From Physorg.com
Comet Lovejoy was only discovered a couple of weeks ago. It was supposed to melt as it came so close to the sun that the temperatures would hit several million degrees.
But astronomers watching live with NASA telescopes were shocked when a bright spot emerged on the sun’s other side. Lovejoy lived.
Here’s some video of the encounter:
spectacular!
The surface of the sun is at several thousand degrees not several million. Some of the tenuous flares from the surface have temperatures in the millions but they are tenuous and do not contain much heat
There are more things in heaven and earth Horatio than are dreamt of in your philosophy.
Kindest Regards
Tom Gray says:
December 16, 2011 at 8:42 pm
The surface of the sun is at several thousand degrees not several million. Some of the tenuous flares from the surface have temperatures in the millions but they are tenuous and do not contain much heat
Similarly, the solar wind through which the comet has traveled for thousands of years is of the order of 100,000 degrees hot [which is what makes it expand away from the sun at several hundred km per second, but it is so thin that there is almost no actual heat to warm anything.
Maybe the answer is that it’s not “icy” at all.
Maybe it’s “rocky”.
Maybe the EU people are right about comets.
And asteroids. And ….
I am thinking of how far we have come, and where we might go……………
Most fascinating and instructive in illustrating just how much we in fact do not know but wish we did.
Maybe they should rename the comet “baked Alaska”.
Some worry about a one or two degrees that could possibly wipe out the human race… a chunk of ice brushes with the sun and survives… enough said.
According to Al Gore is the core of the Earth that reaches several million degrees.
Tom Gray says:
December 16, 2011 at 8:42 pm
Some of the tenuous flares from the surface have temperatures in the millions but they are tenuous and do not contain much heat
============================================================
Tom, I’m not wishing to be critical, and I would expand and expound if you don’t wish, but for many, the sentence above would require an explanation before understanding is achieved.
I know ….but heat, energy, temps…I’m not much on the dynamics of the sun… c’mon man!
More movies at spaceweather.com. Check LASCO yourself here:
http://sohodata.nascom.nasa.gov/cgi-bin/soho_movie_theater
Both C2 and C3 are interesting. Select on of these and the start and end dates, Try 2011-12-15 and 2011-12-16. If you look carefully, there is a surprise. Lovejoy was not alone. Alas, his companion was not so lucky.
Very few things are as stable as water. And ice is one tough solid as most know. It can take a lot of blast. Because it does not transmit heat well. Makes an excellent bomb shelter.
At least that is the way i learned it.
Oh, and I almost forgot: Several million degrees, eh? Was that Kelvin or Celsius? ;->
Look, just for a moment, bury whatever ails ya. And just appreciate the locale. The local cosmic neighborhood. Try enjoying when and where we live.
“It was supposed to melt”
Why are we to assume it did not? Why can’t that smear that crossed my screen be dirty water (vapor?) rather then dirty ice?
Why would melting change the the orbit of a comet?
NASA release
http://science.nasa.gov/science-news/science-at-nasa/2011/16dec_cometlovejoy/
Now that was a HOT encounter…. and ‘Yes’… Coronas were involved
“Strangers in the night…. exchanging momentum..”
Fire and Ice – Robert Frost
Some say the world will end in fire,
Some say in ice.
From what I’ve tasted of desire
I hold with those that favor fire!
But if it had to perish twice,
I know enough of hate
to say that, for destruction ice
is also great
and would suffice.
Do you want fries with that?
Loved the wriggly tail on the way in…….awesome!
Tom Gray says:
Tom, I’m not wishing to be critical, and I would expand and expound if you don’t wish, but for many, the sentence above would require an explanation before understanding is achieved.
I know ….but heat, energy, temps…I’m not much on the dynamics of the sun… c’mon man!
It’s a complex subject. I usually don’t dump people into a web site but I think this will give you the basics.
http://coolcosmos.ipac.caltech.edu/cosmic_classroom/light_lessons/thermal/
Wow! Not sure why it matters, but it sure seems to. That is one tough dirty-snowball!
>>
Tom Gray says:
December 16, 2011 at 8:42 pm
Some of the tenuous flares from the surface have temperatures in the millions but they are tenuous and do not contain much heat
<<
Darn my thermodynamic training:
The classical thermodynamic definition of heat is the transfer of energy across a system boundary due to a temperature difference–from a higher temperature to a lower temperature. As heat is a transient phenomenon, it is not possible for something to contain heat.
