Six years of accumulated ISEE-3 and IMP-8 data to study variations in elemental relative abundances among the different populations of energetic ions seen in interplanetary space are surveyed. Evidence suggesting that heavy ion enrichments may be organized by a rigidity scaling factor A/Z over the range H to Fe is presented. Data to support the hypothesis that shock-associated particles are probably accelerated from ambient energetic fluxes are shown

Mcguire, R. E.

Reames, D. V.

Vonrosenvinge, T. T.

English

NASA Technical Reports Server

22S
SH2.1-7
VARIATIONSIN ELEMENTALCOMPOSITIONOF SEVERALMEV/NUCLEONIONS
OBSERVEDIN INTERPLANETARYSPACE
R.E.McGuiret, T.T.von Rosenvinge,and D.V.Reames
NASA/GoddardSpaceFlightCenter,
Greenbelt,MD 20771 USA
ABSTRACT
We havesurveyedsixyears of accumulatedISEE-3and IMP-8
datato studyvariationsin elementalrelativeabundances
amongthe differentpopulationsof energetic(1.5to >10
MeV/nuc)ionsseen in interplanetaryspace. We present
evidencesuggestivethat heavy ion enrichmentsmay be
organized(withsubstantialscatter)by a rigidityscaling
factorA/Z* over the rangeH to Fe. We alsoshow somedata
to supportthe hypothesisthat shock-associatedparticlesare
probablyacceleratedfromambientenergeticfluxes.
1. Introduction.The elementalcompositionof solarenergeticparticle
(SEP)eventshas beenthe subjectof a numberof recentstudies
[1,2,3,4,5,6].This paperis a reportof resultsfroma new, ongoing
studyof low energy(1-10MeV/nucleon)elementalcompositionwith
comblneddata fromthe Goddardparticleexperimentson ISEE-3and IMP-8.
2. AbundanceDistributions.We have
identifiednearly150 separate ISEE-3,,M_e F_RES(19-28MeV/NUC)
events,which occurredbetween1978 ,a ' '
and 1983,with >50 Oxygencountsin _o I
the ISEE-3energyband 1.9 to 2.8
MeV/nucleon.Of theseevents,we
can associateaboutone-halfwith ,_ ,o_
solarflares. The otherperiodsare ._o I
eithershock-associatedor of Fl_
unknownorigin. Figure1 contains ,o
histogramsof the abundanceratios o, ;o
H/O, He/O,C/O, Si/Oand Fe/O _ I
constructedfromeventaveragesof _,o
_o
the flareevents. The arrows _ lh
indicatemedianvaluesin the ",o
distributions.Data for He and
heavierions comes fromthe ISEE-3 o',I °s_o
experiment,data for H and agalnHe
comes from IMP-8. We note thatthe '
He/O,C/O and Si/Odlstributionsare
narrowcomparedto H/O or Fe/Oand o, ,oF_O
that there is a high abundancetall ' _-_ F--I_--r-_
in the Si/O distribution. imjllro
Histogramsconstructedusingour a.o, RE_TIVEABUNDANCE
identifiedshockeventsor from
those increasesthat are of unknown
origintend to followthe same Fig. 1. Abundancesin flareevents.
fAlsoDept. of Physicsand Astr.,U. of MD, CollegePark,MD 20742USA
5 
1-7 
ATIONS N EMENTAL ITION  EVERAL /NUCLEON ONS 
ERVED N NTERPLANETARY PACE 
.E. CGuiret , .T. von ose inge, and .V. eames 
S / ddard ce light e t r, 
ree elt, MD 20771 SA 
TRACT 
e ve rveyed ix rs f ccum lated ISEE-3 nd IM -S 
ta t  tudy iations in lemental lative undances 
ng t  ifferent lations  getic 1.5 to 0 
e / uc) ions en in interplanetary ce. e resent 
evidence suggestive that heavy ion enrichments ay be 
rganized ( ith s stantial s tter) by  rigidity s ling 
actor /Z* r the ange  to . e lso how ome ta 
to support the hypothesis that shock-associated particles are 
robably accelerated from a ient e ergetic fluxes. 
. Introduction. he elemental c sition f s lar e ergetic rticle 
(SEP) ts s en the ject f  er f recent tudies 
[ ,2,3,4,5,6]. is er is  report f r sults from  ew, oing 
study f low rgy (1-10 e / cleon) lemental sition ith 
co blned data from the oddard particle experiments on ISEE-3 and IMP-S. 
