Shock–Acoustic Waves Generated during Rocket Launches and Earthquakes

Shock–acoustic waves generated during rocket launches and earthquakes are investigated by a method developed earlier for processing data from a global network of receivers of the GPS navigation system. Disturbances of the total electron content in the ionosphere accompanying the launches of the Proton, Soyuz, and Space Shuttle space vehicles from the Baikonur cosmodrome and Kennedy Space Center launch site in 1998–2000, as well as the earthquakes in Turkey on August 17 and November 12, 1999, were analyzed. It was shown that, regardless of the source type, the impulsive disturbance has the character of an N-wave with a period of 200–360 s and an amplitude exceeding background fluctuations under moderate geomagnetic conditions by a factor of 2–5 as a minimum. The elevation angle of the disturbance wave vector varies from 25° to 65°, and the phase velocity (900–1200 m/s) approaches the speed of sound at heights of the ionospheric F-region maximum. The source location corresponds to a segment of the booster trajectories at a distance of no less than 500–1000 km from the start position and to a flight altitude of no less than 100 km. In the case of earthquakes the source location approximately coincides with the epicenter.     

Simultaneous Response of the Mid-Latitude Ionosphere to a Sudden Commencement of Strong Magnetic Storms

Using the new technology of global GPS detection of ionospheric disturbances (GLOBDET), it is found that a sharp increase of the time derivative of the magnetic field strength during magnetic storms is accompanied by a simultaneous decrease of the mid-latitude total electron content (TEC) over the entire dayside of the globe. The corresponding negative correlation coefficient is no less than 0.8, and the delay relative to the sudden commencement of magnetic storm is about 3–10 min. The effect is especially clearly pronounced for magnetic storms with sudden commencements (SSC). The analysis is carried out for a set of 90 to 300 GPS stations for 10 days (January 6 and April 23, 1998; April 6, June 8, July 13, 14, and 15, 2000; March 31, April 4 and 11, 2001) with various levels of geomagnetic activity (D _st and K _p varied from –6 to –295 nT and from 0 to 9, respectively). The amplitude of the response in the total electron content for the events considered was 0.1–0.4 × 10¹⁶ m^–2 (which is a deviation of 0.2–2.6% from the TEC background value). The velocity of the disturbance motion from the dayside to the nightside was about 10–20 km/s. The results obtained agree with the data of ionospheric parameter measurements conducted earlier by methods with high temporal resolution.     

Estimates of disturbances of space vehicle orbits in the upper ionosphere prior to strong earthquakes

Estimates of drag characteristics of the space vehicles with orbit heights of 450–540 and 700–900 km before and after strong (with a magnitude M ≥ 6.5) crust earthquakes of 2000–2006 are presented. The method of estimation of seismic orbital effects is presented using as an example the small Mozhaets-4 spacecraft. Two weeks prior to earthquakes, variations in the drag of low-orbital spacecraft increase. 3–6 days prior to strong crust earthquakes with epicenters on the land, the drag of low-orbit spacecraft in the upper atmosphere increases. The effect of increased viscosity of the neutral component of the atmosphere at spacecraft heights 3–6 days prior to strong crust earthquakes is consistent with the results of studies of disturbances in the ionization density variations in the ionospheric F region prior to earthquakes. No anomalies are found in the day of the earthquake. In the future, it is proposed to use elements of space debris for diagnostics of seismic orbital effects and disturbances of the upper atmosphere.     

