Can you learn jazz by ear?
Jazz is first and foremost an aurally learned music.
Learning music by ear is not always the easy way, and if you aren't used to it, you may find it quite difficult at first. But it's the best way hands down, and the more you do it, the easier it gets.
Can you learn jazz by yourself?
Luckily, there are a number of things you can work on that will help you develop as a jazz musician. Most of these can be done on your own, wherever you are based. If you follow these steps and develop a dedicated and focused practice routine, you should find that you start to make real progress.