The response of the lower stratosphere to strong isolated geomagnetic storms

The fact that circulation in the winter northern lower stratosphere is affected by geomagnetic activity on the time scale of months was reported recently. The aim of this paper is to examine the possibility of short-term geomagnetic disturbances to invoke the detectable effect. In our analysis we study the effect of strong isolated geomagnetic storms (Ap≥60) on the distribution of stratospheric pressure and temperature fields in the Northern Hemisphere winter (December-March) in 1952-2003. Geomagnetic storms in months affected by stratospheric warming events are excluded. Finally, total of 38 isolated storms were left for the analysis. The state of the stratosphere is described by pressure and temperature anomalies at 20, 50 and 100 hPa. Superposed epoch analysis and composite maps are used. Data are taken from the NCEP/NCAR reanalysis. We found that after the storm onset the decrease of pressure and temperature occurred in the high-latitude lower stratosphere. This is with agreement of recently presented physical mechanism. The minimum value of pressure and temperature is reached between 5th-7th day after the onset of the storm.