Statistical study of interplanetary condition effect on geomagnetic storms: 2. Variations of parameters

We investigate the behavior of mean values of the solar wind’s and interplanetary magnetic field’s (IMF) parameters and their absolute and relative variations during the magnetic storms generated by various types of the solar wind. In this paper, which is a continuation of paper [1], we, on the basis of the OMNI data archive for the period of 1976–2000, have analyzed 798 geomagnetic storms with D _st ≤ −50 nT and their interplanetary sources: corotating interaction regions CIR, compression regions Sheath before the interplanetary CMEs; magnetic clouds MC; “Pistons” Ejecta, and an uncertain type of a source. For the analysis the double superposed epoch analysis method was used, in which the instants of the magnetic storm onset and the minimum of the D _st index were taken as reference times. It is shown that the set of interplanetary sources of magnetic storms can be sub-divided into two basic groups according to their slowly and fast varying characteristics: (1) ICME (MC and Ejecta) and (2) CIR and Sheath. The mean values, the absolute and relative variations in MC and Ejecta for all parameters appeared to be either mean or lower than the mean value (the mean values of the electric field E _y and of the B _z component of IMF are higher in absolute value), while in CIR and Sheath they are higher than the mean value. High values of the relative density variation sN/〈N〉 are observed in MC. At the same time, the high values for relative variations of the velocity, B _z component, and IMF magnitude are observed in Sheath and CIR. No noticeable distinctions in the relationships between considered parameters for moderate and strong magnetic storms were observed.     

Stable spatial orbits around collinear libration points

A technique of generation of spatial periodic solutions to the restricted circular three-body problem from periodic orbits of the planar problem has been used for the families of orbits around collinear libration points L ₁ and L ₂. Developing the families obtained at the 1: 1 resonance, we have obtained stable solutions both in the Earth-Moon system and in the Sun-Earth system. Of course, the term “around the libration point” is rather conventional; the obtained orbits become more similar to the orbits around the smaller attracting body. The further development of the family of orbits “around” the libration point L ₂ in the Sun-Earth system made it possible to find the orbits satisfying the new, much more rigorous constraints on cooling the spacecraft of the Millimetron project.     

Statistical analysis of turbulence in the foreshock region and in the Earth’s magnetosheath

Statistical properties of magnetic field and plasma flux fluctuations outside the Earth’s magnetosphere are studied on various time scales based on the INTERBALL-1 satellite data. The analysis of “rough” turbulence characteristics has shown that turbulence properties in various parts of the magnetosheath are distinct. The spectral density of the magnetic field undergoes a break at a frequency of ∼0.5 Hz. As a more “fine” characteristic of the fluctuations on various time scales, changes in the shape and parameters of the probability density function were studied. The analysis of the height of a maximum of the probability density function P(0) and of the kurtosis values have shown the presence of two asymptotic modes of P(0), which are characterized by different power laws. The critical scale, on which the properties of P(0) change, corresponds, presumably, to the scales of the Larmor radius of ions. Based on the results of studying structural functions of various orders, the conclusion is drawn that small-scale turbulence in the foreshock and magnetosheath is described by different phenomenological models.     

Activation of the tail open part during the magnetospheric storm

In each polar cap (PC) we mark out “old PC” observed during quiet time before the event under consideration, and “new PC” that emerges during the substorm framing the old one and expanding the PC total area. Old and new PCs are the areas for the magnetosphere old and new tail lobes, respectively. The new lobe variable magnetic flux Ψ₁ is usually assumed to be active, i.e. it provides the electromagnetic energy flux (Poynting flux) ɛ′ transport from solar wind (SW) into the magnetosphere. The old lobe magnetic flux Ψ₂ is supposed to be passive, i.e. it remains constant during the disturbance and does not participate in the transporting process which would mean the old PC electric field absolute screening from the convection electric field created by the magnetopause reconnection. In fact, screening is observed, but far from absolute. We suggest a model of screening and determine its quantitative characteristics in the selected superstorm. The coefficient of a screening is the β = Ψ₂/Ψ₀₂, where Ψ₀₂ = const is open magnetic flux through the old PC measured prior to the substorm, and Ψ₂ is variable magnetic flux through the same area measured during the substorm. We consider three various regimes of disturbance. In each, the coefficient β decreased during the loading phase and increased at the unloading phase, but the rates and amplitudes of variations exhibited a strong dependence on the regime. We interpreted decrease in β as a result of involving the old PC magnetic flux Ψ₂, which was considered to be constant earlier, in the Poynting flux ɛ′ transport process from solar wind into the magnetosphere. Transport process weakening at the subsequent unloading phase creates increase in β. Estimates showed that coefficient β during each regime and the computed Poynting flux ɛ′ varied manifolds. In general, unlike the existing substorm conception, the new scenario describes an unknown earlier of tail lobe activation process during a substorm growth phase that effectively increases the accumulated tail energy for the expansion and recovery phases.     

