曲靖E区场向不规则体回波特征观测研究
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摘要
利用曲靖VHF相干散射雷达2016年3月至2018年2月间持续观测数据,对电离层E区场向不规则体(field-aligned irregularities, FAI)回波形态特征进行统计分析,结果表明:E区FAI回波在地方时和高度上呈现出三个高发区间,日侧主要位于07:00—12:00LT和90～105 km,而夜侧两个高发区间分别对应于15:00—01:00LT和90～100 km以及18:00—04:00LT和100～115 km;E区FAI回波发生率还具有明显的季节变化,夏季5—8月是其高发期,而冬季的11和12月发生率为极小; E区FAI回波多普勒速度均在-85～85 m/s变化,而其谱宽主要分布在60 m/s以内,三个区间的平均多普勒速度均仅为数m/s,明显小于其平均谱宽,后者约在20～30 m/s.此外,高度分层研究发现,日侧E区FAI的各层平均多普勒速度总体上为负值,但在96 km高度上下薄层内存在一个小幅正值,而夜侧则以105 km高度为界,其上端各层均为负值,下端各层均为正值.曲靖E区FAI表现出典型的Ⅱ型回波特征,其生成和演变过程源自电离层电子密度梯度漂移不稳定性,子午风和低F区电场在其中起着重要作用.
Using the data of the VHF coherent scatter radar in Qujing from March 2016 to February 2018, the morphological characteristics of the ionospheric E-region field-aligned irregularities(FAI) echo are statistically analyzed. The results show that the E-region FAI echoes preferentially occur in three areas, the daytime echoes mainly appear during 07:00—12:00 LT at an altitude of 90—105 km, while the two nighttime echoes are clearly visible during 15:00—01:00 LT at an altitude of 90—100 km and during 18:00—04:00 LT at an altitude of 100—115 km, respectively. Moreover, E-region FAI echoes exhibit distinguishable seasonal variation, i.e., maximum occurrence during May to August, but the minimum occurrence in November and December. The Doppler velocity of these three echoes varies between-85 m/s and 85 m/s with a spectral width of 0—60 m/s, and the mean Doppler velocity is only several m/s which is much smaller than the mean spectral width(20—30 m/s).In addition,we find that the mean Doppler velocity of echoes in the daytime E-region is generally negative,but with a small positive value in the thin layer around the height of 96 km.However,the nighttime E-region is obviously separated by a height of105 km where the upper are negative,but the lower are positive.The characteristics of E-region FAI in Qujing is typical of type Ⅱ.The generation and evolution process are attributed to ionospheric electron density gradient drift instability in which the meridional wind and low F-region electric field play an important role.
Using the data of the VHF coherent scatter radar in Qujing from March 2016 to February 2018, the morphological characteristics of the ionospheric E-region field-aligned irregularities(FAI) echo are statistically analyzed. The results show that the E-region FAI echoes preferentially occur in three areas, the daytime echoes mainly appear during 07:00—12:00 LT at an altitude of 90—105 km, while the two nighttime echoes are clearly visible during 15:00—01:00 LT at an altitude of 90—100 km and during 18:00—04:00 LT at an altitude of 100—115 km, respectively. Moreover, E-region FAI echoes exhibit distinguishable seasonal variation, i.e., maximum occurrence during May to August, but the minimum occurrence in November and December. The Doppler velocity of these three echoes varies between-85 m/s and 85 m/s with a spectral width of 0—60 m/s, and the mean Doppler velocity is only several m/s which is much smaller than the mean spectral width(20—30 m/s).In addition,we find that the mean Doppler velocity of echoes in the daytime E-region is generally negative,but with a small positive value in the thin layer around the height of 96 km.However,the nighttime E-region is obviously separated by a height of105 km where the upper are negative,but the lower are positive.The characteristics of E-region FAI in Qujing is typical of type Ⅱ.The generation and evolution process are attributed to ionospheric electron density gradient drift instability in which the meridional wind and low F-region electric field play an important role.
引文
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[19] LEE C C,LIU J Y,PAN C J.The heights of sporadic-E layer simultaneously observed by the VHF radar and ionosondes in Chung-Li[J].Geophysical research letters,2000,27(5):641-644.
[20] SUDAN R N,KESKINEN M J.Unified theory of the power spectrum of intermediate wavelength ionospheric electron density fluctuations[J].Journal of geophysical research,1984,89(A11):9840-9844.
[21] ZHOU C,LIU Y,TANG Q,et al.Investigation on the occurrence of mid-latitude E-region irregularity by Wuhan VHF radar and its relationship with sporadic E layer[J].IEEE transactions on geoscience and remote sensing,2018,PP(99):1-10.
[22] 赵海生,许正文,吴振森,等.东亚地区Es特性研究[J].空间科学学报,2014,34(1):38-45.ZHAO H S,XU Z W,WU Z S,et al.Sporadic E morphology of East Asia[J].Chinese journal of space science,2014,34(1):38-45.(in Chinese)
[23] KRISHNAMURTHY B V,RAVINDRAN S,VISW ANATHAN K S,et al.Small scale(～3m) E-region irregularities at and off the magnetic equator[J].Journal of geophysical research,1998,103(A9):20761-20772.
[24] KAGAN L M,KELLEY M C.A wind-driven gradient drift mechanism for mid-latitude E-region ionospheric irregularities[J].Geophysical research letters,1998,25(22):4141-4144.
[2] FEJER B G,KELLEY M C.Ionospheric irregularities[J].Reviews of geophysics and space physics,1980,18(2):401-454.
