Based on the comparison with the Earth, using the LB magnetic field model, the distribution of O+ ion originating from the ionosphere in the Martian magnetosphere is theoretically studied under different conditions of...Based on the comparison with the Earth, using the LB magnetic field model, the distribution of O+ ion originating from the ionosphere in the Martian magnetosphere is theoretically studied under different conditions of the tail-like magnetic field. The results show that the tail-like magnetic field has influence on the O+ ion flux in the Martian magnetotail: (i) the O+ ion flux in the Martian tail will increase if the tail-like magnetic field increases; when the tail-like magnetic field increases from 5 nT to 20 nT, the O+ ion flux increases 3 times in the region of 2.8R m in the Martian tail; and (ii) the O+ ion flux decreases with increasing intrinsic moment; when the intrinsic moment increases about 5 times, the flux decreases to one fourth in the region of 2.8R m in the Martian tail. According to the data on the O+ ion flux and theoretical result in this paper, the deduced Martian intrinsic moment is about 2 ×1021 Gcm3. This is consistent with the most recent observation by the USA satellite MGS.展开更多
Observed Martian crustal magnetism shows that the Mars does not possess a global-scale,dynamo-driven intrinsic magnetic field.In addition,the remnant field at the surface is hemi-spherically asymmetric.Our earlier sim...Observed Martian crustal magnetism shows that the Mars does not possess a global-scale,dynamo-driven intrinsic magnetic field.In addition,the remnant field at the surface is hemi-spherically asymmetric.Our earlier simulation results suggest that the Martian dynamo could be sub-critical near its end(the energy required to sustain a subcritical dynamo is less than that to excite the dynamo)and the generated field morphology is non-dipolar.We further the study to examine the characteristics of the magnetic field via Empirical Orthogonal Function(EOF)analysis on the subcritical dynamo solutions with the Rayleigh number Rth = 2480(below the critical point for the onset of the Martian dynamo).Our results show that the magnetic field is dominantly equatorial dipolar.Reversals and excursions occur frequently,and the magnetic dipole moment does not vary monotonically in time.展开更多
The electron spectrometer of Mars Express (MEX) provides the flux of low energy electrons (<20 keV) near Mars. 96 pieces of continuously measured data are analyzed, and the crossings of the magnetic pileup boundary...The electron spectrometer of Mars Express (MEX) provides the flux of low energy electrons (<20 keV) near Mars. 96 pieces of continuously measured data are analyzed, and the crossings of the magnetic pileup boundary (MPB) can be determined by fitting the energy spectrum of the low energy electrons. The shape and position of the MPB can be gained from these crossings, and they are in good agreement with the results obtained by the Mars Global Surveyor (MGS) and Phobos-2. In addition, we classify these crossings based on the crustal magnetic field nearby. It turns out that the position of MPB near the strong (>50 nT) crustal magnetic field is higher than the position of the MPB near the weak (<10 nT) crustal magnetic field. This result reflects the effect of the crustal magnetic field on the interaction between the Martian atmosphere and solar wind.展开更多
基金This work was supported by the National Natural Science Foundation of China ( Grant No. 49884002) .
文摘Based on the comparison with the Earth, using the LB magnetic field model, the distribution of O+ ion originating from the ionosphere in the Martian magnetosphere is theoretically studied under different conditions of the tail-like magnetic field. The results show that the tail-like magnetic field has influence on the O+ ion flux in the Martian magnetotail: (i) the O+ ion flux in the Martian tail will increase if the tail-like magnetic field increases; when the tail-like magnetic field increases from 5 nT to 20 nT, the O+ ion flux increases 3 times in the region of 2.8R m in the Martian tail; and (ii) the O+ ion flux decreases with increasing intrinsic moment; when the intrinsic moment increases about 5 times, the flux decreases to one fourth in the region of 2.8R m in the Martian tail. According to the data on the O+ ion flux and theoretical result in this paper, the deduced Martian intrinsic moment is about 2 ×1021 Gcm3. This is consistent with the most recent observation by the USA satellite MGS.
文摘Observed Martian crustal magnetism shows that the Mars does not possess a global-scale,dynamo-driven intrinsic magnetic field.In addition,the remnant field at the surface is hemi-spherically asymmetric.Our earlier simulation results suggest that the Martian dynamo could be sub-critical near its end(the energy required to sustain a subcritical dynamo is less than that to excite the dynamo)and the generated field morphology is non-dipolar.We further the study to examine the characteristics of the magnetic field via Empirical Orthogonal Function(EOF)analysis on the subcritical dynamo solutions with the Rayleigh number Rth = 2480(below the critical point for the onset of the Martian dynamo).Our results show that the magnetic field is dominantly equatorial dipolar.Reversals and excursions occur frequently,and the magnetic dipole moment does not vary monotonically in time.
文摘The electron spectrometer of Mars Express (MEX) provides the flux of low energy electrons (<20 keV) near Mars. 96 pieces of continuously measured data are analyzed, and the crossings of the magnetic pileup boundary (MPB) can be determined by fitting the energy spectrum of the low energy electrons. The shape and position of the MPB can be gained from these crossings, and they are in good agreement with the results obtained by the Mars Global Surveyor (MGS) and Phobos-2. In addition, we classify these crossings based on the crustal magnetic field nearby. It turns out that the position of MPB near the strong (>50 nT) crustal magnetic field is higher than the position of the MPB near the weak (<10 nT) crustal magnetic field. This result reflects the effect of the crustal magnetic field on the interaction between the Martian atmosphere and solar wind.