Plasma Jet Motion Across the Geomagnetic Field in the “North Star” Active Geophysical Experiment

The active geophysical rocket experiment North Star was carried out in the auroral ionosphere on January 22, 1999, at the Poker Flat Research Range (Alaska, USA) using the American research rocket Black Brant XII with explosive plasma generators on board. Separable modules with scientific equipment were located at distances of from 170 to 1595 m from the plasma source. The experiment continued the series of the Russian–American joint experiments started by the Fluxus experiment in 1997. Two injections of aluminum plasma across the magnetic field were conducted in the North Star experiment. They were different, since in the first injection a neutral gas cloud was formed in order to increase the plasma ionization due to the interaction of neutrals of the jet and cloud. The first and second injections were conducted at heights of 360 and 280 km, respectively. The measurements have shown that the charged particle density was two orders of magnitude higher in the experiment with the gas release. The magnetic field in the first injection was completely expelled by the dense plasma of the jet. The displacement of the magnetic field in the second injection was negligible. The plasma jet velocity in both injections decreased gradually due to its interaction with the geomagnetic field. One of the most interesting results of the experiment was the conservation of high plasma density during the propagation of the divergent jet to considerable distances. This fact can be explained by the action of the critical ionization velocity mechanism.     

Characteristics of thermal ion outflows in the polar cap according to data of the <Emphasis Type="Italic">Interball-2</Emphasis> satellite

Characteristics of polar wind fluxes at a height of ∼20000 km measured by the Hyperboloid mass-spectrometer installed onboard the Interball-2 satellite are presented in the paper. The characteristics are presented for the upwelling flows of ionospheric ions H⁺, He⁺, and O⁺ from the sunlit polar cap in the period of solar activity minimum. Orbit segments with minimal precipitation of magnetospheric ions and electrons were preliminarily selected, and the measurements where the fluxes of ions coming from the cusp/cleft were excluded as carefully as possible. Thus, the densities, field-aligned velocities, and temperatures of ions in the regions where fluxes of polar wind could be detected with the maximal probability degree are presented in the paper. It is found that cases when only H⁺ ions are reaching the detector are with high probability the polar wind outflows. Their characteristics agree well with the Tube-7 hydrodynamic model and are as follows: n ≈ 1.5 cm⁻³, V _∥ ∼ 21 km/s; T _∥ = 3500 K, and T _⊥ = 2000 K. In cases when He⁺ and O⁺ ions are also detected, the temperatures are substantially higher than the model ones, and the measured field-aligned velocities of O⁺ fluxes are several times higher than the model ones. Moreover, it was revealed that the polar wind outflows are predominantly observed in the polar cap regions where the polar rain fluxes are very small.     

A New Population of the Cusp Suprathermal Protons Formed at Mid-Altitudes: INTERBALL-2 Measurements

