PROBABILITY DISTRIBUTION
FUNCTIONS FOR THE
GEOFFECTIVENESS OF SOLAR WIND
INTERPLANETARY MAGNETIC
STRUCTURES
M. Virginia Alves, E. Echer, W. Gonzalez
International Living with a Star – October 2009 – Ubatuba - Brazil
Solar wind interplanetary magnetic structures
Early 1930s – intense magnetic storms - driven by
interplanetary plasma structures
Interplanetary structures can be geoeffective (cause
intense magnetic storms) if they present a continuous,
long-duration, and intense southward magnetic field
3 main interplanetary structures are found in interplanetary
space:
 ICMEs – interplanetary manifestations of CMEs
(including MCs),
 interplanetary shocks, and
 corotating interaction regions (CIR).
Structure Properties - CIR
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proton density rises to unusually high values
near the leading edges of the streams; persist
for ~1 day; density profile - in the inverse ratio to
bulk speed (V) ;
IMF magnitude - proportional to V
constant polarity throughout the stream except
for some fluctuations lasting a few hours;
proton temperature (T) varies in a pattern
similar to V;
it increases with speed and
shows a slight decrease during the magnetic
field descent phase.
Shocks and CIRs
February/March 1999
SI = stream interface (contact between fast and slow SW)
Structure Properties - ICMEs
Common characteristics at 1 AU:
 abnormally low proton temperature
 reduction in the level of the IMF fluctuations
 some degree of organization in the magnetic field
 bounded by distinct magnetic field discontinuities (abrupt changes in
plasma parameters)
Magnetic Clouds (subset of ICMEs)
 large-scale smooth field rotation
 enhanced magnetic field magnitude
 decreased plasma temperature (low  - ratio between thermal and
magnetic pressure)
Complex Ejecta (CE)
 Burlaga et al, 2001 - fast (>600km/s) flows that are neither corotating flows
nor MCs - move past Earth during a day or more - present disordered
magnetic fields; Some CE - consist of material and magnetic fields from
multiple CMEs.
ICMEs and Schocks
Previous Results
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Gosling et al (1991) - Kp 191 MCs, 171 shocks, 1978-1982, 44%
(ICMEs) and 53% (shocks) Kp 5Jurac et al (2002) – Dst 107 shocks, 1995-2000, 21% Dst  -100
nT, 40%  shocks, 10-15% non  shocks
Wu & Lepping, (2002) Dst 34 MCs, 1995-1998, 88% Dst  -50 nT
Zhang et al., (2004) Dst 104 MCs, 1998-2002, 80% Dst  -30 nT,
56% Dst  -50 nT, and 34% Dst  -100 nT
Huttunen et al., (2005) Dst 74 MCs, 1997-2003, ~71% Dst  -50 nT
Yermolaev et al. [2005] review - addressed a comparison of data
analysis methods
Zhang et al., 2007 1996-2000 identified the solar CME sources for
27 major geomagnetic storms (Dst -100 nT), only 1 caused by CIR
Gopalswamy (2008) Solar cycle 23 summarized the properties of
CMEs and high-speed streams and described their geoffectiveness
Events
Observation Period: 1964-2003
MCs: 170
CIRs: 727
Interplanetary Schocks: 830 eventos
Metodology: geoeffectivity is analized in terms of geomagnetic indices Kp
(ap), AE e Dst; peak values were obtained within two days after the
observation of a given interplanetary magnetic structure.
Intense
Moderate
Weak
Quiet
Dst
Dst ≤ -100
-50≤ Dst <-100
-30 ≤ Dst < -50
Dst > -30
Kp
Kp ≥ 7o
ap ≥ 111
5+ ≤ Kp < 7o
56 ≤ ap < 111
4+ ≤ Kp < 5+
32 ≤ ap < 56
Kp < 4+
ap < 32
AE (nT)
AE ≥ 1000
500 ≤ AE < 1000
200 ≤ AE < 500
AE < 200
General Statistical Results
Echer et al. Space Weather, 2006
Influence of MCs on shock geoeffectiveness
Echer et al. Space Weather, 2006
Distribution of the magnetic indices
MC
SHOCK
CIR
25
15
15
10
10
5
5
% events
20
15
10
5
0
-100
0
100
300
400
500
-Dst
10
% events
200
0
-100
0
100
300
400
500
-Dst
10
5
200
500
1000 1500 2000 2500 3000
100
300
400
500
-Dst
0
0
500
AE
1000 1500 2000 2500 3000
0
500
AE
25
200
5
0
0
0
10
5
0
0
-100
1000 1500 2000 2500 3000
AE
15
15
10
10
5
5
% events
20
15
10
5
0
0
0
100
200
ap
300
400
0
0
100
200
ap
300
400
0
100
200
ap
300
400
Results from normality W-test Shapiro-Wilk
(Royston, 1981)
• MC and CIR - Dst and ap are not normally distributed at 0.05
significance level;AE is normally distributed at 0.05 significance
level;
• Shocks, AE is not normally distributed at 0.05; removing the
extreme values, the distribution becomes Gaussian at 0.05 Wtest;
• The parameter A3 is the asymmetry;
it indicates how
different of a normal distribution, in terms of extremes, a
distribution is (A3 = 0 for a normal distribution).
