Nordita Astrophysics Seminars

Astrophysical Dynamos: before 2009, now, and elsewhere

by Axel Brandenburg (Nordita)

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The era of the ERC-supported AstroDyn project at Nordita comes to an end this month. What difference did this project make to our understanding? This can be assessed by recapitulating the situation before 2009. People just began using the test-field method for calculating mean-field dynamo coefficients, but now this methods is routinely producing interesting information. We did not have any knowledge about the memory effect in turbulent transport, but now this is quite well understood. We were worried about the gauge-dependence of magnetic helicity fluxes, but these worries have now been mostly overcome. Back in 2008, the original ERC proposal envisaged 14 target points. Six of them where particularly fruitful in terms of paper output:

  • Project 2 "Test-field method" (10 papers),
  • Project 7 "Magnetic helicity fluxes" (14 papers),
  • Project 8 "Magnetic flux concentrations" (18 papers),
  • Project 9 "CME-like features above dynamos" (6 papers),
  • Project 10 "Spherical shell dynamos" (7 papers),
  • Project 12 "Solar dynamos and forecast" (7 papers),

    i.e. 62 papers in total, which constitutes a major fraction of the total output of 105 refereed papers that all acknowledge the ERC project. Even the now most producing project 8 was already anticipated as being important, but we had no idea whether it would work. It took until 2011 to find out. In my summary of this ERC project I will contrast early knowledge prior to 2009 with the current one and its relevance within the broader context of the field.

    Link to the draft report for reporting period IV