A new population of dispersed suprathermal ions descending into the ionosphere is discovered in the cusp region from theINTERBALL-2 measurements at altitudes of 2–3R _E. The proton energies of the population are below the low energy cut-off of the main dispersed proton population of the magnetosheath origin, and its intensity and density are also much lower. For IMF B _z 2 nT the region of the population observations is located partly coincident with (or sometimes poleward from) the main proton population of the cusp proper. The pitch-angle velocity dispersion in the population during a 2-min satellite rotation manifests itself as a typical pitch-angle V together with a velocity dispersion due to poleward convection. The satellite passes chosen for the detailed analysis and modeling lay approximately along the cusp/cleft band from afternoon till prenoon MLT sectors, thus emphasizing the pitch-angle dispersion role with respect to the dispersion due to convection. This allows one to observe the suprathermal proton population during several tens of minutes over the MLT range of 3 h around noon, i.e., similarly to the MLT extension of the cusp proper. A remarkable space/time stability of this new population is due to its low velocity (tens of km/s) and/or velocity diffusion in the flux tubes of the cusp proper. We have performed both backward tracing of proton trajectories in the Tsyganenko-96 model, and kinetic modeling of the kinematic variations of the distribution function for protons along their way from the bi-Maxwellian source in the form of a heating wall till the satellite. The parameters of the model were adjusted to the observed energy–time spectrograms. They consistently indicate the origin of the descending suprathermal proton population at intermediate altitudes of 5R _E, i.e., within cusp flux tubes but well below the magnetopause. Some published measurements from the POLAR satellite in the cusp region at altitudes of 4–5R _E seem to be consistent with the supposition of crossing the source region of this population, variable in space and time (though these measurements were interpreted in a different manner).     

Development of auroral electrojets and low-latitude geomagnetic disturbances during strong magnetic storms on November 7–11, 2004

The influence of auroral electojets and solar wind parameters on variations in low-latitude geomagnetic disturbances and D _st during strong magnetic storms on November 7–8, 2004 with D _st ≈ −380 nT and on November 9–10, 2004 with D _st ≈ −300 nT is studied on the basis of global geomagnetic observations. It is found that the impulsive variations of the western electrojet intensity with a duration of Δt ≈ 1–2 h (probably, substorm disturbances) lead to positive low-latitude disturbances of ΔH at Φ′ ≈ 10°–30° and to disturbances of the same durations with an amplitude +ΔH ∼ 30–100 nT at latitudes of the polar cap (Φ′ ≈ 75°–80°). More durable (with Δt ≥ 10 h) convection electrojets whose centers are shifted to latitudes of ∼50°–55° in the process of storm development are the main cause of the increase in negative values of ΔH at low latitudes and D _st . It is shown that meridional dynamics of position of the center of electrojets and the equatorial boundary of the auroral oval is governed by variations (increase or decrease) in the intensity of negative values of the IMF B _z component. It is assumed that in these storms the intensification of the magnetospheric partially ring current closes the circuit to the ionosphere with the help of field-aligned currents at the equatorial boundary of the auroral oval is the main cause of the magnetic field depression at low latitudes.     

Ions with a Mass Number of Two in Mass-Spectrometric Experiments aboard Rockets and Satellites

Deuterium ions D⁺and doubly-charged helium ions He⁺⁺have the same mass-to- charge ratio (M/Z= 2) and are not distinguished by the mass-spectrometer. On the basis of analysis of published data, Interkosmos-24satellite data, and theoretical estimations, it is shown that in the ionosphere and plasmasphere the ion with a mass number of two is He⁺⁺and not D⁺, at least at altitudes of higher than 600–800 km. Arguments in favor of the validity of this assumption at lower altitudes are presented. Regularities of the dependence of the N(He⁺⁺)/N(He⁺) ratio on altitude, time of day, season, and solar activity are derived. It is found that in the daytime the N(He⁺⁺)/N(He⁺) ratio decreases with increasing solar activity. The seasonal dependence is most pronounced at nighttime in the altitude interval 1000–2000 km, where this ratio decreases in passing from winter to summer. Peculiarities of the latitude distribution of the absolute and relative values of the He⁺⁺concentration are found in the Interkosmos-24satellite data. On the basis of the same data, a strong longitude effect in the N(He⁺⁺) concentration occurring under certain heliogeophysical conditions is discovered, an effect amplitude attaining one order of magnitude on adjacent orbits. An interpretation of this effect is given.     

