The solar wind reflects the composition of the Sun and physical processes in the corona. Analysis produces information on how the solar system was formed and on physical processes in the corona. The analysis can also produce information on the local interstellar medium, galactic evolution, comets in the solar wind, dust in the heliosphere, and matter escaping from planets

Suess, S. T.

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NASA Manhall Space F f i C  C d e r  
COMPOSITION OF THE SOLAR WIND. S. T. Suess, National Space Science & Technology Center, NASA 
Marshall Space Flight Center, Mail Code VP62, Huntsville, Alabama 35812, USA, email: steven.t.suess@nasa.eov. 
Introduction: The solar wind reflects the compo- 
sition of the Sun and physical processes in the corona. 
Analysis produces information on how the solar sys- 
tem was formed and on physical processes in the co- 
rona. The analysis can also produce information on the 
local interstellar medium, galactic evolution, comets in 
the solar wind, dust in the heliosphere, and matter es- 
caping from planets. 
History: The first measurement of solar wind 
composition was done by exposing aluminum foil on 
the surface of the Moon and by studying implanted 
ions in lunar rocks and soils. The asbsence of a signifi- 
cant lunar magnetic field means the solar wind im- 
pinges directly on the lunar surface and on the foils. 
Ions were embedded in the foils and later analyzed by 
acid etching after return to Earth. This revealed the 
particle tracks, and permitted recovering a portion the 
trapped material. Not only elements, but also individ- 
ual isotopes were measured. 
In intervening years, plasma detectors have been 
developed that analyze solar wind charge state and 
composition. The first of these was the Solar Wind 
Ionization and Charge state Spectrometer (SWICS) on 
Ulysses. The Gensis mission is the latest attempt to 
more deeply probe the composition of the solar wind. 
This mission used the Apollo approach in a modern 
context - samples of various types of material (ceram- 
ics, metals, ...) were exposed to the solar wind for 
varying lengths of time up to months (cumulative). A 
small solar wind plasma instrument determined the 
instantaneous type of solar wind (fast, slow, transient). 
Three sets of surfaces were exposed, each only to one 
type of wind. This is because solar wind composition 
depends on the type of solar wind. For rarer elements, 
an electrostatic concentrator was employed to enhance 
the effectiive collecting area. 
Why the Moon?: Deployment on the Moon cir- 
cumvents several limitations imposed on Gensis. The 
stable platform in the solar wind. The second is that 
there is not the physical limitation on collecting area 
inherent on a freely flying spacecraft. The range of 
particle fluxes varies by perhaps up to 10". Genesis 
and the lunar foils were therefore excluded fiom ana- 
lyzing the rarest species. The third advantage is that 
exposure times can be relatively long. Although a new 
lunar experiment would not be as simple as the 'roller 
shade' lunar foils that were deployed in 1969-1974, 
they would be very simple in comparison to any mod- 
ern spacecraft flight experiment. 
Requirements for the Moon: For lunar deploy- 
ment, the simplest set of instruments would be a sta- 
tionary array of materials like flown on Genesis. With 
sufficiently long exposures, this would produce im- 
proved results for minor species. A better experiment 
would have solar arrays and a solar wind monitor with 
deployable collectors that extend for differing solar 
wind regims. An electrostatic concentrator, achieving 
enhancements of more than 20, would probe minor 
species even more deeply. Technically, the instrument 
would be an evolutionary advance over Genesis. 
Anticipated Results: The best way to illustrate 
the types of results that can be anticipated is to list 
some of the results from the lunar foils, lunar soils, 
SOHOICELIAS, and UlyssesISWICS. These are: 
Measurement of the Abundance of Helium-3 in the 
Sun and in the Local Interstellar Cloud with 
ULYSSESISWICS [I]. Isotopic composition of solar 
wind neon [2]. SWICSIUlysses observations: The 
three-dimensional structure of the heliosphere in the 
declining/minimum phase of the solar cycle [3]. An 
Empirical Study of the Electron Temperature and 
Heavy Ion Velocities in the South Polar Coronal Hole 
[4]. Origin of the Solar Wind From Composition Data 
151. Chemical evolution in our galaxy during the last 5 
Gyr [6]. Unusual composition of the solar wind in the 
203 May 1998 CME observed with SWICS on ACE 
[7]. Elemental composition of the inner source pickup 
ions [8]. Implication of the observed anticorrelation 
between solar wind speed and coronal electron tem- 
perature [9]. These papers reflect the broad range of 
subjects mentioned in the Introduction. 
References: [I] Gloeckler G., and Geiss, J. (1998) 
Spa. Sci. Rev., 84(1/2), 275-284. [2] Kallenbach, R., 
and 27 others (1997), J. Geophys. Res.., 102(A12), 
26895-26904. [3] Woch, J., and 7 others (1997), Geo- 
phys. Res. Lett., 24(22), 2885-2888. [4] KO, Y.-K., 
Fisk, L., Geiss, J., Gloeckler, G., & Guhathakurta, M. 
(1997), Sol. Phys., 171(2), 345-361. [5] Geiss, J., Glo- 
eckler, G., von Steiger, R. (1995), Spa. Sci. Rev., 72, 
49. [6] Geiss, J., Gloeckler, G., & Charbonnel, C. 
(2002), Astrophys. J., 578, 862-867. [7] Gloeckler, G., 
and 8 others, Geophys. Res., Lett., 26(2), 157-160. [8] 
Gloeckler, G., Fisk, L. A,, Geiss, J., Schwadron, N. A., 
& Zurbuchen, T. H. (2000), J. Geophys. Res., 105(A4), 
7459-7462.. [9] Gloeckler, G., Zurbuchen, T. H., & 
Geiss, J. (2003), J. Geophys. Res., 108(A4), doi: 
10.102912002lJA0009286. 
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Composition of the Solar Wind

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