Stratospheric Impacts of the Autumn 2003 Solar Storms

We investigate the effects of the Autumn 2003 solar storms upon the stratospheric composition, using satellite observations from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument aboard ENVISAT. An analysis of stratospheric nitric acid (HNO3) in particular, 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 slowly descending to the middle stratosphere, over the following months. 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.