2009年1月强爆发性增温期间突发E(Es)层的响应

Response of the sporadic-E layer to the stratospheric sudden warming in January 2009

平流层爆发性增温(SSW)期间,低层大气温度场和风场等的剧烈变化会直接影响潮汐和风剪切作用.此举可能会导致电离层Es的相应变化.本文以2009年1月事件为例,分析了SSW期间Es层的响应.首先,在排除太阳活动和地磁活动对Es层影响的前提下,分析了昆明站附近MLT区域行星波和潮汐波的波动特性,发现此期间存在显著的2日行星波,并伴有日潮汐减弱和半日潮汐增强等波动现象;随后,分析相应时间段内Es层的变化特性发现,重庆和昆明站附近Es层强度明显减弱,且其高度显著抬升.这一现象与低层大气的波动变化具有同步性.最后,通过模拟经典风剪切理论下Es层金属离子的汇聚过程和运动轨迹,再现了SSW期间Es层与低层大气波动的耦合演化过程.该分析结果为研究低层-中层-高层大气的耦合过程提供了一种新的思路.

During a stratospheric sudden warming（SSW）,lower atmosphere temperature and wind fields change strongly,which can pose direct influence on tides and vertical wind shears in the mesosphere and lower thermosphere（MLT）.It can cause corresponding variation in the sporadic-E layer（Es）.This paper analyzes the response of the Es to SSW by an example in Jan2009.The method of wavelet analysis was used to analyze the 2-day planetary waves in the MLT region over the Kunming station from Nov 2008 to Mar 2009.Meanwhile,we utilized the harmonic fitting to find the variations of diurnal tide,semidiurnal tide and terdiurnal tide produced by SSW.Finally,we modeled the movement process of the Es layer from the height of200 km to lower altitude under the diurnal tide wind and semidiurnal tide wind based on the theory of wind shear.Firstly,excluding the influence of solar and geomagnetic activities on the Es-layer,we used wind waves and tides activities in the MLT region and found that there were obvious 2-day planetary waves,diurnal tide has been weaker and semidiurnal tide has been stronger during this SSW.Then,we investigated the changes of the Es-layer over the Chongqing and Kunming stations,showed that the intensity of Es-layer was weakened and the height was increased,whichhappened at the same time with the disturbances in the lower atmosphere.Finally,through simulating the convergences and paths of metal ions of the Es layer,we reconstructed the coupling process of the Es layer and lower atmosphere in this SSW period.During the SSW,because of the variations of the wind field in the MLT region and Es-layer,diurnal tide has been weaker and semidiurnal tide has been stronger,while the height of the Eslayer increased and the critical frequency for Es decreased.The results of simulation are consistent with the observation.It can be inferred that the Es-layer may be a coupling approach between the lower atmosphere and the upper atmosphere.