Skip to comments.Space Mailbag: What's Up with the Sun?
Posted on 11/06/2003 12:23:19 AM PST by Aracelis
Questions about the Recent Wild Solar Activity
Readers had many questions about the recent, historical round of 10 solar flares in two weeks and their associated space storms (called coronal mass ejections, or CMEs) that hit Earth. I got behind with the Mailbag because the flares just would not stop -- blame it on the Sun! -- but here, finally, are some answers (recent additions at the top):
Kurtis writes: Is there a possibility that since humans have really only existed for .01% of our Sun's total lifetime, that the Sun is in the process of returning to its norm, and everything we have seen so far in the history of our star has been atypical and the recent activity is just the Sun resuming its normal pattern?
RRB: Hmm. I might buy some of that. You're right that scientists don't know enough about the Sun to predict all the nuances of its cycles and extremes.
We have good records of solar activity for just four centuries (starting with Galileo's observations of sunspots -- see below) and scant written records going back a few more centuries. Tree rings and ice core samples give strong clues about what the Sun was doing hundreds and even many thousands of years ago. But we don't know much about what it really used to do. The Sun is about 4.6 billion years old.
However, studies of other stars like our Sun -- younger and older -- provide indirect evidence for the Sun's past and likely future, so scientists are not totally, ahem, in the dark.
Now, all that said, a study earlier this year suggested -- this is not proven -- suggested that solar activity has been increasing for the past century, perhaps longer. Keep in mind, though, this old weather forecaster's axiom: A single bad storm, or even several in a row, does not signal a shift in long-term climate patterns.
Lynn writes: The way the Sun has been acting is kind of scary. Just what the heck is going on for so many out-of-season eruptions? Are the scientist beginning to wonder if something big is headed our way ... something never before seen from our Sun?
RRB: The series of powerful flares is indeed unusual. But there is no cause for serious concern beyond the effects possible from the individual storms (to satellites, communication and power grids). Humans on the ground are not in danger.
Like any star, the Sun is volatile. Imagine a campfire: It might burn calmly for a long stretch and then suddenly whip into a temporary frenzy. You might be surprised, but you'd think of it as relatively normal. That said, solar physicists will no doubt look into this amazing series of storms in hopes of learning more about what's behind them. The Sun remains largely mysterious.
By "out-of-season," you mean that the 11-year solar cycle peaked about two or three years ago and activity is generally in decline. That's true. Interestingly, though, historical data show that more major flares occur at this stage of the cycle than during the period of maximum solar activity. Just one more mystery.
Earnie writes: How fast does the Sun rotate on its axis? Is it likely that the current sunspots will still be active on the next rotation or next several rotations of the Sun? How long do sunspots last on average?
RRB: The Sun spins once on its axis every 25 days at its equator. It takes about 35 days for the ball of gas to rotate near its poles. Sunspots sometimes form and fizzle in a matter of days. Other times they last weeks.
Any of the three large sunspots seen over the past two weeks could rotate back into view in about two weeks.
Here's a cool fact: Galileo Galilei, back in 1612, discovered the Sun's rotation by noting the movement of sunspots. When he died in 1642, he was blind. Some accounts blame his blindness on an infection, but most experts agree looking at the Sun had something to do with it. Never look at the Sun!
Ann writes: Any chance these solar flares can interrupt airline travel or flight capabilities?
RRB: That possibility exists. The flare on Tuesday, Oct. 4 disrupted radio communications -- causing a total blackout at some wavelengths -- and increased radiation at high latitudes, such as the polar routes taken in trans-Atlantic flights. Last week, communications with pilots were disrupted. And some airlines rerouted planes for more southerly passages, based on a first-ever alert issued by the FAA.
There is little agreement on whether a typical passenger is at any great risk, however. NOAA estimates an airline passenger can experience as much radiation as 10 chest X-rays during a geomagnetic storm. This figure is debated. Experts do agree that anyone on a high-altitude jet, or an astronaut in space, is exposed to more radiation than someone on the ground. More here.
Laura writes: With all the recent activity the Sun has been sending our direction what could we expect if our protective geomagnetic field begins to weaken, or worse, what if our magnetic poles were to reverse as they have done many times in the past history of the Earth?
RRB: The magnetic field can get temporarily tired, one expert told me, so that back-to-back storms -- separated by hours -- might be more effective in penetrating Earth's natural defenses. This situation was set up last week, but we survived. Storms separated by days are not thought to gain any easier entry, however, at least not according to present knowledge. I'm not aware of any studies suggesting short-term solar activity can have anything to do with reversing Earth's magnetic field.
Jason writes: Is the space station shielded heavily enough for such activity from the Sun. That kind of exposure of radiation for such a long time cannot be good for anyone.
RRB: You're right that extra doses of radiation pose health risks. NASA monitors what astronauts are exposed to and limits their time in space. During intense storms, the residents of the International Space Station retreat to the Russian Zvezda service module -- the most protective. They did so several times last week. More about what the crew did last week is here. And here is a story about the radiation risk in general. Also, here's some interesting news about the radiation risk at Mars.
George writes: Is the Sun possibly preparing to enter the red giant phase of life? Are these flares a sign of the end for us?
RRB: No. The Sun is middle-aged at 4.6 billion years. It won't start swelling into its red giant phase for a few billion years. When that happens, anyone remaining on Earth will indeed be in trouble.
Mike writes: What is the likelihood of the CME affecting the asteroid belt? Does the CME have enough force to alter any of the asteroids?
RRB: I'm not aware of any studies done to quantify this. The orbits of asteroids are altered by sunlight. It's called the Yarkovsky effect and, over time, a rock's orbit and rotation change ever-so-slightly due to the constant radiation pressure. A flare would presumably add to that effect, but it's such a minor thing in the grand scheme that it would not have any near-term consequences, like redirecting a space rock immediately to Earth.
Scientists have pondered using the Yarkovsky effect to deflect an asteroid, if one were ever determined to be on a collision course decades or centuries down the road. Simply paint it white, perhaps, and let the Sun gently nudge it off course over the years.
Declan writes: Last week there was an article about an unexplained shadow (or storm), below and to the right of Jupiters Great Spot. Then this week, another highly unusual (nay unique) event takes place with the appearance of two huge sunspots and associated storms, in a period when the Sun is supposed to be winding down to minimum activity. Has anybody investigated the possibility that the two events may be in some way connected?
RRB: The spot on Jupiter was probably a locally generated atmospheric phenomenon, according to astronomers who regularly watch the gas giant planet. There's no reason I know of to think such spots -- similar ones have been seen before -- would have anything directly to do with increased solar activity, though solar energy in general certainly affects Jupiter. In this case, the Jovian spot came and went before the Sun got active, however.
25. And there shall be signs in the sun, and in the moon, and in the stars; and upon the earth distress of nations, with perplexity; the sea and the waves roaring;
26. Men's hearts failing them for fear, and for looking after those things which are coming on the earth: for the powers of heaven shall be shaken.
Given its current mass and the rate of decay/loss of matter, if it were this old the sun would have been much more massive, and burnt the earth to a crisp or its gravity would have sucked the earth into its maw.
Great point, thanx.
I hate the sun.
Been studying Chandrasekar's work?
Nah, I read a lot of different stuff, throw out hyperbole, and sometimes just take things the wrong way ;o)
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