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Magnetic field and flares of the large sunspot group of April–May 1978
Chin.Astron.Astrophys.
5 (1981)
298-306
Pergamon
Acta Astron.Sinica -22 (1981) 18-28
MAGNETIC
FIELD
Press. Printed in Great Britain 0146-6364/81/030298-09$07.50/O
AND FLARES OF THE LARGE SUNSPOT GROUP
OF APRIL-MAY 1978* ZHANG Heng, LI Bo-shu, Yunnan Observatory, Academia Sinica
Received
1980 May 19
ABSTRACT From..magnetograms of the active region 15266 obtained at Yunnan observatory we found that 1) an inverted field configuration and a twisted neutral line are both closely correlated with high-energy flare eruptions. After the flares, the field configuration and the neutral line revert to more stable states. 2) Most of the flares of the present region occurred away from the neutral line; those near the line occurred either in regions of high field gradient or in the vicinity of Severny’s “neutral points”
1.
OBSERVATIONS AND DATA
McMath Active disk
from
Region
April
filtergrams, the
coarse
patrol
15266
25 to
visual
drawings
magnetic
pictures.
field (In
Table
T (max)
1
CI,ASS
UT
4
25
0729
I-
4
26
0205
l-
0310
*A condensed
27
of
Number 78126)
was followed
sunspots,
[l],
Flares
D
1978,
50 were in
M
the
at
the
fine-detail
and magnetograms.
Ref.
M
4
(= Yunnan Serial
May 7,
photos
62 flares
reported,
Active
9 of
Regior,
which
passed
across
Yunnan Observatory
were which
Mcllath
in white observed have
15266
the
with
light, on the
been
Sun’s
Ho
pictures
found
not
to belong
(= Yunnan 78126)
T (max) ,,T CI,ASI --- T (max) CLASS D M C UT
T (max) E-
D
uT
CLASS l-
1005
l-
0110
2
0827
0505
l-
0127
l-
0930
1
1N
0647
l-
0240
1
1012
2
0517
1-
0656
1-F
0325
l-
0833
2N
2344
1
0347
1-
4
28
5
5
2342
1F
0013
1
1051
1N
0002
l-
0459
l-
1107
1-
0110
l-
0813
1
0052 0345
11F
0920
l-
0510
1-
0050
l-
0609
l-
1010
1-
4
29
0057
l-
0138
1
0315
1
0420
l-
0413
l-
0450
l-
0210
l-
0618
1
0557
l-
0651
l-
0715
1
0658
l-
0353
2
0826
1
0722
l-
0433
l-
0948
l-
0735
l-
0610
l-
0820
l-
0050
l-
1005
l-
1037
1-
translation
4
30
5
5
5
1
2
4
0642
2
0316
2
5
5
6
7
of
chromosphere
0135
1N
0430
1-
0500
1-
0412
1N
Flares
to
the
of
maximum and class
present
draw sunspot (April
active
These
Method
visual
of
sketches
dots
mark the
[l],
shown in
Figs.
construction
large
flare
borderedoneither
side
f 500 G, “+I’ for
have
5b,
lined
TABLE 1 lists
in
Ref.
[Z].
limbs
of
and parallels
neutral
line
of
Successive
time
material
magnetograms by the
using
the
their
and photographic
accompanied
than
by +500 G isogausses. for
added). visual
up Yocally”
rather
marks the
“-‘I
299
we had successful
lb-
and meridians
centres,
N-polarity,
been
sufficient but
were
line
1978
was described
sunspots
dashed
April
only
visual
on 5 days
drawings
The chromosphere the
centres
the
whole
of the
isogauss
of
latitudes
are field
contours
(Figs, photos,
flares
disk.
vertical
to
at
In Fig.
1-5,
shown.
In
HI1 =0,
are
at
intervals
S-polarity.
SPECIAL FEATURES OF THE MAGNETIC FIELD 1.
