I have read about 'Jhana' in Ajahn Brahm's book, 'Mindfulness, bliss and beyond'. It looks like, from his teaching of Theravada Buddhism, 'Jhana' is a pre-requisite to attain 'Nirvana'.
I want to ask, is there anything similar to 'Jhana' in Zen.
From my readings it does not seem it's 'Satori'.
Zen and Jhana are the same word. Jhana is a word in the original spoken language. In Sanskrit it is written as Dhyana. Channa or Chan is how it came to Chinese language, and Zen is how it subsequently came into the Japanese (in English transliteration).
Jhana or Zen means the mind of meditation.
If you ever heard the phrases "attain the state of Zen" or "show me your Zen" - that refers to the same practice/result as Jhana. (The popular image that it refers to being a crazy wacko is a modern misunderstanding. "Attaining Zen" is breaking through to spontaneous clarity as a result of quality meditation practice.)
Of course if you are looking for the one-to-one Zen equivalents of each of the four jhanas or the eight jhanas, you will be disappointed - because such cut-and-dry categorization of practical experience would be very much against the spirit of Zen which emphasizes the first-hand discovery and learning-by-doing while avoiding the step-by-step instructions a-la Theravada as a dangerous trap for the mind. So in Zen everything is a little more fluid and the practice of meditation is not split in discrete phases. Nevertheless, the kind of meditation practiced in Zen is an authentic Jhana, functionally equivalent to the fourth Jhana of Theravada Buddhism.
Now, if you expand your scope beyond Zen and take a look at Vajrayana, it has two types of meditation closely associated with the first and second/third jhanas. I'm talking about Generation-phase and Completion-phase meditations correspondingly.
I imagine someone daring might combine the traditions and practice the Generation-, then the Completion-, then the Zazen/Shikantaza-meditation with great results.
When a person doesn't eat, he gets hungry. When you drop a ball from the top of a parking deck, it falls. Likewise, when you watch your breath, a sign, or sit facing emptiness, the mind will eventually but invariably enter jhana. Jhana is a natural phenomenon. It manifests regardless of whether you practice Theravada, Zen, or nothing at all. The Buddha himself entered the first jhana spontaneously under the rose apple tree. So as long as the conditions for jhana are met, you can't help but arrive there. People who practice Zen practice the jhanas. If you are sitting sincerely, it is impossible to do otherwise.
All that being said, no, Zen doesn't "teach" the jhanas. We would see that as a waste of time if not an utter hindrance to effective mediation. Nothing screws up your sitting more efficaciously than trying to make something happen on the cushion. Jhana (and really all meditation) should unfold like a flower. You wait and let it happen. If you try to speed the process along or, god forbid, try impose your own deluded idea of how and when that flower should open, you are going to kill it. The more ideas and techniques you have bouncing around in your head, the further away you are.
Frankly, I also think the whole notion of stratified jhanas is just another bullshit obstacle. The purpose of sitting is to prepare the mind for insight. I mean, don't get me wrong - the mind is more stable and open to insight in the 4th jhana than it is in the 1st - but you can destroy all sorts of obstacles by just dipping your toe into absorption. It's important not to fetishize mental states. Insight is insight. It doesn't matter if it comes from a mind parked in the 2nd jhana, the base of infinite space, or in the Wendy's drive thru.
And for the love of Pete, don't waste time arguing about what "Zen" is. That's like picking one note or measure out of Beethoven's 5th and calling it the whole damn symphony. Zen is everything and everywhere.
I practiced Zen for over a decade. Only much later did I read the suttas. And after reading the suttas, I belatedly realized that practicing Zen alone without ready access to a teacher is a bit like learning to drive a stick-shift car on the freeway by yourself.
The suttas (Early Buddhist Texts in particular) provide a vast, coherent, inclusive, accessible and gently progressive path of practice that really informs the practice of Zen. For example, I did this for ten years on my zabuton:
MN118:17.2: Just mindful, they breathe in. Mindful, they breathe out. When breathing in heavily they know: ‘I’m breathing in heavily.’ When breathing out heavily they know: ‘I’m breathing out heavily.’ When breathing in lightly they know: ‘I’m breathing in lightly.’ When breathing out lightly they know: ‘I’m breathing out lightly.’ They practice breathing in experiencing the whole body. They practice breathing out experiencing the whole body. They practice breathing in stilling the body’s motion. They practice breathing out stilling the body’s motion. They practice breathing in experiencing rapture. They practice breathing out experiencing rapture. They practice breathing in experiencing bliss. They practice breathing out experiencing bliss.
Everything that I read in the suttas aligns with my experience of Zen. I have found no contradictions. Indeed, one sutta in particular was particularly helpful to me in aligning the EBTs with Zen:
MN44:12.1: “But ma’am, what is immersion? What things are the foundations of immersion? What things are the prerequisites for immersion? What is the development of immersion?”
MN44:12.2: “Unification of the mind is immersion...
The EBT stratification of immersion (i.e., jhana's, form and formless dimensions, etc.) was also very helpful to me as a guide, and it revealed pitfalls to be wary of as well as approaches I had not yet practiced.
My roshi was a 6-hour plane flight away. He was an amazing teacher and I made some progress. For those without ready access to good teachers, there are suttas such as AN8.63 that provide instruction that can be read along with Zen scriptures:
AN8.63:1.2: “Sir, may the Buddha please teach me Dhamma in brief. When I’ve heard it, I’ll live alone, withdrawn, diligent, keen, and resolute.”
D. T. Suzuki wrote
In the view of zen, dhyana does not correspond to the true practice of zen
and
Zen is not a type of dhyana
Dhyana can mean trance states, or it can just mean mental cultivation in general. It is the latter sense, it is argued, that is transliterated as ch'an. Furthermore
Rinzai and Soto... the former most often attacks absorption in trance as mindless quietism... the ghost cave of the spirit... the latter... rejects [its] striving
Traditions of Meditation in Chinese Buddhism, p129
By contrast, I have seen it claimed by a Son monk that there is no access to the beginning of the bodhisattva path without the first dhyana.
