- Email: [email protected]
Evolution of network magnetic fields of solar quiet regions
Pergamon Journals. Printed in Great Britian 0275-1062/87$10.00+.00
Chin.Astron.Astrophys.11 (1987) 221-228 28 (1987) 111-119 -
Act.Astron.Sin.
EVOLUTION
OF NETWORK
SHI Zhong-xian Beijing
MAGNETIC
FIELDS
OF SOLAR
QUIET
REGIONS
and WANG Jing-xiu
Observatory,
Academia
Sinica
Received 1986 January 21
ABSTRACT There are 4 types of evolution patterns of network magnetic fields: (1) flux cancellation, the mutual disappearance of encountering fluxes of opposite polarity, (2) flux increase by emergence of ephemeral regions, (3) flux decrease of one polarity and (4) flux increase of one polarity, without emergence of ephemeral regions. From a time sequence of magnetograms of a quiet region of 1983 October 14, the evolution of 300 network features was measured. The magnetograms have a spatial resolution of 2 to 3 arcsec and a time resolution of about 2 hr. The statistics show that the contribution to flux decrease by Type 3 is 1.28 times that bv Tvoe 1. and the contribution to flux increase by Type 4 is 7 times that'by'Type'2.
Figures l-5 show selected portions of the original magnetograms (222"x266"). The Research on network magnetic fields of solar size of picture is 37"x46" in Figs. 1. 2. 3 and 5, and 49"x43" in Fig. 4. Pisitive quiet regions began only a few years ago. In 1983, Martin, Livi and we [l-4] discovered polarity is shown by solid lines, negative, the phenomenon of flux cancellation, and dashed lines. The features are represented Wilson, Simon, Topka, Tarbell and Title by contour lines, the starting contour is [5-71 discovered one-polarity flux increases lOG, then 40G, 80G and 160G. Each picture in this paper is the result and decreases, arousing the attention of of superpositionof 1024 original frames. The researchers on the studyofsmall scale magnetic fields. What are the cancellations superpositiontook 68 seconds of computer time. It raised the accuracy of the field and the one-sided variations physically? What roles do they play in the evolution of measurement at the expense of spatial resolution. In our maps, the measuring the field in quiet regions? To answer accuracy of the field is 7-8G and the spatial these questions, we investigate here the resolution is 2 - 3". The date and time of evolution of the network fields. observation is marked on the corners, e:g. 1824 for 18h24m. In the figures, P stands 2. OBSERVATIONAL DATA for positive and N for negative polarity, PN for flux cancellation, EF for ephemeral region, PD or ND for one-polarity decrease, The data we use is the longitudinal magnetograms obtained by the VMG of the Big PC or NC for one-polarity increase. Suffix Bear Solar Observatory. The telescope has is serial number of the feature. a lo-inch aperature and a Zeiss filter centered on CaI 6103 A, with half-width 0.25 A, and adjustable range *16 A. A calibration 3. THE FOUR EVOLUTION PATTERNS of the magnetograms has been obtained by Patterson and us, [8], which is entirely Type 1: Flux Cancellation There are 25 such suitable for magnetic fields in quiet regions cases in Figs. l-5. For Case Nos. 12 and 13 The magnetograms used here were obtained W12 and PN131, the opposite polarities between October 10 and 14, (13 lacking) 1983. approached each other with velocities 0.22 The filter transmission band was adjusted so km/s and 0.26 km/s. These values are about 3 that the radial velocity at the centre of times the values we found for decaying the apparent disk was zero. activity regions. The following data for 1.
