Mercury's magnetic field and definition of "active"

[Sailboat]

For the second time in two days, the Washington Post has described Mercury’s magnetic field in a way that I believe is flat out wrong. Before I write them a letter, I’d like the SDMB folks to vet my claim.

The errors (as I perceive them):

@NASA Photos Reveal Mercury Is Shrinking

Mercury is the only solar system planet other than Earth to have a magnetosphere.

@Messenger's Pictures From Mercury Surprise Scientists

Among the mysteries researchers hope to unravel is where and how Mercury was formed and the nature of the magnetic fields around it. Earth is the only other planet with such an active magnetosphere.

Surely both of these quotes are in error. The first one is an AP wire article, so I can’t totally blame the Post, but Jupiter’s giant, highly active magnetosphere is pretty well-known, being discussed in movies and numerous educational programs. And surely its famous radio noises, aurora, and impact on Jupiter’s moons qualify it as “active”…more active in any sense that Mercury’s magnetosphere is…right?

I’m also pretty sure the other outer planets, the gas giants, have powerful magnetospheres as well.

In fact, if you look here, you’ll see the likely source of the misunderstanding:

@Windows to the Universe

Mercury is the only inner planet other than the Earth that has a significant magnetic field (220 nT).

Looks like the reporters missed the significance of the words “the only inner planet other than the Earth”.

But is it possible that Mercury’s proximity to the sun causes so much material to strike it’s magnetosphere that that’s what they’re talking about? Could that be the definition of “active” from the second article? Or something else? Or are they just plain wrong?

Thanks for opinions before I potentially make a fool of myself scientifically.

Sailboat

[Squink]

Straight from Messenger: Mercury’s Internal Magnetic Field

MESSENGER saw an internal magnetic field that is well described by the field from a dipole nearly aligned with the planet’s spin axis (dipole tilt ~ 10°). This geometry is similar to that observed by Mariner 10 during its first flyby. The field strength is weaker by about one third than that detected by Mariner 10 during its third (and last) flyby, owing primarily to the difference in trajectories (Mariner 10 flow directly over the magnetic pole where the field strength is greatest). When corrected for our best estimate for the external field, the MESSENGER observations and the two Mariner 10 passes are consistent with very similar solutions for the mean planetary magnetic dipole. The dipolar field is consistent with an active electrical dynamo in which the magnetic field is produced by electrical currents flowing in an outer core of molten metal.

The cores of venus and mars are quiescent, leaving only remnant fields.

[Xema]

There seems to be little question that Jupiter, Saturn, and Uranus have significant magnetospheres.

[Xema]

Also Neptune. Pluto not so much (and is it even a planet?).

[Chronos]

This is the problem with using the single word “planet” for objects as different as Earth and Jupiter. In an ideal world, we’d have completely separate words for “big rocky orb orbiting a star”, “big non-fusing gassy orb orbiting a star”, and “big icy orb orbiting a star”. This way, we’d also manage to avoid the whole debate about Pluto: Mercury and Earth are the only rockballs with active magnetism, Ceres is the smallest of the rockballs, Jupiter is about as big as a gasball can get, and Pluto is one of the largest of the iceballs.