Beyond slash-and-burn: The roles of human activities,altered hydrology and fuels in peat fires in Central Kalimantan,Indonesia

Near-annual landscape-scale fires in Indonesia's peatlands have caused severe air pollution, economic losses, and health impacts for millions of Southeast Asia residents. While the extent of fires across the peatland surface has been widely attributed to widespread peatland drainage for plantation agriculture, fires that transition from surface into sub-surface soil-based fires are the source of the most dangerous air pollution. Yet the mechanisms by which this transition occurs have rarely been considered, particularly in diversely managed landscapes. Integrating physical geography methods, including active fire scene evaluations and hydrological monitoring, with qualitative methods such as retrospective fire scene evaluations and semi-structured interviews, this article discusses how and why sub-surface peat fire transition occurs in an intensively altered peatland ecosystem in Indonesia's Central Kalimantan province. We demonstrate that variable water table levels and flammable surface vegetation (fire fuels) are co-produced socio-political and biophysical phenomena that enable the conditions in which surface fire is likely to transition into peat fire and increase landscape vulnerability to ongoing, uncontrollable annual fires. This localized understanding of peat fire transition counters normative causal narratives of tropical fire such as ‘slash-and-burn’, with implications for the management of new fire regimes in inhabited landscapes.     

A new approach for measuring surface hydrological connectivity

The development of surface hydrological connectivity is a key determinant of flood magnitude in drylands. Thresholds in runoff response may be reached when isolated runoff-generating areas connect with each other to form continuous links to river channels, enabling these areas to contribute to flood hydrographs. Such threshold behaviour explains observed nonlinearities and scale dependencies of dryland rainfall–runoff relationships and complicates attempts at flood prediction. However, field methods for measuring the propensity of a surface to transmit water downslope are lacking, and conventional techniques of infiltration measurement are often inappropriate for use on non-agricultural drylands. Here, we argue for a reconceptualization of the dryland surface runoff process, suggesting that the downslope transfer of water should be considered alongside surface infiltration; that is, there is a need for the “aggregated” measurement of infiltration and overland flow hydraulics. Surface application of a set volume of water at a standardized rate generates runoff that travels downslope; the distance it travels downslope is determined by infiltration along the flow, integration of flow paths, and flow resistance. We demonstrate the potential of such a combined measurement system coupled with structure-from-motion photogrammetry to identify surface controls on runoff generation and transfer on dryland hillslopes, with vegetation, slope, surface stone cover, and surface roughness all having a significant effect. The measurement system has been used on slopes up to 37° compared with the flat surface typically required for infiltration methods. On average, the field workflow takes ~10–15 min, considerably quicker than rainfall simulation. A wider variety of surfaces can be sampled with relative ease, as the method is not restricted to stone and vegetation-free land. We argue that this aggregated measurement represents surface connectivity and dryland runoff response better than standard hydrological approaches and can be applied on a much greater variety of dryland surfaces.     

Expressions to determine temperatures and emission measures for solar X-ray events from GOES measurements

We have developed expressions which give the effective color temperatures and corresponding emission measures for solar X-ray events observed with instruments onboard any of the GOES satellites. Since 1976, these satellites have been used to monitor continuously the full-Sun X-ray emission in two broadband wavelength intervals (approximately 0.5–4 Å and 1–8 Å) with a time resolution of 3 s. To simulate the solar X-ray input at a variety of plasma temperatures, we used theoretical spectra provided by D. L. McKenzie. These spectra were folded through the wavelength dependent transfer functions for the two GOES detectors as given by Donnelly et al. (1977). The resulting detector responses and their ratio as a function of plasma temperature were then fit with simple analytic curves. Over the entire range between 5 and 30 million degrees, these fits reproduce the calculated color temperatures within 2% and the calculated emission measures within 5%. With the theoretical spectra provided by McKenzie, we can determine similar expressions for any pair of broadband X-ray detectors whose sensitivities are limited to wavelengths between 0.2 and 100 Å.     