INTRODUCTION
222
SHI and WANG
Fig. 1 Videomagnetogramson 1983 Ott 10 (Dashed line, negative; solid line, positive)
Fig. 2
~'ideomagnetograms on 1983 Ott 11
such cases is given in TABLE 1: magnetic flux, maximum field intensity and the area occupied in pixels, each pixel corresponding to 1.26 (+15) cm2 of solar surface. The largest amount of flux cancellation was shown by No.5 (12.5 (+18) Mx), the second largest, by No.14 (7.4 (+18) Mx), then No.13 (3.9 (+18)
Mx), then Nos. 8 and 16 (4.6 (~18) Mx). The average decrease over the 19 cases of TABLE 1 is 4.1 (+18) Mx. The time interval was 320 mins (same throughout). The decreases in positive and negative polarity fluxes by cancellation are not equal. Possibly it is because we measured only the
Network Magnetic Fields
Fig. 3
223
Videoma~etograms on 1983 Ott 11-12
was mainly the result of a decrease in area occupied by the feature. Probably here the network field is evolving towards withinnetwork field and is not accompanied with a Type of Ephemeral Regions ._ 2:. Appearance . After their discovery by Harvey and Martin sinking of the feature. On the other hand, in Case Nos. 15 and 20, the area remains [9], true and false cases proved to be basically constant, and hence sinking is difficult to distinguish. This led Martin et al. [33 to propose a new criterion. Using probably dominant. The average flux decrease this new criterion, we could find 8 such over the 20 cases is 4.1 (+18) Mx, same as cases in this data. The largest velocity the average decrease in the cancellation of separation was 0.78 km/s (EFs), followed cases. by 0.62 km/s (EFl), 0.28 km/s (EF?), 0.25 Type 4: One Polarity Flux Increase (with no km/s (EF;). EF8 first separated then reapproached, the velocity of approach was obvious appearance of ephemeral regions). 0.33 km/s, this was interpreted by Zirin [IO] TABLE 3 lists 24 instances. For Nos. 3, S, as sinking in his study of active regions. 21, the maximum field intensity varied little The lines joining P to N did not obey the and the change in magnetic flux was mainly law of sunspot appearance (for Cycle 21, the the result of small pieces combining into leading spot is P in the northern, and N in larger ones, of the within-network fields the southern hemisphere) and were not close gathering into network fields. For Nos. 10, to parallelism with the solar equator as 24, 4, however, the change in area was small, expected, rather, inclined at angles greater and the change in field intensity was large, and it is probable that, in these cases, the than 30° in most cases (nearly 70° in EF2 magnetic feature rose from the bottom layer and EF5), averaging 38'. This may be a of the photosphere. The average flux increase consequence of ephemeral regions called over the 24 instances is 5.7 (+18) t+x. "ephemeral active regions" by some, and In summary, to ascertain whether these ordinary active regions (characterisedby sunspots) originating in different layers, four types of features are accompanied by a as noted by Martin ill]. sinking or a rising motion we must seek corroboration from the velocity field data. 'l'ype 3: One-Polarity Flux Decrease (with no clear cancellation between the two polarities) 4. STATISTICS OF EVOLUTION TYPES TABLE 2 lists 20 such cases. For Case Nos. 1, 3, 4, 8, the maximum field intensity was The statistics are based on the data of basically unchanged, and the change in flux October 14. Taking into account the effect longitudinal component and included only features greater than 106.
224
SHI and WANG
Network Magnetic Fields
Fig. 5
225
Videomag~oetgr~s on 1983 Ott 12-14
Flu::
TABLE 1
CaceLlation
Flux in Kaxwells. 3.04 18 for 3.04~10'" etc.
l-
before
‘a &
)efore
T
AREA
(G)
after
before
I
after
I
NOTES
18
1.8
17
32
14
142
13
4.78
I8
2.04
I8
38
29
184
56
3
2.04
18
I.12
18
23
21
102
64
4
2.64
18
2.t
17
44
17
9s
I3
5
2.18
19
9.26
I8
106
48
617
377
6
5.14
I8
2.88
18
44
30
183
148
7
3.06
18
1.03
18
29
23
139
57
8
7.08
18
2.48
18
37
24
341
139
9
3.44
18
2.28
I8
33
24
146
132
10
1.88
18
1.3
17
22
15
98
9
1.09
18
1.3
i7
27
IS
14
9
1.45
18
6
16
22
iz
82
4
13
1.51
19
1.12
19
92
57
344
2L4
PN,, PN,. PN,.
I4
3.08
19
2.34
19
68
69
1032
730
P&I-,,
I5
8.3
17
3.6
17
28
14
37
24
4.58
18
139
0
PN, PN,,
1.32
18
i 17
61
17
I 1.9
63
13
18
2.04
18
1
16
74
I
19
1.45
18
6
16
82
4
11 I2 : .ri CI % 2
after
I'IAX.FIELD
3.04
2 : .ti .':
r
FLUX
16
!
