Probably not. While the Annals of St. Bertin (in some manuscripts) do name the leader of the 845 siege as Reginherus, which is often taken to be a latinization of Ragnarr, no byname is given and, other than a historicizing instinct among old saga scholarship (i.e. a desire for saga figures to be based on real people), there's no particular reason to link him to Ragnarr loðbrók.
The legendary Ragnarr, in my opinion, is a near-total fabrication, as I elaborate on here.
Two answers on Ragnar Lodbrok's historicity in general (there's no evidence that ties the later legend to any particular historical figure) by /u/y_sengaku and /u/sagathain
Both suggest that the person who sieged Paris in 845 doesn't match up with the details of the Ragnar Lodbrok legend. I'm sure more can be said on the topic, just the answers might give you some more context/information!