An Analysis of A Large Flare, on the Solar Disc of 1984 February 25

A large 3B energetic flare on the solar disc (N16 E48, Y. N. 84044 or Boulder 4423) was observed at Yunnan Observatory on February 25, 1984. The analysis show. 1. This large flare occurs on both sides of the magetic neutral line(H₁₁) with the shearing motion of sunspots, newly emerging flux and great magnetic field gradients.2. The flare covers not only the penumbrae of some following spots, but also their umbrae before and after the maximum of the flare.3. During the eruption process of the flare the strong magnetic field varies of the corresponding active regions of photospheric spots. The increase rate of magnetic flux and the maximum magnetic geadient are 1.0×10⁸ veb/sec and 0.2 G/km, respectively.4. The maximum velocity of the relative motion of one sunspot with respect to another may be 0.3 km/sec.