An upper stratospheric layer of enhanced HNO3 following exceptional solar storms -: art. no. L12S01

An analysis of stratospheric nitric acid (HNO3) observed by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) reveals a distinct, high-altitude maximum, that appeared in late November 2003 in the polar upper stratosphere. Confined to the polar vortex, the enhanced HNO3 layer intensified while descending to the middle stratosphere, and disappeared between mid-January and mid-February. The high-altitude maximum is considerably enhanced compared to the weak, secondary maxima previously reported in the literature. Analysis of MIPAS stratospheric nitrogen dioxide (NO2) and correlations with the geomagnetic Ap index suggest that particle precipitation from the intense solar storms of October - November 2003 was responsible for this extraordinary high- altitude HNO3 layer. The detailed morphology and time-evolution of such a distinct, high-altitude HNO3 layer have not been observed before, nor the link to geomagnetic activity through contemporaneous upper stratospheric NO2 measurements.