Influence of the interplanetary magnetic field on ULF oscillations of the ionospheric resonator

A weak but statistically reliable dependence of the diurnal activity of oscillations in the ionospheric Alfvén resonator on orientation of the interplanetary magnetic field ahead of the magnetospheric front has been detected based on observations of ULF oscillations at Sayan solar observatory Mondy of the Institute of Solar–Terrestrial Physics. The interpretation of the result has been proposed. The essence is that the electromagnetic fluctuations penetrate into the magnetosphere from the interplanetary environment and influence the ionospheric resonator. The formulation of the problem and the method of solving it are part of the broad program of the experimental and theoretical study of the influence of the interplanetary magnetic field on the oscillation regime of ULF oscillations of the magnetosphere.     

Relationship between the fluxes of relativistic electrons at geosynchronous orbit and the level of ULF activity on the Earth’s surface and in the solar wind during the 23rd solar activity cycle

We present the results of a cross-correlation analysis made on the basis of Spearman’s rank correlation method. The quantities to correlate are daily values of the fluence of energetic electrons at a geosynchronous orbit, intensities of ground and interplanetary ultra-low-frequency (ULF) oscillations in the Pc5 range, and parameters of the solar wind. The period under analysis is the 23rd cycle of solar activity, 1996–2006. Daily (from 6 h to 18 h of LT) magnetic data at two diametrically opposite observatories of the Intermagnet network are taken as ground-based measurements. The fluxes of electrons with energies higher than 2 MeV were measured by the geosynchronous GOES satellites. The data of magnetometers and plasma instruments installed on ACE and WIND spacecraft were used for analysis of the solar wind parameters and of the oscillations of the interplanetary magnetic field (IMF). Some results elucidating the role played by interplanetary ULF waves in the processes of generation of magneospheric oscillations and acceleration of energetic electrons are obtained. Among them are (i) high and stable correlation of ground ULF oscillations with waves in the solar wind; (ii) closer link of mean daily amplitudes of both interplanetary and ground oscillations with ‘tomorrow’ values of the solar wind velocity than with current values; and (iii) correlation of the intensity of ULF waves in the solar wind, normalized to the IMF magnitude, with fluxes of relativistic electrons in the magnetosphere.     

Magnetospheric and ionospheric manifestations of interplanetary foreshocks

The geometry of a typical interplanetary shock front in the vicinity of the Earth’s orbit predicts that the leading edge of the foreshock region comes into contact with the magnetosphere a few hours ahead of geomagnetic sudden impulses (SI). There is reason to believe that the interaction of the magnetosphere with the foreshock leads to magnetic and ionospheric disturbances, which can be detected by ground-based instruments. We searched for specific precursors of SIs in data from the Scandinavian riometer network and in the short period geomagnetic pulsation data from mid-latitude magnetometers. We found that SIs were preceded by the following three features: (1) an increase in riometric absorption, (2) excitation of Pcl magnetic pulsations and (3) a spectral broadening of the Pc3 magnetic pulsations. Our observations may be useful for the study of acceleration processes in the solar wind. These observations are also of potential forecasting interest.     

Solar wind dependence of the Pc1 wave activity

There are a host of factors influencing the excitation of Pc1 geomagnetic pulsations, which are ULF waves in the frequency range between 0.2 and 5 Hz. We have studied carefully the dependence of the pearl-type Pc1 activity at Sodankylä, Finland (L = 5.1) on the plasma density N in front of the magnetosphere, the bulk velocity V of the solar wind, and the intensity B of the IMF. The result is as follows: high values of N and reduced values of V are favorable to appearance of Pc1, whereas the dependence of Pc1 activity on B is practically absent. We also show that the probability of Pc1 occurrence decreases with the interplanetary electric field, and increases with solar wind impact pressure and with the plasma to magnetic pressure ratio “beta”.     

Approaches to the development of biomedical support systems for piloted exploration missions

Many aspects of the biomedical systems developed and realized aboard orbital stations, the International space station in the first place, deserve to be regarded as predecessors of the systems for health monitoring and maintenance of future exploration crews. At the same time, there are issues and tasks which have not been yet fully resolved. Specifically, these are prevention of the adverse changes in body systems and organs due to microgravity, reliable protection from the spectrum of space radiation, and elucidation of possible effects of hypomagnetic environment. We should not walk away from search and development of key biomedical technologies such as a system of automated fitness evaluation and a psychodiagnostic complex for testing and optimization of operator′s efficiency, and others. We have to address a large number of issues related to designing the composite life support systems of the utmost autonomy, closure and ecological safety of the human environment that will provide transformation of all kinds of waste. Another crucial task is to define a concept of the onboard medical center and dataware including the telemedicine technology. All the above developments should assimilate the most recent achievements in physiology, molecular biology, genetics, and advanced medical technologies. Biomedical researches on biosatellites also do not lose topicality.     

Some radiation environment estimation data from 10–12 km altitude aircraft

The results of probing the radiation environment on board different civil aviation planes with singletype detectors (nuclear emulsions), with particular emphasis to the cosmic radiation flux measured inside aircraft, are presented. The measurement results make it possible to find the absorbed and equivalent doses induced by the cosmic radiation neutrons and charged particles.     

