SAMI2(Sami2 is Another Model of the Ionosphere)是美国海军实验室开发的电离层物理模型.利用该物理模型,模拟了东亚扇区不同太阳活动强度、不同纬度地区三个站的电离层电子浓度总含量(TEC).通过模拟结果与GPS观测站TEC数据的比较,检...SAMI2(Sami2 is Another Model of the Ionosphere)是美国海军实验室开发的电离层物理模型.利用该物理模型,模拟了东亚扇区不同太阳活动强度、不同纬度地区三个站的电离层电子浓度总含量(TEC).通过模拟结果与GPS观测站TEC数据的比较,检验SAMI2在此扇区的电离层TEC计算精度.结果表明,物理模型输出的电离层TEC具备与观测数据一致的周日变化、季节变化,太阳活动变化.周日分布上,上午时段SAMI2 TEC与观测数据吻合度优于午后时段;季节分布上,SAMI2 TEC在冬季与观测值偏差小于其他季节;SAMI2 TEC与GPS TEC相关系数各站均达到0.87以上,与赤道地区Guam站相关性最好;太阳活动低年计算结果优于太阳活动高年;多数情况下,SAMI2 TEC相对GPS TEC偏大.本文结果为基于SAMI2模型构建背景误差分布特征,开展该区域电离层数值预报研究可行性提供了理论支持.展开更多
This paper reports that plasma density depletions appearing at middle latitudes near sunrise survived until afternoon on 29 May 2017 during the recovery phase of a geomagnetic storm.By analyzing GPS data collected in ...This paper reports that plasma density depletions appearing at middle latitudes near sunrise survived until afternoon on 29 May 2017 during the recovery phase of a geomagnetic storm.By analyzing GPS data collected in Japan,we investigate temporal variations in the horizontal two-dimensional distribution of total electron content(TEC)during the geomagnetic storm.The SYM-H index reached-142 n T around 08 UT on 28 May 2017.TEC depletions extending up to approximately 38°N along the meridional direction appeared over Japan around 05 LT(LT=UT+9 hours)on 29 May 2017,when TEC rapidly increased at sunrise due to the solar extreme ultraviolet(EUV)radiation.The TEC depletions appeared sequentially over Japan for approximately 8 hours in sunlit conditions.At 06 LT on 29 May,when the plasma depletions first appeared over Japan,the background TEC was enhanced to approximately 17 TECU,and then decreased to approximately 80%of the TEC typical of magnetically quiet conditions.We conclude that this temporal variation of background plasma density in the ionosphere was responsible for the persistence of these plasma depletions for so long in daytime.By using the Naval Research Laboratory:Sami2 is Another Model of the Ionosphere(SAMI2),we have evaluated how plasma production and ambipolar diffusion along the magnetic field may affect the rate of plasma depletion disappearance.Simulation shows that the plasma density increases at the time of plasma depletion appearance;subsequent decreases in the plasma density appear to be responsible for the long-lasting persistence of plasma depletions during daytime.The plasma density depletion in the top side ionosphere is not filled by the plasma generated by the solar EUV productions because plasma production occurs mainly at the bottom side of the ionosphere.展开更多
文摘SAMI2(Sami2 is Another Model of the Ionosphere)是美国海军实验室开发的电离层物理模型.利用该物理模型,模拟了东亚扇区不同太阳活动强度、不同纬度地区三个站的电离层电子浓度总含量(TEC).通过模拟结果与GPS观测站TEC数据的比较,检验SAMI2在此扇区的电离层TEC计算精度.结果表明,物理模型输出的电离层TEC具备与观测数据一致的周日变化、季节变化,太阳活动变化.周日分布上,上午时段SAMI2 TEC与观测数据吻合度优于午后时段;季节分布上,SAMI2 TEC在冬季与观测值偏差小于其他季节;SAMI2 TEC与GPS TEC相关系数各站均达到0.87以上,与赤道地区Guam站相关性最好;太阳活动低年计算结果优于太阳活动高年;多数情况下,SAMI2 TEC相对GPS TEC偏大.本文结果为基于SAMI2模型构建背景误差分布特征,开展该区域电离层数值预报研究可行性提供了理论支持.
基金supported by the Japan Society for the Promotion of Science,KAKENHI Grants,16H06286 and 20H00197supported by NASA(NNH17ZDA001N07)NSF(AGS-1931415)grants(JDH)。
文摘This paper reports that plasma density depletions appearing at middle latitudes near sunrise survived until afternoon on 29 May 2017 during the recovery phase of a geomagnetic storm.By analyzing GPS data collected in Japan,we investigate temporal variations in the horizontal two-dimensional distribution of total electron content(TEC)during the geomagnetic storm.The SYM-H index reached-142 n T around 08 UT on 28 May 2017.TEC depletions extending up to approximately 38°N along the meridional direction appeared over Japan around 05 LT(LT=UT+9 hours)on 29 May 2017,when TEC rapidly increased at sunrise due to the solar extreme ultraviolet(EUV)radiation.The TEC depletions appeared sequentially over Japan for approximately 8 hours in sunlit conditions.At 06 LT on 29 May,when the plasma depletions first appeared over Japan,the background TEC was enhanced to approximately 17 TECU,and then decreased to approximately 80%of the TEC typical of magnetically quiet conditions.We conclude that this temporal variation of background plasma density in the ionosphere was responsible for the persistence of these plasma depletions for so long in daytime.By using the Naval Research Laboratory:Sami2 is Another Model of the Ionosphere(SAMI2),we have evaluated how plasma production and ambipolar diffusion along the magnetic field may affect the rate of plasma depletion disappearance.Simulation shows that the plasma density increases at the time of plasma depletion appearance;subsequent decreases in the plasma density appear to be responsible for the long-lasting persistence of plasma depletions during daytime.The plasma density depletion in the top side ionosphere is not filled by the plasma generated by the solar EUV productions because plasma production occurs mainly at the bottom side of the ionosphere.
