Tracking Streamer Blobs into the Heliosphere

In this paper, we use coronal and heliospheric images from the Solar Terrestrial Relations Observatory (STEREO) spacecraft to track streamer blobs into the heliosphere and to observe them being swept up and compressed by the fast wind from low-latitude coronal holes. From an analysis of their elongation/time tracks, we discover a “locus of enhanced visibility” where neighboring blobs pass each other along the line of sight and their corotating spiral is seen edge-on. The detailed shape of this locus accounts for a variety of east–west asymmetries and allows us to recognize the spiral of blobs by its signatures in the STEREO images: in the eastern view from STEREO-A, the leading edge of the spiral is visible as a moving wavefront where foreground ejections overtake background ejections against the sky and then fade. In the western view from STEREO-B, the leading edge is only visible close to the Sun–spacecraft line where the radial path of ejections nearly coincides with the line of sight. In this case, we can track large-scale waves continuously back to the lower corona and see that they originate as face-on blobs.