Ionospheric response to the X‐class solar flare on 7 September 2005
Ionospheric response to the X‐class solar flare on 7 September 2005
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DOI：
10.1029/2011ja016961
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发表时间：
2011-11
影响因子：
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通讯作者：
B. Xiong;W. Wan;Libo Liu;P. Withers;B. Zhao;B. Ning;Yong Wei;H. Le;Z. Ren;Yiding Chen;M. He;Jing Liu
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作者：
B. Xiong;W. Wan;Libo Liu;P. Withers;B. Zhao;B. Ning;Yong Wei;H. Le;Z. Ren;Yiding Chen;M. He;Jing Liu
[1] 我们研究了 2005 年 9 月 7 日发生的强烈太阳耀斑 (X17.0/3B) 期间的极端电离层效应。通过 Millstone Hill、Sondrestrom 和 Tromso 的非相干散射雷达以及 CHAMP 卫星上的无线电掩星实验观察到强烈的 E 区电子密度增强。 Millstone Hill 和 Sondrestrom 站的观测结果显示，在 UT 17:40–18:10 期间电子密度的平均增强百分比在 E 区峰值高度附近超过 200%，但在 F 区域峰值高度附近仅为 10% 左右；从而导致E区电子密度超过F区电子密度的异常现象。我们将这种异常响应归因于此次耀斑期间 EUV 通量的微弱增强和 X 射线通量的强烈增强。为了进一步了解这一不寻常的特征，我们通过将测量得出的电子生产率与查普曼生产函数拟合的电子生产率进行比较来详细分析 E 区响应。我们的结果表明，查普曼产生理论在耀斑时间比在非耀斑时间更符合观测结果，这归因于耀斑和非耀斑时间太阳辐射光谱的明显差异。由于这次耀斑期间X射线通量的强烈增强，E区电子产生更多地以X射线为主，查普曼电离理论在耀斑时期比非耀斑时期更适用。此外，我们提出了一种根据电子密度剖面的电离层观测来估计有效太阳辐射通量的方法。用我们的方法得出的辐射通量与 GOES-12 观测到的 0.1-0.8 nm 处的 X 射线通量非常吻合。
[1] We investigate the extreme ionospheric effect during the intense solar flare (X17.0/3B) that occurred on 7 September 2005. A strong E region electron density enhancement is observed by the incoherent scatter radars at Millstone Hill, Sondrestrom, and Tromso, as well as by the radio occultation experiment on board the CHAMP satellite. The observations from both Millstone Hill and Sondrestrom stations show the average percentage enhancements of electron density during 17:40–18:10 UT are more than 200% near the E region peak height but only about 10% near the F region peak height; as a result, it leads to an unusual phenomenon that the E region electron density exceeds the F region electron density. We ascribe the unusual response to weak enhancement in EUV flux and strong enhancement in X-ray flux during this flare. To further understand this unusual feature, we analyze in detail the E region response by comparing the electron production rates derived from the measurements with those fitted by the Chapman production function. Our results demonstrate that the Chapman production theory fits the observations better in the flare time than in the nonflare time, which is attributed to the obvious difference in the solar radiation spectra at flare and nonflare times. Owing to the strong enhancement in X-ray flux during this flare, the E region electron production is more dominated by the X-ray, and the Chapman ionization theory is more applicable in the flare time than in the nonflare time. In addition, we propose a method to estimate the effective solar radiation flux from the ionospheric observations of electron density profiles. The radiation flux derived with our method agrees well with the X-ray flux at 0.1–0.8 nm observed by GOES-12.