Solar cycle properties and surface-field reconstruction from sunspot observations by Schwabe

• Applicant: Dr. Rainer Arlt
• Subject Area: Astrophysics and Astronomy
• Term: from 2013 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 232231278

A continuous record of detailed information on sunspot groups has been available since 1874. The understanding of the solar cycle would greatly benefit from a longer time series into the past. We propose to use newly available sunspot positions and areas measured on the original drawings made by S.H. Schwabe in 1825-1867. The observations were digitized by the PI in 2009. The individual positions and areas of the sunspots as well as their groupings in active regions were obtained within DFG project. We propose to test and improve empirical relations for the reconstruction of magnetic maps with these data. Such maps as well as time series for the total and open flux will be reconstructed using a surface flux transport model. We will also study the north-south asymmetry from the spot data, possible phase shifts in the cycles on the northern against the southern hemisphere, and sunspot decay leading to turbulent diffusion values in the solar atmosphere. Another goal is the determination of the differential rotation of the Sun in the 19th century.

• DFG Programme: Research Grants