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GEOPHYSICAL RESEARCH LETTERS,
VOL. 32,
L10103,
doi:10.1029/2004GL022151,
2005
Rapid evolution of magnetic decreases (MDs) and discontinuities in the solar wind: ACE and Cluster
Bruce T. Tsurutani
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
Fernando L. Guarnieri
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA Brazilian Institute for Space Research, Sao Jose dos Campos, Sao Paolo, Brazil
Gurbax S. Lakhina
Indian Institute of Geomagnetism, Mumbai, India Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Japan
Tohru Hada
Department of Earth Science and Technology, Kyushu University, Fukuoka, Japan
Abstract
An experiment was conducted to identify and measure the same magnetic decreases (MDs) and interplanetary discontinuities at
two different points in space separated by ∼0.01 AU along the radial distance from the sun. The ACE and Cluster satellite
data were used in this study. Solar wind speeds measured at Cluster were used to calculate the approximate (earlier) times
of arrival at ACE. The field component changes at both spacecraft were intercompared to ensure that the same discontinuities
were detected. Out of 7 MDs/discontinuities selected, 6 were identified at ACE. The MDs/discontinuities were identified within
7 s to 35 s of the convection times. The MD thicknesses at Cluster were substantially smaller than at ACE. The ratio of thicknesses
varied from 0.21 to 0.045. One possible interpretation of this observation is that the Alfvén wave front (rotational discontinuity)
is steepening by a factor of greater than 15 per wavelength propagated. This may have important consequences for the generation
of high frequency turbulence in interplanetary space. It is noted that the 6 discontinuities transited the ∼0.01 AU distance
from ACE to Cluster with essentially the solar wind convection speed. A possible mechanism contributing to this feature is
discussed.
Received 3
December
2004;
accepted 31
March
2005;
published 27
May
2005.
Index Terms: 2109 Interplanetary Physics: Discontinuities (7811); 2159 Interplanetary Physics: Plasma waves and turbulence; 4490 Nonlinear Geophysics: Turbulence (3379, 4568, 7863); 7836 Space Plasma Physics: MHD waves and instabilities (2149, 2752, 6050).
Read Full Article (file size: 119414 bytes) Cited by
Citation: Tsurutani, B. T., F. L. Guarnieri, G. S. Lakhina, and T. Hada
(2005),
Rapid evolution of magnetic decreases (MDs) and discontinuities in the solar wind: ACE and Cluster,
Geophys. Res. Lett.,
32,
L10103,
doi:10.1029/2004GL022151.
Copyright 2005 by the American Geophysical Union.
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