A Study of the Aurora of 1859

The two great auroral displays of August 28-29 and September 1-2, 1859 are studied from a collection of world-wide descriptive observations. Both auroras reached to unusually low latitudes. Red glows were reported as visible from within 23° of the geomagnetic equator in both north and south hemispheres during the display of September 1-2. It is shown that by using graphic symbols, descriptive reports may be used to indicate the significant features of an auroral display. A series of world-wide maps show the hourly locations and lowest latitude limits of auroral visibility and overhead aurora for the most active hours. They illustrate how the progress of an aurora may be followed throughout the night. Both auroras seen in North America reached their southern limits near local midnight. During the larger display of September 1-2 the aurora moved to lower latitudes and also covered a wide range in latitudes. This indicates that during great displays the auroral activity appears to expand in latitude until local midnight, at the same time moving towards the geomagnetic equator. Over large areas both displays were predominantly red. Magnetic records indicate that there were two distinct disturbances associated with the two displays. A tabulation of all known available auroral observations reported from August 28 to September 5, 1859 illustrates that by using a letter code, significant auroral activity may be recorded for use in auroral catalogues.Ye

Precautionary Saving in the Small and in the Large

The theory of precautionary saving is shown in this paper to be isomorphic to the Arrow-Pratt theory of risk aversion, making possible the application of a large body of knowledge about risk aversion to precautionary saving, and more generally, to the theory of optimal choice under risk. In particular, a measure of the strength of precautionary saving motive analogous to the Arrow-Pratt measure of risk aversion is used to establish a number of new propositions about precautionary saving, and to give a new interpretation of the Oreze-Modigliani substitution effect.

Labor Market Dynamics When Unemployment Is A Worker Discipline Device

Efficiency wage models of the effort elicitation type have important implications for labor market dynamics. These models have a wide array of discontinuous sunspot equilibria driven by extraneous variables, in addition to well-behaved equilibria characterized by continuous, slowly adjusting patterns of employment. Many aspects of actual labor markets can be replicated by these models. For example, the longer-run movements they predict in employment allow macroeconomic evidence for a large labor supply elasticity to be reconciled with panel data evidence for a small labor supply elasticity. Many testable, but as yet untested predictions about labor market dynamics can also be generated.

Incidence of Auroras and Their North-South Motions in the Northern Auroral Zone

Studies of the incidence of auroral forms and their north and south motions are made by using a close-spaced array of all-sky cameras located in the northern auroral zone at the approximate geomagnetic longitude 250°E. It is found that during the observing season 1957-58 the peak of the average auroral zone occurred at 66-67° geomagnetic latitude. Although the southern extent of auroras retreats northward after local magnetic midnight, the southward motion of the individual forms, observed at the southern edge of the auroral zone, predominates over the northward motion throughout most of the night. The data indicate the existence on any given night of a latitude position near which many auroral forms occur. The first motion of auroras incident north of this position tends to be northward, and the first motion of auroras incident south of this position tends to be southward. A curve showing the occurrence of auroral forms peaks at, and is nearly symmetrical about, local geographic midnight, but the intensity of auroral emissions measured over the celestial hemisphere remains at a high level after midnight.NSP Grant No. Y/22.6/327Ye

Precautionary saving and precautionary wealth

This is an entry for The New Palgrave Dictionary of Economics, 2nd Ed. JEL Klassifikation: C61, D11, E2

Liquidity Constraints and Precautionary Saving

Economists working with numerical solutions to the optimal consumption/saving problem under uncertainty have long known that there are quantitatively important interactions between liquidity constraints and precautionary saving behavior. This paper provides the analytical basis for those interactions. First, we explain why the introduction of a liquidity constraint increases the precautionary saving motive around levels of wealth where the constraint becomes binding. Second, we provide a rigorous basis for the oft-noted similarity between the effects of introducing uncertainty and introducing constraints, by showing that in both cases the effects spring from the concavity in the consumption function which either uncertainty or constraints can induce. We further show that consumption function concavity, once created, propagates back to consumption functions in prior periods. Finally, our most surprising result is that the introduction of additional constraints beyond the first one, or the introduction of additional risks beyond a first risk, can actually reduce the precautionary saving motive, because the new constraint or risk can hide' the effects of the preexisting constraints or risks.

Precautionary Saving and the Timing of Taxes

This paper analyzes the effects of government debt and income taxes on consumption and saving in a world of infinitely-lived households having uncertain and heterogeneous incomes. The special structure of the model allows exact aggregation across households despite incomplete markets. The effects of government debt are shown to be substantial, roughly comparable to those resulting from finite horizons, and crucially dependent on the length of time until the debt is repaid. Also, anticipated changes in taxes are shown to cause anticipated changes in consumption. Finally, an index of fiscal stance is derived.

Social Security, Retirement and Wealth: Theory and Implications

The effect of Social Security rules on the age people choose to retire can be critical in evaluating proposed changes to those rules. This research derives a theory of retirement that views retirement as a special type of labor supply decision. This decision is driven by wealth and substitution effects on labor supply, interacting with a fixed cost of working that makes low hours of work unattractive. The theory is tractable analytically, and therefore well-suited for analyzing proposals that affect Social Security. This research examines how retirement age varies with generosity of Social Security benefits. A ten-percent reduction in the value of benefits would lead individuals to postpone retirement by between one-tenth and one-half a year. Individuals who are relatively buffered from the change—because they are wealthier or because they are younger and therefore can more easily increase saving to offset the cut in benefits— will have smaller changes in their retirement ages. Authors’ Acknowledgements This work was supported by a grant from the Social Security Administration through the Michigan Retirement Research Center (Grant #10-P-98358-5). The opinions and conclusions are solely those of the authors and should not be considered as representing the opinions or policy of the Social Security Administration or any agency of the Federal Government. The authors gratefully acknowledge this support.

Presence of negative entropies in Casimir interactions

Negative entropy in connection with the Casimir effect at uniform temperature is a phenomenon rooted in the circumstance that one is describing a nonclosed system, or only part of a closed system. In this paper we show that the phenomenon is not necessarily restricted to electromagnetic theory, but can be derived from the quantum theory of interacting harmonic oscillators, most typically two oscillators interacting not directly but indirectly via a third one. There are two such models, actually analogous to the transverse magnetic (TM) and transverse electric (TE) modes in electrodynamics. These mechanical models in their simplest version were presented some years ago, by J. S. H{\o}ye et al., Physical Review E {\bf 67}, 056116 (2003). In the present paper we re-emphasize the physical significance of the mechanical picture, and extend the theory so as to include the case where there are several mediating oscillators, instead of only one. The TE oscillator exhibits negative entropy. Finally, we show explicitly how the interactions via the electromagnetic field contain the two oscillator models.Comment: 12 pages, no figure

The dynamics of the aurora. Part VII - Equatorward motions and the multiplicity of auroral arcs

Dynamic motions of Aurora 7 towards equato