How sound are the narrations which state that Satan descends upon the one who remembers God while asleep?

If you mean that Satan comes to a servant when he sleeps to distract him from the remembrance of Allah, then there is a hadith that indicates this: "When one of you goes to his bed, a malak (angel) and a shaytan (devil) hasten to him. The devil says: 'End with evil,' and the angel says: 'End with good.' If he remembers Allah, the devil departs, and the angel comes and protects him." This hadith was narrated by Al-Hakim and graded as hasan (good) by Al-Hafiz Ibn Hajar, but Al-Albani deemed it weak due to the 'an'anah (narration using "on the authority of") of Abu Al-Zubayr in its chain.