During meditation, I have experienced this phenomenon frequently for the past two months. Recently, it has been occurring about once every few days, and for a certain period of time, whether it's a few hours or even just an hour, when I meditate and reach a state of stillness, I experience the same thing.

If I recall, it clearly started about two months ago, although I think there were times before that when something similar happened. However, the sensation of something happening at the ajna (third eye) between my eyebrows is something that has been happening since that time. It corresponds to the time when a strong aura began to permeate the area around my eyebrows and slightly above them, and I feel that at that time, the aura was being forced through a narrow path from the area between my eyebrows, as if opening a small passage inside.

I have a sense that I am opening the energy channel of the aura to the area between my eyebrows and the center of my head, where the pineal gland is located. Previously, this channel was not open to that extent, and I feel that it began to open at the same time that the strong aura started to permeate my forehead.

When energy tries to pass through this channel, it is narrow and has many obstacles, and every time energy tries to pass through, the various parts of my head, especially the area around my forehead, loosen and creak repeatedly.

And when energy tries to pass through the area between my eyebrows, it begins to pass from my forehead to the center of my head, although it is still a narrow channel. Then, the area between my eyebrows, which I believe corresponds to the ajna, begins to vibrate rapidly, about twice the rate of my pulse. I think this vibration is caused by the energy starting to flow.

It feels like a vibration, but depending on how I perceive it, it feels like the area between my eyebrows is "blinking" very rapidly and repeatedly, like a normal eye blinking at twice the rate of my pulse (not a full blink, but a quick half-blink). There are no physical eyes on my forehead, but I feel like the area between my eyebrows is experiencing the sensation of a normal eye blinking rapidly and repeatedly with a half-open eye.

This type of "vibration" is also described in yoga texts.

The ajna begins to emit a very refreshing and subtle vibration that is difficult to describe. (Esoteric Yoga, P207)

According to this description, it is a phenomenon that occurs in the early stages of the ajna chakra (third eye) awakening.

However, this type of vibration seems to be moving from the subtle energy dimension to the astral dimension, and it is not a very high dimension.

Perhaps, in my case, Azuna was sealed. I think that for other people, it might awaken gradually and synchronize with other chakras, but in my case, it might be that the seal in this area will be released all at once.

Probably, it's not good to force the seal to open with too much force, so I have a feeling that my own spirit, which is watching over me, will release the seal at the right time when it has reached a certain point.