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NASA NTRS2007

Diverse Metals and Sulfides in Polymict Ureilites EET 83309 and EET 87720

Ureilites are a group of carbon-bearing ultramafic achondrites. The majority of samples are monomict with major and trace element compositions consistent with a restitic origin after extensive loss of basaltic melts and significant loss of their metallic component during anatexis. Monomict ureilites are thought to represent largely intact samples of the ureilite parent body (UPB) mantle. Polymict ureilites, by contrast, are fragmental breccias consisting of welded lithic clasts and isolated mineral fragments thought to be regolith that assembled after major disruption fragmented large portions of the UPB mantle. In most polymict ureilites, the majority of clasts consist of material similar to monomict ureilites gardened from the UPB mantle but other materials, both endogenic and xenogenic to the UPB are also found in polymict ureilites, including clasts texturally and compositionally similar to known chondrite types as well as feldspathic melt rocks and clasts of Ca-Al-Ti-rich assemblages. In this study, we demonstrate that polymict ureilites also contain a variety of metal and sulfide compositions of diverse origins. They offer insight into the final equilibrium conditions of disrupted portions of the UPB mantle and the diversity of materials locally available for regolith formation, and provide evidence for only limited post-regolith formation thermal metamorphism.

Herrin, J. S.↗
NASA NTRS2006

Feeling Well Rested and Wide Awake When it Counts

Responding to a congressional concern about aviation safety, NASA's Ames Research Center created the Ames Fatigue/Jet Lag Program in 1980 to examine the extent to which fatigue, sleep loss, and circadian disruption affect pilot performance. The program s primary research was conducted in field settings, as well as in a variety of aviation, controlled laboratory, and full-mission flight-simulation environments, to study fatigue factors and circadian disruption in short-haul, long-haul, military, cargo, and helicopter operations. In 1990, NASA changed the program s name to the Fatigue Countermeasures Group, to provide a greater emphasis on the development and evaluation of countermeasures that would mitigate the adverse effects of fatigue and maximize flight crew performance and alertness. The research conducted by this group at Ames included field studies of cockpit rest, quantity and quality of onboard sleep, and performance changes associated with long-haul flights.

Source record↗
NASA NTRS2005

The Remarkable 2003--2004 Winter and Other Recent Warm Winters in the Arctic Stratosphere Since the Late 1990s

The 2003-2004 Arctic winter was remarkable in the approximately 50-year record of meteorological analyses. A major warming beginning in early January 2004 led to nearly 2 months of vortex disruption with high-latitude easterlies in the middle to lower stratosphere. The upper stratospheric vortex broke up in late December, but began to recover by early January, and in February and March was the strongest since regular observations began in 1979. The lower stratospheric vortex broke up in late January. Comparison with 2 previous years, 1984-1985 and 1986-1987, with prolonged midwinter warming periods shows unique characteristics of the 2003-2004 warming period: The length of the vortex disruption, the strong and rapid recovery in the upper stratosphere, and the slow progression of the warming from upper to lower stratosphere. January 2004 zonal mean winds in the middle and lower stratosphere were over 2 standard deviations below average. Examination of past variability shows that the recent frequency of major stratospheric warmings (7 in the past 6 years) is unprecedented. Lower stratospheric temperatures were unusually high during 6 of the past 7 years, with 5 having much lower than usual potential for polar stratospheric cloud (PSC) formation and ozone loss (nearly none in 1998-1999, 2001-2002, and 2003-2004, and very little in 1997-1998 and 2000-2001). Middle and upper stratospheric temperatures, however, were unusually low during and after February. The pattern of 5 of the last 7 years with very low PSC potential would be expected to occur randomly once every 850 years. This cluster of warm winters, immediately following a period of unusually cold winters, may have important implications for possible changes in interannual variability and for determination and attribution of trends in stratospheric temperatures and ozone.

ozone↗
NASA NTRS2008

Warming of the Indian Ocean Threatens Eastern and Southern Africa, but could be Mitigated by Agricultural Development

