PEM LEVEL 3 DATA QUALITY DOCUMENT Instrument: PEM Version No.: 1.0 Date: 02-02-94 Commonly Asked Questions: Q: What type of PEM data is available on the DAAC? A: Energy Deposition data known in the UARS world as Level 3 data. This means that the PEM measurements have been processed to determine how much particle energy is available to the atmosphere. PEM data exists in component files known as 3at and 3tp files. The level 3at files are time based and are defined as follows: (a) 16 different files created from AXIS X-Ray inversion, (b) one file for electrons from HEPS and MEPS measurements, and (c) one file for protons from HEPS and MEPS measurements. PEM also includes Level 3tp files on the DAAC which are the detailed energy deposition profiles from the individual particle instruments. All files are briefly described below. A more detailed explanation of these files, how computations are made, and their usage are included in the SFDU documents. Q: What type of calculations are made in computing the PEM particle profiles? A: Particle energy deposition profiles are generated by a range-energy CSD (continuous slowing down) type of calculation with pre-computed energy deposition profiles in a look up table format. The particle data is used to adjust the profile to the appropriate intensity. Each particle profile is precomputed for a specific energy, and at angular shapes for the electron distribution or discrete pitch angle values for the proton distribution. Q: What is the basis for computing the electron energy deposition? A: Electron energy loss functions of range and initial energy are interpolated from the J-function tables produced by Spencer (National Bureau of Standards, Monograph 1, 1959). These values are mapped along the geomagnetic field from the satellite altitude and converted to the energy deposition profile using the 1976 U.S. Standard Atmosphere. These profiles are adjusted (according to the parameterization provided by Lummerzheim) for the shape of the electron pitch angle distribution and used as the look up table values. Spencer's J-functions include a solution of the continuous-loss transport equation which includes elastic scattering. Q: What is the basis for computing the proton energy deposition? A: Proton energy loss functions of path length and initial energy are interpolated from the the data tables produced by Janni (Atomic & Nuclear Data Tables, V 27, No. 2/3, 1982). These values are mapped along the geomagnetic field from the satellite altitude and converted to the energy deposition profile using the 1976 U.S. Standard Atmosphere. These profiles are computed for specific pitch angles which are 10 degrees apart starting at 5 degrees. For protons greater than 1 MeV, fully relativistic Bethe equation corrected for polarization effect and for the nonparticipation of inner-shell electrons is used by Janni. From 1 MeV to 20 keV, a statistically weighted least squares polynomial fit to available published energy loss data was used. Below 20 keV, Theoretical energy loss to electrons and elastic nuclear collisions normalized to fit the slope and magnitude of the total energy loss at 20 keV obtained from experimental data was used. Thus, the effects accounted for are: atomic electron straggling, elastic nuclear straggling, charge exchange straggling, total path length straggling, and multiple-scattering. ******************************************************************************* File: 3AT X-Rays (AXIS) Subtypes: EDEP3AT_P01, EDEP3AT_P02, EDEP3AT_P03, EDEP3AT_P04, EDEP3AT_P05, EDEP3AT_P06, EDEP3AT_P07, EDEP3AT_P08, EDEP3AT_P09, EDEP3AT_P10, EDEP3AT_P11, EDEP3AT_P12, EDEP3AT_P13, EDEP3AT_P14, EDEP3AT_P15, EDEP3AT_P16 Description: Energy Deposition by Electrons from Inverted AXIS X-Rays Accumulation Time: 1 UARS minute (dictated by project) (65.536 sec.) Parameter No. 1: Energy Deposition by Electrons Generated from Inverted X-Rays Alt. Range: 5 km - 400 km (grid defined by project) Parameter Units: keV/(g-s) Est. Precision of Parameter: 3 Digit Est. Accuracy of Parameter: see Parameter 2 Resolution of Parameter: Variable Systematic Effects: Caveats: Parameter No. 2: Standard Deviation in the Energy Deposition by Electrons Generated from X-Rays Alt. Range: 5 km - 400 km (grid defined by project) Parameter Units: keV/(g-s) Est. Precision of Parameter: 