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Z. Němeček

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National Scientific and Technical Research Council

University of Oxford

michele ciavarella

Politecnico di Bari

Juan Carlos Moreno Garcia

Centre National de la Recherche Scientifique / French National Centre for Scientific Research

Francesca Stavrakopoulou

University of Exeter

Saint-Petersburg Stieglitz State Academy of Art and Design

University of Sarajevo

Harijono Djojodihardjo

Institut Teknologi Bandung

Bilkent University

Alexander Avramov

Massachusetts Institute of Technology (MIT)

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Papers by Z. Němeček

Correlation length of magnetosheath fluctuations: Cluster statistics

Annales Geophysicae, 2008

Magnetosheath parameters are usually described by gasdynamic or magnetohydrodynamic (MHD) models ... more Magnetosheath parameters are usually described by gasdynamic or magnetohydrodynamic (MHD) models but these models cannot account for one of the most important sources of magnetosheath fluctuations -the foreshock. Earlier statistical processing of a large amount of magnetosheath observations has shown that the magnetosheath magnetic field and plasma flow fluctuations downstream of the quasiparallel shock are much larger than those at the opposite flank. These studies were based on the observations of a single spacecraft and thus they could not provide full information on propagation of the fluctuations through the magnetosheath. We present the results of a statistical survey of the magnetosheath magnetic field fluctuations using two years of Cluster observations. We discuss the dependence of the crosscorrelation coefficients between different spacecraft pairs on the orientation of the separation vector with respect to the average magnetic field and plasma flow vectors and other parameters. We have found that the correlation length does not exceed ∼1 R E in the analyzed frequency range (0.001-0.125 Hz) and does not depend significantly on the magnetic field or plasma flow direction. A close connection of crosscorrelation coefficients computed in the magnetosheath with the cross-correlation coefficients between a solar wind monitor and a magnetosheath spacecraft suggests that solar wind structures persist on the background of magnetosheath fluctuations.

Influence of the Electric Field on Secondary Electron Emission Yield

AIP Conference Proceedings, 2008

We present results of the investigation of secondary electron emission from spherical amorphous c... more We present results of the investigation of secondary electron emission from spherical amorphous carbon grains of 3 to 6 micrometers in diameter affected by a high surface field. In our experiment, we have applied a technique based on levitation of a single charged grain in the quadrupole trap. This grain was charged by an electron beam with an energy tunable up to 10 keV. During this process, the grain charge is continuously monitored. If the grain is charged by an appropriate energetic electron beam, its charge (and the corresponding surface potential and surface electric field) is set to a value when the yield of secondary emission is equal to unity (crossover point). The investigations reveal that the energy corresponding to the crossover point changes proportionally to the grain potential. This effect was attributed to an increase of the yield of secondary emission due to a large electric field at the grain surface. Moreover, the measurement of the net current on the grain induced by electrons with the energy between first and second crossover points indicates similar increase of the yield.

Numerical MHD modeling of propagation of interplanetary shock through the magnetosheath

Journal of Geophysical Research, 2006

Propagation of an interplanetary (IP) shock through the bow shock and magnetosheath is studied us... more Propagation of an interplanetary (IP) shock through the bow shock and magnetosheath is studied using numerical results of a three-dimensional MHD model of the magnetosheath. According to already published theoretical studies, a fast forward shock passing through the bow shock would generate a train of new discontinuities including a slow expansion wave, a contact discontinuity, and a slow reversed shock.

Two-point measurement of hot plasma structures in the magnetotail lobes

Advances in Space Research, 1997

ABSTRACT

Two point observation of magnetopause motion: The INTERBALL project

Advances in Space Research, 1997

On August 3, 1995, two satellites of the INTERBALL mission were launched into a highly elliptical... more On August 3, 1995, two satellites of the INTERBALL mission were launched into a highly elliptical dawnside orbit with an apogee near 200 000 km and a perigee of 800 km. The distance separating the satellites varies from one to several thousand km. Both satellites carry sets of Faraday cups which cover a spatial angle approaching nearly 4~. The cups provide high resolution data (up to 16 Hz for the main satellite and 10 Hz for the subsatellite) which we supplement with magnetic field measurements and observations of the electron/ion energy and angular distributions. The configuration of both satellites allows us to determine small-scale variations of the magnetopause shape and position and to estimate the velocity of the magnetopause motion. A preliminary analysis of the data suggests that the nature of magnetopause motion depends significantly on the geomagnetic latitude. Wavy motion of the magnetopause boundaries seems to be preferred at the low-latitude boundary layer near the equatorial plane whereas a radial expansion/contraction seems to be most common at the high latitude plasma mantle.

