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SUNSPOTS VANISHING, AGAIN For the second time this month, the solar disk is blank, no sunspots. This image of the sun taken by NASA's Solar Dynamics Observatory on June 24th shows zero dark cores. What does this mean? The solar cycle is like a pendulum, swinging back and forth between periods of high and low sunspot number every 11 years. Today's blank sun is a sign that the pendulum is swinging toward low sunspot numbers. In other words, Solar Minimum is coming. Forecasters expect the next Solar Minimum to arrive in 2019-2020. Between now and then, there will be lots of spotless suns. At first, the blank stretches will be measured in days; later in weeks and months. When the sunspot cycle reaches its nadir, a whole year could go by without sunspots. However, don't expect space weather to go away. Solar Minimum brings many interesting changes. For instance, as the extreme ultraviolet output of the sun decreases, the upper atmosphere of Earth cools and collapses. This allows space junk to accumulate around our planet. Also, the heliosphere shrinks, bringing interstellar space closer to Earth. Galactic cosmic rays penetrate the inner solar system, and Earth, with relative ease. Indeed, a cosmic ray surge is already underway . Cosmic rays can seed clouds, trigger lightning, and penetrate commercial airplanes. Measurements show that someone flying back and forth across the continental USA, just once, can absorb as much ionizing radiation as 2 to 5 dental X-rays. This exposure will increase as Solar Minimum deepens. 
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