Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Color
SUNBURSTSHADER_COLOR
Parameter: R Frequency
SUNBURSTSHADER_SCALE_R
Parameter: A Frequency
SUNBURSTSHADER_SCALE_A
Parameter: T Frequency
SUNBURSTSHADER_FREQUENCY
Parameter: Turbulence
SUNBURSTSHADER_TURBULENCE
Parameter: Radius
SUNBURSTSHADER_RADIUS
Parameter: Height
SUNBURSTSHADER_HEIGHT