Meeting abstract

Solar Wind 9, Nantucket, 5-9 October 1998

Abstract:
Between 1992 and 1993 Ulysses travelled gradually southwards from around 10 to 35 degrees south at distances of around 4-5 AU. In this time the spacecraft encountered a series of well developed corotating interaction regions between high speed (around 750 km/s) and slow speed solar wind streams. Towards the end of the interval the spacecraft moved below the most southerly extent of the slow solar wind stream and finally entered uninterrupted fast solar wind in late 1993. A wavelet analysis of Elsässer variables shows that, as expected, there is typically a dominant population of broad-band, outward propagating Alfvén waves (that is, high normalised cross helicity) immediately behind each CIR. There is generally a sharp cut-off in these waves at some point in the trailing edge. During some rotations regions of high cross helicity are, surprisingly, present in slow solar wind streams. Short intervals of dominant inward waves are also occasionally observed.

Power levels and spectral indices from a mulitaper spectral analysis of magnetic field and Elsässer variable data are used to estimate the dynamical age of fluctuations in different regions to investigate the effects of source and environment on the development of the fluctuations. In addition, correlations between stream interfaces and the character of the fluctuations are considered.