Inverted
When it (Fig. to
12 days,
of
the
2.
for
and magnetograms
the magnetograms,
of
We secured
are
their
maximum and centres small
and 21 others
numbers.
pictures
26-30).
la-5a).
region,
of
first lb)
Field
the
leader
expectations
region,
AS,
on the region
in the appeared
by some authors
Fig.la
of
limb,
cycle.
SW of
as judged
instability
Sunspots
active the
of
Apr 26,0657
S (note
increased
UI
28th
flare area
has a rather
configuration
3b),
field
then
the
another
If of
decreased
field
strong
CS) contrary S-polarity
have been
we regard
AS, and its between
structure.
On Apr 26
“hill”
configurations
production. and strength
complex
was inverted.
particularly
(Fig.
Such inverted
by the first
region
field
On the
CS.
as characteristic
then,
degree
the
This
east
was predominantly
present
to
[3,4]
as an instability, to AN, the
Configuration
appeared
the
such
a situation
position 26th
Fig. lb Magnetogram and Flares Apr 26, 0210 UT
regarded
relative and the
30th,
300
Flares of April 1978
Fig.2a Sunspots. Apr 27, 0705 UT
Fig.2b Magnetogram and flares. Apr 27, 1000 UT
Flares
Fig.3a
Fig.3b
Magnetogram
of
Sunspots.
and flares.
April
301
1978
Apr 28,
Apr 28,
0803 UT
0210
UT
Fig-fib Magnetogram
and flares. Apr 29,
0110
UT
303
Flare of April 1978
Fig.Sa Sunspots. Apr
30,
0835
UT
Fig.Sb Magnetogram and flares. Apr 30, 0250 UT
304
Flares of April 1978
reaching a maximum on the 28th. 2.
Changes in the Neutral Line
The part of the neutral line around CS showed rapid
changes between the 26th and the 28th. See Figs. lb, 2b, 3b.
On the 26th, it was fairly
straight, but by the 28th, it had become very twisted, enclosing both a 'peninsula" (CS) and a deep tlbayV1 (AN). A twisted neutral line, or one that makes a large angle with the meridian has been thought [S] to be closely correlated with high-energy flares. On the 29th, the pair AS and AN rotated clockwise relative to each other (see TABLE 2). As a result, Table 2
Apr 29
I
Heliographic Coordinates of AS and AN
18.0
78.70
I
I
18.5
I
81.28
both the peninsula and the bay became less pronounced. Another consequence is the production of another small hill AS opposite AN. See Fig. 6.
AN
The field gradient around AlS and AN was very high.
On the 30th,theneutral line seemed to have entered a more stable state. 2728313133353334383628252513 3Q31182J3230~3533333l27~Ol3
instabilities as evidenced by an
312434373535@7373327I_J!~#~
inverted field configuration and by a twisted
25283136293V33333~~~~12129
neutral line both reached a maximum on the 28th.
242630282628~~6~~232322 iV30
A,s
1817r3pf9isi5393~~ 'IFa -~~~~~23~324~?jlo1716192121 20 18?/~31oiJl9~92~~~~813/2/~ Fig.6 Field intensity matrix within the rectangle marked in Fig.4b. Each value refers to an area of 2'!2X 1'.'5. 3.
Summarizing, the magnetograms of Apr 26-30 show that
And we know that a Class 3B flare occurred on the
28th at UT1335and a Class 28 flare on the
29th at UT1815. Afterwards, on the 30th, both the field configuration and the neutral line were found to be in more stable states.
DISTRIBUTION OF FLARE BRIGHT POINTS
In this Section, our discussion will be confined to the 39 flares (comprising 63 bright knots) found in our chromosphere patrol over the 6 days Apr. 25 - 30. Of our chromosphere photograph, photosphere photograph and magnetogram, the first has the smallest scale corresponding to a solar diameter of 131 mm.
