Current fluctuations in the Earth''s magnetosphere caused by lower-hybrid-drift turbulence

Nonlinear calculations of the anomalous electrical conductivity in the plasma of the earth's plasma mantle, the tail plasma sheet boundary layer and the ionospheric F-region density-trough are presented provided that lower-hybrid-drift turbulence exists. It is shown that in these regions the stabilization of the wave growth is mainly caused by current relaxation. Further, the fluctuations of the electrical currents are estimated via Ampère's and Ohm's laws. It is found that the lower-hybrid-drift turbulence causes maximum anomalous collision frequencies of the order of 10⁻² Hz in the magnetosphere. The maximum current fluctuations are about 3 10⁻⁹ A/m². The theoretical results are in agreement with ISEE and Prognoz-8 measurements.     

Current sheet with medium scale developed turbulence and the formation of the plasma sheet of Earth''s magnetosphere and solar prominences

A current sheet model with developed medium scale turbulence has been constructed. It is suggested that regular plasma flow in the current sheet is compensated by diffusive flux and plasma mixing, leading to temperature equalization. The analyzed turbulence has the form of electrostatic vortices in which electrons and ions move with the same velocities and hence does not lead to anomalous resistivity and current dissipation. It is possible to determine the plasma pressure dependence on magnetic vector potential and to find the Grad—Shafranov equation solutions. The theory is used to explain the Earth's magnetosphere plasma sheet characteristics. It is taken into account that experimentally observed plasma velocity fluctuations in the Earth's plasma sheet and quiescent prominences are much higher than regular plasma flow velocities. The analysis of turbulent current sheet dynamics after the regular motion weakening allows to construct the prominence formation theory. The decreasing of plasma pressure in the sheet due to diffusion leads to field-aligned plasma flow and plasma tube filling by cold chromospheric plasma by the action of siphon mechanism.     

The accuracy of present models of the high altitude polar magnetosphere

The Polar satellite has explored the high-latitude, high-latitude magnetosphere out to 9 Earth radii (Re). The magnetic field data returned from this mission can be used both to provide data for new empirical models and to test existing models. Tests include comparing the observed location of the polar cusp with its position in the empirical models and comparing the strength of the magnetic field in the surrounding region. Near the cusp the magnetosphere is quite sensitive to solar wind conditions. In particular the energy density of the cusp plasma depends on the pressure of the solar wind applied to the interface of the cusp and the sheath. The applied pressure in turn depends on the shape of the magnetopause and the orientation of that interface, both controlled by the direction of the interplanetary magnetic field. Magnetohydrodynamic (MHD) models provide a coarse picture of the magnetosphere at high latitudes. While generally quite realistic, these too require testing against observations because even the MHD models must make some simplifying assumptions.     

Comparing ionospheric models with mid-latitude ionosonde observations

The purpose of this research work is to validate the ionospheric models (IRI and CHIU) to assess its suitability and usefulness as an operational tool. The ionospheric model is a computer model designed to predict the state of the global ionosphere for 24 h. The scope was limited to conduct comparisons between the predicted F₂ layer critical frequencies (f₀F₂) against observed ionosonde data. The ionospheric prediction model (IPM) was designed to predict by using monthly median sunspot number, while the observation data are taken from two digital ionospheric sounding stations (Okinawa, 26.28N, 127.8E and Wakkanai, 45.38N, 141.66E) which lies within the mid-latitude region of the globe. Analysis of the f₀F₂ data from stations for year (2001) with high solar activity and year (2004) with low solar activity, four months (March, June, September and December) chosen based primarily on data availability. From results it seen that the ratio between monthly median predicted and observed f₀F₂ values for each model used in this research work and for the chosen months was nonlinear with local time, so the empirical formula for applying correction factors were determined, these formula can be used to correct the error occurred in predicted f₀F₂ value.     

