Shumann resonances and electromagnetic transparence in the atmosphere of Titan

Among the multiple questions that the CASSINI/HUYGENS mission tries to answer is the likelihood of electric discharges in Titan's atmosphere. The instruments “Huygens Atmospheric Structure Instrument” and “Radio and Plasma Wave Science” will probe the electromagnetic emissions during the Huygens descent and Cassini flybys, respectively. Although no lightning was observed during Voyager's encounters with Titan in 1980 and 1981, this does not exclude the existence of lightning phenomena. Recent investigations show that lightning discharges could occur in the lower atmosphere, such as the detection of methane condensation clouds in the troposphere and the theoretical prediction of an electric field that would be sufficient enough to cause lightning. We present a numerical model of Titan's atmosphere with the aim of calculating the resonance frequencies and the atmospheric transparency to electromagnetic waves. The detection and measurement of these resonances, Schumann frequencies, by the Huygens probe, would show the existence of electric activity connected with lightning discharges in the atmosphere. As it happens with the Schumann frequencies of Earth, losses associated with the electric conductivity will make these frequencies to be lower than the theoretically predicted, the fundamental one being located between 11 and 15 Hz. An analytical study shows that the strong losses associated with the high conductivity make it impossible that an electromagnetic wave generated near the surface with a frequency of 10 MHz or lower reaches the outer part of Titan's atmosphere. Therefore the detection of electromagnetic waves coming from Titan's lower atmosphere by the RPWS instrument is very unlikely.     

Investigation of magnetospheric processes with the use of a source of strong magnetic field in the ionosphere

More than 20 years ago V.P. Shabansky suggested that the magnetic system installed aboard the satellite, could be used as a physical instrument for studying the processes which occur in the near Earth space. The corresponding space scales of an artificial “magnetosphere”—“magnisphere”—are 10 m in the experiment with relatively small magnets in the ionosphere and 100 m in the solar wind. The corresponding similarity criteria are estimated. The possible scheme of the experiment with a superconducting magnet (magnetic moment 10⁵ A · m²) installed aboard the satellite is considered. The experimental complex includes a number of systems for measuring the fluxes of charged particles in a wide energy range, DC electric and magnetic fields, the electromagnetic fields in different frequency bands (from X-rays to radio). The scientific objectives are discussed in detail.     

On the origin of the high-latitude boundary layer

This paper presents a statistical study of the high-latitude boundary layer (HLBL) performed on 53 Interball-1 magnetopause crossings. In the study we verify if antiparallel merging is the main source of HLBL formation when the IMF is nearly horizontal. To provide such a study we designed a new coordinate system which allowed us to analyze HLBL under varied interplanetary conditions. This coordinate system floats over the dayside magnetopause following the changes in the instant location of the reconnection site. Despite very different interplanetary conditions, the observed HLBL plasma regimes manifest systematic behavior in the “reconnection” frame of reference. We explain the observed pattern in terms of sporadic patchy reconnection in the high magnetic shear region of the magnetopause.     

Ion signatures of reconnection at the magnetopause

For a rotational MHD discontinuity the bulk flow is Alfvénic in the de Hoffmann-Teller frame. Using AMPTE/IRM data, we present ion distribution functions during three crossings of the dayside low-latitude magnetopause. For these crossings a well defined de Hoffmann-Teller frame can be found, but the field-aligned bulk flow is always slower than the Alfvén speed. Nevertheless, we find signatures in the distribution functions that provide clear evidence for magnetic reconnection: solar wind ions reflected off the magnetopause, “D-shaped” solar wind ion distributions in the boundary layer, and counterstreaming of solar wind ions and ionospheric ions in the boundary layer.     

Energetic neutron and gamma-ray spectra under the earth radiation belts according to “SALUTE-7”-“KOSMOS-1686” orbital complex and “CORONAS-i” satellite data

The spectra of neutrons >10 MeV and gamma-rays 1.5–100 MeV under the Earth Radiation Belts, restored from the data, obtained onboard orbital complex “SALUTE-7”-“KOSMOS-1686”, are presented. The spectra shapes are similar to those for albedo neutrons and gamma-rays, but absolute values of their fluxes (0.2 cm⁻² s⁻¹ for neutrons, 0.8 cm⁻² s⁻¹ for gamma-rays at the equator and 1.2 cm⁻² s⁻¹, 1.9 cm⁻² s⁻¹, accordingly, at L=1.9) are several times as large. It is possibly explained by the fact that most of the detected particles were produced by the cosmic ray interactions with the orbital complex matter. Neutron and gamma-ray fluxes obtained from “CORONAS-I” data are near those for albedo particles.     

