RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 9, ES3004, doi:10.2205/2007ES000276, 2007

3. Registration of Solar Activity Manifestations in the Near-Earth Space Environment

3.1. Magnetosphere and Radiation Belts

[23]  Conducting measurements of solar cosmic rays along the orbit of the CORONAS-F satellite by the SCR (Solar Cosmic Ray) equipment, a continuous series of the data on the fluxes of energetic solar particles was obtained, the data on the fluxes of solar electrons with energies above 300 keV being unique, because no other measurements has been conducted in this period.

[24]  The conducted measurements of solar cosmic rays made it possible to study the dynamics of the magnetosphere and radiation belts of the Earth and also changes in the boundaries of penetration of energetic solar particles into the magnetosphere in the periods of strong geomagnetic disturbances [Kuznetsov et al., 2007a, 2007b].

2007ES000276-fig11
Figure 11
[25]  The periods of extreme events on the Sun, in particular events in October-November 2003, when powerful flares on the Sun caused two very strong magnetic storms, were especially favorable for studying of effects of the solar-terrestrial relations. Figure 11 shows for this period an example of deformation of the magnetosphere and dynamics of the radiation belts accompanied by penetration of energetic particles to low L-shells.

[26]  Strong variations of the SCR penetration boundary were observed also during strong magnetic storms in November 2001. The variations of the penetration boundary of protons of SCR with an energy of 1-5 MeV and 50-90 MeV and electrons of SCR with an energy of 0.3-0.6 MeV as a function of the geomagnetic activity indices Kp and Dst for the dusk and dawn sectors of the magnetic local time (MLT) were observed. The stronger magnetic disturbances (larger values of Kp and larger negative values of Dst ) the lower the L value, and so solar energetic particles penetrate to lower latitudes and lower heights.

[27]  The experimental dependence of the penetration boundary of solar cosmic rays on the Dst and Kp indices of geomagnetic activity was approximated by the analytical formula in the form: L = a + b cdot Dst + c cdot Kp. The results of this approximation showed that for the electrons penetration boundary there exists a correlation between L and Kp at the daytime side of the Earth, whereas at the nighttime side the correlation between L, Kp, and Dst is of a small significance. For the penetration boundary of protons with an energy of 1-5 MeV, there exists a correlation between L, Kp, and Dst in the early morning and late evening hours, whereas in the early evening hours there exists a correlation between L and Kp. For the penetration boundary of protons with an energy of 50-90 MeV, there exists a correlation between L, Kp, and Dst almost in all hours when the measurements were conducted, except the early evening hours when it is enough to take into account the known relation between L and Kp.

[28]  International Space Station having the inclination of the orbit plane to the equatorial plane of 51o is able (taking into account the inclination of the magnetic dipole axis to the axis of the Earth's rotation sim11o ) to cross during its motion along the orbit the L -shells with L>4 at one-two orbits over the North America and Australia and only there to enter the region of penetration of protons with Ep > 50 MeV. However, according to the results obtained by the SONG device, if a powerful flare occurs during a strong magnetic storm (as it was the case, for example, on 29 October 2003), then ISS enters the region of SCR penetration at more than a half of the orbits. In such situation, a SCR burst presents a serious radiation danger for cosmonauts.

[29]  On the basis of the measurements by the CRM (Cosmic Ray Monitor) device of the SCR scientific equipment, the dynamics of the outer radiation belt of the Earth during strong magnetic storms caused by active events on the Sun is studied and the relation of its dynamics to the structural rebuilding of the magnetosphere is determined. The interaction of coronal mass ejections with the magnetosphere of the Earth led to a magnetic storm which was accompanied by a structural rebuilding of the magnetosphere: shrinking of the region of closed drift shells (region of the radiation belts), redistribution of the field lines into the magnetospheric tail, and increase in the polar cap dimensions.

2007ES000276-fig12
Figure 12
[30]  The dynamics of the radiation belts of the Earth and structural rebuilding of the magnetosphere were studied in detail by the CRM device in the periods of magnetic storms on 6 and 24 November 2001, 29 and 30 October 2003, and 15 May 2005. The integral effect of the magnetic storm impact on the outer radiation belt was also studied for the magnetic storm on 20 November 2004. The obtained data on the disturbances in the Earth's magnetosphere are shown in Figure 12 at the example of the magnetic storms on 6 and 24 November 2001 caused by mass ejections from the Sun. The storms had sudden commencements at 0153 LT on 6 November 2001 and 0556 LT on 24 November 2001, respectively.

2007ES000276-fig13
Figure 13
[31]  One can see in Figure 12 that in the 6 November 2001 event just after the sudden commencement of the magnetic storm, a main phase of the magnetic storm began. It was caused by the redistribution of magnetic field lines from the middle of the magnetosphere into its tail, intensification of the current in the plasma layer of the magnetospheric tail and its approaching the Earth. In the event on 24 November 2001 after the sudden commencement of the magnetic storm during 50 min the first phase of the magnetic storm was observed: compression of the magnetosphere with a weak increase of the field in the plasma layer of the magnetospheric tail with an increase of the field in the middle and with an adiabatic acceleration of the captured particles (the latter fact is seen in the increase of particle fluxes in Figure 13).

