Local instabilities of Alfvén waves in high speed streams

A two fluid stability analysis of an inhomogeneous solar wind plasma leads to prediction of possible instabilities of both Alfvénic and magnetoacoustic waves driven by local velocity gradients. The waves predicted to be possibly unstable have short wavelengths in comparison with the length scale of the gradients and, with different thresholds for the value of velocity shear, may have different directions of propagation with respect to the background magnetic field.We have performed a detailed study, based on Pioneer 6 magnetic and plasma data relative to several high speed streams in the solar wind, on the direction of propagation of the transverse waves which are found within the streams and on their association with velocity gradients within the stream structure. The analysis leads to the conclusion that the observed Alfvén waves may be consistent with the hypothesis of local generation through one of the above mentioned instabilities where velocity shear leads in fact to excitation of incompressible waves in directions almost parallel to the magnetic field.     

Paleoclimate and growth rates of speleothems in the northwestern Iberian Peninsula over the last two glacial cycles

Speleothem growth requires humid climates sufficiently warm to stimulate soil CO₂ production by plants. We compile 283 U/Th dates on 21 stalagmites from six cave systems in the NW coast of Spain to evaluate if there are patterns in stalagmite growth that are evidence of climatic forcing. In the oldest stalagmites, from marine oxygen isotope stage (MIS) 7–5, growth persists through the glacial period. Hiatuses and major reductions in growth rate occur during extreme minima in summer insolation. Stalagmites active during the last interglaciation cease growth at the MIS 5–4 boundary (74 ka), when regional sea-surface temperature cooled significantly. During MIS 3, only two stalagmites grew; rates were highest between 50 and 60 ka during the maximum in summer insolation. One stalagmite grew briefly at 41 ka, 36.5 and 28.6 ka, all during warm phases of the Dansgaard–Oeschger cycles. A pronounced Holocene optimum in stalagmite growth occurs from 9 to 6 ka. The cessation of most growth by 4.1 ka, coincident with broad increases in aridity over the Mediterranean and areas influenced by the North African Monsoon, suggest that regions such as NW Spain, with dominant Atlantic moisture sources, also experienced increased aridity at this time.     

Interferometric millimeter observations of water vapor on Mars and comparison with Mars Express measurements

We present interferometric mapping of the 225.9-GHz HDO and 203.4-GHz lines on Mars obtained with the IRAM Plateau de Bure facility (PdBI). The observations were performed during martian year 28 (MY28), at L_s=320.3° for the HDO line, and at L_s=324.3° for the line. The HDO line is detected at the eastern (morning) and western (evening) limbs of the northern hemisphere, corresponding to a water column density in the range 3-6 pr.-μm. The line is not detected, which is compatible with the column densities derived from the HDO line. Quasi-simultaneous far infrared measurements obtained by the Planetary Fourier Spectrometer (PFS) onboard the Mars Express spacecraft confirm our PdBI results, yielding a 5±1 pr.-μm meridionally constant water column abundance.Such a low water abundance during the southern mid-autumn of MY28 does not correspond to the standard martian climatology as observed during the previous years. It was however already retrieved from near-infrared observations performed by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) onboard the Mars Reconnaissance Orbiter spacecraft [Smith, M.D., Wolff, M.J., Clancy, R.T., Murchie, S.L. 2009. CRISM observations of water vapor and carbon monoxide. J. Geophys. Res. 114, doi: 10.1029/2008JE003288]. Our observations thus confirm that the planet-encircling dust storm that occurred during MY28 significantly affected the martian water cycle. Our observations also demonstrate the usefulness of interferometric submillimeter observations to survey the martian water cycle from ground-based facilities.     

The climate in Zafra from 1750 to 1840: history and description of weather observations

Weather observations in Zafra during the period 1750 to 1840 have been compiled and studied. Zafra was the capital of the Duchy of Feria, located in the southwest of the Iberian Peninsula. The documentary sources used in this work are weekly reports submitted to the Duke (who lived in Madrid) that contain a section describing the weather of the preceding week or less. Regular and updated meteorological information was vital to the government of this Duchy as farming and ranching constituted the bases of the economic activity in this region, allowing the estimation of crop yield and quality and a better management of the trade of agricultural products. Therefore, this documentary source is exceptional to study the climate of SW Iberia due to its continuity, homogeneity and high temporal-resolution.     

α-particle observations in the solar wind

The plasma experiment on board of the ESRO satellite HEOS-1 detects solar wind positive ions in the energy range from 200 eV/Z–16000 eV/Z. -particles have been observed for 10% of the time, from December 1968 to March 1969, when in the interplanetary medium -particle and proton bulk velocities are on average equal. The average relative abundance of -particles is 5.5 %.Although in general the two species, hydrogen and helium, have a similar behaviour, very often -particles have an independent time history. Strong discontinuities may be observed in one species, without occurring in the other, or having different characteristics. At certain times, -particles seem to behave as an independent fluid.Well defined fluxes of -particles are observed within the magnetosheath: in several cases -particles, present in the unperturbed solar wind, are found with unchanged energy spectrum through a certain layer behind the proton shock front inside the magnetosheath. This suggests that thermalization of -particles does not occur at the same place as that of protons.     