Multipoint study of the solar wind: INTERBALL contribution to the topic

Advances in Space Research, 1997

The INTERBALL mission is predominantly dedicated to the magnetospheric study; nevertheless, simul... more The INTERBALL mission is predominantly dedicated to the magnetospheric study; nevertheless, simultaneous measurements of two similarly equipped satellites in the solar wind are of principal importance. The solar wind flow carries many inhomogeneities on different scales and the determination of their evolution or relative velocity of propagation requires a real multipoint measurement. The present paper describes briefly the scientific payload of both INTERBALL satellites from the point of view of the solar wind investigation but the main attention is paid to a comparative study of the disturbances in the solar wind flow on different spatial scales. The small scale is represented by two INTERBALL satellites separated by a few thousands of kin. The data set is completed by the WIND and IMP 8 plasma and magnetic field measurements for the study of the large-scale variations. INTRODUCTION ©1997 COSPAR. Published by Elsevier Science Ltd. During more than three decades of intensive experimental investigation of the solar wind our knowledge has progressed to the point that it can be claimed that its basic properties are well understood. The cold solar wind originates at the Sun surface, afterwards it is heated in the solar corona up to ,,~ 1.5 x 106 K and cooled down by the adiabatic expansion into interplanetary space to ~ 5 × 104 K observed near the Earth orbit. The observations indicate that the solar wind exhibits two distinct states, namely high speed streams characterized by remarkably smooth properties of the plasma and its composition on the one hand, and on the other, low speed streams whose properties are highly variable with considerable fluctuations in density and composition. These two states are connected with different regions on the Sun and they are relatively steady. The interaction of these two streams can lead to the generation of the shock (forward and reverse) pairs but these shocks can be observed at 1 AU only rarely (Burlaga et al., 1985).

Study of energetic particle anisotropy in weak and strong foreshocks

Advances in Space Research, 2006

In this paper, we continue our recent statistical studies of solar wind plasma fluctuations in th... more In this paper, we continue our recent statistical studies of solar wind plasma fluctuations in the EarthÕs foreshock and their relationship to measurements of energetic ion ($25, 50, 110 keV energy channels) fluxes under different solar wind and interplanetary magnetic field conditions, based on the INTERBALL-1 data obtained during 1995-2000. We discuss spatial and temporal characteristics of the energetic particle interaction with the foreshock plasma. We compare the intervals of upstream observations inside the foreshock of different strengths and relate plasma fluctuations to observed energetic particle pitch-angle distributions, anisotropy, and spectra at different distances to the bow shock. We discuss possible physical explanations of observed phenomena.

The shape and location of the high-latitude magnetopause

Advances in Space Research, 2005

Recent empirical magnetopause models are bi-variate with respect to both solar wind dynamic press... more Recent empirical magnetopause models are bi-variate with respect to both solar wind dynamic pressure and B Z component of the interplanetary magnetic field (IMF). Models use various functional forms to represent the shape and location of the magnetopause. Moreover, the models have different ranges of validity because, among other things, the data sets used for their development were usually different. A majority of these models were created for magnetopause crossings regardless of latitude. For the shape of the near-Earth high-latitude magnetopause, a new empirical model was published by Boardsen et al. [

Observations of the beam-plasma interaction during the APEX artificial electron beam emission

Advances in Space Research, 1998

During the APEX project the pulsed electron generator injected an intensive 8-kV electron beam at... more During the APEX project the pulsed electron generator injected an intensive 8-kV electron beam at different angles to the Earth's magnetic field. Multiangular electrostatic analyzers (PEAS spectrometer) registered the flux of electrons and ions in the energy range from 50 eV to 30 keV in two perpendicular planes. The satellite potential was balanced by a low energy Xenon plasma generator during the electron beam injection. The observation of the charged particle ~stribution was accompanied by the me~urement of the spacecraft potential by the floating probe. The energy spectrum of returning electrons exhibits a pronounced m~mum near 1 keV. The electron distribution is not gyrotropic and the energy and number flux of the main electron population decreases with pitch angle. These two observational facts suggest a space-limited perpendicular acceleration process. The accelerated electrons are observed from both sides of the satellite with respect to the magnetic field, so the process is not caused directly by interaction of the primary beam and the ambient plasma. 8198 COSPAR.

