Geomagnetic records of Carrington’s storm from Guatemala

The present study revisits the Carrington’s storm using the observations of geomagnetic declination (D) made in the meteorological observatory of Guatemala approximately during the 2 years preceding the storm. The available monthly data for absolute values (diurnal variation) cover the period that spans between May (April) 1857 and December 1859. The analysis of the temporal evolution of monthly means confirmed its overall good quality. Additionally, highly relevant quasi-hourly declination data was analysed for the 2 stormy days of 28 August and 2 September 1859, including complementary information on the auroral sightings on those days. The quasi-hourly data shows that an extremely large deviation (18′) of the geomagnetic declination occurred at 12–13 h (UT) on the 2 September 1859. The comparison of this disturbance with the maximum hourly variations of D recorded at other low-latitude stations during more recent major geomagnetic storms shows the reliability of the Guatemala data. Furthermore, it provides an additional confirmation of the global scale of the great Carrington’s storm.     

Numerical modeling of the impact of hurricanes on ocean dynamics: sensitivity of the Gulf Stream response to storm’s track

Ocean Dynamics - The study is focused on the disruption that a storm can cause to ocean stratification and ocean currents in a region dominated by a western boundary current and meso-scale...     

Formulation of the Caspian Sea’s legal regime using a joint zone approach

The legal regime of the Caspian Sea has been determined under Treaties 1921 and 1940 by and between Iran and former Soviet Union. In fact, we are neither to explain it nor to determine. As understood from the provisions therein, the exploitation and use of the Caspian Sea by both countries are based on the Condominium. However, there is a 10-nautical mile strip as exclusive fishing areas which have been allocated to the states under the 1940 treaty. It means that Soviet Union and Iran may benefit the marine livings resources out of that strip on an equal manner. This right also includes the seabed and underlying bed. So, the legal regime of this sea may be based on a 10-nautical mile exclusive region for all five states and the remaining part as common and joint area under an agreement until an explaining and supervising organization is established to exploit and supervise over living and non-livings resources.     

Impact of Ponderomotive Forces on the Earth’s Magnetosphere

The theory of plasma density redistribution and polar wind acceleration acceleration under the affect on the magnetosphere of the ponderomotive forces induced by the ultra-low frequency electromagnetic waves is presented. Our attention is focused mainly on the important question about the necessity of experimental verification of fairly certain theoretical predictions. It is pointed out that experimental validation is not only necessary for the development of the theory but also for replenishing the knowledge about the structure and dynamics of the near-Earth space. An original method for indirect verification is presented. The idea of this method is based on the dependence of the foreshock locations on the orientation of the field lines of the interplanetary magnetic field (IMF) in front of the magnetosphere relative to the plane of the geomagnetic equator.     

Direct Assessment of Wood’s Metal Wettability on Quartz

--A tensiometric method (Wilhelmy plate) is used to study Wood's metal dynamic wettability on specially prepared surfaces of quartz single crystals at low velocities of immersion (2 to 16 wm/s). After correction for buoyancy, the force exerted on the plate by the molten metal is used to derive the unit work of wetting n cos Š where n is the Wood's metal surface tension and Š is the interfacial contact angle. Tests at different temperatures (85, 120 and 200°C) show that below 120°C, viscosity effects cannot be neglected. At an immersion/emersion rate of 2 wm/s, n cos Š is in the range 0.417-0.444 N/m at 120°C, and 0.432-0.458 N/m at 200°C. These figures allow the conversion of injection pressures into capillary diameters during Wood's metal injection tests. The method is promising since it may be used in porous materials to check the sensitivity of the unit work of wetting n cos Š to parameters such as roughness and mineralogy, which are known to vary in a wide range within the pores and cracks of rocks.     

Experimental investigation on single person’s jumping load model

This paper presents a modified half-sine-squared load model of the jumping impulses for a single person. The model is based on a database of 22,921 experimentally measured single jumping load cycles from 100 test subjects. Threedimensional motion capture technology in conjunction with force plates was employed in the experiment to record jumping loads. The variation range and probability distribution of the controlling parameters for the load model such as the impact factor, jumping frequency and contact ratio, are discussed using the experimental data. Correlation relationships between the three parameters are investigated. The contact ratio and jumping frequency are identified as independent model parameters, and an empirical frequency-dependent function is derived for the impact factor. The feasibility of the proposed load model is established by comparing the simulated load curves with measured ones, and by comparing the acceleration responses of a single-degree-of-freedom system to the simulated and measured jumping loads. The results show that a realistic individual jumping load can be generated by the proposed method. This can then be used to assess the dynamic response of assembly structures.     

