1

NORTH–SOUTH ASYMMETRY OF DIFFERENT SOLAR ACTIVITY

FEATURES DURING SOLAR CYCLE 23

Neeraj Singh Bankoti1*, Navin Chandra Joshi

1, Seema Pande

2, Bimal Pande

1, Kavita

Pandey1

1Department of Physics, D. S. B. Campus, Kumaun University, Nainital, Uttarakhand,

India

2Depertment of Physics, M.B.P.G. College, Haldwani, Kumaun University, Nainital,

Uttarakhand, India

*E-mail address.nsbankoti@gmail.com

Abstract

A study on North-South (N-S) asymmetry of different solar activity features (DSAF)

such as solar proton events, solar active prominences, H flare index, soft X-ray flares,

monthly mean sunspot area and monthly mean sunspot number were carried out from

1996-2008. It is found in our result that solar cycle 23 is magnetically weak compared to

solar cycle 22. Study shows the Southern dominance of DSAF during the time period of

study. During the rising phase of the cycle the numbers of DSAF approximately equal on

the North and South Hemisphere. However, these activities tend to shift from Northern

Hemisphere to Southern Hemisphere in between year 1998-1999. The statistical

significance of the asymmetry time series using a 2 - test of goodness of fit indicates

that in most of the cases the asymmetry is highly significant, i.e., the asymmetry is a real

feature in the N-S distribution of DSAF.

Key words: Sun: asymmetry - Sun: activity - Sun: sunspot number - Sun: Soft X-ray

flare - Sun: prominences - Sun: solar proton events

1. Introduction

The occurrence of various solar activity features shows non-uniformity over the solar

disk. It has also been noticed that more activity features occur in one part of the solar

Hemisphere than the other at one time. When these features are examined with respect to

equator of the Sun, they are referred to as the North-South (N-S) asymmetry. The N-S

2

asymmetry of several solar activity features viz relative sunspot numbers (SN), sunspot

groups, sunspot areas (SA), flares, Hα flare indices (Q), solar active prominences (SAP),

coronal mass ejections (CME), radio bursts, solar gamma ray bursts, coronal holes,

faculae, green corona, corona’s ionization temperatures and magnetic fluxes have been

investigated by various authors (Maunder, 1904; Howard, 1974; Roy, 1977; Vizoso and

Ballester, 1987; Bai, 1990; Oliver and Ballester, 1994; Joshi, 1995; Ataç and Özgüç,

1996; Verma, 2000; Temmer et al., 2001, 2002; Joshi and Joshi, 2004; Joshi and Pant,

2005; Atac and Özgüç, 2006; Gao, Li and Zhong, 2007; Chang, 2008; Li et al., 2009;

Joshi et al., 2009).

Bell (1962) has found long term N-S asymmetry in the SA data for SC 8-18.

Carbonell et al. (1993) presented a thorough study of the N-S asymmetry of daily SA,

since these are good indicators of magnetic activity and found the N-S asymmetry is

statistically highly significant using 2 - test of goodness of fit. A detailed study has been

carried out by Verma (2000) to decipher N-S asymmetry of SAP during 1957-1998. The

existence of the real N-S asymmetry of SXR flare index (which is strengthened during

solar minimum) during solar cycle 21, 22 and 23 has been analyzed (Joshi and Joshi,

2004). Joshi et al. (2005) also investigated the N-S asymmetry of H flare events during

the solar cycle 23. Zaatri et al. (2006) studied the N-S asymmetry of meridional and zonal

components of horizontal, solar subsurface flows during the years 2001–2004, which

cover the declining phase of solar cycle 23. More recently, asymmetry of solar activity in

cycle 23 has been studied by Li et al. (2009) using sunspot groups and SA from May

1996 to February 2007 and find the solar activity dominance in the Southern Hemisphere

for cycle 23. Joshi et al. (2009) studied the asymmetry of SAP and groups of different

limb and disk features of SAP for solar cycle 23 and presented a comparison among the

solar cycles 21, 22 and 23.

