We Fixed the Geometry of the Galactic Current Sheet

In my last update, I had the first real version of the Galactic Current Sheet surface model. I was combining pulsars, dust, the Radcliffe Wave and electron density models to build a corrugated surface and eventually solve for when the Sun crosses it. At that point, though, I still hadn’t independently resolved the magnetic reversal I actually needed. And, a lot has changed.

I was walking through the geometry with Ben Davidson (@SunWeatherMan / Twitter), and he caught two assumptions I’d implemented incorrectly:

1. The mean GCS should stay parallel to the Galactic plane.

2. The spiral phase should originate from the Galactic center, more like the heliospheric current sheet.

By the way, if you want to see these conversations between Ben and I they are included with membership at https://catastrophism.org

So I rebuilt the surface, and the geometry changed a lot.

First: observational data used

The magnetic part of this model is now mostly pulsars. A pulsar gives me two really useful measurements: Dispersion Measure, or DM:

DM = ∫ nₑ ds

DM tells me how many free electrons are along the path between us and the pulsar.

We also get Rotation Measure, or RM:

RM = 0.812 ∫ nₑ B∥ ds

RM also contains the direction of the magnetic field along that path.

So if I have pulsars in the same direction but at different distances, I can start reconstructing the magnetic field in depth. My database contains:

4,412 unique pulsars 2,315 usable RM measurements 17 independent magnetic-reversal centers

Those 17 reversal centers are very important for us. They’re places where the pulsar data show that the magnetic field changes direction. So, from the observational data, I’m locating the magnetic reversal points and then fitting the surface through them.

Dust, the Radcliffe Wave, stellar polarization, Planck and extragalactic RM still give me structural and magnetic context, but I’m keeping those measurements separate.

The new surface

The surface itself is defined by:

S(R, φ, z) = z - zGCS(R, φ)

The reversal surface is where:

S = 0

The new GC anchored surface is:

zGCS = zmid + A(R) sin(Φ)

with the amplitude growing outward from the Galactic center:

A(R) = A₀ tanh(R / RA)

and the spiral phase:

Φ = m(φ - φ₀) + kR R

The current best fit is:

zmid = -0.0469 kpc A₀ = 0.2935 kpc m = 2 φ₀ = -0.719 rad kR = 28.24 rad/kpc RA = 0.5 kpc

where:

zmid = average vertical position of the sheet
A₀ = how far the sheet waves above and below the Galactic plane
m = the number of large-scale wave modes around the Galaxy
φ₀ = where the wave is in its cycle
kR = how tightly the spiral winds as it moves outward
RA = how the corrugation grows away from the Galactic center

And because of Ben’s first correction:

gR = 0

This means the sheet stays parallel to the Galactic plane, and the corrugation moves above and below it.

That moved the reversal much closer

The old tilted magnetic surface put the closest modeled reversal roughly:

197 pc away

With the corrected geometry, the nominal nearest point is:

60.5 pc away

The bootstrap median is even closer:

43.5 pc

with the central uncertainty range:

14.9–141 pc

What about 1859?

Ben’s hypothesis is that the outskirts of the sheet reached us around 1859, while the central magnetic reversal comes later.

I model the density profile as:

n / npeak = exp(-α² / 2)

The near-term inverse solution gives:

α ≈ 0.403

which gives:

n1859 / npeak ≈ 0.922

So under that interpretation, 1859 wouldn’t mean first contact with a nearly empty outer tail. It’d mean we were already well inside the density enhancement and still moving toward the magnetic reversal.

Predict the Crossing

The pulsars are fantastic for reconstructing the Galactic scale magnetic structure, but they’re not designed to resolve a magnetic transition hundreds of AU from the heliosphere.

So now I’m moving much closer to home: Voyager, IBEX/IMAP, pickup ions, local interstellar neutrals, dust and nearby magnetic field measurements. If there really is a reversal approaching, that’s where I expect the next useful clue to come from.

We’re solving for timing next:

S[r☉(t), t] = 0

It’s a little scary modeling the timing of the end of the world. If you made it this far, thank you for your support.