’
._ --
25
Cl0 I6
SHI
126
Oae-Polarity
TABLE 2
POLARITY
l;ERIAL IUYBER
Decrease
i&X. FIELD (G)
i
before
Flux
-
FLUX
efore
after
1
AREA
I
1
1.02
19
8.1
18
21
37
lfter -37
2
I.77
18
9.7
16
94
26
12
91
3
4.26
I8
2.92
I8
33
27
28
208
4
8.78
18
4.58
18
48
36
36
368
242
S
6.24
19
4.62
19
26
136
I22
1662
1201
6
3.44
18
2.28
J8
34
33
26
146
132
7
1.87
19
1.31
19
30
67
42
695
520
8
1.10
19
6.82
IE
38
45
43
388
271
9
3.44
I8
1.66
18
52
34
22
147
99
10
4.24
18
2.10
18
SI
34
28
174
101
11
6.24
19
4.62
i9
26
136
I22
1480
1201
12
2.22
19
1.70
19
23
114
90
533
46s
13
4.70
16
3.70
18
21
43
30
220
165
14
5.54
18
2.28
18
59
51
21
278
147
15
2.00
19
1.44
19
28
69
45
562
556
16
6.66
18
3.90
18
41
54
38
264
169
17
2.88
18
1.50
18
48
30
20
131
83
18
4.78
18
2.56
18
46
40
27
191
134
19
4.68
18
2.42
18
48
40
21
200
148
20
3.30
18
2.56
18
22
33
22
160
159
TABLE
POLARITY
and WANG
;ER IAL IWBER
r
One-Polarity
3
FLUX
If-
3efore
1
3.18
18
4.28
18
2
8.48
18
1.36
19
3
1.69
19
2.66
4
9.72
IS
1.41
5
3.10
18
6
4.22
7
2.70
8
fter
1
NOTES
370
430
2
PD,
152
I’D,
ND,
Decrcnse
i- MAX.FIELD (G) after
before
Flux
--
before
after
T-
AREA
3efore
I
after
NOTES
28
3s
163
194
43
66
363
462
19
85
85
648
i86
19
49
63
402
4S3
4.50
19
92
96
911
1280
18
7.42
18
22
35
244
362
18
4.20
18
20
31
163
227
I.03
18
2.26
18
IS
27
72
122
9
3.22
18
1.04
19
23
40
185
458
10
6.48
18
9.52
18
32
56
300
326
11
4.76
18
1.55
19
35
68
198
473
12
2.32
18
4.42
18
13
2.86
19
4.0
19
88
120
821
14
7.06
17
2.46
18
17
19
47
1S
5.34
17
3.18
18
14
2s
37
193
16
6.42
18
1.10
19
24
54
326
442
17
2.38
18
8.48
18
27
48
119
354
18
3.78
18
6.86
18
3s
46
185
263
19
1.89
18
7.90
is
18
32
127
383
20
1.78
I8
3.00
IS
24
so
93
129
21
4.58
18
6.68
18
49
52
165
247
22
5.08
17
5.54
18
14
42
36
24s
23
2.12
19
2.88
19
61
103
771
923
NC,
24
2.20
18
3.16
18
22
34
:32
147
NC,
--
127
248 ii90
NC.
154
NC,
Network
TABLE 4 EVOLUTION TYPE
POSITIVE before
Magnetic
Statistics
POLARITY
1
of
Evolution
before
after
227
Types VARIATION
NEGATIVE PLOARITY after
165.3
18
87.8
18
128.2
18
309.2
r8
208.1
18
115.7
708.4
18
198.6
AF
I
%
83.6
18
122.1
18
3.8
18
61.0
18
122.9
l’8
4.9
18
173.6
18
79.9
18
--
2.1
17.2
18
26.4
18
43.6
18
1.4
546.6
18
216.8
18
348.4
18
304.8
18
9.6
598.1
18
334.1
18
3S0.S
18
43.6
18
1.4
of seeing (see next Section), we should regard the data as reliable only when the flux variation is 20% or greater. Only these data are included in the statistical analysis. Those with-flux variations be-low 20%.are included in TABLE 4 without classification into different.types. For Type 2 features (ephemeral regions), the flux “before” is essentially 0, and those with fluxes below 0.5(+18) Mx are not included. Of all the features that-resulted in a decrease in- flux, 22% have flux variations below 20%; of the other 78%, 34% are of Type 1 (flux cancellation) and 43% are of Type 3 (one-polarity flux decrease). In other words, the number of Type 3 features that gave- a significant flux decrease is 1;28-times that-of Type.1 features that-did so. Also, the number of Type 4 (one-polarity flux increase) features that gave a significant (>20%) flux-increase is as much as 7 times that of Type 2 (ephemeral regions) features.
5.
Fields
an- intrinsic B(r)
Gaussian
profile
B,,.exp(-r’/a’).
