A Paiute-Tomahawk sounding rocket containing a 1.5- to 5.3-&mgr;m cryogenically cooled spectrometer was flown into a very bright (IBC III+) auroral breakup from Poker Flat, Alaska. The main emission features at 2.8, 4.3, and 5.3 &mgr;m were all found to be enhanced owing to the large energy input to the atmosphere associated with the aurora. The most prominent enhancement occurred in the 4.3-&mgr;m feature which is identified as emission from the CO2 (&ngr;3) band. The maximum of the peak spectral radiance of this feature was observed at a rocket altitude of 92 km and had a value of about 130 MR/&mgr;m, which is nearly 2 orders of magnitude greater than that for an undisturbed atmosphere. By comparing upleg and downleg data, it was ascertained that the time constant for this excitation/radiation process is longer than 5 min. It is concluded that the excitation process involves vibrational excitation of nitrogen followed by collisional radiance &ngr;-&ngr; transfer to CO2, which then radiates at 4.3 &mgr;m. The 5.3- and 2.8-&mgr;m features are attributed to radiation from fundamental and first-overtone NO bands.