M.V. Teltsov

Magnetic storms in October 2003

Preliminary results of an analysis of satellite and ground-based measurements during extremely strong magnetic storms at the end of October 2003 are presented, including some numerical modeling. The geosynchronous satellites Ekspress-A2and Ekspress-A3, and the low-altitude polar satellites Coronas-F and Meteor-3M carried out measurements of charged particles (electrons, protons, and ions) of solar and magnetospheric origin in a wide energy range. Disturbances of the geomagnetic field caused by extremely high activity on the Sun were studied at more than twenty magnetic stations from Lovozero (Murmansk region) to Tixie (Sakha-Yakutia). Unique data on the dynamics of the ionosphere, riometric absorption, geomagnetic pulsations, and aurora observations at mid-latitudes are obtained.

Radiation dose measurements aboard the Mir using the R-16 instrument.

Data from the R-16 radiation dosimeter mounted to the outside of the Mir space station are analyzed to determine the radiation environment and absorbed radiation dose inside Mir during the 22nd solar cycle. The outcome of the analysis demonstrated that data could be collected over a long period, dynamics of the daily mean absorbed doses correlated well with parameters of solar activity, seasonal variations of absorbed doses during the solar cycle were clearly observed, during periods of unfavorable conditions the absorbed dose rate within the living modules can reach up to 30 mrad/min for more than 10 minutes, and overall, the radiation environment inside the space station was low.

Variations of the radiation dose onboard Mir station

Dose variations, associated with the 11-year solar activity cycle, seasonal variations of particle fluxes in the Earths radiation belts at the station orbit, and solar proton events are studied, using prolonged measurements of radiation doses inside orbital station Mir. Daily averages of radiation doses during the declining phase of the 22nd solar cycle and during transition to the 23rd solar activity cycle reached very large values for astronauts and significantly exceed the values calculated according to existing models.

Study of electric field fluctuations using the intercosmos-Bulgaria-1300 satellite data

Abstract Analysis of electric field and particle precipitating flux data measured by the Intercosmos- Bulgaria-1300 satellite was performed. It was found that the power spectra of the upper ionosphere electrostatic field fluctuations exhibit a power law dependence with an exponent close to sol−5 3 , similar to the Kolmogorovs spectral distribution. A field-aligned potential drop between the magnetosphere and the ionosphere was estimated using the electron and ion precipitating fluxes data, which allowed to reconstruct large-scale fluctuations of electrostatic field in the magnetosphere. It was found that the spectra of fluctuations of the electrostatic field in the magnetosphere differ significantly from the ionospheric spectra, having a weaker dependence on k. This agrees well with the results directly obtained by Weimer at al. using the Dynamics Explorer 1 and 2 electric field data. It reveals a possibility to estimate the large-scale features of the magnetospheric electric field spectra by using solely the date from low-altitude satellites.

Hot plasma pressure variations on the geostationary orbit on the base of Gorizont satellite data

Abstract Plasma and energetic particles pressure distribution is studied using data from the plasma and energetic particle experiment (0.1 – 133 keV) onboard the Gorizont-35 geostationary satellite for the period from 11 to 25 March 1992. The analysed period consists of relatively quiet time, small geomagnetic storms, SC and the time of the northern orientation of the IMF. The calculations show that the basic contribution to the total particle pressure was made by ions at the energy from 0.1 to 12.4 keV. The derived average value of the calculated pressure (∼1 nPa) points to the important role of the geostationary orbit plasma population in the formation of the magnetosphere pressure balance and of the near-Earth magnetic field distortion.

Geostationary orbit plasma pressure variations according to gorizont satellite data

Abstract Plasma and energetic particles pressure distribution is studied using data from the plasma and energetic particle experiment (0.1 –133 keV) onboard the Gorizont-35 geostationary satellite for the period from 11 to 25 March 1992. The analysed period consists of relatively quiet time, small geomagnetic storms, SC and the time of the northern orientation of the IMF. The calculations show that the basic contribution to the total particle pressure was made by ions at the energy from 0.1 to 12.4 keV. The derived average value of the calculated pressure (≈1 nPa) points to the important role of the geostationary orbit plasma population in the formation of the magnetopause pressure balance and of the near-Earth magnetic field distortion.

