电离层热层对太阳辐射变化响应的特征时间

The characteristic time of ionospheric and thermospheric response to solar activity has been one of the fundamental scientific questions in the ionosphere physics since 1960's. CHAMP and GRACE satellites provided simultaneous thermosphere density and ionospheric observations enabling a novel study of characteristic time of ionospheric and thermospheric response to solar activity at the period of 27 days. Thermosphere density data obtained from the CHAMP and GRACE accelerometers,and in-situ electron density from CHAMP planar Langmuir probe and GRACE K-band ranging system, total electron content (TEC) above the CHAMP and GRACE satellites along with TIMED SEE and SDO solar flux data, will be used in this project. These data sources with high time resolution are very important to accurately derive the time delay of ionospheric and thermospheric response to solar activity. The similarities and differences of the response time between ionosphere/thermosphere and solar activity, providing important insight to the physical connections of this solar-terrestrial problem, will be investigated. Additionally, the latitudinal, solar activity and geomagnetic activity dependencies of this characteristic time will be isolated. Observations will be combined with a three dimensional self-consistent coupled thermosphere-ionosphere general circulation model (the National Center for Atmospheric Research - Thermosphere/Ionosphere Electrodynamics General Circulation Model, NCAR-TIEGCM) to understand the fundamental physical and photo-chemical processes in determining the time delay between ionosphere/ thermosphere and solar activity. The response of the photodissociation of molecular oxygen, and NO density (or cooling rate) to the 27-day solar activity will be studied in this project as well, which is crucial to explore the physical mechanisms of the response time of ionosphere and thermosphere to the 27-day solar activity.

电离层与热层对太阳辐射变化响应的特征时间是电离层研究中尚待解决的重要科学问题之一。本项目拟充分利用CHAMP 与GRACE 卫星反演的热层大气密度、卫星高度处的电子浓度、卫星高度以上的总电子含量(TEC)等高时空分辨且协同观测的电离层热层资料，结合高分辨的TIMED SEE、SDO卫星太阳辐射数据，将首次系统研究电离层与热层对太阳辐射27天周期性变化的响应时间，并涵盖该响应时间随纬度、太阳活动和地磁活动的依赖性。 同时，利用全球电离层热层自洽耦合模式TIEGCM，通过观测与模拟结果比较，理论分析电离层热层对太阳辐射响应时间的异同，探讨电离层热层对太阳辐射响应时间受低热层氧分子光解以及NO光化学等过程的影响，以揭示电离层热层对太阳辐射响应时间的物理机理。该项目不但将推动电离层热层光化学以及电离层-热层相互耦合方面的机理研究，而且为空间天气预报提供理论指导。

电离层与热层对太阳辐射变化响应的特征时间是电离层研究中尚待解决的重要科学问题之一。我们基于CHAMP、GRACE等低轨道卫星的观测反演大量电离层电子浓度与热层大气密度数据。利用我们反演的电离层与热层大气数据研究分析电离层热层大气对包括磁暴在内的太阳活动响应。我们侧重研究电离层在磁暴主相期间白天电离层对磁暴响应的经度依赖，并发现不同磁暴期间电离层响应存在明显经度变化，而引起该变化的主要原因是穿透电场的变化。首次观测得到在磁暴主相结束后，顶部电离层TEC在大部分经度都出现持续时间超过3天的负相响应，等离子体沿着磁力线的输运作用和中高纬度长时间低中性氧/氮气浓度比水平或是主要原因。.我们重点探讨了电离层热层对太阳活动的响应特征时间问题。利用2004-2009年期间CHAMP卫星电离层电子浓度观测和TIMED SEE太阳辐射观测研究电离层电子密度对太阳辐射27天变化的响应。我们发现电离层电子浓度和太阳辐射强度变化呈现较好的相关性。电离层电子密度对太阳活动的延迟时间在1天以内，并且呈现了南北半球的非对称性特点。同时，我们认为当电离层电子浓度和太阳辐射强度变化二者相关较弱时，较强地磁活动的干扰有关使得太阳的EUV辐射的影响无法占主导地位。通过电离层热层耦合模式模拟研究了电离层电子浓度对27天太阳辐射变化的响应。我们发现，在剔除了地磁活动影响之后，两者相关性较好，且时间延迟约为十几个小时，远远短于之前报道的多天的响应时间延迟。.依托该项目支持，我们在电离层热层大气对包括磁暴在内的太阳活动的响应方面的研究取得系列创新性成果，发表以项目负责人第一或通讯SCI论文共21篇。