We study the conditions under which spinning twisted solar jets observed by
Solar Dynamic Observatory (SDO) can become unstable against the Kelvin-Helmholtz
(KH) instability. The KH instability arises at the interface of two fluid
layers that move with different speeds. Flows are generally uniform in the two
layers, however, a strong velocity shear arises near the interface region of
these two fluids forming a vortex sheet that become unstable to the spirale-like
perturbations. When a magnetic flux tube moves along its axis, a vortex sheet
is evolved near tube's boundary which may become unstable against to the KH
instability provided that its axial velocity exceeds some critical value. This
vortex sheet causes the conversion of the directed flow energy into a turbulent
energy.
Prof. Ivan Zhelyazkov is a senior Professor at Faculty of Physics, Sofia
University and PI of the Indo—Bulgarian project from Bulgarian side. He is
working in the Kelvin-Helmholtz in the solar atmosphere. He has published
several research papers in the international journal of repute. He is visiting
for here under the Indo-Bulgarian exchange program.