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How can radar measure the temperature, density, and motion of plasma near Earth?
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Learn about the PHELIX (Petawatt High-Energy Laser for Heavy Ion Experiments) laser at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. PHELIX is used for plasma and atomic physics research.
To measure the properties of plasma in near-Earth space, scientists utilize the incoherent scatter radar method.1
This technique functions by bouncing radio waves off small irregularities within the electron gas, which are caused by the random thermal motions of particles. When the signal returns, it is analyzed for changes compared to the transmitted signal.1
The measurement of these plasma variables is achieved as follows:
- Motion: The returning signal undergoes a shift due to the Doppler-shift effect, allowing researchers to determine the velocity of the plasma and wind speed in space, similar to how police radar detects a speeding vehicle.1
- Temperature and Density: By analyzing the characteristics of the scattered waves, scientists can derive the electron and ion temperatures and densities.1
- Additional Variables: This method can also be used to identify the types of ions present and the electric field within the plasma.1
In the region of geospace, this radar technique typically employs frequencies ranging from 50 to 1,000 megahertz (MHz).1