In the past, the N-S asymmetries of several solar activity features on the entire solar

disk and atmosphere have been studied by various researchers (Waldmeier, 1971; Verma,

1987; 1992; 1993; Ballester et al., 2005). Waldmeier (1971) studied asymmetry of most

outstanding feature of solar activity in the decade 1959 -1969 on the two Hemispheres

and found that on the Northern Hemisphere spots, faculae and prominences were more

numerous and the white light corona was brighter than on the Southern Hemisphere. He

also found that the green coronal line was brighter on the Northern Hemisphere, but the

3

intensity of the red line was asymmetric in the opposite sense. Further, a comprehensive

study was carried out by Verma (1987) on N-S asymmetry for major flares (solar cycles

19 and 20), type II radio bursts (solar cycles 19, 20 and 21), white light flares (solar

cycles 19, 20 and 21), gamma ray bursts, hard X-ray bursts and CME (SC 21) and the

results were compared with the found asymmetry in favor of the Northern Hemisphere

during solar cycle 19 and 20 in favor of the Southern Hemisphere during solar cycle 21.

Verma (1992) also predicted that the N-S asymmetry in solar cycles 22, 23 and 24 may

be Southern dominated which will shift to Northern Hemisphere in solar cycle 25. Verma

(1993) studied various solar phenomena occurring in both Northern and Southern

Hemisphere of the Sun for solar cycles 8-22, calculated the N-S asymmetry indices for

several solar phenomena and plotted them against the number of solar cycles. Similarly,

Ballester et al. (2005) have studied N-S asymmetry using different phenomena of solar

activity. Summaries of the studies of Hemispherical asymmetries of solar activity have

been included in the work of Vizoso and Ballester, 1990; Li et al., 1998 and Li et al.,

2002.

The aim of our work is to make a detailed study of N-S asymmetry of DSAF (SN,

SA, SXR, Hα flare index, SAP, SPE) from 1996 to 2008 (solar cycle 23). Section 2

shows the observational data and statistical analysis. Section 3 represents a brief

description of N-S asymmetry of DSAF during the considered time period. Section 4

contains discussions and results.

2. Observational Data and Statistical Analysis:

The different solar activity features analyzed in our study have been downloaded

form following various web sites:

The monthly North and South SNs (1996-2008), from

ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SUNSPOT_NUMBERS/RNRS with

682 data points.

The monthly North and South number of SAPs (1996-2008), obtained from

ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SOLAR_FILAMENTS with 8539 data

points. After excluding the events which lie on equator, a total number of 8426 events

have been selected to study latitude and longitude distribution.

4

The monthly North and South SXR flares (1996-2008), detected by the GOES

satellites, which can be downloaded from

ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SOLAR_FLARE/XRAY_FLARES with

23335 data points. Out of this 12127 flare events for which heliographic coordinates

are given, are selected.

The monthly number of North and South flare index (1996-2007) compiled in

the Kandilli Observatory, from

ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SOLAR_FLARES/INDEX.

The monthly North and South SA (1996-2008) compiled by D.Hathaway, from

http://solarscience.msfc.nasa.gov/greenwch.shtml.

The North and South monthly number of solar proton events (SPE) (1996-2008),

from http://www.swpc.noaa.gov/ftpdir/indices/SPE.txt with 72 data points.

We compare the amplitudes of solar cycle 22 and 23 by using DSAF. In all activity

indices the amplitudes of solar cycle 23 are distinctively weaker than the solar cycle 22,

as can be seen from Fig. 1 and Table 1. First column of Table 1 represents the DSAF for

cycle 22 and 23. 2nd

, 3rd

, 4th

and 5th

columns represent the average values of the DSAF as

well as their standard deviations within brackets during the solar maximum and minimum

phases of the solar cycles 22 and 23. The last two columns illustrate the variability of

DSAF during rising phase and decay phase between the above two successive cycles.

The N-S asymmetry of solar activity phenomena has been calculated using the

formula:

SN

SNANS

(1)

Here, NSA is the N-S asymmetry index, N is the number of solar activity phenomena in

Northern Hemisphere and S is the number of solar activity phenomena in Southern

Hemisphere. Thus, if NSA > 0, the activity in the Northern Hemisphere dominates and if

NSA < 0, the reverse is true. To verify the reliability of the observed N-S asymmetry

values, a 2 - test is applied with Equation (2) given below.