 ance i ributions.  ve 
l e tified early 150 se arate 
e e ts, hich cc rred etween 1975 
d S3, ith 0 gen ts ln 
the ISEE-3 energy band 1.9 to 2.S 
e / leon. f these ts,  
n sociate t half i h 
solar flares. The other periods are 
ther -as ociated   
known rigin. igure  tains 
histograms of the abundance ratios 
/O, e/O, /O, ilO and Fe/O 
constructed from event averages of 
e lare s. e rows 
n icate e an ues n he 
tributions. a or  d 
heavier lons comes from the ISEE-3 
experiment, data for Hand agaln He 
s rom S.  e hat he 
e/O, /O and ilO lstributions are 
narrow co pared to /O or Fe/O and 
that there is a high abundance tall 
n he lO tribution. 
istograms constructed using our 
d ified hock ts  rom 
hose ncreases  e  known 
rigin tend to follow the same 
ISEE-3. IMP-a FLARES (1 9 - 2 a MeV/NUC) 
20 H/O 
10 
20 HolD 
10 
~ Or-------~,0~-=~~~~----~ 
~ 
II: 
~ 20 
::Ii 
:::> 
z 
10 
10 
C/o 
01 
50/0 
10 
olD 
ELATIVE ABUNDANCE 
Flg. 1. bundances in flare events. 
t lso ept. of Physics and str., U. of MD, College Park, MD 20742 USA 
https://ntrs.nasa.gov/search.jsp?R=19850026475 2020-03-20T17:01:53+00:00Z
226
SH2.1-7
general range and dlstributlon of iSEE-3,IMP-8
values as the flare events in Figure
1, except that there are fewer Fe- 1.9-2.8MeVINUC
enriched events. 1o ......., ........, ........
3. Abundance Correlations. An _1_
important question in the _
interpretation of heavy-ion i
enrlchments is whether atomic number
(Z) atomic mass (A) or the _-
rlgldity-scaling factor mass divided
by effectlve charge (A/Z*) best
organizes the enrichment factors for IO-I
different elements. Note that A/Z*
for H:He:O:Si:Fe fall in the approx-
imate ratios 1.0:2.0:2.2:2.6:4.0,
uslng the charge state measurements 1o-2 ................. , .......
of [7]. Thus the relative histogram Io-_ i 1o 1o2
wldths in Figure 1 are conslstent O/Si
with A/Z* as the organlzing i_ ........, ........, .......
parameter, ]n that largest
dl fferences in A/Z* gl ve ri se to the I,_'l'IIlilt!
widest distributions.
To further explore this idea, we 10 _.
present a series of scatter plots of ® _i_,_jthe flare data in Figures 2a-2c. --._
Figure 2a shows O/Sl versus Sl/Fe. o -F-LI_+
The trend as seen (larger O/Si imply I
larger Sl/Fe, a positive slope) is -i-___
the trend expected given that heavy I +
ion enrichments increase I
monotonlcally with e.g. increaslng I0-I ........ J ........ , .......A/Z* [1,2,3,4,6]. Note the common • 10 102 103
factor of the Si abundance in the He/O
denomlnator of 0/$I and the io4.. ......., ........,- .......
numerator of SI/Fe. If variations
(from whatever cause) in 0 and Fe
were not correlated with variations t+ ' II Itin Si, we mght still find an _ _ It
apparent correlation in the ratios 't '+_l'_i,_-+.+i+_
because of thls common factor but . -
wlth a negatlve slope. The
amplltude of the random variations "_ I * _i_ 1_
determnes whether such an effect _ _ + .
w111 be seen. Figure 2b shows He/O ++ +
versus O/Fe. Given the narrow +,_
distrlbutlon of He/O in Figure I, It
is not surprqslng that we find, 1o
Fig. 2. Scatter plots of flare
abundance ratios: (a) O/S1 vs 1 , i a,*,l,I , , ,lllJJl i a i,,1
SI/Fe, (b) He/O vs O/Fe, and Io io2 io3
(c) H/He vs He/Fe. H/He
28 
general range and dlstributlon of 
al es as t e flare e e ts i  i re 
1, except that there are fe er e-
lched e t . 
. bu a ce orrelations. n 
important question in the 
lnterpretation of heavy-ion 
lchments s hether ic  
(Z), ato ic ass (A) or the 
rlgldity-scaling factor mass divlded 
by effectlve charge ( /Z*) best 
organizes the enrichment factors for 
