By analysing a long series of data (1996-2019), we show that solar cycle 23 was more marked by violent solar flares and coronal mass ejections (CMEs) compared to solar cycle 24. In particular, the halo coronal mass ej...By analysing a long series of data (1996-2019), we show that solar cycle 23 was more marked by violent solar flares and coronal mass ejections (CMEs) compared to solar cycle 24. In particular, the halo coronal mass ejections associated with X-class flares appear to be among the most energetic events in solar activity given the size of the flares, the speed of the CMEs and the intense geomagnetic storms they produce. Out of eighty-six (86) X-class halo CMEs, thirty-seven (37) or 43% are highly geoeffective;twenty-four (24) or approximately 28% are moderately geoeffective and twenty-five (25) or 29% are not geoeffective. Over the two solar cycles (1996 to 2019), 71% of storms were geoeffective and 29% were not. For solar cycle 23, about 78% of storms were geoeffective, while for solar cycle 24, about 56% were geoeffective. For the statistical study based on speed, 85 halo CMEs associated with X-class flares were selected because the CME of 6 December 2006 has no recorded speed value. For both solar cycles, 75.29% of the halo CMEs associated with X-class flares have a speed greater than 1000 km/s. The study showed that 42.18% of halo (X) CMEs with speeds above 1000 km/s could cause intense geomagnetic disturbances. These results show the contribution (in terms of speed) of each class of halo (X) CMEs to the perturbation of the Earth’s magnetic field. Coronal mass ejections then become one of the key indicators of solar activity, especially as they affect the Earth.展开更多
We study the distribution of quasars on the celestial sphere according to ground-based SDSS and space-based WISE and Gaia observations. All distributions as a function of galactic latitude, b, exhibit a decrease in qu...We study the distribution of quasars on the celestial sphere according to ground-based SDSS and space-based WISE and Gaia observations. All distributions as a function of galactic latitude, b, exhibit a decrease in quasar frequency well outside the dust in and near the galactic plane. We prove that the observed decrease in quasar frequency at high galactic latitudes is not accompanied by reddening, meaning that it can not be caused by dust. The scattering of light by the circumgalactic gas is negligible because the Thomson scattering cross section is very small. We conclude the observed scattering of light must be caused by dark matter in the galactic halo. We determine the mass and charge of dark matter particles. If the dark matter particle is a fermion its mass, mDMand charge eDM=δe, where e is the elementary charge are: mDM=3.2×10−2eV and δ=3.856×10−5. If however the dark matter particle is spinless then: mDM=0.511eV and δ=2.132×10−4. These values for the charge of a dark matter particle are orders of magnitude higher than the upper limit of the neutrino charge according to laboratory experiments. Consequently, dark matter particles are not charged neutrinos. Since dark matter particles are charged, they must emit and absorb electromagnetic radiation. However, PDM~δ2, or: PDM~1.487×10−9Pe, where Peis the power output of a single electron.展开更多
This article addresses the design of the trajectory transferring from Earth to Halo orbit, and proposes a timing closed-loop strategy of correction maneuver during the transfer in the frame of circular restricted thre...This article addresses the design of the trajectory transferring from Earth to Halo orbit, and proposes a timing closed-loop strategy of correction maneuver during the transfer in the frame of circular restricted three body problem （CR3BP）. The relation between the Floquet multipliers and the magnitudes of Halo orbit is established, so that the suitable magnitude for the aerospace mission is chosen in terms of the stability of Halo orbit. The stable manifold is investigated from the Poincar6 mapping defined which is different from the previous researches, and six types of single-impulse transfer trajectories are attained from the geometry of the invariant manifolds. Based on one of the trajectories of indirect transfer which are ignored in the most of literatures, the stochastic control theory for imperfect information of the discrete linear stochastic system is applied to design the trajectory correction maneuver. The statistical dispersion analysis is performed by Monte-Carlo simulation,展开更多
文摘By analysing a long series of data (1996-2019), we show that solar cycle 23 was more marked by violent solar flares and coronal mass ejections (CMEs) compared to solar cycle 24. In particular, the halo coronal mass ejections associated with X-class flares appear to be among the most energetic events in solar activity given the size of the flares, the speed of the CMEs and the intense geomagnetic storms they produce. Out of eighty-six (86) X-class halo CMEs, thirty-seven (37) or 43% are highly geoeffective;twenty-four (24) or approximately 28% are moderately geoeffective and twenty-five (25) or 29% are not geoeffective. Over the two solar cycles (1996 to 2019), 71% of storms were geoeffective and 29% were not. For solar cycle 23, about 78% of storms were geoeffective, while for solar cycle 24, about 56% were geoeffective. For the statistical study based on speed, 85 halo CMEs associated with X-class flares were selected because the CME of 6 December 2006 has no recorded speed value. For both solar cycles, 75.29% of the halo CMEs associated with X-class flares have a speed greater than 1000 km/s. The study showed that 42.18% of halo (X) CMEs with speeds above 1000 km/s could cause intense geomagnetic disturbances. These results show the contribution (in terms of speed) of each class of halo (X) CMEs to the perturbation of the Earth’s magnetic field. Coronal mass ejections then become one of the key indicators of solar activity, especially as they affect the Earth.
文摘We study the distribution of quasars on the celestial sphere according to ground-based SDSS and space-based WISE and Gaia observations. All distributions as a function of galactic latitude, b, exhibit a decrease in quasar frequency well outside the dust in and near the galactic plane. We prove that the observed decrease in quasar frequency at high galactic latitudes is not accompanied by reddening, meaning that it can not be caused by dust. The scattering of light by the circumgalactic gas is negligible because the Thomson scattering cross section is very small. We conclude the observed scattering of light must be caused by dark matter in the galactic halo. We determine the mass and charge of dark matter particles. If the dark matter particle is a fermion its mass, mDMand charge eDM=δe, where e is the elementary charge are: mDM=3.2×10−2eV and δ=3.856×10−5. If however the dark matter particle is spinless then: mDM=0.511eV and δ=2.132×10−4. These values for the charge of a dark matter particle are orders of magnitude higher than the upper limit of the neutrino charge according to laboratory experiments. Consequently, dark matter particles are not charged neutrinos. Since dark matter particles are charged, they must emit and absorb electromagnetic radiation. However, PDM~δ2, or: PDM~1.487×10−9Pe, where Peis the power output of a single electron.
基金National Natural Science Foundation of China (10702003)Innovation Foundation of Beijing University of Aeronautics and Astronautics for Ph.D. Graduates
文摘This article addresses the design of the trajectory transferring from Earth to Halo orbit, and proposes a timing closed-loop strategy of correction maneuver during the transfer in the frame of circular restricted three body problem （CR3BP）. The relation between the Floquet multipliers and the magnitudes of Halo orbit is established, so that the suitable magnitude for the aerospace mission is chosen in terms of the stability of Halo orbit. The stable manifold is investigated from the Poincar6 mapping defined which is different from the previous researches, and six types of single-impulse transfer trajectories are attained from the geometry of the invariant manifolds. Based on one of the trajectories of indirect transfer which are ignored in the most of literatures, the stochastic control theory for imperfect information of the discrete linear stochastic system is applied to design the trajectory correction maneuver. The statistical dispersion analysis is performed by Monte-Carlo simulation,
