Rapid‐run ionosonde observations of traveling ionospheric disturbances in the auroral ionosphere
Rapid‐run ionosonde observations of traveling ionospheric disturbances in the auroral ionosphere
复制标题
极光电离层中行进电离层扰动的快速电离探空仪观测
DOI：
--
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
T. Ulich
中科院分区：
文献类型：
--
作者：
A. Kozlovsky;T. Turunen;T. Ulich
自2007年以来，索丹屈莱地球物理观测台每分钟例行进行一次垂直电离层探测，使用频率调制的连续波啁啾，频率为500 kHz/s，从500 kHz到16 MHz。我们使用这些数据来研究旅行电离层扰动（TID）在10-16当地时间。这些观测是在2007年4月至2012年6月期间进行的，主要是在太阳活动较低的时候。在对应于以下的五个周期带中研究TID：次声（声）波和浮力截止（周期从5到10分钟）;小尺度重力波（GW; 10-15分钟）;中等尺度（MS; 15-30分钟）GW;中等-大尺度（MS-LS; 30-60分钟）GW;和大尺度（LS; 60-120分钟）GW。短期（5-15分钟）和MS（15-30分钟）TID的相对贡献（相对于LS TID）在冬季最小，在夏季最大。这些年变化与真高度的变化密切相关，即最大的相对振幅出现在夏季，此时在最小高度处观测到TID。我们认为，夏季短周期TID的增加是由于反射降低到Brunt-Väisälä周期较小的高度，因此存在短周期重力波。在太阳活动最小的3年（2008-2010年）中，夏季最大值最为突出。在2011年，当太阳活动增加时，年度变化似乎不那么突出。较长周期（30-120分钟）TID的年度变化基本上不太显著。对于所有的TID，没有发现明显的依赖性的AE和Ap指数的磁活动。
Since 2007, the Sodankylä Geophysical Observatory routinely performs vertical ionosphere soundings once per minute, using a frequency‐modulated continuous‐wave chirp at the rate of 500 kHz/s from 500 kHz to 16 MHz. We used these data to study traveling ionospheric disturbances (TIDs) during 10–16 local time. The observations were made between April 2007 and June 2012, mostly during low solar activity. The TIDs were studied in five bands of periods corresponding to the following: infrasonic (acoustic) waves and the buoyancy cutoff (periods from 5 to 10 min); small‐scale gravity waves (GWs; 10–15 min); medium‐scale (MS; 15–30 min) GWs; medium‐large scale (MS‐LS; 30–60 min) GWs; and large‐scale (LS; 60–120 min) GWs. Relative contribution (with respect to LS TIDs) of the short‐period (5–15 min) and MS (15–30 min) TIDs shows minima in winter and maxima in summer. These annual variations anticorrelate with variations of true height, namely, the largest relative amplitudes occur in summer, when TIDs were observed at minimal heights. We suggest that the summer increase of shorter‐period TIDs is due to lowering reflection to the height where the Brunt‐Väisälä period is smaller and, hence, shorter‐period gravity waves exist. The summer maxima were most prominent during the 3 years of minimal solar activity (2008–2010). In 2011, when solar activity increased, the annual variation seems less prominent. Annual variations of the longer‐period (30–120 min) TIDs are essentially less significant. For all TIDs, no obvious dependences on the AE and Ap indices of magnetic activity were found.