ON-AIR FAQ "Auroras - Living with a Star"

Auroras   Coronal Mass Ejections   Earth's Magnetic Poles   Solar Wind

Auroras

QUESTION:
When will the next auroras occur?

ANSWER:
The next aurora is occurring right now. There is aurora almost all the time, somewhere. Nobody may be there to see it, but if you were to look down from a satellite, and you could see the entire globe, you'll see almost all the time that there is an oval shaped ring of light around the magnetic pole. Often this aurora looks boring from the ground, and often it is not where you are. And, of course, looking from the ground, you need clear skies. Here in Fairbanks (and according to the radio weather report everywhere in Alaska) the weather is so bad, I can't even see the trees on the other side of the parking lot. So there may be aurora once it gets dark, but I am not going to see any of it.
Dirk Lummerzheim
Geophysical Institute of the University of Alaska Fairbanks

QUESTION:
When did auroras begin to appear or when did people start showing interest in them?

ANSWER:
Aurora has been here longer than we humans have. And I am sure the Neanderthal people would have seen them, and probably were frightened by them. According to a book by R. Eather "Majetic Lights" there may be references to aurora in the Bible. Looking at the ancient literature, there are sometimes strange lights in the sky, but it takes some imagination to relate this to aurora. But consider that it is a very rare event to see aurora in the ancient world around the Mediterranean, and that the people living there and then had no idea what it was what they were seeing. So descriptions of angry gods throwing flames, or warriors in the sky fighting that the sparks fly off their weapons may actually be inspired by sightings of aurora. Unfortunately, the ancient people of the north, either in Scandinavia or North America, did not leave any written records. But there are old legends among the Eskimo and Athapascan people which involve the aurora. Often these old stories describe the aurora as something that is to be feared.
Dirk Lummerzheim
Geophysical Institute of the University of Alaska Fairbanks

QUESTION:
How do auroras happen?

ANSWER:
Dear Writer,

A question that goes to the heart of the topic I'd say. In brief, aurora are caused by the interactions of solar particles and the Earth's magnetosphere, its magnetic shield. The particles may have their source as part of the solar wind that blows away from the Sun and into space or more commonly, be from a solar storm that blastted out from the Sun. When these particles reach Earth in two to four days, they interact with and excite charged particles trapped in the Earth's magnetic field 60 to 600 miles above the Earth. Energy is transferred and the paricles begin to glow different colors. This is a short version fo all that takes place, but a good overview I hope. It has taken science hundreds of years to figure this all out and the details are still being studied carefully.
Steele Hill
SOHO Media Specialist
NASA Goddard Space Flight Center

QUESTION:
What are the diferences with auroras on Earth can auroras on Jupiter?

ANSWER:
While I am not an expert on this, I think I can help. The aurora on Jupiter do not seem to be as colorful as those on Earth and this is probably because the elements that are excited do not glow in reds and yellows and greens. Different elements, different colors. But they are certainly a similar type of phenomoenon. Saturn's aurora are larger because it is so much larger than Earth and, thus, has a much stronger magnetic field. But in proportion to the size of Earth, they seem roughly about the same. I hope this helps.
Steele Hill
SOHO Media Specialist
NASA Goddard Space Flight Center

QUESTION:
How long do auroras last? How many different colors can auroras be?

ANSWER:
Dear Writer,

That's a good, practical question. A very faint aurora might only be visible for a few seconds perhaps, whereas aurora caused by a major solar storm might last off and on for several days, though it would not be visible during the day. The typical aurora display seems to last perhaps an hour or two. Sometimes they fade away but reappear minutes or hours laters. But if you ever see one, you will never forget it! As for colors, green is the most common, followed by blues and reds and yellows. Sometimes one color is about all you see; other times, one dominates with a little bit of the others; and finally sometimes there are all the colors about evenly distributed.
Steele Hill
SOHO Media Specialist
NASA Goddard Space Flight Center

QUESTION:
What happens if the particles do not reach 10,000 volts, how will that affect the wave lengths? Also is the color of the wave determined and how do the waves change and at what altitude?

ANSWER:
The particles that cause the aurora are energized in the magnetosphere, that is, above the atmosphere. If they don't reach 10,000 volts, they will still cause auroral light. The lower energy won't change the wave length of the light, but will cause the light to be dimmer.

The color of the light wave, or its wave length, is determined by the atom in the atmosphere that is excited by the particle. For example, oxygen atoms will emit green light. This green light is typically emitted at altitudes around 100 km. The red light from auroras comes from atoms at higher altitudes, 300-500 km.

I think of the aurora like a set of TV screens at various altitudes, each emitting different colored light. The particles hit the atoms in the TV screen and they glow in their particular color. The light from each screen then travels to the ground where we see it with our eyes.
Dr. Bill Taylor
Project Manager
Raytheon at NASA/GSFC

QUESTION:
Why does auroras boreales have so many colors like a rainbow?

