Dynamic Array Names?

I am a bit new to actionscript so bear with me. I have a function that is called from a timer event. Every time the event is called I need to create a new Array with a unique name:

var dropNumber:int = dropHead.length - 1;
var ["dropTail" + dropNumber???]:Array = new Array();

I am not sure how to dynamically change the name of an array with as3, Please help.

Also, just a bonus question, is it more efficient to have a single array broken into partitioned indexes or have several arrays of data?