Jim
James Sexton says:
December 16, 2011 at 9:40 pm
I know ….but heat, energy, temps…I’m not much on the dynamics of the sun… c’mon man!
The average energy of a molecule or atom is proportional to the absolute temperature. The total energy of a volume of gas [though which the comet flies] is the energy of a single atom times the number of atoms.If the density of the gas is very low, there are not many atoms so the total energy [need to heat the comet] is also very low.
What a great object lesson on the scientific method for my students–you make a prediction based on what you already know or can find out, then see if it happens. If it doesn’t, you get to try to figure out why!
Science is awesome.
Hmm… after that slingshot, where’s Lovejoy going now?
So the IPCC climastrologists were right. The sun ain’t no big deal.
Time for NASA to consider a close encounter mission with the sun? Hitch a ride on a sun-grazing comet. Now there’s a worthy technical challenge for them.
Richard111 said: “Hmm… after that slingshot, where’s Lovejoy going now?”
Off to see Lady Felsham.
What a refreshing post, nice to see some science be discussed after the barrage of political posting that have swallowed up this site since CG2. Thank you! 🙂
That is one great lesson in physics!
Wonder who now thinks such a comet would burn up steaking into OUR atmosphere? It may due to the great density of the molucules here.
Two, the radiation. E/m waves. I should not have such a hard time now explaining why the ir radiation from the surface of our eath only contributes a net of 23 W/m-2 to the atmosphere and have someone believe it, it’s true. People (climate scientists) always seem to leave the impression of this huge influence of I/R radiation just because all energy leave the earth by radiation, slightly more that 40% in the far infrared and microwave. No, just 23 W/m-2 from the surface and that is according to Trenberth own data. They just have hidden that fact so well and deep and have instilled wrong impressions.
NASA doing some real science. What’s this a back to basics expedition?
Whatever it is some good pictures. Perhaps the corona has high temperature but little heat.
>>
Richard111 says:
December 16, 2011 at 11:51 pm
Hmm… after that slingshot, where’s Lovejoy going now?
<<
Slingshot? This sounds like something from Star Trek. Lovejoy will continue on its conic-section orbit: ellipse, parabola, or hyperbola–probably ellipse. If they knew Lovejoy’s orbital parameters before it passed behind the Sun, then those parameters would remain unchanged.
Jim
That must of been one hot ride, no matter what the actual temperature was. I would put it in the VBH (very blooming hot) range.
“Now, Dasher! now, Dancer! now, Prancer and Vixen!
On, Comet! on Cupid! on, Donder and Lovejoy?!?!
To the top of old Sol! Thru the heat of the orb!
Now dash away! dash away! dash away all!”
As dry leaves that before the wild hurricane fly,
When they meet with an obstacle, mount to the sky,
So up to the Sun’s back the boulders they flew,
With the sleigh full of toys, and St. Nicholas too.
A Merry Xmas to all Watts readers
(with thanks to Clement Clarke Moore/Henry Livingston)
Craig M
The discussion about heat transfer requiring density is interesting!
Makes perfect sense by analogy with “It’s not the heat, it’s the humidity.” Water vapor makes more contact with the skin than air molecules, so it transfers more heat. But I’d never thought about it in terms of simple gas density.
Wonder if the effect is noticeable in the usual barometric variation? Does 80 degrees at 30.1 inches feel hotter than 80 degrees at 28.4 inches?
Several million degrees? Sun surface is only about 6000 C and so is the main portion of its radiation. And sun corona is too diluted to heat up anything big considerably.
Jim Masterson says:
December 17, 2011 at 2:21 am
“Slingshot? This sounds like something from Star Trek. Lovejoy will continue on its conic-section orbit: ellipse, parabola, or hyperbola–probably ellipse. If they knew Lovejoy’s orbital parameters before it passed behind the Sun, then those parameters would remain unchanged.”
I agree, what slingshot? But I noticed you said probably elliptical. And you could very well be right. Like an Oort comet. But if it’s elliptical the eccentricy would be like 0.995, maybe closer to 0.999. When I get some time I am going to calculate that with such a good measurement of it’s altitude above the surface. My main point was ‘that bugger’ is not coming back any time soon, like a thousand+ years if elliptical… if ever if not.
