ANTARCTICA (above) / Aug.29, 2018. This detail is off AMERY ICE SHELF. The contrast etc. maxed to reveal miles of cracking ice chunks. https://go.nasa.gov/2LJ2QFG
ANTARCTICA (above) / Aug.29, 2018. AMUNDSEN SEA area, contrast etc. enhanced. https://go.nasa.gov/2NrCDNk
ANTARCTICA (above) / Aug.29, 2018. AMUNDSEN SEA area, contrast etc. enhanced. https://go.nasa.gov/2MzPpwV
The Atmosphere and Ionosphere: Elementary Processes, Discharges and Plasmoids
Chapter 4 / Electromagnetic Drivers in the Upper Atmosphere: Observations and Modeling
A.A. Namgaladze, M. Fo ̈rster, B.E. Prokhorov, and O.V. Zolotov
This chapter presents and discusses some of the most recent measurements obtained by the Electron Drift Instrument (EDI) on “Cluster”, the accelerometer on board the low-Earth-orbiting satellite CHAMP, and global maps of total electron content (TEC) gathered by the fleet of GPS satellites. It aims at a better understanding of the globally interconnected complex plasma physical and electrodynamic processes of the Earth’s upper atmosphere by means of first-principle numerical modeling using the Upper Atmosphere Model (UAM).
The study results show ionospheric electric fields, generated by magnetospheric and seismogenic sources, and reveal their influence on the thermospheric dynamics and the TEC (total electron count) pattern. UAM simulations of the thermospheric neutral wind at high latitudes are compared with CHAMP observations for varying interplanetary magnetic field (IMF) conditions on 28 October 2003, the day before the famous Halloween superstorm of the previous solar cycle.
The simulations show the immediate response of the upper atmosphere and its high sensitivity to IMF changes in strength and orientation. Investigation of the ‘lithosphere–atmosphere– ionosphere’ coupling problem allowed statistically describing GPS-measured TEC variations treated as precursors to earthquakes as (1) anomalous strong (30–90% and more) TEC-positive or -negative deviations relative to the quiet conditions before the forthcoming seismic event, not less than M5 by magnitude, linked to the near-epicenter area. (2) The typical zone of the anomaly maximum manifestation extends more than 1,500 km in latitude and 3,500–4,000 km in longitude. (3) Anomaly living time is from several hours or days to couple of weeks before the earthquake release moment. (4) Analogous effects at the magnetically conjugated area are often reported. (5) In the case of strong low-latitudinal earthquakes, there are effects related to the modification of the ionospheric F2-region equatorial anomaly.
From the analysis of the TEC deviations before a few strong recent seismic events (12 January 2010, Haiti; 1 and 2 January 2011, Argentina and Chile; 11 March 2011, Japan), these pre-earthquake TEC signatures are extended with terminator and ‘ban’-time effects. We strongly believe that the main reason for the appearance of these TEC anomalies is the vertical drift of F2-region ionospheric plasma under the influence of a zonal electric field of seismic origin.
Increase of the atmospheric radioactivity level during earthquake preparation leads to enlargement of the ionization and electric conductivity of the near-ground atmosphere. Another (and possibly more effective) ionization mechanism proposed is the so-called positive holes effect.
Changes of resistance of the underlying atmosphere lead to the generation of an external electric current flowing between the Earth and the ionosphere and to the corresponding disturbances of the ionospheric electric field and TEC. These disturbances were modeled by UAM and compared with the GPS TEC observations. Comparison shows satisfactory agreement between the model and observations. Methodical recommendations for detection of ionospheric earthquake precursors are given.
Keywords High-latitude ionospheric convection • Thermospheric neutral wind • Magnetosphere-ionosphere-thermosphere (MIT) coupling • Upper Atmosphere Model (UAM) • Solar wind and IMF influence • Ionospheric currents • Global total electron content (TEC) pattern • Seismogenic ionospheric effects • Earthquake precursors
ANTARCTICA (above) / Aug.29, 2018. The BELLINGSHAUSEN SEA area. Contrast & saturation adjusted. Color is a result of the adjustments and not natural. https://go.nasa.gov/2wsIADa
ANTARCTICA (above) / Aug.29, 2018. The BALLENY ISLANDS (below McMurdo Station). Contrast etc. maxed https://go.nasa.gov/2NEdjUE
ANTARCTICA (above) / Aug.29, 2018. The BALLENY ISLANDS (below McMurdo Station). Contrast etc. maxed.
