A statistical analysis of hard X-Ray solar flares

In this study we perform a statistical study on, 8319 X-Ray solar flares observed with the Hard X-Ray Burst Spectrometer (HXRBS) on the Solar Maximum Mission satellite (SMM). The events are examined in terms of the durations, maximum intensities, and intensity profiles. It is concluded that there is no evidence for a correlation between flare intensity, flare duration, and flare asymmetry. However, we do find evidence for a rapid fall-of in the number of short-duration events.     

Evaporation and condensation of corundum and silicon carbide grains around the supernova SN1987A in the large magellanic cloud

We investigate the evaporation and condensation of corundum and silicon carbide grains around the supernova SN1987A. We predict the time after outburst of the interaction of the condensed dust with pre-existing dust, with a view to undertaking observations with future instrumentation such as the Infra-Red Space Observatory.     

The Kwakshua Watersheds Observatory,central coast of British Columbia,Canada

The Kwakshua Watersheds Observatory (KWO) is an integrative watersheds observatory on the coastal margin of a rain-dominated bog-forest landscape in British Columbia (BC), Canada. Established in 2013, the goal of the KWO is to understand and model the flux of terrestrial materials from land to sea – the origins, pathways, processes and ecosystem consequences – in the context of long-term environmental change. The KWO consists of seven gauged watersheds and a network of observation sites spanning from land to sea and along drainage gradients within catchments. Time-series datasets include year-round measurements of weather, soil hydrology, streamflow, aquatic biogeochemistry, microbial ecology and nearshore oceanographic conditions. Sensor measurements are recorded every 5 min and water samples are collected approximately monthly. Additional observations are made during high-flow conditions. We used remote sensing to map watershed terrain, drainage networks, soils and terrestrial ecosystems. The watersheds range in size from 3.2 to 12.8 km², with varying catchment characteristics that influence hydrological and biogeochemical responses. Despite local variation, the overall study area is a global hotspot for yields of dissolved organic carbon, dissolved organic nitrogen and dissolved iron at the coastal margin. This observatory helps fill an important gap in the global network of observatories, in terms of spatial location (central coast of BC), climate (temperate oceanic), hydrology (very high runoff, pluvial regime), geology (igneous intrusive, glacially scoured), vegetation (bog rainforest) and soils (large stores of organic carbon).     

Tephrochronology,magnetostratigraphy and mammalian faunas of Middle and Early Pleistocene sediments at two sites on the Old Crow River,northern Yukon Territory,Canada

Alluvial and lacustrine sediments exposed beneath late Pleistocene glaciolacustrine silt and clay at two sites along the Old Crow River, northern Yukon Territory, are rich in fossils and contain tephra beds. Surprise Creek tephra (SZt) occurs in the lower part of the alluvial sequence at CRH47 and Little Timber tephra (LTt) is present near the base of the exposure at CRH94. Surprise Creek tephra has a glass fission-track age of 0.17 ± 0.07 Ma and Little Timber tephra is 1.37 ± 0.12 Ma. All sediments at CRH47 have a normal remanent magnetic polarity and those near LTt at CRH94 have a reversed polarity — in agreement with the geomagnetic time scale. Small mammal remains from sediments near LTt support an Early Pleistocene age but the chronology is not so clear at CRH47 because of the large error associated with the SZt age determination. Tephrochronological and paleomagnetic considerations point to an MIS 7 age for the interglacial beds just below SZt at CRH47 and at Chester Bluffs in east-central Alaska, but mammalian fossils recovered from sediments close to SZt suggest a late Irvingtonian age, therefore older than MIS 7. Further studies are needed to resolve this problem.     

Using Mg Isotopes to Trace Cyanobacterially Mediated Magnesium Carbonate Precipitation in Alkaline Lakes

This study assesses the potential use of Mg isotopes to trace Mg carbonate precipitation in natural waters. Salda Lake (SW Turkey) was chosen for this study because it is one of the few modern environments where hydrous Mg carbonates are the dominant precipitating minerals. Stromatolites, consisting mainly of hydromagnesite, are abundant in this lake. The Mg isotope composition of incoming streams, groundwaters, lake waters, stromatolites, and hydromagnesite-rich sediments were measured. Because Salda Lake is located in a closed basin, mass balance requires that the Mg isotopic offset between Lake Salda water and precipitated hydromagnesite be comparable to the corresponding offset between Salda Lake and its water inputs. This is consistent with observations; a ??²⁶Mg offset of 0.8?C1.4??? is observed between Salda Lake water and it is the incoming streams and groundwaters, and precipitated hydromagnesite has a ??²⁶Mg 0.9?C1.1??? more negative than its corresponding fluid phase. This isotopic offset also matches closely that measured in the laboratory during both biotic and abiotic hydrous Mg carbonate precipitation by cyanobacteria (Mavromatis, V., Pearce, C., Shirokova, L. S., Bundeleva, I. A., Pokrovsky, O. S., Benezeth, P. and Oelkers, E.H.: Magnesium isotope fractionation during inorganic and cyanobacteria-induced hydrous magnesium carbonate precipitation, Geochim. Cosmochim. Acta, 2012a. 76, 161?C174). Batch reactor experiments performed in the presence of Salda Lake cyanobacteria and stromatolites resulted in the precipitation of dypingite (Mg₅(CO₃)₄(OH)₂·5(H₂O)) and hydromagnesite (Mg₅(CO₃)₄(OH)₂·4H₂O) with morphological features similar to those of natural samples. Concurrent abiotic control experiments did not exhibit carbonate precipitation demonstrating the critical role of cyanobacteria in the precipitation process.     

The Last Piece Is You

Abstract

This article presents the cartographic outcome of a 3-year collaboration with Penobscot Nation Cultural & Historic Preservation to map the traditional place names of Penobscot territory in the state of Maine. After a consideration of the challenges of mapping Indigenous place names, I describe my cartographic contribution to the project, to transform the map design using the tools of narrativity and translation. Initial insights about Penobscot place names then led to wider insights regarding Indigenous place names and traditional cartography, through a comparison to similar practices in the place name traditions of other communities. I then explain how these insights influenced the design of the map itself.     

Revisiting the Borrobol Tephra

The Borrobol Tephra has been identified as one of the key tephra horizons for the Lateglacial time period but it also exemplifies many of the promises and problems of tephrochronology. Additional horizons with similar major element composition and approximately the same age have been identified around the North Atlantic region. Here, we revisit the Borrobol Tephra identified at two Swedish sites, Hässeldala port and Skallahult, and also the Borrobol type‐site in Scotland. We present the first set of minor element data (trace and rare earth analyses) along with new analyses of major elements from these three sites. The analysed minor and the trace elements have a similar signature; however, the glass from the Scottish type‐site seems to imply two populations. To answer if this truly represents two populations, or if it reflects magmatic differentiation additional and larger data sets of minor elements are needed. The new major elements are compared to other Borrobol‐type tephras identified in the North Atlantic region. Our results are in line with earlier investigations, which showed no differences in major elements. Further, comparison of minor elements from glass analyses from our sites with those for eruptions associated with Icelandic central volcanoes implies an Icelandic origin for the Borrobol‐type tephras.