Determination of characteristic frequencies of elastic oscillations of the <Emphasis Type="Italic">International Space Station</Emphasis> construction

The results of investigating free oscillations of the International Space Station construction appearing during spacecraft docking and undocking are described. The study is carried out using the measurement data of the low-frequency MAMS accelerometer. Several intervals of measurements performed in 2005 and 2006 were chosen to be studied. For chosen intervals, only the data intervals corresponding to the process of free attenuation of the oscillations construction elements were analyzed. Characteristic frequencies of elastic oscillations of the station construction and attenuation coefficients corresponding to them are found. The comparative analysis of the results obtained for various docking ports (nodes) is carried out. The described study is performed as a part of the technical experiment “The ISS Environment” carried out onboard the station in accordance with the Russian program of scientific and engineering experiments.     

Statistical study of interplanetary condition effect on geomagnetic storms

Based on the archive OMNI data for the period 1976–2000 an analysis has been made of 798 geomagnetic storms with D _st < −50 nT and their interplanetary sources-large-scale types of the solar wind: CIR (145 magnetic storms), Sheath (96), magnetic clouds MC (62), and Ejecta (161). The remaining 334 magnetic storms have no well-defined sources. For the analysis, we applied the double method of superposed epoch analysis in which the instants of the magnetic storm beginning and minimum of D _st index are taken as reference times. The well-known fact that, independent of the interplanetary source type, the magnetic storm begins in 1–2 h after a southward turn of the IMF (B _z < 0) and both the end of the main phase of a storm and the beginning of its recovery phase are observed in 1–2 h after disappearance of the southward component of the IMF is confirmed. Also confirmed is the result obtained previously that the most efficient generation of magnetic storms is observed for Sheath before MC. On the average parameters B _z and E _y slightly vary between the beginning and end of the main phase of storms (minimum of D _st and D _st ^* indices), while D _st and D _st ^* indices decrease monotonically proportionally to integral of B _z and E _y over time. Such a behavior of the indices indicates that the used double method of superposed epoch analysis can be successfully applied in order to study dynamics of the parameters on the main phase of magnetic storms having different duration.     

Manifestations of sudden commencement of a severe magnetic storm of November 20, 2003, in generation of an SC pulse, <Emphasis Type="Italic">P</Emphasis><Subscript>SC</Subscript> pulsations,and spatial modulation of the auroral brightness

The results of investigation of the geomagnetic and auroral response to the commencement of a severe magnetic storm of November 20, 2003, are presented. It is established that the onset of SC led to the brightening of the auroral arc in the dusk sector for 2–3 min with its extent to the east with a velocity of 10–20 km/s and to displacement poleward with a velocity of 1.0 km/s. Furtheron, the fast auroral expansions of short duration (5 min) to the pole up to 2–4°were observed, repeating every 5–10 min during 40 min, which led to the spatial modulation of the brightness of the glow and to generation of P_SC pulsations with similar periods of oscillations. The broadening of aurora poleward had a steplike character, with generation of new arcs poleward of previous ones 5 arcs per 1.5 min. The modulation of brightness of the glow and P_SC were observed against the background of intensification of a two-cell DP2 type current system and were accompanied by multiple turnings of the IMF B_z from south to north and back. It is assumed that the source of P_SC pulsations was a modulation of the intensity of the DP2 ionosphere currents as a result of variations of the magnetosphere convection level.Translated from Kosmicheskie Issledovaniya, Vol. 42, No. 6, 2004, pp. 608–615.Original Russian Text Copyright © 2004 by Baishev, Borisov, Velichko, Solovyev, Yumoto.     

variations of the atmospheric chemical composition in the earths’s polar regions after solar proton flare on July 14, 2000 (photochemical simulation)

