“The charge-exchange processes with the neutral geocorona and the charged ring current particles can be strong enough to produce enough signal to monitor the plasmaspheric and ring current dynamics in the inner magnetosphere.” https://t.co/O218eVjrnc

“Recently, the NASA IMAGE mission with its onboard neutral atom imagers demonstrated that also the charge-exchange processes with the neutral geocorona and the charged ring current particles.” https://t.co/O218eVjrnc

“For a long time, the auroral light from the polar region ionospheres was the only source that could provide two-dimensional images of the large-scale space plasma processes.” https://t.co/O218eVjrnc

“However, the limited number of measurement points still means that many quantities must be evaluated using proxy parameters derived either from point measurements in space or from ground-based observations.” https://t.co/O218eVjrnc

“The European Space Agency’s Cluster mission with its four satellites flying in constellation has for the first time allowed for separation of space and time and by identification of full three-dimensional vector quantities from four point measurements.” h

The magnetosphere-ionosphere system. “The sparsity of the satellite fleet and the vast regions to be covered means that, at any given time, direct measurements of the magnetospheric processes are limited to only a few points in space.” https://t.co/O218eVj

“Magnetic storms include, in addition to strong substorm activity, also other kinds of strong activity, field-aligned currents, and inner magnetosphere disturbances.” https://t.co/O218eVjrnc

“On the other hand, stronger levels of driving may lead to sawtooth oscillations, which are large-scale substorms associated with strong, longitudinally extended, quasi-simultaneous injections at geostationary orbit recurring every 2–3 h.” https://t.co/O21

“Steady convection intervals are periods of steadily southward IMF and steady, relatively slow solar wind flow that drive continuous, low-level auroral activity without evident substorm expansion phase activity.” (IMF= interplanetary magnetic field). https

“The magnetospheric substorms and storms are the most commonly occurring responses to enhanced solar wind driving, but the magnetosphere can enter into a variety of other dynamic states.” https://t.co/O218eVjrnc

“It is debated whether the substorm-associated magnetic field variations and the associated (inductive) electric fields are necessary for the buildup of the ring current energy density.” https://t.co/O218eVjrnc

“The interaction of the inner magnetosphere storm-associated processes with the magnetotail substorm-associated processes is highly complex, and presently under active study.” https://t.co/O218eVjrnc

“While substorms can occur without magnetic storms, almost all storms include also substorm activity.” https://t.co/O218eVjrnc

“Storms as largest magnetospheric disturbances are associated with many of the space weather phenomena.” https://t.co/O218eVjrnc

Mag storms. “At times, the ionospheric outflow can be strong enough for the ionospheric oxygen to dominate the energy density in the ring current.” https://t.co/O218eVjrnc

Mag storms. “The ring current is populated both by efficient convection and injection of plasma sheet particles into the inner region and by strongly enhanced ion outflow from the ionosphere.” https://t.co/O218eVjrnc

“Magnetic storms typically last from about 12 hours to a few days. Storms are characterized by the formation of an intense ring current encircling the Earth with current peak at about 4 RE, i.e., well inside the geostationary orbit.” https://t.co/O218eVjrn

Magnetic storms “often follow from the interaction of a fast solar wind stream, an interplanetary magnetic cloud, an ICME, or other coherent solar wind structure.” https://t.co/O218eVjrnc

“It takes several hours of southward interplanetary field and/or high solar wind speed to create a magnetic storm.” https://t.co/O218eVjrnc

“Magnetospheric substorms require a period of enhanced energy input (southward interplanetary field) from 30 minutes to 1 hour. If the energy input continues significantly longer (≥3 h), a magnetic storm develops.” https://t.co/O218eVjrnc

Energy gyres. “It is estimated that about half of the energy that enters via the dayside reconnection process is processed in the inner magnetosphere and ionosphere, while the other half is carried by the plasmoid(s) back to the solar wind.” https://t.co/O

“This plasmoid is accelerated tailward and ejects a large portion of the plasma sheet plasma, magnetic flux, and energy back to the solar wind.” https://t.co/O218eVjrnc

“Magnetic reconnection in the tail leads to formation of a plasma structure where the field lines are no longer connected to the Earth.” https://t.co/O218eVjrnc

“Energetic electrons precipitating into the ionosphere and colliding with the atmospheric constituents create bright auroral displays in the night sector auroral region.” https://t.co/O218eVjrnc

“On ground, magnetospheric substorms are seen as disturbances in the geomagnetic field caused by the field-aligned current systems and auroral electrojet currents in the ionosphere.” https://t.co/O218eVjrnc

