Can you say anything about the April, 1997 solar storm?

Here's an excerpt from my upcoming book 'The 23 Cycle: Learning to live with a stormy star" Published in December 2000 by Columbia University Press . For more on this book, visit The Astronomy Cafe's 23 Cycle page.

"The instruments on board NASA's Solar and Heliospheric Observatory (SOHO) were routinely keeping watch on the Sun on April 7, 1997, when the EIT camera picked up a typical garden-variety, class-C6 solar flare in progress. Scientists back on Earth watched while a shock wave from the flare passed through the local gases in the solar corona like the waves from a pebble dropped into a pond. It was a beautiful event to watch, looking for all the world like some artful animation, rather than the awesome detonation that it actually was. In minutes, a ring of compressed gases had spread to engulf a patch of the Sun as big as the Earth. Radiation sensors onboard the geosynchronous GOES weather satellites detected a rain of flare particles minutes later. Meanwhile, radio telescopes began to detect the tell-tail radio waves from a Type II burst on the Sun. The CME, in its haste to leave the Sun, had shocked and compressed solar plasma ahead of it, snowplowing them into walls of stripped atoms and magnetic fields that emitted powerful blasts of radio waves. At 10:00 AM EDT, as the shock wave spent itself, the LASCO instrument witnessed a major CME grow to the size of the Sun and larger.

Three days later on April 10 at 7:00 PM EDT, the WIND and SOHO satellites, parked one million miles from the Earth towards the Sun, started to feel the direct impacts of energetic particles from the CME. The faint signals from the compressed interplanetary wind had already been sensed a few hours earlier. Ground-based magnetometer readings from CANOPUS, the Canadian magnetic observatory network, started to feel major changes in the Earth's field heralding a Large Storm Commencement at 10:00 PM EDT. Meanwhile, the POLAR satellite had already seen auroras begin to grow on the dayside of the Earth at 2:50 PM, EDT. By 5:26 PM, intense nighttime aurora could be seen in New Hampshire and Massachusetts as the aurora slid past the US-Canada border and plunged into the Lower-48. Many amateur photographers reveled in spectacular opportunities to capture on film both the dazzling auroral curtains, and the history-making comet Hale-Bopp.

The great series of domino events tracked by NASA satellites, literally from cradle-to-grave, prompted scientists to release a press announcement on April 8th that predicted the real meat of this CME would harmlessly pass about a few million miles below the plane of the Earth's orbit. At best it would be a glancing blow, and most probably not a direct hit. As seen from the Sun, hitting the Earth is not exactly a turkey shoot even with a million-mile-wide bullet. The magnetosphere of the Earth extends over 100,000 miles from the center of the Earth, and has about the same apparent size as a dime held at 30 feet. Even though CMEs are huge, the Earth is such a small target, you really have to get CME and solar flares pointed right at the Earth before there's a good chance of any physical contact happening.

The news media were especially fascinated by this cosmic salvo. The spectacular satellite images of its genesis millions of miles away, made the CME near miss almost irrelevant. It really didn't matter if the storm would only be a glancing blow this time. April 10th turned out to be a big news day for this cosmic non-event, with nearly all of the major national and international newspapers carrying some kind of story about it. Some reporters, unfortunately, rushed into press with rather sensational stories such as Matthew Wald's article in the New York Times, "Storm on Sun Is Viewed From Spacecraft; First detailed look at solar event that could effect life on earth", which was datelined April 9th and published on April 10, 1997. Meanwhile, CNN and Yahoo!News, reassuringly reported in their on-line news services that "Solar Flare small after all, poses little damage" (CNN) and "Solar Storm's Full Force to Miss Earth" (Yahoo). Even the Boston Globe reported "Not much flare to this solar event, experts say". NBC, CBS and CNN News, carried interviews with George Withbroe, Chief of the NASA Office of Space Science, and Nicola Fox, a scientist at NASA's Goddard Space Flight Center who coordinates the Global Geospace Science program. Nearly every news report mentioned possible technology impacts should the CME actually hit the Earth, including electrical blackouts and satellite outages. "

 


Copyright 1997 Dr. Sten Odenwald

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