Simulation of the solar magnetic field in a magnetic cloud expanding toward the Earth. The Sun is at left, and the green asterisk at right represents the Earth. The green asterisk to the left near the Sun corresponds to a distance of 30 solar radii. The color scheme: red is strong magnetic field of the order of a gauss and dark blue is weak magnetic field of the order of several nano tesla (nT). This theoretical example is discussed in Chen and Garren [1993] .

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