Recent results of the joint ESA-DARA/IBMP experiments Biokosmos "Seeds"

Comparison of experimental data obtained from short (SDEF) and long duration exposure flights (LDEF) have recently led to results which will be significant for longer and/or repeated sojourn of man in space. Under orbital conditions biological stress and damage are induced in test subjects by cosmic radiation, especially the high energetic, densely ionizing component of heavy ions. Plant seeds were successful model systems for a biotest in studying the physiological damages and mutagenic effect caused by ionizing cosmic radiation in particular stem cells. Dosimetrically, the subdivision into charge- and Let-groups reveals the contribution of the intermediate group (LET = 350-1000 MeV/cm) due to the medium heavy ions (Z = 6-10). Their relative contribution increases with the lower inclination of the orbit of LDEF-1; on the other hand, the total fluence becomes higher with longer duration of the flight. The observed endpoints of the biological radiation damage hint at a correlation with particle dose rate rather than with the dose; additionally, data on shielding effects inside and outside the space craft and its exposure were gained from the different SDEF- and LDEF-missions.     

Possible Origin of Ultralow-Frequency Whistlers

The sonographic analysis of records of ultralow-frequency emissions recorded by the induction magnetometer at the Mirnyi observatory (Antarctica) in 1981–1985 has revealed the presence of a special class of signals in the frequency band 0.25–5 Hz having a characteristic dispersion reminiscent of the dynamic spectra of LHR-whistlers observed in the VLF band. The ULF whistlers are observed, as a rule, at morning and evening hours of local time at moderate values of the K _p-index (0 < K _p < 4). The analysis of the frequency–time behavior of observed signals shows that the canalized propagation of short broadband pulses as magnetosonic waves in the layered medium, for example, in the magnetospheric current sheet can serve as a possible cause of the dispersion. Such sporadic phenomena on the magnetopause as microreconnections or FTE-events may be sources of these pulses.     

Qualitative estimation of magnetic storm efficiency in producing relativistic electron flux in the Earth’s outer radiation belt using geomagnetic pulsations data

It is well known that during many but not all of the geomagnetic storms enhanced fluxes of high-energy electrons are observed in the outer radiation belt. Here we examine relativistic (>2 MeV) electron fluxes measured by GOES at the synchronous orbit and on-ground observations of two types of ULF pulsations during 30 magnetic storms occurred during 1996–2000. To characterize the effectiveness of the chosen magnetic storms in producing relativistic electron fluxes, following to (Reeves, G.D., McAdams, K.L., Friedel, R.H.W., O’Brien, T.R. Acceleration and loss of relativistic electrons during geomagnetic storms. Geophys. Res. Lett. 30, doi:10.1029/2002GL016513, 2003), we calculate a ratio of the maximum daily-averaged electron flux measured during the recovery phase, to the mean pre-storm electron flux. A storm is considered an effective one if its ratio exceeds 2. We compare behavior of Pi1 and Pc5 geomagnetic pulsations during effective and non-effective storms and find a tendency for a storm efficiency to be higher when the mid-latitude Pi1 pulsations are observed for a long time during the magnetic storm main phase. We note also that the prolonged powerful Pc5 pulsation activity during the recovery phase of a magnetic storm is the necessary condition for the storm effectiveness. To interpret the found dependences, we suggest that there are two prerequisites for generating relativistic electron populations during a storm: (1) the availability of seed electrons in the magnetosphere, and Pi1 emissions are indicators of the mid-energy electron interaction with the ionosphere and (2) acceleration of the seed electrons to MeV energies, and interaction of electrons with the MHD wave activity in the Pc5 range is one of the most probable mechanisms proposed in the literature for this purpose.     

The effect of heavy ions on the spectrum of oscillations of the magnetosphere

Some issues concerning the influence of multi-ion composition of plasma on the spectrum of ultralow frequency (ULF) oscillations in the magnetosphere are analyzed. Main emphasis is made on the effects that are perceptible by analyzing the results of observations of ULF oscillations. The resonator confining ion cyclotron waves in the equatorial zone high above the Earth is considered, as well as the near-equatorial waveguide existing under the plasmasphere arch and canalizing magnetosonic waves in the azimuth direction. It is shown that the very existence of the ion-cyclotron resonator would be impossible, if only one species of ions were contained in plasma. It is emphasized that the problem of excitation of magnetosonic waves with harmonics of the gyrofrequency of O⁺ needs further investigation. The effect of heavy ions on the spectrum of Alfvén oscillations of the magnetosphere is considered. Some arguments are presented giving evidence that existence of alpha-particles in the solar wind leads to an asymmetry of the spectrum of magnetosonic oscillations in front of the Earth’s bow shock. Anomalously large asymmetry is expected at immersion of the Earth into the “plasmasphere” of the flare-associated stream of solar plasma. The general conclusion is made that even a small admixture of heavy ions can have a substantial effect on the spectrum of ULF oscillations.