Since 1980, the number of undernourished people in eastern and southern Africa has more than doubled. Rural development stalled and rural poverty expanded during the 1990s. Population growth remains very high and declining per capita agricultural capacity retards progress towards Millennium Development goals. Analyses of in situ station data and satellite observations of precipitation identify another problematic trend. Main growing season rainfall receipts have diminished by approximately 15% in food insecure countries clustered along the western rim of the Indian Ocean. Occurring during the main growing seasons in poor countries dependent on rain fed agriculture, these declines are societally dangerous. Will they persist or intensify? Tracing moisture deficits upstream to an anthropogenically warming Indian Ocean leads us to conclude that further rainfall declines are likely. We present analyses suggesting that warming in the central Indian Ocean disrupts onshore moisture transports, reducing continental rainfall. Thus late 20th century anthropogenic Indian Ocean warming has probably already produced societally dangerous climate change by creating drought and social disruption in some of the world's most fragile food economies. We quantify the potential impacts of the observed precipitation and agricultural capacity trends by modeling millions of undernourished people as a function of rainfall, population, cultivated area, seed and fertilizer use. Persistence of current tendencies may result in a 50% increase in undernourished people. On the other hand, modest increases in per capita agricultural productivity could more than offset the observed precipitation declines. Investing in agricultural development can help mitigate climate change while decreasing rural poverty and vulnerability.

Funk, Chris↗
NASA NTRS2008

CME Initiation

One of the most challenging problems in solar physics is understanding the processes responsible for giant magnetic disruptions such as the event of July 14, 2000, which consisted of a massive filament ejection, a fast coronal mass ejection (CME), prolonged X-class flaring, and an intense particle storm. These major events are of critical importance because they drive the most destructive forms of space weather and they provide a unique opportunity to study, in revealing detail, MHD instability and nonequilibrium -- processes that are at the heart of plasma astrophysics. It is now widely accepted that CMEs/eruptive flares represent the explosive release of magnetic energy stored in the corona. Therefore, in order to understand the phenomenon, we must answer the following questions: What is the field structure responsible for the disruption and why is the energy released explosively? In this talk we address these two questions using the latest theories and numerical models for CMEs/eruptive flares.

Antiochos, Spiro K.↗
NASA NTRS2007

Understanding and Counteracting Fatigue in Flight Crews

The materials included in the collection of documents describe the research of the NASA Ames Fatigue Countermeasures Group (FCG), which examines the extent to which fatigue, sleep loss, and circadian disruption affect flight-crew performance. The group was formed in 1980 in response to a Congressional request to examine a possible safety problem of uncertain magnitude due to transmeridian flying and a potential problem due to fatigue in association with various factors found in air-transport operations and was originally called the Fatigue/Jet Lag Program. The goals of the FCG are: (1) the development and evaluation of strategies for mitigating the effects of sleepiness and circadian disruption on pilot performance levels; (2) the identification and evaluation of objective approaches for the prediction of alertness changes in flight crews; and (3) the transfer and application of research results to the operational field via classes, workshops, and safety briefings. Some of the countermeasure approaches that have been identified to be scientifically valid and operationally relevant are brief naps (less than 40 min) in the cockpit seat and 7-min activity breaks, which include postural changes and ambulation. Although a video-based alertness monitor based on slow eyelid closure shows promise in other operational environments, research by the FCG has demonstrated that in its current form at the time of this reporting, it is not feasible to implement it in the cockpit. Efforts also focus on documenting the impact of untreated fatigue on various types of flight operations. For example, the FCG recently completed a major investigation into the effects of ultra-long-range flights (20 continuous hours in duration) on the alertness and performance of pilots in order to establish a baseline set of parameters against which the effectiveness of new ultra-long-range fatigue remedies can be judged.