-
(1)
and. the effect of seeing ca.n also be expressed by a Gaussian broadening function exp(-c2/n2) th- observed profile will be a convolution of the two. B(r)ob
-
u’Bm~~ -eexd-r’/(u’+ 6')
(u’ +
b')].
Calculation will show that the effect of seeing will be less than 16%. If we take a fan-shaned profile, [2],
then calculation will again show the effect or seeing to he less than 16%. Therefore, it is reasonable to take 20% as the fiducial line and regard as reliable those flux variations greater than this size.
THE EFFECT OF SEEING 6.
It is generally thought that seeing does not affect the measurement of the flux-of network Bat this is true only for the case of field. one single polarity; when features of opposite polarities are very close tooether, e.g., within 2”, then the measurement will Not- to mention the fact that be affected. when the noise. -(background magnetic field) is as high as 7-8 G, only features 10 G or more can be picked out from the background; Hence, when the seeing is poor, the fluxfrom features with fluxes below 10-G will be a corsiderablr portion. of the flux-from all features. Of the nearly 300 features in the October 14 material, 16 had fluxes above 108 G aud these had an average flux-variation of zFbefore
- EFafter’EFbofore
s 4%
This shows the relative stability of large network fields and also reflects the, reliability of the.magnetogram calibration. If we assume the magnetic features have
SUMARY
The network fields of quiet regions have four evolution patterns: 1. Cancellation. Positive and negative polarities approach each other and the flux decreases. The average decrease (over 320 min, averaged over 19 features of TABLE 1) was found to be 4.1 (+18) Mx, and the average velocity of approach, 0.2 km/s. Whether flux cancellation is accompanied by field reconnccti.ons and sinking is difficult to decide at the present. 2. Ephemeral Regions. Both polarities appear together with a velocity of separation above 0.2 km/s (may be as large as 0.8 km/s). In one instance, the separation was followed by re-approach, followed by a decrease in flux and a sinking. The fluxes (lonpitudinal component) of the two polarities are not eo_ua1 . There Clne-polarity Flux Decrease. 3. are two kinds. In one, the maximum field intensity remains nearly the same while thL area of the feature decreases; in the other
228
SHI and WANG
form of flux decrease in quiet regions, a the area remains nearly constant while the somewhat more common form is one-polarity field intensity decreases, in this case, flux decrease, which is more difficult to sinking is possible. Average decrease over understand than cancellation. Similarly, 20 instances was 4.1 (+18) Mx. one-polarity flux increase is hard to One-Polarity Flux Increase. There are 4. understand and accept. also two kinds similar to the two kinds in 3. Here the evolution is from a within-network ACKNOWLEDGEMENT We thank Dr. H. Zirin, field towards a network field, or a rising of the Big Bear Solar Observatory from the bottom layer of the photosphere. The Director for support; S.F. Martin, S.H.B. Livi and average flux increase over 24 instances was F. Tang for valuable opinions and Dr. Alan found to be 5.7 (+18) Mx. Pattern for help in using the instruments. In summary, the statistics of the October 14 data show that cancellation is not the only
REFERENCES ( 11 I2 I ( 31
Marlin, S. F., Livi, S. H. B., Wang. 1.. Aurt. J. Plgr. 38(1985), 6, 929. Livi, S. J-3. B., Wang, Jr., Martin, S. F., AU*. J. Ply. 38(1985), 6, 1~55. Marlin, S. F., Livi, S. H. B., Wang, J., Shi, Z., 1984. “hterrurcmentr of Bohr p. 403. (NASA Conf. Publa No2374)
r 4 ]
Wang,
[ 5 1
Wilson,
I6
I
[ 7 1
[ 81 [ Y1 [IO]
Simun,
J., G.
W.,
H., Shi,
Z..
S&r
Plyr.
98(1985),
G. W., Ap. .I.. 273(1983),
Simon,
P. R., Ap. 1..
Wilson,
295(1985),
Harvey,
K.
Zirin, H.,
L..
Martin,
Ap. 3.. F.,
S. L. Keil) Bumba, V.,
S. F..
291(1985),
Proc.
Symp.
Solar
Phyr.,
Magnetic
Fields”,
241.
805. 541.
Topka, K. P., Tarbell, T. D., Title, A. M., Ap. .I., Shi, Z., Wang, J., Patterron. A., BBSO, 257.
[I 11 Martin, S. [12]
Zirin,
P. R.,
~~~~~~
32(1973),
306(1986),
304.
389.
858. on Small
Izv.Krym.Astr.0b.s.
