Prompt acceleration of ions by oblique turbulent shocks in solar flares

Solar flares often accelerate ions and electrons to relativistic energies. The details of the acceleration process are not well understood, but until recently the main trend was to divide the acceleration process into two phases. During the first phase elctrons and ions are heated and accelerated up to several hundreds of keV simultaneously with the energy release. These mildly relativistic electrons interact with the ambient plasma and magnetic fields and generate hard X-ray and radio radiation. The second phase, usually delayed from the first by several minutes, is responsible for accelerating ions and electrons to relativistic energies. Relativistic electrons and ions interact with the solar atmosphere or escape from the Sun and generate gamma ray continuum, gamma ray line emission, neutron emission or are detected in space by spacecraft. In several flares the second phase is coincident with the start of a type 2 radio burst that is believed to be the signature of a shock wave. Observations from the Solar Maximum Mission spacecraft have shown, for the first time, that several flares accelerate particles to all energies nearly simultaneously. These results posed a new theoretical problem: How fast are shocks and magnetohydrodynamic turbulence formed and how quickly can they accelerate ions to 50 MeV in the lower corona? This problem is discussed

Energetic ion acceleration at collisionless shocks

An example is presented from a test particle simulation designed to study ion acceleration at oblique turbulent shocks. For conditions appropriate at interplanetary shocks near 1 AU, it is found that a shock with theta sub B n = 60 deg is capable of producing an energy spectrum extending from 10 keV to approx. 1 MeV in approx 1 hour. In this case total energy gains result primarily from several separate episodes of shock drift acceleration, each of which occurs when particles are scattered back to the shock by magnetic fluctuations in the shock vicinity

Cigarettes and Alcohol: Substitutes or Complements?

Taxation of cigarettes and alcohol can raise revenue and reduce consumption of goods with negative external effects. Despite medical and psychological evidence linking their consumption, little previous work has investigated the significance of cross-price effects in cigarette and alcohol consumption. We use individual-level data from the Behavioral Risk Factor Surveillance System to investigate cigarette and alcohol consumption in the US, estimating both own and cross-price elasticities. Results suggest significant cross-price effects. Specifically, we find that higher alcohol prices decrease both alcohol consumption and smoking participation (suggesting a complementarity in consumption), while higher cigarette prices tend to decrease smoking participation but increase drinking. The significance of these findings suggests that further work is warranted to better understand the social and economic relationship between cigarette and alcohol consumption.

How Much Might Universal Health Insurance Reduce Socioeconomic Disparities in Health? A Comparison of the US and Canada

A strong association between lower socioeconomic status (SES) and worse health-- the SES-health gradient-- has been documented in many countries, but little work has compared the size of the gradient across countries. We compare the size of the income gradient in self-reported health in the US and Canada. We find that being below median income raises the likelihood that a middle aged person is in poor or fair health by about 15 percentage points in the U.S., compared to less than 8 percentage points in Canada. We also find that the 7 percentage point gradient difference between the two countries is reduced by about 4 percentage points after age 65, the age at which the virtually all U.S. citizens receive basic health insurance through Medicare. Income disparities in the probability that an individual lacks a usual source of care are also significantly larger in the US than in Canada before the age of 65, but about the same after 65. Our results are therefore consistent with the availability of universal health insurance in the U.S, or at least some other difference that occurs around the age of 65 in one country but not the other, narrowing SES differences in health between the US and Canada.

Direct, physically-motivated derivation of the contagion condition for spreading processes on generalized random networks

For a broad range single-seed contagion processes acting on generalized random networks, we derive a unifying analytic expression for the possibility of global spreading events in a straightforward, physically intuitive fashion. Our reasoning lays bare a direct mechanical understanding of an archetypal spreading phenomena that is not evident in circuitous extant mathematical approaches.Comment: 4 pages, 1 figure, 1 tabl

Exact solutions for social and biological contagion models on mixed directed and undirected, degree-correlated random networks

We derive analytic expressions for the possibility, probability, and expected size of global spreading events starting from a single infected seed for a broad collection of contagion processes acting on random networks with both directed and undirected edges and arbitrary degree-degree correlations. Our work extends previous theoretical developments for the undirected case, and we provide numerical support for our findings by investigating an example class of networks for which we are able to obtain closed-form expressions.Comment: 10 pages, 3 figure

Monthly precipitation in Missouri

Cover title

Total energy budget of the plant canopy and its relationship to evapotranspiration from corn

The bulletin is a report on Department of soil research project 210 'Weather'--P. [2].Digitized 2007 AES.Includes bibliographical references (page 22)

Probability of killing freezes in Missouri

Cover title.Includes bibliographical references