Antiparticle content in the magnetosphere

In the present work we assess the stable and transient antiparticle content of planetary magnetospheres, and subsequently we consider their capture and application to high delta-v space propulsion. We estimate the total antiparticle mass contained within the Earth’s magnetosphere to assess the expediency of such usage. Using Earth’s magnetic field region as an example, we have considered the various source mechanisms that are applicable to a planetary magnetosphere, the confinement duration versus transport processes, and the antiparticle loss mechanisms. We have estimated the content of the trapped population of antiparticles magnetically confined following production in the exosphere due to nuclear interactions between high energy cosmic rays (CR) and constituents of the residual planetary upper atmosphere.The galactic antiprotons that directly penetrate into the Earth’s magnetosphere are themselves secondary by its nature, i.e. produced in nuclear reactions of the cosmic rays passing through the interstellar matter. These antiproton fluxes are modified, dependent on energy, when penetrating into the heliosphere and subsequently into planetary magnetospheres. During its lifetime in the Galaxy, CR pass through the small grammage of the interstellar matter where they produce secondary antiprotons. In contrast to this, antiprotons generated by the same CR in magnetosphere are locally produced at a path length of several tens g/cm² of matter in the ambient planetary upper atmosphere. Due to the latter process, the resulting magnetically confined fluxes significantly exceed the fluxes of the galactic antiprotons in the Earth’s vicinity by up to two orders of magnitude at some energies.The radiation belt antiparticles can possibly be extracted with an electromagnetic-based “scoop” device. The antiparticles could be concentrated by and then stored within the superimposed magnetic field structure of such a device. In future developments, it is anticipated that the energy of the captured antiparticles (both rest energy and kinetic energy) can be adapted for use as a fuel for propelling spacecraft to high velocities for remote solar system missions.     

Low-energy ion flows into the magnetosphere

Ion flows from the ionosphere into the magnetosphere fall into two main categories: cold (<1eV), “classical” polar wind and heated (>1eV), suprathermal ion outflows. A wealth of new understanding of these outflows has resulted from the Dynamics Explorer Mission. This review describes both the confirmation of the predicted classical polar wind as well as the revelation of a great variety of low-energy suprathermal outflows: the cleft ion fountain, the nightside auroral fountaion (X-events, toroids and field-aligned flows) and polar cap outflows. The main emphasis is placed on flows at energies below about 50eV, observed by the Retarding Ion Mass Spectrometer (RIMS) on board the Dynamics Explorer 1 satellite; limited comparisons are made with results from other instruments which sample different energy ranges.     

Power line radiation in the magnetosphere

VLF radiation from electrical power transmission lines stimulates nonlinear wave-particle and wave-wave interactions in the magnetosphere, resulting in wave growth, triggering of emissions, and entrainment of other natural or manmade VLF waves. Examples of these effects will be reviewed using both ground-based and satellite data. In many instances, the interpretation of data is aided by Siple transmitter results that show similar spectral characteristics.     

Field-aligned flows of ionospheric plasma in the magnetosphere

Data are presented from occasions when one of the detectors of the Suprathermal Plasma Analyser on GEOS-2 observed along the magnetic field direction. Electrons were seen with larger fluxes along the field-aligned direction than at 80° to it. One particular class of these events was identified on the night-side when electrons in the energy range 10's to 100's eV were seen. These electrons of ionospheric origin may be associated with suprathermal electron bursts or the permanent power law population of the diffuse auroral zone.     

Probing the magnetosphere with artificial electron beams

Since 1970 the Minnesota group has completed five sounding rocket experiments in which electron beams were injected into the magnetosphere at ionospheric heights and the interaction of the beams with the nearby and distant magnetosphere studied. By the technique of precisely locating conjugate region beam echoes the distant electric and magnetic field structures were studied by mapping into the local ionosphere. Ionospheric fields were measured directly for comparison. Subjects studied included gradient and curvature drifts, electric field drifts, electron pitch angle diffusion and other types of interactions with the tail plasma sheet region and the nearby ionosphere and atmosphere. The beams were also studied by plasma wave and ground-based electromagnetic detectors, by ground-based low light level television techniques and by extensive on-board rocket x-ray, photometer and particle detectors. Vehicle potentials and neutralizing processes and beam-ionosphere interactions have also been studied but will not be discussed in this paper.     

Energetic ions upstream of the Earth''s bow shock: INTERBALL-1 survey

A statistical survey of energetic ions (> 20 keV) observed by the DOK2 experiment on Interball-1 during foreshock intervals from 1996 to 1998 is presented. Flux levels depend on the connection geometry, with higher values at quasi-parallel shocks, particularly at lower energies. The decrease of flux in diffusive events with distance from the bow shock is consistent with results from earlier surveys performed closer to the bow shock. The energy spectra are softer for quasi-parallel than quasi-perpendicular connections. The reflected ions have musch softer spectra. The cumulative frequencies for flux level occurrence patterns exhibit differences for quasi-parallel and quasi-perpendicular geometries up to approximately 200 keV.     