If we take 0.25 mm as the limit of precision
of an eye estimate, then we shall find for the various positions of ths active region during this time, this limit corresponds to 5000 km on the Sun surface, at worst. For the 63 bright knots, we measured their distances totheneutral line. We found only 18 to have distances less than 5000 km, while 37 to have distances greater than 10,000 km. We may now concentrate on the 18 bright knots nearest to the neutral line (these are marked by triangles in Figs. lb-5b) to see whether there are any peculiarities in the field around them, [6]. First, we note that 4 bright points on the 29th, marked as 0450 (2 points) 0557 and 0658 on Fig. 4b are located in the region of high gradient as noted above. On the 28th, the part oftheneutral line lies between AS and AN and closer to the latter. Fig. 3a shows their penumbral filaments are continuous in the vicinity of the neutral line. We
Flares
know that field
the
Hence
[7].
regions
we see
antiparallel
are
activities
in
were
UT, these
On the “neutral
close
to
the
B1 and B2 are exactly
that
and they
filaments
other
orientated
in
directions observed
hand,
neutral
line,
the
knots there
as defined
region
the
same direction
since
in
the
HI1 =0,
are to
above
present
the
plane
this
on the of
area
as the
S-polarity
and N-polarity
equation
two sides
of
the penumbral
on the
transverse
we have
Hence by Maxwell’s
densities
perpendicular in
305
1978
inductions then
antiparallel.
current
4 bright
points”
are
April
B1 and B2 are the magnetic
if
infinitely
and hence
0450
penumbral
of
28th,
the
neutral
filaments.
but
on the
29th
are
12 bright
knots [8].
in
the vicinity
See Fig.
7.
of
Whereas,
which
we could
it
quite
is
find
impossible
fl--.
26-'0517 UT
26’0833 UT
*,d
0826 0413
28& f6y6
“T
UT 29’0820 UT
3060240UT Fig.7
Flare Lines
after
appeared.
by Severny
30’0240 UT
knots (black dots) in the vicinity with arrows run orothogonal to the
30” “0;;; UT of neutral points(shaded isogauss contours.
line,
No flare
dots).
396
Flares of April 1978
to find such "neutral points" around the neutral line between AN and AlS in Fig. 4b, as the isogauss contours there are nearly parallel. As regards the two remaining cases [Apr. 27, 1005 and 30 0920) we do not have sufficient information on the local field. In summary, most of the flares of Region 15266 occurred away from the neutral line, and those near the line canbelargely put into 2 groups: one group occur in regions of high field gradient and antiparallel currents, the other in the vicinity of "neutral points". ACKNOWLEDGEMENT We thank ZHOU Yun-feng and LI Weibao for assistance and Ding You-ji and ZHANG Bai-rong for guidance in the course of this work.
REFERENCES [1] LI Wei-bao, LI Jing-ying, LI Qiu-sha, ZHANG Heng, Ken*e Tongbczo(1979) 840. [2] DING You-ji, PENG Fang-lin, ZHONG Shu-hua, LI Bo-shu, LUAN Ti, YE Hui-lian, Studia Astronomica Sinica No. 1 (1978) 69. English trans. in Chin. Astron. 3 (1979) 205. [3] YE Shi-hui "Magnetic Fields in Celestial Bodies" (in Chinese) pp 109.[4] ZHANG Bo-rong, ZHONG Shu-hua, WANG Hong-zhao, Studia Astronomica Sinica No. 2 (1978) 76. English trans. in Chin. Astron. 3 (1979) 400-408. [5] A. M. Ssepesa. A. B. Genepa& Nsa. Kp AG, 41-42 (1960). 97-156. [6] G. E.MoretonandA, B. Beverny, SolarPAysib,3(1968), 282-297. [7] F. B. K~KJI~H, B. E. Crenanoa. Conaesamesaaame,(1963) Ne 1,55. [8] A. B. Ceaep~wft, H3.9. Kp AO, 20 (1958). 22-50.