Scale Dynamical 23
(1960)
Procerrer 212.
in Quiet Srcllrr
Atmoapbezec,
p. 30. (Ed.
Chin.Astron.Astrophys.11 (1987) 221-228 28 (1987) 111-119 -
Act.Astron.Sin.
EVOLUTION
OF NETWORK
SHI Zhong-xian Beijing
MAGNETIC
FIELDS
OF SOLAR
QUIET
REGIONS
and WANG Jing-xiu
Observatory,
Academia
Sinica
Received 1986 January 21
ABSTRACT There are 4 types of evolution patterns of network magnetic fields: (1) flux cancellation, the mutual disappearance of encountering fluxes of opposite polarity, (2) flux increase by emergence of ephemeral regions, (3) flux decrease of one polarity and (4) flux increase of one polarity, without emergence of ephemeral regions. From a time sequence of magnetograms of a quiet region of 1983 October 14, the evolution of 300 network features was measured. The magnetograms have a spatial resolution of 2 to 3 arcsec and a time resolution of about 2 hr. The statistics show that the contribution to flux decrease by Type 3 is 1.28 times that bv Tvoe 1. and the contribution to flux increase by Type 4 is 7 times that'by'Type'2.
Figures l-5 show selected portions of the original magnetograms (222"x266"). The Research on network magnetic fields of solar size of picture is 37"x46" in Figs. 1. 2. 3 and 5, and 49"x43" in Fig. 4. Pisitive quiet regions began only a few years ago. In 1983, Martin, Livi and we [l-4] discovered polarity is shown by solid lines, negative, the phenomenon of flux cancellation, and dashed lines. The features are represented Wilson, Simon, Topka, Tarbell and Title by contour lines, the starting contour is [5-71 discovered one-polarity flux increases lOG, then 40G, 80G and 160G. Each picture in this paper is the result and decreases, arousing the attention of of superpositionof 1024 original frames. The researchers on the studyofsmall scale magnetic fields. What are the cancellations superpositiontook 68 seconds of computer time. It raised the accuracy of the field and the one-sided variations physically? What roles do they play in the evolution of measurement at the expense of spatial resolution. In our maps, the measuring the field in quiet regions? To answer accuracy of the field is 7-8G and the spatial these questions, we investigate here the resolution is 2 - 3". The date and time of evolution of the network fields. observation is marked on the corners, e:g. 1824 for 18h24m. In the figures, P stands 2. OBSERVATIONAL DATA for positive and N for negative polarity, PN for flux cancellation, EF for ephemeral region, PD or ND for one-polarity decrease, The data we use is the longitudinal magnetograms obtained by the VMG of the Big PC or NC for one-polarity increase. Suffix Bear Solar Observatory. The telescope has is serial number of the feature. a lo-inch aperature and a Zeiss filter centered on CaI 6103 A, with half-width 0.25 A, and adjustable range *16 A. A calibration 3. THE FOUR EVOLUTION PATTERNS of the magnetograms has been obtained by Patterson and us, [8], which is entirely Type 1: Flux Cancellation There are 25 such suitable for magnetic fields in quiet regions cases in Figs. l-5. For Case Nos. 12 and 13 The magnetograms used here were obtained W12 and PN131, the opposite polarities between October 10 and 14, (13 lacking) 1983. approached each other with velocities 0.22 The filter transmission band was adjusted so km/s and 0.26 km/s. These values are about 3 that the radial velocity at the centre of times the values we found for decaying the apparent disk was zero. activity regions. The following data for 1.