[3] 陈培仁.雷达研究E层不均匀结构的最新进展[J].空间科学学报,1996,16(1):43-50.CHEN P R.The latest advances on E region irregularities study by coherent radar[J].Chinese journal of space science,1996,16(1):43-50.(in Chinese)
[4] MILLMAN G H.Field-aligned ionization scatter geometry[J].Journal of geophysical research,1969,74(3):900-905.
[5] LEADABRAND R L,YABROFF I.The geometry of auroral communications[J].IRE transactions on antennas and propagation,1958,6(1):80-87.
[6] YAMAMOTO M,FUKAO S,WOODMAN R F,et al.Mid-latitude E region field-aligned irregularities observed with the MU radar[J].Journal of geophysical research,1991,96(A9):15943-15949.
[7] YAMAMOTO M,FUKAO S,OGAWA T,et al.A morphological study on mid-latitude E-region field-aligned irregularities observed with the MU radar[J].Journal of atmospheric and solar-terrestrial physics,1992,54(6):769-777.
[8] HALDOUPIS C,SCHLEGEL K.Characteristic of midlatitude coherent backscatter from the ionospheric E region obtained with sporadic E scatter experiment[J].Journal of geophysical research,1996,101(A6):13387-13397.
[9] WOODMAN R F,CHAU J L,Aquino F,et al.Low-latitude field-aligned irregularities observed in the E region with the Piura VHF radar:first results[J].Radio science,1999,34(4):983-990.
[10] CHAU J L,WOODMAN R F,FLORES L A.Statistical characteristics of low-latitude ionospheric field-aligned irregularities obtained with the Piura VHF radar[J].Annales geophysicae,2002,20:1203-1212.
[11] PAN C J,RAO P B.Morphological study of the field-aligned E-layer irregularities observed by the Gadanki VHF radar[J].Annales geophysicae,2004,22:3799-3804.
[12] PATRA A K,SRIPATHI S,SIVAKUMAR V,et al.Statistical characteristics of VHF radar observations of low latitude E-region field-aligned irregularities over Gadanki[J].Journal of atmospheric and solar-terrestrial physics,2004,66:1615-1626.
[13] 宁百齐,李国主,胡连欢,等.基于三亚VHF雷达的场向不规则体观测研究:1.电离层E区连续性回波[J].地球物理学报,2013,56(3):719-730.NING B Q,LI G Z,HU L H,et al.Observations on the field-aligned irregularities using Sanya VHF radar:1.ionospheric E-region continuous echoes[J].Chinese journal of geophysics,2013,56(3):719-730.(in Chinese)
[14] 李国主,宁百齐,胡连欢,等.基于三亚VHF雷达的场向不规则体观测研究:2.东亚低纬电离层E区准周期回波[J].地球物理学报,2013,56(7):2141-2151.LI G Z,NING B Q,HU L H,et al.Observations on the field-aligned irregularities using Sanya VHF radar:2.low latitude ionospheric E-region quasi-periodic echoes in the East Asian sector[J].Chinese journal of geophysics,2013,56(7):2141-2151.(in Chinese)
[15] NING B Q,HU L H,LI G Z,et al.The first time observations of low-latitude ionospheric irregularities by VHF radar in Hainan[J].Science China technological sciences,2012,55(5):1-9.
[16] PAN C J,LIU C H,R?TTGER J,et al.A three dimensional study of E region irregularity patches in the equatorial anomaly region using the Chung-Li VHF radar[J].Geophysical research letters,1994,21(17):1763-1766.
[17] PAN C J,R?TTGER J,CHEN C L.Radar investigations of low-altitude quasi-periodic echoes in Chung-Li[J].Geophysical research letters,2005,32:L11102.DOI:10.1029/2004GL022136
[18] WANG C Y,CHU Y H,SU C L,et al.Statistical investigations of layer-type and clump-type plasma structures of 3-m field-aligned irregularities in nighttime sporadic E region made with Chung-Li VHF radar[J].Journal of geophysical research,2011,116(A12):A12311.DOI:10.1029/2011JA016696
[19] LEE C C,LIU J Y,PAN C J.The heights of sporadic-E layer simultaneously observed by the VHF radar and ionosondes in Chung-Li[J].Geophysical research letters,2000,27(5):641-644.
[20] SUDAN R N,KESKINEN M J.Unified theory of the power spectrum of intermediate wavelength ionospheric electron density fluctuations[J].Journal of geophysical research,1984,89(A11):9840-9844.
[21] ZHOU C,LIU Y,TANG Q,et al.Investigation on the occurrence of mid-latitude E-region irregularity by Wuhan VHF radar and its relationship with sporadic E layer[J].IEEE transactions on geoscience and remote sensing,2018,PP(99):1-10.
[22] 赵海生,许正文,吴振森,等.东亚地区Es特性研究[J].空间科学学报,2014,34(1):38-45.ZHAO H S,XU Z W,WU Z S,et al.Sporadic E morphology of East Asia[J].Chinese journal of space science,2014,34(1):38-45.(in Chinese)
[23] KRISHNAMURTHY B V,RAVINDRAN S,VISW ANATHAN K S,et al.Small scale(～3m) E-region irregularities at and off the magnetic equator[J].Journal of geophysical research,1998,103(A9):20761-20772.
[24] KAGAN L M,KELLEY M C.A wind-driven gradient drift mechanism for mid-latitude E-region ionospheric irregularities[J].Geophysical research letters,1998,25(22):4141-4144.