Multiresolution wavelet analysis of SUMER/SOHO observations in a solar prominence

We have studied through a multiresolution wavelet analysis the oscillations in a limb prominence. Intensity fluctuations in time and height corresponding to different lines of Siiv and Oiv observed with SUMER on board SOHO have been analyzed in the wavelet bands of J₃= 1 min 36 s to 3 min 12 s and J₄=3 min 12 s to 6 min 24 s. For all species, oscillations in the J₄ band were dominant. We found relevant differences between the behavior of line D₁ (1393.76 Å) corresponding to Siiv and the set D₂ (1401.16 Å), D₃ (1404.81 Å), D₄ (1402.77 Å) corresponding to Oiv, Oiv and Siiv respectively. We also report the identification of a pulse in the intensity of the line D₁ that appears in the range of 15–20 min. This disturbance seems to travel with a speed of about 170 km s^–1.     

Preconsolidation stress in the Vega Baja and Media areas of the River Segura (SE Spain): Causes and relationship with piezometric level changes

Preconsolidation stress (σ′_p) is the maximum effective stress that a soil has suffered throughout its life. From a geotechnical point of view, preconsolidation stress has a great importance because it separates elastic and reversible deformations from inelastic and only partially irreversible deformations and marks the starting point of high compressibility. This study calculates the preconsolidation stress for 139 undisturbed soil samples from the Vega Baja and Media of the Segura river (SE Spain), using the uniaxial consolidation test and applying the method proposed by Casagrande while using a novel analytical procedure proposed by Gregory et al. [Gregory, A.S., Whalley, W.R., Watts, C.W., Bird, N.R.A., Hallet, P.D., Whitmore, A.P., 2006. Calculation of the compression index and precompression stress from soil compression test data. Soil and Till. Res., 89, 45–57] to avoid subjective interpretations of maximum curvature point. The results show overconsolidation ratio (OCR — the ratio of preconsolidation stress to current natural overburden stress) values for the 10–15 m depth of soil varying from 2 to 14 and maximum preconsolidation stresses above 800 kPa. The main causes of calculated preconsolidation identified are desiccation due to seasonal drying and wetting cycles that have induced additional stresses always lower than 42 kPa for the more superficial samples. Water level decline due to the reduction of recharge suffered by the aquifer system during periods of drought and the uncontrolled withdrawal of water is considered to be the second cause of anomalous OCR values. This second cause induces low stresses to the more superficial layers (lower than 41 kPa) that can reach values higher than 150 kPa for the deeper layers for known water level decreases. In consequence, the soils of the Vega Baja and Media of the Segura river are highly overconsolidated for the first 5 m, decreasing gradually with depth to 10–15 m deep. For samples located deeper than 15 m the soils seem to be underconsolidated, probably due to the existence of confined aquifers that cause deviations from a hydrostatic and linear pore pressure model. This fact has a huge practical significance which implies that deformations affecting superficial layers are lower than those expected for deeper layers for the same load.     

Dynamics of a Quiescent Solar Prominence Observed with the SUMER/SOHO Instrument

We present the results obtained from analyzing SUMER/SOHO observational data of a quiescent solar prominence. The studied prominence is made of complex structures. From the 1-hr data set, we derive characteristic frequencies in terms of intensity and velocity oscillations, as measured in 4 transition-region lines. The presence of different types of frequencies is detected: chromospheric oscillations and intermediate periods (6 min to 12 min). This result suggests that these oscillations are transmitted by the magnetic fields from the chromosphere to the transition region.