Ways pīti (rapture) in first and second jhāna are the same and different

 

Ways in which pīti in first and second jhāna, and pīti sambojjhanga are the same

They're both nirā-misa (spiritual), as opposed to sa-misā (worldly) pīti which are based on 5 cords of sensual pleasure.

MN 99 uses the simile of fire that depends on wood to burn, and the jhānic pīti is the superior fire because it doesn't depend on a fuel source, whereas worldly pīti depends on 5 cords of sensual pleasure as the fuel for the fire. 

Ways in which pīti in first and second jhāna are different

first jhāna pīti is born from viveka (judicious-seclusion). That is, 

* the rapture that arises from knowing how to use right view to judiciously separate one self from lust, passion, greed, and unskillful Dharmas. In general, enjoyment of anything in accordance to Dharma. 

* also the rapture of enjoying the direct experience of being judiciously secluded from lust, passion, greed, and unskillful Dharmas. 

second jhāna pīti is born from samādhi. That is, when verbal thinking from first jhāna has been sublimated into subverbal mental processing with singular focus (ekodi-bhava) in second jhāna, there is an exponentially stronger increase in jhānic force circulating internal energy in the body, causing a proportional increase in physical pleasure (sukha). 

The tendency is to respond to this great change in force of sukha (from first to second jhāna), with a mental excitement (pīti). 

Whereas in first jhāna, jhānic force had been somewhat muted and dispersed by vitakka and vicāra (directed thought and evaluation).

* rapture from the direct experience of the increase in sukha and jhānic force

* rapture from Dharmic subverbal knowledge, such as the knowledge one has gained the skill of thinking what one wants to think, not thinking what one doesn't want to think (MN 20), which is not shared by first jhāna pīti.