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A Bimodal Model of the Solar Wind Speed

Published online by Cambridge University Press:  12 April 2016

W.A. Coles
W.A. Coles*
Affiliation:
E.C.E.Dept., University of California, La Jolla, CA 92093-0407 Phone 619-534-2703; Fax 619-534-2486;emailbcoles@ucsd.edu

Abstract

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Until the ULYSSES spacecraft reached high latitude, the only means for measuring the solar wind velocity in the polar regions was from radio scattering observations (IPS), and these remain the only way to measure the velocity near the sun. However, IPS, like many remote sensing observations, is a “line-of-sight” integrated measurement. This integration is particularly troublesome when the line-of-sight passes through a fast stream but that stream does not occupy the entire scattering region. Observations from the HELIOS spacecraft have shown that the solar wind has a bimodal character which becomes more pronounced near the sun. Recent observations from ULYSSES have confirmed that this structure is clear at high latitudes even at relatively large solar distances. We have developed a method of separating the fast and slow contributions to an IPS observation which takes advantage of this bimodal structure. In this paper I will describe the technique and its application to IPS observations made using the receiving antennas of the EISCAT incoherent backscatter radar observatory in northern Scandinavia.

Keywords

solar windplasmainterplanetary scintillation
Type
Quasi-Static Structures
Information
International Astronomical Union Colloquium , Volume 154: Solar and Interplanetary Transients , 1996 , pp. 87 - 96
Copyright
Copyright © Kluwer 1997

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