INTRODUCTION
222
SHI and WANG
Fig. 1 Videomagnetogramson 1983 Ott 10 (Dashed line, negative; solid line, positive)
Fig. 2
~'ideomagnetograms on 1983 Ott 11
such cases is given in TABLE 1: magnetic flux, maximum field intensity and the area occupied in pixels, each pixel corresponding to 1.26 (+15) cm2 of solar surface. The largest amount of flux cancellation was shown by No.5 (12.5 (+18) Mx), the second largest, by No.14 (7.4 (+18) Mx), then No.13 (3.9 (+18)
Mx), then Nos. 8 and 16 (4.6 (~18) Mx). The average decrease over the 19 cases of TABLE 1 is 4.1 (+18) Mx. The time interval was 320 mins (same throughout). The decreases in positive and negative polarity fluxes by cancellation are not equal. Possibly it is because we measured only the
Network Magnetic Fields
Fig. 3
223
Videoma~etograms on 1983 Ott 11-12
was mainly the result of a decrease in area occupied by the feature. Probably here the network field is evolving towards withinnetwork field and is not accompanied with a Type of Ephemeral Regions ._ 2:. Appearance . After their discovery by Harvey and Martin sinking of the feature. On the other hand, in Case Nos. 15 and 20, the area remains [9], true and false cases proved to be basically constant, and hence sinking is difficult to distinguish. This led Martin et al. [33 to propose a new criterion. Using probably dominant. The average flux decrease this new criterion, we could find 8 such over the 20 cases is 4.1 (+18) Mx, same as cases in this data. The largest velocity the average decrease in the cancellation of separation was 0.78 km/s (EFs), followed cases. by 0.62 km/s (EFl), 0.28 km/s (EF?), 0.25 Type 4: One Polarity Flux Increase (with no km/s (EF;). EF8 first separated then reapproached, the velocity of approach was obvious appearance of ephemeral regions). 0.33 km/s, this was interpreted by Zirin [IO] TABLE 3 lists 24 instances. For Nos. 3, S, as sinking in his study of active regions. 21, the maximum field intensity varied little The lines joining P to N did not obey the and the change in magnetic flux was mainly law of sunspot appearance (for Cycle 21, the the result of small pieces combining into leading spot is P in the northern, and N in larger ones, of the within-network fields the southern hemisphere) and were not close gathering into network fields. For Nos. 10, to parallelism with the solar equator as 24, 4, however, the change in area was small, expected, rather, inclined at angles greater and the change in field intensity was large, and it is probable that, in these cases, the than 30° in most cases (nearly 70° in EF2 magnetic feature rose from the bottom layer and EF5), averaging 38'. This may be a of the photosphere. The average flux increase consequence of ephemeral regions called over the 24 instances is 5.7 (+18) t+x. "ephemeral active regions" by some, and In summary, to ascertain whether these ordinary active regions (characterisedby sunspots) originating in different layers, four types of features are accompanied by a as noted by Martin ill]. sinking or a rising motion we must seek corroboration from the velocity field data. 'l'ype 3: One-Polarity Flux Decrease (with no clear cancellation between the two polarities) 4. STATISTICS OF EVOLUTION TYPES TABLE 2 lists 20 such cases. For Case Nos. 1, 3, 4, 8, the maximum field intensity was The statistics are based on the data of basically unchanged, and the change in flux October 14. Taking into account the effect longitudinal component and included only features greater than 106.
224
SHI and WANG
Network Magnetic Fields
Fig. 5
225
Videomag~oetgr~s on 1983 Ott 12-14
Flu::
TABLE 1
CaceLlation
Flux in Kaxwells. 3.04 18 for 3.04~10'" etc.
l-
before
‘a &
)efore
T
AREA
(G)
after
before
I
after
I
NOTES
18
1.8
17
32
14
142
13
4.78
I8
2.04
I8
38
29
184
56
3
2.04
18
I.12
18
23
21
102
64
4
2.64
18
2.t
17
44
17
9s
I3
5
2.18
19
9.26
I8
106
48
617
377
6
5.14
I8
2.88
18
44
30
183
148
7
3.06
18
1.03
18
29
23
139
57
8
7.08
18
2.48
18
37
24
341
139
9
3.44
18
2.28
I8
33
24
146
132
10
1.88
18
1.3
17
22
15
98
9
1.09
18
1.3
i7
27
IS
14
9
1.45
18
6
16
22
iz
82
4
13
1.51
19
1.12
19
92
57
344
2L4
PN,, PN,. PN,.
I4
3.08
19
2.34
19
68
69
1032
730
P&I-,,
I5
8.3
17
3.6
17
28
14
37
24
4.58
18
139
0
PN, PN,,
1.32
18
i 17
61
17
I 1.9
63
13
18
2.04
18
1
16
74
I
19
1.45
18
6
16
82
4
11 I2 : .ri CI % 2
after
I'IAX.FIELD
3.04
2 : .ti .':
r
FLUX
16
!