On the long-term variability of the heliosphere–magnetosphere environment

Annual means of measured and reconstructed solar, heliospheric, and magnetospheric parameters are used to infer solar activity signatures at the Hale and Gleissberg cycles timescales. Available open solar flux, modulation strength, cosmic ray flux, total solar irradiance data, reconstructed back to 1700, solar wind parameters (speed and density) and the magnitude of the heliospheric magnetic field at 1 AU, reconstructed back to 1870, as well as the time series of geomagnetic activity indices (aa, IDV, IHV), going back to 1870, have been considered. Simple filtering procedures (successive 11-, 22-, and 88-year running averages and differences between them) and scaling by the standard deviation from the average value for the common interval covered by the data show that the long-discussed variation in the 20th century (a pronounced increase since ∼1900, followed by a depression in the ‘60s and a new, slower, increase) seen in the 11-year averages of parameters such as geomagnetic activity indices and reconstructed heliospheric magnetic field strength, solar wind speed, open solar flux, is a result of the superposition in data of solar activity signatures at Hale and Gleissberg cycles timescales. The Hale and Gleissberg signals were characterized and similarities and differences in the temporal behavior of the analyzed parameters at these timescales are discussed. The similarities in the studied parameters point to a common pacing source, the solar dynamo.     

The low energy plasma in the Uranian magnetosphere

The Plasma Science experiment on Voyager 2 detected a magnetosphere filled with a tenuous plasma, rotating with the planet. Temperatures of the plasma, composed of protons and electrons, ranged from 10 eV to ∼1 keV. The sources of these protons and electrons are probably the ionosphere of Uranus or the extended neutral hydrogen cloud surrounding the planet. As at Earth, Jupiter, and Saturn, there is an extended magnetotail with a central plasma sheet. Although similar in global structure to the magnetospheres of these planets, the large angle between the rotation and magnetic axes of the planet and the orientation of the rotation axis with respect to the solar wind flow make the Uranian magnetosphere unique.     

Auroral signatures of transient processes in the outer magnetosphere

We present an analysis of sporadic and recurrent injections of magnetospheric ions in the midnight auroral oval during substorms and of the associated ionospheric ion outflows. The source of plasma sheet precipitating ions is determined using a simple method, based on the measured relation between the ion inverse velocity and time (l = v × t). This method is applied here to two typical passes of the Interball-Auroral (IA) satellite at distances of 3 R_E above the auroral regions. Substorm related ion injections are shown to be mainly due to time of flight effects. In contrast with particle trajectory computations (Sauvaud et al., 1999), the inverse velocity method does not require magnetic and electric field models and can thus be used systematically for the detection of time of flight dispersed ion structures (TDIS). This allowed us to build a large database of TDIS events and to perform a statistical analysis of their spatial distribution. For the cases presented here the source region of the injected ions is found at radial distances from 18 to 30 R_E near the equatorial magnetosphere. At Interball altitudes ( 3 R_E), ion injections detected at the poleward boundary of the nighside auroral oval are associated with shear Alfvén waves superimposed over large-scale quasi-static current structures. We show that the most poleward TDIS are collocated with a large outflow of ionospheric H⁺ and O⁺ displaying pitch-angle distributions peaked in the pitch-angle range 90°–120°. These ions are thus accelerated perpendicularly to the magnetic field not only in the main auroral acceleration region but also up to at least 3 R_E. The expanding auroral bulge thus constitutes a significant source of H⁺ and O⁺ ions for the mid-tail magnetosphere.     

Plasma convection in the low-latitude mantle of the near-earth magnetosphere

A detailed analysis of Geotail observations on June 1, 1997 provides evidence for the appearance of the plasma mantle at low-latitudes, Z_GSM 3 R_E for southward interplanetary magnetic field (IMF), and clarifies the characteristics of the plasma flow in the low-latitude mantle. The tailward flow speed in the mantle is 80 160 km/s, smaller than the flow speed (300 km/s) in the adjacent magnetosheath. The component of the velocity perpendicular to the magnetic field lines is predominantly poleward at speeds up to 60 km/s, and the convection tends to be stronger for |;B_Y|<|;B_Z| than for IMF |B_Y|>|B_Z|;. This polewardconvection can be interpreted as being driven by a J × B force operating on the field lines.