The RHESSI Spacecraft Instrument Data Processing Unit

The Ramaty High-Energy Spectroscopic Imager (RHESSI) spacecraft is a NASA Small Explorer (SMEX) class mission. RHESSI is designed to image solar X-rays and gamma rays with high-energy resolution. The Instrument Data Processing Unit (IDPU) serves as the central RHESSI instrument on-board data-processing element. It controls and monitors the instrument operations, and provides a flexible telemetry collection and formatting system. The system responds autonomously to optimize science data collection over a wide dynamic range of conditions, handling up to 40 Mbps of telemetry during solar flares. This paper presents an overview of the IDPU hardware and software design.     

X-ray emissions from two-temperature accretion flows within a dipole magnetic funnel

We investigate the hydrodynamics of accretion channelled by a dipolar magnetic field (funnel flows). We consider situations in which the electrons and ions in the flow cannot maintain thermal equilibrium [two-temperature (2T) effects] due to strong radiative loss, and determine the effects on the keV X-ray properties of the systems. We apply this model to investigate the accretion shocks of white dwarfs in magnetic cataclysmic variables (mCVs). We have found that the incorporation of 2T effects could harden the keV X-rays. Also, the dipolar model yields harder X-ray spectra than the standard planar model if white dwarf is sufficiently massive  (≳1 M_⊙)  . When fitting observed keV X-ray spectra of mCVs, the inclusion of 2T hydrodynamics and a dipolar accretion geometry lowers estimates for white dwarf masses when compared with masses inferred from models excluding these effects. We find mass reductions ≲9 per cent in the most massive cases.     

Implications of dredging induced changes in sediment particle size composition for the structure and function of marine benthic macrofaunal communities

A meta-analysis approach was used to assess the effect of dredging induced changes in sediment composition, under different conditions of natural physical disturbance, for the structure and function of marine benthic macrofaunal communities. Results showed the sensitivity of macrofaunal communities increased as both the proportion of gravel increased and the level of natural physical disturbance decreased. These findings may be explained by the close association of certain taxa with the gravel fraction, and the influence of natural physical disturbance which, as it increases, tends to restrict the colonisation by these species. We conclude that maintaining the gravel content of surface sediments after dredging and, where practicable, locating extraction sites in areas of higher natural disturbance will minimise the potential for long-term negative impacts on the macrofauna.     

Daily precipitation distributions over the intra-Americas sea and their interannual variability

The seasonal (March to October) and interannual variability of the cumulative distribution function (CDF) of precipitation is examined for Meso-America, the eastern Pacific and western Atlantic, commonly referred to as the intra-Americas sea (IAS). Large-area precipitation CDFs were constructed over land and temperature pools greater than 28.5° C and between 26.5° and 28.5° C. The cooler waters tend to have their precipitation distributions shifted to lower values as compared to land and the western hemisphere warm pool (WHWP). The land and the WHWP have similar precipitation distributions from March to May. From June to October the land histogram of precipitation is narrower (less light and heavy rainfall) relative to the WHWP histogram. The highest probability of finding heavy to extreme precipitation over the WHWP is in June. From 1997 to 2008, in the summer months, the El Niño/Southern Oscillation (ENSO) is related to the CDFs of precipitation over land, where during El Niño there is a shift toward lower daily rain totals. There is not a strong relationship between ENSO and the CDFs of precipitation over the ocean pools. Finally, a large WHWP in May-June-July is related to the CDF of precipitation over the WHWP in October, namely a shift towards higher daily rain totals and more extreme events. The size of the July WHWP explains 75% of the variability in the frequency of rainfall greater than 50 mm within the WHWP in October, and the root mean square error between the observed points and the linear models is about 0.005. However, the reason for this apparent predictability is not simply due to a warm seasonal anomaly leading to local thermodynamic effects. The concurrent correlation between the size of the WHWP in October and the CDF of precipitation therein is small, indicating a lack of a contemporaneous response. Here it is shown through atmospheric-oceanic reanalysis that rainfall extremes in October are dependent upon the development of the Atlantic portion of the WHWP in May-June-July. Large WHWPs in these months are consistent with an early onset of the Atlantic warm pool and atmospheric instability over Central America leading to extreme precipitation events in the fall.     