3 Digit Est. Accuracy of Parameter: Model and Fit Dependent Resolution of Parameter: Variable Systematic Effects: Caveats: ******************************************************************************* File: 3AT Electrons (HEPS and MEPS) Subtype: EDEP3AT_ELEC Description: Energy Deposition by Both HEPS and MEPS Electrons Accumulation Time: 1 UARS minute (dictated by project) (65.536 sec) Parameter No. 1: Energy Deposition by Electrons Alt. Range: 5 km - 400 km (grid defined by project) Parameter Units: erg/(cm**3-s) Est. Precision of Parameter: 3 Digit Est. Accuracy of Parameter: see Parameter 2 Resolution of Parameter: Variable Systematic Effects: (1) Zero values mean no parameter computed. (2) No angular dependence has been included in the spectrum; the data is taken to be isotropic. (3) Waviness in the profile results from sparseness of sampled energies. Caveats: (1) Data is reported from both HEPS and MEPS electrons only. (2) Data gaps may be caused by data not available from both instruments, look in electron 3tp files for individual instrument resolutions. (3) Result dependent on atmospheric model, 1976 US Standard Atmosphere used. (4) High energy data was fitted to a double power law. It may not reflect intense precipitation accurately. Parameter No. 2: Standard Deviation in the Energy Deposition by Electrons Alt. Range: 5 km - 400 km (grid defined by project) Parameter Units: erg/(cm**3-s) Est. Precision of Parameter: 3 Digit Est. Accuracy of Parameter: Model and Fit Dependent Resolution of Parameter: Variable Systematic Effects: (1) Zero values mean no parameter computed. (2) No angular dependence has been included in the spectrum; the data is taken to be isotropic. (3) Waviness in the profile results from sparseness of sampled energies. (4) A negative value of standard deviation indicates a region in which the fit to the data exceeds the fit to the sum of the data plus error. Caveats: (1) Data is reported from both HEPS and MEPS electrons only. (2) Data gaps may be caused by data not available from both instruments, look in electron 3tp files for individual instrument resolutions. (3) Result dependent on atmospheric model, 1976 US Standard Atmosphere used. (4) High energy data was fitted to a double power law. It may not reflect intense precipitation accurately. ******************************************************************************* File: 3AT Protons (HEPS and MEPS) Subtype: EDEP3AT_PROT Description: Energy Deposition by Both HEPS and MEPS Protons Accumulation Time: 1 UARS minute (dictated by project) (65.536 sec) Parameter No. 1: Energy Deposition by Protons Alt. Range: 5 km - 400 km (grid defined by project) Parameter Units: erg/(cm**3-s) Est. Precision of Parameter: 3 Digit Est. Accuracy of Parameter: see Parameter 2 Resolution of Parameter: Variable Systematic Effects: (1) Zero values mean no parameter computed. (2) No angular dependence has been included in the spectrum; the data is taken to be isotropic. (3) Waviness in the profile results from sparseness of sampled energies. (4) Only those HEPS sensors having a corresponding LEP unit are used. Caveats: (1) Data is reported from both HEPS and MEPS protons only. (2) Data gaps may be caused by data not available from both instruments, look in proton 3tp files for individual instrument resolutions. (3) Result dependent on atmospheric model, 1976 US Standard Atmosphere used. (4) High energy data was fitted to a double power law. It may not reflect intense precipitation accurately. Parameter No. 2: Standard Deviation in the Energy Deposition by Protons Alt. Range: 5 km - 400 km (grid defined by project) Parameter Units: erg/(cm**3-s) Est. Precision of Parameter: 3 Digit Est. Accuracy of Parameter: Model and Fit Dependent Resolution of Parameter: Variable Systematic Effects: (1) Zero values mean no parameter computed. (2) No angular dependence has been included in the spectrum; the data is taken to be isotropic. (3) Waviness in the profile results from sparseness of sampled energies. (4) A negative value of standard deviation indicates a region in which the fit to the data exceeds the fit to the sum of the data plus error. (5) Only those HEPS sensors having a corresponding LEP unit are used. Caveats: (1) Data is reported from both HEPS and MEPS protons only. (2) Data gaps may be caused by