Abstract:
We present the first observational evidence of the evolution of sausage-pinch instability in active region 11295 during
a prominence eruption using data recorded on 2011 September 12 by the Atmospheric Imaging Assembly (AIA)
onboard the Solar Dynamics Observatory (SDO). We have identified a magnetic flux tube visible in AIA 304Å
that shows curvatures on its surface with variable cross-sections as well as enhanced brightness. These curvatures
evolved and thereafter smoothed out within a timescale of a minute. The curved locations on the flux tube exhibit
a radial outward enhancement of the surface of about 1–2 Mm (a factor of two larger than the original thickness
of the flux tube) from the equilibrium position. AIA 193Å snapshots also show the formation of bright knots and
narrow regions in-between at the four locations as that of 304Å along the flux tube where plasma emission is
larger compared to the background. The formation of bright knots over an entire flux tube as well as the narrow
regions in <60 s may be the morphological signature of the sausage instability. We also find the flows of confined
plasma (propagation of brightness) in these bright knots along the field lines, which indicates the dynamicity of the
flux tube that probably causes the dominance of the longitudinal field component over short temporal scales. The
observed longitudinal motion of the plasma frozen in the magnetic field lines further vanishes the formed curvatures
and plasma confinements as well as growth of instability to stabilize the flux tube.