Altitude—temporal cross-sections q(z, t) of atmospheric ionization rates by solar protons above the polar regions were calculated using the GOES-10 satellite data on solar proton fluxes for the period of solar proton flare (SPF) on July 14, 2000. The values of q(z, t) were used further in calculations of variations of the atmospheric chemical composition during the flare in the northern and southern polar regions (70°N and 70°S) by two different 1D photochemical models of the atmosphere (neutral and charged components). The calculation results have shown considerable variation of the ozone content after SPF: a decrease of [O3] was about 80% at altitudes of 65–75 km above northern and 25% in the layer of 55–65 km above the southern polar region. Such decrease of the ozone content is a result of reactions with [NO] and [OH] whose concentrations have grown substantially during SPF. According to calculations, the increase of electron concentration during SPF has reached 3–4 orders of magnitude at altitudes of 50–80 km. A comparison of the calculation results with the observational data on [NO], [NO2], and [O3] from the UARS and HALOE satellites for 70°N have shown a good qualitative correspondence, however, for variations of nitric oxides there are quantitative discrepancies.     

INTERBALL-1 Observations of the Kilometric “Continuum” of the Earth's Magnetosphere

The electromagnetic radio-frequency emission of the inner region of the Earth's plasmasphere discovered recently by the GEOTAIL satellite [4] and referred to as the kilometric continuum was observed by the INTERBALL-1 satellite (1995–2000) in the 100–500 kHz band in the AKR-X experiment. During a period of low solar activity (1995–1997), this continuum was found leaving the inner plasmasphere at geocentric distances of 2–4R _E as isolated pencil-like (1°–6°) beams located in the magnetic equator plane. During a time of high solar activity (1999–2000), the occurrence of the emission was extremely rare (it was observed only at a considerable fall of this activity). If detected, at the same geocentric distances (2–4R _E) the continuum demonstrated a strongly variable and perturbed character, as well as a considerably larger extension of the beam over the geomagnetic latitude (10°–20° and more). In addition, quasi-periodic (QP) signals, similar to the observed QP emissions of Jupiter, were sometimes detected in this period. The probable nature of the observed features of the kilometric continuum is briefly discussed.     

On the asteroid hazard

The concept of “space patrol” is considered, aimed at discovering and cataloging the majority of celestial bodies that constitute a menace for the Earth [1, 2]. The scheme of “optical barrier” formed by telescopes of the space patrol is analyzed, requirements to the observation system are formulated, and some schemes of sighting the optical barrier region are suggested (for reliable detection of the celestial bodies approaching the Earth and for determination of their orbits). A comparison is made of capabilities of electro-jet engines and traditional chemical engines for arrangement of patrol spacecraft constellation in the Earth’s orbit.     

Storm deviations of the geomagnetic trap core from dipole configuration deduced from data on relativistic electrons

Satellite data on the position of maximum L _m of the belt of relativistic electrons during strong storms, obtained at low altitudes (∼500 km) and at high altitudes (near the geomagnetic equator plane), are compared (L is the McIlwain parameter). Both at low and high altitudes the maximum of the storm belt of relativistic electrons is formed on the outer edge of the ring current. It is shown that the geomagnetic field can substantially deviate from dipole configuration not only at the geomagnetic trap periphery, but at its core as well (at L ∼ 2.5–3.5), and these deviations are nonlinear. Simultaneous measurements of the fluxes of relativistic electrons at low and high altitudes can serve for estimation of the real shape of magnetic field lines at L < 4 during geomagnetic disturbances.     

Some features of solar cosmic ray penetration into the Earth’s magnetosphere

We compared fluxes of the 1–100 MeV solar energetic particles (SEP) measured in the interplanetary medium (ACE) and in the magnetosphere (Universitetsky-Tatiana, POES—in polar caps, and GOES-11—at geosynchronous orbit) during several SEP events of 2005–2006. Peak intensities of the SEP fluxes inside and outside the magnetosphere were compared for each event. It is shown that observed inside-outside difference depends mainly on direction of interplanetary magnetic field (IMF), on degree of the SEP anisotropy (pitch-angle distribution) in IMF, and on distance of the dayside magnetopause from the Earth.