ANSWER:
The aurora has many colors because there are different kinds of atoms in the atmosphere that are excited by electrons and ions from the magnetosphere. Each of the atoms can be excited to various levels and when the atoms emit auroral light, the higher energy levels, emit higher energy light. For example, red light is lower energy than purple light.

The atmosphere is made up mostly of nitrogen, oxygen, and argon. There are smaller amounts of other gases, like helium. Each atom will emit its own colors.
Dr. Bill Taylor
Project Manager
Raytheon at NASA/GSFC

QUESTION:
Why do auroras appear in different colors and how do they get that way?

ANSWER:
The different colors of the aurora arise because different auroral particles are exciting different chemical species (mainly atomic oxygen and molecular nitrogen) are being bombarded by auroral particles. Depending on how energetic these particles are, different energy-level transitions are being excited by the bombardment. Green light is common, coming from atomic oxygen. If the particles are very energetic, red and blue light may start appearing near the bottom of the auroral curtains.
Mark Conde
Assistant Professor of Physics
Geophysical Institute of the University of Alaska Fairbanks

QUESTION:
Can auroras ever be seen clearly with calm winds and inactive sun?

ANSWER:
If you mean "winds" on earth, they have nothing to do with the aurora. If you mean "solar winds", then the aurora is seen only in the polar cap. There is always aurora. When the sun is active, the solar wind is stronger and the aurora occurs more often at lower latitudes. When the sun is inactive, and the solar wind calm, the aurora occurs at high latitudes.
Chuck Deehr
Geophysical Institute of the University of Alaska Fairbanks

QUESTION:
Which is the southest point where aurora can still be seen?
Pedro
Universum Science Museum in Mexico City

ANSWER:
The aurora has come as far south as the southern border of the USA. It occurs at an altitude of 100 to 1000 km above the earth, so it may be seen as far south as Yucatan or central Mexico. This occurs about once every ten years.
Chuck Deehr
Geophysical Institute of the University of Alaska Fairbanks

QUESTION:
How can you determine where and when an aurora will appear/occur?

ANSWER:
It depends on how far in advance you want to predict. The aurora is caused by activity on the Sun. Certain solar features known as "coronal holes" last for several months, and cause auroral activity when they are facing Earth. Because the Sun rotates once every 27 days at its equator, if a coronal hole produces activity today, we can predict similar activity in another 27 days. Another source of activity are solar flares. These are not easily forecast but, once they occur, it takes 1 to 3 days for the material that erupts from the Sun to reach Earth. Finally, there are several spacecraft permanently located about 1 hour "upstream" of Earth in the solar wind. If these spacecraft see a cloud of material heading to Earth, we get about one hour's warning. As for where the aurora will be, it will occur on mostly the nightside of Earth. If the aurora is quiet, it will be about 20 degrees of latitude from the magnetic poles. As activity increases, the aurora moves south, reaching to middle and low latitudes during big storms.
Mark Conde
Assistant Professor of Physics
Geophysical Institute of the University of Alaska Fairbanks

QUESTION:
What causes the shape and color of an aurora? Why can you only see aurora's clearly with ultravioletness?

ANSWER:
The color is caused by oxygen and nitrogen atoms that are being 'energized' by collisions with fast-moving currents of particles flowing towards earth. These currents come from a region of space called the 'magnetotail' which is a part of Earth's magnetic field. As this 'tail' flaps around with the passing solar wind, it gets stressed and causes particles to get boosted in energy. These particles then flow along the magnetic field into the polar regions to stimulate the aurora. The shapes are caused as the magnetic field in the magnetotail re-arranges itself and causes the flows of particles to change their direction and intensity.
Dr. Sten Odenwald
Astronomer
Raytheon at NASA/GSFC

QUESTION:
Is the Aurora the same as seeing different colors in the sky? How often do Auroras occur and does the weather have something to do with it?

ANSWER:
Auroras happen nearly all the time, but the very colorful and spectacular ones you may be thinking about require a passing solar storm or 'CME' to trigger them. The different colors you see depend on where the incoming energetic particles are arriving from, and their energies when they enter the atmosphere. They also have to be boosted in energy within the ionosphere which adds another complication to the process.
Dr. Sten Odenwald
Astronomer
Raytheon at NASA/GSFC

QUESTION:
Would it be possible to use the energy that generates aurora for the commercial production of electricity?
Jesus
Universum Science Museum in Mexico City

ANSWER:
Not very easily. A powerful aurora can produce about 800 gigawatts of power, but most of this is involved in heating the upper atmosphere. Even if a gigawatt of this was electrical, it is distributed over many millions of square miles so its usable energy at ground is far less than what you get from sunlight falling on a solar cell.
Dr. Sten Odenwald
Astronomer
Raytheon at NASA/GSFC