iffere t ele e ts. ote t at / * 
for : e: :Si:Fe fall in the approx-
 o  . . .2:2.6:4.0, 
uSlng the charge state easure ents 
of [7]. Thus the relative histogram 
l t s i  i re  are c slste t 
ith /Z* as the organlzing 
para eter, ln that largest 
dlfferences ln A/Z* glve rise to the 
i  i ributions. 
To further explore this idea, we 
present a series of scatter plots of 
 are  n i es . 
Figure 2a shows /Sl versus SliFe. 
The trend as seen (larger /Si imply 
larger SliFe, a positive slope) is 
the trend expected given that heavy 
on ichm s n rease 
onotonlcally ith e.g. increaslng 
/ * [ ,2,3,4,6]. te t e co mon 
factor of the Si abundance in the 
denomlnator of O/Sl and the 
er t r  liF .  iations 
(from hatever cause) in 0 and Fe 
were not correlated with variations 
in Si, we mlght still find an 
apparent correlation in the ratios 
e  hlS om n or  
lth a negatlve slope. T  
amplltude of the random variations 
determlnes hether such an effect 
wlll be seen. Figure 2b shows He/O 
versus O/Fe. Given the narrow 
distrlbutlon of e/  in lgure 1, lt 
1S not surprlslng that e flnd, 
Fig. 2. Scatter plots of flare 
abundance ratios: (a) /Sl vs 
SliFe, (b) He/O vs /Fe, and 
(c) /He vs e/ e. 
10- 1 
0-2 
10- 1 
102 
10 
CD 
LL 
........ 
0 
10- 1 
1 
104 
loa 
Q) 
11. 
Q;1Q2 
:J: 
10 
2.1-  
I -3, S 
1.9-2.S MeV/NUC 
10 
/ i 
It, t 
,,',dt t 
'tH 
t -+ 1>t' 
++f + jf~ 
+*t 
--t  
 2 
alO 
" 
t,' \lttl 
t .: ,~ j t 
+ : +t,lji't 
1- t " t 
fIr t t + 
  t It 
tf 
t 
l~~~~,t~~~~~~~ 
1 10 102 103 
H  
227
SH2.1-7
at best, only a slight posltive
ISEE-3,1M_8 19-2.8 MeV/NUC slope to the correlatlon. Thls plot
is also consistent wlth A/Z*
organization slnce the scallng
t factors for He and 0 are similar.
M/o It is not easily understood in terms
lo_ , of organization by Z or A
* _, ,. * . separately. Random varlatlons would
' ' again give a negatlve slope, if any,
to the plot.
10o( o
A plot of hlgher energy (7.2-12.5
MeV/nucleon) He/O to O/Fe In fact
° oo ._o shows such a negative slope. Thls
I_ o higher energy data lS consistent
o °°
°o o o oO with the published ratios of McGuire
° et al. (1979,1985) but we emphasize
wu that such a negative slope is
_t _o _ ambiguous because of the common
_ , factor In the ratios. That the
. t" " " nature of these plots changes with
I _ N/O energy may be only a consequence ofo _ _o to .° o° _ the increased scatter in the
relative fluxes at the hlgher
NVO energles.
_* . _ "" *_ Figure 2c shows H/He versuso _ _ / He/Fe. Here too there is a
_ M_O suggestion of positive slope
_ _ _ _ _ _ (posslbly larger in magnitude than
_ that of He/O versus O/Fe) but the
o trend is obscured by the overall
scatter in the data. If A/Z*
svo f, organizes the data overall, we would
., f" t '' ,, -" expect H/He to be positively
o_ ft _ correlated with He/Fe or O/Fe. We
note that H and He spectral slopes
t are generally not equal [2,8,9]; the
F_o unequal spectral slopes may be
o_ _ f_ _ _ largely responsible for the
II scatter. Other explanations for a
#_ general colnclde_ce of low H/He
I$• ratlos with hlgher Fe abundances
ool (for Instance, special plasma
condltions required in the source
m _ _ _ _ _ region for an Fe enrichment to take
_ _ _ _ _ _ place [10]) are also clearly
_ _ _ _ _ _ possible.
4. A Source Population for Shock-
Fig. 3. Abundances for 7 palrs of associated Particles. A quite
events (ambient energetic flare different question of concern to us
particles and shock-associated is that of the source population in
particles), shock-associatedenergetic particle
ISEE-3. IMP-8 1 9 - 2.8 eV/NUC 
 