NS

NSNS

A

A

SN

SN

2

)(

)(2 (2)

5

If ,NSNS AA NSNSNS AAA 2 and ,2 NSNS AA the probability that N-S

asymmetry exceeds the dispersion value is %84p , %5.99%84 p and %5.99p

respectively. Here the first, second and third limits imply statistically insignificant,

significant and highly significant values respectively (Joshi and Joshi, 2004; Joshi et al.,

2009).

3. N-S Asymmetry of Sunspot Numbers, Sunspot Area, SXR Flares, Hα Flare

Index, Solar Active Prominences and Solar Proton Events

To investigate the behavior in variation of DSAF in the North and South

Hemispheres, activities were counted for each Hemisphere separately and are shown in

Table 2 & Figure 2. In Table 2, first and second column represent DSAF and total

number of events reported from different ground and space based observatories and

satellites respectively. Column 3rd

represents events for which the heliographic

coordinates are given and column 4th

and 5th

represent the total number of events in

Northern and Southern Hemisphere respectively during the considered time span. All

parameters shown in Fig 2 show nearly the same monthly variation in the North-South

Hemisphere except SAP. Further, SAP shows an abnormal behavior as it is active from

1996-1998. On the other hand, for the same period, other activities are almost dormant.

For more clear results smoothened monthly means of the DSAF indices in the Northern

and Southern Hemispheres are shown in Fig. 3 (left panel). In the temporal variation of

SA, SXR flares, SAP and SPE the strength of the activity of two Hemispheres is

different. The strength dominates in Northern Hemisphere for flare index and SAP

whereas it dominates in Southern Hemisphere for SA, SXR and SPE. Additional plot of

the smoothed asymmetry for the monthly mean is given for each solar active feature in

Fig.3 (right panel). It is clear that the dominance of activity at the beginning of the cycle

started to alternate between the two Hemispheres during the rising phase (0 – 48 months).

However during the maximum phase the N-S asymmetry dropped nearly to zero and

remained very low (48 – 96 months) and after 96 months of the considered time it is in

favor of Southern Hemisphere.

All these results are confirmed by Fig. 4 in which we have shown the cumulative

counts of the monthly DSAF for the Northern (black line) and Southern Hemispheres

(red line) respectively. The vertical spacing between the two lines is a measure of the

6

Northern/Southern excess of DSAF at that time which shows Southern dominance of SN,

SA, SXR, Q and SAP excluding SPE. In order to characterize the N-S asymmetry of

DSAF, the asymmetry values of the monthly DSAF numbers in the Northern and

Southern hemispheres were calculated, and fitted into a straight line (Fig. 5). Here,

interestingly, we notice that, during considered time period, the behavior of asymmetry

changes from North to South hemisphere in the year 1998-99 for SN, SA, Q and SXR

whereas asymmetry of SAP changes from North to South in the year 1997. From Fig. 5 it

is clearly evident that the slopes are negative for each activity which again supports our

previous observation that the activities are Southern Hemisphere dominant. To

understand the behavior of DSAF with respect to SN, correlations were obtained between

DSAF and SN (Fig. 6) and following points were noticed; (i) Higher correlation

(positive) for SA and Q (ii) Moderate correlation (positive) for SXR and SPE and (iii)

Poor correlation (negative) for SAP. In Fig. 7 we have plotted the annual asymmetry

index of DSAF. Yearly N-S asymmetry of DSAF where highly significant, significant

and insignificant values are marked with filled square (■), circle (●) and triangle ()

respectively, using 2 - test (equation 2). Significance level of N-S asymmetry is also

represented in Table 3. SXR flare, SA and SAP have larger number of highly significant

values as compared to SN and Q.

4. Discussion and Results:

We have presented a comparative study of activity between cycles 22, 23 using

DSAF. In Table 1 we have represented the minimum to maximum variability of the

DSAF during cycle 22 and 23. In column 5 of this table all the features except SAP show

values greater than 1, which means that the activity in rising phase of solar cycle 22 is

higher than the solar cycle 23. The SAP shows negative value because there are very less

number of SAP observed in maximum phase compared to minimum phase of solar cycle

23. In column 6 all the features show values greater than 1, which means that the activity

in solar cycle 22 is higher than solar cycle 23. The number of SAP events is 27.47 times

larger in decay phase of cycle 22 than solar cycle 23. During the time of increased

amplitude of solar activity we would expect short-period cycles and during the times of

decreased amplitude of solar activity we would expect loner-period cycles as in cycle 23

(Hathaway et al., 2002). There is enough evidence to support that the chosen cycle 23 is

7

magnetically weak. This peculiarity is clearly evident from comparison of DSAF during

cycle 22 and 23 (Fig. 1). Even-Odd (or Gnevyshev, G-O) effect (Gnevyshev and Ohl,

1948) is seen in the monthly averaged or smoothed wolf sunspot numbers (1749-2003)

where the odd-numbered cycle amplitudes are compared with the amplitudes of the

preceding even-numbered cycles. Our results show the violation of G-O rule in cycle 23

for DSAF.

