SWICS User Notes - Ulysses
SWICS - User Notes
SWICS Contact:
Dr. R. v. Steiger
International Space Science Institute
Hallerstrasse 6
CH-3012 Bern
Switzerland
Phone: (41) 31-631 4890
Telefax: (41) 31-631 4897
E-mail: vsteiger@issi.unibe.ch
Ulysses/SWICS Heavy Ion Composition Data: User's Recipe
Thomas Zurbuchen and Rudolf von Steiger
Updated 5-Aug-2011
General Composition:
Composition observations are the most powerful technique for identifying the
character of solar wind plasma streams. Plasma composition is determined close
to the Sun, by plasma processes occurring in the upper chromosphere near the
transition region (elemental composition), and by the temperature history of the
plasma between the transition region and 3 solar radii (charge state
composition). These plasma processes near the source differ markedly between the
fast and the slow solar wind, and even larger differences, for example in the
temperature histories, are observed in the case of coronal mass ejections
(CMEs), The compositional data are particularly useful when we try to understand
specific time periods with interacting solar wind streams such as CIRs and CMEs.
Magnetic rotations, indicative of a magnetic cloud embedded inside a CME,
generally occupy only a portion of the CME. The compositional data can be used
to determine the full extent of the CME, and indeed is the only plasma parameter
that can do so.
Elemental composition signatures:
Elemental composition varies according to the solar wind source. Elemental
fractionation strongly depends on the First Ionization Potential (FIP) of the
element. The smaller the FIP, the easier it is to ionize particles that can end
up in the solar wind. Element ratios in the solar wind show a characteristic
fractionation pattern when compared to solar abundance ratios: Elements with an
FIP smaller than 10 eV are enriched in the solar wind by a factor that is
indicative of the solar wind type, on average ~3 in the slow wind and ~1.5 in
fast streams (von Steiger et al. 1997; 2000). The ratio Fe/O compares an element
of very small FIP with a high-FIP element and thus is indicative of the strength
of the FIP fractionation.
Charge state composition signatures:
Charge state composition results, such as from O, C, and Fe, contain a coronal
"finger-print" of the solar wind source region and the expansion properties
close to the Sun (see, e.g. BŸrgi and Geiss, 1986). During their expansion
process from the coronal source, the ionic charge state adapts to the
environment until the recombination and ionization time-scale of a certain ionic
charge state becomes large compared to the expansion time-scale. At this point,
Rf, the respective charge state freezes in. For a given speed, temperature and
density profile each ionic charge state has its own specific freeze- in point
which may vary quite considerably from one ion species to another. It turns out
that O7+/O6+, as well as C6+/C5+ freeze in rather close to the solar wind source
region, and therefore show the most variability. The charge states of Fe freeze
in further out, at up to 3.5 solar radii. It has been pointed out (see, e.g.,
Geiss et al., 1995; Von Steiger et al., 1997; 2000) that the charge state
composition clearly distinguishes coronal hole associated solar wind from
streamer-associated slow solar wind. Furthermore, clear variations within
low-speed solar wind also separate different sources of low-speed solar wind
(Zurbuchen et al., 2000). Finally, very high charge states, e.g. of Fe, are
often indicative of CMEs.
Description of archive parameters:
a) Heavy ion main charge states (yearly files uswimatbYY.dat): Listed are
density (relative to O6+) , speed, and kinetic temperature of the main charge
state of heavy elements. They can be used to track the kinetic properties
(differential speeds, mass- proportional temperatures) of these ions and their
evolution with heliocentric distance, heliographic latitude, etc. They must not
be used, however, to derive freeze-in temperatures or abundance ratios of
elements (although the ratio C6+/O6+ is an excellent proxy for the C and O
freezing-in temperature).
b) Selected charge states and abundance ratios (yearly files uswichstYY.dat): -
Alpha particle speed: Repeated from previous archive for comparison. - C6+/C5+
and O7+/O6+ ratios: These two ratios are essentially redundant, with the former
being ~10 times higher than the latter on average. At high values the O ratio is
more reliable (because C5+ is getting rare) whereas at low values the C ratio is
preferable (because O7+ gets rare). Low ratios are indicative of fast streams. -
Fe/O abundance ratio: This is a proxy for the strength of the FIP fractionation
if divided by the solar Fe/O ratio of ~0.05. - Average charge state of Fe:
Weighted average of all charge states from Fe6+ to Fe16+, normally between 9 and
12 both in slow and in fast wind. High values are a good CME indicator. - Number
of instrument cycles that were accumulated to obtain the 3-hour average value.
Each instrument cycle takes 13 minutes, so values of 12-14 are normal, whereas
low values should be considered as a warning.
Statistical accuracy of results:
The data have been calculated using automatic routines as described in von
Steiger et al. (2000). The accuracy of these data mostly depends on the counting
statistics. Generally, the typical count rate is directly proportional to the
solar wind mass flux. The statistical accuracy of these composition measurements
is estimated to be 10- 25%.
References:
BŸrgi, A., and J. Geiss, Sol. Phys., 103, 347, 1986.
Geiss, J., et al., Science, 268, 1033, 1995.
Schwadron, N. A., L. A. Fisk, and T. H. Zurbuchen, Astrophys. J. , 521, 859, 1999.
