is this sentence correctly written? Logos, the appeal to logic; persuasion that is backed up with actual observations, data, and facts.

The message is understood but the sentence is not well written. You should write "Logos, that is the appeal of logic, consists of persuation backed up with actual observation, data, and facts". While the word Logos can be paraphrased as 'the appeal of logic', it is necessary to clarify the function of Logos in a text. With that purpose in mind, it is neccesary to separate the ideas of persuation from the paraphrase.