Phi spark

A phi spark is a commonly seen (for example, during the evolution of a Herschel) large symmetric spark that dies in 9 generations. It gains its name from resemblance of its generation 2 to a Greek capital letter phi (Φ).

The pentadecathlon splits during its cycle into two phi sparks for the span of five generations; their central halves regenerate the oscillator, while the outer halves die as usual.

.OOO.
O...O
O...O
.OOO.

A phi spark.

..O..
.OOO.
O.O.O
O.O.O
.OOO.
..O..

Generation 2 reveals the origin of the name.

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.OOO.
OOOOO

A triangle is a common parent of phi.

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.O.O
O..O
.OO.

A 7-cell pattern arising from a Herschel, which becomes a phi spark in 8 generations (a triangle in 7).