Some comments on the ion distribution function evolution in the quasiparallel shock

Advances in Space Research, 1991

ABSTRACT

Energetic proton spectra upstream of the bow shock from intershock project

Advances in Space Research, 1986

... References. 1. M. Scholer Geophys. Monograph 35 (1985), p. 287 AGU . 2. S. Fischer, K. Kudela... more

Instabilities of ion flow observed downstream of the Earth's bow shock

Advances in Space Research, 1986

The results presented were obtained from experiments with temporal resolution of 0.02 to 1.28 sec... more The results presented were obtained from experiments with temporal resolution of 0.02 to 1.28 sec that were carried out on board Prognoz 8 and 10 satellites. The following parameters and their changes after bow shock crossing have been taken into account: three dimensional drift velocity of total ion flow and ion temperature, and their fluctuations. The bow shock crossings under study involve both quasiparallel and quasiperpendicular strong shocks. In this paper, slow quasiperiodic fluctuations (10~÷ 10 Hz) in the downstream region are studied and the relation between these fluctuations and energy distribution function variations is discussed. Data from 13 selected shock wave crossings were used to investigate how the frequency of the oscillations depends on parameters characteristic for particular crossings.

Ion distribution function dynamics near the strong shock front (Project Intershock)

Advances in Space Research, 1986

The structure of the ion distribution function downstream of the bow shock front is analyzed with... more The structure of the ion distribution function downstream of the bow shock front is analyzed with the use of ion energy spectra measured with high temporal resolution (0.64 sec) by several differently oriented narrow-angle electrostatic analyzers onboard Prognoz-1O-Intercosmos satellite. Within a relatively extended region downstream of the shock the ion energy spectra exhibit fine structure consisting of several rapidly varying narrow peaks. Some evidence exists that the ion distribution function behind a strong quasiperpendicular shock consists of many narrow bunches. The electrostatic potential jump at the front of an oblique shock may occur in a distance of about 2 km.

Small-scale deformation of the bow shock

Advances in Space Research, 2008

The prediction of the bow shock location is a proof of our understanding of the processes governi... more The prediction of the bow shock location is a proof of our understanding of the processes governing the solar wind -- magnetosphere interaction However the models describing the bow shock location as a function of upstream parameters are based on a statistical processing of bow shock crossings observed by a single spacecraft Such crossings locate the bow shock in motion i e in non-equilibrium state and this fact can be a source of significant errors We have identified about 200 bow shock crossings observed by a closely 1 R E spaced INTERBALL-1 and MAGION-4 spacecraft and divided them into two groups The crossings in the first group were observed by one spacecraft only and the bow shock spent a long time between them In such cases the bow shock location is known with an error determined by the spacecraft separation along the bow shock normal and this location can be directly compared with the model The crossings in the second group were observed by both spacecraft We have estimated the bow shock speed and used it as a measure of a deviation of the observed bow shock location from the equilibrium position The results of our analysis are compared with predictions of bow shock models We have carefully analyzed all these crossings with motivation to find the source and way of the bow shock motion Our results suggest that often a small-scale deformation of the bow shock front is the most appropriate interpretation of observations

High and low frequency large amplitude variations of plasma and magnetic field in the magnetosheath: Radial profile and some features

Advances in Space Research, 2003

Variations in magnetosheath parameters, such as the ion flux and the magnitude of the magnetic fi... more Variations in magnetosheath parameters, such as the ion flux and the magnitude of the magnetic field, over a wide range of frequencies are much larger than the variations in the undisturbed solar wind. We present the results of a statistical investigation of magnetosheath variations using a large database of high time resolution (ls) INTERBALL-1 measurements and 1 min resolution IMP

Dynamics of the earth's bow shock position

Advances in Space Research, 1988

The paper deals with a study of the variations in the Earth's bow shock position based on simulta... more The paper deals with a study of the variations in the Earth's bow shock position based on simultaneous measurements by the Prognoz 10 and IMP-B satellites. Abrupt variations of solar wind parameters that have been registered by one apparatus are identified with shock crossings as seen by the other one. In the cases of solar windmagnetosheath crossings the velocity has been calculated also from the data obtained by only one apparatus (the one observing the crossing). Assuming the velocity of discontinuity propagation the same as the velocity of the solar wind, we can calculate the mean shock velocity from the time interval between these events. The shock model proposed by Formisano has been used for the calculations of the bow shock position. Experimental data indicates that the bow shock position depends on the magnetic field more strongly than is usually supposed /1/. On the other hand, the dependence on the solar wind dynamic pressure seems to be weaker than expected. Calculated velocities of the shock front motion lie in the interval of 2 to 60km/s. For small variations of the solar wind dynamic pressure the calculated velocity is roughly proportional to the magnitude of the variation.

