Download Coupling between the Crust and the Ionosphere prior to Earthquakes

Coupling between the Crust and the Ionosphere prior to Earthquakes
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Friedemann Freund , Yvonne Cagle , Brian Shiro , Stuart Pilorz , Phillip Hollis-Watts , Chris Windsor
1. NASA Ames Research Center, 2. SETI Institute, 3. NOAA Pacific Tsunami Warning Center,
4. Astronauts4Hire, 5. Western Australia School of Mines (contact: [email protected])
Introduction. When tectonic stresses build up in
the Earth’s crust prior to major earthquakes,
electronic charge carriers are activated in the
stressed rocks. The charge carriers of interest are
defect electrons in the oxygen anion sublattice of
rock-forming minerals, known as positive holes,
symbolized by h• [1].
The h• have the remarkable ability to spread out of
the stressed rocks into the surrounding unstressed
rocks, traveling fast and far, meters in the
laboratory, tens of kilometers in the field. Upon
arrival at the Earth surface in sufficiently large
numbers, they cause air molecules to become
field-ionized, causing the injection of massive
amounts of airborne ions at the ground-to-air
interface, sometimes exclusively positive [2].
Atmospheric Effects. The air volume heavily
laden with positive ions expands upward, probably
to stratospheric heights, dragging along Earth’s
ground potential (Figure 1). In response to the
changing vertical electric field the ionospheric
plasma responds by increasing the Total Electron
Content (TEC) at its lower edge [3].
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toward the ionosphere, forming a distributed ion
current through the mesosphere [4]. Likewise
electrons will be accelerated downward from the
lower edge of the ionosphere. These vertical
currents will couple to the Earth’s magnetic field,
forcing the ions and electrons onto spiraling
trajectories. At some critical current density
magneto-hydro-dynamic theory predicts that the
smooth, distributed currents will break up into
bunches, forming bubbles of higher charge
densities separated by regions of lower charge
densities or of opposite sign. This will result in
strong electric fields causing electric discharges in
the mesosphere.
Ground Observations. Evidence for bursts of
millisec discharges over regions of impending
earthquake activity in SW Australia, Indonesia and
the South Pacific – and over active volcanoes
undergoing a Plinian eruption – has been obtained
by Hollis-Watts at Perth, Australia, using a
directional antenna recording signals over a wide
frequency range, from 10 kHz to 1.3 GHz [5]. The
signals and their polarization are consistent with
mesospheric lightning strikes.
Conclusion.
We propose to use suborbital
vehicles to traverse the mesosphere during times
of such electric activity to measure (i) electric fields
along the flight path, (ii) ion concentrations, (iii)
electron concentrations.
References.
[1] Freund, F. T. (2010), Towards a unified solid
state theory for pre-earthquake signals, Acta
Geophysica, 58, 719-766.
[2] Freund, F. T., et al. (2009), Air ionization at rock
surface and pre-earthquake signals, J. Atmospheric
Solar Terrestrial Physics, 71, 1824–1834.
Figure 1: Injection of positive airborne ions at the
•
ground-to-air interface, due to stress-activated h
charge carriers arriving at the Earth surface from
below, and upward expansion of the ionized air,
causing a response in the ionospheric plasma.
We predict that positive air ions at the upper edge
of the stratosphere will be accelerated upward
[3] Liu, J. Y., et al. (2004), Pre-earthquake ionospheric anomalies registered by continuous GPS
TEC measurements, Annales Geophysicae, 22,
1585-1593.
[4] Pulinets, S., and K. Boyarchuk (2004),
Ionospheric Precursors of Earthquakes, 350 pp.,
Springer, Heidelberg.
[5] Pulinets, S., and P. Hollis-Watts (2003), P-H
pulses - the new type of seismoelectromagnetic
emission, Geophysical Research Abstr., 5, 07035.