Impact and explosion crater ejecta,fragment size,and velocity

A model was developed for the mass distribution of fragments that are ejected at a given velocity for impact and explosion craters. The model is semiempirical in nature and is derived from (1) numerical calculations of cratering and the resultant mass versus ejection velocity, (2) observed ejecta blanket particle size distributions, (3) an empirical relationships between maximum ejecta fragment size and crater diameter, (4) measurements of maximum ejecta size versus ejecta velocity, and (5) an assumption on the functional form for the distribution of fragments ejected at a given velocity. This model implies that for planetary impacts into competent rock, the distribution of fragments ejected at a given velocity is broad; e.g., 68% of the mass of the ejecta at a given velocity contains fragments having a mass less than 0.1 times a mass of the largest fragment moving at that velocity. Using this model, we have calculated the largest fragment that can be ejected from asteroids, the Moon, Mars, and Earth as a function of crater diameter. The model is unfortunately dependent on the size-dependent ejection velocity limit for which only limited data are presently available from photography of high explosive-induced rock ejecta. Upon formation of a 50-km-diameter crater on an atmosphereless planet having the planetary gravity and radius of the Moon, Mars, and Earth, fragments having a maximum mean diameter of ≈30, 22, and 17 m could be launched to escape velocity in the ejecta cloud. In addition, we have calculated the internal energy of ejecta versus ejecta velocity. The internal energy of fragments having velocities exceeding the escape velocity of the moon (～2.4 km/sec) will exceed the energy required for incipient melting for solid silicates and thus, the fragments ejected from Mars and the Earth would be melted.     

Hyperion: Analysis of Voyager observations

A total of 82 images of Hyperion was returned by the Voyager spacecraft; the most detailed views have a nominal resolution of 8.7 km/line pair. Hyperion had a rotation period of about 13 days and a spin vector lying close to its orbital plane at the time of the Voyager 2 encounter in 1981. The satellite's shape is very irregular, and cannot be approximated suitably by an ellipsoid. The largest cross section (A × C) is about 370 × 225 km; the B × C cross section is approximately 280 × 225 km. Most prominent among the surface features is a 120-km-diameter crater with an estimated depth of 10 km, and a series of arcuate scarps 300 km long that have relief in excess of 5 km. The density of large craters of Hyperion is smaller than that on other small Saturnian satellites and suggests the possibility that the last significant fragmentation of Hyperion occurred near the end of or after initial heavy bombardment. Voyager photometry yields an average normal reflectance of the surface material of 0.21 in the clear filter (0.47 μm) and evidence of slight albedo mottling over the surface. The disk-integrated phase coefficient between phase angles of 22° and 82° is 0.018 mag/de; there is little indication of a strong opposition effect in Voyager data down to phase angles of 3°. Hyperion's average color is definitely redder than that of Phobe, but matches that of the dark material on the leading hemisphere of Iapetus quite well. The satellite's albedo and color are consistent with those of contaminated water ice but since no mass determinations of Hyperion exist we do not know whether the bulk composition is icy or rocky.     

S-asteroids 387 Aquitania and 980 Anacostia: Possible fragments of the breakup of a spinel-bearing parent body with C03/CV3 affinities

Abstract— Asteroids 387 Aquitania and 980 Anacostia are anomalous members of the S-class. Their reflectance spectra exhibit a strong broad absorption feature longwards of 1.5 μm and no significant feature near 1 μm. Their spectra indicate the presence of spinel, an aluminum-magnesium oxide mineral commonly present in inclusions in CV3 and CO3 meteorites. Spinel probably makes up only a small percentage of the surface assemblages of these asteroids, but its spectral effect may be enhanced by its presence in fine-grained white inclusions in immature asteroid regoliths. It is speculated that Aquitania and Anacostia represent material formed in the same nebular zone as the CV3 and CO3 chondrites but either: A) at an earlier time in the nebula when such inclusions might have been a relatively larger fraction of the nebular grain population, or B) in local regions where nebular processes (e.g., settling to the midplane) had concentrated such inclusions. The close similarity of two orbital elements (a, i) suggests that Aquitania and Anacostia may be members of a partially dispersed asteroid family produced by the early disruption of a spinel-bearing parent body.     

Hamilton's equations of motion for non-conservative systems

This paper deals with the Hamilton equations of motion and non conservative forces. The paper will show how the Hamilton formalism may be expanded so that the auxiliary equations for any problem may be found in any set of canonical variables, regardless of the nature of the forces involved. Although the expansion does not bring us closer to an analytical solution of the problem, it's simplicity makes it worth noticing.The starting point is a conservative system (for instance a satellite orbiting an oblate planet) with a known Hamiltonian (K) and canonical variables {Q, P}. This system is placed under influence of a non-conservative force (for instance drag-force). The idea is then to use, as far as possible, the same definitions used in the conservative problem, in the process of finding the auxiliary equations for the perturbed system.     

COMMUTING DISTANCE AND GENDER AMONG NONMETROPOLITAN UNIVERSITY EMPLOYEES*

The applicability of metropolitan-derived explanations of gender differences in worktrip lengths is examined based on a sample of 435 university employees in the nonmetropolitan town of Blacksburg, VA. Women's worktrips are found to be longer than men's in contrast to metropolitan findings. This pattern results from the interaction of spatial structures of housing and employment with women's lower incomes, gender segregation of employment, and the tendency for married women to find jobs after their residence is established. Upward trends in female labor force participation rates and in nonmetropolitan growth require continued analysis of their joint impact on women's spatial behavior.