Dear Members of the IAU Inter-Division B and E Working Group on Coordination of Synoptic Observations of the Sun:

Attached is a brief summary of recent activity of this working group since the last update:

1. Activity related to preservation and digitization of records of past solar activity.

  • The WG was contacted by researchers from the Taipei Astronomical Museum (TAM), who run an observing program of daily sunspot drawings since 1941. The TAM drawings were digitized and are now available via the Historical Archive of Sunspot Observations (HASO) at http://haso.unex.es/?q=content/sunspot-drawings Thank you to our colleagues from TAM and HASO who made it happen.
  • We received several requests for letters of support for WG members for their activity on digitization of solar observations from historical archives: Zurich Library, ISSI, and Paris Observatory. Several members of WG worked together on issues related to getting access to historical data and/or finding funding for digitization of data.
  • We also provided letters of support for continuing operations of Debrecen Heliophysical Observatory (DHO), and for a research proposal that seeks funding for implementing advanced statistical methods to improve the sunspot number as recomputed from the SILSO database. Unfortunately, we have recently learned that the DHO has been effectively closed (see http://fenyi.solarobs.unideb.hu/news.html).
  • Early this year, we learned about an effort to digitize synoptic maps created by Patrick McIntosh, and had attended the team meeting for this project. The project is led by David Webb (see current information at http://www.ngdc.noaa.gov/docucomp/page?xml=NOAA/NESDIS/NGDC/STP/Solar/iso/xml/solar-imagery_composites_synoptic-maps_mc-intosh.xml&view=getDataView&header=none).

2. Sunspot number time series.

Several members of the WG participate in grass-root community initiative to recalibrate the historical time series of sunspot number and create a single unified time series (with error bars). During the Space Climate 6 symposium in Levi (Finland, April 2016), we held a side meeting to discuss plans for this recalibration. During the SPD meeting in Boulder, we organized a small side meeting to make further plans. An action plan was developed as the result of these meetings and is now in the final discussions. A group of researchers who expressed interests in pursuing verification and reconciliation of different time series was identified, and smaller groups were formed. These groups will examine existing time series for specific issues, and in a second step, all groups will meet to discuss the solutions for found differences between different time series. This will take place in the framework of ISSI workshops.

As a long-term goal, we plan proposing a unified sunspot number time series as a “reference” series for IAU approval. External (non-solar) communities had expressed a strong desire for having a single sunspot number time series (not the multiple ones). The concept of “reference” data sets is used by other communities (e.g., Earth magnetic field, solar irradiance); and as part of developing sunspot number “reference” time series, we will rely on their experience and develop clear procedures for updating, vetting and officially approving the reference time series.

3. Web site, data.

The work on the WG web site was somewhat slow. We created a map of solar observatories, and some of you had provided valuable comments on improving this map. We are still working on implementing these comments. We also continue collecting links to various solar data although it is clear that the presentation of this data needs to be improved. The web site still uses “long list” format, which is getting too long to be useful. If you have any suggestions on a better approach for presenting the data, please let us know.

In the course of our personal research, we came across of several long-term datasets that were very useful in the past, but unfortunately, are not updated anymore. Examples of such datasets include summary information on prominences at the limb and their eruptions, maps of coronal holes, synoptic/Carrington maps of EUV/coronal intensity. Some of the datasets were only produced during some limited period of time, and there is no consistency. Therefore, if the idea is supported by the solar physics community, this working group could create/discuss a list of such data products derived from primary data that would be beneficial for researchers. Getting funding for production of such long-duration datasets is always an issue; one possible solution could be to maintain and extend such data sets as collaboration between several organizations, which would share the costs.

4. Planned activities for the coming year

  • Support to threatened continuation of the WDC-SILSO activities at the Royal Observatory of Belgium, in Brussels and other long-term projects, which continuation could be threatened.
  • Participation to meetings: Synoptic ground-based solar observations for Space Weather, Nice, 19-20/10/2016
  • Continue work towards developing unified sunspot number time series.

If you have any information that would be of interest to the members of this IAU Working Group, please let us know.

Alexei A. Pevtsov and Frederic Clette