I find fault with generally accepted comet theory. The current theory goes something like this.
Comets are dirty snowballs which occasionally pass through our solar system. As they approach the sun, they go through a transformation as they move from the so-called inactive zone, to the active zone. The active zone is where they begin to display comet like appearance. The dirty snowball begins melting and outgassing a percentage of its mass. It develops a fog like shroud called a coma which is much larger than the comet itself. Sometimes much bigger than the earth itself. Even though the comet nucleus is only one to six miles long. The closer it gets to the sun the brighter it glows and the more material it outgasses. The solar wind which blows from the sun at speeds of 200 to 600 kilometers per hour blow much of the coma and outgassed material behind the comet in two tails. One is called the dust tail which falls behind the comets movement around the sun and leave a trail of debris behind. The other tail is called the Ion Tail and it allways points away from the sun. The Ion tail can be many millions of miles beyond the comet by the solar wind. But the Ion tail is allways pointing away from the sun and may actually be in front of the comets path as it exits its close call with the sun.

I have several problems with this theory. First of all as the comet gets close to the sun the tail moves around much like the indicator shadow on a sun dial. Looking at the pictures of the comet you can see what appears to be material flowing away from the comet and downstream from the sun. But at 10 million kilometers long, or 4 million miles long the far end of the tail must accelerate sideways across the apparent solar wind to maintain its position in time with the comet. Kind of like the speed of a wheel at its hub versus the speed of the wheel at the tire. The further out you go the faster the material making up the wheel must travel. In the case of a comet it moves relatively slowly, but the material streaming off the comet should maintain the same speed around the sun as the comet. But it obviously must speed up. But there is nothing to accelerate it across the apparent direction of the solar wind. If you have ever seen tracer rounds being shot at night you know that if you move the gun to the left or right while it is firing the path of the bullets appears to be an arc. Same thing is apparent if you squirt a water hose in your back yard. Even though the water mollecules are moving in a straight line, if you move the nozzle to the left or rignt the stream appears to be an arc. Even if the molecules from the comet are accelerated at 100% of the speed of the solar wind, (which is unlikely) it would take 5 hours for the ionizing material to make it to from the comet to the end of the tail. But it does not. It looks straight as an arrow. I have some very against the mainstream theories about what can cause this apparition. But none of them are perfect either. The Ion tail on the comet should look like an arc. Can anybody provide a reasonable explanation? I don't want to expose my theories until I have tried all other logical expanations.

Thanks, Dan Apted. dapted@customcpu.com

<a name="20020326.1:3"> page 20020326.1:3 aka COMET's tail
On 2002-03-25 23:42, dapted wrote: To: 7 CABAN 15 CUMKU
8: March 26, 2002 Log on for posible `bait
7: later if I can thin UP
6: some THIN
5: reminds me of
4: Shadow [spokes]
3: in the rings of Saturn
2: thats all I have at
1: "THIS TIME" 1:34 A.M. pst

As I posted a little while ago, there is another fellow named James McCanney who thinks there's more to comets than the dirty snowballs we currently believe them to be. DStahl kindly provided a link to McCanney's site where you can also find versions of his paper. I'm interested in this line of thought too...but it all seems like an exercise in futility until we get better images and analysis of comet nucleii.

<font size=-1>[ This Message was edited by: Comixx on 2002-03-26 06:15 ]</font>

We have some good closeups of a couple of comet nuclei. Halley in particular. Deep Impact will actually penetrate a comet! I have a few friends working on that spacecraft.

I have a number of friends working on the Rosetta program, which is now in it's final testing before launch.

http://spdext.estec.esa.nl/content/doc/e5/2277_.htm

http://www.sci.esa.int/content/news/...=398&oid=29695

Why do I have the feeling that even after a probe is landed on a comet and performs direct measurements that the "Electric Comet" people will call it big cover-up??

The Langmuir Probe on board will be very sensitive to electric fields.

