M. S. Pulinets

Topology of High-Latitude Magnetospheric Currents

The structure and localization of high latitude transverse and field-aligned currents are analyzed using the data from the Themis satellite mission. A number of evidences resumed in this paper, including daytime compression of magnetic field lines and the existence of magnetic field minima far from the equatorial plane make necessary to reanalyze the traditional points of view about the topology of high-latitude magnetospheric currents. Comparison between the dayside integral transverse currents at the geocentric distances 7–10R E , calculated assuming the validity of the condition of magnetostatic equilibrium and the nighttime transverse currents, showed that ordinary ring current has the high latitude continuation until geocentric distances ∼10–13R E . The problem of the location of Region 1 field-aligned current of Iijima and Potemra is discussed.

Dependence of magnetic field parameters at the subsolar point of the magnetosphere on the interplanetary magnetic field according to the data of the THEMIS experiment

We analyze the dependence of the magnitude of the magnetic field, its three components, and the clock angle in the magnetosheath just in front of the magnetopause on the same values in the solar wind before a shock wave using the data of the THEMIS experiment. We take into account the time delay of the solar wind arrival at the subsolar point of the magnetopause. We obtain dependencies of the components of the magnetic field and the clock angle at the magnetopause on the corresponding quantities in the solar wind for different averaging intervals. We point to the events for which the direction of the magnetic field at the magnetopause is highly different from the direction of the magnetic field in the solar wind up to the sign change.

Magnetospheric substorms and discrete arcs of the polar aurora

A brief review of the results of the research in physics of the Earth’s magnetosphere leading to a substantial modification of the previously developed approaches is presented. The main emphasis is placed on physics of magnetospheric substorms and the nature of auroral arcs. It is shown that the formation of powerful electron beams that produce multiple arcs can be associated with the penetration of cold electrons of an ionospheric origin into the region of field-aligned acceleration of hot magnetospheric electrons.

Turbulence in the Magnetosheath and the Problem of Plasma Penetration Inside the Magnetosphere

Chapman & Ferraro (1931) introduced the concept of confinement of the Earths magnetic field in a cavity carved in the solar plasma flow. The balance between the Earth’s magnetic field (more accurately between the magnetic pressure at the boundary of the cavity) and the solar wind dynamic pressure was considered as the condition of the formation of the boundary of the cavity. Chapman-Ferraro model is called a closed magnetosphere. Low energy particles can not penetrate through the boundary of the cavity. Dungey (1961) made the most drastic revision of Chapman-Ferraros original theory. Dungey envisaged that the connection process, called reconnection, takes place on the dayside magnetopause and that the connected field lines are then transported in the antisolar direction by the solar wind, resulting in the magnetotail. Subsequently, the field lines are reconnected there and then transported back to the dayside magnetosphere. Such process takes place when interplanetary magnetic field (IMF) has the southward direction. The large scale reconnection takes place at high latitudes when IMF has the northward direction. The scheme shown on Fig. 1 demonstrates Dungey’s concept of reconnection at the dayside magnetopause when IMF has southword (a) and northward (b) directions. The model of Dungey qualitatively accounts for such phenomena as the inward motion of the dayside magnetopause, equatorward motion of the cusp, expansion of the auroral oval, increase in magnetotail magnetic field strength, and expansion of the magnetotail radius which occur when the IMF turns southward. It can also easily explain the penetration of the plasma of solar wind origin inside the magnetosphere. That is why this concept for a long period was the dominant concept in the physics of the magnetosphere and was widely used for the description of different phenomena including the formation of boundary layers (see, for example, the review Lavraud et al. (2011)). However step by step a number of observations ant theoretical arguments have appeared which give the possibility to throw doubts on the applicability of the scheme shown on Fig. 1 for the real situation.

Variations in plasma parameters and magnetic field upon magnetopause crossing at the main phase maximum of the magnetic storm of November 14, 2012

Measurements of the plasma parameters and magnetic field upon magnetopause crossings by the THEMIS-А satellite during the large magnetic storm of November 14, 2012, are analyzed. The main specific feature of this event is the magnetopause crossing at the time of the magnetic-storm maximum. An imbalance of total pressure on the magnetopause reaching up to ~40% has been observed. An abrupt turn of the magnetic field immediately on the magnetopause is recorded. Inside the magnetosphere, plasma motions have been observed, both along the magnetopause and inward, at velocities of ~100–300 km/s. Variations in geomagnetic parameters are analyzed before and after the crossing. It is shown that specific features of the observed crossing may be associated with a sharp change in the magnetospheric current systems during the magnetospheric substorm.

Determining the thickness of the low-latitude boundary layer in the Earth’s magnetosphere

We describe a method for determining the thickness of the low-latitude boundary layer (LLBL) of the Earth’s magnetosphere at the dayside near the equatorial plane based on the data gathered by a single satellite that traverses the layer and measures the plasma velocity. The method may be applied when the position of the magnetopause and the magnetosheath parameters fluctuate. The necessity of taking the presence of outer and inner LLBL regions into account is analyzed. The developed method is tested using the analysis results of two almost simultaneous close traverses of the magnetopause completed by the THEMIS mission satellites that provided relatively precise data on the LLBL thickness. It is shown that the developed method makes it possible to determine the LLBL thickness with an accuracy of ∼10%.

Thickness of the low latitude boundary layer at different levels of magnetic field fluctuations in the magnetosheath

The role of a high fluctuations level in the Earth’s magnetosheath in plasma penetration into the magnetosphere and in the formation of the low-latitude boundary layer (LLBL) has been considered based on the events that occurred on November 1 and 5, 2007, using the THEMIS-A satellite observations. During the selected LLBL crossings the satellite was measuring behind the quasi-parallel and quasi-perpendicular bow shocks. The angle between the magnetic field direction in the solar wind and the normal to the bow shock (ΘBn) has been taken as a parameter reflecting the level of magnetic field and plasma paremeters fluctuations in the magnetosheath. It has been indicated that a thick LLBL is observed when angle ΘBn is small and the turbulence level in the magnetosheath is high. When angle ΘBn is large, the layer thickness decreases. The possible mechanisms by which a thick LLBL is formed are discussed.