J/A+A/584/A73 Sunspot areas and tilt angles (Senthamizh Pavai+, 2015)
Sunspot areas and tilt angles for solar cycles 7-10.
Senthamizh Pavai V., Arlt R., Dasi-Espuig M., Krivova N., Solanki S.
<Astron. Astrophys. 584, A73 (2015)>
=2015A&A...584A..73S 2015A&A...584A..73S (SIMBAD/NED BibCode)
ADC_Keywords: Sun
Keywords: sun: sunspots - sun: activity - catalogs
Abstract:
Extending the knowledge about the properties of solar cycles into the
past is essential for understanding the solar dynamo. This paper aims
to estimate areas of sunspots observed by Schwabe in 1825-1867 and
to calculate the tilt angles of sunspot groups.
The sunspot sizes in Schwabe's drawings are not to scale and need to
be converted into physical sunspot areas. We employed a statistical
approach assuming that the area distribution of sunspots was the same
in the 19th century as it was in the 20th century.
Description:
We present sunspot positions and areas from historical observations of
sunspots by Samuel Heinrich Schwabe from Dessau, Germany. He has
recorded his observations of sunspots from 1825-1867 as drawings in
small circles of about 5cm diameter (representing the solar disk).
Even though he has used quite a number of telescopes for his
observations, the majority of the full-disk drawings were made with a
3-1/2-foot telescope from Fraunhofer. His observing log books are
stored in the library of the Royal Astronomical Society in London.
Those drawings were digitized photographically with a resolution of
2912x4378 pixels per page. The sizes and positions of the sunspots
were measured using a dozen of circular mouse cursor shapes with
different diameters. The sunspot sizes in Schwabe's drawings are not
to scale and need to be converted into physical sunspot areas. We
employed a statistical approach assuming that the area distribution of
sunspots was the same in the 19th century as it was in the 20th
century. Umbral areas for about 130,000 sunspots observed by Schwabe
were obtained, as well as the tilt angles of sunspot groups assuming
them to be bipolar (two or more spots). There is, of course, no
polarity information in the observations.
Both an updated sunspot database and a tilt angle database are
available at http://www.aip.de/Members/rarlt/ sunspots for further
study.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 106 135921 Sunspot positions and areas
table4.dat 108 23141 Tilt angles of the sunspot groups with two or
more spots
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See also:
VI/138 : Sunspots catalogues, 1853-1870 (Casas+, 2013)
J/A+A/390/707 : Hemispheric Sunspot Numbers 1975-2000 (Temmer+, 2002)
J/A+A/447/735 : Hemispheric Sunspot Numbers 1945-2004 (Temmer+, 2006)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 I4 yr Obs.Y Observation date (YYY)
6- 7 I2 "month" Obs.M Observation date (MM)
9- 10 I2 d Obs.D Observation date, day referring to the German
civil calendar running from midnight to
midnight (DD)
12- 13 I2 h Obs.h Observation time in mean local time
in Dessau, Germany (HH)
15- 16 I2 min Obs.m Observation time, typically accurate
to 15 minutes (MI)
18 I1 --- T [0/1] Indicates how accurate the time is (1)
20- 24 F5.1 deg HLON0 Heliographic longitude of apparent disk centre
seen from Dessau (L0)
26- 30 F5.1 deg HLAT0 Heliographic latitude of apparent disk centre
seen from Dessau (B0)
32- 36 F5.1 deg CMD ? Central meridian distance, difference in
longitude from disk centre
37 A1 --- n_CMD [n-] Note for no data (2)
38- 42 F5.1 deg HLON ? Heliographic longitude in the Carrington
rotation frame (LLL.L)
43 A1 --- n_HLON [n-] Note for no data (2)
44- 48 F5.1 deg HLAT ? Heliographic latitude,
southern latitudes are negative (BBB.B)
49 A1 --- n_HLAT [n-] Note for no data (2)
51 A1 --- M [CHQ-01] Method of determining the
orientation (3)
53 I1 --- Q [0/4] Subjective quality (4)
55- 56 I2 --- SS Size estimate in 12 classes running from 1 to
12; a spotless day is indicated with 0
58- 65 A8 --- Group Group designation based on Schwabe,
but modified by our regrouping
67- 76 A10 --- Measurer Last name of person who obtained position
78- 82 F5.1 deg HLONM ?=- Model longitude from rotational matching
(only spots used for matching have this)
(MOD_L)
84- 88 F5.1 deg HLATM ?=- Model latitude from rotational matching
(only spots used for matching have this)
(MOD_B)
