It is likely that you’re using a pager such as less or most since the output of ps aux is longer than a screenful. If so, the following options will cause (or force) long lines to wrap instead of being truncated.
If you use either of the following commands, lines won’t be wrapped but you can use your arrow keys or other movement keys to scroll left and right.
ps aux | less -S # use arrow keys, or Esc-( and Esc-), or Alt-( and Alt-)
ps aux | most # use arrow keys, or < and > (Tab can also be used to scroll right)
Lines are always wrapped for more and pg.
When ps aux is used in a pipe, the w option is unnecessary since ps only uses screen width when output is to the terminal.