Dst
Shocks
Average -71.9
sd
62.7
min
-472
max
10
Median -55
A3
-2.05
N
830
Dst
MCs
-94.7
54.4
-288
-5
-82
-1.07
170
Dst
CIRs
-43.2
24.2
-131
9
-38
-0.85
747
AE
Shocks
870
396
106
2780
840
0.72
830
AE
MCs
1007
344
104
2155
1014
0.34
170
AE
CIRs
792
280
116
2300
786
0.50
747
ap
Shocks
72.3
67
3
400
48
1.88
830
ap
MCs
92
63
7
300
80
0.87
170
ap
CIRs
48
29
9
236
39
1.50
747
Fitted distribution functions
0,15
0,10
0,05
0,00
-50
0
50 100 150 200 250 300 350 400 450 500
-Dst
0,100
Probability
Gaussian for Dst
and AE
Probability
0,20
Probability
Distribution
Function – fitting
0,075
0,050
0,025
0,000
0
500
1000
1500
Probability
2000
2500
AE
0,15
Exponential for ap
Shocks
MCs
CIRs
0,10
0,05
0,00
0
100
200
300
ap
400
3000
Conclusions
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Transient interplanetary structures are more geoeffective than CIRs
MCs are the most geoeffective structure as measured by the three
geomagnetic indices used here
The geoeffectiveness as measured by the AE index is the largest
one for all the interplanetary structures we used in this paper
The main geoeffectiveness of CIRs is seen in AE activity, while for
shocks and MCs the Dst and Kp geoeffectiveness is much higher
relatively to CIRs
The occurrence of combined structures (Shock + MC) seems to be
more geoeffective for every class of geomagnetic activity than the
occurrence of isolated interplanetary structures
The probability distributions obtained in this work can be used for
space weather forecast by given a probability of an observed
interplanetary solar wind magnetic structure be followed by every
type of magnetic activity.
References
1. ECHER, Ezequiel ; GONZALEZ, Walter D ; ALVES, M. V. Minimum
variance analysis of interplanetary coronal mass ejections around solar
cycle 23 Maximum (1998-2002). Solar Physics, 233 (2), 249-263, 2006
2. ALVES, M. V.; ECHER, Ezequiel ; GONZALEZ, Walter D .
Geoeffectiveness of Corotating interaction regions as measured by Dst
index (A07S05, doi:10.1029/2005JA011379.). J. Geophys. Research, 111
(5), 1-9, 2006
3. ECHER, Ezequiel ; GONZALEZ, Walter D ; ALVES, M. V. On the
geomagnetic effects of solar wind interplanetary magnetic structures
(S06001, doi:10.1029/2005SW000200). Space Weather The International
Journal of Research And Applications, 4, 1-11, 2006
4. ECHER, Ezequiel ; ALVES, M. V. ; GONZALEZ, Walter D . A statistical
study of magnetic cloud parameters and geoeffectiveness. J. of
Atmospheric and Solar-Terrestrial Physics, 67 (10), 839-852, 2005
5. ECHER, Ezequiel ; ALVES, M. V. ; GONZALEZ, Walter D .
Geoeffectiveness of interplanetary shocks during solar minimum (19951996) and solar maximum (2002). Solar Physics, 221, 361-380, 2004
Acknowledgements: ACE SWEPAM and MAG teams - data publicly available; NSSDC at Goddard Space
Flight Center – OMNIweb database; National Geophysical Data Center and to the World Data CenterGeomagnetism – geomagnetic indices. Brazilian Agency CNPq.