When I was developing a solar system simulation program years ago I had a favorite high elliptic orbit to test various integrators an I believe it was about e=0.96 with a period of something like 120 years. That certain ellipticity was special for all solved parameters of that orbit landed exact on whole numbers and that way you could tell precisely after an even number of years, you should find the body exactly at the same starting point with the same velocity vector exactly parallel to a circular orbit at that radial distance if no errors were injected by the integrator itself. But if I remember that test body’s closest approach was much higher that Lovejoy’s skimming perihelion altitude meaning much longer period.
Hoser says:
December 16, 2011 at 9:51 pm
Oh, and I almost forgot: Several million degrees, eh? Was that Kelvin or Celsius? ;->
=================================================================
Bachelors, Hoser.
Richard111 said: “Hmm… after that slingshot, where’s Lovejoy going now?”
That’s not a comet, everyone knows that’s Destiny, fueling up on our sun’s corona. Then performing a slingshot to their next Stargate Universe (SGU) adventure.. Their stellar navigation must be off-line since they didn’t realize they reached home..
For those who need a point of reference:
http://stargate.wikia.com/wiki/Destiny
just having a little fun 🙂
joshua Corning asked:
“Why would melting change the the orbit of a comet?”
Remember “orbital mechanics” and man-made satellites around earth. To stay in orbit, the mass of the satellite must maintain a velocity commensurate with it’s orbital distance from the gravity well. That is why space trash keeps falling to earth. For those orbiting objects, their mass is constant, but their velocity varies.
But if the mass of the object changes, then the orbital trajectory will also change. “Heavier” (more mass) objects require more energy to maintain their orbit than “lighter” objects.
Also, a comet may have a highly eccentric orbit, but it is still subject to the mathematics of orbital mechanics.
So, as Comet Lovejoy left a visible trail as it flew past our sun, it was probably shedding mass. Less mass in the orbital mechanics equation will mean that Lovejoy’s trajectory will be altered.
“The surface of the sun is at several thousand degrees not several million.”
That depends on whether or not CRU is handling the analysis.
How many times have you heard the phrase “we were amazed/shocked”. Just shows how litle we know about the unknown or what a bloated ego we have!
Hoser says:
December 16, 2011 at 9:51 pm
Oh, and I almost forgot: Several million degrees, eh? Was that Kelvin or Celsius? ;->
First one, then the other. 8^D
I just like the way the cols tail is buffeted by the hot flares. Makes Lovejoy emerge from the far side looking like a bottle rocket.
@ Newt Love:
“But if the mass of the object changes, then the orbital trajectory will also change.”
Trouble is NL, you are speaking of the wrong mass. You would have to change the sun’s mass since in orbits, check something like vis viva equation, is controlled by a term (M+m), M being the sun’s mass and m being the comet’s mass. Since the sun’s mass so dwarfs the comet’s, a loss of mass in the comet is going to do basically nothing (well, unmeasureable).
This comet was discovered in early December. Glad it didn’t come through our neighborhood. Not much time to activate the planetary defense shield.
Should be…..cold tail…..
Oh heck if Al can say the center of the earth is millions of the degrees then why can the sun be millions of degrees too?
“Astronomers say it probably wasn’t deadly because the comet was larger than they thought.” Really!
In spite of comet Temple-whatever being shown NOT to be a snowball but mostly rock when smashed by the large copper slug several yrs ago, these guys (clowns?) were “amazed” that Lovejoy didn’t behave like a snowball either…. so it still had to be a snowball but larger than they thought. GMAFB!
Never A Straight Answer – is it dogma or stupidity or incompetence or other?
When you’re hot, you’re hot. When you’re not, you’re not. In this case it seems to be hot and not hot at the same time. However, the videos were pretty cool.
Was 2011 the year of, “The Sun Diving Comet”?
Or, are we reserving that title for 2012?
This year we saw comets go into the corona and coronal ejections come out.
We now think that comets may perturb or destabilize magnetic fields triggering ejection.
But,
Comet Lovejoy does a spiro gyro to within a 140,000 kilomtrs of the solar surface inside! the solar corona and zips around out the otherside?
So how could the space industry use this to build something simular. Looks like we could learn something from this.
Forget the thin nebulous gases. The radiative heating must have been horrendous. An hour of such radiative heating would have seriously cracked and fissured any exposed surface. I am gobsmacked it didn’t explode. Perhaps this would be a good technique for further exploration of heat prohibitive locales. 🙂 GK
Comet Lovejoy survives it’s own version of “Global Warming”!!! ;-))
By Jim Masterson on December 17, 2011 at 2:21 am
Don’t forget John Chrichtons ‘slingshot’ manouver in ‘Farscape’!