Magnetosheath-cusp interface

Annales Geophysicae, 2004

We advance the achievements of Interball-1 and other contemporary missions in exploration of the ... more We advance the achievements of Interball-1 and other contemporary missions in exploration of the magnetosheath-cusp interface. Extensive discussion of published results is accompanied by presentation of new data from a case study and a comparison of those data within the broader context of three-year magnetopause (MP) crossings by Interball-1. Multi-spacecraft boundary layer studies reveal that in ∼80% of the cases the interaction of the magnetosheath (MSH) flow with the high latitude MP produces a layer containing strong nonlinear turbulence, called the turbulent boundary layer (TBL). The TBL contains wave trains with flows at approximately the Alfvén speed along field lines and "diamagnetic bubbles" with small magnetic fields inside. A comparison of the multi-point measurements obtained on 29 May 1996 with a global MHD model indicates that three types of populating processes should be operative:-large-scale (∼few R E) anti-parallel merging at sites remote from the cusp;-medium-scale (few thousand km) local TBL-merging of fields that are anti-parallel on average;

ROY—A multiscale magnetospheric mission

by M. Veselov, S. Savin, Z. Němeček, and S. Klimov

Planetary and Space Science, 2011

The scientific rationale of the ROY multi-satellite mission addresses multiscale investigations o... more

Multi-scale characteristics of the super-dense plasma streams at magnetospheric boundaries: fastest bridge for global and micro scales

by S. Savin and Z. Němeček

Energy concentration and re-distribution in the magnetospheric boundary layers

by S. Savin and Z. Němeček

Basing on comparison of the Cluster, Interball and solar wind (SW) data we discuss extremely dist... more Basing on comparison of the Cluster, Interball and solar wind (SW) data we discuss extremely disturbed magnetosheath (MSH) regions either closer to the bow shock (BS), or ahead of magnetopause (MP), which provide an evidence for unprecedented kinetic energy concentration either in spikes ('plasma jets' with the energy density up to several times above that of the unshocked SW), or

Correlation length of magnetosheath fluctuations: Cluster statistics

Annales Geophysicae, 2008

Magnetosheath parameters are usually described by gasdynamic or magnetohydrodynamic (MHD) models ... more Magnetosheath parameters are usually described by gasdynamic or magnetohydrodynamic (MHD) models but these models cannot account for one of the most important sources of magnetosheath fluctuations -the foreshock. Earlier statistical processing of a large amount of magnetosheath observations has shown that the magnetosheath magnetic field and plasma flow fluctuations downstream of the quasiparallel shock are much larger than those at the opposite flank. These studies were based on the observations of a single spacecraft and thus they could not provide full information on propagation of the fluctuations through the magnetosheath. We present the results of a statistical survey of the magnetosheath magnetic field fluctuations using two years of Cluster observations. We discuss the dependence of the crosscorrelation coefficients between different spacecraft pairs on the orientation of the separation vector with respect to the average magnetic field and plasma flow vectors and other parameters. We have found that the correlation length does not exceed ∼1 R E in the analyzed frequency range (0.001-0.125 Hz) and does not depend significantly on the magnetic field or plasma flow direction. A close connection of crosscorrelation coefficients computed in the magnetosheath with the cross-correlation coefficients between a solar wind monitor and a magnetosheath spacecraft suggests that solar wind structures persist on the background of magnetosheath fluctuations.

Influence of the Electric Field on Secondary Electron Emission Yield

AIP Conference Proceedings, 2008

We present results of the investigation of secondary electron emission from spherical amorphous c... more We present results of the investigation of secondary electron emission from spherical amorphous carbon grains of 3 to 6 micrometers in diameter affected by a high surface field. In our experiment, we have applied a technique based on levitation of a single charged grain in the quadrupole trap. This grain was charged by an electron beam with an energy tunable up to 10 keV. During this process, the grain charge is continuously monitored. If the grain is charged by an appropriate energetic electron beam, its charge (and the corresponding surface potential and surface electric field) is set to a value when the yield of secondary emission is equal to unity (crossover point). The investigations reveal that the energy corresponding to the crossover point changes proportionally to the grain potential. This effect was attributed to an increase of the yield of secondary emission due to a large electric field at the grain surface. Moreover, the measurement of the net current on the grain induced by electrons with the energy between first and second crossover points indicates similar increase of the yield.

