Document Type : Research
Institute of Geophysics, University of Tehran
In the study of solar-terrestrial relationships, magnetic storms and solar activity play important roles. In this paper, the intense magnetic storms in company with solar proton events occurred in October and November 2003, January 2005, December 2006, January and March of 2012 have been considered. The variation of the odd nitrogen (NOy) oxides and ozone in the stratospheric layer is investigated by the effects of energetic particle precipitation. Anomaly percentage of the odd nitrogen (NOy) oxides and ozone are calculated separately for the Southern and the Northern hemispheres and geographic latitude from 60 to 80 degrees. The analyzed results of the observational data showed that the intense magnetic storms which consist of more than 500 (particles/cm2 s sr) solar energetic proton (E>10MeV), gave rise to increase the odd nitrogen (NOy) oxides in the stratosphere, from level 1 mb to 200 mb. Also, the results showed that on November 2003, January 2005, December 2006, January and March of 2012 the odd nitrogen (NOy)oxides which consist of more than 500 (particles/cm2 s sr) increased in the Northern hemisphere but for the Southern hemisphere a little decreased. Among the events of the magnetic storms in the autumn and winter seasons, the only event on the October 2003, showed that the odd nitrogen (NOy) oxides increased in the Southern hemisphere. The results showed that the increase in the odd nitrogen (NOy) oxides caused the decrease of ozone in the altitude below the odd nitrogen (NOy) with a delay.
The analyzed results of observation data suggested that the strong magnetic storms consist of a solar proton more than 500 (particles/cm2 s sr) give rise to increasing the odd nitrogen oxides in the stratosphere, from level 1mb to 200 mb. Since the solar zenith angle is dependent on the season, and also, it is very different in the Northern Hemisphere and Southern Hemisphere Polar Regions, the solar zenith angle impacts the background atmosphere. This suggests that the influences of the solar proton event that produced 〖NO〗_y changed ozone somewhat differently in the two hemispheres (Jackman et al. 2014). Because of the difference between the solar zenith angle in fall and winter, we expected a different behavior of 〖NO〗_yin the Northern Hemisphere and Southern Hemispheres. This study consists of three magnetic storm events in winter (January 2005; January 2012; March 2012) and of three magnetic storm events in fall (October 2003, November 2003; December 2006). The main conclusions can be summarized as follows:
1) We observed a large increase in the anomaly percentage of 〖NO〗_y over the Northern Hemisphere, on November 2003, January 2005, December 2006, January 2012 and March 2012; for the Southern Hemisphere, We observed a small decrease in 〖NO〗_y in the same dates except for March 2012.
2) In October 2003 and March 2012 , We observed a large increase in the anomaly percentage of 〖NO〗_y over the Southern Hemisphere and only in October 2003, we observed a decrease in the anomaly percentage of 〖NO〗_yover the Northern Hemisphere.
3) Increase in 〖NO〗_y always cause a decrease in the stratospheric ozone (of short duration and with a delay of several days) at the level lower than the level of increase in〖 NO〗_y.
4) The variation of the anomaly percentage of the stratospheric ozone directly related to the variation of 〖NO〗_y, but the decrease in ozone cannot be considered as the exact model of increase in〖 NO〗_y.
5) Proton flux and increase in influence energetic particles (when geomagnetic storms occurred) in the upper and the middle atmosphere cause of the increase in ionization.
6) There is a delay (from few hours to several days) between starting time of geomagnetic storm event and the time of the maximize proton flux, time of the increase in 〖NO〗_y and time of the decrease in ozone.