According to the report of National Space Weather Monitoring and Early Warning Center, on February 13, 2006 10: 40 Beijing time, another 3.4-magnitude solar flare occurred.

(1) Solar activity causes the phenomenon of "aurora" in the polar regions, which is wrong; (2) The solar activity disturbs the earth's magnetic field, resulting in a "magnetic storm" phenomenon, and the earth's magnetic needle cannot correctly indicate the direction, which is correct; (3) solar activity disturbs the ionosphere, interferes with radio short-wave communication, and pagers and mobile phones will fail, which is correct; (4) The latitude of Mohe River is lower than that of the Arctic Circle, so there will be no extreme day phenomenon, which is caused by the revolution of the earth and has nothing to do with solar activity.

Therefore, choose: d.