Outer Plasmaspheric Plasma Properties: What We Know from Satellite Data

Our understanding of the composition, density, and temperature structure of the outer plasmasphere has undergone several major revisions since the discovery of the plasmasphere over 35 years ago. Each new era of understanding was brought about by the launching of satellites carrying suites of plasma diagnostic experiments each more sophisticated than its predecessor. Instead of each new generation of missions providing incremental advancement in our knowledge of the plasmasphere's plasma properties, they most often than not, initiated a complete re-thinking of our understanding. There are still a number of observational "puzzles" and large gaps in our knowledge of how plasmaspheric structure and plasma properties change with geomagnetic storm and substorm activity. As we develop new missions to attempt to globally image the outer plasmasphere in order to put simultaneous multi-spacecraft observations into context, we undoubtedly will uncover new tantalizing observations that will cause us to re-think our mental picture of the plasmasphere. What we have learned from satellite data about the chemical composition, density, temperature and pitch-angle distribution properties and their variability is outlined in this review paper.     

Solar Ultraviolet Bursts

The term “ultraviolet (UV) burst” is introduced to describe small, intense, transient brightenings in ultraviolet images of solar active regions. We inventorize their properties and provide a definition based on image sequences in transition-region lines. Coronal signatures are rare, and most bursts are associated with small-scale, canceling opposite-polarity fields in the photosphere that occur in emerging flux regions, moving magnetic features in sunspot moats, and sunspot light bridges. We also compare UV bursts with similar transition-region phenomena found previously in solar ultraviolet spectrometry and with similar phenomena at optical wavelengths, in particular Ellerman bombs. Akin to the latter, UV bursts are probably small-scale magnetic reconnection events occurring in the low atmosphere, at photospheric and/or chromospheric heights. Their intense emission in lines with optically thin formation gives unique diagnostic opportunities for studying the physics of magnetic reconnection in the low solar atmosphere. This paper is a review report from an International Space Science Institute team that met in 2016–2017.     

The Lunar Orbiter Laser Altimeter Investigation on the Lunar Reconnaissance Orbiter Mission

The Lunar Orbiter Laser Altimeter (LOLA) is an instrument on the payload of NASA’s Lunar Reconnaissance Orbiter spacecraft (LRO) (Chin et al., in Space Sci. Rev. 129:391–419, 2007). The instrument is designed to measure the shape of the Moon by measuring precisely the range from the spacecraft to the lunar surface, and incorporating precision orbit determination of LRO, referencing surface ranges to the Moon’s center of mass. LOLA has 5 beams and operates at 28 Hz, with a nominal accuracy of 10 cm. Its primary objective is to produce a global geodetic grid for the Moon to which all other observations can be precisely referenced.     

Did earthquakes keep the early crust habitable?

The shallow habitable region of cratonal crust deforms with a strain rate on the order of approximately 10(19) s(1). This is rapid enough that small seismic events are expected on one-kilometer spatial scales and one-million-year timescales. Rock faulting has the potential to release batches of biological substrate, such as dissolved H(2), permitting transient blooms. In addition, the steady-state deformation of the brittle crust causes numerous small faults to be permeable enough (on the order of approximately 10(15) m(2)) for water to flow on a kilometer scale over relatively short geological times ( approximately 10(5) yr). Hence, active faults act as concentrated niches capable of episodically tapping resources in the bulk volume of the rock. Radiolysis and ferrous iron are potentially bases of sustainable hard-rock niches.     

Lunar exploration and development--a sustainable model

A long-term goal of space exploration is the development of a lunar settlement that will not only be largely self-sufficient but also contribute to the economy of the Earth-Moon system. Proposals for lunar mining and materials processing developments, as well as tourism-based applications, have appeared in the literature for many years. However, so great are the technical and financial difficulties associated with sustained lunar development that, more than 30 years after the end of the Apollo programme, there have been no practical advances towards this goal. While this may soon be remedied by a series of proposed unmanned orbiters, landers and rovers, the philosophy of lunar exploration and development remains the same as it has for decades: conquer, exploit, and ignore the consequences. By contrasting the well-recognised problems of Earth orbital debris and the barely recognised issue of intentional spacecraft impacts on the lunar surface, this paper illustrates the need for a new model for lunar exploration and development. This new paradigm would assign a value to the lunar environment and provide a balance between protection and exploitation, creating, in effect, a philosophy of sustainable development for the Moon. It is suggested that this new philosophy should be an integral part of any future strategy for lunar colonisation.     

