New and Updated Ion Composition Data Products from SWICS
The SWICS data products that are now available from the ACEScience Center,
with new data products shown in bold.
The Solar Wind Ion Composition Spectrometer (SWICS), as part of the ACE and
Ulysses payloads, has revolutionized our understanding of the composition of
the solar wind. After a brief commissioning period in 1997, ACE/SWICS has
become the longest-operating composition instrument in flight, providing
unprecedented elemental composition, ionic composition, and dynamic properties
of 77 species in the solar wind.
To get the most value out of this investigation, the SWICS team has undertaken
an improved analysis of all SWICS data, providing the most accurate and most
complete data set available to the community. The new SWICS data are provided
in two categories:
- From 4 February 1998 to 23 August 2011, "SWICS 1.1", indicates a newer
and improved data set than was formerly available. A thorough recalibration
has been performed, which involved creating an instrument forward model and
ion identification scheme more advanced and precise than that used formerly,
allowing for a reanalysis of SWICS data from the beginning of the mission to
the present, and the recovery of more ions and data products than were
available previously. Most importantly, this novel analysis properly accounts
for low flux elements and uses the correct statistical inversion methodology,
as described by Shearer et al., ApJ, 789, 2014.
- On 23 August 2011, a radiation- and age-induced hardware anomaly altered the
operational state of SWICS, causing an increased level of background to appear
in the heavy-ion time-of-flight measurement and creating an instrument that
best measures composition in an Energy/charge-Energy mode. To understand
and characterize this background, SWICS data delivery was suspended while
various alternate instrument settings were tested and a new model for data
recovery was developed. The ensuing new operating mode of SWICS is now called
"SWICS 2.0", indicating that it operates as a new and different
instrument, delivering a different set of data products than were available
previously. SWICS 2.0 data are now available from 1 June 2012 to present day,
and SWICS continues to make heavy ion measurements that are not available from
any other solar wind composition instrument in flight today.
In addition, the SWICS proton measurements, which are captured in a separate
instrument channel and were unaffected by the hardware anomaly, are now
delivered at 12-minute resolution for the entire duration of the SWICS
The figure shows the SWICS data products that are now available from the ACE
Science Center, with new data products shown in bold. In addition to these, a
merged SWEPAM-SWICS solar wind proton data time series is continuing to be
delivered as a Level 3 data product. Both the new and the recalibrated SWICS
data, along with release notes explaining the analysis and recalibration, and
the statistical guidelines for data usage, can be found at
This item was contributed by
Jason A. Gilbert, Paul Shearer, and Thomas H. Zurbuchen of the University of Michigan.
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Last modified 29 May 2015.