Stratospheric studies consider crucial question of particle precipitation

Recent work calls into question the adequacy of using atmospheric models with an upper boundary near 60 km for interpretive and prognostic studies of stratospheric odd nitrogen (NOY = NO + NO2 + 2 × N2O5 + HNO3 + CINO3 + NO3) and ozone (O3). Studies have shown that the effects of energetic particle precipitation occurring within the mesosphere and the lower thermosphere (MLT, roughly 60–110 km) ultimately affect stratospheric NOY and, calculations suggest, O3. The magnitude of these effects— which are solar cycle-dependent—on the stratosphere is calculated to be comparable with those due to solar flux variations associated with the 11-year solar activity cycle. Accounting for the effects of these precipitating particles requires models with an upper boundary no lower than 100 km. Also, the polar night observations of the species required to unambiguously characterize this solar and particle-driven coupling between atmospheric regions have not been made and are not yet planned.