Observability of NEIALs with the Sondrestrom and Poker Flat incoherent scatter radars

► Aurorae with similar morphology are observed at both Sondrestrom and PFISR. ► NEIALs were not observed with Sondrestrom when active auroral structures were present during several different events. ► Sondrestrom is well suited to make ISR measurements inside active aurora. ► The limiting scale size of enhanced ion acoustic waves is between 10 and 15 cm.