L3 Data Products
L3s are the next higher level of data products available to the scientific community. L3s consist of irreversible transformed data and irreversible combinations of data from multiple instruments. Refer to the TRACERS Rules of Use while working with these data products
ACE
The ACE L3 data are pitch angle distributions of electrons that are derived from a combination of ACE L2 and MAG L1B data. The L3 data consist of counts, differential energy fluxes, and uncertainties as a function of pitch angle, calibrated energy, and time.
To compute the pitch angle, electron velocity vectors from ACE and magnetic field measurements from MAG are utilized. Since ACE and MAG operate at different cadences, each component of the MAG vector is linearly interpolated and evaluated at the measurement times recorded by ACE, reconciling the discrepancy in the instruments’ cadences and resulting in pitch angle distributions with the intrinsic sampling rate of ACE. The pitch angle is determined using velocity vectors for each of ACE’s 21 anodes dotted with the linearly interpolated magnetic field vector from MAG in the TRACERS Spacecraft Coordinate System (TSCS).
These pitch angles and their corresponding counts and background counts are then binned into 49 energy steps and 18 pitch angle bins with 10 degress resolution from 0 to 180 degrees. Differential energy fluxes are computed by subtracting the background counts from the counts and dividing by the integration time and geometric factor of a given anode where the counts were measured. A weighted average is utilized in this calculation to account for the fact that multiple anodes contribute counts to a given pitch angle bin. Uncertainties in the differential energy fluxes are also reported as a function of energy step and pitch angle. Poissonian statistics are utilized to propagate the error associated with each differential energy flux measurement in a given energy step and pitch angle bin.
Similar to ACE L2 data, the background correction can result in negative differential energy fluxes in the ACE L3 data and creates extremely large reported uncertainties.