5 (1981)
298-306
Pergamon
Acta Astron.Sinica -22 (1981) 18-28
MAGNETIC
FIELD
Press. Printed in Great Britain 0146-6364/81/030298-09$07.50/O
AND FLARES OF THE LARGE SUNSPOT GROUP
OF APRIL-MAY 1978* ZHANG Heng, LI Bo-shu, Yunnan Observatory, Academia Sinica
Received
1980 May 19
ABSTRACT From..magnetograms of the active region 15266 obtained at Yunnan observatory we found that 1) an inverted field configuration and a twisted neutral line are both closely correlated with high-energy flare eruptions. After the flares, the field configuration and the neutral line revert to more stable states. 2) Most of the flares of the present region occurred away from the neutral line; those near the line occurred either in regions of high field gradient or in the vicinity of Severny’s “neutral points”
1.
OBSERVATIONS AND DATA
McMath Active disk
from
Region
April
filtergrams, the
coarse
patrol
15266
25 to
visual
drawings
magnetic
pictures.
field (In
Table
T (max)
1
CI,ASS
UT
4
25
0729
I-
4
26
0205
l-
0310
*A condensed
27
of
Number 78126)
was followed
sunspots,
[l],
Flares
D
1978,
50 were in
M
the
at
the
fine-detail
and magnetograms.
Ref.
M
4
(= Yunnan Serial
May 7,
photos
62 flares
reported,
Active
9 of
Regior,
which
passed
across
Yunnan Observatory
were which
Mcllath
in white observed have
15266
the
with
light, on the
been
Sun’s
Ho
pictures
found
not
to belong
(= Yunnan 78126)
T (max) ,,T CI,ASI --- T (max) CLASS D M C UT
T (max) E-
D
uT
CLASS l-
1005
l-
0110
2
0827
0505
l-
0127
l-
0930
1
1N
0647
l-
0240
1
1012
2
0517
1-
0656
1-F
0325
l-
0833
2N
2344
1
0347
1-
4
28
5
5
2342
1F
0013
1
1051
1N
0002
l-
0459
l-
1107
1-
0110
l-
0813
1
0052 0345
11F
0920
l-
0510
1-
0050
l-
0609
l-
1010
1-
4
29
0057
l-
0138
1
0315
1
0420
l-
0413
l-
0450
l-
0210
l-
0618
1
0557
l-
0651
l-
0715
1
0658
l-
0353
2
0826
1
0722
l-
0433
l-
0948
l-
0735
l-
0610
l-
0820
l-
0050
l-
1005
l-
1037
1-
translation
4
30
5
5
5
1
2
4
0642
2
0316
2
5
5
6
7
of
chromosphere
0135
1N
0430
1-
0500
1-
0412
1N
Flares
to
the
of
maximum and class
present
draw sunspot (April
active
These
Method
visual
of
sketches
dots
mark the
[l],
shown in
Figs.
construction
large
flare
borderedoneither
side
f 500 G, “+I’ for
have
5b,
lined
TABLE 1 lists
in
Ref.
[Z].
limbs
of
and parallels
neutral
line
of
Successive
time
material
magnetograms by the
using
the
their
and photographic
accompanied
than
by +500 G isogausses. for
added). visual
up Yocally”
rather
marks the
“-‘I
299
we had successful
lb-
and meridians
centres,
N-polarity,
been
sufficient but
were
line
1978
was described
sunspots
dashed
April
only
visual
on 5 days
drawings
The chromosphere the
centres
the
whole
of the
isogauss
of
latitudes
are field
contours
(Figs, photos,
flares
disk.
vertical
to
at
In Fig.
1-5,
shown.
In
HI1 =0,
are
at
intervals
S-polarity.
SPECIAL FEATURES OF THE MAGNETIC FIELD 1.