Auroral electron precipitation when the trapped radiation region collapsed during the main phase of the geomagnetic storm of May 15, 2005

The simultaneous measurements of the boundary of the trapped radiation region, where auroral electrons precipitate, on the Meteor-3M satellite (the circular polar orbit at an altitude of ∼1000 km) and the westward electrojet dynamics during the main phase of a strong (Dst = −263 nT) magnetic storm that occurred on May 15, 2005, are analyzed. At the end of the first hour of the storm main phase, the nightside boundary of the trapped radiation region and the peak of the precipitating electron fluxes with a energies of ∼1 keV shifted toward the Earth to L ∼ 3. The westward electrojet center approached the same L shell. Near the boundary of the trapped radiation region, the auroral electron spectrum had the shape of typical inverted V. The differential spectrum maximum shifted to an energy of ∼100 eV, when the latitude decreased by ∼1°. The nightside boundary of the trapped radiation region, the electron precipitation equatorward boundary, and the westward electrojet center are compared with the known empirical dependences of the position of these structures on the Dst variation amplitude.

Detection and prediction of absorbed radiation doses from solar proton fluxes onboard orbital stations

We consider cases of simultaneous detection of the absorbed doses produced by proton fluxes of powerful solar events onboard the Mir and ISS orbital stations and the Ekspress A3 geosynchronous satellite. Experimental data are analyzed using a software package that takes into account the energy spectra of protons at the Earths orbit depending on the time of event evolution, as well as their penetration to near-earth orbits and through the protective shields of spacecraft. Based on a comparison of the experimental data of dosimeters with the calculation of absorbed doses under the action of solar proton events, we developed a method of estimating the effective thickness of the shielding of dosimeters and made some estimates. A possibility is considered for predicting the radiation hazard onboard orbital stations upon the appearance of solar proton events using dosimeter data from a geosynchronous orbit.

Observation of the Near Plasma Sheet, Ring Current, and Energetic Electrons from Radiation Belts at a Geosynchronous Orbit, March 11–25, 1992

The dynamics of near plasma sheet electrons and ions (E≈ 0.1–12.4 keV), ring current protons (Ei≈ 41–133 keV), and energetic electrons from the Earths radiation belts (Ee≈ 97–1010 keV) is considered using the data from the Gorizont-34and Gorizont-35geosynchronous satellites from March 11–25, 1992. Peculiarities of this period are a long (more than 4 days) interval of the northward interplanetary magnetic field (Bz> 0) and a high-speed stream of the solar wind with an enhanced particle density. The SC and compression of the magnetosphere to the geosynchronous orbit (GMC) preceded this interval. Under quiet and moderately disturbed geomagnetic conditions and under a prolonged northward interplanetary magnetic field, we observed a significant decrease of fluxes and softening of spectra of the electron component of plasma in the energy ranges of 0.1–12.4 keV and 97–1010 keV, and of the ion component of plasma at energies of 0.1–4 keV, while the intensity of 5–12.4 keV ion fluxes increases by about one order of magnitude. The peculiarities of distributions of energetic particle fluxes observed in the period under consideration can be associated with significant variations of the convection conditions and a decreased or fully suppressed injection of energetic electrons into the geosynchronous orbit region.

Observations of near plasma sheet, ring current and energetic electrc radiation belt under northward IMF condition

Abstract The dynamics of different plasma domains is studied using data from the plasma ( E i , e =0.1–12.4 keV) and energetic particle ( E i =41–133 keV, E e =97–1010 keV) experiments onboard the geostationary satellites “Gorizont-34” and “Gorizont-35” for the period from 11 to 25 March 1992. The analysed period consists of relatively quiet time, small geomagnetic storms, SC and the long time (>4 days) of the northward interplanetary magnetic field. The observed features of the energetic particle flux distributions were “untypical” for the geostationary orbit region: the decrease of the electron fluxes by about a factor of ten; the decrease of the ion fluxes in the energy range from about 100 eV to 400 eV by about a factor of 5–10 and the formation of the intensive fluxes of ions at the energy ∼5–12.4 keV. The obtained results consist qualitatively with the conception of a closed topology of the magnetosphere for the steady northward interplanetary magnetic field condition and point to the dependence of the magnetospheric mechanism of the charged particle acceleration on the interplanetary magnetic field parameters.