I don't buy the electric comet theory either. My theory has to do with light pillars caused by ice cystals, or some other frozen crystalized gas co-orbiting with the comet and reflecting and refracting light to the observer. This effect allows the near end and the far end of a multi-million mile tail to be the same (approximately) distance from the viewer and thus appear straight. Here are some links.
<a href=http://www.netppl.fi/~jarmom/haloguid/halogal.htm> Halos and Pillars</a>
<a href=http://www.genesismission.org/product/genesis_kids/ropingrainbows/ropingrainbows.html> Simplest explanation of light pillars </a>

<a href=http://www.weather-photography.com/Guest/photos.html> sun pillars and halos</a>

More sun pillar photos

another good sun pillar


<a href=http://www.meteoros.de/englisch/ee08e.htm> Pillar explanation</a>
Better Pillar explanation

One more explanation

If there are frozen crystals in co-orbit with comets, and if those crystals can be aligned by balance between solar gravity as accelerator and solar wind as drag then a pillar could be formed. Said pillar explains how a comet tail can look so long and straight when by all orbial math it should be an arc.

Dan

Sure. In the two examples that you gave, tracer bullets, and water streams, the arcs that you see when you move the gun or hose sideways is in part a result of the fact that you start your sideways movement from a stand still. In other words, you are accelerating the gun or hose to the right or left.

Acceleration produces arcs, as the familiar gravity parabolas attest. If you were to mount a gun on a train and fire the tracers as the train was moving at a constant speed, the path of the tracers would appear to be more like a straight line (except for their fall due to gravity--but I'm sure you mean the sideways motion). That's a result of the combination of the two essentially linear motions.

For the comet, its motion is not strictly constant, but it is close enough for the time that we observe it.

Sorry to disagree with you but the tail starts out almost directly behind the comet as it approaches the sun from way out in space. The tail is short, and it movement can't be detected, then as it nears the sun it accelerates its swing as it goes around the sun. Once the comet has gone most of the way around it starts its outbound trajectory the distant end is now well in advance of the comet and the swing is much slower. Watch a sprinkler on a hayfield. In just a few seconds of travel time it still looks like an arc. If the ion emitting material is moving at 300 to 400 KPH, which is pretty close to 100% of the speed of the solar wind (I doubt it could even come close to that, and the comet tail is 150 million kilometers long and straight as an arrow.

Here is a quote from <a href=http://tweens.indiatimes.com/twt_pg/tweencyclopedia/universe/deepimpact.htm> a sposedly knowledgable source</a>

"The solar wind, which consists of high-speed atomic nuclei, protons, and electrons, sweeps cometary gases away from the Sun, producing a straight tail up to 93 million miles (150 million kilometres) in length. A second tail consisting of dust particles may also appear. This dust tail is shorter and more curved than the gas tail. A comet tail always points away from the Sun because of the force exerted by the solar wind and the Sun's radiation on the cometary material. Therefore, when a comet travels away from the Sun, its tail or tails are always in front of it. Some comets have been observed to develop as many as nine tails."

If you believe this then the material from the comet at 100% of the speed of solar wind will take 20 days to get there. A comets tail will have turned a long way around the sun in 20 days time.

In addition you have to find a way to believe that any ionizing material can be accelerated to that speed in the first place. Thus at best figure 200 days for the material to make it to the end at a still unbelievable speed of 10% of the speed of the solar wind. When they dump water from the space shuttle they have to aim it straight down toward the earth in order to keep it from becoming a problem. If solar wind would carry it away they would not have to do that. Here is a page with an explanation and a photograph of a water dump by the space shuttle
<a href=http://www.eclipsetours.com/sat/shuttle.html> Paul Maley's page about the shuttle activites. </a>

This proves ice crystals can exist in space, and it shows what happens to matter when you jettison it to a different orbit. In this case it is jettisoned to a lower orbit, which has less distance to travel, thus the arc curves ahead of the shuttle. It hasn't really sped up, it just has to travel less distance than the shuttle as it moves around the planet. Also note that the solar wind did not blow it away.

Thanks I enjoyed reading those pages. I wish they could launch earlier though. I may not make it to 2011.

Dan

Dan,
I read with interest your post.
I edited my post when I realized you wanted an answer to why there is no curvature in the ion tail. (apparently you realize the dust tail does show apparent curvature)

First, the origin of the tails are different:
The ion tail originates from the interaction of a highly charged solar WIND ( and associated solar magnetic field) with the charged gas that surrounds the cometary necleus. The result is an emission spectrum from the recombination of charged particles with electrons.

The dust tail on the other hand arises from solar pressure, (i.e. solar E.M. RADIATION)that forces molecules off the surface of the comet. It is observable by reflection.

