Evaluation of Peak Current Polarity Retrieved by the ZEUS Long-Range Lightning Monitoring System

This letter presents the first assessment of a newly developed polarity retrieval scheme augmenting a very low frequency (VLF) long-range lightning detection network (named ZEUS). The polarity scheme uses extremely low frequency (ELF) in conjunction with the VLF waveform. The measured ELF signal is compared with the simulated ELF signal to extract the polarity sign. This comparison also produces correlation coefficients that are used to assign four confidence index categories on the polarity sign. This letter presents polarity results for a period of ZEUS network operation from November 26 to December 15, 2004. Assessment of the polarity measurements is conducted through comparisons against the Brazilian lightning network Rede Integrada Nacional de Detecccedilatildeo de Descargas Atmosfeacutericas (RINDAT) that uses a well-established lightning location technology. Contingency test analysis shows that algorithm performance is consistent with the assigned confidence level, e.g., at medium confidence level, the algorithm has a 5% bias, whereas at high level, perfect agreement is shown with RINDAT. Peak current strength was found not to influence the accuracy of the polarity retrieval     

Further details on the applicability of Thellier paleointensity method: The effect of magnitude of laboratory field

Twenty years after Tanaka and Kono's pioneering contribution (Tanaka and Kono, 1984), we give some new details on the effect of applied field strength during Thellier paleointensity experiments. Special attention is paid to the relation of magnitude of laboratory field and Coe's quality factors (Coe et al., 1978). Full thermoremanent magnetizations were imparted on natural samples containing low-Ti titanomagnetites of pseudo-single domain structure in a 40-μT magnetic field from 600?°C to room temperature. The samples were subjected to the routine Thellier procedure using a wide range of applied laboratory fields. Results indicate that values of laboratory fields may be accurately reproduced within 2% of standard error. The quality factors, however, decrease when the magnitude of ‘ancient’ field does not match to applied laboratory fields. To cite this article: J. Morales et al., C. R. Geoscience 338 (2006).     

ROCESSES OF EPHEMERAL GULLY EROSION

IINTRoDUCTIONEphemeralgulliesaresmallerosionalchannelsonagriculturalIandscapescausedbytheconcentrationofoverlandflowtypicallybetweentwoopposingslopes(ahollow),oftenformedduringasingIerainfaIlevent.Sincethescouredsoilvolumeisnotverylargewithinthesegullies,farmerscaneasilyrefillthem.Ingeneral,ephemeralgulliescanreappearatornearthesamelocationonayearlybasisbecausethesurfacetopograPhyofthefielddoesnotchangeappreciably.Mostephemeralgulliesoccuroncultivatedfieldswithhighlyerodiblesoils,withlit…     

Ammonia observations of the nearby molecular cloud MBM 12

We present NH₃(1,1) and (2,2) observations of MBM 12, the closest known molecular cloud (65-pc distance), aimed at finding evidence for on-going star formation processes. No local temperature (with a T _rot upper limit of 12 K) or linewidth enhancement is found, which suggests that the area of the cloud that we have mapped (15-arcmin size) is not currently forming stars. Therefore this nearby 'starless' molecular gas region is an ideal laboratory to study the physical conditions preceding new star formation.
A radio continuum source has been found in Very Large Array archive data, close to but outside the NH₃ emission. This source is likely to be a background object.     

Tree-ring reconstructed dry season rainfall in Guatemala

Climate Dynamics - Drought in Guatemala has negative consequences for agriculture and potable water supplies, particularly in regions of the country with highly seasonal rainfall. General...