The growth rate of solar activity in the early phase of a solar cycle has been known to be well correlated with the subsequent amplitude （solar maximum）. It provides very useful information for a new solar cycle as ...The growth rate of solar activity in the early phase of a solar cycle has been known to be well correlated with the subsequent amplitude （solar maximum）. It provides very useful information for a new solar cycle as its variation reflects the temporal evolution of the dynamic process of solar magnetic activities from the initial phase to the peak phase of the cycle. The correlation coefficient between the solar maximum （Rmax） and the rising rate （βa） at Am months after the solar minimum （Rmin） is studied and shown to increase as the cycle progresses with an inflection point （r = 0.83） at about Am = 20 months. The prediction error of Rmax based on βa is found within estimation at the 90% level of confidence and the relative prediction error will be less than 20% when Am ≥ 20. From the above relationship, the current cycle （24） is preliminarily predicted to peak around October, 2013 with a size of Rmax = 84 ＋ 33 at the 90% level of confidence.展开更多
The topology and dynamics of the three-dimensional magnetic field in the solar atmosphere govern various solar eruptive phenomena and activities, such as flares, coronal mass ejections, and filaments/prominences. We h...The topology and dynamics of the three-dimensional magnetic field in the solar atmosphere govern various solar eruptive phenomena and activities, such as flares, coronal mass ejections, and filaments/prominences. We have to observe and model the vector magnetic field to understand the structures and physical mechanisms of these solar activities. Vector magnetic fields on the photosphere are routinely observed via the polarized light, and inferred with the inversion of Stokes profiles. To analyze these vector magnetic fields, we need first to remove the 180° ambiguity of the transverse components and correct the projection effect. Then, the vector magnetic field can be served as the boundary conditions for a force-free field modeling after a proper preprocessing. The photospheric velocity field can also be derived from a time sequence of vector magnetic fields.Three-dimensional magnetic field could be derived and studied with theoretical force-free field models, numerical nonlinear force-free field models, magnetohydrostatic models, and magnetohydrodynamic models. Magnetic energy can be computed with three-dimensional magnetic field models or a time series of vector magnetic field. The magnetic topology is analyzed by pinpointing the positions of magnetic null points, bald patches, and quasi-separatrix layers. As a well conserved physical quantity,magnetic helicity can be computed with various methods, such as the finite volume method, discrete flux tube method, and helicity flux integration method. This quantity serves as a promising parameter characterizing the activity level of solar active regions.展开更多
In this work,the ionospheric variability is analyzed by applying the wavelet decomposition technique to the noontime fo F2,F10.7,interplanetary magnetic field(IMF)Bz,Ap,and lower thermospheric temperature at pressure ...In this work,the ionospheric variability is analyzed by applying the wavelet decomposition technique to the noontime fo F2,F10.7,interplanetary magnetic field(IMF)Bz,Ap,and lower thermospheric temperature at pressure of 10?4 h Pa in 2002.Results show that the variance of periodic oscillations in the ionosphere is largest in the 2–4-day period and declines with the increase of the period.The maximum variance of the periodic oscillations in solar irradiation is in the 16–32-day period.For geomagnetic activities,most of the variance is about equally distributed on intervals of periods shorter than 32 days.Variance distributions of IMF Bz and lower thermospheric temperature are similar to those of the ionosphere.They show the maximum in the 2–4-day period and decline with the increase of the period.By analyzing the distributions of the variances,the potential connections between the ionosphere and the external sources are discussed.展开更多
The geomagnetic storm is one of the most important geomagnetic disturbance phenomena in the geospace.Many studies assume that input of solar wind energy into the Earth's ring current only occurs when IMF Bz in GSM...The geomagnetic storm is one of the most important geomagnetic disturbance phenomena in the geospace.Many studies assume that input of solar wind energy into the Earth's ring current only occurs when IMF Bz in GSM coordinates is southward;the ring current energy injection and decay under northward IMF Bz are not well understood and still need further investigation.In this paper,by using the large amount of data from the year 1964 to 2010,we use the empirical phase space analysis method to study the ring current energy injection and decay under northward IMF Bz and compare the results with those under southward IMF Bz condition.We have found that the largest injection Q under northward IMF Bz condition is only 7% of the largest injection under southward IMF Bz,implying that there is a very limit energy injected into the ring current region when IMF Bz is northward.The decay time decreases as VBz increases and shows a good linear trend for southward IMF Bz;while for the northward IMF Bz,there is not a clear relation between τ varies and VBz.Having taken τ as a function of injection Q instead of VBz,we have obtained the empirical relation of τ with Q for northward and southward IMF Bz conditions:the two categories are further combined together and the empirical relation τ= e(2.6 0.039 Q) is derived.Further,the pressure-corrected Dst formula Dst=Dst b P+c is derived for both southward and northward IMF Bz conditions,where the coefficients b and c are 6.9/10.4 and 10.0/15.2 when IMF Bz is southward and northward respectively.The statistical results on between the different geomagnetic indices(Dst,Kp,AE) and IMF Bz are also obtained.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.10973020,40890161 and 10921303)the National Basic Research Program of China (Grant No.2011CB811406)the China Meteorological Administration (Grant No.GYHY201106011)
文摘The growth rate of solar activity in the early phase of a solar cycle has been known to be well correlated with the subsequent amplitude （solar maximum）. It provides very useful information for a new solar cycle as its variation reflects the temporal evolution of the dynamic process of solar magnetic activities from the initial phase to the peak phase of the cycle. The correlation coefficient between the solar maximum （Rmax） and the rising rate （βa） at Am months after the solar minimum （Rmin） is studied and shown to increase as the cycle progresses with an inflection point （r = 0.83） at about Am = 20 months. The prediction error of Rmax based on βa is found within estimation at the 90% level of confidence and the relative prediction error will be less than 20% when Am ≥ 20. From the above relationship, the current cycle （24） is preliminarily predicted to peak around October, 2013 with a size of Rmax = 84 ＋ 33 at the 90% level of confidence.
