Abstract
We present, for the first time, measurements of arc-polarized velocity variations together with magnetic field variations associated with a large-amplitude Alfv?n wave as observed by the Wind satellite. The module of the magnetic field variance is larger than the magnitude of the average magnetic field, indicating the large amplitude of these fluctuations. When converting to the deHoffman-Teller frame, we find that the magnetic field and velocity vector components, in the plane perpendicular to the minimum-variance direction of the magnetic field, are arc-polarized, and their tips almost lie on the same circle. We also find that the normalized cross helicity and Alfv?n ratio of the wave are both nearly equal to unity, a result which has not been reported in previous studies at 1?AU. It is worthy to stress here that pure Alfv?n waves can also exist in the solar wind even near the Earth at 1?AU, but not only near 0.3?AU. Further study could be done to help us know more about the properties of pure Alfv?n wave at 1?AU that could not be figured out easily before because of the contaminations (e.g., Alfv?n waves propagating in different directions, magnetic structures, and other compressional waves) on previously reported Alfv?n wave cases.
Published Version
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