Mallis, Melissa↗
NASA NTRS2010

Optical Structural Health Monitoring Device

This non-destructive, optical fatigue detection and monitoring system relies on a small and unobtrusive light-scattering sensor that is installed on a component at the beginning of its life in order to periodically scan the component in situ. The method involves using a laser beam to scan the surface of the monitored component. The device scans a laser spot over a metal surface to which it is attached. As the laser beam scans the surface, disruptions in the surface cause increases in scattered light intensity. As the disruptions in the surface grow, they will cause the light to scatter more. Over time, the scattering intensities over the scanned line can be compared to detect changes in the metal surface to find cracks, crack precursors, or corrosion. This periodic monitoring of the surface can be used to indicate the degree of fatigue damage on a component and allow one to predict the remaining life and/or incipient mechanical failure of the monitored component. This wireless, compact device can operate for long periods under its own battery power and could one day use harvested power. The prototype device uses the popular open-source TinyOS operating system on an off-the-shelf Mica2 sensor mote, which allows wireless command and control through dynamically reconfigurable multi-node sensor networks. The small size and long life of this device could make it possible for the nodes to be installed and left in place over the course of years, and with wireless communication, data can be extracted from the nodes by operators without physical access to the devices. While a prototype has been demonstrated at the time of this reporting, further work is required in the system s development to take this technology into the field, especially to improve its power management and ruggedness. It should be possible to reduce the size and sensitivity as well. Establishment of better prognostic methods based on these data is also needed. The increase of surface roughness with fatigue is closely connected to the microstructure of the metal, and ongoing research is seeking to connect this observed evidence of the fatigue state with microstructural theories of fatigue evolution to allow more accurate prognosis of remaining component life. Plans are also being discussed for flight testing, perhaps on NASA s SOFIA platform.

Buckner, Benjamin D.↗
NASA NTRS2009

Icy Satellites of Saturn: Impact Cratering and Age Determination

Saturn is the first giant planet to be visited by an orbiting spacecraft that can transmit large amounts of data to Earth. Crater counts on satellites from Phoebe inward to the regular satellites and ring moons are providing unprecedented insights into the origin and time histories of the impacting populations. Many Voyager-era scientists concluded that the satellites had been struck by at least two populations of impactors. In this view, the Population I impactors, which were generally judged to be comets orbiting the Sun, formed most of the larger and older craters, while Population II impactors, interpreted as Saturn-orbiting ejecta from impacts on satellites, produced most of the smaller and younger craters. Voyager data also implied that all of the ring moons, and probably some of the midsized classical moons, had been catastrophically disrupted and reaccreted since they formed. We examine models of the primary impactor populations in the Saturn system. At the present time, ecliptic comets, which likely originate in the Kuiper belt/scattered disk, are predicted to dominate impacts on the regular satellites and ring moons, but the models require extrapolations in size (from the observed Kuiper belt objects to the much smaller bodies that produce the craters) or in distance (from the known active Jupiter family comets to 9.5 AU). Phoebe, Iapetus, and perhaps even moons closer to Saturn have been struck by irregular satellites as well. We describe the Nice model, which provides a plausible mechanism by which the entire Solar System might have experienced an era of heavy bombardment long after the planets formed. We then discuss the three cratering chronologies, including one based upon the Nice model, that have been used to infer surface ages from crater densities on the saturnian satellites. After reviewing scaling relations between the properties of impactors and the craters they produce, we provide model estimates of the present-day rate at which comets impact, and catastrophically disrupt, the saturnian moons. Finally, we present crater counts on the satellites from two different groups. Many of the heavily cratered terrains appear to be nearly saturated, so it is difficult to infer the provenance of the impactors from crater counts alone. More large craters have been found on Iapetus than on any other satellite. Enceladus displays an enormous range of surface ages, ranging from the old mid-latitude plains to the extremely young South Polar Terrain. Cassini images provide some evidence for the reality of Population II. Most of the observed craters may have formed in one or more cataclysms, but more work is needed to determine the roles of heliocentric and planetocentric bodies in creating the craters.