(The greatest sci-fi tv show ever! In my opinion)
B-)
Apologies for the spelling. English is not my mothertounge.
I need to send an email to check with Bill Nye but, I’m almost sure the temperature is close to several million degrees just like the center of the earth. Bill should know since he seems to be a buddy of Al Gore.
G. Karst says:
December 17, 2011 at 8:23 am
yeah, that’s what I was just thinking. The previous posts about nebulous thin gases containing no heat seem a little irrelevent (no offence folk!) – I mean, you stand on a warm sunny day and feel radiative heat at the earths distance from the sun on your back, yes? – now, let’s move a few million miles closer to the source – what is the radiative heat energy likely to be there? At the very least also, I’d expect the comet to have come out looking rather red (like I do, after an hour in the sun! LOL)……..
The music is “Open Season” by “Stuck Mojo”.
Very ironic, (because of NASA’s flirting with the Moslems), as the lyrics are VERY un-pc toward them…
The answer to why the comet didn’t melt/vaporize is simple: No CO2.
Karst said: “…I am gobsmacked it didn’t explode….”
It is made of Kryptonite! :}
I had to turn off the sound to watch this NASA video.
What Muslim hogwash muzak has to do with the Sun and the comet?
So it melts. Where is it going to go then. It just keeps going until it freezes up again! Gee, some people of gotten the Nobel Prize for a lot less than that.
@jim Masterson
> As heat is a transient phenomenon, it is not possible for something to contain heat.
That’s misleading. Heat is energy and is measured in calories, the amount of energy needed to raise the temperature of 1 gm of water by 1 C° There is a property of mass, known as heat capacity , which refers in general to the amount of heat needed to raise the temperature of any mass by a given amount.
So the point being made about the comet passing through the plasma surrounding the Sun, is that although its temperature is over a million Kelvins, it has very little mass, so very little heat energy in the plasma to be transferred to the comet.
If the comet lingered long enough in the corona, adiabatically without any additional transfer of heat, the system would come to an equilibrium temperature, somewhere in the middle, but that would take a very long time.
I hate to rain on the parade here, but as we all know computer models and scientific consensus trump reality, therefore comet Lovejoy does not, in fact, exist.
I think it was Santa and David Suzuki looking for a new toy workshop now the North pole has made Santa homeless. “The horror”
The North Pole, once a wintery wonderland,
is no longer safe for Santa’s Workshop.
Climate change is melting the snow and ice, and the rising water is getting too close for comfort. Santa must relocate — FAST — to make sure that all the nice boys and girls still have a Happy Holiday.
You can help by buying Santa the supplies he needs to land safely in a new home.
Better yet, buy them as green gifts for friends and family to show you’re thinking about them — and the planet — this holiday season.
David Suzuki Santa’s friend.
http://www.wherewillsantalive.ca/
>>
John Day says:
December 17, 2011 at 10:59 am
That’s misleading.
<<
That’s hard to believe. It was a direct quote from my thermodynamics textbook.
>>
Heat is energy
<<
True.
>>
and is measured in calories
<<
Well, usually. Heat is energy and we can use any units for energy. The first law of thermodynamics relates the cyclic integral of heat flow TO a system with the cyclic integral of work performed BY the system. Those units can be calories, BTUs, joules, ergs, dyne-centimeters, newton-meters, kilowatt-hours, horsepower-mins, foot-pounds, foot-poundals, electron volts, or any other unit of energy.
>>
the amount of energy needed to raise the temperature of 1 gm of water by 1 C°
<<
It’s the definition of a calorie.
>>
There is a property of mass, known as heat capacity, which refers in general to the amount of heat needed to raise the temperature of any mass by a given amount.
<<
Heat capacity is not heat flow. Heat is a flow of energy.
>>
So the point being made about the comet passing through the plasma surrounding the Sun, is that although its temperature is over a million Kelvins, it has very little mass, so very little heat energy in the plasma to be transferred to the comet.
<<
You’ll notice I made no comment about this as I didn’t disagree with it.
Jim
>>
Jim Masterson says:
December 17, 2011 at 3:55 pm
we can use any units for energy
<<
My bad–it should read: any energy units for energy.
Jim
>>
Wayne says:
December 17, 2011 at 4:50 am
When I was developing a solar system simulation program years ago . . . .