Inverted
When it (Fig. to
12 days,
of
the
2.
for
and magnetograms
the magnetograms,
of
We secured
are
their
maximum and centres small
and 21 others
numbers.
pictures
26-30).
la-5a).
region,
of
first lb)
Field
the
leader
expectations
region,
AS,
on the region
in the appeared
by some authors
Fig.la
of
limb,
cycle.
SW of
as judged
instability
Sunspots
active the
of
Apr 26,0657
S (note
increased
UI
28th
flare area
has a rather
configuration
3b),
field
then
the
another
If of
decreased
field
strong
CS) contrary S-polarity
have been
we regard
AS, and its between
structure.
On Apr 26
“hill”
configurations
production. and strength
complex
was inverted.
particularly
(Fig.
Such inverted
by the first
region
field
On the
CS.
as characteristic
then,
degree
the
This
east
was predominantly
present
to
[3,4]
as an instability, to AN, the
Configuration
appeared
the
such
a situation
position 26th
Fig. lb Magnetogram and Flares Apr 26, 0210 UT
regarded
relative and the
30th,
300
Flares of April 1978
Fig.2a Sunspots. Apr 27, 0705 UT
Fig.2b Magnetogram and flares. Apr 27, 1000 UT
Flares
Fig.3a
Fig.3b
Magnetogram
of
Sunspots.
and flares.
April
301
1978
Apr 28,
Apr 28,
0803 UT
0210
UT
Fig-fib Magnetogram
and flares. Apr 29,
0110
UT
303
Flare of April 1978
Fig.Sa Sunspots. Apr
30,
0835
UT
Fig.Sb Magnetogram and flares. Apr 30, 0250 UT
304
Flares of April 1978
reaching a maximum on the 28th. 2.
Changes in the Neutral Line
The part of the neutral line around CS showed rapid
changes between the 26th and the 28th. See Figs. lb, 2b, 3b.
On the 26th, it was fairly
straight, but by the 28th, it had become very twisted, enclosing both a 'peninsula" (CS) and a deep tlbayV1 (AN). A twisted neutral line, or one that makes a large angle with the meridian has been thought [S] to be closely correlated with high-energy flares. On the 29th, the pair AS and AN rotated clockwise relative to each other (see TABLE 2). As a result, Table 2
Apr 29
I
Heliographic Coordinates of AS and AN
18.0
78.70
I
I
18.5
I
81.28
both the peninsula and the bay became less pronounced. Another consequence is the production of another small hill AS opposite AN. See Fig. 6.
AN
The field gradient around AlS and AN was very high.
On the 30th,theneutral line seemed to have entered a more stable state. 2728313133353334383628252513 3Q31182J3230~3533333l27~Ol3
instabilities as evidenced by an
312434373535@7373327I_J!~#~
inverted field configuration and by a twisted
25283136293V33333~~~~12129
neutral line both reached a maximum on the 28th.
242630282628~~6~~232322 iV30
A,s
1817r3pf9isi5393~~ 'IFa -~~~~~23~324~?jlo1716192121 20 18?/~31oiJl9~92~~~~813/2/~ Fig.6 Field intensity matrix within the rectangle marked in Fig.4b. Each value refers to an area of 2'!2X 1'.'5. 3.
Summarizing, the magnetograms of Apr 26-30 show that
And we know that a Class 3B flare occurred on the
28th at UT1335and a Class 28 flare on the
29th at UT1815. Afterwards, on the 30th, both the field configuration and the neutral line were found to be in more stable states.
DISTRIBUTION OF FLARE BRIGHT POINTS
In this Section, our discussion will be confined to the 39 flares (comprising 63 bright knots) found in our chromosphere patrol over the 6 days Apr. 25 - 30. Of our chromosphere photograph, photosphere photograph and magnetogram, the first has the smallest scale corresponding to a solar diameter of 131 mm.
