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. Even so, the proton data are now being released by the SWICS team as a verified Level 2 data product, and the data 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 other ACE Level 2 data products
- Release Notes
- SWEPAM Level 2 data
- SWICS Level 2 Proton data
- SWICS Level 2 composition data prior to August 23 2011
- SWICS Level 2 composition data after August 23 2011
SWEPAM/SWICS Proton Data Description
Time Data
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)
In addition, the ACE spacecraft position at the beginning of each 12-minute period is provided, in the GSE coordinate system and in the GSM coordinate system):
- 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
meanings:
Examples: if the flag has a value of 0, no SWICS data are used. If the flag has a value of 7, all three SWICS items are used.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
following meanings:
This flag is zero if no SWICS data was usedBit 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)
Our Email Address: asc@srl.caltech.edu
Last Updated: 22 Feb, 2010