In a method and a control sequence determination device and a magnetic resonance system for the determination of a magnetic resonance system activation sequence as a multichannel pulse train with multiple individual RF pulse trains to be emitted in parallel by the magnetic resonance system respectively via multiple independent radio-frequency transmission channels of a transmission device, the multichannel pulse train is calculated in order to achieve a defined local target magnetization distribution upon emission of the calculated multichannel pulse train. The local target magnetization distribution is obtained as a parameter map determined from image data obtained with preceding measurement.