Field-aligned current sheets, “where the current flows to the ionosphere at the eastern edge of the reconnection region and out from the ionosphere at the western edge.” https://t.co/O218eVjrnc

Plasma sheet. “The flow shear between the fast outflow from the reconnection region and the ambient Earthward plasma flow within the plasma sheet creates a pair of field-aligned current sheets.” https://t.co/O218eVjrnc

“As this thin current sheet grows unstable, a rapid dissipation process quickly expands to a large-scale reconnection event whose effects are observable over a large portion of the coupled magnetosphere-ionosphere system.” https://t.co/O218eVjrnc

Magnetosphere. “The current sheet at the tail center has a thickness of only a few hundred kilometers (comparable to the thermal ion gyroradius), and the magnetic field component normal to the current sheet becomes very small, only a few nanotesla.” https:

Substorms increase magnetosphere energy. “This causes a configuration change in the magnetosphere including enhancement of the magnetospheric current systems and formation of a thin and intense current sheet from near-geostationary distance outward.” https

“Substorms typically occur at a rate of four to five per day, each lasting typically two to three hours. They are initiated by enhanced dayside reconnection and hence increased energy input to the magnetosphere.” https://t.co/O218eVjrnc

“Variability in the north-south orientation of the interplanetary magnetic field causes episodic energy loading-dissipation cycles termed magnetospheric substorms.” https://t.co/O218eVjrnc

“Energy transfer is most efficient when the reconnection process takes place at the dayside magnetopause, which occurs during periods when the interplanetary field points southward and is thus antiparallel to the intrinsic geomagnetic field.” https://t.co/

“Energy, momentum, and plasma enter the magnetosphere both via magnetic reconnection at the magnetospheric boundaries in regions where the interplanetary and terrestrial fields are antiparallel and via viscous interactions along the boundary.” https://t.co

“Figure 4. The plasma sheet in the closed field line region extends to the dayside magnetopause and to the distant nightside tail.” https://t.co/O218eVjrnc

 “Figure 4. Inner magnetosphere plasma populations. The outer van Allen belt, the ring current, and the plasmasphere are colocated within the inner magnetosphere trapping region.” https://t.co/O218eVjrnc

“The plasma populations can retain their characteristics without being thermalized, and that the plasma distribution functions can significantly deviate from simple Maxwellians. Figure 4 shows the key plasma populations in the magnetosphere.” https://t.co/

Plasma. “It is important to note that the dynamic processes all occur on time scales that are short compared to collision times.” https://t.co/O218eVjrnc

“The relatively low collision frequencies that keep the system from obtaining thermal equilibrium all contribute to the complexity and variability of the inner magnetosphere plasma populations.” https://t.co/O218eVjrnc

“The quasi-dipolar field allows trapping of the particles to closed drift orbits.” https://t.co/O218eVjrnc

“The variety of processes bringing particles into the inner magnetosphere.” https://t.co/O218eVjrnc

“The electron acceleration and loss processes are strongly dependent on the electric field structure and the wave-particle interactions in the inner magnetosphere.” https://t.co/O218eVjrnc

The electron fluxes. “Their rapid drift motion around the Earth is largely controlled by the magnetic field geometry, in contrast to the cold particles that are guided both by the electric and magnetic fields.” https://t.co/O218eVjrnc

“These relativistic electron fluxes show sharp dropouts and enhancements in response to the varying geomagnetic activity, and their dynamics is key to space weather, as these electrons pose a hazard to satellites in Earth orbit.” https://t.co/O218eVjrnc

“The electrons reside colocated with the ring current and the plasmasphere in the inner magnetosphere, roughly from 3 RE to slightly beyond geostationary orbit.” https://t.co/O218eVjrnc

“The outer van Allen radiation belt consists mainly of electrons in the energy range from hundreds of keV to several MeV.” https://t.co/O218eVjrnc

“The ring current decays via charge exchange processes and Coulomb collisions with the exospheric particles.” https://t.co/O218eVjrnc

The ring current composition changes from being dominated by solar wind protons and doubly charged helium to consisting large percentages (up to dominating the mass and energy density) of ionospheric oxygen and to lesser amounts of singly charged helium.”

