Hello to you all
Actually there are many evidence that support partial khazar ancestry of Ashkenazi. The historian Douglas Dunlop gives some of them in his book "The history of the Jewish Khazars".
As for Ashkenazi jews being connected to Arabs there is no way. Ashkenazis lived in europe and Arab jews lived first in Yemen and Hijaz, part of them became muslims and part remained Jewish, part immigrated and part stayed.
While only a minority of Ashkenazi are semitic, the majority of Sphardic are. Part are genuine Arabs who converted after the second temple distruction and almost all Yemenites are and the rest are an amalagmation of different semitic peoples who converted to Judaism one way or another.
The question here should be are all Jews Israelites? the answer is a definite no. Many of the Sphardic Jews are semitic yes but this proves nothing since they could be either Aramaic, Phoenician, Kanaanites, Assyrians or Arabs who are all semitic as well. Ashkenazi on the other hand as I said in earlier posts are mostly germanic, slavs, Turkic and a minority of semitic peoples.
Finally about the ethiopian jews, they probably came with the Ethiopians after they were kicked out from Arabia by the Sassanids. I don't know about genetics but I think that a study proved they were ethnic African.
AL-Jassas