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

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

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:

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):

Also provided are three info/Quality flags, as follows:

Note: The SWEPAM Alpha/proton ratio and the SWEPAM vector velocity are included in this data set, but gaps in these data are not filled with SWICS data. SWICS only provides the scalar proton speed, not the vector velocity. SWICS alpha-particle data are not currently available at 12-minute resolution.

Our Email Address: asc@srl.caltech.edu

Last Updated: 22 Feb, 2010

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