Dones, L.↗
NASA NTRS2001

The Effect of Acute Microgravity on Mechanically-Induced Membrane Damage and Membrane-Membrane Fusion Events

Although it is unclear how a living cell senses gravitational forces there is no doubt that perturbation of the gravitational environment results in profound alterations in cellular function. In the present study, we have focused our attention on how acute microgravity exposure during parabolic flight affects the skeletal muscle cell plasma membrane (i.e. sarcolemma), with specific reference to a mechanically-reactive signaling mechanism known as mechanically-induced membrane disruption or "wounding". This response is characterized by both membrane rupture and membrane resealing events mediated by membrane-membrane fusion. We here present experimental evidence that acute microgravity exposure can inhibit membrane-membrane fusion events essential for the resealing of sarcolemmal wounds in individual human myoblasts. Additional evidence to support this contention comes from experimental studies that demonstrate acute microgravity exposure also inhibits secretagogue-stimulated intracellular vesicle fusion with the plasma membrane in HL-60 cells. Based on our own observations and those of other investigators in a variety of ground-based models of membrane wounding and membrane-membrane fusion, we suggest that the disruption in the membrane resealing process observed during acute microgravity is consistent with a microgravity-induced decrease in membrane order.

Clarke, Mark, S. F.↗
NASA NTRS2001

Stabilized NADH as a Countermeasure for Jet Lag

Current remedies for jet lag (phototherapy, melatonin, stimulant, and sedative medications) are limited in efficacy and practicality. The efficacy of a stabilized, sublingual form of reduced nicotin amide adenine dinucleotide (NADH, ENADAlert, Menuco Corp.) as a countermeasure for jet lag was examined. Because NADH increases cellular production of ATP and facilitates dopamine synthesis, it may counteract the effects of jet lag on cognitive functioning and sleepiness. Thirty-five healthy, employed subjects participated in this double-blind, placebo-controlled study. Training and baseline testing were conducted on the West Coast before subjects flew overnight to the East Coast, where they would experience a 3-hour time difference. Upon arrival, individuals were randomly assigned to receive either 20 mg of sublingual stabilized ADH (n=18) or identical placebo tablets (n=17). All participants completed computer-administered tests (including CogScreen7) to assess changes in cognitive functioning, mood, and sleepiness in the morning and afternoon. Jet lag resulted in increased sleepiness for over half the participants and deterioration of cognitive functioning for approximately one third. The morning following the flight, subjects experienced lapses of attention in addition to disruptions in working memory, divided attention, and visual perceptual speed. Individuals who received NADH performed significantly better on 5 of 8 cognitive and psychomotor test measures (P less than or equal to 0.5) and showed a trend for better performance on the other three measures (P less than or equal to .l0). Subjects also reported less sleepiness compared with those who received placebo. No adverse effects were observed with NADH treatment. Stabilized NADH significantly reduced jet lag-induced disruptions of cognitive functioning, was easily administered, and was found to have no adverse side effects.

Kay, Gary G.↗
NASA NTRS2011

Lunar Ion Transport Near Magnetic Anomalies: Possible Implications for Swirl Formation

The bright swirling features on the lunar surface in areas around the Moon but most prominently at Reiner Gamma, have intrigued scientists for many years. After Apollo and later Lunar Prospector (LP} mapped the Lunar magnetic fields from orbit, it was observed that these features are generally associated with crustal magnetic anomalies. This led researchers to propose a number of explanations for the swirls that invoke these fields. Prominent among these include magnetic shielding in the form of a mini-magnetosphere which impedes space weathering by the solar wind, magnetically controlled dust transport, and cometary or asteroidal impacts that would result in shock magnetization with concomitant formation ofthe swirls. In this presentation, we will consider another possibility, that the ambient magnetic and electric fields can transport and channel secondary ions produced by micrometeorite or solar wind ion impacts. In this scenario, ions that are created in these impacts are under the influence of these fields and can drift for significant distances before encountering the magnetic anomalies when their trajectories are disrupted and concentrated onto nearby areas. These ions may then be responsible for chemical alteration of the surface leading either to a brightening effect or a disruption of space weathering processes. To test this hypothesis we have run ion trajectory simulations that show ions from regions about the magnetic anomalies can be channeled into very small areas near the anomalies and although questions remain as to nature of the mechanisms that could lead to brightening of the surface it appears that the channeling effect is consistent with the existence of the swirls.