Re-entry of orbital debris observed by Chung-Li VHF radar with MEDAC

MEDAC (Meteor Echo Detection and Collection) system, a product of University of Colorado, has become part of Chung-Li VHF facilities since July 12, 1989. MEDAC is installed to observe the mesospheric winds from Doppler echos returned by meteor trails in the upper atmosphere. However, the time variations in the in-phase and quadrature components of the signals can be used to derive the time history of the meteor trail formation. The meteor flight speed in the atmosphere is hence deduced. Preliminary analysis of some data taken from July 12 to July 17 of 1989 indicates that there are some “meteor” trails that could have been produced by the reentry of orbital debris into the atmosphere. The criteria of the flight speed and the ionization height are used for selecting an orbital debris trail from pools of “meteor” trails. The relative flux intensities between the reentry orbital debris flux as tentatively identified in this paper and the meteor flux is about 1 to 100.     

Analysis of the nucleus and circumnuclear area of comet Halley with the “I.K.S.” infrared sounder from the “Vega” flyby probes

The “Vega” Soviet flyby probes to comet Halley will carry a French infrared sounder, called “I.K.S.”. In order to assess its observing capabilities, a theoretical model of the comet infrared emission was constructed. We show how the experiment results will be used to derive the nucleus size and radiative properties, and to study the distribution of gas and dust in the inner coma and circumnuclear area. A preliminary discussion is made of the relevance of the data in instances where the cometary phenomena would be more complex than assumed in the model.     

Transient effects of solar energetic particle flux enhancements on the inner magnetosphere of the earth

In one type of space weather, the sun emits intermittent enhancements of solar energetic particle (SEP) fluxes. A fraction of these fluxes that reach the envelope of geospace can be injected into the magnetospheric particle confinement region after transiting the geomagnetic tail domain, the polar cleft/cusp region, or directly through the front side magnetopause. Common for these processes is that they provide inward diffusive “leakage” whenever the immediate external flux environment is more intense than in the outer trapping region. Conversely, following injection events outward leakage can also occur whereby the confinement region becomes a source of Magnetosheath particles. Numerical modeling has been carried out to investigate the effects on the ambient fluxes in the Earth's radiation belts from this effect.     

Mini-belt as a fine spatial structure of the outer radiation belt in quiet and disturbed conditions

Electron flux data from LANL geostationary spacecrafts were statistically treated and ordered in a special magnetic coordinate system (effective L-coordinate and MLT). The data treating procedure allowed to obtain the dynamics of quasi-trapped electrons of different energies on effective L-shells ranging from 6.6 to 7.0. It was found that in quiet conditions a stable fine spatial structure of quasi-trapped electrons exists with maximum of fluxes near L = 6.78 and MLT=12. This structure may be looked at as an asymmetrical “mini-belt”. The position of the maximum depends on electron energy and changes with magnetic activity. The dynamics of this mini-belt for both quiet and disturbed periods is illustrated and discussed. During isolated magnetic storms the mini-belt maximum shifts in a regular manner outward and inward; a diffusion wave of quasi-trapped particles propagates from outside of the geostationary orbit and serves as a source of new particles for the mini-belt. The azimuthal geometry of this diffusion wave extracted from experimental data is illustrated. The possible role of the “mini-belt” is discussed in relation with well-known “anomalous” dynamics of the inner radiation belt.     

On the non-occurrence of Type I X-ray bursts from the black hole candidates

It has been justifiably questioned if the black hole candidates (BHCs) have “hard surface” why Type I X-ray bursts are not seen from them [Narayan, R., Black holes in astrophysics, New J. Phys, 7, 199–218, 2005]. It is pointed out that a “physical surface” need not always be “hard” and could be “gaseous” in case the compact object is sufficiently hot [Mitra, A., The day of the reckoning: the value of the integration constant in the vacuum Schwarzschild solution, physics/0504076, p1–p6, 2005; Mitra, A., BHs or ECOs: A review of 90 years of misconceptions, in: Focus on Black Holes Research, Nova Science Pub., NY, p1–p94, 2005]. Even if a “hard surface” would be there, presence of strong intrinsic magnetic field could inhibit Type I X-ray burst from a compact object as is the case for Her X-1. Thus, non-occurrence of Type I bursts actually rules out those alternatives of BHs which are either non-magnetized or cold and, hence, is no evidence for existence of Event Horizons (EHs). On the other hand, from the first principle, we again show that the BHCs being uncharged and having finite masses cannot be BHs, because uncharged BHs have a unique mass M = 0. Thus the previous results that the so-called BHCs are actually extremely hot, ultramagnetized, Magnetospheric Eternally Collapsing Objects (ECOs) [Robertson, S., Leiter, D., Evidence for intrinsic magnetic moment in black hole candidates, Astrophys. J., 565, 447–451, (astro-ph/0102381), 2002 ; Robertson, S., Leiter, D., MECO model of galactic black hole candidates and active galactic nuclei, in: New Developments in Black Hole Research, Nova Science Pub., NY, p1–p44, astro-ph/0602453, 2005] rather than anything else get reconfirmed by non-occurrence of Type I X-ray bursts in BHCs.     

