Wilcox Solar Observatory Magnetograms

(index below)

As part of its regular observing program, WSO regularly produces solar magnetograms. Magnetograms are maps of the line-of-sight component of magnetic flux at the photosphere, the sun's visible surface. The fields are measured by detecting the Zeeman shift between right-hand and left-hand circularly polarized light in a suitable magnetically sensitive absorption line. The line used is the 5250Å absorption line of neutral iron (Fe I). The observations are made by scanning slowly back and forth across the solar disc, stopping for 15 seconds at each of 195 preselected locations to measure the integrated flux in a square aperture of projected width 3' (about 10% of the solar diameter). The aperture is oriented parallel to the direction of the sun's rotational axis. In addition to determining the magnetic flux, measurements are also obtained of the line-of-sight component of surface motion from the line's Doppler shift, and of the intensity.

Weather permitting, magnetograms are usually obtained once per day. The only exception is that during summers when long days permit helioseismic observations of global modes of oscillation, magnetograms are made only once every three or four days. An average of about 250 magnetograms are made per year.

At left is a typical magnetogram: (actually it is our first one). In the image, regions of strong positive and negative magnetic flux are shown as bright blue and red areas, respectively. At this resolution and sensitivity, the global-scale organization of magnetic fields into large sectors of opposite polarity is evident. It is at the boundaries between these sectors that magnetic active regions develop.

The Dopplergrams (right) use the color convention positive-red negative-blue they are not particularly interesting to look at, except for quality checks, because they are completely dominated by the essentially constant solar rotation of about 2000 m/sec. They do contain useful information on subtle variations in the structure and rate of rotation, however.

The photograms of light intensity are purely diagnostic. Intensity Image Dark regions are caused not by spots at this resolution, but by temporary shadows of clouds, structures, or the horizon, and indicate degraded quality of the measurements. (left)

The ``daily'' magnetograms are numbered sequentially. Because of the large number of them, they have been doubly indexed in an image atlas. Clicking on the appropriate list below will bring up a page of 100 numbered small magnetogram images in the sequence-number range selected. Clicking on an individual image in that page will bring up a page displaying a large magnetogram, the corresponding Dopplergram and photogram, and information on the particular scan (time, sky condition, and quality assessment).


SN, Date SN, Date SN, Date
1 - 99, 1976/05/16 - 1976/09/05 100 - 199, 1976/09/06 - 1977/01/14 200 - 299, 1977/01/15 - 1977/05/19
300 - 399, 1977/05/20 - 1977/08/28 400 - 599, 1977/08/28 - 1978/05/24
600 - 699, 1978/05/25 - 1978/09/12 700 - 899, 1978/09/12 - 1979/05/26
900 - 999, 1979/05/26 - 1979/08/12 1000 - 1499, 1979/08/12 - 1981/04/29
1500 - 1599, 1981/04/30 - 1981/09/10 1600 - 2599, 1981/09/11 - 1985/06/12
2600 - 2699, 1985/06/12 - 1985/08/15 2700 - 2899, 1985/08/15 - 1986/04/09
2900 - 2999, 1986/04/09 - 1986/09/07 3000 - 3199, 1986/09/08 - 1987/05/11
3200 - 3299, 1987/05/13 - 1987/10/01 3300 - 3399, 1987/10/02 - 1988/03/01
3400 - 3499, 1988/03/02 - 1988/07/27 3500 - 3599, 1988/07/31 - 1989/01/27 3600 - 3699, 1989/01/28 - 1989/06/20
3700 - 3799, 1989/06/20 - 1989/09/26 3800 - 3899, 1989/09/26 - 1990/03/14 3900 - 3999, 1990/03/18 - 1990/08/30
4000 - 4099, 1990/08/31 - 1991/02/11 4100 - 4199, 1991/02/13 - 1991/08.13 4200 - 4299, 1991/08/13 - 1991/12/11
4300 - 4399, 1991/12/12 - 1992/06/25 4400 - 4499, 1992/07/02 - 1993/01/22 4500 - 4599, 1993/01/23 - 1993/07/20
4600 - 4699, 1993/07/21 - 1993/11/07 4700 - 4799, 1993/11/08 - 1994/04/23 4800 - 4899, 1994/04/24 - 1994/09/22
4900 - 4999, 1994/09/22 - 1995/03/06 5000 - 5099, 1995/03/06 - 1995/08/26 5100 - 5199, 1995/08/26 - 1995/11/15
5200 - 5299, 1995/11/16 - 1996/05/30 5300 - 5399, 1996/05/31 - 1996/09/10 5400 - 5499, 1996/09/11 - 1997/02/23
5500 - 5599, 1997/02/24 - 1997/05/18 5600 - 5699, 1997/05/18 - 1997/07/25 5700 - 5799, 1997/07/25 - 1997/09/30
5800 - 5899, 1997/10/02 - 1998/04/12 5900 - 5999, 1998/04/15 - 1998/07/15 6000 - 6099, 1998/07/16 - 1998/09/13
6100 - 6199, 1998/09/14 - 1999/02/02 6200 - 6299, 1999/02/03 - 1999/05/28 6300 - 6399, 1998/05/30 - 1999/07/27
6400 - 6499, 1999/07/27 6500 - 6599, 1999/10/08 6600 - 6699, 2000/03/08
6700 - 6799, 2000/06/03 6800 - 6899, 2000/08/24 6900 - 6999, 2001/02/28
7000 - 7099, 2001/06/06 7100 - 7199, 2001/08/28 7200 - 7299, 2002/01/03
7300 - 7399, 2002/05/10 7400 - 7499, 2002/07/22 7500 - 7599, 2002/10/31
7600 - 7699, 2003/04/16 7700 - 7799, 2003/07/10 7800 - 7899, 2003/09/19
7900 - 7999, 2004/03/13 8000 - 8099, 2004:07:03 8100 - 8199, 2004:09:16
8200 - 8299, 2005:01:23 8300 - 8399, 2005:06:13 8400 - 8499, 2005:08:17
8500 - 8599, 2005:11:27 8600 - 8699, 2006:05:15 8700 - 8799, 2006:08:16
8800 - 8899, 2006:12:22 8900 - 8999, 2007:05:01 9000 - 9099, 2007:07:30
9100 - 9199, 2007:11:26 9200 - 9299, 2008:04:17 9300 - 9399, 2008:07:14
9400 - 9499, 2008:08:25 9500 - 9599, 2008:12:30 9600 - 9699, 2009:04:19
9700 - 9799, 2009:06:24 9800 - 9899, 2009:08:10 9900 - 9999, 2009:10:23
10000, 2010:03:23 10100, 2010:06:16 10200, 2010:08:08
10300, 2010:10:12 10400, 2011:04:15 10500, 2011:07:09
10600, 2011:09:05 10700, 2011:12:28 10800, 2012:05:05
10900, 2012.07.02 11000, 2012.08.28 11100, 2012.11.10
11200, 2013.02.24 11300, 2013.05.10 11400, 2013.07.24
11500, 2013.09.23 11600, 2013.12.11 11700, 2014.04.09
11800, 2014.06.12 11900, 2014.08.09 12000, 2014.10.28
12100, 2015.04.01 12200, 2015.06.23 12300, 2015.08.31
12400 12500 12600


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