Lunar response to the time-varying interplanetary magnetic field and application to the ALSEP magnetometer experiment

Mathematical model for predicting lunar response to time varying interplanetary magnetic fields and its applicability to interpretation of ALSEP magnetometer dat

Electrostatic potential distribution of the sunlit lunar surface

Electrostatic potential distribution on sunlit lunar surfac

Interaction of the solar wind with a planetary ionosphere

An electrodynamic model for an ionosphere-solar wind interaction is developed based on the existence of a low beta plasma below the anemopause. The currents for the interaction are driven by the solar wind motional electric field and induce a stagnation magnetic field at the anemopause. For Venus and Mars the lower region of the ionosphere near the electron density peak has the highest conductivity, and therefore the tangential component of the induction current flows substantially in this region. The current paths close in the anemopause, which is a solar wind current sheath analogous to the magnetopause. Both the fraction of the undisturbed solar wind motional electric field, which drives the induction current, and the required fraction of incident solar wind particles, crossing the anemopause to produce this current, are shown to be small

Method for estimating the electrical conductivity of the lunar interior

Estimation method for electrical conductivity of lunar interio

Preconditioning for Allen-Cahn variational inequalities with non-local constraints

The solution of Allen-Cahn variational inequalities with mass constraints is of interest in many applications. This problem can be solved both in its scalar and vector-valued form as a PDE-constrained optimization problem by means of a primal-dual active set method. At the heart of this method lies the solution of linear systems in saddle point form. In this paper we propose the use of Krylov-subspace solvers and suitable preconditioners for the saddle point systems. Numerical results illustrate the competitiveness of this approach

Stochastic stability versus localization in chaotic dynamical systems

We prove stochastic stability of chaotic maps for a general class of Markov random perturbations (including singular ones) satisfying some kind of mixing conditions. One of the consequences of this statement is the proof of Ulam's conjecture about the approximation of the dynamics of a chaotic system by a finite state Markov chain. Conditions under which the localization phenomenon (i.e. stabilization of singular invariant measures) takes place are also considered. Our main tools are the so called bounded variation approach combined with the ergodic theorem of Ionescu-Tulcea and Marinescu, and a random walk argument that we apply to prove the absence of ``traps'' under the action of random perturbations.Comment: 27 pages, LaTe

How much does teenage parenthood affect long term outcomes? A systematic review.

Background: The rates of teenage pregnancy in the UK are relatively high. Although early entry to parenthood can be a positive experience, most studies find large adverse effects on long term outcomes for the mother, child and father, in addition to being costly for the NHS. This is why the government launched its Teenage Pregnancy Strategy in 1999. However, there is growing evidence that teenage pregnancy might be mainly an indicator of disadvantage which is the underlying cause of the negative outcomes. Methods: A systematic literature review was undertaken of studies which used a UK dataset to quantify any long term outcomes of a teenage birth upon the mother, father or child. Studies were included if they used appropriate methods to isolate the causal effect of early parenthood. The databases searched included Medline, Cochrane, EconLit and Web of Science. Results: Six studies were identified by the review; five studies considered the mother’s socioeconomic outcomes, one study reported the child’s outcomes, and no studies met the inclusion criteria for the father’s outcomes. The studies suggested that early motherhood accounts for relatively few of the negative long term socioeconomic outcomes and it is predominantly an indicator of a disadvantaged family background. Conclusion: Limited evidence is available to understand the long term outcomes associated with teenage birth within the UK for the mother, father and child. Current econometric studies suggest that effective interventions to prevent teenage pregnancies will not eradicate the poorer long term socioeconomic outcomes often associated with early motherhood. Thus policy should focus on reducing initial disadvantage in addition to preventing teenage pregnancy. Additional econometric analyses around the mothers’, fathers’ and children’s long term socioeconomic and health-related outcomes would be valuable

Hysteresis phenomenon in deterministic traffic flows

We study phase transitions of a system of particles on the one-dimensional integer lattice moving with constant acceleration, with a collision law respecting slower particles. This simple deterministic ``particle-hopping'' traffic flow model being a straightforward generalization to the well known Nagel-Schreckenberg model covers also a more recent slow-to-start model as a special case. The model has two distinct ergodic (unmixed) phases with two critical values. When traffic density is below the lowest critical value, the steady state of the model corresponds to the ``free-flowing'' (or ``gaseous'') phase. When the density exceeds the second critical value the model produces large, persistent, well-defined traffic jams, which correspond to the ``jammed'' (or ``liquid'') phase. Between the two critical values each of these phases may take place, which can be interpreted as an ``overcooled gas'' phase when a small perturbation can change drastically gas into liquid. Mathematical analysis is accomplished in part by the exact derivation of the life-time of individual traffic jams for a given configuration of particles.Comment: 22 pages, 6 figures, corrected and improved version, to appear in the Journal of Statistical Physic

Does dynamics reflect topology in directed networks?

We present and analyze a topologically induced transition from ordered, synchronized to disordered dynamics in directed networks of oscillators. The analysis reveals where in the space of networks this transition occurs and its underlying mechanisms. If disordered, the dynamics of the units is precisely determined by the topology of the network and thus characteristic for it. We develop a method to predict the disordered dynamics from topology. The results suggest a new route towards understanding how the precise dynamics of the units of a directed network may encode information about its topology.Comment: 7 pages, 4 figures, Europhysics Letters, accepte