Space radiation quality factor investigations with “NAUSICAA”-device on board the “MIR” space station

The estimation of radiation quality factor in space flights is a serious problem of space dosimetry. The solution of this problem is based on LET-spectra measurements. The “NAUSICAA”-device installed on the “MIR” station has a detector with a large geometric factor, that gives the possibility of measuring LET-spectra with sufficient statistic in relatively short time interval and hence the corresponding Q. LET-spectra are accumulated through 24 hour periods and equivalent dose (H), absorbed dose (D), quality factor and flux (F) are measured every 10 minutes. The obtained data permit the estimate of the diurnal Q and Q in South Atlantic Anomaly. These values vary in the range of 1.4 – 2.2. The analysis of these values including their comparison with the calculated results is given in this paper.     

Experimental investigations of quasistable radiation belts formed after solar proton events in September–October 1989 and March 1991 based on measurements made by “Liulin” dosimeter-radiometer on board the “MIR” space station

Since 1988 high sensitivity dosimeter-radiometer “Liulin” has been installed on board the MIR space station. Device measured absorbed dose rate and flux of penetrating particles. Results of measurements showed that after powerful solar proton events (SPE) September–October, 1989 and March, 1991 additional quasistable radiation belts were formed in the near earth space within the interval L=1.8−3.0. These “new” belts were observed as an additional maximums in flux (and sometimes dose) channels when crossing the SAA region. “New” belts were quasi stable and existed at least several months, decaying slightly after SPE. Dose to flux ratio analysis showed that major components of these belts were energetic electrons and protons arising in connection with preceding SPEs.     

Updated TUS space fluorescence detector for study of UHECR

The TUS (Tracking Ultra-violet Set up) space fluorescence detector has to be launched in 2010 as a separated platform in Foton (Bion) mission prepared by the Samara enterprise. This detector was designed for another satellite and the updated variant of the TUS detector for a new platform is presented. The data on UV glow of the atmosphere obtained in operation of one pixel of the TUS detector on board the Moscow State University “Universitetsky-Tatiana” satellite was taken into account in design of the updated TUS detector. The data on UV transient flashes registered in “Universitetsky-Tatiana” mission are of special interest. Electronics of the TUS detector able to select and register different types of UV events in the atmosphere is presented.     

近地环境的电状态

通过电过程的耦合是太阳对气象耦合影响的机制之一,本文扼要地综述了迄今为止人们对近地环境内电流和电场的观测结果以及在此基础上所建立的经验和理论模式;给出了在平均状况下和太阳活动下近地环境电性能的总概貌,重点在靠近地球表面的低层、中层大气区域;着重介绍了该区域内的大气电性能及其受太阳活动的调制.      

Modeling the (upper) solar atmosphere including the magnetic field

The atmosphere of the Sun is highly structured and dynamic in nature. From the photosphere and chromosphere into the transition region and the corona plasma-β changes from above to below one, i.e., while in the lower atmosphere the energy density of the plasma dominates, in the upper atmosphere the magnetic field plays the governing role – one might speak of a “magnetic transition”. Therefore the dynamics of the overshooting convection in the photosphere, the granulation, is shuffling the magnetic field around in the photosphere. This leads not only to a (re-)structuring of the magnetic field in the upper atmosphere, but induces also the dynamic reaction of the coronal plasma, e.g., due to reconnection events. Therefore the (complex) structure and the interaction of various magnetic patches is crucial to understand the structure, dynamics and heating of coronal plasma as well as its acceleration into the solar wind.