Keller, J. W.↗
NASA NTRS2009

Developing NDE Techniques for Large Cryogenic Tanks

The Shuttle and Constellation Programs require very large cryogenic ground storage tanks in which to store liquid oxygen and hydrogen. The existing LC-39 pad tanks, which will be passed onto Constellation, are 40 years old and have received minimal refurbishment or even inspection, because they can only be temperature cycled a few times before being overhauled (a costly operation in both time and dollars). Numerous questions exist on the performance and reliability of these old tanks which could cause a major Program schedule disruption. Consequently, with the passing of the first two tanks to Constellation to occur this year, there is growing awareness that NDE is needed to detect problems early in these tanks so that corrective actions can be scheduled when least disruptive. Time series thermal images of two sides of the Pad B LH2 tank have been taken over multiple days to demonstrate the effects of environmental conditions to the solar heating of the tank and therefore the effectiveness of thermal imaging.

Parker, Don↗
NASA NTRS2009

Enhancing Team Performance for Long-Duration Space Missions

Success of exploration missions will depend on skilled performance by a distributed team that includes both the astronauts in space and Mission Control personnel. Coordinated and collaborative teamwork will be required to cope with challenging complex problems in a hostile environment. While thorough preflight training and procedures will equip creW'S to address technical problems that can be anticipated, preparing them to solve novel problems is much more challenging. This presentation will review components of effective team performance, challenges to effective teamwork, and strategies for ensuring effective team performance. Teamwork skills essential for successful team performance include the behaviors involved in developing shared mental models, team situation awareness, collaborative decision making, adaptive coordination behaviors, effective team communication, and team cohesion. Challenges to teamwork include both chronic and acute stressors. Chronic stressors are associated with the isolated and confined environment and include monotony, noise, temperatures, weightlessness, poor sleep and circadian disruptions. Acute stressors include high workload, time pressure, imminent danger, and specific task-related stressors. Of particular concern are social and organizational stressors that can disrupt individual resilience and effective mission performance. Effective team performance can be developed by training teamwork skills, techniques for coping with team conflict, intracrew and intercrew communication, and working in a multicultural team; leadership and teamwork skills can be fostered through outdoor survival training exercises. The presentation will conclude with an evaluation of the special requirements associated with preparing crews to function autonomously in long-duration missions.

Orasanu, Judith M.↗
NASA NTRS2011

Consequence and Resilience Modeling for Chemical Supply Chains

The U.S. chemical sector produces more than 70,000 chemicals that are essential material inputs to critical infrastructure systems, such as the energy, public health, and food and agriculture sectors. Disruptions to the chemical sector can potentially cascade to other dependent sectors, resulting in serious national consequences. To address this concern, the U.S. Department of Homeland Security (DHS) tasked Sandia National Laboratories to develop a predictive consequence modeling and simulation capability for global chemical supply chains. This paper describes that capability , which includes a dynamic supply chain simulation platform called N_ABLE(tm). The paper also presents results from a case study that simulates the consequences of a Gulf Coast hurricane on selected segments of the U.S. chemical sector. The case study identified consequences that include impacted chemical facilities, cascading impacts to other parts of the chemical sector. and estimates of the lengths of chemical shortages and recovery . Overall. these simulation results can DHS prepare for and respond to actual disruptions.