Properties and origin of energetic particles at the duskside of the Earth’s magnetosheath throughout a great storm

We study an interval of 56 h on January 16 to 18, 1995, during which the GEOTAIL spacecraft traversed the duskside magnetosheath from X ≅ −15 to −40 R_E and the EPIC/ICS and EPIC/STICS sensors sporadically detected tens of energetic particle bursts. This interval coincides with the expansion and growth of a great geomagnetic storm. The flux bursts are strongly dependent on the magnetic field orientation. They switch on whenever the B_z component approaches zero (B_z ≅ 0 nT). We strongly suggest a magnetospheric origin for the energetic ions and electrons streaming along these “exodus channels”. The time profiles for energetic protons and “tracer” O⁺ ions are nearly identical, which suggests a common source. We suggest that the particles leak out of the magnetosphere all the time and that when the magnetosheath magnetic field connects the spacecraft to the magnetotail, they stream away to be observed by the GEOTAIL sensors. The energetic electron fluxes are not observed as commonly as the ions, indicating that their source is more limited in extent. In one case study the magnetosheath magnetic field lines are draped around the magnetopause within the YZ plane and a dispersed structure for peak fluxes of different species is detected and interpreted as evidence for energetic electrons leaking out from the dawn LLBL and then being channelled along the draped magnetic field lines over the magnetopause. Protons leak from the equatorial dusk LLBL and this spatial differentiation between electron and proton sources results in the observed dispersion. A gradient of energetic proton intensities toward the Z_GSM= 0 plane is inferred. There is a permanent layer of energetic particles adjacent to the magnetosheath during this interval in which the dominant component of the magnetic field was B_z.     

Influence of Total Solar Irradiance on the Earth’s Climate

Geomagnetism and Aeronomy - The results of analysis of variations in the total solar irradiance in the 17–24th solar activity cycles and their relation to the climate global warming are...     

Comments on “Core Eigenmodes and Their Impact on the Earth’s Rotation”

Surveys in Geophysics -     

Marine radar ocean wave retrieval’s dependency on range and azimuth

The strength of the surface wave signal in marine X-band radar (MR) images strongly depends on range and azimuth (i.e., the angle between antenna look and peak wave direction). Traditionally, MR wave analysis is carried out in a set of rectangular windows covering the radar field of view (FOV). The FOV is typically partially obstructed, e.g., due to the coastline or ship superstructures. Especially for ships that are subject to regular course changes, this results in an increased variability or error associated with wave parameters. Using MR measurements from R/P FLIP, acquired off California during the 2010 US Office of Naval Research (ONR) high resolution air–sea interaction (Hi-Res) experiment, this study quantifies the dependency of the radar-based 2D wave spectrum and parameters on range and azimuth. With the help of reference data from a nearby Datawell Waverider buoy, we propose empirical methods to remove the dependency and we illustrate their efficacy.     

Reaearch on Skempton’s coefficient B based on the observation of groundwater of Changping station

Based on isotropic linear poroelastic theory and under the undrained condition,we summarize three equations connecting the Skempton’s coefficient B with the groundwater level.After analysis,we propose a method to calculate the Skempton’s coefficient B according to the relationship between water level and tidal strain.With this method we can get the value of B without the earthquake occurrence,which can provide the high frequency waves for research.Besides,we can also get the in-suit Skempton’s coefficient B...     

Coherence estimation algorithm using Kendall’s concordance measurement on seismic data

The coherence method is always used to describe the discontinuity and heterogeneity of seismic data. In traditional coherence methods, a linear correlation coefficient is always used to measure the relationship between two random variables (i.e., between two seismic traces). However, mathematically speaking, a linear correlation coefficient cannot be applied to describe nonlinear relationships between variables. In order to overcome this limitation of liner correlation coefficient. We proposed an improved concordance measurement algorithm based on Kendall’s tau. That mainly concern the sensitivity of the liner correlation coefficient and concordance measurements on the waveform. Using two designed numerical models tests sensitivity of waveform similarity affected by these two factors. The analysis of both the numerical model results and real seismic data processing suggest that the proposed method, combining information divergence measurement, can not only precisely characterize the variations of waveform and the heterogeneity of an underground geological body, but also does so with high resolution. In addition, we verified its effectiveness by the actual application of real seismic data from the north of China.     