An atlas of Northamptonshire the medieval and early-modern landscape

National Geographic Society (NGS) has made several changes throughout the years in their choice of map projection for their world reference maps. The Van der Crinten I map projection was used from 1922 to 1988. Then, in 1988, it was replaced by the Robinson projection. Beginning in 1998, the Winkel Tripel became the map projection of choice for NCS' world maps. Given this change, cartographers and others who make maps may be interested in using the Winkel Tripel for custom applications. The goal of this paper is to show how Winkel Tripel's complex projection equations can be programmed using Visual Basic. Those who use other languages such as C++ can use this programming example to help them create a similar algorithm in their language of choice.     

Geospatial Analysis of Space–Time Patterning of ENSO Forced Daily Precipitation Distributions in the Gulf of Mexico

The Gulf of Mexico experiences significant changes in the distribution of daily precipitation totals that are linked to the El Niño–Southern Oscillation (ENSO). This research uses geospatial techniques to examine distribution patterns of ENSO-related precipitation. Kolmogorov–Smirnov test results comparing daily rainfall distributions for El Niño and La Niña are mapped at a 1° × 1° latitude/longitude resolution, and hotspot analysis using local Moran's I is performed to identify spatial clustering. Results indicate that ENSO-forced spatial and temporal variation in daily precipitation distributions influence large areas of the Gulf of Mexico region from August through January.     

The nitrogen cycle on Mars: Impact decomposition of near-surface nitrates as a source for a nitrogen steady state

Nitrogen isotopes appear to be escaping from Mars at approximately the primordial ratio ¹⁴N/¹⁵N ≈ 275 and to have an atmospheric nitrogen depletion time scale of about 800 Myr. For the standard model of a progressive decline of an initial inventory of atmospheric nitrogen, having no source of N, the agreement of the isotopic ratio of escaping N with primitive nitrogen would be coincidental. Here we propose a steady state model in which nitrates, produced early in Mars' history, are later decomposed by the current impact flux. The detection of near-surface nitrates can discriminate between the standard and the steady state models. Based on current estimates of N loss to space, we predict a quantity of nitrates equivalent to 60 ± 30 mbars for a steady state, or a global layer of about 3 m of pure NaNO₃.     

Plate tectonic model for the oligo-miocene evolution of the western Mediterranean

This paper outlines a plate tectonic model for the Oligo-Miocene evolution of the western Mediterranean which incorporates recent data from several tectonic domains (Corsica, Sardinia, the Kabylies, Balearic promontory, Iberia, Algero-Provençal Basin and Tunisian Atlas). Following late Mesozoic anticlockwise rotation of the Iberian peninsula (including the Balearic promontory and Sardinia), late Eocene collision occurred between the Kabylies and Balearic promontory forming a NE-trending suture with NW-tectonic polarity. As a result of continued convergence between the African and European plates, a polarity flip occurred and a southward-facing trench formed south of the Kabylie—Balearic promontory suture. During late Oligocene time an E-W-trending arc and marginal basin developed behind the southward-facing trench in the area of the present-day Gulf of Lion. Opening of this basin moved the Corsica—Sardinia—Calabria—Petit Kabylie—Menorca plate southward, relative to the African plate. Early Miocene back-arc spreading in the area between the Balearic promontory and Grand Kabylie emplaced the latter in northern Algeria and formed the South Balearic Basin. Coeval with early Miocene back-arc basin development, the N-S-extension in the Gulf of Lion marginal basin changed to a more NW-SE direction causing short-lived extension in the area of the present-day Valencia trough and a 30° anticlockwise rotation of the Corsica-Sardinia-Calabria—Petit Kabylie plate away from the European plate. Early—middle Miocene deformation along the western Italian and northeastern African continental margins resulted from this rotation. During the early late Miocene (Tortonian), spreading within a sphenochasm to the southwest of Sardinia resulted in the emplacement of Petit Kabylie in northeastern Algeria.