Sunspot Number Workshop - Newsletter 1Edit

SIDC, Royal Observatory of Belgium, Brussels, 21 - 25 May 2012

Dear Colleagues,

Below you will find an update of the schedule. In order to balance the contents of all 4 days, a few presentations were moved to other times.

We also include additional information, in particular directions to the ROB from the two hotels.

Last reminder: those who did not fill out the Doodle list for registering to the social activities and to the lunches should do it today at the latest! Thank you.

Sincerely yours, Frédéric, Ed & Leif

Workshop scheduleEdit

Please take note of the time allocated to your talk. It includes a few minutes for questions.

You should provide us your presentation file before the start of the corresponding session (USB key), so we can install it on our projection PC. Alternately, you can also connect directly your own laptop.


13:00 - 14:00: Registration

13:00 - 14:00: lunch (possible at the ROB cafetaria)

14:00 - 14:15: Welcoming remarks: Frédéric Clette & Ronald Van der Linden (ROB Director)

14:15 - 14:30: Motivations and goals: Ed Cliver

Introduction to the SSN (Chair E. Cliver)

14:30 – 15:10: T. Friedli: Rudolf Wolf and the Zürich Sunspot Number

15:10 - 15:50: F. Clette: The international Sunspot Index: method and relation with recent indices

15:50 - 16:00: break

16:00 - 16:30: L.Svalgaard (K. Schatten): The Group Sunspot Number

16:30 - 16:45: Discussion: questions and clarifications regarding the methods at the base of the SSN.

16:45 – 18:00: Welcome Reception at the ROB


Introduction to the SSN (Chair F. Clette)

08:30 – 09:05: M. Cagnotti & Gatti: The Zürich - Locarno Method

09:05 – 09:30: L. Svalgaard: Study of the weighted sunspot count at Locarno

09:30 – 09:50: W. Poetzi: Sunspot observations at the Kanzelhöhe Observatory

09:50 – 10:30: R. Howe & J. Riggs: The American Sunspot Number from the AAVSO

10:30 – 10:40: F. Clette: A 70-year long comparison of Ra and Ri

10:40 – 11:00: Discussion: questions and clarifications about the practices at Locarno

11:00 - 11:20: break

Sunspot & facular areas (Chair: A.Pevtsov)

11:20 – 11:40: D. Willis: The Greenwich Photo-heliographic Results, 1874 - 1976.

11:40 – 12:00: A. Tlatov & V. Erschov: Numerical processing of sunspot images using the digitized Royal Greenwich Observatory Archive

12:00 – 12:20: A. Tlatov, D.Lepshokov & V. Vasil'eva: Reconstruction of the characteristics of sunspots in the period 1853-1879

12:20 -12:40: Discussion: about developing standards for measuring sunspot areas.

13:00 - 14:00: lunch

Recent sunspot activity and the fading of sunspots (Chair: A. Pevtsov)

14:00 – 14:20: Alexei Pevtsov: Sunspot Magnetic Fields and umbral areas in Cycles 15-19

14:20 – 14:40: H. Hudson (F. Watson): A first systematic look at sunspot statistics from space

14:40 – 15:00: L. Lefèvre & F. Clette: Are the sunspots vanishing ? What was different in cycle 23 ?

15:00 – 15:30: G. de Toma: Sunspot variations over two solar cycles

15:30 - 15:45: break

15:45 – 16:05: M. Penn (teleconf) : Changing Distribution of Umbral IR Magnetic Field Strengths and Application to F10.7

16:05 - 16:20: L. Bertello: Sunspot field strength measurements from Mt. Wilson Observatory

16:20 - 16:40: A. Pevtsov (J. Nagovitsyn): On a possible explanation of Livingston-Penn effect

16:40 – 17:00: Discussion: Cycle 23 anomalies and lessons for the past sunspot record.


