If a spacecraft keeps chugging along for long enough, eventually it may find something startling.
It's an exciting find for scientists studying the stars--a new weather condition adds a new variable in terms of research. But what does a weak solar wind really mean?
One possible outgrowth of a prolonged weakened solar wind could have to do with climate change. Experts agree that solar cycles can have an effect on the Earth's climate. But they don't agree on much more than that, according to Boston University astrophysicist Nancy Crooker. "Models are so rudimentary that we can't even predict how much effect the sun can have," she told PM.
For this type of sun shift to have a direct impact on global warming, Crooker insistes, the first star would have to go through a more substantial change than the standard 11-year cycle of minimums and maximums. "Eleven years is not enough time for the climate to respond to anything solar," she said. In the late 17th century, for example, the sun entered a much longer, sustained low, and at the same time the Earth suffered through a moderate cooling.
So what matters for climate, Crooker said, is whether this downturn in the solar wind's strength becomes a long-term downturn in the sun's radiation. There's some evidence that the sun undergoes a 100-year cycle in the intensity of its sunspots during solar maximum, and that we're currently nearing the bottom of that cycle. But the pattern is weak, she said, and therefore it's a stretch to claim that the sun is currently counteracting global warming with global cooling, though it is possible. "We can't discount it," she said.
The most realistic effect of a reduced solar wind is that it could threaten the lives of astronauts. Flying around outer space is a dangerous proposition at any time, and not just because of the lack of oxygen or the incredible distances. Cosmic rays, energetic particles mostly including protons, helium nuclei and electrons, come from both the sun and from other sources and fly all over the place. And they are dangerous to our health: Like other ionizing radiation, they can damage DNA and cause diseases such as cancer and cataracts. The Earth's magnetosphere shields orbiting shuttles and space stations from this radiation, but anybody trekking to the moon or Mars had better watch out. The current finding of an especially weak solar wind means that "this is not a good time to be traveling in space," says Crooker.
Solar wind usually creates a bubble around our solar system called the heliosphere, which keeps out most cosmic rays from the rest of the galaxy. But a weak solar wind means a weak heliosphere, and more cosmic rays crossing through our area. "The smaller the heliosphere gets, the less shielding we get," said Dave McCombs of the Southwest Research Institute.
Solar maximums are no picnic, either. When they occur, the sun produces many more coronal mass ejections (CMEs), intense bursts of cosmic rays often associated with sunspots. CMEs are certainly dangerous to astronauts, but, Crooker said, many NASA officials consider them the lesser of two evils when compared to a solar minimum. If cosmic rays come in short bursts, as in a CME, astronauts could take cover behind shielding and wait them out. But if weak solar wind and therefore weakened shielding continues, astronauts would have no place to hide from the constant barrage.
Scientists won't know whether we're really entering a long period of low solar activity until they've measure data over time. Ulysses, which was already 13 years past its four-year planned life span when it delivered yesterday's discovery about the solar wind, will probably die in the next few months when its fuel freezes.
But fear not: One of Ulysses' finest achievements in its years of monitoring the sun's poles was finding that the intensity of solar wind at the sun's poles is the same as it is at the sun's equator, so the distribution of the solar wind is basically uniform. Most of our satellites are on the sun's equatorial plane, so even if a Ulysses replacement never reaches the top of the list for NASA funding, other satellites can now take measurements and be confident that the data they measure on the sun's equatorial plane hold true for the whole solar system.