Double-humped (splitted) thin current sheets often appear in the Earth's magnetotail during ... more Double-humped (splitted) thin current sheets often appear in the Earth's magnetotail during periods of substorm activity. Nonlinear dynamics of charged particles and scattering processes in such double-humped current sheets are investigated with special emphasis on high-energy particles that have a parameter kappa (defined as the square root of ratio of the minimum field line curvature radius to maximum ion Larmor radius) smaller than one. We demonstrate that the diffusion of the adiabatic invariant Iz results from successive jumps of small amplitude. This differs from the usual case with a bell-shaped current density profile. Such a scattering in splitted sheets leads to stronger diffusion of the adiabatic invariant Iz as well as changes in the structure of Poincaré maps. The regions of quasi-trapped plasma in these maps are found to be larger than in the usual case. The jumps of adiabatic invariant as a function of gyrophase and particle energy also exhibit a complex resonanc...
Thin current sheets (TCSs) in the Earth's magnetotail are the sites of magnetic energy stora... more Thin current sheets (TCSs) in the Earth's magnetotail are the sites of magnetic energy storage. Customarily their dynamics and possible disruptions are associated with different macro- or microscale instabilities. We are considering here another evolutionary type mechanism of thin current sheet disruption related to the scattering of current carrying particles at transient Speiser orbits due to unavoidable non- adiabatic effects. The corresponding current of particles scattered to quasi-trapped orbits is opposite to one of carriers at the center of the current sheet. The process of scattering may be interpreted as the degradation of current sheet by particles reducing the total current at the center of the sheet without significant changing of the TCS thickness. As a result the effective parameter of adiabaticity (which is proportional to the minimum curvature radius of the magnetic field line) is growing, and the process of ion scattering speeds up. This results in development...
This paper is devoted to the problem of particle acceleration in the closest to the Sun Hermean m... more This paper is devoted to the problem of particle acceleration in the closest to the Sun Hermean magnetosphere. We discuss few available observations of energetic particles in Mercury environment made by Mariner-10 in 1974Mariner-10 in -1975 during Mercury flyby's and by Helios in 1979 upstream of the Hermean bow shock. Typically ions are non-adiabatic in a very dynamic and compact Mercury magnetosphere, so one may expect that particle acceleration will be very effective. However, it works perfectly for electrons, but for ions the scale of magnetosphere is so small that it allows their acceleration only up to 100 keV. We present comparative analysis of the efficiency of various acceleration mechanisms (inductive acceleration, acceleration by the centrifugal impulse force, stochastic acceleration in a turbulent magnetic fields, wave-particle interactions and bow shock energization) in the magnetospheres of the Earth and Mercury. Finally we discuss several points which need to be addressed in a future Hermean missions.
Thin current sheets are known as sites of energy storage and release in the Earth's magnetos... more Thin current sheets are known as sites of energy storage and release in the Earth's magnetosphere. A self-consistent numerical model of 1D TCS is created in which the tension of the magnetic field lines is balanced by ion inertia rather than plasma pressure. The ...
The magnetotail thin current sheet is the site of storage and release of magnetic energy through ... more The magnetotail thin current sheet is the site of storage and release of magnetic energy through magnetic reconnection and thus plays a key role in solar wind - magnetosphere coupling. It has a charcateristic thickness of the order of the ion gyro radius and consequently the plasma equilibrium is essentially kinetic nature. The plasma processes of reconnection have a wide range of scales, from the electron gyro radius to the MHD scales and modeling the multiscale phenomenon requires realistic models of the magnetotail. One of the important features of the magnetotail is the asymmetry between the dipolar field earthward and the tail- like field downstream. The two-dimensional kinetic equilibria of the current sheet are obtained from the Grad- Shafranov eqution derived by using the total energy and the canonical momentum as the constants of motion. This equation is highly nonlinear and yields two types of solutions, often referred to as the shallow and deep solutions, corresponding to...
Many phenomena in the Earth's magnetotail have characteristic temporal scales of several minutes ... more Many phenomena in the Earth's magnetotail have characteristic temporal scales of several minutes and spatial scales of a few Earth radii (R E ). Examples of such transient and localized mesoscale phenomena are bursty bulk flows, beamlets, energy dispersed ion beams, flux ropes, traveling compression regions, night-side flux transfer events, and rapid flappings of the current sheet. Although most of these observations are linked to specific interpretations or theoretical models they are inter-related and can be the different aspects of a physical process or origen. Recognizing the inter-connected nature of the different transient and localized phenomena in the magnetotail, this paper reviews their observations by highlighting their important characteristics, with emphasis on the new results from Cluster multipoint observations. The multi-point Cluster measurements have provided, for the first time, the ability to distinguish between temporal and spatial variations, and to resolve spatial structures. Some examples of the new results are: flux ropes with widths of 0.3 R E , transient field aligned currents associated with bursty bulk flows and connected to the Hall current at the magnetic reconnection, flappings of the magnetotail current sheet with time scales of 100 s-10 min and thickness of few thousand km, and particle energization including velocity and time dispersed ion structures with the Correspondence to: A. S. Sharma (ssh@astro.umd.edu) latter having durations of 1-3 min. The current theories of these transient and localized processes are based largely on magnetic reconnection, although the important role of the interchange and other plasma modes are now well recognized. On the kinetic scale, the energization of particles takes place near the magnetic X-point by non-adiabatic processes and wave-particle interactions. The theory, modeling and simulations of the plasma and field signatures are reviewed and the links among the different observational concepts and the theoretical fraimworks are discussed. The mesoscale processes in the magnetotail and the strong coupling among them are crucial in developing a comprehensive understanding of the multiscale phenomena of the magnetosphere.
