From UPSC perspective, the following things are important :
Prelims level : Ionosphere, CIP
Mains level : Relation between atmosphere and seismic activity
Scientists of Indian Institute of Geomagnetism (IIG) an autonomous institution of the DST have extensively studied the signatures of recent large earthquakes into the ionosphere with an ambitious aim to derive the seismic source characteristics from the ionosphere.
- The research is a part of the interdisciplinary program ‘Coupled Lithosphere-Atmosphere- Ionosphere-Magnetosphere System (CLAIMS)’ of IIG.
- CLAIMS focuses on energy transfer to the atmosphere during solid Earth processes such as earthquakes as well as tsunamis.
Key terms: Co-seismic Ionospheric Perturbations (CIP)
- In general, the Earth crust uplift during an earthquake produces compressional (i.e. pressure) waves in the overlying atmosphere.
- These waves propagate upward in the region of exponentially decreasing atmospheric neutral density, and thus, wave amplitude increase with atmospheric heights.
- On arrival at ionospheric heights, the waves redistribute ionospheric electron density and produce electron density perturbations (disruption) known as CIP.
Objective of CLAIMS
- The spatial distribution of near field co-seismic Ionospheric perturbations (CIP) associated with this event could reflect well the ground deformation pattern evolved around the epicentre.
- These CIPs were derived using the Global Positioning System (GPS) measured Total Electron Content (TEC).
- The CIP distribution was estimated at Ionospheric piercing point (IPP) altitude.
Other factors affecting CIP
The major effective non-tectonic forcing mechanisms at ionospheric altitudes are the-
- orientation between the ambient geomagnetic field and seismic induced neutral wave perturbations.
- orientation between the moving satellite line of sights and the wave perturbations.
- ambient ionospheric electron density gradient.
- The ionosphere is the ionized part of Earth’s upper atmosphere, from about 60 km to 1,000 km altitude.
- It is a region that includes the thermosphere and parts of the mesosphere and exosphere.
- It is ionized by solar radiation.