Javana: fr. javati to impel: 'impulsion', is the phase of full cognition in the cognitive series, or perceptual process citta-vīthi see. viññāna-kicca occurring at its climax, if the respective object is large or distinct. It is at this phase that kamma is produced, i.e. advantageous or disadvantageous intention concerning the perception that was the object of the previous stages of the respective process of consciousness. There are normally 7 impulse moments. In mundane consciousness lokiya, any of the 17 kammically advantageous classes of consciousness Tab. I, 1-17 or of the 12 disadvantageous ones Tab. I, 22-23 may arise at the phase of impulsion. For the Arahat, however, impulsion has no longer a kammic, i.e. rebirth-producing character, but is a kammically independent function kiriya Tab. I, 72-89. There are further 8 supra-mundane classes of impulsion Tab. I, 18-21, 66-69.
The 4 impulse moments immediately before entering an absorption jhāna or one of the supra-mundane paths magga see. ariya-puggala are: the preparatory parikamma approach upacāra adaptation anuloma and change-of-lineage-moment gotrabhū In connection with entering the earth-kasina absorption see: kasina they are explained as follows, in Vis.M IV:;After the breaking off of the subconscious stream of being bhavanga-sota, there arises the 'directing at the mind-door' manodvārāvajjana see: viññānakicca, taking as object the earthkasina whilst thinking, 'Earth! Earth!' Thereupon, 4 or 5 impulse moments flash forth, amongst which the last one change-of-lineage-moment belongs to the fine-material sphere rūpāvacara whereas the rest belong to the sense-sphere kāmāvacara, see: avacara though the last one is more powerful in thought conception, discursive thinking, interest rapture, joy and concentration cf. jhāna than the states of consciousness belonging to the sense-sphere. They are called 'preparatory' parikamma-samādhi as they are preparing for the attainment-concentration appanā-samādhi; access upacāra-samādhi as they are close to the attainment-concentration and are moving in its neighbourhood; adaptive anuloma as they adapt themselves to the preceding preparatory states and to the succeeding attainment concentration. The last one of the four is called 'matured' gotrabhū. In a similar way, the impulse moments before reaching the divine ear are described in Vis.M XIII, 1.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.