1. Introduction

From the HPCE data, two types of pool files and a unique set of images for each pool file type are produced. These two types of pool products reflect two distinct philosophies of HPCE instrument operation which lead to two distinct data handling procedures. The two types are referred to as mass average and energy average pool files. The mass average mode nominally occurred for 3 days per month and obtained data using the full instrumental mass resolution. The energy average mode nominally occurred for 27 days per month and obtained data at the maximum energy resolution of the instrument but at only a few (5) mass positions.

In addition during chemical release intervals, limited mass ranges were selected. The images produced during those times are in the mass average format but only limited mass ranges appear. The images are produced over a nominal time period of one orbit (15 hours 39 minutes) per image starting from perigee. The images are always for a period somewhat longer than 1 nominal orbit. Seven images per orbit are produced in the mass average mode. Three images per orbit are produced in the energy average mode. For data obtained after the HPC ceased obtaining ion data on 4 April 1985, the number of images produced in each mode has been reduced to one for each mode for each orbit.

2. Common Features Description

Features common to all images will be documented first. The date and time of the first data sample on the image is given in the upper left and right hand corners. The images are identified by "AMPTE HPCE" in the upper middle.

The HPCE pool file plot software version number is given in the lower right corner as "PV" followed by the version number. Immediately below that is the HPCE pool file generation software version number given as a "V" followed by the version number. Directly below the version numbers are the time (in hours and minutes) and date when the plot file was created.

Across the bottom, four sets of parameters are displayed every 2 hours on even hour marks. First is the Universal Time in hours and minutes. Second is McIlwain's L value (dimensionless). Third is the local time in hours and minutes. Fourth is the magnetic latitude in degrees.

3. Mass Average Images (7)

There are 7 mass average images per orbit (see Plates 1, 2, 3, 4, 5, 6 and 7) . The contents of each image are discussed below, describing each image format individually. Panels on the images are identified on the outline figures of that image format and are numbered consecutively from top to bottom. The outline figures are presented as figures, with Figure 1 displaying the data format for Plate 1.

