difference between "Ja mata" and "mata ne"

Question

Answer

Ja(jaa) means like "then". "Mata" means see you. So it could be "see you then" or "then, see you!"
"Ne" is used to make a sentence sounds softer. 
eg: きょう は てんき が いいです。
     きょう は てんき が いいですね。

You can say only "mata!" as well but adding "ne" sounds like more friendly.

Answer

They mean the same. We use them colloquially.

We also say: 
Jaa mata, Ja matane, Jaa matane, Jaane, Dewa mata...etc. 
They mean the same like "see you" or "bye". 
("Dewa" sounds more formal than "ja" or "jaa".)

I hope this helped you.

Answer

jaa matane = then see you or then bye
matane= see you next time, ok ? /see you ok?..