# Galactic current — the drift is nanometres per second

### Ampère reading of the named Milky Way disk · travel of kilometres in 12,000 years · no ledger row · no promote

**CPT Framework — Book C / FT-PERATT / GAL-PLASMA-FRAC**
**Date:** 2026-10-07
**Status:** **RECORD** · public page `/cosmology/galactic-current` · this file charters no §0bn row
**Parents:** `a_geom_ft_peratt_homology_spec.md` · `a_geom_ft_peratt_homology_results.md` · `a_geom_galactic_plasma_mass_fraction_consideration.md` · `a_geom_bulk_current_join_design.md` · §0bn967 · §0bn964 · §0bn660

Tags: **[E algebra]** of the frozen inputs · **[E honesty]** on what stays free

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## 0. One-line

> **The net galactic current, spread through the warm ionized disk at the frozen inputs, is a drift of \(8.94\times 10^{-9}\,\mathrm{m\,s^{-1}}\).** A carrier moves \(0.282\,\mathrm{m}\) in a year, \(3.39\,\mathrm{km}\) in \(12{,}000\) years, and \(4.00\times 10^{9}\,\mathrm{m}\) in one Hubble time at \(H_0=68.973\). A \(12{,}000\)-year sheet crossing is not this motion.

---

## 1. Frozen inputs

From the Peratt spec, catalogue values, not a fit:

| Input | Value |
|-------|--------|
| \(B\) | \(5\,\mu\mathrm{G}\) |
| \(n_e\) | \(0.03\,\mathrm{cm^{-3}}\) |
| \(T\) | \(8000\,\mathrm{K}\) |
| \(R\) | \(8.5\,\mathrm{kpc}\) |
| \(h\) | \(0.3\,\mathrm{kpc}\) |
| Warm ionized mass | \(\sim 2\times 10^{9}\,M_\odot\) |

\[
I=\frac{BR}{\mu_0}=1.044\times 10^{17}\,\mathrm{A}.
\]

The current crossing a radial cut of height \(h\) has mean density \(J=B/(\mu_0 h)\). Quasi-neutrality gives one relative drift,

\[
v_d=\frac{B}{\mu_0 n_e e h}=8.94\times 10^{-9}\,\mathrm{m\,s^{-1}}.
\]

That is \(8.94\,\mathrm{nm}\) in one second, and \(2.57\times 10^{-14}\) of the electron thermal speed at \(8000\,\mathrm{K}\) (\(3.48\times 10^{5}\,\mathrm{m\,s^{-1}}\)). A full reversal of the same field doubles the surface current and doubles the drift.

---

## 2. How far a carrier travels

| Clock | Distance at \(8.94\times 10^{-9}\,\mathrm{m\,s^{-1}}\) |
|-------|----------------------------------------------------------|
| One second | \(8.94\,\mathrm{nm}\) |
| One year | \(0.282\,\mathrm{m}\) |
| Eighty years | \(22.6\,\mathrm{m}\) |
| \(12{,}000\) years | \(3.39\,\mathrm{km}\) |
| One Hubble time, \(H_0=68.973\,\mathrm{km\,s^{-1}\,Mpc^{-1}}\) | \(4.00\times 10^{9}\,\mathrm{m}\) (\(4{,}000\,\mathrm{km}\)) |

The same fluid in a Harris sheet of half-thickness \(70\,\mathrm{pc}\) has a peak drift \(3.83\times 10^{-8}\,\mathrm{m\,s^{-1}}\) and travels \(14.5\,\mathrm{km}\) in \(12{,}000\) years. At \(160\,\mathrm{pc}\) the peak drift is \(1.68\times 10^{-8}\,\mathrm{m\,s^{-1}}\) and the travel is \(6.35\,\mathrm{km}\).

Drift kinetic energy is \(1.1\times 10^{-29}\) of the magnetic energy for electrons and \(2.0\times 10^{-26}\) for protons. Magnetic energy is \(0.621\,\mathrm{eV\,cm^{-3}}\). The banked plasma \(\beta\) is \(0.033\). The energy does not choose which sign slips. Proton gyroradius is \(170\,\mathrm{km}\). Electron gyroradius is \(4.0\,\mathrm{km}\).

\(B\), \(n_e\), and \(h\) are catalogue orders. A factor of a few in any one of them moves \(v_d\) by that factor. The travel in \(12{,}000\) years stays a few kilometres.

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## 3. What this motion is

The mass in the circuit is the warm ionized medium, about \(2\times 10^{9}\,M_\odot\). The banked disk split puts the stars near \(5\times 10^{10}\,M_\odot\) and the neutral gas near \(10^{10}\,M_\odot\). The plasma is quasi-neutral hydrogen: equal numbers of protons and electrons, mass in the protons, net charge at the scored leftover. The current is the slip \(v_i-v_e\).

A \(12{,}000\)-year crossing of a galactic sheet is a different claim. At \(7\,\mathrm{km\,s^{-1}}\) the Sun travels \(0.086\,\mathrm{pc}\) in \(12{,}000\) years. The published local magnetic reversal is a tilted plane \(0.25\)–\(0.55\,\mathrm{kpc}\) from the Sun (Booth et al. 2026, ApJ 997, 304). The Radcliffe Wave oscillates on a timescale of tens of millions of years (Konietzka et al. 2024, Nature 628, 62). The heliospheric current sheet turns over with the solar rotation and the 11-year cycle. None of those clocks is this drift.

The halo stays the open leftover of Book G. This record does not retire it.

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## 4. Integrity

| Gate | Verdict |
|------|---------|
| Drift at the frozen inputs | **Direct calculation** · \(8.94\times 10^{-9}\,\mathrm{m\,s^{-1}}\) |
| Travel in \(12{,}000\) years | **\(3.39\,\mathrm{km}\)** on the disk mean |
| \(12{,}000\)-year sheet crossing as this current | **Not this motion** |
| Which sign slips, and any faster canceling legs | **Free** |
| Halo | **Stays open** |
| Ledger row / chip / promote | **No** |

**Exit:** record only. Public text is `/cosmology/galactic-current`.