The present article will emphasize the need for three-dimensional modeling accounting for the complexity of the solar atmosphere to understand these processes. Some advances on 3D modeling of the upper solar atmosphere in magnetically closed as well as open regions will be presented together with diagnostic tools to compare these models to observations. This highlights the recent success of these models which in many respects closely match the observations.     

Remote sensing of the ring current using energetic neutral atoms

Energetic neutral atom (ENA) images of the storm-time ring current obtained from the ISEE-1 spacecraft provide information for a “zero-order” global model of the energetic ion distribution. With the assumption of isotropic pressure and magnetostatic, non-convective pressure balance, the global system of electrical currents driven by the ion pressure can be calculated using Euler potentials for the divergenceless current density. Radial pressure gradients drive azimuthal currents, and azimuthal pressure gradients drive radial currents. The radial currents cause current lines in the inner magnetosphere to close in the ionosphere, forming a “partial” ring current. The intensities and locations of these field-aligned currents driven into and out of the ionosphere resemble those of the observed Region 2 current system, but not all observed properties of the Region 2 system are reproduced by the “zero-order” model.     

On the stereoselective aminoacylation of RNA

Aminoacylation of the “internal” 2′-hydroxyl groups of poly(A) with the imidazolide of racemic DL-leucine resulted in the formation of an enantiomeric excess of the D-ester, whereas aminoacylation with the imidazolide of racemic N-3,5-dinitrobenzoyl-DL-leucine gave an enantiomeric excess of the L-ester. Comparison of these results with those obtained earlier for alanine shows that the larger side chain tends to favor the formation of the D-ester. High resolution proton magnetic resonance spectroscopy was performed on the D- and L-alanyl “internal” 2′-esters of 3′,5′-ApA. The resonance of the side chain methyl group of the D-ester is upfield from that of the L-ester, and the separation of the peaks increases with a decrease in temperature.     

Generation mechanisms of the ELF-ULF waves related to the flux transfer events

Satellite observations near the magnetopause and within the magnetosheath revealed the existence of some structures characterised by specific magnetic field and plasma signatures. They have been called “Flux Transfer Events”. One of the models of FTEs is a reconnected fluxtube, extending from the inner magnetosphere into the magnetosheath. ELF-ULF waves are often observed in together with other FTE's signatures. Wideband emissions are associated with the boundaries of FTEs with characteristic maxima at lower hybrid and ion-cyclotron frequencies. They provide a tool for better timing of the events. These emissions might also be related to the reconnection process. Observations of FTE's by Prognoz-8 satellite are presented in our paper. Wave signatures of the FTEs are described. Various mechanisms of generation of the emissions by instabilities depending on local plasma conditions are discussed along with non-local aspects of such waves. Numerical solutions of the dispersion equation for the typical conditions in FTEs are presented. Possible relation of these waves to the reconnection process are discussed.     

An investigation of the spatial variations of the energetic trapped electrons at low altitudes

We have analyzed the trapped electron data (0.19–3.2 MeV) taken by the Japanese OHZORA satellite operated at 350–850 km altitude in polar orbit during 1984–1987 near solar minimum. The electron observations reveal all the global attributes of the quiet-time electron radiation belts, such as the South Atlantic Anomaly, the electron “slot”, and the outer radiation belt regions. The electron data are in general agreement with the NASA AE-8 electron model, but there are differences, particularly with respect to distinctive local-time variations in the slot region. In this paper, we present results from analyses of variations of the electron pitch angle distributions with local time, L-shell and altitude.     

Outstanding issues in understanding the dynamics of the inner plasma sheet and ring current during storms and substorms

The paper deals with five selected issues of the dynamical coupling of the near-Earth plasma sheet and magnetosphere, (1) substorm initiation, (2) dipolarization, (3) pressure release of the outer magnetosphere via the auroral energy conversion process, (4) magnetization of the very high beta plasma assembling at the inner edge of the tail, and (5) penetration of energetic particles into the ring current below L 4. One outstanding and strongly debated subject is not discussed here, the origin of the substorm current wedge. The main conclusions (or personal preferences) are: (1) the substorm is initiated by formation of a near-Earth neutral line; (2) dipolarization occurs through magnetic flux transport by the earthward reconnection flow and not by current diffusion; (3) the auroral energy conversion process, the “auroral pressure valve”, contributes substantially to the pressure release during the substorms; (4) high beta ( 10) plasma breaks up into smaller scale blobs under slow magnetization; and (5) deep and prolonged penetration of hot plasma sheet plasma into the middle magnetosphere produces currents and electric fields which lead to the growth of the storm-time ring current.