We model the highly axisymmetric planetary nebula M2-9 using a global 3-D MHD simulation. We assume that there is no high-density circumstellar gas around M2-9, because termination shocks are missing at the top of the bipolar lobes in optical images. The overall structure of our MHD solution is a self-consistent consequence of the stellar wind itself, corresponding to two kinds of circumstellar gas distributions, one a collimated flow and the other enveloping the collimated flow. Thus our model shows a ‘solitary stellar wind’ forming in a diluted circumstellar gas density.