Ring current. “During magnetically active times, ion outflow from the ionosphere is greatly enhanced.” https://t.co/O218eVjrnc

“The ring current typically consists of ions in the energy range from a few tens of keV to several hundred keV, and has a highly variable intensity controlled by the level of geomagnetic activity.” https://t.co/O218eVjrnc

“The ring current encircling the Earth roughly in the region 2–7 RE from the Earth consists of plasmas originating both from the solar wind and the ionosphere.” https://t.co/O218eVjrnc

The plasmapause particles “outside the trapping boundary drift under the dawn-to-dusk electric field to the dayside boundary and are lost in the outer magnetosphere and eventually to the solar wind.” https://t.co/O218eVjrnc

The plasmapause. “Particles inside the trapping boundary remain on closed drift paths around the Earth.” https://t.co/O218eVjrnc

“In the vicinity of this boundary, the plasma density has a sharp gradient; this is known as the plasmapause.” https://t.co/O218eVjrnc

“The interplay between the solar wind-imposed electric field and the corotation electric field creates a boundary inside of which particles are trapped on closed orbits around the Earth.” https://t.co/O218eVjrnc

“The Earth’s rotation sets up an electric field, which drags the cold plasma into a corotational motion.” https://t.co/O218eVjrnc

“The radius of the torus is variable, but typically the plasmasphere extends close to geostationary orbit, being more compressed during geomagnetically active times and more extended during long periods of magnetic quiescence.” https://t.co/O218eVjrnc

“The plasmasphere consists mostly of protons, with singly charged helium accounting for about 20% of the number density.” https://t.co/O218eVjrnc

“The upward extension of the ionosphere, the plasmasphere, is a torus filled with low-energy (around 1 eV), dense (10–1000cm−3) plasma originating from the ionosphere.” https://t.co/O218eVjrnc

“During active magnetospheric processes, auroral precipitation is enhanced, localized, and highly structured, especially in the nightside oval.” https://t.co/O218eVjrnc

The auroral oval “is the region where particles precipitating from the plasma sheet and colliding with atmospheric atoms and molecules create visible auroral light.” https://t.co/O218eVjrnc

“The region encircling the magnetic poles where the current systems flow is also called the auroral oval.” https://t.co/O218eVjrnc

“The more poleward current Region 1 currents couple to the magnetotail and magnetospheric boundaries, whereas the more equatorward Region 2 currents couple to the ring current in the inner magnetosphere.” https://t.co/O218eVjrnc

“The ionosphere is coupled to the magnetosphere by highly structured and dynamic field-aligned currents, which on an average sense form a pair of large-scale field-aligned current sheets.” https://t.co/O218eVjrnc

“Consequently, the plasma flows from the dayside toward the nightside over the polar cap, returning to the dayside along the lower latitudes, consistent with the Dungey cycle.” https://t.co/O218eVjrnc

“The solar wind electric field drives a global convection pattern in the ionosphere, which produces convection electrojets carried by drift currents flowing eastward on the duskside and westward on the dawnside of the ionosphere.” https://t.co/O218eVjrnc

“From space weather point of view, the ionosphere is significant both because of its effects on radio waves and because it hosts strong electric currents whose effects extend to the ground.” https://t.co/O218eVjrnc

“The ionospheric plasma processes couple both to the neutral atmosphere below and to the magnetospheric processes above.” https://t.co/O218eVjrnc

“Above about 80 km altitude, the solar ultraviolet radiation ionizes a small portion of the atmospheric gas creating what is known as the ionosphere.” https://t.co/O218eVjrnc

“During active times, when the flux of energetic charged particles is sufficiently high, this provides (the only) means to image the inner parts of the magnetosphere.” https://t.co/O218eVjrnc

“The slow neutral atoms charge-exchanging with fast charged particles create a population of high-speed neutrals that propagate linearly away from the collision site.” https://t.co/O218eVjrnc

“Coulomb collisions and charge-exchange processes with neutral atoms are significant loss mechanisms for energetic charged particles in the inner magnetosphere, and thus contribute to the recovery of quiet conditions after a magnetic storm.” https://t.co/O

“While the neutral atoms and molecules are not influenced by the electromagnetic forces, the geocorona is significant to space physics processes in at least two ways.” https://t.co/O218eVjrnc

“The neutral exosphere, or the upward extension of the atmosphere, fills the near-Earth space with an exponentially decreasing density.” https://t.co/O218eVjrnc

“In addition to the solar wind flow, the atmosphere contributes both to the neutral and charged particle density in the magnetosphere.” https://t.co/O218eVjrnc

“The solar wind plasma, consisting mostly of protons and a small percentage of doubly charged helium and other heavier ions, populates much of the outer magnetosphere through these processes.” https://t.co/O218eVjrnc

