Solar and Stellar Dynamos and Cycles



Alexander Kosovichev (Stanford University) , Maarit Korpi (Observatory, Helsinki University)

Nordita Events is where most of the daily talks of the program are being annouced.

Time table for the Ilkka fest link.

Programme routine and workshop

The first two weeks of the programme are dedicated to stellar dynamo theory and observations, and the last two for solar magnetic activity, dynamos and data assimilation methods. We plan to have informal gatherings over coffee every day at 10:00 and 16:00. For some of the days we shall schedule talks or formal discussions at 10:30.

We are also organising a special workshop during the 5th-6th of October in the honor of the 70th birthday of Professor Ilkka Tuominen. We aim to cover topics that Ilkka has actively pursued during his long and successful scientific career, namely spectroscopy and Doppler imaging of stellar magnetic activity, stellar activity cycles and the flip-flop phenomenon, and stellar dynamo theory. If you plan to attend all or part of the program, or if you would like to come to the special workshop on 5-6 October, please register on the page indicated above. Please indicated if you would like to give a talk. Alternatively, you may just email any of us. The most up-to-date time table with preliminary allocation of chair persons is on this link.


Understanding the origin of solar and stellar magnetic fields is one of the central problems of physics and astrophysics, and a key to understanding the cosmic magnetism, in general. There are two main difficulties in studying this problem: 1) magnetic fields are generated by turbulent dynamos in convection zones below the visible surface, not accessible by direct observations; 2) solar and stellar magnetic activity is a multi-scale phenomenon, involving physical processes on very small scales, probably, below the current observational limit, and at the same time showing remarkable large-scale spatial and temporal organizations over a whole star. The prime target of our investigation is the Sun, which serves as the Rosetta Stone in this field and holds the key to unlocking the secrets of magnetic field generation in the Universe. The most detailed observational data and theoretical models have been obtained for the Sun, but a very significant progress has also been achieved in observations and theories of magnetism on other stars.

Observationally, most efforts for solving the problem of solar and stellar magnetism are focused on developing helio- and asteroseismology for probing the structure and dynamics inside the Sun and stars and detecting changes associated with magnetic fields, on high- resolution observations for probing small-scale and even unresolved magnetic structures and their organization and evolution, and on studying large-scale patterns of sunspots and starspots and magnetic activity cycles.

Theoretically, this problem is addressed by developing physical models at three different levels of the spatial and temporal domain: 1) direct 3D MHD simulations of small volumes of the convection zone with the highest possible resolution to understand properties of MHD turbulence, helicity, diffusion and saturation mechanisms; 2) 3D mean-field and full MHD simulations of the interior of the Sun and stars for the global dynamo on the scale of the activity cycles; 3) non-linear dynamical models to investigate long-term evolution of the dynamo. These approaches have been developed independently and quite successfully by different groups.

Data assimilation is a powerful analysis method in which observed information is accumulated into dynamical models taking into account physical constraints and properties. This approach makes possible efficient and accurate estimations of physical properties which cannot be observed directly, and obtain better understanding of the underlying physics and develop forecast models.

At the beginning and the end of this program, we plan to hold short (2-3 days) general discussion meetings. Also, during the program, we will hold topical discussion sessions, as these are needed. Most work will be done in focused working groups. In particular, we propose the following initial tasks for discussion and investigation:

  • Physics of MHD turbulence and turbulent dynamo
  • Numerical dynamo simulations
  • Observational constraints on the solar and stellar dynamos
  • Mathematics of prediction and data assimilation

    Program details

  • Participants
    • Alexander Kosovichev
    • Allan Sacha BRUN
    • Axel Brandenburg
    • Balarac Guillaume
    • Dhrubaditya MITRA
    • Dmitry Sokoloff
    • Elias Holm
    • Eniko Madarassy
    • Erico Rempel
    • Fabio Del Sordo
    • Friedrich Busse
    • Guenther Ruediger
    • Gustavo Guerrero
    • Igor Rogachevskii
    • Ilkka Tuominen
    • Ilya Ilyin
    • Irina Kitiashvili
    • Jaan Pelt
    • Jan Eskil Snellman
    • Jörn Warnecke
    • Karl-Heinz Raedler
    • Kirill Kuzanyan
    • Kyösti Ryynänen
    • Laurene Jouve
    • Leith Arar
    • Luiz Garcia
    • Maarit Korpi
    • Marjaana Lindborg
    • Matthias Rheinhardt
    • Nathan Kleeorin
    • Nikolai Piskunov
    • Nobumitsu YOKOI
    • Oleg Kochukhov
    • Pekka Janhunen
    • Petri Käpylä
    • Piyali Chatterjee
    • Rainer Arlt
    • Simon Candelaresi
    • Thomas Hackman
    • Virendra K. VERMA