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.
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.
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.
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.
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. [
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.
... References. 1. M. Scholer Geophys. Monograph 35 (1985), p. 287 AGU . 2. S. Fischer, K. Kudela... more ... References. 1. M. Scholer Geophys. Monograph 35 (1985), p. 287 AGU . 2. S. Fischer, K. Kudela, V. Lutsenko, J. Mati in and J. Rojko , Intershock Project. Publ. Astron. Institute Prague No. 60 (1985), p. 166. 3. V. Lutsenko, Z. N me ek and J. afránková , Intershock Project. Publ. ...
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.
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.
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
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
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.
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;
The scientific rationale of the ROY multi-satellite mission addresses multiscale investigations o... more The scientific rationale of the ROY multi-satellite mission addresses multiscale investigations of plasma processes in the key magnetospheric regions with strong plasma gradients, turbulence and magnetic field annihilation in the range from electron inertial length to MHD scales.
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
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.
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.
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.
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.
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. [
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.
... References. 1. M. Scholer Geophys. Monograph 35 (1985), p. 287 AGU . 2. S. Fischer, K. Kudela... more ... References. 1. M. Scholer Geophys. Monograph 35 (1985), p. 287 AGU . 2. S. Fischer, K. Kudela, V. Lutsenko, J. Mati in and J. Rojko , Intershock Project. Publ. Astron. Institute Prague No. 60 (1985), p. 166. 3. V. Lutsenko, Z. N me ek and J. afránková , Intershock Project. Publ. ...
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.
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.
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
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
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.
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;
The scientific rationale of the ROY multi-satellite mission addresses multiscale investigations o... more The scientific rationale of the ROY multi-satellite mission addresses multiscale investigations of plasma processes in the key magnetospheric regions with strong plasma gradients, turbulence and magnetic field annihilation in the range from electron inertial length to MHD scales.
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
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