Blast from the past

 In August 1972, a series of solar flares and associated geomagnetic storms led to widespread communications disturbances and power outages. On August 4th, the geomagnetic storm caused a nearly instantaneous detonation of dozens of sea mines installed by the US during the Vietnam War south of Hai Phong. The August 4th flare, which occurred between the Apollo 16 and Apollo 17 missions, led to a significant increase in the radiation level in the interplanetary space. It was estimated that for the astronauts on the moonwalk, the radiation dose equivalents would have been clinically significant, including nausea, vomiting, a very high probability of cataract formation, with a slight increase in the probability of death. This flare, which occurred more than 50 years ago, was well-observed by the H-alpha flare patrol telescope at the National Solar Observatory at Sacramento Peak. Image on the left shows the Sun before the flare, and on the right is the flare in progress. You can also see that a portion of filament left of the flaring region had disappeared. These are the signs of a coronal mass ejection erupting from this area of the Sun. Study of the past events may bring invaluable information  about how such strong eruptions develop and help us to prepare for traveling to the Moon and Mars.