Effects of Earth’s Lateral Inhomogeneous Structures on Coseismic Gravity Changes

Based on the perturbation method, we present a new method to study the effects of Earth’s laterally inhomogeneous structures on coseismic gravity changes caused by dislocations within a 3-D heterogeneous spherical earth model. We describe this method by six independent dislocations: A vertical strike-slip, two vertical dip-slips perpendicular to each other, and three tensile openings on three perpendicular planes. We derived the calculation formulae for the six independent dislocations. A combination of the six independent dislocations is useful to compute the effects on coseismic gravity changes resulting from an arbitrary seismic source at an arbitrary position.     

Impact of solar wind tangential discontinuities on the Earth’s magnetosphere

The collision of a solar wind tangential discontinuity with the bow shock and magnetopause is considered in the scope of an MHD approximation. Using MHD methods of trial calculations and generalized shock polars, it has been indicated that a fast shock refracted into the magnetosheath originates when density increases across a tangential discontinuity and a fast rarefaction wave is generated when density decreases at this discontinuity. It has been indicated that a shock front shift under the action of collisions with a tangential discontinuity is experimentally observed and a fast bow shock can be transformed into a slow shock. Using a specific event as an example, it has been demonstrated that solar wind tangential discontinuity affects the geomagnetic field behavior.     

Effects of hydrocarbon physical properties on caprock’s capillary sealing ability

A new mechanics formula of caprock’s capillary sealing ability has been established in this paper, in which the boundary layer resistance was considered and characterized by starting pressure gradient. The formula shows that capillary sealing ability of caprock is determined not only by the capillary force of rock and the buoyancy of hydrocarbon column, but also by the starting pressure gradient of hydrocarbons and the thickness of caprock. The buoyancy of hydrocarbon column, the starting pressure gradient of hydrocarbon, and the capillary force of caprock are affected by hydrocarbon density, hydrocarbon viscosity, and hydrocarbon-water interface tension respectively. Based on hydrocarbon property data of reservoirs of Jiyang Depression and equations from literature, the effects of hydrocarbon density, hydrocarbon viscosity, and hydrocarbon-water interface tension on the sealing ability of caprock are analyzed. Under formational conditions, the sealing ability of oil caprock can vary up to dozens times because of the variations of the oil density, oil viscosity, and oil-water interface tension. Thus, the physical characters of hydrocarbon should be considered when evaluating the capillary sealing ability of caprocks. Study of the effects of physical characters on sealing ability of caprock can provide guidance to exploring special physical property hydrocarbon resources, such as viscous oils, and hydrocarbon resources in special pressure-temperature environments.     

Simulation of tides in hydrocarbon lakes on Saturn’s moon Titan

Numerous hydrocarbon lakes have recently been detected on Saturn’s largest moon Titan, representing the only known large bodies of liquids on a planetary surface outside the Earth. In the context of comparative oceanography, tides and tidal currents in two representative lakes on Titan (Kraken Mare and Ontario Lacus) are simulated by a three-dimensional baroclinic ocean circulation model. Since the tide-generating force on Titan is an order of magnitude larger than on Earth and the gravitational acceleration is small, tides and currents are substantially larger than in Earth’s lakes and are more comparable with those in Earth’s oceans. The predicted maximum tidal range in Kraken Mare is 4 m. The tidal wave propagates around the basin of Kraken Mare, while a nearly standing tidal wave is excited in Ontario Lacus. Titan’s rotation is too slow to affect the tidal flow in any Titan’s lake. The tidal current velocity in Kraken Mare amounts to a few centimeters per second except in the vicinity of a narrow strait, where it is enhanced by an order of magnitude. In summer, when the lake is stratified, internal tides can develop. Seiches cannot be caused by tide. In the largest lakes, atmospheric tide may cause additional lake surface displacements.     

Telluric currents have no significant effect on the Earth’s core seismicity

We show that telluric currents have no effect on the formation of macrofaults in the Earth’s crust or on implementation of the intensification regime. This is mainly associated with the weakness of telluric currents and induction of the geomagnetic field.     

The Effects of the Earth’s Curvature on Gravity and Geoid Calculations

While it is obvious that large-scale gravity studies should account for the sphericity of the Earth, each case should be examined. If a geometry model is very large for the 3D-gravity calculation, it cannot be correctly defined in Cartesian coordinates. Because of the Earth’s curvature it is necessary to use spherical coordinates, the importance of which is shown in this paper. The calculation of the gravity for a cylinder reveals, 1 m above the center of the cylinder, a relative difference of 13% between the models with Cartesian and spherical coordinates.