remote sensing data sets with field spectroscopy, and other laboratory analyses, for the geological and geomorphological mapping of the island. It is hoped that such work will also usefully contribute to the evaluation of the volcanic hazard potential of the islands as well as to the evaluation of the status of its current activity.

Buongiorno, M. Fabrizia↗
NASA NTRS1996

Thermal signatures of urban land cover types: High-resolution thermal infrared remote sensing of urban heat island in Huntsville, AL

The main objective of this research is to apply airborne high-resolution thermal infrared imagery for urban heat island studies, using Huntsville, AL, a medium-sized American city, as the study area. The occurrence of urban heat islands represents human-induced urban/rural contrast, which is caused by deforestation and the replacement of the land surface by non-evaporating and non-porous materials such as asphalt and concrete. The result is reduced evapotranspiration and more rapid runoff of rain water. The urban landscape forms a canopy acting as a transitional zone between the atmosphere and the land surface. The composition and structure of this canopy have a significant impact on the thermal behavior of the urban environment. Research on the trends of surface temperature at rapidly growing urban sites in the United States during the last 30 to 50 years suggests that significant urban heat island effects have caused the temperatures at these sites to rise by 1 to 2 C. Urban heat islands have caused changes in urban precipitation and temperature that are at least similar to, if not greater than, those predicted to develop over the next 100 years by global change models. Satellite remote sensing, particularly NOAA AVHRR thermal data, has been used in the study of urban heat islands. Because of the low spatial resolution (1.1 km at nadir) of the AVHRR data, these studies can only examine and map the phenomenon at the macro-level. The present research provides the rare opportunity to utilize 5-meter thermal infrared data acquired from an airplane to characterize more accurately the thermal responses of different land cover types in the urban landscape as input to urban heat island studies.

Lo, Chor Pang↗
NASA NTRS1997

Breccia Formation at a Complex Impact Crater: Slate Islands, Lake Superior, Ontario, Canada

The Slate Islands impact structure is the eroded remnant of a approximately 30-32 km-diameter complex impact structure located in northern Lake Superior, Ontario, Canada. Target rocks are Archean supracrustal and igneous rocks and Proterozoic metavolcanics, metasediments, and diabase. A wide variety of breccias occurs on the islands, many of which contain fragments exhibiting shock metamorphic features. Aphanitic, narrow and inclusion-poor pseudotachylite veins, commonly with more or less parallel boundaries and apophyses branching off them, represent the earliest breccias formed during the compression stage of the impact process. Coarse-grained, polymictic elastic matrix breccias form small to very large, inclusion-rich dikes and irregularly shaped bodies that may contain altered glass fragments. These breccias have sharp contacts with their host rocks and include a wide range of fragment types some of which were transported over minimum distances of approximately 2 km away from the center of the structure. They cut across pseudotachylite veins and contain inclusions of them. Field and petrographic evidence indicate that these polymictic breccias formed predominantly during the excavation and central uplift stages of the impact process. Monomictic breccias, characterized by angular fragments and transitional contacts with their host rocks, occur in parautochthonous target rocks, mainly on the outlying islands of the Slate Islands archipelago. A few contain fragmented and disrupted, coarse-grained, polymictic clastic matrix breccia dikes. This is an indication that at least some of these monomictic breccias formed late in the impact process and that they are probably related to a late crater modification stage. A small number of relatively large occurrences of glass-poor, suevitic breccias occur at the flanks of the central uplift and along the inner flank of the outer ring of the Slate Islands complex crater. A coarse, glass-free, allogenic breccia, containing shatter-coned fragments derived from Proterozoic target rocks (upper target strata), observed at two locations may be analogous to the 'Bunt Breccia' of the Ries crater in Germany. At one of these locations this breccia lies close to a crater suevite deposit. At the other, it overlies parautochthonous, monomictic breccia. The State Islands impact breccias are superbly exposed, much better than breccias in most other terrestrial impact structures. Observations, including those indicative of multiple and and sequential processes, provide insight on how impact breccias form and how they relate to the various phases of the impact process. Eventually they will lead to an improved understanding of planetary impact processes.

Dressler, B. O.↗
NASA NTRS1984

The erosion of streamlined islands, longitudinal grooves and scour marks: Implications to the origin of the Martian outflow channels

The diversity of proposed origins for large Martian outflow channels results from the differing interpretations given to the landforms associated with the outflow channels. In an attempt to help limit the possible mechanisms of channel erosion, detailed studies of three of the channel features were done; the streamlined islands, longitudinal grooves and scour marks. This examination involved a comparison of the martian streamlined islands with various streamlined landforms on Earth including those found in the Channel Scabland in large rivers, glacial drumlins, and desert yardangs. The comparisons included statistical analyses of the landform lengths versus widths and positions of maximum width, and an examination of the degree of shape agreement with the geometric lemniscate which was in turn demonstrated to correspond closely with true airfoil shapes. The analyses showed that the shapes of the martian islands correspond closely to the streamlined islands in rivers and the Channel Scabland land. Drumlins show a much smaller correlation. Erosional rock islands formed by glaciers are very much different in shape.

