Observations of the 3D coronal structure over a solar cycle

Abstract

Solar rotational tomography is applied to almost eleven years of LASCO C2/SOHO data, revealing for the first time the structural behavior of streamers over almost a full solar activity cycle. Streamers are most often shaped as extended, narrow plasma sheets. The sheets can be extremely narrow at times (<=0.14×10⁶ km at 4R_solar). This is over twice their heliocentric angular thickness at 1 AU. For most of the activity cycle, streamers share the same latitudinal extent as filaments on the disk, showing that large-scale stable streamers are closely linked to the same large-scale photospheric magnetic configuration which give rise to large filaments. There is considerable differential rotation of streamers at high latitudes, which makes comparison between disk and coronal structure complicated. The presence of differential rotation has implications for many areas of coronal and heliospheric research.