Now to correct a error. 1st, the solar WIND (that causes the ion tail) travels at a stagering 400 or so Kilometers PER SECOND, not per hour as you gave in your post. This is about a million miles per hour! And is over 100 time as fast as the orbital velocity of, say Comet Hale Bopp at its FASTEST point (at perihelion).

With such a high tail velocity we would not expect the curvature to be perceptible. It would be like (in your garden hose analogy) moving the head of the nossel very slowly with respect to the speed of the water coming out - there would be very little arching.
In an equal amount of time that the comet moved 100 km. the tail would have traveled over 10000 km. A little trig. would show that this is less than 1/2 degree of arc.

For an ion tail to have gone out 4 million miles only takes 4 hours and the comet has only moved 40 k miles. (Again, 1/2 degree curvature). Even the width of the tail would be greater than 40 k miles.
(Also, note that the visible length of the tail is limited by the lifetime of ionic recombination of gas and solar wind.)

I believe that's the solution to your problem.

G^2






<font size=-1>[ This Message was edited by: Gsquare on 2002-03-26 22:56 ]</font>

Thanks for the explanation, but I used 200kps, Kilometers per second. using your 400kps x 60 seconds yeilds 24,000 kilometers per minute x60 yeilds 1,440,000 per hour. So at 100% efficiency assuming no loss of speed due to the comet and its coma being in the way of the solar wind, it would take 100 hours to go 144 million kilometers. The article above quoted the Ion tail as being 150 million kilometers long.

How much angular movement is there in the tail in 4 days? use the perihelium swing for this debate.

I am not good at trig.

<font size=-1>[ This Message was edited by: dapted on 2002-03-26 23:13 ]</font>

3:28 A.M.? 20020327
On 2002-03-26 11:39, dapted wrote:

<a href=http://www.netppl.fi/~jarmom/haloguid/halogal.htm> Halos and Pillars</a>
<a href=http://www.genesismission.org/product/genesis_kids/ropingrainbows/ropingrainbows.html> Simplest explanation of light pillars </a>

<a href=http://www.weather-photography.com/Guest/photos.html> sun pillars and halos</a>

More sun pillar photos

another good sun pillar


<a href=http://www.meteoros.de/englisch/ee08e.htm> Pillar explanation</a>
Better Pillar explanation

One more explanation

3:29 A.M. Yep

No matter what time frame you use, the relative speeds (and thus relative distances)stays the same, so the arc is the same.

In any time period the ratio of distance covered by the comet vs. radial distance covered by the tail stays the same, (assuming the period isn't so long that the orbital speed has changed significantly). Thus using tangent, we see that the amount of angular change from the front to the rear of the tail is the same, about 1/2 degree.

The amount of arching is based on the relative speeds (solar wind vs. orbital speed), not the time frame.

The dust tail,however, is blown off at lower speeds by radiation pressure and thus arching is much more apparent.
Hope that's more understandable.

G^2



<font size=-1>[ This Message was edited by: Gsquare on 2002-03-27 10:19 ]</font>

<font size=-1>[ This Message was edited by: Gsquare on 2002-03-27 09:16 ]</font>

Gsquare beat me to it. In a nutshell, the difference between the speed of the solar wind compared to that of the comet is just too great for any ion tail arcing(sp?) to be perceptible. There's also the vantage point to take into account here. Pretty much always, we see the comet sideways from the Earth(usually, we see comets as they're traveling towards the sun (anyway, in my own relatively short(20 years) comet-gazing experience)). An arc, looking at it sideways, looks like a straight line. So even if a comet would have a perceptible arc, we wouldn't see it.

Thanks G I appreciate the effort but I guess I must be daft. Anytime you see a water discharge from the shuttle, they launch it into a lower orbit. When they do this the water appears to arc forward of the shuttle. Orbital mechanics says it should as it now has less distance to circle the globe but it is still moving at the same forward velocity as it had when it was on board the shuttle. If they were to launch it into a higher orbit, away from the earth it should arc backwards relative to the shuttle, again because it now has a longer distance to go to get around the globe, but it is still moving at the speed of a lower orbit.

