You’ll notice in Col. Pratt’s report that he uses “Army N. E. Va” in the closing. As I’ve discussed here and here, I’ve never been able to find any documentation creating or formally recognizing an Army of Northeastern Virginia. Pratt’s report is one of only three references to such an organization in the Official Records. The other two are Porter’s endorsement (dated August 19, 1861) of Burnside’s report, and Robert E. Lee’s reference to his own army in a September 3, 1862 letter to Jefferson Davis (OR, Series I, Volume XII/2, p 559). Pratt’s report is exceptional in that it contains the first reference to the army that is contemporary to the battle, as the report is dated July 22. Pratt was a judge before and after the war, so maybe he was predisposed to timely record keeping. Or maybe he pre-dated the report. I honestly don’t know.
I don’t want to belabor this point. McDowell was in command of the Department of Northeastern Virginia, and the federal troops within that department. But every reference I’ve found to the Army of Northeastern Virginia, with the exception of Pratt’s report, was written after McDowell’s army was broken up. I can’t find any mention of the Army of Northeastern Virginia in the New York Times for 1861.