( ( The ( radio ( flux density ) ) ) ( then ( ( follows ( the ( 11 ( year ( sunspot cycle ) ) ) ) ) . ) ) )
(ROOT (S (NP (DT The) (NN radio) (NN flux) (NN density)) (ADVP (RB then)) (VP (VBZ follows) (NP (DT the) (CD 11) (NN year) (NN sunspot) (NN cycle))) (. .)))
The radio flux density then follows the 11 year sunspot cycle.
(ROOT (S (NP (NNS Sunspots)) (VP (VBP occur) (PP (IN in) (NP (DT a) (CD 11) (NN year) (NN cycle)))) (. .)))