plume would imply that there has been an increase in the density through compression of the prominence.

The next assumption is in relation to the modelling of the geometry of the problem. As the plume moves at an approximately constant velocity with an elliptical head, this can be used to simplify the system under study. The first step is to remove the stem of the plume, and just leave an ellipse in the prominence material. Then as this ellipse is moving at constant velocity through (what we assume to be) a constant medium, a shift in reference frame can make the situation of an ellipse, stationary in a constant flow. The effect of a non-stationary prominence will be investigated to some extent later. Now we must consider the 3D nature of the geometry under investigation. The observed plumes are known to be caused by the magnetic Rayleigh-Taylor instability [@BERG2010; @HILL2012] It is also known that the 3D magnetic Rayleigh-Taylor instability creates filamentary structures aligned with the magnetic field [@ISO2005; @ISO2006b; @Stone2007; @HILL2012] or the bi-sector of the upper an lower magnetic fields in the case where shear is present [@Stone2007]. Therefore we can view the problem as being similar to 