Latitudinal variation of stochastic properties of the geomagnetic field

We explore the stochastic fractal qualities of the geomagnetic field from 210 mm ground-based magnetometers during quiet and active magnetospheric conditions. We search through 10 yr of these data to find events that qualify as quiet intervals, defined by Kp ≤ 1 for 1440 consecutive minutes. Similarly, active intervals require Kp ≥ 4 for 1440 consecutive minutes. The total for quiet intervals is ~ 4.3 x 10⁶ and 2 x 10⁸ min for active data points. With this large number of data we characterize changes in the nonlinear statistics of the geomagnetic field via measurements of a fractal scaling. A clear difference in statistical behavior during quiet and active intervals is implied through analysis of the scaling exponents; active intervals generally have larger values of scaling exponents. This suggests that although 210 mm data appear monofractal on shorter timescales, the scaling changes, with overall variability are more likely described as a multifractional Brownian motion. We also find that low latitudes have scaling exponents that are consistently larger than for high latitudes

Geomagnetic field fluctuations during the passage at the Earth's orbit of the tail of the 15?16 July 2000 ejecta

International audienceIn this work we present the analysis of the geomagnetic field fluctuations observed at different ground stations (approximately along two latitudinal arrays, separated by several hours in local time) during the passage at the Earth's orbit of the tail of the 15?16 July 2000 coronal ejecta. The time interval of interest is characterized by northward interplanetary magnetic field conditions and several changes in the solar wind dynamic pressure. We found at all stations, both in the local morning and in the local evening, simultaneous and highly coherent waves at the same discrete frequencies (~ 1.8 and ~ 3.6 mHz) and suggest a possible interpretation in terms of global compressional modes driven by an impulsive variation of the solar wind pressure. Along the array situated in the morning sector, at the highest latitudes, the higher frequency mode seems to couple with the local field line resonance; on the other hand, along the array situated in the evening sector, the characteristics of the observed fluctuations suggest that the highest latitude station could be located at the footprint of open field lines. Our results also show that solar wind pressure variations observed during the recovery phase of the storm do not find correspondence in the geomagnetic field variations, regardless of local time and latitude; conversely, some hours later continuous solar wind pressure variations find a close correspondence in the geomagnetic field variations at all stations

A precursory ULF signature for the Chi-Chi earthquake in Taiwan

ULF emission data at Lunping (epicentral distance, 120 km) have been analysed for the Chi-Chi earthquake (with magnitude 7.6 and depth of 11 km) in Taiwan which occurred on 21 September 1999. Simple intensity analyses have not yielded any significant results but we have found, based on the analysis of polarization (the ratio of vertical magnetic field component <i>Z</i> to the horizontal component <i>G</i>), that the polarization (<i>Z</i>/<i>G</i>) showed a significant enhancement for two months before the earthquake. This kind of temporal evolution of polarization seems to be very similar to previous results, so that it is highly likely that this phenomenon may be associated with the Chi-Chi earthquake. Also, the comparison of the results of polarization analyses, by changing the signal threshold, has given us an approximate intensity of the seismogenic emission of the order of the monthly mean value

Ionospheric conductivity dependence of dayside region-0, 1, and 2 field-aligned current systems: statistical study with DMSP-F7

The present study statistically examines the dependence of the intensities of dayside (MLT=8-12h) large-scale field-aligned currents (FACs) on the ionospheric conductance using the summary data of DMSP-F7 constructed by the procedure of Higuchi and Ohtani&amp;nbsp;(2000). We have found that, in the dayside region, R1 and R0 have a higher correlation between ionospheric conductivity and FAC intensity than R2, suggesting that R0 and R1 are driven by a more voltage-like source than R2. This result is consistent with the idea that R1 and R0 are driven by the interaction between the solar wind and the open magnetospheric magnetic field. We have also found that dayside FAC intensities are latitudinally well balanced when they have a three sheet structure (R0, R1 and R2); on the other hand, for a two sheet structure (R1 and R2), the intensity of R1 is larger than that of R2, so that the net current has the polarity of R1

Successful cessation of transmitting healthcare-associated infections due to Burkholderia cepacia complex in a neonatal intensive care unit in a Japanese children's hospital

<p>Abstract</p> <p>Background</p> <p><it>Burkholderia cepacia </it>strains have been known to possess the capability to cause serious infections especially in neonatal intensive care units (NICUs), and their multi-drug resistances become a severe threat in hospital settings. The aim of this investigation was to evaluate the <it>B. cepacia </it>complex infections in the NICU in Nagano Children's Hospital, Azumino 399-8288, Japan, and to report the intervention leading to the successful cessation of the outbreak.</p> <p>Methodology</p> <p>The incidence of isolation and antimicrobial susceptibilities of nosocomial <it>Burkholderia cepacia </it>complex strains during a four-year period were retrospectively examined by clinical microbiological records, and by pulsed-field gel electrophoresis analyses along with the bacteriological verification of disinfectant device itself and procedures for its maintenance routinely used in the NICU.</p> <p>Results</p> <p>During the period surveyed between 2007 and 2009, only an isolate per respective year of <it>B. cepacia </it>complex was recovered from each neonate in the NICU. However, in 2010, the successive 6 <it>B. cepacia </it>complex isolates were recovered from different hospitalized neonates. Among them, an isolate was originated from peripheral blood of a neonate, apparently giving rise to systemic infection. In addition, the hospitalized neonate with bacteremia due to <it>B. cepacia </it>complex also exhibited positive cultures from repeated catheterized urine samples together with tracheal aspirate secretions. However other 5 isolates were considered as the transients or contaminants having little to do with infections. Moreover, the 5 isolates between July and October in 2010 revealed completely the same electrophoresis patterns by means of pulsed-field gel electrophoresis analyses, strongly indicating that they were infected through the same medical practices, or by transmission of the same contaminant.</p> <p>Conclusions</p> <p>A small outbreak due to <it>B. cepacia </it>complex was brought about in the NICU in 2010, which appeared to be associated with the same genomovar of <it>B. cepacia </it>complex. The source or the rout of infection was unknown in spite of the repeated epidemiological investigation. It is noteworthy that no outbreak due to <it>B. cepacia </it>complex was noted in the NICU after extensive surveillance intervention.</p