基金supported by National Natural Science Foundation of China (Grant Nos. 11533005, 11203014, 11373023, and 11303016)National Key Basic Research Special Foundation (Grant No. 2014CB744203)
文摘The topology and dynamics of the three-dimensional magnetic field in the solar atmosphere govern various solar eruptive phenomena and activities, such as flares, coronal mass ejections, and filaments/prominences. We have to observe and model the vector magnetic field to understand the structures and physical mechanisms of these solar activities. Vector magnetic fields on the photosphere are routinely observed via the polarized light, and inferred with the inversion of Stokes profiles. To analyze these vector magnetic fields, we need first to remove the 180° ambiguity of the transverse components and correct the projection effect. Then, the vector magnetic field can be served as the boundary conditions for a force-free field modeling after a proper preprocessing. The photospheric velocity field can also be derived from a time sequence of vector magnetic fields.Three-dimensional magnetic field could be derived and studied with theoretical force-free field models, numerical nonlinear force-free field models, magnetohydrostatic models, and magnetohydrodynamic models. Magnetic energy can be computed with three-dimensional magnetic field models or a time series of vector magnetic field. The magnetic topology is analyzed by pinpointing the positions of magnetic null points, bald patches, and quasi-separatrix layers. As a well conserved physical quantity,magnetic helicity can be computed with various methods, such as the finite volume method, discrete flux tube method, and helicity flux integration method. This quantity serves as a promising parameter characterizing the activity level of solar active regions.
基金supported by the National Natural Science Foundation of China(Grant Nos.41174134 and 41274156)the National Basic Research Program of China("973"Project)(Grant No.2011CB811405)
文摘In this work,the ionospheric variability is analyzed by applying the wavelet decomposition technique to the noontime fo F2,F10.7,interplanetary magnetic field(IMF)Bz,Ap,and lower thermospheric temperature at pressure of 10?4 h Pa in 2002.Results show that the variance of periodic oscillations in the ionosphere is largest in the 2–4-day period and declines with the increase of the period.The maximum variance of the periodic oscillations in solar irradiation is in the 16–32-day period.For geomagnetic activities,most of the variance is about equally distributed on intervals of periods shorter than 32 days.Variance distributions of IMF Bz and lower thermospheric temperature are similar to those of the ionosphere.They show the maximum in the 2–4-day period and decline with the increase of the period.By analyzing the distributions of the variances,the potential connections between the ionosphere and the external sources are discussed.
文摘The geomagnetic storm is one of the most important geomagnetic disturbance phenomena in the geospace.Many studies assume that input of solar wind energy into the Earth's ring current only occurs when IMF Bz in GSM coordinates is southward;the ring current energy injection and decay under northward IMF Bz are not well understood and still need further investigation.In this paper,by using the large amount of data from the year 1964 to 2010,we use the empirical phase space analysis method to study the ring current energy injection and decay under northward IMF Bz and compare the results with those under southward IMF Bz condition.We have found that the largest injection Q under northward IMF Bz condition is only 7% of the largest injection under southward IMF Bz,implying that there is a very limit energy injected into the ring current region when IMF Bz is northward.The decay time decreases as VBz increases and shows a good linear trend for southward IMF Bz;while for the northward IMF Bz,there is not a clear relation between τ varies and VBz.Having taken τ as a function of injection Q instead of VBz,we have obtained the empirical relation of τ with Q for northward and southward IMF Bz conditions:the two categories are further combined together and the empirical relation τ= e(2.6 0.039 Q) is derived.Further,the pressure-corrected Dst formula Dst=Dst b P+c is derived for both southward and northward IMF Bz conditions,where the coefficients b and c are 6.9/10.4 and 10.0/15.2 when IMF Bz is southward and northward respectively.The statistical results on between the different geomagnetic indices(Dst,Kp,AE) and IMF Bz are also obtained.
