Since I started performing the Shiva mantra "Maha Paduka Guru Mantra" in which the feet (paduka) of Shiva rest on the crown chakra, I have been having the experience very, very much like that described below. Shiva showed me the column of light that enters where his paduka touch the the crown and how to allow the column to pass through to the base at muladhara. None of this happens without profound Surrender to the Divine. Then Shiva directed me to this document to confirm my experience: Seeking the Sidhas - Part 2 - Ramalinga Adigal
I could go into much more detail, but the below extracts give plenty of indication of the kind of development being referenced here.
‘Beyond the experience of the Divinity that can be achieved through the Ajna and the Sahasrara, the full Union with God in body and soul (deathless body) takes place when the Most High Lord accepts the absolute surrender of the disciple’.
‘These great saints saw a Column of Light rising above the Sahasrara up to the Divinity. In one who realizes the Golden Deathless Body an indissoluble bond is established with the Divinity through this Column of Light.
‘The one in whom the Column of Light is settled enjoy the continual experience on the Divinity, who, on having descended, resides in one's own Heart (as shining Sun) and fills with Himself the whole Being gradually, even the physical body (which, cell by cell, is completely transmuted up to becoming divine).
At first the above mentioned experience has not the same intensity all the time. Moved by His great Compassion, God takes the maximum care of the possible after effect in the physical body and that's why He is alternating the intensity to manifest Himself as Divine Light. Some times His resplendence is very soft whereas in other occasions It becomes the most intense, seeming that one is going to be melted in It. This experience on God fills the Self with Divine Love and Compassion, which overflow from the Heart as a river flowing endlessly towards the other beings’. ‘Little by little, God is increasing by degrees the intensity of Light and one is becoming accustomed to it, until the time comes when God manifests Himself wholly. Then the Column of Light shines from beginning to end with Its entire splendor . It isn’t visible, except in very rare occasions’. ‘This Column of Light is truly the embodied Divine Jothi. This is the Full God's Manifestation in the Earth’. ‘There was no longer the body, no longer any sensation; there was only a Column of Light rising from the place where is ordinarily the base of the body up to the place where is ordinarily the head, to form there a disk of Light like that of the moon; then from there the Column went on rising up to very far above the head to break into an immense Sun, dazzling and multi-colored, from which fell a rain of Golden Light covering the whole earth’. ‘Then slowly the Column of Light descended forming an oval of living Light, awakening and setting in motion, each in a particular way, according to a special mode of vibration, the centers which were above the head, at the place of the head, the throat, the heart, in the middle of the belly, at the base of the spine and still lower. At the height of the knees, the ascending and the descending currents joined together and the circulation thus became in a way uninterrupted enveloping the whole being in an immense oval of living Light’.
‘There is a Pillar (Column of Light) rising up from the seat of Brahma (muladhara), above the Sahasrara, and reaching up to Suddha Siva Sthana, the seat of Suddha Siva (the pure Space of the Divine which is the world of True Knowledge). It will be of the vibration of Vayu (air of life - force called Vayu Nadi) up to the Heart centre and beyond that, of the principle of Agni the fire. It is broad at the bottom and becomes finer and finer as it goes up. It is invisible to senses as it becomes infinitesimally atomic; it is imperceptible to the jeeva as it becomes infinite, and can be seen only rarely in spiritual vision. It is the Pillar of Unity without division. This is called the whole and perfect Pillar of the Divine Form, Sivakara Poorna Stambha’.