We have also presented the N-S asymmetry of DSAF for solar cycle 23 and the

obtained results are discussed below. Earlier studies by Verma (1992, 93); Ataç and

Özgüç, (1996, 2006) and Li et al. (2002) gave the dominant Hemisphere of solar activity

in each of solar cycles 12 to 22 and inferred that a Southern dominance of solar activity

should occur in solar cycle 23. Recently Li et al. (2009) and Joshi et al. (2009) found out

the Southern dominances of SA, grouped SN and different groups of SAP respectively.

Our results support the predictions. This finding is further confirmed in the present study

by investigation of the cumulative counts of DSAF number for the Northern and

Southern Hemispheres during considered time. It is found that all the features except SPE

and Q show a small spacing during the rising and maximum phase whereas a

considerable spacing (Southern dominances) between the two cumulative lines during the

end phase of solar cycle 23 (Fig. 4). Vizoso and Ballester, 1990; Ataç and Özgüç, 1996;

Li et al., 2002 and Joshi and Joshi, 2004; found regularity in their studies of different

activity parameters that for each four cycles the slope of the fitting straight lines of the N-

S asymmetry values changes its sign. The solar activity of cycle 23 is very important for

demonstrating the existence of these regularities. We have also demonstrated the

Southern dominance of solar activity in cycle 23 with the help of linear fitting of monthly

asymmetry index values of DSAF (see Fig. 5), which is similar to solar cycles 20, 21 and

22 as the obtained slopes are negative. Yearly N-S asymmetry of DSAF shows similar

type of variation during cycle 23 (Fig. 7). In our study, we observe the DSAF show

periodic behavior form 1996 to 2001. N-S asymmetry for SA, SXR, Q and SAP favors

Southern Hemisphere in the year 1996. In 1997, 1999 and 2000 all the activity

asymmetries move to the Northern Hemisphere. These shift to South again in 1998 and

beyond 2001, where these strongly favor the Southern Hemisphere. It also has been

found that the variation of N-S asymmetry of SPE has an alternating nature during whole

cycle. Temmer et al. (2001) and Joshi et al. (2009) analyzed the N-S asymmetry of Hα

8

flares and SAP and found high statistical significance of N-S asymmetry. We have also

found highly significant values of all DSAF (Table 3), which is in agreement with

previous studies (Temmer et al., 2001; Joshi and pant, 2005).

The physical interpretation of the asymmetry in the solar activity has not been given

clearly so far. However, Hathaway (1996), argued that the fluctuations in the meridian

flow, believed to be a product of turbulent convection and variations in the gradient of the

rotation rate, contributed to the cycle amplitude variations. The Sun’s magnetic activity is

generally believed to be supplied by a hydro magnetic dynamo operating either in or at

the base of the solar convective zone (Pulkkine et al. 1999). Zhao and Kosovichev (2004)

have found out that meridian flows vary with the location of the solar activity belts. By

applying time-distance helioseismology measurements, it is demonstrated that the activity

belts which were located towards the pole side of the faster zonal bands migrated together

towards the solar equator around the maximum phase of the solar cycle 23 and their

synoptic maps show unsymmetrical zonal flows in the Northern and Southern

Hemispheres (Haber et al. 2002). Zaatri et al. (2006) also found the zonal flow is larger in

the Southern Hemisphere than the Northern one, and N-S asymmetry increases with

depth. These explanations are only suggestive and more observations of local

helioseismology are needed to understand the N-S asymmetry of DSAF.

Acknowledgement

Authors, NSB and NCJ are thankful to UGC, New Delhi, India for financial assistance

under RFSMS (Research Fellowship in Science for meritorious students) scheme.

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10

Tables

Table 1: Rising and decay phase variability of DSAF during solar cycle 22 and 23.

