亚大地区F2电离层预测方法和CCIR方法的比较

本文将“国际参考电离层”所采用的CCIR频率预测方法和亚大地区F_2电离层预测方法预测的f_0F_2和M(3000)F_2,分别与第21太阳活动周的我国实测数据进行了比较。结果表明,从总体上看,在中国区域内亚大地区F_2电离层预测方法优于CCIR方法。文章建议,在没有更好方法的情况下,未来的“中国参考电离层”可以采用亚大地区F_2电离层预测方法。     

太阳活动区R9077引起的强烈吸收事件

利用南极中山站的观测数据分析了太阳活动区R9077所引起的强烈吸收事件，其中2000年7月14日的太阳质子事件引起了持续3天多强烈的极盖吸收，同时，激烈的太阳活动使磁层处于极度扰动状态，磁层高能粒子沉降使许多持续时间较短的吸收峰叠加在极盖吸收背景之上，最突出的是7月1日的吸收增强事件，其最大值达26dB。这是自1997年2月中山站安装成像式宇宙噪声接收机以来观测到的最强的吸收，另一个较突出的吸收峰发生在14日1753UT前后，本文还讨论了产生这些吸收的原由。     

低电离层中的行星波扰动及其垂直传播

根据武昌电离层观象台接收的罗兰－Ｃ ＬＦ无线电波的传播资料，利用小波分析方法，研究了１９８５年和１９８６年冬季的低电离层中的行星波扰动及其垂直传播。结果表明：（１）两个冬季中，在７５ｋｍ和９５ｋｍ高度上，均存在明显的行星波扰动，主要成分是５－１０天和１０－２０天周期的波动，扰动幅度随高度增长，但增长值小于理论增长值；（２）在７５ｋｍ高度上的扰动和９５ｋｍ高度上的扰动，具有十分相似的扰动形态。根据行     

武昌低电离层LF观测的季节变化

通过分析武昌低电离层LF观测数据,得到了中低纬度低电离层电子密度剖面的季节变化特征及其与太阳天顶角周年变化的关系,给出LF相位周年振荡幅度的年际变化曲线．     

Equatorial vertical E × B drift velocities inferred from ionosonde measurements over Ouagadougou and the IRI-2007 vertical ion drift model

F-region vertical plasma drift velocities were deduced from the hourly hmF2 values acquired from ionogram data over a near dip equatorial station Ouagadougou (12.4°N, 358.5°E, dip angle 5.9°N) in Africa. Our results are compared against the global empirical model of Scherliess and Fejer (1999) incorporated in the IRI model (IRI-2007) for 1600 to 0800 LT from 1 year of data during sunspot maximum year of 1989 (yearly average solar flux intensity, F10.7 = 192) corresponding to the peak phase of solar cycle 22, under magnetically quiet conditions. The drifts are entirely downward between 2000 and 0500 LT bin for both techniques and the root mean square error (RMSE) between the modeled and the ionosonde vertical plasma drifts during these periods is 3.80, 4.37, and 4.74 m/s for June solstice, December solstice and equinox, respectively. Ouagadougou average vertical drifts show evening prereversal enhancement (PRE) velocity peaks (V_ZP) of about 16, 14, and 17 m/s in June solstice, December solstice, and equinox, respectively, at 1900–2000 LT; whereas global empirical model average drifts indicate V_ZP of approximately 33 m/s (June solstice), 29 m/s (December solstice), and 50 m/s (equinox) at 1800 LT. We find very weak and positive correlation (+0.10376) between modeled V_ZP versus F10.7, while ionosonde V_ZP against F10.7 gives worst and opposite correlation (−0.05799). The results also show that modeled V_ZP–Ap indicates good and positive correlation (+0.64289), but ionosonde V_ZP–Ap exhibits poor and negative correlation (−0.22477).     

A study of long-term climatology of ionospheric irregularities by using GPS phase fluctuations at the Brazilian longitudes

We have examined the ionospheric plasma irregularities that were recorded by using three ground-based receivers of the global positioning system (GPS) located at Brazilian longitudes during the period of a complete solar cycle, 1995–2005. The statistic results show that ionospheric irregularities are very easy to occur in December solstice months but rare to occur in June solstice months. Besides, the occurrence rates of irregularities in both December and June solstice months are little dependent on solar activity. However, in equinoctial months, the development of irregularities is obviously dependent on solar activity. There is a new finding in this study that if strong irregularities are distinguished from moderate ones, their occurrence rates would increase with solar activity during the December solstice months.     

High-resolution, coupled thermosphere–ionosphere models for space weather applications

Current first-principles global models of the coupled thermosphere–ionosphere (T–I) system use grids that are too coarse to simulate the mesoscale and small-scale structures that occur in this complex system. These small-scale and mesoscale structures have a great effect on global-scale neutral and plasma distributions and have important consequences for daily space weather. In this paper, we present a new first-principles, high-resolution, T–I nested grid (TING) polar cap model that incorporates multiple nesting levels and two-way interaction. The TING model simulation of the electron densities and temperatures demonstrates the importance of high spatial resolution. It is found that both the mid-latitude electron density trough and its associated dawn electron temperature peak are more pronounced and structured in the nested grid than in the coarse grid. Using the TING model to simulate ionospheric F₂ region electron density variations with geomagnetic activity and universal time (UT) is also discussed.     

Development of a campaign to study equatorial ionospheric phenomena over Guam

The United States Air Force Academy (USAFA) is in the process of developing a series of ground-based and space-based experiments to investigate the equatorial ionosphere over Guam and the southern crest of the Equatorial Appleton Anomaly over New Guinea. On the ground the Digital Ionospheric Sounder (University of Massachusetts, Lowell DPS-4 unit) and a dual-frequency GPS TEC/scintillation monitor will be used to investigate ionospheric phenomena in both campaign and long-term survey modes. In campaign mode, we will combine these observations with those collected from space during USAFA’s FalconSAT-3 and FalconSAT-5 low Earth orbit satellite missions, which will be active over a period of several years beginning in the first quarter of the 2007 calendar year. Additionally, we will investigate the long-term morphology of key ionospheric characteristics useful for driving the International Reference Ionosphere, such as critical frequencies (f_oE, f_oF1, f_oF2, etc.), the M(3000) F2 parameter (the maximum useable frequency for a signal refracted within the F2 layer and received on the ground at a distance of 3000 km away), and a variety of other characteristics. Specific targets of investigation include: (a) a comparison of TEC observed by the GPS receiver with those calculated by IRI driven by DPS-4 observations, (b) a comparison of plasma turbulence observed on-orbit with ionospheric conditions as measured from the ground, and (c) a comparison between topside ionospheric satellite in situ measurements of plasma density during an overpass of a Digisonde versus the calculated value based on extrapolation of the electron density profiles using Digisonde data and a topside α-Chapman function. This last area of investigation is discussed in detail in this paper.