Shear flow-interchange instability in nightside magnetotail causes auroral beads as a signature of substorm onset

A geometric wedge model of the near-earth nightside plasma sheet is used to derive a wave equation for low frequency shear flow-interchange waves which transmit $\vec{E} \times \vec{B}$ sheared zonal flows along magnetic flux tubes towards the ionosphere. Discrepancies with the wave equation result used in Kalmoni et al. (2015) for shear flow-ballooning instability are discussed. The shear flow-interchange instability appears to be responsible for substorm onset. The wedge wave equation is used to compute rough expressions for dispersion relations and local growth rates in the midnight region of the nightside magnetotail where the instability develops, forming the auroral beads characteristic of geomagnetic substorm onset. Stability analysis for the shear flow-interchange modes demonstrates that nonlinear analysis is necessary for quantitatively accurate results and determines the spatial scale on which the instability varies

Read an exclusive extract from Richard Horton’s The COVID-19 Catastrophe

This post is an exclusive extract from Chapter Three of Richard Horton’s, Editor-in-Chief of leading medical journal The Lancet, recent book The COVID-19 Catastrophe: What’s Gone Wrong and How to Stop It Happening Again. Polity Press. This is the seventh post in a six-week series: Rapid or Rushed? exploring rapid response publishing in covid times. Read the rest of the series here. As part of the series, there was a virtual roundtable featuring Professor Joshua Gans (Economics in the Age of COVID-19, MIT Press), in conversation with Richard Horton (The COVID-19 Catastrophe, Polity Press and Editor of The Lancet), Victoria Pittman (Bristol University Press) and Qudsiya Ahmed (Cambridge University Press, India

The Online Laboratory: Conducting Experiments in a Real Labor Market

Online labor markets have great potential as platforms for conducting experiments, as they provide immediate access to a large and diverse subject pool and allow researchers to conduct randomized controlled trials. We argue that online experiments can be just as valid---both internally and externally---as laboratory and field experiments, while requiring far less money and time to design and to conduct. In this paper, we first describe the benefits of conducting experiments in online labor markets; we then use one such market to replicate three classic experiments and confirm their results. We confirm that subjects (1) reverse decisions in response to how a decision-problem is framed, (2) have pro-social preferences (value payoffs to others positively), and (3) respond to priming by altering their choices. We also conduct a labor supply field experiment in which we confirm that workers have upward sloping labor supply curves. In addition to reporting these results, we discuss the unique threats to validity in an online setting and propose methods for coping with these threats. We also discuss the external validity of results from online domains and explain why online results can have external validity equal to or even better than that of traditional methods, depending on the research question. We conclude with our views on the potential role that online experiments can play within the social sciences, and then recommend software development priorities and best practices

Law’s power to safeguard global health: a Lancet–O’Neill Institute, Georgetown University Commission on Global Health and the Law

The law-–global, national, and subnational–-plays a vital, yet often underappreciated, role in safeguarding and promoting the public’s health. In this article, we launch the Lancet-O’Neill Institute, Georgetown University Commission on Global Health and the Law. Commissioners from around the world will explore the critical opportunities and challenges of using law as a tool, while evaluating the evidence base for legal interventions. The Commission aims to define and systematically describe the current landscape of law that affects global health and safety. Commissioners were chosen from disciplines that range from health, policy, and law to economics and governance. The Commission aims to present a compelling argument as to why law should be viewed as a major determinant of health and safety and how the law can be used in a powerful and innovative way to address the global burdens of injury and disease. Above all, the Commission will pursue justice, finding innovative ways to narrow existing and unconscionable health inequalitie