move the text after the cursor to a new line

If the cursor is on a <space> as in ([] marks the cursor):

lorem ipsum[ ]dolor sit amet

the simplest is to do r<CR>, that is "replace the current character with a linebreak".

Otherwise, use @knittl's solution.

As I answered in this post, How do I insert a linebreak where the cursor is without entering into insert mode in Vim?.

Please try Control + j.

So you want to move everything in the current line, which comes after the cursor to the next line? Read: insert a line break??

(move cursor)
i (or a)
<return>
<esc> (or ^C)

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To map this sequence of keystrokes to a single key, follow @thb's suggestion and use the :map command:

:map <F2> i<CR><ESC>

:map <F2> i<CR>

This keeps vi in insert mode.