For the past month or so, I have been working on longer sits and establishment of metta alongside concentration on my meditation object. At the moment I am doing fire kasina using a book light, and a mantra which tends to bring up Piti.

On a couple of occasions lately, I have gotten into a state which persists something like 15-60 minutes. I am curious if others have dealt with similar states and may share their reflections on it. Based on some material I have read, I am guessing that I may be scratching at the door of 3rd Jhana but am unsure. The significance of classifying or putting the experience on a map for me is mostly to get a sense of how to deal with the state skillfully. I do find maps have been beneficial for me overall; though I also see the downsides of worrying too much about these things.

The state and its entry point feels as follows:
- The entry point has been spending something like 45 minutes in sitting meditation, with emphasis on keeping Piti and Sukha sustained alonged with attention to the kasina as much as I can manage.
- Often there is a period where I deal with some pretty extreme somnolence, but I find I can counter balance that by blasting my nervous system with some internal energy periodically.
- Awareness eventually changes its quality to the point where the spotlight of attention is de-emphasized
- After I am done the sit, my awareness feels somewhat more expansive, although not to a profound degree
- I have twice now noticed, after roughly 55 minutes sits on my lunch break (I work from home as a programmer), re-orienting the mind to work takes about 15 minutes. Initially, I stare at the screen and notice that while I feel great (calm, pretty much free from any hindrances), my mind does not respond much to intentions to focus on formulating, let alone solving a problem. 
- Similar to those two experiences, I did a 90 minute sit on a day off, and freaked my partner out a bit with how I was acting afterwards. More accurate to say I was unreacting. She said my voice changed, and I seemed serious (her words, I personally felt the situation was that I was not capable of taking anything seriously, though I did not feel any negative emotions). From my vantage point, I could hear here speak to me, but there was again this unreactive and disinterested nature about my mind to the content. By analogy, it was reminded me of how Dr. Manhattan acted like from The Watchmen movie (minus any super powers of course). This time, the state lasted for more like an hour or so.

Happy to hear any perspectives and suggestions; both in terms of where to go next and how to skillfully deal with it in contexts where interacting with things and people is important. Also, worth mentioning that my partner and I have talked about that and she understands that it is just a temporary state. 

Neat.

Is the state you are asking about the one that happens on the cushion or the one that happens after? When you mention 3rd Jhana, are you talking about the highest level of samadhi during the sit, or are you asking about whether what happens after the sit is related to 3rd Jhana?

Interesting question; it isn't clear to me whether it is a different state or just that I am doing different things (i.e. washing dishes instead of staring at a book light). My working model is that the mental context (level of samadhi, emotions, etc.) generated during the sit persists after the sit for a period of time. I'm curious if you have a different model or understanding. 
As mentioned, I wrote the OP without thinking of these as different states. I suppose that I am moreso asking if the state after sitting may be an indication of a particular Jhana; or if others have experienced something similar. What is tempting me to try to use it as a signpost is that it feels profoundly different to me than what I would describe as just Piti and Sukha. 

Dammarato is a teacher who thinks of the jhanas as something that happens at the same time as day-to-day activities. Most other teachers think of the jhanas as a pretty well exclusively on-cushion thing. Often the jhanas are taught as arising after a great deal of stilling of the mind and sort of unifying it so that the mind is exclusively aware of the state. A complicated activity like washing the dishes, which involves planning, perception, judgment, and a lot of physical movement would not be possible in intense jhana states. Toward the deeper end of the jhanic space, the experience is so overwhelming that it is not even possible to think.

But wherever a person is in this rage of possible intensities, concentration can produce lasting perceptual/processing changes that continue, or sometimes arrive for the first time, after the sit. It sounds like you are experiencing equanimity and a reduced sense of agency. It can be very powerfully helpful to experience this kind of a shift, especially if it happens more than once. It is a demonstration of the malleability of the mind. When the mind sees that it can operate in new modes, quite a lot can open up. 

My focus here would be on the experience after the sit. It's worth really exploring. I'm not sure that tying it to a specific jhana number would give you any more information than the state itself, without any particular labels. 

Thank you for sharing your perspective.

I learned a new word today, somnolence, so thank you for that!

So I think in terms of Jhanas the third one is the trickiest one to suss out as a "distinct" state, mostly because in my experience it tends to be more of a transition from feeling lots of sukha to deep equanimity (spaciousness, wide attention, pain becomes less bothersome, carefreeness, etc). It does sound like from the after effects you are starting to get into more into the realm equanimity (I've noticed that usually the 4th jhana has a bit of a carefree clean afterglow feeling and increased visual acuity).

The trick that really helped me go deeper into the jhanas, courtesy of TWIM and Delson Armstrong, was to relax more, let attention go broad (they do jhanas by radiating metta out to the 6 directions, which lets the metta expand beyond your body), and to just sit there. Then the piti and sukha will naturally run its course, and you will be left in the 4th jhana. Hope that helps!

A nice way to look at 2nd/3rd distinction is this: In second, the description, "like a lake with spring-water welling up from within" applies. There is a welling up of sukha. This is a change, and adding to, a gain. In third, the description "immersed in the water and grow without standing up out of the water, so that they are permeated and pervaded, suffused and filled with cool water from their roots to their tips" applies. There is no more welling up. No more adding, no more gain. No movement of the mind or in the mind, just the pervasive awareness of sukha. 

Hey, thanks for sharing. I actually just started practicing some TWIN/Delson stuff last week. I was wondering if you could share your perspective on something specific to this practice.

With regard to the practice they outline in TWIM, they talk about using metta itself as a meditation object after metta is established via the usual techniques (well-wishing statements, visualizations, etc.). Cool; I think I can do that first part perfectly fine since about 5 years ago. Those techniques absolutely get me going on an overall feeling of well-being and well-wishing.

Where I am stuck at the moment, is transition to using metta as a meditation object after establishing it (i.e. dropping the statements/visualizations). Delson described it in various ways (feelings of warmth, glowing, tingling in the heart area), but it is not obvious to me whether then bodily sensations I feel are Piti, Metta, or both at the same time. So my question is, assuming what I said tracks with your experience/understanding, does metta present itself as a discrete sensation apart from Piti to you? If yes, can you describe it (I know we are not likely to have the same experience necessarily but I'm still curious)? If no, do you basically just take whatever bodily good feeling you can sustain in that area, and use that as an object for meditation?

So in my experience they are distinct. Metta does feel basically how Delson describe, and piti for me has always had this electricity/tingling feeling to it (similar to the pins and needle effect when a numb part of your body comes back online), and it generally starts in my hands or spine (but I've heard people feel piti in different ways).

Two things you might want to consider. If you have access to the waking up app, I think Sam Harris does a great job with his guided meditations on metta (like they are the best ive seen). Second, you can also just try to tune directly into feelings of warmth and fuzziness and that works for me (although after a good amount of experience with metta so ymmv).

Thanks for sharing. I've been experimenting with this on the cushion and I think I have managed to tune into the feeling. In retrospect I'm not surprised that I was not sure if it was thermogenesis or metta. For me, the quality of the feeling is nearly (but still not) identical to just feeling warmth. Once I was able to get it going at a whole body level and a bit beyond that space, it became more distinct.