SWEPAM/SWICS Level 3 Merged Solar Wind Proton Data Documentation
This data set consists of 12-minute averaged solar wind proton data from The Solar Wind Electron, Proton, and Alpha Monitor (SWEPAM), and Solar Wind Ion Composition Spectrometer (SWICS). Gaps in the SWEPAM density, bulk speed, and temperature data are filled in using data from SWICS, if available.
SWEPAM and SWICS both measure solar wind proton plasma parameters. In particular, proton speed, density, and temperature can be calculated from the distributions measured by both instruments. For reasons related to accommodating the Ulysses flight spare on ACE at 1 AU, SWEPAM has reduced sensitivity at the lowest energies, and at times underestimates the proton density, especially for very slow wind. Thus, proton density is sometimes culled from low-speed (< ~350 km/s) intervals in the SWEPAM Level 2 data, and proton temperature may also be culled. More rarely, the solar wind velocity may also be culled, especially during periods of both high solar energetic particle background and high wind speeds.
The SWICS instrument is usually producing valid solar wind proton distributions when there are gaps in the SWEPAM Level 2 data. Solar wind proton studies are not part of the primary science goals for SWICS, and the proton speed, density, and temperature data are not included in the standard SWICS Level 2 data products. However, the data are valuable, and are of high enough quality to fill in gaps in the SWEPAM coverage.
The highest time-resolution data that SWICS can provide is 12 minutes, and so the cadence of this data set is 12 minutes.
Note, this is a Level 3 data product: These data have not been validated to the same extent as our ACE Level 2 data products, such as the Level 2 SWEPAM proton moments. They may therefore be of lesser quality than the Level 2 data which are verified in great detail.
- Release notes for SWEPAM/SWICS merged proton data.
- The SWEPAM Home Page at Los Alamos National Labs.
- The SWICS Home Page at U. Michigan.
- SWEPAM Level 2 data.
- SWICS Level 2 data.
SWEPAM/SWICS Proton Data Description
All data records for all ACE instruments contain timing information in the same format. The format of the timing information is described here.
Solar Wind Proton Data
The 12-minute averaged data are organized into yearly data files.
A data value of -9999.9 indicates bad or missing data.
Each 12-minute data record consists of the following data items:
- Proton Density (np in cm -3)
- Radial Component of the Proton Temperature (TP,rr in o Kelvin)
- Ratio of Alpha Density to proton Density (nHe/nP)
- Proton Speed (VP in km/s)
- Proton Velocity Vector in GSE coordinates (in km/s)
- Proton Velocity Vector in RTN coordinates (in km/s)
- Proton Velocity Vector in GSM coordinates (in km/s)
- pos_gse_x,y,z - The x,y,z-components of the spacecraft position, in GSE, in km.
- pos_gsm_x,y,z - The x,y,z-components of the spacecraft position, in GSM, in km.
Also provided are three info/Quality flags, as follows:
- N_swe64 - Number of SWEPAM 64-second records used in the 12-minute average that contained good proton_density data.
- SWICS_flag - This is a bit-field, indicating which SWICS data
items have been used to fill in missing SWEPAM
data, if any. The flag bits have the following
Bit Description 0 SWICS Density used 1 SWICS Temperature used 2 SWICS speed used
- Qual_flag - Quality flag carried over from original SWICS
data, if any SWICS data was used to fill the
SWEPAM data. The flag is a bit-field, and the bits have the
Bit Description 0 Low statistics 1 Very low statistics 2 Non-thermal distribution (2nd moment / fit Vthermal comparison exceeds limits) 3 Missing peak (the peak could not be identified)
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Last Updated: 22 Feb, 2010