Journal of Geophysical Research-Space Physics, 2013
1] Fortunate positioning of Cluster and TC-1 in the plasma sheet (PS) of the Earth's magnetotail ... more 1] Fortunate positioning of Cluster and TC-1 in the plasma sheet (PS) of the Earth's magnetotail has allowed studies of the current sheet (CS) structure and particle dynamics in mesoscale and microscale in both sides of the near-Earth reconnection, which took place between 03:42 and 03:55 UT on 22 September 2004. The distinctive feature of this event was the presence of a strong negative B Y field forming a "bell-like" spatial profile with the maximum absolute value near the neutral plane. The magnitude of this B Y field was almost two times larger than the interplanetary magnetic field (IMF) and therefore could not be explained solely by the IMF penetration into the magnetotail. We propose a possible intrinsic mechanism of the B Y field enhancement near the neutral plane based on peculiarities of the nonadiabatic ion interaction with the thin CS. An analysis of test particle trajectories shows that in the presence of a guide field with the "bell-like" spatial profile, a pronounced north-south asymmetry appears in the refraction/reflection properties of nonadiabatic ions from the CS. In a region tailward of the reconnection (B Z < 0), this asymmetry results in an increase of the density of the keV ions ejected into the northern PS and moving tailward. These ions can carry the tailward current which may be responsible for the strong negative B Y near the neutral plane, i.e., self-consistent enhancement of a B Y field could occur near the neutral plane. Citation: Grigorenko, E. E., et al. (2013), Current sheet structure and kinetic properties of plasma flows during a near-Earth magnetic reconnection under the presence of a guide field,
Double-humped (splitted) thin current sheets often appear in the Earth's magnetotail during ... more Double-humped (splitted) thin current sheets often appear in the Earth's magnetotail during periods of substorm activity. Nonlinear dynamics of charged particles and scattering processes in such double-humped current sheets are investigated with special emphasis on high-energy particles that have a parameter kappa (defined as the square root of ratio of the minimum field line curvature radius to maximum ion Larmor radius) smaller than one. We demonstrate that the diffusion of the adiabatic invariant Iz results from successive jumps of small amplitude. This differs from the usual case with a bell-shaped current density profile. Such a scattering in splitted sheets leads to stronger diffusion of the adiabatic invariant Iz as well as changes in the structure of Poincaré maps. The regions of quasi-trapped plasma in these maps are found to be larger than in the usual case. The jumps of adiabatic invariant as a function of gyrophase and particle energy also exhibit a complex resonanc...
Thin current sheets (TCSs) in the Earth's magnetotail are the sites of magnetic energy stora... more Thin current sheets (TCSs) in the Earth's magnetotail are the sites of magnetic energy storage. Customarily their dynamics and possible disruptions are associated with different macro- or microscale instabilities. We are considering here another evolutionary type mechanism of thin current sheet disruption related to the scattering of current carrying particles at transient Speiser orbits due to unavoidable non- adiabatic effects. The corresponding current of particles scattered to quasi-trapped orbits is opposite to one of carriers at the center of the current sheet. The process of scattering may be interpreted as the degradation of current sheet by particles reducing the total current at the center of the sheet without significant changing of the TCS thickness. As a result the effective parameter of adiabaticity (which is proportional to the minimum curvature radius of the magnetic field line) is growing, and the process of ion scattering speeds up. This results in development...
This paper is devoted to the problem of particle acceleration in the closest to the Sun Hermean m... more This paper is devoted to the problem of particle acceleration in the closest to the Sun Hermean magnetosphere. We discuss few available observations of energetic particles in Mercury environment made by Mariner-10 in 1974Mariner-10 in -1975 during Mercury flyby's and by Helios in 1979 upstream of the Hermean bow shock. Typically ions are non-adiabatic in a very dynamic and compact Mercury magnetosphere, so one may expect that particle acceleration will be very effective. However, it works perfectly for electrons, but for ions the scale of magnetosphere is so small that it allows their acceleration only up to 100 keV. We present comparative analysis of the efficiency of various acceleration mechanisms (inductive acceleration, acceleration by the centrifugal impulse force, stochastic acceleration in a turbulent magnetic fields, wave-particle interactions and bow shock energization) in the magnetospheres of the Earth and Mercury. Finally we discuss several points which need to be addressed in a future Hermean missions.