10.000 
• 
1000 
o 
100 0 
• 1 01 T 
01 
01 t t 
01 
001 
en 
.... 
en 
'. 
+. 
00 
 
 
ClO 
+. •• 
alO 
~+ • 
.. 
+. 
t 
en 
.... 
en 
+ 
.. 
+ 
SilO 
.... 
:::> 
.., 
'" ~ 
.... 
00 
wo 
• 
• • 
• 
o 
o 
• 
• 
HalO 
o 
 
• • 
N/O 
D D 00 
•• +. 
glO 
.. .. 
• 
• 
FalO 
.... 
•• 
• 
00 
•• 
.+ 
•• 
.... 
GO 
en 
0.. 
III 
'" ~ 
ig. 3. bundances for 7 pa1rs of 
events (a bient energetic flare 
particles and shock-associated 
particles). 
27 
.1-7 
t st, l   light 1tive 
lope to th  rrelat10n. 1S l t 
s so si tent 1t  / * 
r a 1zation Sl ce the scal1ng 
factors for He and 0 are si ilar. 
It 1S not easily understood 1n terms 
of organization by  or  
separately. Random var1at10ns would 
in ive  t1ve slop , i  , 
to the plot. 
 l t f 1 r rgy ( .2-12.5 
eV/nucleon) e/O t  / e 1n f t 
shows such a negative slope. Th1S 
1 r rgy ta 1  s1ste t 
ith the published ratios of cGuire 
et l. (19 ,1985) t e e phasize 
that such a negative slope is 
ambiguous because of the common 
factor 1n the ratios. That the 
nature of these plots changes ith 
energy may be only a consequence of 
the 1ncreased scatter in the 
r lative fluxes t the 1 r 
energ1es. 
Figure 2c shows H/He versus 
e/ e. ere too there is a 
suggestion of posit1ve slope 
(posslbly larger in magn1tude than 
t t f e/O rsus / e) t th  
trend is obscured by the overall 
er n h  .  /Z* 
organizes the data overall, we ould 
expect H/He to be positively 
correlated with He/Fe or O/Fe. We 
note t at  and He spectral slopes 
are generally not equal [2,8,9]; the 
unequal spectral slopes may be 
largely responsible for the 
scatter. Other explanations for a 
al 01 c1de~ce  low /  
rat10s ith h1gher Fe abundances 
(for 1 stance, s ec1al lasma 
cond1tions requ1red 1n the source 
r gion f r a  e richm t t  t  
place [10]) are also clearly 
possible. 
4.  Source Populat10n for Shock-
associated Particles. A quite 
different question of concern to us 
is that of the source population in 
shock-associated energet1c particle 
228
SH2.1-7
flux increases. In partlcular, if these particles are locally
accelerated, then we might expect the shock partlcles to mirror the
abundances of amblent energetic particle fluxes. In Figure 3, we have
plotted elemental abundances as pairs of events (event-averaged
abundances preceeding the shock particles and abundances in the flux
peak associated with the shock) for a select set of events. In these
events, the ambient peak was separable from the shock peak (at the
energy range of the composltion data, again from 1.8-2.8 MeV/nucleon)
and both averaged fluxes were sufficlent to satlsfy the >50 Oxygen count
limit. Those events with unusual composition (e.g. high C/O ratios)
were expected to be the most useful in testlng the hypothesis.
Unfortunately, few events satisfied the selection criteria and these had
mostly average composition. In general, we do believe the abundance
pairs as plotted are consistent with local acceleration of the shock-
assoclated partlcles from the ambient energetic populations. The plot
does not however provide strong positlve evidence for the idea. We note
that varlatlon in H/O between the amblent and shock particles might be
expected because the energy spectra are steepened generally at shocks
and because the ambient H and He spectra do not have the same slope.
Fe/O is complicated by the klnd of temporal variations that occur in