The weather, climate, and space weather (processes related to solar and geomagnetic activity) and their forecasting are extremely important for mankind. Observations and mathematical modeling used together are the modern ways for solving the forecasting needs. Modern first-principle numerical models are time dependent, three dimensional (3D), and global.
Until recent years these models were being developed for the lower atmosphere (responsible for the weather and climate; heights <100 km) and upper atmosphere (responsible for space weather; heights >100 km) separately, despite the lack of any boundary between these two atmospheric regions. Their principal physical difference consists of the amount of the charged particles, the ions and electrons, that is, in their concentration (number density), which is high in the upper atmosphere and low in the lower. Therefore, electrodynamic processes are very important in the upper atmosphere (thermosphere, ionosphere, and magnetosphere).
However, electrodynamic processes are important in the lower and middle atmosphere (troposphere, stratosphere, and mesosphere) as well because of the existence of such lower atmosphere electricity sources as cosmic rays, thunderstorms, soil radioactivity, and seismodynamic effects. The lower atmosphere electric currents are connected with the ionospheric electric currents so that they are closely related to the magnetospheric currents, creating a common global electric circuit. This circuit consists of currents flowing upward from thunderstorm current generators, through the ionosphere, and down to the Earth’s surface as fair-weather currents. The vertical fair-weather current between the ionosphere and the Earth is about 2–3 pA/m2 and the total global current is about 1 kA, producing a potential difference of about 250–300 kV between the ionosphere and the Earth.
The horizontal potential difference in the ionosphere may reach 100–150 kV (usually 30–50 kV) between the morning and evening sides of the polar cap boundaries at the polar edges of the auroral zones (at about 75ı magnetic latitude) in both Northern and Southern Hemispheres. The cross-polar cap potential difference (or drop) is the commonly used characteristic of the high-latitude ionospheric electric fields. Its dependences on solar and geomagnetic activity have been investigated by many authors and used as input in electric field calculations of the model.
This potential difference is generated at the magnetopause under the solar wind–magnetosphere interaction and transported into the polar ionosphere along the geomagnetic field lines via so-called field-aligned currents (FACs) of Region-1. They flow down into the ionosphere at the dawn side and up from the ionosphere at the dusk side, creating electric fields of several tens or even hundreds of mV/m in the polar caps directed from dawn to dusk. FACs of opposite signs flow at the equatorial edges of the auroral zones (Region-2 FACs). These currents shield the inner magnetosphere and the mid-latitude ionosphere from penetrating magnetospheric electric fields. This shielding and the presence of internal atmospheric dynamo processes results in smaller mid-latitude electric fields (of about several mV/m) in comparison with the high-latitude and subauroral ones.
Region-0 FACs are found during intervals of a strictly positive Bz-component of the interplanetary magnetic field (IMF). They may exist in the vicinities of the cusps. The IMF By-component is responsible for the asymmetry of the morning and evening cells of the ionospheric convection (plasma drift trajectories). The intensity of the FACs and the corresponding cross-polar cap potential drops (or the electric field strength) are well correlated with the southward IMF Bz -component, which can trigger magnetospheric substorm and storm generation processes.
Another source of ionospheric electric fields is the dynamo action of the thermospheric winds pushing ions across the geomagnetic field lines at ionospheric E- and F1-region heights (100–170 km), where electrons are magnetized (electron- neutral collision frequency en ̋e – electron cyclotron frequency) but ions are not (ion-neutral collision frequency in ̋i – ion cyclotron frequency). For this reason, this height region is referred to as the dynamo region. Horizontal ionospheric currents of the upper atmosphere flow predominantly in this height range.
In the ionospheric F2-region and above it (heights >170 km), both electrons and ions are magnetized ( en, in ̋e, ̋i) and electric currents flow first and foremost along the geomagnetic field lines (FACs), which conduct well; exceptions are plasma drift processes in the magnetosphere, like pressure gradient-driven currents. Because of the high electrical conductivity of the geomagnetic field lines, they can be assumed to be electrical equipotentials, so that electric fields along these lines are zero or very small. Electric fields at heights >170 km are therefore almost always perpendicular to the geomagnetic field lines. These mutually perpendicular electric (E) and magnetic (B) fields force the ionospheric plasma to move with the so-called E B plasma drift velocity (equal to E B/B2 ), that is, in the direction perpendicular to both. In this drift motion, ions and electrons move together with the same velocity; that is, there is no charge separation and they do not create electric currents.
