Utilizing observations by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument,we quantitatively assessed the dawn-dusk asymmetry in temperature disturbances within the high-latitude mes...Utilizing observations by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument,we quantitatively assessed the dawn-dusk asymmetry in temperature disturbances within the high-latitude mesosphere and lower thermosphere(MLT)during the main phase of geomagnetic storms in this study.An analysis of five geomagnetic superstorm events indicated that during the main phase,negative temperature disturbances were more prevalent on the dawn side than on the dusk side in the high-latitude MLT region.Results of a statistical analysis of 54 geomagnetic storm events also revealed a notable disparity in temperature disturbances between the dawn and dusk sides.At high latitudes,38.2%of the observational points on the dawn side exhibited negative temperature disturbances(less than−5 K),whereas on the dusk side,this percentage was only 29.5%.In contrast,at mid-latitudes,these proportions were 34.1%and 36.5%,respectively,showing no significant difference.We also conducted a statistical analysis of temperature disturbances at different altitudes,which revealed an increase in the proportion of warming disturbances with altitude.Conversely,the proportion of cooling disturbances initially rose with altitude,reaching a peak around 105 km,and subsequently decreased.These temperature disturbance differences could be explained by the day-night asymmetry in vertical wind disturbances during storm conditions.展开更多
The dawn-dusk asymmetry of the magne- tosheath under quasi-steady states has been studied by using a newly developed 3D MHD magnetosphere simulation model. The results show that the dawn-dusk asymmetry is substantial ...The dawn-dusk asymmetry of the magne- tosheath under quasi-steady states has been studied by using a newly developed 3D MHD magnetosphere simulation model. The results show that the dawn-dusk asymmetry is substantial because of the Parker spiral IMF. It is found that the dawn-dusk magnetosheath thickness asymmetry is the effect of different shock conditions. The plasma density and flux asymmetry are mainly caused by the different thickness of the dawn-dusk magnetosheath, and the magnetic recon- nection on the magnetopause has no significant effects. It is also showed that the Plasma Depletion Layer in front of the dayside magnetopause can cause duskward plasma flow, and the total plasma flux on the dusk side will be higher.展开更多
This study is concerned with determining the altitude of the sun under the horizon to the beginning and the end of the true and pseudo dawn and dusk. In 2007 and 2008, the Sky Quality Meter (SQM) was used in four regi...This study is concerned with determining the altitude of the sun under the horizon to the beginning and the end of the true and pseudo dawn and dusk. In 2007 and 2008, the Sky Quality Meter (SQM) was used in four regions in Malaysia to measure the brightness at night, pseudo dawn, true dawn, true dusk and pseudo dusk. The measurements were taken when the device was directed to the position of sunrise and sunset at the horizontal angle of the sunrise or sunset and at five degrees above the horizon during the entire monitoring period. The altitude of the sun for the true dusk was found to be -14.38°± 0.91°and for the beginning of the pseudo dusk was found to be -14.86°± 0.91°and the end of the pseudo dusk is -17.8°± 0.7°, while for the beginning of the true dawn it was found to be -14.19°± 0.52°(for high confidence -14.71°) and for the pseudo dawn was found to be -18.62°± 0.82°. The light magnitude of the full night after the pseudo dusk was found to be 20.77 ± 0.93 mag./arcsec<sup>2</sup>, while it was found to be 22.17 ± 0.1 mag./arcsec<sup>2</sup> before the pseudo dawn.展开更多
本文基于自己开发的全球三维磁层模型,模拟研究了IMF(Interplanetary Magnetic Field)北向时磁层顶重联及磁尾结构.结果发现磁层顶附近存在两种典型的重联过程:一是高纬极尖区IMF与地球磁场的重联,这与空间观测证据和前人的模拟结果是...本文基于自己开发的全球三维磁层模型,模拟研究了IMF(Interplanetary Magnetic Field)北向时磁层顶重联及磁尾结构.结果发现磁层顶附近存在两种典型的重联过程:一是高纬极尖区IMF与地球磁场的重联,这与空间观测证据和前人的模拟结果是一致的;二是重联后一端在太阳风中另一端与地球相连的磁力线在向磁尾运动中,会发生弯曲、拖曳,在磁尾晨昏侧低纬区域可与尾瓣开放磁力线满足重联条件而再次发生重联.我们认为前一重联会使磁尾等离子片产生与IMF时钟角方向相反的旋转;而后者可重新形成闭合磁力线,可能是LLBL(Low Latitude Boundary Layer)形成的重要原因.展开更多
基金the National Key R&D Program of China(Grant No.2022YFF0503702)the National Natural Science Foundation of China(Grant Nos.42004132,42074195 and 42074183)+1 种基金the open funding of the Ministry of Natural Resources Key Laboratory for Polar Science(Grant No.KP202104)the China Geological Survey(Grant No.ZD20220145).
