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PhYSEduC 311991) PrinledinlheUK NOTES ON EXPERIMENTS'Notes on experiments' enables teachers at both school and tertiary level to share their ideas with other readers. Physics Education welcome submissions from readers who know of some simple improvement to a commercially made piece of apparatus, or who have designed a new gadget or improved a standard experiment. In particular the Editor would welcome brief descriptions of experiments devised or procedures evolved during the course or project work or investigations undertaken by students; such submissions should be made under the joint name of the teacher and the student.

Traveling convection vortices TCV are studied using a theoretical ideal MHD model for the equilibrium and perturbed plasma. In this rst approach, we do not consider the viscosity and the ow of the plasma column in the equilibrium. The linearized equations are solved using normal mode analysis. The solutions show a n m = 1 kink instability which is in good agreement with the experimental data. It is calculated numerically a growth rate of 28 minutes to be compared with experimental data, indicating a quite good result with our model. Clearly, the results indicate the behaviour of the TCV as a kind of kink instability as supported by the agreement b e t ween theoretical and experimental values for the growth rate. Also the lamentation currents calculated through the theoretical model agree quite well with the experimental observations by satellites.