H_α isocontours overplotted on MDI magnetograms during the rise a) and the main phase d) of the flare; red (blue) colors indicate positive (negative) polarity. Overplots of 1600 Å TRACE isocontours on the corresponding MDI magnetograms during the rise b) and main phase e) of the flare. The contours levels are at 60, 70, 80, and 90% of maximum 1600 Å intensity in b), while they are at 70, 80, and 90% in e). Overplots of RHESSI isocontours over MDI magnetograms taken during the rise c) and main phase f) of the X3.8 flare. RHESSI data are integrated for 30 s around 08:04 UT c) and 09:43 UT f). Green isocontours indicate the emission at 12−25 keV, while orange and red isocontours indicate the emission at 25−50 keV and 50−100 keV, respectively. The contour levels are at 50, 60, 70, 80, 90, and 95% of maximum intensity.