So then go back to the comet, it is launching material which is, or will be ionizing into a much higher orbit, but the forward velocity has had no energy input to make it move at the faster speed required to orbit the sun in the same period of time as the comet. 150 million killometers is a hugely long ways. Assuming the solar wind is responsible for putting it up that fast, what is the mechanism to make the orbital speed come up?
Dan

When the material is ionized it becomes a plasma, i.e. a mixture of electrons and positively charged nuclei and molecules. These solar wind plasma also consists of charged particles travelling at high speeds (high energies). Because of the electric fields of the particles, they can interact at much further distances than if they were neutral, so collisions between the solar wind plasma and the comet plasma transfer energy to the comet particles and accelerate them to the solar wind velocity. This is called "ion pickup".

http://www.agu.org/pubs/abs/nja/97JA...97JA02667.html

The shuttle takes an hour and a half to go around the Earth, comets may take hundreds or thousands of years to go around the Sun. Their angular velocity is a lot less.

Not buying it. You are most probably correct, but I dont see it. Put another way, this Ion tail, if it exists, is the only thing in the Universe that makes a straight line, other than rays which are an illusion caused by sunlight moving through a cloud or other object which is not straight at all. To my eye, and pea sized brain, the only explanation of the Ion tail is that the Ion tail is an effect of light ie photons exciting small amounts of matter which must surround the comet, I just can't make the leap to any matter being instantly accelerated to 400kps. I can imagine the effect moving that fast. Kind of like the Aurora Borealis. The Ionic effect moves at those speeds. But the underlying matter which emits the photons is essentially upper atmosphere and is sitting still, relative to the solar winds which ignite the event.

It was first measured directly by the spacecraft ICE/ISEE-3 on September 11, 1985. (I built part of the instumentation.)

http://www.sp.ph.ic.ac.uk/~balogh/isee3.htm

Photoionization is in fact a key factor in producing plasma from the comet source material.

It isn't instant.

The solar wind doesn't directly excite aurora, solar wind particles are trapped in the magnetosphere and acceleration processes occur which dump electrons into the upper atmosphere. These electrons follow magnetic field lines, not straight lines.




<font size=-1>[ This Message was edited by: Karl on 2002-03-28 10:34 ]</font>

There is a distinct difference between "straight" and "apparently straight". As has been pointed out, the curvature of the ion tail is approximately 1/2 degree. This is the maximum arc that can be observed (and only if the orbit of the comet is such that its path is perpendicular to our line of sight). If the orbit is such that it is moving directly across our line of sight, it will appear to be straight (no matter how curved it "really" is.

_________________
When all is said and done - sit down and shut up!

<font size=-1>[ This Message was edited by: Kaptain K on 2002-03-28 11:17 ]</font>

Thanks for the response, dapted, but your shuttle discharge example is not at all analogous to the comet. In fact, it's the inverse.
In the shuttle example the only reason you observe the arching is because the forward velocity is SO MUCH GREATER than the outward (radial) velocity of the water. In a comet its just the opposite. (GOW alluded to this).

TO MAKE the shuttle ANALOGOUS TO THE COMET:
the shuttle would need to slow down to say 10 mph (and still stay in orbit) AND the water would have to be spewed out at over 1000 mph to a higher orbit; then you would see no arching (provided the water dissapted after it gets to that height as does an ion tail). Only then can it be analogous to the comet since the ORBITAL velocity would only be 1/100 th the RADIAL velocity of the water. In a comet it's the orbital velocity that is very low relative to the HIGH radial velocity of the jet of ion material.
Thus, no mechanism is needed to make the orbital speed of the tail increase so as to keep it straight. Essentially, an ion particle from the head reaches the end of the tail so fast (before dissapation) that there is very little ORBITAL distance traveled to make curvature detectable.

G^2

P.S. Note: Even in DUST tails where the curvature IS significant enough to be detected,(as mentioned by Ranma & Kaptain K), the curvature may be hidden by an unfortunate line of sight wrt earth; a factor which will vary depending upon relative inclination of orbits, longitudes, etc.




<font size=-1>[ This Message was edited by: Gsquare on 2002-03-28 13:23 ]</font>

Correct I see that point, but I have looked at thousands of photographs of comets and they appear to run the gammut as far as vantage point. Some even seem to have an Ion tail that points both toward the sun and away from it. And none of them show any sort of Arc. Even a 1/4 degree of arc would be perceptable. Plus there is the fact that the Ion tail usually seems to be where a shadow would be if there were one.

