First-principles-based modeling of geomagnetically induced currents (GIC) at mid- and low-latitudes Pulkkinen, A., N. Buzulukova, L. Rastaetter, M. Kuznetsova, A. Viljanen, and R. Pirjola 1 December 18, 2008, fall AGU, San Francisco, CA

Motivation Two-level experimental GIC forecasting system has been running at the Community Coordinated Modeling Center since February But the short lead-time Level 2 forecasts have a problem… December 18, 2008, fall AGU, San Francisco, CA 2

April 29, 2008, Space Weather Workshop, Boulder, CO 3 Lagrange 1 observations used as boundary conditions for magnetospheric MHD. NASA’s ACE data used. Magnetospheric MHD model (BATS-R-US) used to model the magnetospheric-ionospheric dynamics. Computations carried out at the Community Coordinated Modeling Center. Magnetospheric MHD output used to drive geoelectromagnetic induction and GIC code providing GIC at individual nodes of the power grid. GIC forecast file is generated. MHD provides only high-latitude currents. MHD provides only high-latitude currents.

Motivation … and GIC occur also at mid- and low- latitudes. December 18, 2008, fall AGU, San Francisco, CA 4 Gaunt and Coetzee (2007)

5 “Low latitude problem” Domain not included in magnetospheric MHD

The challenge Need information about the near-space current systems generating electromagnetic field fluctuations in the mid- and low-latitudes.  Inclusion of realistic inner magnetospheric non- MHD physics needed. (Challenge 1) Field-aligned currents cannot be assumed to be perpendicular to the ionospheric plane.  Need to use more general methods for solving the geomagnetic induction problem. (Challenge 2) December 18, 2008, fall AGU, San Francisco, CA 6

The solution (Challenge 1) Use Comprehensive Ring Current Model (CRCM) to model the inner magnetosphere. Drive CRCM with global MHD. For details, see poster SM11A-1571 by Buzulukova et al. December 18, 2008, fall AGU, San Francisco, CA 7

CRCM-BATSRUS one way coupling KAMELEON interpolation library Linear interpolation: MHD ionosphere grid- CRCM ionosphere grid KAMELEON interpolation library CRCM run MHD BATSRUS run at the CCMC MHD B-field B-field at the whole CRCM region electric field potential in the ionosphere CRCM potential in the ionosphere at the CRCM polar boundary MHD T, n Equatorial n,T at the CRCM polar boundary CRCM polar boundary Region II Birkeland currents3-D H+, e- fluxesSelf-consistent E-field

The solution (Challenge 2) Develop an extended Complex Image Method (CIM) to deal with arbitrary field- aligned current orientations. December 18, 2008, fall AGU, San Francisco, CA 9 Complex Image Method (1) (2)

Initial test Drive BATS-R-US MHD with ACE observations for the August 12, 2000 storm event. Drive CRCM with MHD output. Use ionospheric 5-minute resolution output of CRCM with extended CIM to compute the ground magnetic field fluctuations at mid-latitudes. As a first-order approximation, include the magnetic field perturbation due to the ring current via Dessler-Parker- Sckopke relation. Compare to observations averaged to 5-minute resolution. December 18, 2008, fall AGU, San Francisco, CA 10

Initial results December 18, 2008, fall AGU, San Francisco, CA 11

Initial results December 18, 2008, fall AGU, San Francisco, CA 12 Hours from the beginning of August 11, 2000.

Initial results December 18, 2008, fall AGU, San Francisco, CA 13 Quantitative comparisons to follow Hours from the beginning of August 11, 2000.

Summary Mid- and low-latitude GIC addressed in terms of coupled CRCM/MHD and extended CIM. Future development includes: a)Inclusion of the effect of an asymmetric ring current. b)Calculation of actual GIC. December 18, 2008, fall AGU, San Francisco, CA 14