We have been talking about the flow of the breath, which creates a flow of energy in the body. The word for flow in yoga is nadi. In the nostrils three different flows of energy are created. These are known as ida, pingala and sushumna. The left nostril is connected to the ida network of nadis, the right nostril to pingala, and when both nostrils function together, the main channel or sushumna network is stimulated.
The energy flows created by the left and right swaras act something like the positive and negative currents in an electrical circuit. The left swara is the negative line, while the right is the positive. When the right nostril is flowing, it is said that pingala stimulates the body. When the left nostril is flowing, ida stimulates the mental faculties. During the time when the swara is alternating, both nostrils become active simultaneously. Then sushumna nadi is said to stimulate the atma or spiritual potential. But this usually occurs only during the period of changeover for a couple of minutes.
Sushumna nadi is the cause of spiritual actions and it is the purpose of every yogic and tantric system to activate it. Sushumna runs straight up the centre of the spine and merges with ida and pingala a little above the nasal root at ajna chakra, the point behind the eyebrow centre. It is through sushumna that the kundalini shakti, the high-
powered spiritual force, has to be channelled. When both nostrils are active, it is an indication that the sushumna passage is open. Therefore, equalizing the breath is important for it is associated with the opening of sushumna nadi.
When sushumna flows, the mental and physical energy patterns become even and rhythmic, the thoughts are stilled and the mind is calm. Therefore, it is also known as the shoonya swara. Shoonya means void. For the yogi this is the most significant type of swara because it aids in the practice of dhyana or meditation. The aim of swara yoga is therefore to develop the shoonya swara by reducing the activities of the alternating breath.