DOI: 10.7910/dvn/fmy6ur
title: Active region dipole moments determined from NSO carrington maps

description: &lt;h2&gt;Citation and Acknowledgements&lt;/h2&gt;

&lt;p&gt;&lt;br&gt;Please cite both this database the paper describing it, as well as adding the following acknowledgement:

&lt;p&gt;&lt;br&gt;&lt;b&gt;"Active region dipole moments determined from NSO synoptic carrington maps were downloaded from the solar dynamo dataverse (https://dataverse.harvard.edu/dataverse/solardynamo), maintained by Andrés Muñoz-Jaramillo." &lt;/b&gt;&lt;/p&gt;

&lt;p&gt;&lt;br&gt; Database citation format is shown at the top of this page, underneath the database title. It can be downloaded in a variety of formats directly from this page&lt;/p&gt;

&lt;p&gt;&lt;br&gt;The paper describing this database is&lt;/p&gt;

&lt;p&gt;&lt;br&gt;&lt;b&gt;T. Whitbread, A.R. Yeates and A. Muñoz-Jaramillo, How many active regions are necessary to predict to solar dipole moment?, The Astrophysical Journal 863, 116, (2018).&lt;/b&gt; &lt;a href="https://ui.adsabs.harvard.edu/abs/2018ApJ...863..116W/abstract"&gt;https://ui.adsabs.harvard.edu/abs/2018ApJ...863..116W/abstract&lt;/a&gt;&lt;br&gt;
&lt;/p&gt;

&lt;h2&gt;Description&lt;/h2&gt;

&lt;p&gt;Database of magnetic active region properties extracted from NSO synoptic carrington maps of the Sun's photospheric line-of-sight magnetic flux between carrington rotations CR 1641 and CR 2196 inclusive. Regions need not be bipolar, but rather can have complex, multipolar structures. The data were first used in &lt;a href="https://ui.adsabs.harvard.edu/abs/2018ApJ...863..116W/abstract"&gt;Whitbread et al. (2018)&lt;/a&gt;.&lt;/p&gt;

&lt;p&gt;The plot below summarizes the dataset, showing latitude versus time, coloured by axial dipole moment (saturated at 25% of maximum):&lt;/p&gt;

&lt;img src="http://www.maths.dur.ac.uk/~bmjg46/images/c21c22c23c24_axdip.png" alt="NSO active regions" width="840"&gt;

&lt;p&gt;Separate files are provided for each solar cycle, defined purely by date. The start dates used for each cycle are 1976-May-1, 1986-Mar-10, 1996-June-1 and 2008-Aug-03.&lt;/p&gt;

&lt;p&gt;In each file, the columns are as follows:&lt;/p&gt;

&lt;ol&gt;
&lt;li&gt;Carrington rotation number.&lt;/li&gt;
&lt;li&gt;Carrington longitude of region centre [degrees].&lt;/li&gt;
&lt;li&gt;Latitude of region centre [degrees].&lt;/li&gt;
&lt;li&gt;Total magnetic flux of each polarity [Maxwells].&lt;/li&gt;
&lt;li&gt;Axial dipole moment at time of observation [Gauss].&lt;/li&gt;
&lt;/ol&gt;

&lt;p&gt;&lt;i&gt;Important: &lt;/i&gt;The latitude and longitude denote the centroid of unsigned magnetic flux. Regions are not assumed to be bipolar, so tilt angle does not make sense as a measure. The more meaningful physical measure is axial dipole moment.&lt;/p&gt;

&lt;p&gt;The original carrington maps were downloaded from the NSO website: &lt;a href="http://solis.nso.edu/0/vsm/vsm_maps.php"&gt;http://solis.nso.edu/0/vsm/vsm_maps.php&lt;/a&gt;.&lt;/p&gt;

&lt;p&gt;Before cr2007, data from the KPVT (868.8nm line) were used, and from cr2007 onwards we used data from SOLIS/VSM (630.2nm, line-of-sight magnetic flux, 360x180 resolution).&lt;/p&gt;

&lt;p&gt;The active regions and their properties were identified from the sequence of carrington maps using an automated procedure, as in the sft_data code (available at &lt;a href="https://github.com/antyeates1983/sft_data"&gt;https://github.com/antyeates1983/sft_data&lt;/a&gt;). In this code, each region is defined as a connected area of strong magnetic flux, and is corrected for flux imbalance. Here we used the parameters sigma=3 and Bpar=39.8G.&lt;/p&gt;

&lt;p&gt;The properties given in this dataset were calculated at the time of observation of the region, before any further evolution.&lt;/p&gt;

&lt;h2&gt;Main Limitations&lt;/h2&gt;

&lt;p&gt;&lt;br&gt;The main limitations of these data are:&lt;/p&gt;

&lt;ol&gt;
&lt;li&gt;Sometimes, nearby active regions are classified as a single region by the automated method, and hence assigned an overall flux and dipole moment.&lt;/li&gt;
&lt;li&gt;Some regions are strong enough to be detected more than once in consecutive carrington rotations. In such cases, there is a separate entry in the database for each carrington rotation (i.e. there is no tracking of regions over time).&lt;/li&gt;
&lt;li&gt;Observational gaps in the original NSO synoptic maps mean that some regions are likely missing.&lt;/li&gt;
&lt;/ol&gt;