D-region electron density and effective recombination coefficients during twilight ― experimental data and modelling during solar proton events
D-region electron density and effective recombination coefficients during twilight ― experimental data and modelling during solar proton events
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暮光期间的 D 区电子密度和有效复合系数——太阳质子事件期间的实验数据和建模
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发表时间：
2009
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通讯作者：
V. Tereschenko
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作者：
A. Osepian;S. Kirkwood;P. Dalin;V. Tereschenko
抽象的。对低D区(海拔70公里以下)的电子密度的准确测量很少。这既适用于地面设施和探空火箭的测量，也适用于安静条件和高能电子沉淀条件下的测量。在太阳质子事件期间，高能太阳质子通量深入大气层会在整个D区产生额外的电离，包括较低的海拔，这为使用地面设施进行精确测量提供了有利条件。在这项研究中，我们表明，用两个地面设施在几乎相同的纬度但略有不同的经度测量的电子密度，为验证模型计算提供了一个有价值的工具。使用的两种技术是无线电波的非相干散射(挪威特罗姆索的EISCAT 224 MHz雷达，北纬69.6°，东经19.3°)和无线电波的部分反射(俄罗斯摩尔曼斯克附近的2.8 MHz雷达，北纬69.0°，东经35.7°)。这两种雷达都能在SPE过程中给出准确的电子密度值，EISCAT雷达从57-60千米以上的高度，部分反射技术在55-70千米之间。接近中午时，两个地点的太阳天顶角几乎没有差别，两种方法在重叠高度给出的电子密度值大致相同。在黄昏，当太阳天顶角的差异增大时，电子密度值就会发散。当两部雷达都处于夜间条件(太阳天顶角99°)时，重叠高度的电子密度再次变得相等。我们使用联合测量来验证模型计算的电离层参数f+、λ，αEf及其在太阳质子事件期间的变化。这些参数是低电离层结构的重要特征，是其他方法无法确定的。
Abstract. Accurate measurements of electron density in the lower D-region (below 70 km altitude) are rarely made. This applies both with regard to measurements by ground-based facilities and by sounding rockets, and during both quiet conditions and conditions of energetic electron precipitation. Deep penetration into the atmosphere of high-energy solar proton fluxes (during solar proton events, SPE) produces extra ionisation in the whole D-region, including the lower altitudes, which gives favourable conditions for accurate measurements using ground-based facilities. In this study we show that electron densities measured with two ground-based facilities at almost the same latitude but slightly different longitudes, provide a valuable tool for validation of model computations. The two techniques used are incoherent scatter of radio waves (by the EISCAT 224 MHz radar in Tromso, Norway, 69.6° N, 19.3° E), and partial reflection of radio-waves (by the 2.8 MHz radar near Murmansk, Russia, 69.0° N, 35.7° E). Both radars give accurate electron density values during SPE, from heights 57–60 km and upward with the EISCAT radar and between 55–70 km with the partial reflection technique. Near noon, there is little difference in the solar zenith angle between the two locations and both methods give approximately the same values of electron density at the overlapping heights. During twilight, when the difference in solar zenith angles increases, electron density values diverge. When both radars are in night conditions (solar zenith angle >99°) electron densities at the overlapping altitudes again become equal. We use the joint measurements to validate model computations of the ionospheric parameters f+, λ, αeff and their variations during solar proton events. These parameters are important characteristics of the lower ionosphere structure which cannot be determined by other methods.