DSAF: Cycles 22

and 23

1986

Minimum

1989-1991

Maximum

1996

Minimum

2000-2002

Maximum

2008

Minimum

Rising

phase

cycle22/

cycle23

Decay

phase

cycle22/

cycle23

Sunspot Number 13.4

(9.9)

148.6

(23.2)

8.6

(5.3)

111.5

(19.4)

2.9

(2.4) 1.31 1.29

Sunspot Area 124.7

(134.7)

2366.0

(654.8)

81.9

(80.1)

1716.8

(562.1)

22.78

(39.6) 1.37 1.35

Flare Index 1.2

(1.4)

14.9

(4.6)

0.4

(0.4)

6.3

(4.3)

0.46

(0.7) 2.32 2.48

H flare

730

(54.6)

20816

(117.8)

280

(18.1)

11294

(146.6)

125

(30.6) 1.82 1.84

x-ray flare 916

(62.8)

8538

(58.5)

515

(30.1)

8085

(53.6)

86

(10.2) 1.01 1.003

Solar active

Prominence

3095

(127.1)

33891

(130.28)

2213

(63.8)

1163

(24.7)

10

(1.2) -29.33 27.47

11

Table 2: Total number of DSAF in Northern and Southern Hemisphere during solar cycle

23.

Solar Active

Feature

Total

Number

Total

Number

(N+S)

Total North

Number (%)

Total South

Number (%)

Dominant

Hemisphere

SAP 8539 8426 4018

(47.69%)

4408

(52.31%) S

SXR 23,335 12,127 5131

(42.31%)

6996

(56.69%) S

SPE 72 71 36

(50.7%)

35

(49.3%) -

SN

(monthly mean) - 682

322.1

(47.22%)

359.9

(52.78%) S

SA

(monthly mean) - 10091.16

4690.1

(46.48%)

5401.06

(53.52%) S

Q

(yearly) - 443.53

212.95

(50.26%)

230.58

(49.74%) -

12

Table 3: Significance level of DSAF during solar cycle 23 using 2 -test.

Solar Active

Feature

Highly

Significant Significant Insignificant

SAP 8 1 4

SXR 11 2 0

SPE 4 5 4

SN

(monthly mean) 5 3 5

SA

(monthly mean) 10 2 1

Q

(yearly) 6 2 4

13

0 24 48 72 96 120 1440

50

100

150

0 24 48 72 96 120 1440

750

1500

2250

0 24 48 72 96 120 1440

75

150

225

300

0 24 48 72 96 120 1440

200

400

600

0 24 48 72 96 120 1440

5

10

15

20

0 24 48 72 96 120 1440

250

500

750

1000

SUN

SPO

T N

UM

BE

R

SC 22

SC 23

SC 22

SC 23

SUN

SPO

T A

RE

A

X-R

AY

FL

AR

E SC 22

SC 23

H

FL

AR

E SC 22

SC 23

FLA

RE

IN

DE

X

Time (11-Monthly running mean)

SC 22

SC 23

SOL

AR

AC

TIV

E P

RO

MIN

EN

CE

S

Time (11-Monthly running mean)

SC 22

SC 23

Figure 1: Comparison of the monthly mean of the SXR, SA, SN, Hα flare, Q and SAP

for the solar cycle 22 and solar cycle 23.

14

0

40

80

0

1000

2000

0

75

150

0

4

8

0

150

3000

1

2

SN

Time (Years)

SA

SX

R

Q

SA

P

SP

E

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Figure 2: Monthly number of solar proton events (SPE), solar active prominences (SAP),

Flare index (Q), Hα flare, soft X-ray flare (SXR), monthly mean sunspot area (SA) and

monthly mean sunspot number (SN) respectively in the Northern (the black line) and

Southern (the red line) Hemispheres from 1996-2008 (from top to bottom ).