Stamber, Kevin L.↗
NASA NTRS2011

Microgravity-Enhanced Stem Cell Selection

Stem cells, both embryonic and adult, promise to revolutionize the practice of medicine in the future. In order to realize this potential, a number of hurdles must be overcome. Most importantly, the signaling mechanisms necessary to control the differentiation of stem cells into tissues of interest remain to be elucidated, and much of the present research on stem cells is focused on this goal. Nevertheless, it will also be essential to achieve large-scale expansion and, in many cases, assemble cells in 3D as transplantable tissues. To this end, microgravity analog bioreactors can play a significant role. Microgravity bioreactors were originally conceived as a tool to study the cellular responses to microgravity. However, the technology can address some of the shortcomings of conventional cell culture systems; namely, the deficiency of mass transport in static culture and high mechanical shear forces in stirred systems. Unexpectedly, the conditions created in the vessel were ideal for 3D cell culture. Recently, investigators have demonstrated the capability of the microgravity bioreactors to expand hematopoietic stem cells compared to static culture, and facilitate the differentiation of umbilical cord stem cells into 3D liver aggregates. Stem cells are capable of differentiating into functional cells. However, there are no reliable methods to induce the stem cells to form specific cells or to gain enough cells for transplantation, which limits their application in clinical therapy. The aim of this study is to select the best experimental setup to reach high proliferation levels by culturing these cells in a microgravity-based bioreactor. In typical cell culture, the cells sediment to the bottom surface of their container and propagate as a one-cell-layer sheet. Prevention of such sedimentation affords the freedom for self-assembly and the propagation of 3D tissue arrays. Suspension of cells is easily achievable using stirred technologies. Unfortunately, in conventional bioreactors, stirring invokes deleterious forces that disrupt cell aggregation and results in cell death. First-generation rotating bioreactors provided rotation on the horizontal axis, which resulted in the suspension of cells without stirring, thus providing a suitable environment to propagate cells without sedimentation to a surface. The rotating wall bioreactors did not provide a way to remove air bubbles that were causing shear and disrupting 3D cultures. Johnson Space Center successfully engineered the hydrofocusing bioreactor (HFB) that resolved the problem of removing the air bubbles from the fluid medium of NASA's rotating-wall space bioreactors. The HFB uses the principle of hydrodynamic focusing that simultaneously produces a low-shear fluid culture environment and a variable hydrofocusing force that can control the movement, location, and removal of suspended cells, tissues, and air bubbles from the bioreactor. The HFB is a rotating, domeshaped cell culture vessel with a centrally located sampling port and an internal viscous spinner. The vessel and spinner can rotate at different speeds either in the same or opposite directions. Rotation of the vessel and viscous interaction at the spinner generate a hydrofocusing force. Adjusting the differential rotation rate between vessel and spinner controls the magnitude of the force.