90- 94 F5.3 deg Sigma ?=- Total residual of model positions compared
with measurements of reference spots in
rotational matching (only spots used for the
matching have this), holds for entire day
96- 99 F4.1 deg delta ? Heliocentric angle between the spot and the
apparent disk centre in degrees
(disk-centre distance)
100 A1 --- n_delta [n-] Note for no data (2)
101-104 I4 --- Umb ? Inferred umbral area in millionths of the
solar hemisphere (MSH)
105 A1 --- n_Umb [n] Note for no data (5)
106 A1 --- A [!U-] Flag for area mapping (6)
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Note (1): Timeflag as follows:
0 = time has been inferred by the measurer (in most cases to be 12h local time)
1 = the time is as given by the observer
Note (2): Code for no data as follows:
- = indicates spotless day
n = position of spot could not be measured
Note (3): Method of determining the orientation as follows:
C = horizontal pencil line parallel to celestial equator
H = book aligned with azimuth-elevation
Q = rotational matching with other drawings (spot used for the matching have
MHLON, HLAT and sigma {diff} "-")
Note (4): Subjective quality as follows:
1 = all observations with coordinate system drawn by Schwabe
2 = Positions derived from rotational matching with the probability
distributions fixing the position angle of the drawing were not very sharp
3 = Positions derived from rotational matching with the probability
distributions fixing the position angle of the drawing were broad and
asymmetric
0 = spotless day
4 = spots for which no position could be derived, but have sizes
Note (5): Note for umbral no data:
Umb=0 for spotless days
n_Umb=n if spot position could not be derived or Delta>85deg
Note (6): Flag as follows:
U = area mapping is based on umbral area
! = area mapping is based on penumbral area (less certain than from umbral)
(actual area given in Umb is always umbral)
- = spotless day
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 yr Obs.Y Observation date (YYY)
6- 7 I2 "month" Obs.M Observation date (MM)
9- 10 I2 d Obs.D Observation date, day referring to the German
civil calendar running from midnight to
midnight (DD)
12- 13 I2 h Obs.h Observation time in mean local time
in Dessau, Germany (HH)
15- 16 I2 min Obs.m Observation time, typically accurate
to 15 minutes (MI)
18- 25 A8 --- Group Group name based on Schwabe, but modified
by our regrouping
27- 28 I2 --- SP Number of spots in a group
30- 32 I3 --- ARA Sum of umbral area of all spots in a group,
in millionths of the solar hemisphere (MSH)
34- 38 F5.1 deg HLONA Area-weighted heliographic longitude of the
group (AWL.L)
40- 44 F5.1 deg HLATA Area-weighted heliographic latitude of the
group (AWB.B)
46- 51 F6.2 deg TiltAn Tilt angle of the group (1)
53- 58 F6.2 deg TiltHo Tilt angle computed as in Howard (1991,
Sol. Phys., 136, 251) for compatibility
reasons (2)
60- 64 F5.2 deg PolSP Polarity separation of the group in degrees on
the solar sphere (3)
66- 67 I2 --- FN Number of spots in the following polarity
69- 70 I2 --- LN Number of spots in the leading polarity
72- 74 I3 --- FAR Umbral area of the following polarity, in MSH
76- 78 I3 --- LAR Umbral area of the leading polarity, in MSH
80- 84 F5.1 deg HLONF Area-weighted longitude of the following
polarity (FLL.L) (3)
86- 90 F5.1 deg HLATF Area-weighted latitude of the following
polarity (FBB.B) (3)
92- 96 F5.1 deg HLONL Area-weighted longitude of the leading
polarity (LLL.L) (3)
98-102 F5.1 deg HLATL Area-weighted latitude of the leading
polarity (BBB.B) (3)
104-108 F5.1 deg GFC Heliocentric distance of the group from the
disk centre in degrees
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Note (1): Tilt angle of the group ; positive sign means leading polarity closer
to equator in either hemisphere. This tilt angle was found using an isotropic
search for the most likely dividing line between the polarities.
Note (2): It is based on a fixed vertical dividing line between the polarities
and an approximative formula for the tilt angle.
Note (3): based on the polarity definition for TiltAn.
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Acknowledgements:
V. Senthamizh Pavai, svalliappan(at)aip.de
Rainer Arlt, rarlt(at)aip.de
Leibniz Institute for Astrophysics Potsdam, Germany
(End) Rainer Arlt [Leibniz Inst.], Patricia Vannier [CDS] 04-Nov-2015