Roche tomography of cataclysmic variables - VII. The long-term magnetic activity of AE Aqr

We present a long-term study of the secondary star in the cataclysmic variable AE Aqr, using Roche tomography to indirectly image starspots on the stellar surface spanning 8 years of observations. The seven maps show an abundance of spot features at both high and low latitudes. We find that all maps have at least one large high-latitude spot region, and we discuss its complex evolution between maps, as well as its compatibility with current dynamo theories. Furthermore, we see the apparent growth in fractional spot coverage, fs, around 45° latitude over the duration of observations, with a persistently high fs near latitudes of 20°. These bands of spots may form as part of a magnetic activity cycle, with magnetic flux tubes emerging at different latitudes, similar to the `butterfly' diagram for the Sun. We discuss the nature of flux tube emergence in close binaries, as well as the activity of AE Aqr in the context of other stars.

National incomes and economic growth in pre-industrial Europe: insights from recent research

Pessimistic Malthusian verdicts on the capacity of pre-industrial European economies to sustain a degree of real economic growth under conditions of population growth are challenged using current reconstructions of urbanisation ratios, the real wage rates of building and agricultural labourers, and GDP per capita estimated by a range of methods. Economic growth is shown to have outpaced population growth and raised GDP per capita to in excess of $1,500 (1990 $ international at PPP) in Italy during its twelfth- and thirteenth-century commercial revolution, Holland during its fifteenth- and sixteenth-century golden age, and England during the seventeenth- and eighteenth-century runup to its industrial revolution. During each of these Smithian growth episodes expanding trade and commerce sustained significant output and employment growth in the manufacturing and service sectors. These positive developments were not necessarily reflected by trends in real wage rates for the latter were powerfully influenced by associated changes in relative factor prices and the per capita supply of labour as workers varied the length of the working year in order to consume either more leisure or more goods. The scale of the divergence between trends in real wage rates and GDP per capita nevertheless varied a great deal between countries for reasons which have yet to be adequately explained.