Claudio, Pier Paolo↗
NASA NTRS2009

Convective Weather Avoidance with Uncertain Weather Forecasts

Convective weather events have a disruptive impact on air traffic both in terminal area and in en-route airspaces. In order to make sure that the national air transportation system is safe and efficient, it is essential to respond to convective weather events effectively. Traffic flow control initiatives in response to convective weather include ground delay, airborne delay, miles-in-trail restrictions as well as tactical and strategic rerouting. The rerouting initiatives can potentially increase traffic density and complexity in regions neighboring the convective weather activity. There is a need to perform rerouting in an intelligent and efficient way such that the disruptive effects of rerouting are minimized. An important area of research is to study the interaction of in-flight rerouting with traffic congestion or complexity and developing methods that quantitatively measure this interaction. Furthermore, it is necessary to find rerouting solutions that account for uncertainties in weather forecasts. These are important steps toward managing complexity during rerouting operations, and the paper is motivated by these research questions. An automated system is developed for rerouting air traffic in order to avoid convective weather regions during the 20- minute - 2-hour time horizon. Such a system is envisioned to work in concert with separation assurance (0 - 20-minute time horizon), and longer term air traffic management (2-hours and beyond) to provide a more comprehensive solution to complexity and safety management. In this study, weather is dynamic and uncertain; it is represented as regions of airspace that pilots are likely to avoid. Algorithms are implemented in an air traffic simulation environment to support the research study. The algorithms used are deterministic but periodically revise reroutes to account for weather forecast updates. In contrast to previous studies, in this study convective weather is represented as regions of airspace that pilots are likely to avoid. The automated system periodically updates forecasts and reassesses rerouting decisions in order to account for changing weather predictions. The main objectives are to reroute flights to avoid convective weather regions and determine the resulting complexity due to rerouting. The eventual goal is to control and reduce complexity while rerouting flights during the 20 minute - 2 hour planning period. A three-hour simulation is conducted using 4800 flights in the national airspace. The study compares several metrics against a baseline scenario using the same traffic and weather but with rerouting disabled. The results show that rerouting can have a negative impact on congestion in some sectors, as expected. The rerouting system provides accurate measurements of the resulting complexity in the congested sectors. Furthermore, although rerouting is performed only in the 20-minute - 2-hour range, it results in a 30% reduction in encounters with nowcast weather polygons (100% being the ideal for perfectly predictable and accurate weather). In the simulations, rerouting was performed for the 20-minute - 2-hour flight time horizon, and for the en-route segment of air traffic. The implementation uses CWAM, a set of polygons that represent probabilities of pilot deviation around weather. The algorithms were implemented in a software-based air traffic simulation system. Initial results of the system's performance and effectiveness were encouraging. Simulation results showed that when flights were rerouted in the 20-minute - 2-hour flight time horizon of air traffic, there were fewer weather encounters in the first 20 minutes than for flights that were not rerouted. Some preliminary results were also obtained that showed that rerouting will also increase complexity. More simulations will be conducted in order to report conclusive results on the effects of rerouting on complexity. Thus, the use of the 20-minute - 2-hour flight time horizon weather avoidance teniques performed in the simulation is expected to provide benefits for short-term weather avoidance.

Karahan, Sinan↗
NASA NTRS2010

THEMIS and Substorm Timing

The THEMIS mission represents the culmination of many years of planning directed towards understanding the processes that drive and trigger geomagnetic substorms. Following Akasofu's discovery of the substorm cycle, it became increasingly clear that timing questions provide the key to discriminating between proposed 'inside-out' and 'outside-in' models for substorms, triggered respectively by current disruption and magnetic reconnection. THEMIS observations provide a wealth of information that is currently being investigated to resolve this question. While observations in the magnetotail generally point towards reconnection. those on the ground point towards current disruption. This talk reviews the relevant observations and recent efforts at reconciliation.

Sibeck, D. G.↗
NASA NTRS2010

Sources and Losses of Ring Current Ions

During geomagnetic quiet times, in-situ measurements of ring current energetic ions (few to few tens of keVs) from THEMIS spacecraft often exhibit multiple ion populations at discrete energies that extend from the inner magnetosphere to the magnetopause at dayside or plasma sheet at nightside. During geomagnetic storm times, the levels of fluxes as well as the mean energies of these ions elevated dramatically and the more smooth distributions in energies and distances during quiet times are disrupted into clusters of ion populations with more confined spatial extends. This reveals local plasma heating processes that might have come into play. Several processes have been proposed. Magnetotail dipolarization, sudden enhancement of field-aligned current, local current disruptions, and plasma waves are possible mechanisms to heat the ions locally as well as strong convections of energetic ions directly from the magnetotail due to reconnections. We will examine two geomagnetic storms on October 11, 2008 and July 22, 2009 to reveal possible heating mechanisms. We will analyze in-situ plasma and magnetic field measurements from THEMIS, GOES, and DMSP for the events to study the ion pitch angle distributions and magnetic field perturbations in the auroral ionosphere and inner magnetosphere where the plasma heating processes occur.

Chen, Sheng-Hsien↗