Description of the Hot Plasma Survey Plot

The Hot Plasma analyzer measures the intensities of electrically charged particles as functions of particle energy and direction. Measurements of electrons and positive ions are acquired simultaneously. This analyzer is one element of the Comprehensive Plasma Instrumentation (CPI) on board the Geotail spacecraft. Detailed descriptions of the Hot Plasma analyzer (HP), the Solar Wind analyzer (SW), the Ion Composition analyzer (IC), and the associated electronics package that comprise the Comprehensive Plasma Instrumentation are provided in the Description of Instrumentation.

Measurements from the Hot Plasma analyzer are available at this Web site in a graphical survey format. This format is designed to provide convenient access to the observations. Each survey plot is a five-day record of the electron and ion intensities and several parameters derived from those intensities. The measurements are given in a sequence of five panels. From top to bottom the panels display:

1. N [cm^-3], the ion number density.
2. V_X [km/s], the component of the ion bulk-flow velocity along the Earth-Sun line. Positive flow is towards the sun.
3. T_i and T_e"> [K], the respective temperatures of ions and electrons.
4. The intensities of positive ions as a function of particle energy.
5. The intensities of electrons as a function of particle energy.

The particle intensities given in panels 4 and 5 are five-minute accumulations from the ion and electron sensors that view the ecliptic plane. This plane is perpendicular to the spin axis of the spacecraft, and the intensities are summed over eight equally spaced spin sectors. The particle intensities are color coded according to the logarithmic color bar on the right-hand side of the figure which has separate scales for ions and electrons. Particle energies-per-charge (E/Q, Volts) are indicated by the logarithmic scale on the ordinates of the ion and electron panels. Dates corresponding to the major tick marks on the abscissa are shown at the bottom of the display. Minor tick marks are given at four-hour intervals. The projection of the Geotail orbit in the ecliptic plane is shown for reference at the top of the display. The beginning of each day is marked with a dot, and the first day of the five-day sequence is highlighted.

The plasma parameters given in the first three panels of the survey display are computed for particles with energies-per-charge in the range 50 V to 48 kV. The ions are assumed to be protons. The parameters are computed using five-minute accumulations from the electron and ion sensors that view the ecliptic plane. Thus, the number density, the V_X component of the flow, and the temperatures given here are equivalent to those that would be gained with a two-dimensional plasma analyzer.