No Magnetic Field?

The sun is generally supposed to have a magnetic field more powerful than that of the earth. The scientific reasoning: the lines in the sun's spectrum seem to show the "Zeeman effect," splitting in two like the lines in a laboratory light source affected by magnetism. But Dr. Martin A. Pomerantz of the Bartol Foundation had long doubted the sun's magnetic field. Last summer he set out to disprove the theory by the apparently far-fetched method of catching cosmic rays with sounding balloons near the earth's north magnetic pole.

When a cosmic ray (an electrically charged particle from outer space) approaches the earth, it is deflected by the earth's magnetic field. If it is speeding fast enough, it slams through this interference and plunges into the atmosphere. The most powerful particles, whose speed gives them an energy of 14 billion electron-volts, can reach the earth at the equator, where the magnetism is strongest. At the latitude of Philadelphia, two billion volts is enough.

Dr. Pomerantz figured that near the north magnetic pole in northeastern Canada the earth's magnetic field is so feeble that even the most sluggish rays should make the grade. He also reasoned that if he could find rays so feeble that they could not theoretically get through the supposed magnetic field of the sun, he would have proved that such a field does not exist.

With the backing of the National Geographic Society and the help of the Defense Research Board of Canada, Dr. Pomerantz launched high-flying balloons from Churchill on Hudson Bay. At this point of feeble earth magnetism, Geiger counters attached to the balloons found what Dr. Pomerantz was looking for: cosmic rays with only 100 million volts of energy. Such rays would be much too feeble to reach the earth from outer space if they had to break through the magnetic field attributed to the sun. Therefore, Dr. Pomerantz announced last week, the sun must be bare of permanent magnetism, and the physicists must find some other way to explain its Zeeman effect.

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