If we take 0.25 mm as the limit of precision
of an eye estimate, then we shall find for the various positions of ths active region during this time, this limit corresponds to 5000 km on the Sun surface, at worst. For the 63 bright knots, we measured their distances totheneutral line. We found only 18 to have distances less than 5000 km, while 37 to have distances greater than 10,000 km. We may now concentrate on the 18 bright knots nearest to the neutral line (these are marked by triangles in Figs. lb-5b) to see whether there are any peculiarities in the field around them, [6]. First, we note that 4 bright points on the 29th, marked as 0450 (2 points) 0557 and 0658 on Fig. 4b are located in the region of high gradient as noted above. On the 28th, the part oftheneutral line lies between AS and AN and closer to the latter. Fig. 3a shows their penumbral filaments are continuous in the vicinity of the neutral line. We
Flares
know that field
the
Hence
[7].
regions
we see
antiparallel
are
activities
in
were
UT, these
On the “neutral
close
to
the
B1 and B2 are exactly
that
and they
filaments
other
orientated
in
directions observed
hand,
neutral
line,
the
knots there
as defined
region
the
same direction
since
in
the
HI1 =0,
are to
above
present
the
plane
this
on the of
area
as the
S-polarity
and N-polarity
equation
two sides
of
the penumbral
on the
transverse
we have
Hence by Maxwell’s
densities
perpendicular in
305
1978
inductions then
antiparallel.
current
4 bright
points”
are
April
B1 and B2 are the magnetic
if
infinitely
and hence
0450
penumbral
of
28th,
the
neutral
filaments.
but
on the
29th
are
12 bright
knots [8].
in
the vicinity
See Fig.
7.
of
Whereas,
which
we could
it
quite
is
find
impossible
fl--.
26-'0517 UT
26’0833 UT
*,d
0826 0413
28& f6y6
“T
UT 29’0820 UT
3060240UT Fig.7
Flare Lines
after
appeared.
by Severny
30’0240 UT
knots (black dots) in the vicinity with arrows run orothogonal to the
30” “0;;; UT of neutral points(shaded isogauss contours.
line,
No flare
dots).
396
Flares of April 1978
to find such "neutral points" around the neutral line between AN and AlS in Fig. 4b, as the isogauss contours there are nearly parallel. As regards the two remaining cases [Apr. 27, 1005 and 30 0920) we do not have sufficient information on the local field. In summary, most of the flares of Region 15266 occurred away from the neutral line, and those near the line canbelargely put into 2 groups: one group occur in regions of high field gradient and antiparallel currents, the other in the vicinity of "neutral points". ACKNOWLEDGEMENT We thank ZHOU Yun-feng and LI Weibao for assistance and Ding You-ji and ZHANG Bai-rong for guidance in the course of this work.
REFERENCES [1] LI Wei-bao, LI Jing-ying, LI Qiu-sha, ZHANG Heng, Ken*e Tongbczo(1979) 840. [2] DING You-ji, PENG Fang-lin, ZHONG Shu-hua, LI Bo-shu, LUAN Ti, YE Hui-lian, Studia Astronomica Sinica No. 1 (1978) 69. English trans. in Chin. Astron. 3 (1979) 205. [3] YE Shi-hui "Magnetic Fields in Celestial Bodies" (in Chinese) pp 109.[4] ZHANG Bo-rong, ZHONG Shu-hua, WANG Hong-zhao, Studia Astronomica Sinica No. 2 (1978) 76. English trans. in Chin. Astron. 3 (1979) 400-408. [5] A. M. Ssepesa. A. B. Genepa& Nsa. Kp AG, 41-42 (1960). 97-156. [6] G. E.MoretonandA, B. Beverny, SolarPAysib,3(1968), 282-297. [7] F. B. K~KJI~H, B. E. Crenanoa. Conaesamesaaame,(1963) Ne 1,55. [8] A. B. Ceaep~wft, H3.9. Kp AO, 20 (1958). 22-50.