2007ES000276-fig14
Figure 14
[32]  Comparing Figures 13 and 14, one can see that at the main phase of the magnetic storm the region of the captured radiation existence shrank and the radiation belt maximum shifted to the L sim 3 shell reached by the boundary of SCR penetration. At the L<3 shells, the intensity of electrons almost did not change. One can see in Figure 14 that the recovery of the radiation belt of electrons in the 24 November 2001 event began only after 1700 UT.

2007ES000276-fig15
Figure 15
[33]  The minimal intensity of electrons in the maximum of the radiation belt and the minimal value of L in the belt maximum position were observed at 1223 UT in the maximum of the magnetic storm main phase. The dynamics of the radiation belt of electrons of various energies (0.3-0.6, 0.6-1.5, 1.5-3 and 3-6 MeV) during the magnetic storms of November 2001 and in the intervals between magnetic storms is shown in Figure 15. Till 6 November 2001, the maximum of the outer radiation belt for electrons with energies of 0.3-0.6 MeV and 0.6-1.5 Mev was located at the L sim 4 shell. After 6 November 2001, the maximum of the radiation belt of these electrons was formed at the L sim 3 shell with increased values of the intensity. At the L sim 3 shell to 15 November 2001, the electron belt with energies of 1.5-3 MeV and 3-6 MeV was gradually formed. For electrons with energies of 0.3-0.6 MeV to 15 November 2001, a gap began to be formed at the L sim 3 shell and two maxima at the L sim 2.5 and L sim 4 appeared. On 24 November 2001, the next magnetic storm changed the structure of the outer radiation belt again. The maximum of the radiation belt with increased intensity for electrons with energies of 0.3-0.6 MeV and 0.6-1.5 MeV was formed again at the L sim 3 shell.

[34]  Thus the structural rebuilding of the magnetosphere during a magnetic storm leads to a shrinking of the region of the outer radiation belt. After the end of a magnetic storm (the recovery phase), the outer radiation belt recovers. First the electron fluxes increase at the boundary of the penetration of SCR electrons at the moment of the magnetic storm, then the fluxes of electrons with an energy of a few MeV increase, and so the radiation belt structure could have two maxima.

[35]  Thus it is proved on the basis of the conducted measurements that the effect of the disappearance of the outer radiation belt of electrons at the main phase of magnetic storms at the energies above 1.5 MeV is due to the shrinking of the region in which the captured radiation could exist. After the end of a magnetic storm, the region of existence of the captured radiation recovers up to the pre-storm state.

3.2. Upper Atmosphere of the Earth

2007ES000276-fig16
Figure 16
[36]  At the observations of the upper atmosphere of the Earth, besides the known precipitations of energetic particles from the magnetosphere to the ionosphere in the near-polar regions and in the zone of the Brazilian anomaly, the AVS-F device detected localized (about 30o and 10o along geographic latitude and longitude, respectively) quasi-stationary low-latitude and equatorial precipitations as shown on Figure 16 provided by I. V. Arkhangel'skaya et al., (in press, 2008). These precipitations are characterized by a considerable increase in the radiation background (by 20-30%). Their lifetime can reach 8 days.

2007ES000276-fig17
Figure 17
[37]  According to the experiment with the RPS (X-ray spectrometer) device in the X-ray range 3-31.5 keV, charts of the emission of the nighttime upper atmosphere of the Earth caused by the impact on the atmosphere of fluxes of solar radiation, galactic cosmic rays, and charged particles precipitating from the magnetosphere were drawn (Figure 17). On the basis of these data, important regularities in the behavior of this emission are revealed: The existence of the long-period seasonal and depending on solar activity level variations in the nighttime emission of particular regions of the globe, such as the Brazilian anomaly region, regions of the outer radiation belt of electrons in the Southern and Northern Hemispheres, and also the smaller regions, such as global magnetic anomalies, is detected. For the first time the information also obtained on the fluxes of low-energy electrons of the radiation belts of the Earth precipitating into the Earth's atmosphere and responsible for its soft X-ray emission.

2007ES000276-fig18
Figure 18
[38]  Using the solar X-ray telescope of the CORONAS-F satellite, the upper atmosphere of the Earth was studied on the basis of the absorption of the hard X-ray radiation of the Sun at the entrances of the satellite to the shadow and exits out of it [Slemzin et al., 2003] (see Figure 18). On the basis of such observations, the height dependences of the absorption coefficients of the X-ray radiation were obtained with a high vertical resolution. The dependence of the density and composition of the Earth's atmosphere at altitudes up to 500 km on solar activity was studied. The content of molecular nitrogen and atomic oxygen was determined. For similar observations, fluxes of the solar radiation in the ultraviolet range were measured by the SUFR radiometer and VUSS spectrophotometer.

[39]  The observations of the upper atmosphere of the Earth carried out in the scope of the CORONAS-F project made it possible to obtain experimental data for creation of a modern model of the Earth's atmosphere. This is important in the light of the recent publication on the possible systematic trends in the parameters of the upper atmosphere and in relation to the global warming problem.


RJES

Citation: Kuznetsov, V. D. (2007), From the geophysical to heliophysical year: The results of the CORONAS-F project, Russ. J. Earth Sci., 9, ES3004, doi:10.2205/2007ES000276.

Copyright 2007 by the Russian Journal of Earth Sciences

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