Measurement of the stochasticity of low-latitude geomagnetic temporal variations

International audienceGround magnetometer measurements of total magnetic field strength from 6 stations at low latitudes were analyzed using power spectrum and Hurst range scaling techniques. The Hurst exponents for most of these time-series were near 0.5, which indicates stochasticity, with the highest latitude stations exhibiting some persistence with Hurst exponents greater than 0.6. Although no definite correlations are evident, the relative increase of the Hurst exponent with latitude suggests the possibility that the underlying dynamics of the magnetosphere change with latitude. This result may help quantify the dynamics of the inner magnetosphere itself without the direct presence of the solar wind driver

Timing of Substorm-Associated Auroral Oscillations

Previous studies have shown that auroral luminosity oscillations are often associated with substorms. Here we examine photometer data for the magnetospheric substorm on April 1, 2000 (expansive phase onset at 0525 UT) to study the detailed timing of the auroral oscillations relative to onset. Accurate timing information for the periodicities in the photometer data were determined using the wavelet transform. We find that the oscillations occur primarily during the recovery phase. Copyright © The Society of Geomagnetism and Eart

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

Modeling and simulation of the horizontal component of the geomagnetic field by fractional stochastic differential equations in conjunction with empirical mode decomposition

In this paper, we investigate the characteristics and develop a stochastic model for the horizontal component B-x of the magnetic field at 22 stations of the global near-real-time magnetic observatory network INTERMAGNET. The model is in the form of a fractional stochastic differential equation. A method to estimate the parameters on the basis of observed data and to simulate the data using the model is given. The degree of fractional differentiation and the alpha-stability exponent of the process are employed to cluster the stations. The B-x time series possess pronounced local trends, which must be removed before modeling and simulation can be performed. This trend removal is carried out by an empirical mode decomposition. An outcome is an efficient method to simulate the B-x time series by empirical mode decomposition and fractional stochastic differential equation. The numerical results indicate the existence of two distinct clusters of the INTERMAGNET: one in the mid- and low latitudes consistent with the D-st index, and the other above geomagnetic latitude 60 degrees N consistent with the AE index. This clustering corresponds to the inner magnetosphere and the outer magnetosphere, respectively

Combating Cancer Through Public Health Practice in the United States: An In-Depth Look at the National Comprehensive Cancer Control Program

Cancer is the second leading cause of the death in the United States (U.S.). The National Comprehensive Cancer Control Program (NCCCP) is a national, public health practice program funded by the U.S. Centers for Disease Control and Prevention. The NCCCP has been planning and implementing interventions to reduce the burden of cancer since 1998. Interventions are implemented across three areas primary prevention, early detection, and survivorship using health systems and environmental changes to promote sustainable cancer control. The aim of this chapter is to provide a summary of the NCCCP, and highlight specific examples of interventions and successes to aid cancer planning in other countries. Cancer plan analyses show that all NCCCP participant cancer plans address reducing tobacco use for cancer prevention and 98% contain activities to increase colorectal cancer screening. The vast majority implement activities to improve the quality of life following a cancer diagnosis (94%). Relatively fewer cancer plans contain activities to reduce radon exposure (42%), promote human papilloma virus vaccination (62%), and incorporate the use of genomics in cancer control (56%). The examples of NCCCP activities demonstrate success in controlling cancer and other non-communicable diseases through public health practice

Organization of the magnetosphere during substorms

The change in degree of organization of the magnetosphere during substorms is investigated by analyzing various geomagnetic indices, as well as interplanetary magnetic field z-component and solar wind flow speed. We conclude that the magnetosphere self-organizes globally during substorms, but neither the magnetosphere nor the solar wind become more predictable in the course of a substorm. This conclusion is based on analysis of five hundred substorms in the period from 2000 to 2002. A minimal dynamic-stochastic model of the driven magnetosphere that reproduces many statistical features of substorm indices is discussed