Numerical MHD modeling of propagation of interplanetary shock through the magnetosheath

Journal of Geophysical Research, 2006

Propagation of an interplanetary (IP) shock through the bow shock and magnetosheath is studied us... more Propagation of an interplanetary (IP) shock through the bow shock and magnetosheath is studied using numerical results of a three-dimensional MHD model of the magnetosheath. According to already published theoretical studies, a fast forward shock passing through the bow shock would generate a train of new discontinuities including a slow expansion wave, a contact discontinuity, and a slow reversed shock.

Two-point measurement of hot plasma structures in the magnetotail lobes

Advances in Space Research, 1997

ABSTRACT

Two point observation of magnetopause motion: The INTERBALL project

Advances in Space Research, 1997

On August 3, 1995, two satellites of the INTERBALL mission were launched into a highly elliptical... more On August 3, 1995, two satellites of the INTERBALL mission were launched into a highly elliptical dawnside orbit with an apogee near 200 000 km and a perigee of 800 km. The distance separating the satellites varies from one to several thousand km. Both satellites carry sets of Faraday cups which cover a spatial angle approaching nearly 4~. The cups provide high resolution data (up to 16 Hz for the main satellite and 10 Hz for the subsatellite) which we supplement with magnetic field measurements and observations of the electron/ion energy and angular distributions. The configuration of both satellites allows us to determine small-scale variations of the magnetopause shape and position and to estimate the velocity of the magnetopause motion. A preliminary analysis of the data suggests that the nature of magnetopause motion depends significantly on the geomagnetic latitude. Wavy motion of the magnetopause boundaries seems to be preferred at the low-latitude boundary layer near the equatorial plane whereas a radial expansion/contraction seems to be most common at the high latitude plasma mantle.

Multipoint study of the solar wind: INTERBALL contribution to the topic

Advances in Space Research, 1997

The INTERBALL mission is predominantly dedicated to the magnetospheric study; nevertheless, simul... more The INTERBALL mission is predominantly dedicated to the magnetospheric study; nevertheless, simultaneous measurements of two similarly equipped satellites in the solar wind are of principal importance. The solar wind flow carries many inhomogeneities on different scales and the determination of their evolution or relative velocity of propagation requires a real multipoint measurement. The present paper describes briefly the scientific payload of both INTERBALL satellites from the point of view of the solar wind investigation but the main attention is paid to a comparative study of the disturbances in the solar wind flow on different spatial scales. The small scale is represented by two INTERBALL satellites separated by a few thousands of kin. The data set is completed by the WIND and IMP 8 plasma and magnetic field measurements for the study of the large-scale variations. INTRODUCTION ©1997 COSPAR. Published by Elsevier Science Ltd. During more than three decades of intensive experimental investigation of the solar wind our knowledge has progressed to the point that it can be claimed that its basic properties are well understood. The cold solar wind originates at the Sun surface, afterwards it is heated in the solar corona up to ,,~ 1.5 x 106 K and cooled down by the adiabatic expansion into interplanetary space to ~ 5 × 104 K observed near the Earth orbit. The observations indicate that the solar wind exhibits two distinct states, namely high speed streams characterized by remarkably smooth properties of the plasma and its composition on the one hand, and on the other, low speed streams whose properties are highly variable with considerable fluctuations in density and composition. These two states are connected with different regions on the Sun and they are relatively steady. The interaction of these two streams can lead to the generation of the shock (forward and reverse) pairs but these shocks can be observed at 1 AU only rarely (Burlaga et al., 1985).

Study of energetic particle anisotropy in weak and strong foreshocks

Advances in Space Research, 2006

In this paper, we continue our recent statistical studies of solar wind plasma fluctuations in th... more In this paper, we continue our recent statistical studies of solar wind plasma fluctuations in the EarthÕs foreshock and their relationship to measurements of energetic ion ($25, 50, 110 keV energy channels) fluxes under different solar wind and interplanetary magnetic field conditions, based on the INTERBALL-1 data obtained during 1995-2000. We discuss spatial and temporal characteristics of the energetic particle interaction with the foreshock plasma. We compare the intervals of upstream observations inside the foreshock of different strengths and relate plasma fluctuations to observed energetic particle pitch-angle distributions, anisotropy, and spectra at different distances to the bow shock. We discuss possible physical explanations of observed phenomena.

