All Figures

$\begin{figure} \par\includegraphics[width=12cm,clip]{9777fig1.eps}\end{figure}$ Figure 1: Geometry of observation. ( Left panel) Type III source on the spiral open magnetic field line and the locations of Wind and Ulysses in the HEEC (Heliocentric Earth Ecliptic) coordinate system xyz. ( Right panel) Source-centered reference frame x'y'z': the x'-axis is tangent to the open magnetic field line passing the source anti-sunward; the z'-axis is in the plane defined by the x'-axis and the vertical to the ecliptic plane, oriented to ecliptic North; the y'-axis completes the orthogonal right-handed coordinate system. The direction of Wind and Ulysses is defined by the longitude $\varphi$ and latitude $\theta$ relative to the source frame.
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In the text

$\begin{figure} \par\includegraphics[width=12cm,clip]{9777fig2.eps}\end{figure}$ Figure 2: The flux density time profile of a type III burst observed by Wind ( top) and Ulysses ( bottom) on 17 June 1996 at 196 kHz. The continuous curve above background represents the actual burst intensity profile. The lower curve (full circles), denoted $S_{\rm W}(t)$ and $S_{\rm U}(t)$ , shows the same burst profile, but with the background removed. The burst is seen to occur between the onset time $t_{\rm onset}$ and end time $t_{\rm end}$ (see text for exact definition).
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In the text

$\begin{figure} \par\includegraphics[width=15cm]{9777fig3.eps}\end{figure}$ Figure 3: (a) Type III burst energy ratios R measured from Wind (circles) and Ulysses (triangles), at all selected frequencies and for all relative latitudes $\theta$ of the spacecraft, $\theta _{\rm W}$ and $\theta _{\rm U}$ , as a function of the longitudes $\varphi$ of Wind and Ulysses, $\varphi _{\rm W}$ and $\varphi _{\rm U}$ , relative to the source (in coordinates x'y'z', Fig. 1). Different absolute values of latitude $\theta$ are indicated by a color bar. Averaged values of R in $20^\circ$ bins of longitude $\varphi$ are plotted as black full circles. (b) Energy ratios R measured from Wind (circles) and Ulysses (triangles), at all selected frequencies and for all relative longitudes $\varphi$ of the spacecraft, $\varphi _{\rm W}$ and $\varphi _{\rm U}$ , as a function of the latitudes $\theta$ of Wind and Ulysses, $\theta _{\rm W}$ and $\theta _{\rm U}$ , relative to the source. Different absolute values of $\varphi$ indicated by the color bar. Averaged values of R in $20^\circ$ bins of $\theta$ plotted as black full circles.
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In the text

$\begin{figure} \par\includegraphics[width=11cm,clip]{9777fig4.eps}\end{figure}$ Figure 4: The diagram in longitude $\varphi$ relative to the source, with the fitted values of the amplitude a and shift $\varphi _0$ , is plotted as a continuous line as ${\rm log}_{10}D(\varphi )$ vs. $\varphi$ , in different frequency ranges. The diagram data (see definition in the text) are averaged in $20^\circ$ bins of $\varphi$ and plotted (black circles with scatter bars) vs. $\varphi$ . As the frequency decreases, the shift $\varphi _0$ to east of the local magnetic field direction increases and the amplitude a of the cosine diagram decreases.
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In the text

$\begin{figure} \par\includegraphics[width=12cm,clip]{9777fig5.eps}\end{figure}$ Figure 5: The diagram in latitude $\theta$ relative to the source, with the fitted values of the amplitude and shift, is plotted as a continuous line as ${\rm log}_{10}D(\theta )$ vs. $\theta$ , in different frequency ranges. The diagram data (see definition in the text) are averaged in $20^\circ$ bins of $\theta$ and plotted (black circles with scatter bars) vs. $\theta$ . No significant tilt is seen in the diagram. A weak directivity is observed equatorward at highest frequencies. At low frequency, the diagram is nearly isotropic.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{9777fig6.eps}\end{figure}$ Figure 6: Schematic interpretation of the eastward (equatorward) shift of the type III emission diagram in longitude (latitude) relative to the local open-field direction at the source. The type III electrons travel outward along spiral open-field lines from the associated flare sites in active regions. Along these paths, the solar wind escapes faster than in the surrounding areas filled with structures of closed-field lines. At some distance farther out, the faster wind catches up with the ambient slower wind and produces a density compression that leads to a transverse density gradient $\nabla n_{\rm e}$ directed westward (poleward) of the open-field direction. This in turn results in a refractive index gradient $\nabla \mu = - \nabla n_{\rm e}$ , oriented eastward (equatorward) in the opposite sense of the density gradient. Radiation is thus bent in the eastward (equatorward) direction as observed.
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In the text