I know there is a limit to argument but I haven't reached my limit yet. Assume the comet at its closet approach to the sun is 1 au, approximately 150 million kilometers. Assume it's tail is 1 au as well, another 150 million kilometers. The top of the arc or 1/4 way around the sun give or take a little is a path of approximately 23,500 million kilometers. The path taken by the tip of the tail is closer to 47,000 million miles. Thus to cover the different distances in the same amount of time requires the tip to be moving approximately twice as fast as the base of the tail in Oribtal velocity. Since nothing accelerated the orbital velocity as the material made it's way out to the end of the tail, orbital velocity being perpendicular to the solar wind, the tail should have a significant arc. It should look like a swirl of an arm on a galaxy for crying out loud. Yes it would look straight or nearly so if viewed from the same plane, but deep space 1 was definately in multiple different positions. Still no arc is visible. The arc has nothing to do with the speed differential between the orbital speed of the comet and the time it speed of the matter getting to the end. even if it is instantaneous the arc is evident. You can plot it with a piece of graph paper and make it simultaneous. The matter in the higher orbit has to fall behind. The arc is totaly dependent on the difference in orbital speed between the lower orbit of the comet and the higher orbit of the matter at the tip of the tail. Only if the tip of the tail accelerates to double the orbital speed of the comet can it appear to be a straight line.

Thus my insistance that the matter which is being ionized must be there well before the event which causes it to plasma. An unseen thin cloud of material waiting for the shadow of the coma to eiter begin the plasma event, or perhaps maybe it just takes the shadow for the event to be seen, an ambient lighting kind of thing, or the one I like best a light pillar caused by the soft glow of the coma making it appear as if the ion tail exists when it doesn't. What ever the mechanism, I dont buy matter being accelerated out the tail producing the apparent tail apparition.

I am too old and stubborn to give in. Probably too dumb too! <grin> No need to get mad, I know I am an exasperating fool! I can live with it, hopefully you can too.

And that is exactly what you should do. Find a real photo, and get the actual parameters, and plot the graph. How does it compare to the photo?

If the ion tail doesn't exist, what were all of those spacecraft measuring?

Am I the only one or has anyone else noticed
... that every time you anwer an objection the objection changes?
I'm beginning to realize this is one of those cases of 'My mind is made up so don't bother me with the facts'.

Nice graphics Karl.
G^2

By the way,Karl, you may be aware of the recent discovery of a third tail, a neutral Sodium tail, in Hale Bopp, which places it in about the same position as the 'hydrogen envelope' in your graph. Not sure of the origin - It reminds me of the moon's sodium 'trail'. Any ideas?


<font size=-1>[ This Message was edited by: Gsquare on 2002-03-29 09:10 ]</font>

Haven't yet found the graphic I'm looking for, that shows the actual angle of the solar wind w.r.t. the sun position vector. Due to the garden hose effect the ion tail isn't directly out from the sun.

http://space.rice.edu/IMAGE/livefrom/sunearth.html

Even though the energy flux in the solar wind is far less intense than sunlight, it is important because charged particles respond to the electric and magnetic fields in the solar wind. Consider a comet - Figure 4 shows Comet Hale-Bopp from 1997. The brightest tail of the comet is the dust tail. The yellowish dust tail points away from the Sun because the pressure of sunlight bouncing off its dust particles. It curves slowly because the dust particles have a significant mass. The other comet tail is the ion tail - here the blue tail seen above the dust tail. This tail is caused by ionized particles being pushed away from the sun not by sunlight but by the pressure of the solar wind. The comet's neutral atmosphere, the coma, is ionized by sunlight (the neutral atoms are stripped of one or more electrons by absorbing energetic particles of light, or photons). The coma is also ionized by electron impact - electrons in the solar wind striking the comet's atoms or molecules, knocking off additional electrons in the process and leaving the initial atom or molecule as a positively charged ion. The resulting ions and electrons are "picked up" by the solar wind and join with the flow, which also points away from the Sun but at a slightly different angle. The blue color is caused by sunlight scattering off of OH+ ions.




Yeah, I heard about it, but haven't read anything in detail about it. Been up to my eyeballs for the past four months getting an instrument delivered and am just now coming up for air.

Edit to fix characters in quote.

<font size=-1>[ This Message was edited by: Karl on 2002-03-29 10:24 ]</font>

About time, welcome back. You may be the most un-newbie newbie we got.