Komar, P. D.↗
NASA NTRS1985

On the effects of islands' geometry and size on inducing sea breeze circulation

Model scaling of the characteristics of the sea breeze circulation involved with circular and slab elongated-symmetric midlatitude islands was performed. Larger horizontal and vertical velocities were indicated over the small circular islands as compared to those over corresponding elongated islands. The circulation characteristics of both types of islands become similar when the half-width of the island is about the same as the distance of inland penetration of the sea breeze in a nonisland case. Evaluation of the results through a scale analysis is presented.

Mahrer, Y.↗
NASA NTRS1995

New Observations at the Slate Islands Impact Structure, Lake Superior

Slate Islands, a group of 2 large and several small islands, is located in northern Lake Superior, approximately 10 km south of Terrace Bay. Shatter cones, breccias and shock metamorphic features provide evidence that the Slate Islands Structure was formed as a result of asteroid or comet impact. Most of the island group is believed to represent the central uplift of a complex impact crater. The structure possibly has a diameter of about 32 km. For Sage (1978, 1991) shock metamorphic features, shatter cones and pervasive rock brecciation are the results of diatreme activity. The present investigations represent the second year of a co-operative study of the Lunar and Planetary Institute, Houston, Texas and the Field Services Section (Northwest) of the Ontario Geological Survey. The objective of this investigation is to come to a better understanding of the formation of mid-size impact structures on Earth and the planets of the solar system. Impact processes played a fundamental role in the formation of the planets and the evolution of life on Earth. Meteorite and comet impacts are not a phenomenon of the past. Last year, more than 20 pieces of the Shoemaker-Levy 9 impacted on Jupiter and the Tunguska comet impacted in Siberia in the early years of this century. The study of impact processes is a relatively young part of geoscience and much is still to be learnt by detailed field and laboratory investigations. The State Islands Structure has been selected for the present detailed investigations because of the excellent shoreline outcrops of rock units related to the impact. The structure is a complex impact crater that has been eroded so that important lithological and structural elements are exposed. We know of no other mid-size terrestrial impact structure with equal or better exposures. In this publication we present preliminary results of our 1994 and 1995 field and laboratory investigations. We have tentatively identified a few impact melt and a considerable number of suevite occurrences.

Dressler, B. O.↗
NASA NTRS1999

Slate Islands, Lake Superior, Canada: A mid-size, Complex Impact Structure

The target rocks of the 30-32-km diameter Slate Islands impact structure in northern Lake Superior, Canada, are Archean supracrustal and igneous rocks and supracrustal Proterozoic rocks. Shatter cones, pseudotachylites, impact glasses, and microscopic shock metamorphic features were formed during the contact and compression phase of the impact process, followed, during excavation and central uplift, by polymict, clastic matrix breccias in the uplifted target, and by allogenic fall-back breccias (suevite and bunte breccia). Monomict, autoclastic breccias were mainly observed on Mortimer Island and the other outlying islands of the archipelago and were probably generated relatively late in the impact process (central uplift and/or crater modification). The frequency of low index planar shock metamorphic features in quartz was correlated with results from shock experiments to estimate shock pressures experienced by the target rocks. The resulting shock attenuation plan across the archipelago is irregular, probably because the shock wave did not expand from a point or spherical source, and because of the destruction of an originally more regular shock attenuation plan during the central uplift and crater modification stages of the impact process. No impact melt rock bodies have been positively identified on the islands. An impact melt may be present in the annular trough around the islands, though and-based on a weighted mixture of target rocks-may have an intermediate-mafic composition. No such impact melt was found on the archipelago. An Ar-40-Ar-39 release spectrum of a pseudotachylite provides an age of about 436 Ma for the impact structure, substantiating age constraints based on various stratigraphic considerations.

Dressler, B. O.↗
NASA NTRS2001

The Urban Heat Island Pilot Project (UHIPP)

Urban heat islands increase the demand for cooling energy and accelerate the formation of smog. They are created when natural vegetation is replaced by heat-absorbing surfaces such as building roofs and walls, parking lots, and streets. Through the implementation of measures designed to mitigate the urban heat island, communities can decrease their demand for energy and effectively "cool" the metropolitan landscape. Measures to reverse the urban heat island include afforestation and the widespread use of highly reflective surfaces. To demonstrate the potential benefits of implementing these measures, EPA has teamed up with NASA and LBNL to initiate a pilot project with three U.S. cities. As part of the pilot, NASA is using remotely-sensed data to quantify surface temperature, albedo, the thermal response number and NDVI vegetation of each city. To pursue these efforts, more information is needed about specific characteristics of several different cities. NASA used the Advanced Thermal and Land Applications Sensor (ATLAS) to obtain high spatial resolution (10 m pixel resolution) over each of the three pilot cities (Baton Rouge, Sacramento, and Salt Lake City). The goal of the UHIPP is to use the results from the NASA/LBNL analysis, combined with knowledge gained through working with various organizations within each pilot city to identify the most effective means of implementing strategies designed to mitigate the urban heat island, These "lessons learned" will be made available and used by cities across the U.S. to assist policy makers and others within various communities to analyze their own urban heat islands and determine which, if any, measures can be taken to help save energy and money, and to prevent pollution. The object of this session is for representatives from each of the pilot cities to present their results of the study and share the experience of working with these data in managing their urban landscape.

Luvall, Jeff↗