句子：I am thinking back now to when I first started listening to rockroll and I remember my father saying it was a bad influence on us.
请问老师：back now to是短语介词back to中插入了now，还是副词back修饰thinking，now时间状语，to when...作状语呢？back to、up to与down to类似的短语，其中back， up， down的词性能否剖析呢？他们是修饰to...还是修饰前面的动词或非谓语动词呢？
back to, up to, down to等，其中back, up, down均为副词表示方向，介词to表示目的或目的地，为地址状语。一个动词可以既带有方向状语，同时还带有地址状语。now为时间状语。
He now came down to the ground.
He came down now to the ground.
他这个时候下到地面。