a. Energy and Angle Spectra Image (1)
Plate 1 , referenced as hpce01, displays the energy and angular distributions versus time for both the total ions (independent of mass) as measured by the energy detector (ED) and for the electrons. Figure 1 is the outline figure for this image format. Two color bars appear on the right side. The upper color bar is used for the ion display while the lower color bar is used for the electron display.
- Panel 1: Ion number flux in (cm sec sr keV/e)**-1 averaged over 6.4 minute intervals as a function of energy in keV versus time. These data have been background corrected.
- Panel 2: Asymmetry parameters for the total ion flux (ED). There are 4 asymmetry parameters, up/down and right/left.
  The up/down asymmetry parameters are calculated by dividing the difference between the number flux at 0 +/- 30 degrees of pitch angle and at 180 +/- 30 degrees of pitch angle by the sum of these two quantities:
```
       j(0 +/- 30 degrees) - j(180 +/- 30 degrees) 
Aud = ---------------------------------------------
       j(0 +/- 30 degrees) + j(180 +/- 30 degrees)
```
  Thus a positive value indicates that the flux over the 60 degree pitch angle sector centered at 0 degrees (particles moving parallel to the magnetic field) exceeds the flux of particles over the 60 degree sector centered on 180 degrees.
  The right/left asymmetry parameters are calculated by dividing the difference between the number flux at 90 +/- 30 degrees and at 270 +/- 30 degrees by the sum of these two quantities:
```
        j(90 +/- 30 degrees) - j(270 +/- 30 degrees)
Alr = ------------------------------------------------
        j(90 +/- 30 degrees) + j(270 +/- 30 degrees)
```
  Thus the right/left asymmetry parameter is positive if the flux over the 60 degree sector centered at 90 degrees pitch angle (particles moving toward the right when looking along the spin axis) exceeds the flux over the 60 degree sector centered at 270 degrees (particles traveling to the left when looking along the spin axis).
  These asymmetry parameters are displayed in the following generic way on 4 horizontal bars or lines. The top bar displays the up/down parameter for high energy ions (100 eV - 1 keV). The range for asymmetry parameters is from +1 to -1. The color code for these parameters is: red=+1, white = 0, green = -1 and ranges smoothly between these values. The second bar is the up/down asymmetry parameter for the low energy ions (less than 100 eV). The middle bar is left blank to serve as a separator and appears black. The fourth bar is the right/left parameter for high energy ions (100 eV - 1 keV as above). The fifth and last bar is the right/left asymmetry parameter for low energy ions (less than 100 eV as above).
- Panel 3: Ion background converted to number flux for each 6.4 minute interval and mapped to the ion color bar (upper color bar).
- Panels 4, 5 and 6: Ion number flux versus pitch angle for ions divided into the three energy ranges 4 - 18 keV, 1 - 4 keV and 0 - 1 keV, respectively. The pitch angle range used is 0 - 90 degrees; this range was obtained by folding over pitch angles in the range 0 - 360 degrees in a saw tooth fashion.
- Panel 7: Left blank as a separator and appears black.
- Panels 8 and 9: Contain no data in the mass average mode. This image format ( Figure 1 ) is common to both the mass average and energy average modes but appropriate data to fill these panels exists only in the energy average mode and then only in certain sub-modes. When data coverage exists for a 6.4 minute average but data of the appropriate type for that particular display is not present, a gray background appears. When no data is sampled during the average, a black background is used. In panel 9 two lines composed of small white rectangles is displayed. For one line the rectangles are oriented longer in the horizontal axis and the data varies more smoothly; these represent the minimum ram angle. For the other line, the rectangles are oriented vertically and the data varies more rapidly; these represent the pitch angle at the time of the minimum ram angle. The angle range used in this panel is 0 to 360 degrees.
- Panel 10: Another black separator panel.
- Panel 11: Electron energy flux in keV/(cm**2 sec sr keV) mapped to the electron color bar (lower color bar). The energy scale is in units of keV, ranging from 0 to 25 keV.
- Panel 12: Electron asymmetry parameters in the same display format as described for Panel 2 above.
- Panels 13, 14 and 15: Electron angular distributions divided into 3 energy bands, 4 - 25 keV, 1 - 4 keV and 0 - 1 keV respectively.
- Panel 16: Unused.
b. Mass Spectra Images (6)
There are 6 images containing HPCE energy/mass spectrograms completing the set of 7 mass average images. These 6 images , referenced as hpce02 through hpce07, have a similar format which will be described only once below. First the organization of, and differences between, the 6 images will be described. Figure 2 is the outline for this image format for reference. Plates 2, 3, 4, 5, 6 and 7 are one complete set of mass spectra data.
The mass spectra are accumulated over 32 minute intervals. Each spectrum is displayed for the complete orbit, 11 spectra for the first 2 images and 10 spectra for the third image. Additionally, these spectra were accumulated for those ions parallel to the magnetic field line (pitch angle 45 degrees or less) and for those perpendicular to the magnetic field line (pitch angle between 45 and 135 degrees). This yields two sets of 3 images for a total of 6 images per orbit.
For identification of the type of data (parallel ions versus perpendicular ions), the parallel and perpendicular symbols are displayed in the lower right side of the images just above the version numbers.
The similar format for these 6 images is to display each mass/energy spectrogram twice, once on the left (panels 1A - 11A), using the color bar in the middle, and once on the right (panels 1B - 11B) using the color bar to the right side of the image. This allows each spectrum to be displayed with different scales to expand the dynamic range. The horizontal axis is the mass axis for each panel and is in units of mass steps (MS) ranging from 1 at the left to 64 at the right side of the panel. The relationship between the mass step and the mass per charge of the ion (M/Q) is
```
       M/Q = 0.848/[1 - ((MS - 1)/64)]**2
```
The vertical axis is the ion energy in keV ranging from 0 to 17 keV.
The times of each mass/energy spectrogram 32-minute interval are identified by an alphabetic character or a number up to 5. This character is displayed at the left side of each spectrogram and is related to universal time in the orbit by panel 15. Panel 14 is a black separator panel. Panel 13 is the ion total background converted to number flux for each 6.4 minute interval.

4. Release Interval Data
Plate 8 is an example of data taken in a special mode used during chemical release intervals. Data for these intervals are displayed in the mass spectra format but only subsets of the mass range were covered.

5. Energy Average Images (3)
Three images per orbit are produced from energy average pool files. The first image , referenced as hpce01, displays energy-time spectrograms for each of 5 species: H+, O+, He+, He++ and O++ (panels 1, 3, 5, 7 and 9 on Figure 3). The energy range is from 0 to 17 keV. Immediately below the spectrogram for each species is displayed the asymmetry parameters for that species as described in 3a (panels 2, 4, 6, 8 and 10). Finally panel 11 shows the MD background converted to number flux and displayed according to the color bar shown at the right side of the image (see Figure 3 and Plate 10) .
The second energy average image (outline on Figure 4, data on Plate 11) , referenced as hpce02, displays the hydrogen (H+, panels 1, 2 and 3) and oxygen (O+, panels 6, 7 and 8) number fluxes as a function of pitch angle over a range of 0 to 90 degrees for each of 3 energy bands (4 - 18 keV, 1 - 4 keV and 0 - 1 keV). The panel immediately below the 0 - 1 keV energy band (panels 4 and 9 for H+ and O+ respectively) displays for each ion the asymmetry parameters for that ion as described in 3a. Panel 11 is the MD background converted to number flux for display purposes only and displayed according to the color bar shown at the right side of the image.
The third energy average image (outline on Figure 1, data on Plate 9) , referenced as hpce03, is the same as that described for the first mass average image in 3a (Energy and Angle Spectra Image) with the exception that the two middle panels for ED1 RPA (Retarding Potential Analyzer) data will sometimes be filled. When appropriate data exists, the number flux for 7 differential RPA channels is displayed first as a function of energy in panel 8 and then as a function of pitch angle in panel 9.

1. Introduction

2. Common Features Description

3. Mass Average Images (7)

4. Release Interval Data

5. Energy Average Images (3)