many events [6,11,12], speciflcallywhere Fe/O is higher at the event
onset than near the shock arrlval tlme.
5. Acknowledgments.Thlswork was supportedin part underNASAGrantNGR
21-002-316.
References.
I. McGuire, R.E. et al., 1979, Proc. 16th ICRC, 5, 61.
2. McGulre, R.E. et al., 1985, submitted to Ap. J..
3. Cook, W.R. et al., 1980, Ap. J. (Lett.), 238, L97.
4. Cook, W.R. et al., 1984, Ap. J._ 2_, 827.
5. Mason, G.M. et al., 1980, Ap. J., 239, 1070.
6. Reames, D.V. and T.T. von Rosenvinge, 1981, Proc. 17th ICRC, 3, 162.
7. Luhn, A. et al., 1984, Adv. Space Res., (Graz, CoSPAR PF0_eedings).
8. McGuire, R.E. et al., 1981,. Proc. 17-thICRC, 3, 65.
9. McGuire, R.E. et al., 1984, Adv. Space Res., 4, 117.
10. Flsk, L.A., 1978, Ap. J., 224, 10_8.
11. O'Gallagher, J.J. et al., 1976, Ap, J. (Lett.), 209, L97.
12. Scholer, M. et ai.,1978, J. Geophys. Res., 83, 3349.
228 
SH2.1-7 
flux lncreases. In partlcular, lf these particles are locally 
acc lerated, then we might expect the shock partlcles to mirror the 
abundances of amblent energetic particle fluxes. In Figure 3, we have 
plotted elemental abundances as pairs of events (event-averaged 
abundances pr ceeding the shock particles and abundances in the flux 
peak associ ated with the shock) for a s l ect set of vents. In th se 
vents, the ambient peak wa  sep rable from the shock peak (at the 
nergy range of the composltion d ta, gain from 1.8-2.8 MeV/nucleon) 
and both averaged fluxes were sufficlent to satlsfy the )50 Oxygen count 
limit. Thos  vents with n sual composition (e.g. high C/O ratios) 
were expected to be the most useful in testlng the hypothesis. 
Unfortunately, few events satisfied the selection criteri  and these had 
mostly average composition. In general, we do believe the abundance 
pairs as plotted are consistent with local acc leration of the shock-
assoclated partlcles from the ambient nergetic opulations. The plot 
does not how ver provide strong positlv  evidence for the idea. We note 
that varlatlon ln H/O between the amblent and shock particles might be 
expected because th  nergy spectr  are steepened g nerally at shocks 
and because the ambient H and He spectra do not have the same slope. 
Fe/O 1S complicated by the k1nd of temporal variations that occur 1n 
many events [6,ll,12J, speciflcally where Fe/O is higher at the event 
onset than near the shock arrlval tlme. 
5. Acknowledgments. ThlS work was supported in part under NASA Grant NGR 
21-002-316. 
References. 
1. McGu1re, R.E. et al., 1979, Proc. 16th ICRC, 5, 61-
2. McGulre, R.E. et al., 1985, submitted to Ap. J •• 
3. Cook, W.R. et al., 1980, Ap. J. (Lett.~, 238, L97. 
4. Cook, W.R. et al., 1984, Ap. J., 279, 27. 
5. Mason, G.M. et al., 1980, Ap. J., 239, 1 70. 
6. Reames, D.V. and .T. von Rosenvinge, 1981, Proc. 17th ICRC, 3, 162. 
7. Luhn, A. et al., 1984, Adv. Space Res., (Graz, CaSPAR Proceedings). 
8. McGuire, R.E. et al., 1981,. Proc. 17th ICRC, 3, 65. 
9. McGuire, R.E. et al., 1984, Adv. Space Res., 4, 117. 
10. F1Sk, L.A., 1978, Ap. J., 224, 1048. 
11. O'Gallagher, .J. et al., 1976, Ap. J. (Lett.), 209, L97. 
12. Scholer, M. et al.,1978, J. Geophys. Res., 83, 3349. 


Variations in elemental composition of several MEV/nucleon ions observed in interplanetary space

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