Using the data of Cluster C3 during the interval of 17:10:00–17:40:00 UT on 17 June 2008,we investigated the polytropic processes of ions in a plasma mantle event in the vicinity of magnetopause near the cusp.Based o...Using the data of Cluster C3 during the interval of 17:10:00–17:40:00 UT on 17 June 2008,we investigated the polytropic processes of ions in a plasma mantle event in the vicinity of magnetopause near the cusp.Based on the interplanetary magnetic field(IMF)and solar wind conditions~3 h before this event,it is inferred that these mantle ions originate from the cusp.By analyzing the magnetohydrodynamic(MHD)Bernoulli integral(MBI)of this event,it was found that the plasma mantle is composed of many independent streamline-tubes,a few streamline-tube bundles,and transition layers between them.The MBI of streamline-tube is slightly higher than that in the typical magnetosheath,and one order higher than that in the solar wind.Most of the time,the kinetic energy density and enthalpy of mantle ions are the main components of MBI.Based on the homogeneous MBI method,more than 700 polytropic processes occurring in the plasma mantle streamline-tubes were identified,and their accurate ion polytropic indices were calculated.It shows that the range of these polytropic indices is broad,mainly from-1.6 to 3.5,with median and mean values of 1.12 and 1.08.The distribution of these indices is similar to that of the magnetosheath and wider than that of the central plasma sheet(CPS),and they are all within the coverage range of the solar wind.This indicates that there is a certain spatial evolution in the polytropic processes of solar wind,magnetosheath,plasma mantle,and plasma sheet ions,which also reflects the continuous conversion of kinetic energy into internal and static-pressure energy for plasma in these regions.These results indicate that plasma mantle ions can frequently experience various types of short-lived polytropic processes.These polytropic processes are direct manifestations of internal energy changes,and clarifying these polytropic processes and their evolutionary laws is crucial for understanding the mechanism of energy transport in the solar-terrestrial space.展开更多
This study reports a new model of an air standard Dual-Miller cycle(DMC) with two polytropic processes and heat transfer loss.The two reversible adiabatic processes which could not be realized in practice are replaced...This study reports a new model of an air standard Dual-Miller cycle(DMC) with two polytropic processes and heat transfer loss.The two reversible adiabatic processes which could not be realized in practice are replaced with two polytropic processes in order to more accurately reflect the practical working performance. The heat transfer loss is taken into account. The expressions of power output, thermal efficiency, entropy generation rate(EGR) and ecological function are addressed using finite-time thermodynamic theory. Through numerical calculations, the influences of compression ratio, cut-off ratio and polytropic exponent on the performance are thermodynamically analyzed. The model can be simplified to other cycle models under specific conditions, which means the results have an certain universality and may be helpful in the design of practical heat engines. It is shown that the entropy generation minimization does not always lead to the best system performance.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.12375250)。
文摘Using the data of Cluster C3 during the interval of 17:10:00–17:40:00 UT on 17 June 2008,we investigated the polytropic processes of ions in a plasma mantle event in the vicinity of magnetopause near the cusp.Based on the interplanetary magnetic field(IMF)and solar wind conditions~3 h before this event,it is inferred that these mantle ions originate from the cusp.By analyzing the magnetohydrodynamic(MHD)Bernoulli integral(MBI)of this event,it was found that the plasma mantle is composed of many independent streamline-tubes,a few streamline-tube bundles,and transition layers between them.The MBI of streamline-tube is slightly higher than that in the typical magnetosheath,and one order higher than that in the solar wind.Most of the time,the kinetic energy density and enthalpy of mantle ions are the main components of MBI.Based on the homogeneous MBI method,more than 700 polytropic processes occurring in the plasma mantle streamline-tubes were identified,and their accurate ion polytropic indices were calculated.It shows that the range of these polytropic indices is broad,mainly from-1.6 to 3.5,with median and mean values of 1.12 and 1.08.The distribution of these indices is similar to that of the magnetosheath and wider than that of the central plasma sheet(CPS),and they are all within the coverage range of the solar wind.This indicates that there is a certain spatial evolution in the polytropic processes of solar wind,magnetosheath,plasma mantle,and plasma sheet ions,which also reflects the continuous conversion of kinetic energy into internal and static-pressure energy for plasma in these regions.These results indicate that plasma mantle ions can frequently experience various types of short-lived polytropic processes.These polytropic processes are direct manifestations of internal energy changes,and clarifying these polytropic processes and their evolutionary laws is crucial for understanding the mechanism of energy transport in the solar-terrestrial space.
基金supported by the National Natural Science Foundation of China(Grant No.51576207)
文摘This study reports a new model of an air standard Dual-Miller cycle(DMC) with two polytropic processes and heat transfer loss.The two reversible adiabatic processes which could not be realized in practice are replaced with two polytropic processes in order to more accurately reflect the practical working performance. The heat transfer loss is taken into account. The expressions of power output, thermal efficiency, entropy generation rate(EGR) and ecological function are addressed using finite-time thermodynamic theory. Through numerical calculations, the influences of compression ratio, cut-off ratio and polytropic exponent on the performance are thermodynamically analyzed. The model can be simplified to other cycle models under specific conditions, which means the results have an certain universality and may be helpful in the design of practical heat engines. It is shown that the entropy generation minimization does not always lead to the best system performance.