’
._ --
25
Cl0 I6
SHI
126
Oae-Polarity
TABLE 2
POLARITY
l;ERIAL IUYBER
Decrease
i&X. FIELD (G)
i
before
Flux
-
FLUX
efore
after
1
AREA
I
1
1.02
19
8.1
18
21
37
lfter -37
2
I.77
18
9.7
16
94
26
12
91
3
4.26
I8
2.92
I8
33
27
28
208
4
8.78
18
4.58
18
48
36
36
368
242
S
6.24
19
4.62
19
26
136
I22
1662
1201
6
3.44
18
2.28
J8
34
33
26
146
132
7
1.87
19
1.31
19
30
67
42
695
520
8
1.10
19
6.82
IE
38
45
43
388
271
9
3.44
I8
1.66
18
52
34
22
147
99
10
4.24
18
2.10
18
SI
34
28
174
101
11
6.24
19
4.62
i9
26
136
I22
1480
1201
12
2.22
19
1.70
19
23
114
90
533
46s
13
4.70
16
3.70
18
21
43
30
220
165
14
5.54
18
2.28
18
59
51
21
278
147
15
2.00
19
1.44
19
28
69
45
562
556
16
6.66
18
3.90
18
41
54
38
264
169
17
2.88
18
1.50
18
48
30
20
131
83
18
4.78
18
2.56
18
46
40
27
191
134
19
4.68
18
2.42
18
48
40
21
200
148
20
3.30
18
2.56
18
22
33
22
160
159
TABLE
POLARITY
and WANG
;ER IAL IWBER
r
One-Polarity
3
FLUX
If-
3efore
1
3.18
18
4.28
18
2
8.48
18
1.36
19
3
1.69
19
2.66
4
9.72
IS
1.41
5
3.10
18
6
4.22
7
2.70
8
fter
1
NOTES
370
430
2
PD,
152
I’D,
ND,
Decrcnse
i- MAX.FIELD (G) after
before
Flux
--
before
after
T-
AREA
3efore
I
after
NOTES
28
3s
163
194
43
66
363
462
19
85
85
648
i86
19
49
63
402
4S3
4.50
19
92
96
911
1280
18
7.42
18
22
35
244
362
18
4.20
18
20
31
163
227
I.03
18
2.26
18
IS
27
72
122
9
3.22
18
1.04
19
23
40
185
458
10
6.48
18
9.52
18
32
56
300
326
11
4.76
18
1.55
19
35
68
198
473
12
2.32
18
4.42
18
13
2.86
19
4.0
19
88
120
821
14
7.06
17
2.46
18
17
19
47
1S
5.34
17
3.18
18
14
2s
37
193
16
6.42
18
1.10
19
24
54
326
442
17
2.38
18
8.48
18
27
48
119
354
18
3.78
18
6.86
18
3s
46
185
263
19
1.89
18
7.90
is
18
32
127
383
20
1.78
I8
3.00
IS
24
so
93
129
21
4.58
18
6.68
18
49
52
165
247
22
5.08
17
5.54
18
14
42
36
24s
23
2.12
19
2.88
19
61
103
771
923
NC,
24
2.20
18
3.16
18
22
34
:32
147
NC,
--
127
248 ii90
NC.
154
NC,
Network
TABLE 4 EVOLUTION TYPE
POSITIVE before
Magnetic
Statistics
POLARITY
1
of
Evolution
before
after
227
Types VARIATION
NEGATIVE PLOARITY after
165.3
18
87.8
18
128.2
18
309.2
r8
208.1
18
115.7
708.4
18
198.6
AF
I
%
83.6
18
122.1
18
3.8
18
61.0
18
122.9
l’8
4.9
18
173.6
18
79.9
18
--
2.1
17.2
18
26.4
18
43.6
18
1.4
546.6
18
216.8
18
348.4
18
304.8
18
9.6
598.1
18
334.1
18
3S0.S
18
43.6
18
1.4
of seeing (see next Section), we should regard the data as reliable only when the flux variation is 20% or greater. Only these data are included in the statistical analysis. Those with-flux variations be-low 20%.are included in TABLE 4 without classification into different.types. For Type 2 features (ephemeral regions), the flux “before” is essentially 0, and those with fluxes below 0.5(+18) Mx are not included. Of all the features that-resulted in a decrease in- flux, 22% have flux variations below 20%; of the other 78%, 34% are of Type 1 (flux cancellation) and 43% are of Type 3 (one-polarity flux decrease). In other words, the number of Type 3 features that gave- a significant flux decrease is 1;28-times that-of Type.1 features that-did so. Also, the number of Type 4 (one-polarity flux increase) features that gave a significant (>20%) flux-increase is as much as 7 times that of Type 2 (ephemeral regions) features.
5.
Fields
an- intrinsic B(r)
Gaussian
profile
B,,.exp(-r’/a’).
-
(1)
and. the effect of seeing ca.n also be expressed by a Gaussian broadening function exp(-c2/n2) th- observed profile will be a convolution of the two. B(r)ob
-
u’Bm~~ -eexd-r’/(u’+ 6')
(u’ +
b')].