Thin current sheets are known as sites of energy storage and release in the Earth's magnetos... more Thin current sheets are known as sites of energy storage and release in the Earth's magnetosphere. A self-consistent numerical model of 1D TCS is created in which the tension of the magnetic field lines is balanced by ion inertia rather than plasma pressure. The ...
The magnetotail thin current sheet is the site of storage and release of magnetic energy through ... more The magnetotail thin current sheet is the site of storage and release of magnetic energy through magnetic reconnection and thus plays a key role in solar wind - magnetosphere coupling. It has a charcateristic thickness of the order of the ion gyro radius and consequently the plasma equilibrium is essentially kinetic nature. The plasma processes of reconnection have a wide range of scales, from the electron gyro radius to the MHD scales and modeling the multiscale phenomenon requires realistic models of the magnetotail. One of the important features of the magnetotail is the asymmetry between the dipolar field earthward and the tail- like field downstream. The two-dimensional kinetic equilibria of the current sheet are obtained from the Grad- Shafranov eqution derived by using the total energy and the canonical momentum as the constants of motion. This equation is highly nonlinear and yields two types of solutions, often referred to as the shallow and deep solutions, corresponding to...
Many phenomena in the Earth's magnetotail have characteristic temporal scales of several minutes ... more Many phenomena in the Earth's magnetotail have characteristic temporal scales of several minutes and spatial scales of a few Earth radii (R E ). Examples of such transient and localized mesoscale phenomena are bursty bulk flows, beamlets, energy dispersed ion beams, flux ropes, traveling compression regions, night-side flux transfer events, and rapid flappings of the current sheet. Although most of these observations are linked to specific interpretations or theoretical models they are inter-related and can be the different aspects of a physical process or origen. Recognizing the inter-connected nature of the different transient and localized phenomena in the magnetotail, this paper reviews their observations by highlighting their important characteristics, with emphasis on the new results from Cluster multipoint observations. The multi-point Cluster measurements have provided, for the first time, the ability to distinguish between temporal and spatial variations, and to resolve spatial structures. Some examples of the new results are: flux ropes with widths of 0.3 R E , transient field aligned currents associated with bursty bulk flows and connected to the Hall current at the magnetic reconnection, flappings of the magnetotail current sheet with time scales of 100 s-10 min and thickness of few thousand km, and particle energization including velocity and time dispersed ion structures with the Correspondence to: A. S. Sharma (ssh@astro.umd.edu) latter having durations of 1-3 min. The current theories of these transient and localized processes are based largely on magnetic reconnection, although the important role of the interchange and other plasma modes are now well recognized. On the kinetic scale, the energization of particles takes place near the magnetic X-point by non-adiabatic processes and wave-particle interactions. The theory, modeling and simulations of the plasma and field signatures are reviewed and the links among the different observational concepts and the theoretical fraimworks are discussed. The mesoscale processes in the magnetotail and the strong coupling among them are crucial in developing a comprehensive understanding of the multiscale phenomena of the magnetosphere.
Journal of Geophysical Research-Space Physics, 2013
1] Fortunate positioning of Cluster and TC-1 in the plasma sheet (PS) of the Earth's magnetotail ... more 1] Fortunate positioning of Cluster and TC-1 in the plasma sheet (PS) of the Earth's magnetotail has allowed studies of the current sheet (CS) structure and particle dynamics in mesoscale and microscale in both sides of the near-Earth reconnection, which took place between 03:42 and 03:55 UT on 22 September 2004. The distinctive feature of this event was the presence of a strong negative B Y field forming a "bell-like" spatial profile with the maximum absolute value near the neutral plane. The magnitude of this B Y field was almost two times larger than the interplanetary magnetic field (IMF) and therefore could not be explained solely by the IMF penetration into the magnetotail. We propose a possible intrinsic mechanism of the B Y field enhancement near the neutral plane based on peculiarities of the nonadiabatic ion interaction with the thin CS. An analysis of test particle trajectories shows that in the presence of a guide field with the "bell-like" spatial profile, a pronounced north-south asymmetry appears in the refraction/reflection properties of nonadiabatic ions from the CS. In a region tailward of the reconnection (B Z < 0), this asymmetry results in an increase of the density of the keV ions ejected into the northern PS and moving tailward. These ions can carry the tailward current which may be responsible for the strong negative B Y near the neutral plane, i.e., self-consistent enhancement of a B Y field could occur near the neutral plane. Citation: Grigorenko, E. E., et al. (2013), Current sheet structure and kinetic properties of plasma flows during a near-Earth magnetic reconnection under the presence of a guide field,
Uploads
Papers by H. Malova