The shape and location of the high-latitude magnetopause

Advances in Space Research, 2005

Recent empirical magnetopause models are bi-variate with respect to both solar wind dynamic press... more Recent empirical magnetopause models are bi-variate with respect to both solar wind dynamic pressure and B Z component of the interplanetary magnetic field (IMF). Models use various functional forms to represent the shape and location of the magnetopause. Moreover, the models have different ranges of validity because, among other things, the data sets used for their development were usually different. A majority of these models were created for magnetopause crossings regardless of latitude. For the shape of the near-Earth high-latitude magnetopause, a new empirical model was published by Boardsen et al. [

Observations of the beam-plasma interaction during the APEX artificial electron beam emission

Advances in Space Research, 1998

During the APEX project the pulsed electron generator injected an intensive 8-kV electron beam at... more During the APEX project the pulsed electron generator injected an intensive 8-kV electron beam at different angles to the Earth's magnetic field. Multiangular electrostatic analyzers (PEAS spectrometer) registered the flux of electrons and ions in the energy range from 50 eV to 30 keV in two perpendicular planes. The satellite potential was balanced by a low energy Xenon plasma generator during the electron beam injection. The observation of the charged particle ~stribution was accompanied by the me~urement of the spacecraft potential by the floating probe. The energy spectrum of returning electrons exhibits a pronounced m~mum near 1 keV. The electron distribution is not gyrotropic and the energy and number flux of the main electron population decreases with pitch angle. These two observational facts suggest a space-limited perpendicular acceleration process. The accelerated electrons are observed from both sides of the satellite with respect to the magnetic field, so the process is not caused directly by interaction of the primary beam and the ambient plasma. 8198 COSPAR.

Some comments on the ion distribution function evolution in the quasiparallel shock

Advances in Space Research, 1991

ABSTRACT

Energetic proton spectra upstream of the bow shock from intershock project

Advances in Space Research, 1986

... References. 1. M. Scholer Geophys. Monograph 35 (1985), p. 287 AGU . 2. S. Fischer, K. Kudela... more

Instabilities of ion flow observed downstream of the Earth's bow shock

Advances in Space Research, 1986

The results presented were obtained from experiments with temporal resolution of 0.02 to 1.28 sec... more The results presented were obtained from experiments with temporal resolution of 0.02 to 1.28 sec that were carried out on board Prognoz 8 and 10 satellites. The following parameters and their changes after bow shock crossing have been taken into account: three dimensional drift velocity of total ion flow and ion temperature, and their fluctuations. The bow shock crossings under study involve both quasiparallel and quasiperpendicular strong shocks. In this paper, slow quasiperiodic fluctuations (10~÷ 10 Hz) in the downstream region are studied and the relation between these fluctuations and energy distribution function variations is discussed. Data from 13 selected shock wave crossings were used to investigate how the frequency of the oscillations depends on parameters characteristic for particular crossings.

Ion distribution function dynamics near the strong shock front (Project Intershock)

Advances in Space Research, 1986

The structure of the ion distribution function downstream of the bow shock front is analyzed with... more The structure of the ion distribution function downstream of the bow shock front is analyzed with the use of ion energy spectra measured with high temporal resolution (0.64 sec) by several differently oriented narrow-angle electrostatic analyzers onboard Prognoz-1O-Intercosmos satellite. Within a relatively extended region downstream of the shock the ion energy spectra exhibit fine structure consisting of several rapidly varying narrow peaks. Some evidence exists that the ion distribution function behind a strong quasiperpendicular shock consists of many narrow bunches. The electrostatic potential jump at the front of an oblique shock may occur in a distance of about 2 km.