Von Steiger, R., J. Geiss, and G. Gloeckler, in Cosmic winds and the heliosphere, 581,
Arizona Press, 1997.
Von Steiger et al., J. Geophys. Res., 105, 27,217, 2000.
Zurbuchen, T. H., et al., J. Geophys. Res., 105, 18,327, 2000.
________________________________________________________________________________
SWICS FILE FORMAT (REFERENCE: A&A,92,2 page 279, table 5)
UDS REPRESENTATIVE: R. VON STEIGER (VSTEIGER@ISSIBERN.CH)
Product 1: Heavy Ions Main Charge States (yearly files uswimatbYY.dat)
RECORD FORMAT:
C FREE FORMAT
READ(1,*)IYEAR,IDOY,IHOUR,IMIN,ISEC,
. DENS_ALPHA,VEL_ALPHA,TEMP_ALPHA,
. DENS_C6,VEL_C6,TEMP_C6,
. DENS_O6,VEL_O6,TEMP_O6,
. DENS_NE8,VEL_NE8,TEMP_NE8,
. DENS_MG10,VEL_MG10,TEMP_MG10,
. DENS_SI9,VEL_SI9,TEMP_SI9,
. DENS_S10,VEL_S10,TEMP_S10,
. DENS_FE11,VEL_FE11,TEMP_FE11
C FIXED FORMAT
READ(1,100)IYEAR,IDOY,IHOUR,IMIN,ISEC,
. DENS_ALPHA,VEL_ALPHA,TEMP_ALPHA,
. DENS_C6,VEL_C6,TEMP_C6,
. DENS_O6,VEL_O6,TEMP_O6,
. DENS_NE8,VEL_NE8,TEMP_NE8,
. DENS_MG10,VEL_MG10,TEMP_MG10,
. DENS_SI9,VEL_SI9,TEMP_SI9,
. DENS_S10,VEL_S10,TEMP_S10,
. DENS_FE11,VEL_FE11,TEMP_FE11
100 FORMAT(X,I4,X,I3,X,I2,2(X,2I2),8(E10.3,X,F6.1,E10.3))
PARAMETER LIST:
IYEAR: year
IDOY: day of year
IHOUR: hour
IMIN: minute
ISEC: second
DENS_ALPHA: alpha to oxygen 6+ density ratio
VEL_ALPHA: alpha velocity
TEMP_ALPHA: alpha temperature
DENS_C6: carbon 6+ to oxygen 6+ density ratio
VEL_C6: carbon 6+ velocity
TEMP_C6: carbon 6+ temperature
DENS_O6: oxygen 6+ density in cm^-3
VEL_O6: oxygen 6+ velocity
TEMP_O6: oxygen 6+ temperature
DENS_NE8: neon 8+ to oxygen 6+ density ratio
VEL_NE8: neon 8+ velocity
TEMP_NE8: neon 8+ temperature
DENS_MG10: magnesium 10+ to oxygen 6+ density ratio
VEL_MG10: magnesium 10+ velocity
TEMP_MG10: magnesium 10+ temperature
DENS_SI9: silicon 9+ to oxygen 6+ density ratio
VEL_SI9: silicon 9+ velocity
TEMP_SI9: silicon 9+ temperature
DENS_S10: sulphur 10+ to oxygen 6+ density ratio
VEL_S10: sulphur 10+ velocity
TEMP_S10: sulphur 10+ temperature
DENS_FE11: iron 11+ to oxygen 6+ density ratio
VEL_FE11: iron 11+ velocity
TEMP_FE11: iron 11+ temperature
DENSITY UNITS: ratio to oxygen 6+ density (no units)
VELOCITY UNITS: km/s
TEMPERATURE UNITS: K
TIME RESOLUTION: 3.0 hours; times indicate the beginning of the interval
NOTES: All parameters values are positive definite; zeroes indicate
missing values
Product 2: Selected Charge State and Abundance Ratios (yearly files uswichstYY.dat)
RECORD FORMAT:
C FREE FORMAT
READ(1,*)IYEAR,IDOY,IHOUR,IMIN,ISEC,
. VEL_ALPHA,
. RAT_C6_C5,
. RAT_O7_O6,
. RAT_FE_O,
. CHARGE_FE,
. N_CYC
C FIXED FORMAT
READ(1,100)IYEAR,IDOY,IHOUR,IMIN,ISEC,
. VEL_ALPHA,
. RAT_C6_C5,
. RAT_O7_O6,
. RAT_FE_O,
. CHARGE_FE,
. N_CYC
100 FORMAT(X,I4,X,I3,3(X,2I2),X,F6.1,3(X,F6.3),X,F4.1,X,I3)
PARAMETER LIST:
IYEAR: year
IDOY: day of year
IHOUR: hour
IMIN: minute
ISEC: second
VEL_ALPHA: alpha velocity
RAT_C6_C5: ratio of carbon 6+ to 5+
RAT_O7_O6: ratio of oxygen 7+ to 6+
RAT_FE_O: abundance ratio of iron to oxygen
CHARGE_FE: average charge state of iron
N_CYC: number of instrument cycles in average
VELOCITY UNITS: km/s
CHARGE UNITS: e = 1.6022E-19 C
TIME RESOLUTION: 3.0 hours; times indicate the beginning of the interval
NOTES: All parameters values are positive definite; zeroes indicate
missing values