QUESTION:
You told that it is possible to see some auroras in Mexico, is it possible to know when it will be the next one?
Pedro
Universum Science Museum in Mexico City

ANSWER:
The best way to do this is to follow the appearence of major coronal mass ejections on the sun. When a 'halo CME' is identified in the reports, this could mean that in a few days earth's magnetic field will be shaken enough to produce a major geomagnetic event. You need an event with a Kp of at least 8-9 to cause aurora to be seen at low latitudes. You get about 2-3 of these every sunspot cycle and I think we have already gotten our quota!
Dr. Sten Odenwald
Astronomer
Raytheon at NASA/GSFC

Coronal Mass Ejection

QUESTION:
I learned that CME's can have so much mass that it could be compared to the mass of 1000 luxury cruiseships. If they are so massive, could they have inflicted some damage on the space shuttle Columbia while in orbit?
Western Adventist School (Mayaguez, Puerto Rico)

ANSWER:
Dear Writer,

Yes, you are correct about the mass involved in a CME. However, we have to put that fact in context. We are talking about particles that are heading out into space, expanding as a huge cloud over 30 million miles wide by the time it reaches Earth. In fact, at Earth its density is so low that it would not even be enough to create a breeze, if there were such a thing in space. So, no, it could not inflict physical damage on the shuttle. A shuttle could be impacted by radiation from such a storm or one like it, but there is no chance for physical impact. thanks!
Steele Hill
SOHO Media Specialist
NASA Goddard Space Flight Center

Earth's Magnetic Poles

QUESTION:
Does any harmful effect exist for the organisms that live in the magnetic poles due to the flows of energetic particles that are given?
Miguel
Universum Science Museum in Mexico City

ANSWER:
Not at the ground. Earth's atmosphere is a thick blanket, and it shields us from these particles. Passengers in high-flying aircraft may experience a minor hazard (similar to having an x-ray) during a large solar proton storm.
Mark Conde
Assistant Professor of Physics
Geophysical Institute of the University of Alaska Fairbanks

QUESTION:
What does it happen with the magnetosphere during the inversion of the magnetic poles?
Tere
Universum Science Museum in Mexico City

ANSWER:
Nobody knows how a pole reversal is actually going to happen: does the magnetic field just turn off, and then turn on again with reverse polarity? Does the pole start moving towards the equator and then up (or down, depending on your point of view) towards the other side? What we can say about magnetospheres in these two scenarios comes from observations of other planets. Venus, for example, has no magnetic field, but a dense atmosphere. We can see that such a planet has an ionosphere with some very strange and very weak aurora all over the dark hemisphere, but there is no magnetosphere. Uranus, on the other hand, has a magnetic field such that the magnetic pole is on the equator, so we can see what the magnetosphere in such a situation looks like. What we have there is a twisted magnetosphere that changes very rapidly over the course of a day. The aurora on Uranus is also very strange, strongest during high noon, and best seen at the equator.
Dirk Lummerzheim
Geophysical Institute of the University of Alaska Fairbanks

Solar Wind

QUESTION:
What is a "solar wind"? In ancient civilizations were auroras thought to be signs from their gods?

ANSWER:
The solar wind is a very small portion of the ionized atmosphere of the sun that is blown away from the sun by its tremendous temperatures.

The outer atmosphere of the sun is called the corona and its temperature is millions of degrees. So some of the atoms in the corona are moving very, very fast and can escape the sun. The surface of the sun is only about 6000 degrees, much cooler than its atmosphere.

Very perceptive, some ancient civilizations did think auroras were signs from gods. Others thought that they were light from fires burning over the horizon or from sunlight reflected off of snow on the ground.

I hadn't even seen aurora live and in person until after I had studied their effects for several years. So I knew what caused them. When I did see them for the first time, I was awed by their magnificence and beautiful colors. If I had not known what they were and saw them, by surprise, for the first time, I can't imagine what I would have thought they were! What do you think you would have thought?
Dr. Bill Taylor
Project Manager
Raytheon at NASA/GSFC

QUESTION:
What is a "solar wind"? In ancient civilizations were auroras thought to be signs from their gods?

ANSWER:
The solar wind is gas from the sun that is fast enough to escape to space. It is mostly protons and electrons carrying the solar magnetic field. It moves outward at 300 to 2000 km/sec. These particles enter the earth's magnetic field when the sun's magnetic field connects with it. Ancient civilizations looked to the stars for signs from their gods. The infrequent appearence of the aurora overwhelmed the people who were used to seeing small changes in the night sky. It must have been a big event and it would be remembered for a long time.
Chuck Deehr
Geophysical Institute of the University of Alaska Fairbanks