AM: Discovery of Brussels: group sightseeing tours

PM: Free afternoon, Split meetings (science or technical)


Using geomagnetic indices and cosmogenic isotopes to calibrate the SSN (Chair: E. Cliver)

08:30 - 09:10: L. Svalgaard: Using the daily range of geomagnetic activity as a consistency check on the ISN

09:10 - 09:40: I. Cnossen: The effects of secular change in the Earth's internal magnetic field on geomagnetic activity

09:40 - 10:10: K. Mursula: Does sunspot number calibration by the “magnetic needle” make sense?

10:10 – 10:50: I. Usoskin: Using Cosmic Rays to Justify the Consistency of the SSN

10:50 - 11:10: break

11:10 - 11:40: Discussion: on the use of geomagnetic and cosmogenic isotope proxies

Reconciling the International and Group SSNs (Part 1) (Chair: F. Clette)

11:40 – 12:20: J. Vaquero: Sunspot data from 17th-19th centuries

12:20 – 12:40: D. Willis & M. Wild: Reconciling the International and Group Sunspot Numbers: Evidence from the Greenwich Photo-heliographic Results.

12:40 – 13:00: F. Clette & L. Wauters: Reconstructed Group SSN over the last 40 years: some insights

13:00 - 14:00: lunch

Reconciling the International and Group SSNs (Part 2) (Chair: F. Clette)

14:00 – 14:40: R. Arlt: Sunspots observations before 1900 in their originals

14:40 – 15:00: I. Usoskin: Computation of clean Wolf and group numbers from Schwabe's originals

15:00 – 15:30: L.Svalgaard: Rectifying the GSN and ISN after 1826

15:30 - 15:50: break

15:50 – 16:10: Discussion: on remaining issues in the SSN and group SSN

CaII-K line index & other Sunspot Number Proxies (Chair: L. Bertello)

16:10 – 16:40: L. Bertello: How well do the Ca II K index time series correlate with the ISN?

16:40 – 17:00: P. Foukal (teleconf): title TBC

19:00: Workshop banquet in downtown Brussels.


CaII-K line index & other Sunspot Number Proxies (Part 2)

08:30 - 8:50: A. Pevtsov: Consistency of Ca II K daily measurements

New mathematical techniques applied to the sunspot series

08:50 – 09:10: M. Laurenza, The Empirical Mode Decomposition to study the sunspot number variability.

09:10 – 9:40: T. Dudok de Wit: title TBC

9:40 - 9:50: Discussion: which innovative mathematical tools are most promising for progressing on the SSN series?

09:50 - 10:10: break

10:10 – 11:40: Workshop Summary/Discussion & Mid-Course Assessment (Chair:E.Cliver)

All participants + Observers: R. Brajsa, H. Hudson, N. Crosby, G. De Toma

11:40 – 12:10: Planning for the Third SSN Workshop (Chair: E.Cliver & F. Clette)

12:10: end of the meeting

13:00 - 14:00: lunch (possible at the ROB cafetaria)

Registration and social activitiesEdit

Please note that for payment of the activities (registration on Monday), we can only accept cash payments in Euro.

The fee for the walking tour is 8 euro/person.


The Observatory is within walking distance of both hotels, County House and Les Tourelles (about 30mins).

Alternately, you can use public transportation:

From “Les Tourelles”: bus 60, Direction “Uccle-Calevoet”, Stop at “Mercure”

From the County House: tram 92, Direction “Fort Jaco”, Stop at “Lagrange”

or bus 43, Direction “Observatoire”, Stop at “Observatoire” (terminus)

Because of ongoing transformation works, the main entrance gate (North) is currently not accessible. Therefore, you must enter the site via the back “deliveries” gate (South). From there, you will find indications (signs) guiding you to the meeting room.

Please check the attached maps.

SSN workshop Web siteEdit


On this site, you can find general information, the announcements and the presentations of the 1st SSN Workshop. All presentations of this 2nd Workshop will be added after the meeting. So, stay tuned to this site for further announcements and updates.

Leif is the curator for the website so please contact him with any questions or suggestions (