“During northward IMF, high-latitude reconnection over the magnetic poles allows for particle entry to the high-latitude plasma mantle. A minor portion of the energy, estimated to be about 10%, enters via viscous interaction processes.” https://t.co/O218eV

Asymmetry. “While the plasma enters mostly through the dayside magnetopause, a portion of the particles gain entry through the magnetopause boundary layers at low latitudes, well tailward of the terminator.” https://t.co/O218eVjrnc

“The plasma entry is strongly modulated by the orientation of the interplanetary magnetic field, and thus enhanced during periods of southward IMF.” (IMF= interplanetary magnetic field). https://t.co/O218eVjrnc

IMF= interplanetary magnetic field. https://t.co/O218eVjrnc

The solar wind can gain entry into the magnetosphere.” This occurs when the IMF and the magnetospheric fields are antiparallel and magnetic reconnection creates an “open magnetosphere” configuration with a field component normal to the boundary.” https://t

“While the magnetospheric field in general excludes the solar wind plasma from the magnetosphere, at times the solar wind can gain entry into the magnetosphere through the magnetopause.” https://t.co/O218eVjrnc

“This basic flow pattern (in highly variable forms) can always be found underlying the temporal changes associated with the space weather events.” https://t.co/O218eVjrnc

“In the ionosphere, this large-scale convection pattern induces antisunward flow across the polar cap and sunward plasma flow in the auroral region ionosphere.” https://t.co/O218eVjrnc

“Within the tail plasma sheet, the flows are Earthward on the Earthward side of the reconnection region and away from the Earth in the tailward side of the reconnection region .” https://t.co/O218eVjrnc

“At the distant tail reconnection region, plasmas are accelerated toward and away from the reconnection region.” https://t.co/O218eVjrnc

“Dayside reconnection allows solar wind plasma and field entry to the dayside magnetosphere, from where the plasma convects across the polar cap and tail lobes to another reconnection location in the distant tail.” https://t.co/O218eVjrnc

“The solar wind motional electric field in the Earth’s frame of reference imposes a large-scale convection pattern within the magnetosphere and ionosphere.” https://t.co/O218eVjrnc

“An enlargement of the Earth showing the auroral oval, auroral electrojet currents, and the large-scale Region 1 (more poleward) and Region 2 (more equatorward) currents bounding the high-latitude polar cap is shown in the background.” https://t.co/O218eVj

Figure. “Large-scale current systems in the magnetosphere.” https://t.co/O218eVjrnc

“In that system, the x-axis points Sunward along the Sun-Earth line, the z-axis is in the plane containing the Sun-Earth line and the dipole axis and points northward, and the y-axis completes the right-handed triad pointing duskward.” https://t.co/O218eVj

“The geocentric solar magnetospheric coordinate system (GSM) is used in the following discussion.” https://t.co/O218eVjrnc

“The plasma sheet is magnetically connected to the auroral ovals, which encircle the magnetic poles and host continuous, diffuse auroral precipitation in addition to the bright auroral displays associated with events of geomagnetic activity.” https://t.co/

“These field-aligned currents mediate a strong coupling between the ionosphere and the magnetosphere.” https://t.co/O218eVjrnc

“The magnetospheric structure is maintained by intense electric current systems at the magnetospheric boundaries, across the tail plasma sheet, and parallel to the magnetic field lines connecting the ionosphere with various parts of the magnetosphere.” htt

The inner magnetosphere. “The ring current located roughly at 4–6 RE radial distance encircles the Earth with highly variable intensity also modulated by the level of geomagnetic activity.” https://t.co/O218eVjrnc

“In the inner magnetosphere, particles can become trapped on closed orbits drifting around the Earth guided by the quasi-dipolar intrinsic field.” https://t.co/O218eVjrnc

“The inner part of the plasma sheet with its weak field and at times intense cross-tail current sheet is highly variable with bursts of fast flows, magnetic reconnection, and large-scale reconfiguration events.” https://t.co/O218eVjrnc

Mag field. “Thus, while the plasma beta (ratio of plasma and magnetic pressures, β = 2 μ0p/B2) is very low in the tail lobes, it generally exceeds unity at the center of the field reversal region.” https://t.co/O218eVjrnc

Mag field. “The plasma sheet separating the northern and southern lobes hosts densities of the order of 1 cm−3 and partially very low magnetic field values reaching only a few nT.” https://t.co/O218eVjrnc