Solar Wind Speed and Expansion Rate of the Coronal Magnetic Field during Carrington Rotation 1909

ISSN： 0038-0938

Source： Solar Physics, Vol.187, Iss.1, 1999-06, pp. : 115-122

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Abstract

The synoptic map of the solar wind speed (SWS) estimated by the computer-assisted tomography (CAT) method with interplanetary scintillation observations is constructed for the 1909 Carrington rotation. A similar synoptic map of expansion rate (RBR) of the coronal magnetic field calculated by the so-called `potential model' with the photospheric magnetic field is also constructed under the radial field assumption (RF model). These maps consist of 64 800 (180×360) data points of equal area. We examine for the first time relations between the SWS estimated by the CAT technique and the RBR calculated by the RF model. A highly significant correlation is found between the SWS and the RBR. A simple correlation coefficient is about -0.72; that is, high-velocity winds emanate from photospheric areas corresponding to a low expansion rate of the coronal magnetic field, and low-velocity winds emanate from photospheric areas of high expansion rate. This result suggests that there is some acceleration mechanism relating to the coronal field expansion.