What is a 'plasmagram'?

The Radio Plasma Imager will produce, as its standard data product, a two- dimensional snapshot of the plasma in the magnetosphere called a plasmagram. These will be updated every 5 minutes during the 2 year mission.

A plasmagram is similar to an ionogram derived from ground-based ionosonds and for more on what ionograms are and how to read them you might visit the National Geophysical Data Center.

Ionosonds receive reflected pulses primarily along one line-of-sight along which the primary transmitter/receiver antenna beam pattern is pointed. The result is a 1-dimensional plot of the ions along the line-of- sight...the ionogram. The vertical axis will indicate the distance to the reflected plasma region, and the horizontal axis will indicate the frequency of the reflected pulse.

For the 'RPI' instrument, it will produce a related two-dimensional plot, with one very important difference. Because the transmission and reflection of the radio waves comes from the full sky, it is impossible to represent 3- dimensional data in an ionogram-format. Each point in the 2-dimensional plasmagram represents the sum of all received echos that have the same delay time and frequency...all over the sky. For convenience, RPI will use the ionogram- style display method for its data, however, researchers will be able to go into the data and extract the full 3-dimensional sky pattern of returned echos at a specific frequency.


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