Calculation will show that the effect of seeing will be less than 16%. If we take a fan-shaned profile, [2],
then calculation will again show the effect or seeing to he less than 16%. Therefore, it is reasonable to take 20% as the fiducial line and regard as reliable those flux variations greater than this size.
THE EFFECT OF SEEING 6.
It is generally thought that seeing does not affect the measurement of the flux-of network Bat this is true only for the case of field. one single polarity; when features of opposite polarities are very close tooether, e.g., within 2”, then the measurement will Not- to mention the fact that be affected. when the noise. -(background magnetic field) is as high as 7-8 G, only features 10 G or more can be picked out from the background; Hence, when the seeing is poor, the fluxfrom features with fluxes below 10-G will be a corsiderablr portion. of the flux-from all features. Of the nearly 300 features in the October 14 material, 16 had fluxes above 108 G aud these had an average flux-variation of zFbefore
- EFafter’EFbofore
s 4%
This shows the relative stability of large network fields and also reflects the, reliability of the.magnetogram calibration. If we assume the magnetic features have
SUMARY
The network fields of quiet regions have four evolution patterns: 1. Cancellation. Positive and negative polarities approach each other and the flux decreases. The average decrease (over 320 min, averaged over 19 features of TABLE 1) was found to be 4.1 (+18) Mx, and the average velocity of approach, 0.2 km/s. Whether flux cancellation is accompanied by field reconnccti.ons and sinking is difficult to decide at the present. 2. Ephemeral Regions. Both polarities appear together with a velocity of separation above 0.2 km/s (may be as large as 0.8 km/s). In one instance, the separation was followed by re-approach, followed by a decrease in flux and a sinking. The fluxes (lonpitudinal component) of the two polarities are not eo_ua1 . There Clne-polarity Flux Decrease. 3. are two kinds. In one, the maximum field intensity remains nearly the same while thL area of the feature decreases; in the other
228
SHI and WANG
form of flux decrease in quiet regions, a the area remains nearly constant while the somewhat more common form is one-polarity field intensity decreases, in this case, flux decrease, which is more difficult to sinking is possible. Average decrease over understand than cancellation. Similarly, 20 instances was 4.1 (+18) Mx. one-polarity flux increase is hard to One-Polarity Flux Increase. There are 4. understand and accept. also two kinds similar to the two kinds in 3. Here the evolution is from a within-network ACKNOWLEDGEMENT We thank Dr. H. Zirin, field towards a network field, or a rising of the Big Bear Solar Observatory from the bottom layer of the photosphere. The Director for support; S.F. Martin, S.H.B. Livi and average flux increase over 24 instances was F. Tang for valuable opinions and Dr. Alan found to be 5.7 (+18) Mx. Pattern for help in using the instruments. In summary, the statistics of the October 14 data show that cancellation is not the only
REFERENCES ( 11 I2 I ( 31
Marlin, S. F., Livi, S. H. B., Wang. 1.. Aurt. J. Plgr. 38(1985), 6, 929. Livi, S. J-3. B., Wang, Jr., Martin, S. F., AU*. J. Ply. 38(1985), 6, 1~55. Marlin, S. F., Livi, S. H. B., Wang, J., Shi, Z., 1984. “hterrurcmentr of Bohr p. 403. (NASA Conf. Publa No2374)
r 4 ]
Wang,
[ 5 1
Wilson,
I6
I
[ 7 1
[ 81 [ Y1 [IO]
Simun,
J., G.
W.,
H., Shi,
Z..
S&r
Plyr.
98(1985),
G. W., Ap. .I.. 273(1983),
Simon,
P. R., Ap. 1..
Wilson,
295(1985),
Harvey,
K.
Zirin, H.,
L..
Martin,
Ap. 3.. F.,
S. L. Keil) Bumba, V.,
S. F..
291(1985),
Proc.
Symp.
Solar
Phyr.,
Magnetic
Fields”,
241.
805. 541.
Topka, K. P., Tarbell, T. D., Title, A. M., Ap. .I., Shi, Z., Wang, J., Patterron. A., BBSO, 257.
[I 11 Martin, S. [12]
Zirin,
P. R.,
~~~~~~
32(1973),
306(1986),
304.
389.
858. on Small
Izv.Krym.Astr.0b.s.
Scale Dynamical 23
(1960)
Procerrer 212.
in Quiet Srcllrr
Atmoapbezec,
p. 30. (Ed.