Remote sensing and the first amendment

The images and information available from remote-sensing satellites are potentially valuable to a large market. The news media is part of this market, ready to make major use of new near real-time information offered by the latest technology, which can provide images with resolution of less than 10 metres. A media business consortium (‘Mediasat’) could be created. However, the US Land Remote Sensing Commercialization Act of 1984 places tough licensing restrictions on any US company wanting to put a camera into orbit. The author argues that these restrictions clash with the US Constitutional right of freedom of information, and the press's right to gather information.     

Early renal changes in 45 degrees HDT rats

Background: Both microgravity and simulated microgravity models, such as the 45HDT (45 degrees head-down tilt), cause a redistribution of body fluids indicating a possible adaptive process to the microgravity stressor. Understanding the physiological processes that occur in microgravity is a first step to developing countermeasures to stop its harmful effects, i.e., (edema, motion sickness) during long-term space flights. Hypothesis: Because of the kidneys' functional role in the regulation of fluid volume in the body, it plays a key role in the body's adaptation to microgravity. Methods: Rats were injected intramuscularly with a radioactive tracer and then lightly anesthetized in order to facilitate their placement in the 45HDT position. They were then placed in the 45HDT position using a specially designed ramp (45HDT group) or prone position (control group) for an experimental time period of 1 h. During this period, the 99mTc-DTPA (technetium-labeled diethylenepentaacetate, MW=492 amu, physical half-life of 6.02 h) radioactive tracer clearance rate was determined by measuring gamma counts per minute. The kidneys were then fixed and sectioned for electron microscopy. A point counting method was used to quantitate intracellular spaces of the kidney proximal tubules. Results: 45HDT animals show a significantly (p=0.0001) increased area in the interstitial space of the proximal tubules. Conclusions: There are significant changes in the kidneys during a 1 h exposure to a simulated microgravity environment that consist primarily of anatomical alterations in the kidney proximal tubules. The kidneys also appear to respond differently to the initial periods of head-down tilt.     

China's rise in space and US policy responses: A collision course?

China's opaque politics present particular difficulties for US space policy. Heavily invested in and reliant on space, the US will closely monitor China's burgeoning space program. New space powers, and the increasing use of space generally will further create significant challenges, most particularly to the reliance of states on space for national security. In order to maintain its space capabilities, the US will have to decide between securing this via multilateral and co-operative uses of space, or through trying to maintain a level of dominance over other space actors. While very gradually shifting away from the latter position, Washington's policy choices are complicated by the lack of a clear Chinese space strategy. While the Chinese space program, and its wider intentions, are opaque, tenure of a more cooperative approach course might prove fragile.     

Experiments to Examine the Situated Nature of Geoscientific Concepts

ABSTRACT

Ontologies are being developed in many geoscientific domains. They are typically populated with two types of concepts: upper-level concepts that apply across many or all domains, and domain concepts that apply only within a specific domain. Previous work has refined this distinction by identifying a particular type of domain concept, called a situated concept, which is dependent on specific processes (natural, social, scientific, or possibly machine) for its meaning and is instantiated amongst entities within a specific geographical and historical context. In this paper we present new support for situated geoscientific concepts, building on our previous research that argues for the importance of situations in the development and use of concepts related to geoscientific field mapping. The new results are obtained by using statistical techniques to further analyze three geologists' field data over time, to better test the hypothesis that the concepts developed by the geologists to classify objects on the map are in fact situated. The field data are compared to each other, and to the concepts developed by the team. Differences found between and within individuals' data for three map concepts provide strong support for the idea that the concepts are variably influenced by data, theory, and natural and human situations. From this increased corroboration of situated concepts we suggest two implications for domain ontologies: (1) a delineation between situated domain concepts and non-situated domain concepts; and (2) recognition that representation of reliable meaning involves the capture of historical and geographical context for situated concepts.