<<
Interesting. I wrote a Java Applet based on a NASA solar system simulator I saw on the web. It seemed to work quite well. I should probably try your trick to see how good it really was.
Jim
Images of comet Lovejoy are still being processed. Comet Lovejoy spiro gyros its way through the solar corona then sling shots itself out of the solar corona.
Here’s http://www.spaceweather.com take on it.
QUIET SUN: Solar activity is very low. WIth no sunspots producing strong flares, the sun’s x-ray output has flatlined. Significant flares are unlikely this weekend.
SPIRAL COMET TAIL: As Comet Lovejoy recedes intact from its Dec. 16th close encounter with the sun, researchers are pondering a mystery: What made the comet’s tail wiggle so wildly in transit through the sun’s atmosphere? The effect is clear in this sequence of extreme UV images recorded by NASA’s STEREO-B spacecraft:
“Why the wiggles?” wonders Karl Battams of the Naval Research Lab. “We’re not sure. There might be some kind of helical motion going on. Perhaps we’re seeing material in the tail magnetically ‘clinging’ to coronal loops and moving with them. [Coronal loops are huge loops of magnetism that emerge from the sun’s surface and thread the sun’s atmosphere.] There are other possibilities too, and we will certainly investigate those!”
Battams notes that these images can be combined with similar images from STEREO-A on the other side of the sun to produce a three dimensional picture. “When we pair these together, and throw in the SDO images too, we should be able to get an incredibly unique 3-D picture of how this comet is reacting the the intense coronal heat and magnetic loops. We are going to learn a lot.”
http://www.spaceweather.com/images2011/18dec11/EUVI_B_lovejoy.gif
How many g’s would comet Lovejoy be pulling in that slingshot around the sun….?
I would be guessing that a loosely packed snow ball or globule of liquid would be torn apart… So Lovejoy must be quite solid and very heat resilient….. The radiative energy it was subjected to would have been awesome. So quite obviously a solid chunk of rock and or metals
….. as for the wriggly tail…. Interaction with Birkleland currents?
>>
J.H. says:
December 19, 2011 at 11:02 pm
How many g’s would comet Lovejoy be pulling in that slingshot around the sun….?
<<
Again, the “slingshot” term is a misnomer. The comet is simply following a very elliptical orbit around the Sun. The g’s (acceleration) would be pretty high–probably in the hundreds. As the comet is in free-fall, those g’s would not be felt. However, tidal forces may become significant. High tidal forces can tear a body apart.
Jim
That Comet Lovejoy?
Yeah thats the 505 from Downtown….yeah, you want the 506, that’ll get you home…no man if you missed it, you’ll have to wait another hour, then the 506 will swing by again, better be ready, it don’t stay long.
I was in that Hale-Bopp fender bender, when it spun outa control, yeah that sucked, lucky for me I was at the back. So no blood no foul.
Think they shut that line down, who takes the Bopp anywhere these days, am I right,…sure I am, forget about it.
You got a concession card? Me too, I was catchin’ that eco friendly unit – Electric thing – Russian,…ELENIN, yeah thats it. Ellie Nin…
Whats the big deal right? Damn thing swung by once, never seen it again since,…so much for solar. All the tinfoil hat kids cryin’ foul, ‘its dangerous,…its dangerous, it’ll hit something’,…I wish it had hit something, mighta been worth the ticket price.
There’s twelve bucks i’ll never see again.
Hear about that Nibiru,…yeah, its the Number Ten, ain’t never seen it, no one has, know why? Its Hydrogen, no infrastructure, can’t refuel. So much for that.
Hey this is my unit, see ya around kid.
Carla says:
December 18, 2011 at 10:13 am
..Battams notes that these images can be combined with similar images from STEREO-A on the other side of the sun to produce a three dimensional picture. “When we pair these together, and throw in the SDO images too, we should be able to get an incredibly unique 3-D picture of how this comet is reacting the the intense coronal heat and magnetic loops. We are going to learn a lot.” ..
~
Has anyone seen tha new movie? ..
I include in the comet lovejoy time line the launches of the two Mars missions. One Russian (carrying a Chinese payload) called Phobos Grunt and the US lead mission. The Russians were planning a return trip. That’s important. .. .. Scoop some dirt from Mar’s moon Phobos and make a return trip. Well we all know now that the Russians were unable to make communication? with Phobos Grunt (launched Nov. 9, 2011) Some Australian location was able briefly. But for the most part now its death watch for the Grunt.
