Statistical Analysis on the Relationship between Solar and Geomagnetic Activities and the Arctic Oscillation

Abstract

The purpose of this study is to analyze the possible impact of solar activity and geomagnetic activity upon the Arctic Oscillation (AO) as an external forcing to the atmosphere. Maximum and minimum periods are defined for the solar flux density at 10.7 cm wavelength (F10.7) and the amplitude antipodal index (aa index). In each period, the monthly mean of barotropic height anomaly, zonal-mean wind anomaly, and zonal-mean temperature anomaly are calculated, and the difference between the maximum and minimum period is analyzed. As a result, the structure of the AO is found in winter when the composite of anomaly is analyzed for each month. Significance test shows that the aa index has wider significant area than that of F10.7. According to the result for the zonal-mean temperature anomaly, a heating area is found in the lower stratosphere for both indices. But in the case of the aa index, the characteristic heating or cooling areas are stronger during the maximum period than that for the minimum period in the vicinity of 1 hPa. There is a possibility that the upper atmospheric differences in temperature can be a trigger of the excitation of the AO in the lower atmosphere.