data not available from both instruments, look in proton 3tp files for individual instrument resolutions. (3) Result dependent on atmospheric model, 1976 US Standard Atmosphere used. (4) High energy data was fitted to a double power law. It may not reflect intense precipitation accurately. ******************************************************************************* File: 3TP Electrons (HEPS) Subtype: HEPS_ELEC_ED Description: Energy Deposition by HEPS Electrons Only Accumulation Time: 1 UARS minute (65.536 sec) Parameter No. 1: Energy Deposition by Electrons Alt. Range: 5 km - 400 km (grid defined by project) Parameter Units: erg/(cm**3-s) Est. Precision of Parameter: 3 Digit Est. Accuracy of Parameter: see Parameter 2 Resolution of Parameter: Variable Systematic Effects: (1) Zero values mean no parameter computed. (2) No angular dependence has been included in the spectrum; the data is taken to be isotropic. (3) Waviness in the profile results from sparseness of sampled energies. Caveats: (1) Data is reported from only HEPS electrons. Caution should be used interpreting data above 100 km because MEPS electrons are not included. (2) Data gaps are most likely caused by no sensor included within the loss cone. (3) Result dependent on atmospheric model, 1976 US Standard Atmosphere used. (4) High energy data was fitted to a double power law. It may not reflect intense precipitation accurately. Parameter No. 2: Standard Deviation in the Energy Deposition by Electrons Alt. Range: 5 km - 400 km (grid defined by project) Parameter Units: erg/(cm**3-s) Est. Precision of Parameter: 3 Digit Est. Accuracy of Parameter: Model and Fit Dependent Resolution of Parameter: Variable Systematic Effects: (1) Zero values mean no parameter computed. (2) No angular dependence has been included in the spectrum; the data is taken to be isotropic. (3) Waviness in the profile results from sparseness of sampled energies. (4) A negative value of standard deviation indicates a region in which the fit to the data exceeds the fit to the sum of the data plus error. Caveats: (1) Data is reported from only HEPS electrons. Caution should be used interpreting data above 100 km because MEPS electrons are not included. (2) Data gaps are most likely caused by no sensor included within the loss cone. (3) Result dependent on atmospheric model, 1976 US Standard Atmosphere used. (4) High energy data was fitted to a double power law. It may not reflect intense precipitation accurately. ******************************************************************************* File: 3TP Electrons (MEPS) Subtype: MEPS_ELEC_ED Description: Energy Deposition by MEPS Electrons Only Accumulation Time: 2 UARS seconds (2048 msec) Parameter No. 1: Energy Deposition by Electrons Alt. Range: 5 km - 400 km (grid defined by project) Parameter Units: erg/(cm**3-s) Est. Precision of Parameter: 3 Digit Est. Accuracy of Parameter: see Parameter 2 Resolution of Parameter: Variable Systematic Effects: (1) Zero values mean no parameter computed. (2) No angular dependence has been included in the spectrum; the data is taken to be isotropic. (3) Waviness in the profile results from sparseness of sampled energies. Caveats: (1) Data is reported from only MEPS electrons. Caution should be used interpreting data because HEPS electrons are not included. (2) Data gaps are most likely caused by either no sensor included within the loss cone or the spacecraft is charged and MEPS data is not reliable. (3) Result dependent on atmospheric model, 1976 US Standard Atmosphere used. Parameter No. 2: Standard Deviation in the Energy Deposition by Electrons Alt. Range: 5 km - 400 km (grid defined by project) Parameter Units: erg/(cm**3-s) Est. Precision of Parameter: 3 Digit Est. Accuracy of Parameter: Model and Fit Dependent Resolution of Parameter: Variable Systematic Effects: (1) Zero values mean no parameter computed. (2) No angular dependence has been included in the spectrum; the data is taken to be isotropic. (3) Waviness in the profile results from sparseness of sampled energies. Caveats: (1) Data is reported from only MEPS electrons. Caution should be used interpreting data because HEPS electrons are not included. (2) Data gaps are most likely caused by either no sensor included within the loss cone or the spacecraft is charged and MEPS data is not