Furthermore, there exists the so-called co-rotation electric field induced by the rotation of the Earth and its atmosphere around the geodetic axis. In the equatorial plane, this electric field is directed toward the Earth’s center and causes the magnetized ionospheric plasma to rotate together with the Earth (to drift with the Earth’s rotation velocity).
ANTARCTICA (above) / Aug.30, 2018. The Ross Sea area with contrast etc. enhanced. https://go.nasa.gov/2wtcneT
ANTARCTICA (above) / Aug.30, 2018. The AMUNDSEN SEA area with the contrast etc. adjusted. https://go.nasa.gov/2LIJsby
ANTARCTICA (above) / Aug.30, 2018. The AMUNDSEN SEA area with the contrast etc. adjusted.
Global electric field patterns obtained mainly from satellite measurements are usually presented as polar maps of electric potential distributions for different magnetic activity levels and/or different IMF orientations. We show and discuss some of the recent data in Sect. 4.3 of this chapter.
Ionospheric E B plasma drifts cause many important peculiarities of the spatial and time variations of the ionospheric plasma, such as the formation of the equatorial anomaly, the main ionospheric trough, the plasmasphere, and ionospheric disturbances related to magnetic storms and substorms.
At high and sub-auroral latitudes (where the geomagnetic field inclination I is near 90ı–60ı), the ionospheric plasma drifts affect electron density mainly because of the divergence/convergence of the horizontal plasma flows. The daytime plasma, having high density, can thus flow across the polar caps to the night side, increasing the density there. Plasma motion will stagnate where the magnetospheric convection and the co-rotation are oppositely directed with about the same velocity magnitudes. If this occurs outside the sunlit region, the plasma will be lost because of recombination processes to very low density values, forming the so-called main ionospheric trough in the dark winter ionosphere at subauroral latitudes.
At middle to low latitudes, the plasma co-rotation with the Earth leads to the formation of the plasmasphere. At these latitudes (where inclination I is small) the vertical plasma drifts also become important. Close to the equator, they cause the so- called fountain effect, forming the equatorial anomaly. At middle latitudes, they can create increases or decreases of electron density by lifting the plasma up or down the geomagnetic field lines to heights where the ion loss rate is lower or higher, respectively.
Both the ionospheric plasma drifts and the electric currents influence ion and neutral temperatures (Joule heating) via ion-neutral collisions.
ANTARCTICA (above) / Aug.30, 2018. The BELLINGSHAUSEN SEA area. Contrast & saturation adjusted. Color is a result of the adjustments and not natural. https://go.nasa.gov/2MDiuaR
ANTARCTICA (above) / Aug.30, 2018 / the AMERY ICE SHELF area with the contrast & saturation etc. maxed. https://go.nasa.gov/2wtWG7r
ANTARCTICA (above) / Aug.30, 2018 / the AMERY ICE SHELF area with the contrast & saturation etc. maxed. Note the hundreds of miles of ‘spiral-coils’ evidence of scalar wave charged cloud formations.
ANTARCTICA (above) / Aug.30, 2018 / the AMERY ICE SHELF area with the contrast & saturation etc. maxed. Note the hundreds of miles of ‘spiral-coils’ evidence of scalar wave charged cloud formations. I used some enhancement for clarity. “For plasmas, there is a neutral force region where filaments do not merge, but rather start a rotational motion around each other to form a vortex-like geometry.” [‘Physics of the Plasma Universe’ by Anthony L. Peratt, Springer, 2015.] https://go.nasa.gov/2Nwf6e1
Thermospheric wind circulation changes the thermospheric gas composition, which in turn influences the ionospheric ion composition and electron density and so forth. The plasma physical processes within the near-Earth space environment as well as the interactions between the various regions appear to be highly complex.
To understand the dynamics of the whole system with all its interrelationships at various levels of complexity is one of the most important reasons to use first-principle models for their description. They allow us to perform “numerical experiments” and to interpret different measurements on a common basis, which may be obtained at various places far from each other by both ground-based observations and remote or in situ data gathering with satellites.
This chapter presents and discusses some of the most recent measurements of the near-Earth environment obtained by Cluster, CHAMP, and the global positioning system (GPS) satellites and their modeling in the framework of the Upper Atmosphere Model (UAM). The results concern ionospheric electric fields, generated by magnetospheric and seismogenic sources, and show their influence on the thermospheric dynamics and the ionospheric total electron content (TEC).
ANTARCTICA (above) / Aug.31, 2018. The BELLINGSHAUSEN SEA area. Contrast & saturation adjusted. Color is a result of the adjustments and not natural. https://go.nasa.gov/2MDiuaR