15

0 36 72 108 1440

20

40

60

0 24 48 72 96 120 144 168-1.0

-0.5

0.0

0.5

1.0

0 36 72 108 1440

200

400

600

800

1000

1200

0 24 48 72 96 120 144 168-1.0

-0.5

0.0

0.5

1.0

0 36 72 108 1440

20

40

60

80

100

0 24 48 72 96 120 144 168-1.0

-0.5

0.0

0.5

1.0

0 36 72 108 1440

1

2

3

4

5

6

0 24 48 72 96 120 144 168

-0.5

0.0

0.5

0 36 72 108 1440

50

100

150

0 24 48 72 96 120 144 168

-0.5

0.0

0.5

0 36 72 108 1440.0

0.5

1.0

0 24 48 72 96 120 144 168

-0.5

0.0

0.5

SU

NS

PO

T N

UM

BE

R NORTH

SOUTH

SUNSPOT NUMBER

N-S

AS

YM

ME

TR

Y

NORTH

SOUTH

SU

NS

PO

T A

RE

A

SUNSPOT AREA

N-S

AS

YM

ME

TR

Y

NORTH

SOUTH

X-R

AY

FL

AR

E

X-RAY FLARE

N-S

AS

YM

ME

TR

Y

NORTH

SOUTH

FL

AR

E I

ND

EX FLARE INDEX

N-S

AS

YM

ME

TR

Y

NORTH

SOUTH

PR

OM

INE

NC

ES SOLAR ACTIVE PROMINENCES

N-S

AS

YM

ME

TR

Y

NORTH

SOUTH

SO

LA

R P

RO

TO

N E

VE

NT

Time (11-Month running mean)

SOLAR PROTON EVENTS

N-S

AS

YM

ME

TR

Y

Time (11-Month running mean)

Figure 3. Monthly plots of N-S asymmetry of the SN, SA, SXR, Q, SAP and SPE and

Gnevyshev gap time occurrence.

16

0

100

200

300

400

0

1500

3000

4500

6000

0

2000

4000

6000

8000

0

50

100

150

200

250

1995 1998 2001 2004 2007

1000

2000

3000

4000

1995 1998 2001 2004 2007

0

9

18

27

36

north (47.22%)

south (52.78%)

SN

north (46.48%)

south (53.52%)

SA

north (42.31%)

south (56.69%)

SX

R

north (50.26%)

south (49.74%)

Q

north (47.69%)

south (52.31%)

SA

P

Time (Years)

north (50.7%)

south (49.3%)

SP

E

Time (Years)

Figure 4: Cumulative monthly mean sunspot number (SN), monthly mean sunspot area

(SA) number of soft X-ray flare (SXR), Hα flare index (Q), solar active prominences

(SAP) and solar proton events (SPE) respectively in the Northern Hemisphere (the black

lines) and the Southern Hemisphere (the red lines) from 1996-2008.

17

-1.0

-0.5

0.0

0.5

1.0

-1.0

-0.5

0.0

0.5

1.0

-1.0

-0.5

0.0

0.5

1.0

-1.0

-0.5

0.0

0.5

1.0

-1.0

-0.5

0.0

0.5

1.0

-1.0

-0.5

0.0

0.5

1.0

SN

SA

SX

R

Q

SA

P

Time (Years)

Time (Years)

SP

E

1995 1998 2001 2004 2007

1995 1998 2001 2004 2007

Figure 5: Fit of a regression straight line to the monthly values of the North-South

asymmetry of monthly mean sunspot number (SN), monthly mean sunspot area (SA)

number of soft X-ray flare (SXR), Hα flare index (Q), solar active prominences (SAP)

and solar proton events (SPE)respectively from 1996-2008.

18

750

1500

2250

3000

0

75

150

225

0

3

6

9

12

0

100

200

300

400

0

1

2

3

4

r = 0.92

SA

r = 0.60

SX

R

r = 0.73

Q

r = - 0.13

SA

P

SN

r = 0.47

SP

E

SN1995 1998 2001 2004 2007 2010

1995 1998 2001 2004 2007 2010

Figure 6: Correlation plot of the monthly mean sunspot area (SA), soft X-ray flare

(SXR), Hα flare index (Q), solar active prominences (SAP) and solar proton events (SPE)

with monthly mean sunspot number (SN); r indicates the correlation coefficient.

19

1996 1998 2000 2002 2004 2006 2008-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

N-S

Asy

mm

etry

Time (Years)

SN

SA

XR

FI

SAP

SPE

Figure 7: Plot of N-S asymmetry of Various Solar Active Phenomena versus years.

Highly significant, significant and insignificant values marked with filled square (■),

circle (●) and triangle () respectively from 1996-2008.

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