“There are two different energies which are in conflict – Ha and Ṭha.
Because of these two energies we are not in our natural state.
Why do they never meet?
Because there is a big obstacle in the form of a coiled serpent.
Further we add to the obstacle rather than reduce it.
Through practices we can use the fire that is in our system to slowly reduce the obstacle.
When this happens the two have the possibility of entering Suṣumnā and become one.
When this happens there is the union of Ha and Ṭha.”
– TKV Desikachar

“The terms Ha and Ṭha also represent
two extreme sides of a wavering mind.
Ha often is meant to represent the sun, Ṭha the moon.
Suṣumṇā in the middle Nāḍī.
Prāṇa in the Ha and Ṭha represents
a confused and wavering mind.
Prāṇa in the  Suṣumṇā represents a clear, steady mind.
Hence, Jñāni is one whose Prāṇa is in Suṣumṇā
and Ajñāni is one whose Prāṇa is still
in the opposite two Nāḍī, Ha and Ṭha.”
– TKV Desikachar Religiousness in Yoga
‘Various Approaches to Yoga’
Chapter Seventeen Page 246-247