Small-scale deformation of the bow shock

Advances in Space Research, 2008

The prediction of the bow shock location is a proof of our understanding of the processes governi... more The prediction of the bow shock location is a proof of our understanding of the processes governing the solar wind -- magnetosphere interaction However the models describing the bow shock location as a function of upstream parameters are based on a statistical processing of bow shock crossings observed by a single spacecraft Such crossings locate the bow shock in motion i e in non-equilibrium state and this fact can be a source of significant errors We have identified about 200 bow shock crossings observed by a closely 1 R E spaced INTERBALL-1 and MAGION-4 spacecraft and divided them into two groups The crossings in the first group were observed by one spacecraft only and the bow shock spent a long time between them In such cases the bow shock location is known with an error determined by the spacecraft separation along the bow shock normal and this location can be directly compared with the model The crossings in the second group were observed by both spacecraft We have estimated the bow shock speed and used it as a measure of a deviation of the observed bow shock location from the equilibrium position The results of our analysis are compared with predictions of bow shock models We have carefully analyzed all these crossings with motivation to find the source and way of the bow shock motion Our results suggest that often a small-scale deformation of the bow shock front is the most appropriate interpretation of observations

High and low frequency large amplitude variations of plasma and magnetic field in the magnetosheath: Radial profile and some features

Advances in Space Research, 2003

Variations in magnetosheath parameters, such as the ion flux and the magnitude of the magnetic fi... more Variations in magnetosheath parameters, such as the ion flux and the magnitude of the magnetic field, over a wide range of frequencies are much larger than the variations in the undisturbed solar wind. We present the results of a statistical investigation of magnetosheath variations using a large database of high time resolution (ls) INTERBALL-1 measurements and 1 min resolution IMP

Dynamics of the earth's bow shock position

Advances in Space Research, 1988

The paper deals with a study of the variations in the Earth's bow shock position based on simulta... more The paper deals with a study of the variations in the Earth's bow shock position based on simultaneous measurements by the Prognoz 10 and IMP-B satellites. Abrupt variations of solar wind parameters that have been registered by one apparatus are identified with shock crossings as seen by the other one. In the cases of solar windmagnetosheath crossings the velocity has been calculated also from the data obtained by only one apparatus (the one observing the crossing). Assuming the velocity of discontinuity propagation the same as the velocity of the solar wind, we can calculate the mean shock velocity from the time interval between these events. The shock model proposed by Formisano has been used for the calculations of the bow shock position. Experimental data indicates that the bow shock position depends on the magnetic field more strongly than is usually supposed /1/. On the other hand, the dependence on the solar wind dynamic pressure seems to be weaker than expected. Calculated velocities of the shock front motion lie in the interval of 2 to 60km/s. For small variations of the solar wind dynamic pressure the calculated velocity is roughly proportional to the magnitude of the variation.

Magnetosheath-cusp interface

Annales Geophysicae, 2004

We advance the achievements of Interball-1 and other contemporary missions in exploration of the ... more We advance the achievements of Interball-1 and other contemporary missions in exploration of the magnetosheath-cusp interface. Extensive discussion of published results is accompanied by presentation of new data from a case study and a comparison of those data within the broader context of three-year magnetopause (MP) crossings by Interball-1. Multi-spacecraft boundary layer studies reveal that in ∼80% of the cases the interaction of the magnetosheath (MSH) flow with the high latitude MP produces a layer containing strong nonlinear turbulence, called the turbulent boundary layer (TBL). The TBL contains wave trains with flows at approximately the Alfvén speed along field lines and "diamagnetic bubbles" with small magnetic fields inside. A comparison of the multi-point measurements obtained on 29 May 1996 with a global MHD model indicates that three types of populating processes should be operative:-large-scale (∼few R E) anti-parallel merging at sites remote from the cusp;-medium-scale (few thousand km) local TBL-merging of fields that are anti-parallel on average;

ROY—A multiscale magnetospheric mission

by M. Veselov, S. Savin, Z. Němeček, and S. Klimov

Planetary and Space Science, 2011

The scientific rationale of the ROY multi-satellite mission addresses multiscale investigations o... more

Multi-scale characteristics of the super-dense plasma streams at magnetospheric boundaries: fastest bridge for global and micro scales

by S. Savin and Z. Němeček

Energy concentration and re-distribution in the magnetospheric boundary layers

by S. Savin and Z. Němeček

Basing on comparison of the Cluster, Interball and solar wind (SW) data we discuss extremely dist... more Basing on comparison of the Cluster, Interball and solar wind (SW) data we discuss extremely disturbed magnetosheath (MSH) regions either closer to the bow shock (BS), or ahead of magnetopause (MP), which provide an evidence for unprecedented kinetic energy concentration either in spikes ('plasma jets' with the energy density up to several times above that of the unshocked SW), or