reliable. (3) Result dependent on atmospheric model, 1976 US Standard Atmosphere used. ******************************************************************************* File: 3TP Protons (HEPS) Subtype: HEPS_PROT_ED Description: Energy Deposition by HEPS Protons Only Accumulation Time: 1 UARS minute (65.536 sec) Parameter No. 1: Energy Deposition by Protons Alt. Range: 5 km - 400 km (grid defined by project) Parameter Units: erg/(cm**3-s) Est. Precision of Parameter: 3 Digit Est. Accuracy of Parameter: see Parameter 2 Resolution of Parameter: Variable Systematic Effects: (1) Zero values mean no parameter computed. (2) No angular dependence has been included in the spectrum; the data is taken to be isotropic. (3) Waviness in the profile results from sparseness of sampled energies. (4) Only those HEPS sensors having a corresponding LEP unit are used. Caveats: (1) Data is reported from only HEPS protons. Caution should be used interpreting data above 100 km because MEPS protons are not included. (2) Data gaps are most likely caused by no sensor included within the loss cone. (3) Result dependent on atmospheric model, 1976 US Standard Atmosphere used. (4) High energy data was fitted to a double power law. It may not reflect intense precipitation accurately. Parameter No. 2: Standard Deviation in the Energy Deposition by Protons Alt. Range: 5 km - 400 km (grid defined by project) Parameter Units: erg/(cm**3-s) Est. Precision of Parameter: 3 Digit Est. Accuracy of Parameter: Model and Fit Dependent Resolution of Parameter: Variable Systematic Effects: (1) Zero values mean no parameter computed. (2) No angular dependence has been included in the spectrum; the data is taken to be isotropic. (3) Waviness in the profile results from sparseness of sampled energies. (4) A negative value of standard deviation indicates a region in which the fit to the data exceeds the fit to the sum of the data plus error. (5) Only those HEPS sensors having a corresponding LEP unit are used. Caveats: (1) Data is reported from only HEPS protons. Caution should be used interpreting data above 100 km because MEPS protons are not included. (2) Data gaps are most likely caused by no sensor included within the loss cone. (3) Result dependent on atmospheric model, 1976 US Standard Atmosphere used. (4) High energy data was fitted to a double power law. It may not reflect intense precipitation accurately. ******************************************************************************* File: 3TP Protons (MEPS) Subtype: MEPS_PROT_ED Description: Energy Deposition by MEPS Protons Only Accumulation Time: 2 UARS seconds (2048 msec) Parameter No. 1: Energy Deposition by Protons Alt. Range: 5 km - 400 km (grid defined by project) Parameter Units: erg/(cm**3-s) Est. Precision of Parameter: 3 Digit Est. Accuracy of Parameter: see Parameter 2 Resolution of Parameter: Variable Systematic Effects: (1) Zero values mean no parameter computed. (2) No angular dependence has been included in the spectrum; the data is taken to be isotropic. (3) Waviness in the profile results from sparseness of sampled energies. Caveats: (1) Data is reported from only MEPS electrons. Caution should be used interpreting data because HEPS electrons are not included. (2) Data gaps are most likely caused by either no sensor included within the loss cone or the spacecraft is charged and MEPS data is not reliable. (3) Result dependent on atmospheric model, 1976 US Standard Atmosphere used. Parameter No. 2: Standard Deviation in the Energy Deposition by Protons Alt. Range: 5 km - 400 km (grid defined by project) Parameter Units: erg/(cm**3-s) Est. Precision of Parameter: 3 Digit Est. Accuracy of Parameter: Model and Fit Dependent Resolution of Parameter: Variable Systematic Effects: (1) Zero values mean no parameter computed. (2) No angular dependence has been included in the spectrum; the data is taken to be isotropic. (3) Waviness in the profile results from sparseness of sampled energies. Caveats: (1) Data is reported from only MEPS electrons. Caution should be used interpreting data because HEPS electrons are not included. (2) Data gaps are most likely caused by either no sensor included within the loss cone or the spacecraft is charged and MEPS data is not reliable. (3) Result dependent on atmospheric model, 1976 US Standard Atmosphere used.