Characterization of phanerogam communities (Posidonia oceanica and Cymodocea nodosa) using side-scan-sonar images

This paper presents the most appropriate image-processing techniques available at the present time to differentiate two different seameadow communities, Posidonia oceanica and Cymodocea nodosa. The pre-processing program is an integral part of the sonar system and, therefore, is not discussed in this paper. We propose a methodology based on unsupervised classification to chart and monitor these meadows, so fundamentally important to the mediterranean ecosystem. The images used for discussion were of seabottoms in the Cabrera Archipielago in the Mediterranean Sea.     

New Millimeter Heterodyne Observations of Titan: Vertical Distributions of Nitriles HCN, HC3N, CH3CN, and the Isotopic Ratio N/N in Its Atmosphere

High sensitivity observations were performed at 1.2- and 3-mm wavelengths with the IRAM 30-m telescope (Spain) between April 1996 and December 1999 to investigate the nitrile composition of Titan's stratosphere. A part of our dataset consists of high resolution spectra of HC¹⁴N taken at 88.6 GHz as well as spectra of HC¹⁵N recorded at 258.16 GHz. From a thorough analysis of both lines and with the help of appropriate radiative transfer calculations we show that the isotopic ratio ¹⁵N/¹⁴N is strongly enhanced compared to the terrestrial value. We propose that the range 3.9-4.5 should be considered as a basis for the enrichment factor. Five individual lines of HC₃N were measured at 39-kHz resolution using a frequency-switched technique. Several CH₃CN features were recorded at 78-kHz resolution in two transitions around 147.6 and 220.7 GHz. The high spectral resolution and the good signal-to-noise ratio affecting the spectra permit us to retrieve disk-averaged vertical profiles for HCN up to 450 km and for HC₃N and CH₃CN up to 500 km. Comparison of our inferred vertical profiles with relevant results of presently published photochemical models is presented. We show that the profiles of HCN and HC₃N predicted by various authors below 450-km altitude appear inconsistent with our new observations. We find that the three distributions present very different gradients of abundance below 200-km altitude down to the condensation levels around 80 km. In the upper stratosphere HC₃N and CH₃CN have approximately the same mixing ratio of about 4×10⁻⁸ at 450 km, at least one order of magnitude lower than that of HCN. In the same time, another nitrile HC₅N has been searched for by observing four transitions located between 109 and 221 GHz. As no spectral features could be detected after several hours of integration time, we propose an upper limit for the mixing ratio equal to 4×10⁻¹⁰ assuming a uniform distribution of this compound in the lower stratosphere.     

Synchronous deposition of massive sulphide deposits in the Iberian Pyrite Belt: New data from Las Herrerías and La Torerera ore-bodies

Two small to medium sized massive sulphide deposits, Las Herrerías and La Torerera, located in the Iberian Pyrite Belt (IPB) are examined from a geological and palynostratigraphic perspective. The palynological assemblages are assignable to the Retispora lepidophyta–Verrucosisporites nitidus (LN) miospore Biozone (Latest Devonian: Latest Famennian/Strunian) of Western Europe. This age permits correlation with some of the main massive sulphide deposits dated so far in the region (viz., Tharsis, Aznalcóllar, Sotiel-Coronada or Neves-Corvo), and validates once again the hypothesis that a single mineralizing event was responsible for the genesis of most of the IPB’s massive sulphide deposits. The present study confirms that palynostratigraphy is an invaluable high-resolution biostratigraphic tool in the IPB, applicable to dating, correlation and ore-exploration.     

Mapping adaptive capacity and smallholder agriculture: applying expert knowledge at the landscape scale

The impacts of climate change exacerbate the myriad challenges faced by smallholder farmers in the Tropics. In many of these same regions, there is a lack of current, consistent, and spatially-explicit data, which severely limits the ability to locate smallholder communities, map their adaptive capacity, and target adaptation measures to these communities. To explore the adaptive capacity of smallholder farmers in three data-poor countries in Central America, we leveraged expert input through in-depth mapping interviews to locate agricultural landscapes, identify smallholder farming systems within them, and characterize different components of farmer adaptive capacity. We also used this input to generate an index of adaptive capacity that allows for comparison across countries and farming systems. Here, we present an overview of the expert method used, followed by an examination of our results, including the intercountry variation in expert knowledge and the characterization of adaptive capacity for both subsistence and smallholder coffee farmers. While this approach does not replace the need to collect regular and consistent data on farming systems (e.g. agricultural census), our study demonstrates a rapid assessment approach for using expert input to fill key data gaps, enable trans-boundary comparisons, and to facilitate the identification of the most vulnerable smallholder communities for adaptation planning in data-poor environments that are typical of tropical regions. One potential benefit from incorporating this approach is that it facilitates the systematic consideration of field-based and regional experience into assessments of adaptive capacity, contributing to the relevance and utility of adaptation plans.