Effect of subauroral polarization streams on the thermosphere: A statistical study
Effect of subauroral polarization streams on the thermosphere: A statistical study
复制标题
DOI：
10.1029/2010ja016236
复制
发表时间：
2011-03
影响因子：
--
通讯作者：
Hui Wang;H. Lühr;K. Häusler;P. Ritter
中科院分区：
文献类型：
--
作者：
Hui Wang;H. Lühr;K. Häusler;P. Ritter
利用2年的CHAMP和DMSP协调观测，我们首次分别研究了两个半球在黄昏和午夜前的极光亚区，极光亚极化流（SAPS）、电离层霍尔电流（电喷流）、上层热层纬向风和质量密度之间的关系。为了比较，我们还分析了在非saps期间相同的参数作为磁纬度（30度-80度磁纬度）的函数。在非SAPS期间，中性风表现出与SAPS期间相似的特征，在黄昏到午夜前的区域，与等离子体漂移的方向相同，向西流动。无论SAPS是否发生，中性和等离子体速度都在同一纬度达到峰值。地磁活动越活跃，速度越快，峰值向赤道方向移动。在非saps期间，无论地磁活动如何，两个半球的等离子体风速和中性风速之比平均为2.75 +/- 0.4。当Kp = 4时，在北半球和南半球，与非SAPS时间相比，SAPS事件期间的中性风分别增强了1.5/1.2倍。SAPS期与中性风的速度差也比非SAPS期大，且随地磁活动的增加而增大。在SAPS事件中，东向极光电喷射的峰值纬度出现在等离子体漂移的极地方向1.5度，证实了SAPS在高电导率通道的赤道方向形成。这些由sap引起的强风可以加热上层热层。结果，我们观察到在400公里高度的质量密度比没有SAPS的时期增加了10%。此外，密度异常峰与SAPS同时出现，取代了电喷峰。我们认为这是离子中性摩擦有效加热热层的指示。
Using 2 years of coordinated CHAMP and DMSP observations we have investigated for the first time the relationship between subauroral polarization streams (SAPS), ionospheric Hall current (electrojet), upper thermospheric zonal wind, and mass density at subauroral regions in the dusk and premidnight sectors, separately for both hemispheres. For comparison, we have also analyzed the same parameters as a function of magnetic latitude (30 degrees-80 degrees magnetic latitude) during non-SAPS periods. During periods of non-SAPS, the neutral wind exhibits similar features as during SAPS events in the dusk to premidnight sector, streaming westward in the same direction as the plasma drift. Both neutral and plasma velocities peak at the same latitude regardless of SAPS occurrence. For higher geomagnetic activity both velocities are faster and the peaks shift equatorward. During non-SAPS periods, the ratio between plasma and neutral wind velocity is on average 2.75 +/- 0.4 in both hemispheres irrespective of geomagnetic activity. The neutral wind during SAPS events gets enhanced by a factor of 1.5/1.2 for Kp = 4 in the Northern/Southern Hemisphere, respectively, as compared to non-SAPS time. The velocity difference between SAPS and neutral wind is also larger during SAPS period than during non-SAPS period, and the difference tends to increase with increasing geomagnetic activity. The peak latitude of the eastward auroral electrojet appears 1.5 degrees poleward of the plasma drift during SAPS events, confirming the formation of SAPS equatorward of the high-conductivity channel. These SAPS-induced large winds can heat the upper thermosphere. As a result we observe a 10% enhanced mass density at 400 km altitude with respect to periods without SAPS. In addition a density anomaly peak occurs collocated with the SAPS, displaced from the electrojet peak. We regard this as an indication for efficient thermospheric heating by ion neutral friction.