文摘Utilizing observations by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument,we quantitatively assessed the dawn-dusk asymmetry in temperature disturbances within the high-latitude mesosphere and lower thermosphere(MLT)during the main phase of geomagnetic storms in this study.An analysis of five geomagnetic superstorm events indicated that during the main phase,negative temperature disturbances were more prevalent on the dawn side than on the dusk side in the high-latitude MLT region.Results of a statistical analysis of 54 geomagnetic storm events also revealed a notable disparity in temperature disturbances between the dawn and dusk sides.At high latitudes,38.2%of the observational points on the dawn side exhibited negative temperature disturbances(less than−5 K),whereas on the dusk side,this percentage was only 29.5%.In contrast,at mid-latitudes,these proportions were 34.1%and 36.5%,respectively,showing no significant difference.We also conducted a statistical analysis of temperature disturbances at different altitudes,which revealed an increase in the proportion of warming disturbances with altitude.Conversely,the proportion of cooling disturbances initially rose with altitude,reaching a peak around 105 km,and subsequently decreased.These temperature disturbance differences could be explained by the day-night asymmetry in vertical wind disturbances during storm conditions.
基金This work was supported by the National Natural Science Foundation of China(Grant No.40390150).
文摘The dawn-dusk asymmetry of the magne- tosheath under quasi-steady states has been studied by using a newly developed 3D MHD magnetosphere simulation model. The results show that the dawn-dusk asymmetry is substantial because of the Parker spiral IMF. It is found that the dawn-dusk magnetosheath thickness asymmetry is the effect of different shock conditions. The plasma density and flux asymmetry are mainly caused by the different thickness of the dawn-dusk magnetosheath, and the magnetic recon- nection on the magnetopause has no significant effects. It is also showed that the Plasma Depletion Layer in front of the dayside magnetopause can cause duskward plasma flow, and the total plasma flux on the dusk side will be higher.
文摘This study is concerned with determining the altitude of the sun under the horizon to the beginning and the end of the true and pseudo dawn and dusk. In 2007 and 2008, the Sky Quality Meter (SQM) was used in four regions in Malaysia to measure the brightness at night, pseudo dawn, true dawn, true dusk and pseudo dusk. The measurements were taken when the device was directed to the position of sunrise and sunset at the horizontal angle of the sunrise or sunset and at five degrees above the horizon during the entire monitoring period. The altitude of the sun for the true dusk was found to be -14.38°± 0.91°and for the beginning of the pseudo dusk was found to be -14.86°± 0.91°and the end of the pseudo dusk is -17.8°± 0.7°, while for the beginning of the true dawn it was found to be -14.19°± 0.52°(for high confidence -14.71°) and for the pseudo dawn was found to be -18.62°± 0.82°. The light magnitude of the full night after the pseudo dusk was found to be 20.77 ± 0.93 mag./arcsec<sup>2</sup>, while it was found to be 22.17 ± 0.1 mag./arcsec<sup>2</sup> before the pseudo dawn.
文摘本文基于自己开发的全球三维磁层模型,模拟研究了IMF(Interplanetary Magnetic Field)北向时磁层顶重联及磁尾结构.结果发现磁层顶附近存在两种典型的重联过程:一是高纬极尖区IMF与地球磁场的重联,这与空间观测证据和前人的模拟结果是一致的;二是重联后一端在太阳风中另一端与地球相连的磁力线在向磁尾运动中,会发生弯曲、拖曳,在磁尾晨昏侧低纬区域可与尾瓣开放磁力线满足重联条件而再次发生重联.我们认为前一重联会使磁尾等离子片产生与IMF时钟角方向相反的旋转;而后者可重新形成闭合磁力线,可能是LLBL(Low Latitude Boundary Layer)形成的重要原因.
