The Malbim elucidates this in the following way. The manifestation of evil in this world is destruction of varying forms and degrees. Destruction exists only in the physical realm. Hence, the Satan can carry out his functions only within the perimeters of this world. He must, therefore, spend his time meandering around the earth.
Destruction manifests itself in three ways.
By way of the natural vulnerability of animate objects to disease, death and their subsequent decomposition. Death and havoc inflicted by violent eruptions of forces of nature and disease. Acts of folly and wickedness perpetrated by man. The world of the spiritual is by its very nature immune to these phenomena. This means that the Satan can accomplish his mission only in the physical world.