Here’s an update on comet Lovejoy from http://www.space.com
Spectacular Photos: Astronaut Sees Dazzling Comet From Space Stationby Tariq Malik, SPACE.com Managing EditorDate: 22 December 2011 Time: 04:22 PM ET
An astronaut living in space has captured an unprecedented view of a comet from orbit in a jaw-dropping set of photos taken over a nighttime Earth.
The amazing images show comet Lovejoy, which survived a trip through the sun’s atmosphere last week. They were snapped by veteran NASA astronaut Daniel Burbank, who is currently commander of the International Space Station.
And even for a seasoned spaceflyer, the sight was amazing to behold..
..Comet Lovejoy was discovered on Nov. 27 by Australian amateur astronomer Terry Lovejoy. The comet was estimated to be about 660 feet (200 meters) wide, larger than two football fields, when it was first seen..
..The comet zoomed within 87,000 miles (140,000 kilometers) of the sun’s surface, and many astronomers predicted it would not survive such a close solar encounter. But comet Lovejoy defied the odds and re-emerged on the other side of the sun. The event stunned astronomers and was captured by several sun-watching observatories in space..
http://www.space.com/14031-spectacular-comet-photo-astronaut-space.html
Are we going to lose site of comet Lovejoy around the same time line as the Grunt falls to Earth in January?
The Naval Research Labratory has page dedicated to sun grazing comets. They have been covering comet Lovejoy of course..
Here’s a description and video that’s is pretty far out and one I have not seen before. Kinda like the comet does this tail loss thing as a second part of its stage..
But a great analysis and video:
“”..This is the SECCHI COR-1 (inner coronagraph) image on the STEREO-B satellite. From the perspective of STEREO-B, the comet moved diagonally across the face of the Sun, looped around it, and re-emerged from around the back. The comet is obvious to see as it enters the camera in the lower right. We lose sight of the head of the comet at ~2300UT as it disappears behind the occulting disk. (We superimposed a Sun image on the movie — this camera doesn’t actually see that.) Then at around 0130UT we see the bright tail of the comet appear again in the upper-left of the image and continue to move out. Here’s the fun part: this is not the comet itself! Keep watching, and at ~0530UT you’ll see the comet — minus a tail! — emerge on the right hand side of the central disk and move towards the lower-right of the image, finally exiting at ~10:45UT.
So if the comet re-emerges on the right without its tail, does that mean the bright thing that flew out of the top-left of the image is its tail?? Absolutely! I summarize the situation here. What we’re seeing is the comet streaming into our field of view with a vast cloud of dust and ice trailing in its wake. The comet reaches the Sun, loops sharply around it, and head out around the back of the Sun. But the tail material we see has already left the comet and is just going to carry on in a straight line from the time it was ejected, while at the same time be pushed away from the Sun by the radiation pressure from the Sun itself. So we’re actually seeing the tail material sweeping out towards us, while the comet races off to do its own thing.
OK, why does Lovejoy not have a tail after it reappears? How did it get torn off? Well it didn’t actually get “torn off”, as it was never physically connected to begin with, but what likely happened was that the dust and ice produced by the comet was no longer able to follow the comet in its path as the relatively dense and incredibly hot solar corona “captured”..””
http://sungrazer.nrl.navy.mil/images/lovejoy/lovejoy_20111215b_cor1.mov
http://sungrazer.nrl.navy.mil/index.php?p=news/birthday_comet#bottom
..
After viewing a couple comet Lovejoy videos ..
Seeing it ping pong its way through field loops in the suns corona..
This next question posed by a Russian scientist seems reasonable..
Proceedings of the International Astronomical Union
01 August 2010
Copyright © International Astronomical Union 2011
DOI: 10.1017/S1743921311015584
Published online: 26 August 2011
How reliable are observations of solar magnetic fields? Comparison of full-disk measurements in different spectral lines and calibration issues of space missions SOHO, Hinode, and SDO
Mikhail Demidov
Abstract
An urgent problem in modern solar physics, which is not completely solved up to now, is to obtain realistic magnetic field strength values from parameters measured magnetographs or Stokes-meter instruments. One of the important tools on this way is a comparison of observations made in different spectral lines with the same or with the different telescopes. This issue is an actual task in the analysis of the new data sets provided by the space missions SOHO and Hinode, which measurements are available for several years already, and SDO, which data appeared recently. The main aim of this study is a cross-comparison of magnetic field observations made in different spectral lines used on the above mentioned space observatories: