# Talk:Magnetosphere

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## Comment on page name

This page should be called Earth's Magnetosphere. Previous page correctly (prior to Jan 1, 2006) noted that Earth is not the only planet with a magnetosphere. Content from previous page that defined a magnetosphere in general should link to Earth's Magnetosphere.

I am tempted to agree - the Earth is far from the only magnetosphere we know of and that point should be made clear. Many of the details of the terrestrial magnetosphere are either not strictly true or else plain wrong when you replace the world "terrestrial" with, say, the magnetosphere of Jupiter or a pulsar. DanielWent (talk) 12:22, 6 July 2010 (UTC)

What is the current state of the the magnetosphere, isn't it decaying? At what rate? How often do the poles reverse?

The magnetic field does appear to be decaying (possibly in preparation for a reversal though, without having observed one before, nobody is completely sure) and past reversals seem to have occurred randomly. Sometimes they are tens of millions of years apart, sometimes merely tens of thousands. Although these reversals will change the direction of the magnetospheric field (and, with it, the direction of the ring current and the solar wind field polarity for which magnetospheric activity peaks) nobody has actually observed the "space environment" effects of a reversal before - or spent much time modelling them theoretically - so it's probably best to keep discussion of them to the magnetic field page for now. —Preceding unsigned comment added by 129.31.247.154 DanielWent (talk) 12:22, 6 July 2010 (UTC)

## MSPF

There are several references to seeing the MSPF section or page. This doesn't exist on wikipedia, nor is it found through exhaustive use of Google. Due to the level of experience and expertise of the originator DavidStern, I am fairly confident that this copy is valid for Wikipedia use. I've added a request on his Talk Page for the Magnetic Storms and Plasma Flows section to be included.

Xaminmo 15:16, 13 October 2006 (UTC)

## Velikovsky Prediction

I have found many claims on the internet that essentially say:

The Earth's magnetosphere was predicted by controversial author, Immanuel Velikovsky in a letter dated 5 Dec 1956 to Prof. Harry H. Hess in a memorandum on "Tests and Measurements Proposed for Inclusion in the Program of the International Geophysical Year". Velikovsky wrote:
"Measurement of the strength of the terrestrial magnetic field above the upper layers of the ionosphere. It is accepted that the terrestrial magnetic field — about one-quarter of a Gauss at the surface of the earth — decreases with the distance from the ground; yet the possibility should not be discounted that the magnetic field above the ionosphere is stronger than at the earth’s surface."[1]

How does this constitute a "prediction" of Earth's magnetosphere? I don't see the connection. If anyone can provide the connection, please contribute. I have found a discussion of this on Google Groups [2]. I don't think the issuse is settled enough to warrant its inclusion in a encyclopedia article. I have added the link to the Google Groups discussion to the Velikovsky Wiki page.

I think it's probably a valid prediction of the (observationally verified) fact that the Earth's magnetic field extends out into space but this on its own does not constitute a prediction of the magnetosphere. One could easily imagine (in the absence of the interplanetary magnetic field and solar wind) a terrestrial magnetic field that extends indefinitely out into space (decreasing in strength with distance from the ground) without ever forming a magnetosphere. —Preceding unsigned comment added by 129.31.247.154 (talk) 18:24, 5 July 2010 (UTC)

## Comment to author who cut-and-pasted a web page here in January 2006

Please allow the Wiki community to help. There are some very obvious problems in the current page. For example, the first sentence has two glaring errors:

"The magnetosphere of Earth is the space region whose processes are shaped by the Earth's magnetism ...". The errors are (1) the use of "shape" is inappropriate because a process does not have a shape; "determined" would be more appropriate, but the entire sentence should be rewritten, and (2) magnetospheric processes would not exist without the solar wind.

The above may no longer apply unless it is reverted.

## Coining of the term "magnetosphere"

The current sentence about the coining of the term magnetospehre reads: "The name was suggested by Thomas Gold in 1959, as an upwards extension of the lower part of Earth's atmosphere ...". I don't think this makes sense as it does not make clear if the magnetosphere is part of the atmosphere. I think it would be better to refer to how the region differs physically as in James Van Allen's bio [3] "In 1959 Thomas Gold suggested the term 'magnetosphere' for the region around the earth in which the geomagnetic field has a controlling influence on the motion of charged particles and the term 'magnetospheric physics' was widely adopted. Magnetosphere joined the already established list of 'spheres' -- atmosphere, ionosphere, mesosphere, thermosphere, etc. -- as a geophysical term. "

Sounds great, be bold and go for it, you seem like you're interested in making this artilce better, which is great. --Matthew 15:31, 22 February 2006 (UTC)

## merger proposal

I suggested a merger of Magnetic tail. It seem to be such a related concept and (as of now) such a stubby page that it could just be integrated here. Thoughts? --Chaser T 23:19, 6 June 2006 (UTC)

Great idea. I probably should have just done that in the first place. --S.O.T.A. 23:30, 6 June 2006 (UTC)

## Inverse cube(major error)

This page says: "The dipole field has an intensity of about 30,000-60,000 nanoteslas (nT) at the Earth's surface, and its intensity diminishes like the inverse of the cube of the distance, i.e. at a distance of R Earth radii it only amounts to 1/R³ of the surface field in the same direction."

Why do they say cube? I'm pretty sure it should be the inverse square of distance not cube.

I feel like the author is either correct and are not being clear about what is being measured, or they are wrong.

This is a pretty major error, so I'll probably ask people who can verify 100% on monday and change it then, but if the originator of this claim would like to provide an explanation before then I would appreciate one.

As evidence as to why I believe the article to be incorrect, Look at the wikipedia article on magnetic fields.

It has the following equation for magnetic field strength:

$d\mathbf{B} = \frac{\mu_0}{4\pi} \frac{I d\mathbf{l} \times \mathbf{\hat r}}{r^2}$

It clearly shows the field strength varying as the inverse square of the radius not the cube. (Look at the term on the bottom) So unless magnetospheric field strength seriously deviates from an ideal magnetic field, there is a major problem here. —Preceding unsigned comment added by 128.97.68.15 (talk) 21:47, 14 December 2007 (UTC)

I think I was just confused, I retract my comment, it should be cube. —Preceding unsigned comment added by 128.97.68.15 (talk) 22:17, 14 December 2007 (UTC)

## CNN said "Mercury is the only planet in the solar system other than Earth to have a magnetosphere"

CNN said "Mercury is the only planet in the solar system other than Earth to have a magnetosphere" in an article from yesterday: http://edition.cnn.com/2008/TECH/space/01/30/mercury.messenger.ap/index.html . Is that true and wikipedia is wrong?, because according to the wikipedia article: "Earth is surrounded by a magnetosphere, as are the magnetized planets Jupiter, Saturn, Uranus and Neptune. Mercury and Jupiter's moon Ganymede are magnetized, but too weakly to trap plasma". Mi intention is not to start a controversy, I just wish someone could clarify this for me because I feel confused. Thanks. --Dhcp 15:50, 31 January 2008 (UTC)

The CNN article is wrong in this case - many planets (as listed in the wikipedia article) have magnetospheres. PhySusie (talk) 16:01, 31 January 2008 (UTC)
Actually that's an AP story from an unknown source. The unknown source might have written from yesterday's MESSENGER press release [4] which compared Mercury's and Earth's field, and which mentioned a few other planets. -- SEWilco (talk) 16:08, 31 January 2008 (UTC)
Both CNN and Wikipedia were wrong. CNN was wrong because several planets besides Mercury and Earth have magnetospheres. Wikipedia was wrong because MESSENGER has shown that Mercury's magnetospheres does trap significant densities of solar wind plasma.[5] I have corrected our lead accordingly. Kaldari (talk) 03:23, 2 February 2008 (UTC)

## Magnetic Tail section errors

The section about "magnetic tail" attempts to describe the magnetotails of magnetized planets. However it confuses the plasmaspheric plume, formerly referred to as the plasmaspheric tail, with the magnetotail and offers a picture of the plasmasphere produced by the Extreme Ultraviolet instrument on the IMAGE spacecraft. I have edited the text to more correctly describe the magnetotail and at least attempted to mark the graphic for removal. The plasmasphere is described elsewhere in Wikipedia. If you want more of a description, visit my web pages at http://plasmasphere.nasa.gov.

Galladl (talk) 19:40, 15 August 2008 (UTC)

## Question about the opening paragraph

It is written in the opening that "Jupiter's moon Ganymede is magnetized, but too weakly to trap solar wind plasma." However, as Ganymede will never ever enter the solar wind, I wonder why this has been written down. Indeed, a ring current signature was found by Williams et al. (1997) "Trapped electrons in Ganymede's magnetic field, Geophys. Res. Lett. 24, 2953-2956". So I think this comment should be scrapped.--Tusenfem (talk) 13:33, 12 September 2008 (UTC)

Also, one may consider a line about the unmagnetized planets Venus and Mars, which have a so called "induced magnetosphere" created by the draped magnetic field of the solar wind around the planet.--Tusenfem (talk) 13:37, 12 September 2008 (UTC)

I changed the opening paragraph. A magnetosphere is by definition produced by an interaction with a plasma stream and a magnetic field. It is not just an area dominated by a magnetic field. As to Ganymede, it has a magnetosphere (http://science.nasa.gov/headlines/y2000/ast19may_1.htm ) but that magnetosphere is entirely within Jupiter's magnetosphere. So I stated that. The motion of ions and electrons trapped in Jupiter's magnetic field impinging on Ganymede create Ganymede's magnetosphere. If the phrase "resulting in complex interactions" seems awkward, go ahead and delete it. While the weaker magnetic fields of Mars and Venus do deflect the solar wind to an extent, these deflections are not usually referred to as magnetospheres. I think that Mars and Venus need not be mentioned at all in an opening paragraph but left it there, clarified, because it was there, and requested above. Canuck100 (talk) 09:49, 31 October 2009 (UTC)

## Stellar magnetosphere

I was a little surprised to find no mention of stellar magnetospheres on this article. It should be covered somewhere. (See Heliosphere for example.) Would it be better to discuss it here or on the Stellar magnetic field article? Thanks.—RJH (talk) 18:23, 18 April 2010 (UTC)

## Missing Citations

The latter 2/3 of the article has been flagged as missing citations. Shouldn't the article as a whole also be flagged as a result, until citations are provided? — Preceding unsigned comment added by 65.6.139.251 (talk) 11:57, 11 October 2011 (UTC)

Done. RockMagnetist (talk) 16:45, 15 October 2011 (UTC)

## Magnetosphere Doesn't Protect Ozone

At the end of the section "Earth's Magnetosphere" the article states:

Earth’s magnetosphere protects the ozone layer from the solar wind. The ozone layer protects the Earth (and life on it) from dangerous ultraviolet radiation.

However, this isn't true, and the cited source doesn't mention the magnetosphere at all (nor does the academic paper the source cites). The magnetosphere dips down near the poles, making the atmosphere there unprotected to the solar winds yet you don't see ozone depletion. — Preceding unsigned comment added by 169.233.20.225 (talk) 16:11, 31 May 2012 (UTC)

I request a new paragraph in this article (or on other page(s), with links to/from this one) on:

Power line radiation, and its effect on Earth's magnetosphere. This is referred to in Robert Helliwell and found in papers published on the Internet.

Any suggestions? GilesW (talk) 19:43, 11 June 2012 (UTC)

## The Moon's effect on Earth's magnetosphere

I request a new paragraph in this article (or on other page(s), with links to/from this one) on:

The Moon's effects on Earth's magnetosphere, in particular the effects of the new Moon's wake, and the full Moon's passage through the magnetotail. This is the subject of a paper "Interaction of the Moon with the Earth's Magnetosphere" published by NASA, among other info. Are those effects measurable at ground level?

Any suggestions? GilesW (talk) 19:48, 11 June 2012 (UTC)