Art Poland WebChat March 5

Guest: Dr. Art Poland, former U.S. Project Scientist for the SOlar and
Heliospheric Observatory:

GHS: How is SOHO today?

Art Poland: It's in an orbit maneuver and momentum management state today... we now have N(orth) up again so you don't need to twist your head around.

GHS: Tell us how you can navigate without gyros? In 2 sentences?!?

Poland: The gyros are only used for momentum wheel management, they are off most of the time. We use momentum wheels to keep the spacecraft steady. They are controlled by the Sun sensors and a star tracker. When the wheels get going too fast or too slow we used to turn on the gyros for position information and fire thrusters to offload momentum. Now we do it very carefully with the Sun sensor and the guide stars.

Art Poland: Hi, Sherri and Lowell, any questions about the Sun or SOHO?

Sherri Pergrem: This is my first interactive involvement with PASSPORT TO KNOWLEDGE programs. I'm here to learn anything I can about the program.

Art Poland: Well from my viewpoint I'd just like to help you teachers get the kids more interested in science. Another word might be "knowledgeable." If you want to get them more excited about the Sun, visit our web page then click on latest images. You can see "Today's Data" from space here.

We also have an "Ask Dr. SOHO" section, click TEACHERS and then "Ask Dr. SOHO". We are usually able to get answers back within a day. A teacher from California did that last year. Each day we had a few questions from kids in the class. She said it worked pretty well.

Eileen Bendixsen: When the Sun gets to be a red giant in about 5 billion years will the Earth be burnt up? How large will the Sun get?

Eileen Bendixsen: Hi Art! I have a student with me who heard about tornadoes on the Sun. He would like to know what exactly is a tornado on the surface of the Sun?

Art Poland: That is a good one. It looks like a tornado in our pictures. It is really a magnetic tornado. It is much bigger than the whole Earth. Give me a minute and I'll get the web address for more details on it, including pictures. This address has links to news stories tornadoes are there. If you want more scientific information about the tornadoes, send me an e-mail and I'll get back to you.

Eileen Bendixsen: Thank you. Garrett is going to look up the web page and we will get back to you if we need more information.

Lowell Bailey: Art, Janna Arthur would like to know if there has been any new information about the development or structure of sunspots from the Sun's sound wave data.

GHS: Art--a little bit ago there was a question about our Sun becoming a Red Giant: will it? And how does SOHO tell us about the life cycle of our Sun???

Art Poland: The Sun is just another plain old small to medium size star. Our computer model calculations allow us to see what the life history of a star is. We see that gases condense in the beginning: almost all hydrogen. When it gets dense enough you get nuclear reactions. That is what produces the Sun's energy. Right now we are in the plain old hydrogen reaction phase. After about 5 billion more years it will run out of hydrogen and the reactions will change. When that happens, the computer calculations tell us that the Sun will expand to a red giant. SOHO is telling us about the current structure of the interior of the Sun, so we can tell if the computer models are correct or not. So far it seems that the models are very close to correct.

Susan Hurstcalderone: Can you give us a little more information about the origins of magnetic tornadoes? This comes from Beth

Art Poland: On the origins of magnetic tornadoes. The Sun is a magnetic star. This magnetism is constantly moving around, kind of like after an egg cracks in a pot of boiling water. This magnetism would look kind of like the egg white twirling around in the boiling water. The tornadoes may be that sort of thing. We need to study them more to find out if that's really the situation or not.

That is what science is all about. You see something, you ask what it is and what causes it, you make a guess, then you find out if your guess is right or not. With tornadoes, we have seen it, we have made a guess, and we're trying to find out if our guess is right or not. So, to answer your question--we think the Sun's boiling near the surface is twisting the magnetic field and sometimes it twists it enough and in the right way to make what we see as a tornado.

Eileen Bendixsen: What new information have we learned about the cause of CMEs by using SOHO?

Art Poland: We first discovered CMEs in the early 1970s. At that time it seemed that they were caused by prominences erupting from the surface of the Sun. From SOHO we have actually been able to see not only prominences, but other magnetic instabilities give rise to CMEs. We seem to be seeing, sometimes, a global magnetic instability.

SOHO has been studying the interior structure of the Sun through helioseismology. That is like studying the Earth's interior by tracking sound waves. The sound waves bounce around inside the Sun and depending on the interior structure they give different patterns on the surface. We measure the sound wave pattern on the surface to deduce the interior structure. We are seeing that the structure (temperature, density, velocity) under sunspots is different than under other parts of the Sun. A really exciting thing is that we are now seeing sunspot structure in places before a sunspot appears there. So, we may be able to predict where and when a sunspot will appear.

An exciting result from the interior studies can be seen form mthe SOHO home page. Click on Solar Quakes.

GHS: Art--I think that was a pretty good answer: we have about 10 minutes left, so it's time for just a few more questions: students or teachers, before you zip off for lunch?

Art Poland: Any other questions out there? I could probably still push the keys a few more times.

More important than lunch is that it's a nice day so I'm going to go home and ride a horse or two.

GHS: It really is a beautiful day--but you're not going to get off too early: when you're out there in the sunshine, riding your horses, do you ever think that this is the same object you're studying back there at Goddard on all those computers? Last question!

Art Poland: Now that you mention it, mostly no. I guess it's like a surgeon and a patient. The Sun is an aesthetic thing to enjoy. Sometimes when I am working on it, I do reflect on how beautiful it is.

Lowell Bailey: I would just like to thank Art for being available to answer our questions!

GHS: So, Art, many thanks for participating--we'll be editing and posting the transcript, and readers/chatters, you can see Art in the videos upcoming March 16 and then LIVE FROM GODDARD on April 13. Many thanks to all, and bye from LIVE FROM THE SUN!

Art Poland: OK, bye!