neutral-sheet-distance

neutral-sheet-distance is a skill for Claude Code, Codex from spedas/spedas_agent_kit. It costs 101 tokens per session (2,442 once invoked), scanned A, original, MIT.

A workflow for calculating how far a spacecraft is from the modelled neutral sheet in Earth’s magnetotail, and whether it is north or south of it. The neutral sheet is the thin current-carrying region dividing the tail’s two magnetic lobes.

In plain words
What is it for?
Use it to measure neutral-sheet distance, identify the spacecraft’s north or south position, or detect a crossing when the signed distance changes. It is intended for near-tail spacecraft data, not dayside orbits.
Why use it?
It turns a spacecraft position into useful current-sheet geometry for studying crossings and changes in the magnetotail.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: installed under .agents/ (shared by several agents).

Good fit Use it to measure neutral-sheet distance, identify the spacecraft’s north or south position, or detect a crossing when the signed distance changes. It is intended for near-tail spacecraft data, not dayside orbits.

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Install with agentmods
npx agentmods add skills/spedas/spedas_agent_kit/neutral-sheet-distance
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add spedas/spedas_agent_kit --skill neutral-sheet-distance
Clone the repo
git clone --depth 1 https://github.com/spedas/spedas_agent_kit

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for neutral-sheet-distance

README.md
[![agentmods](https://agentmods.dev/badge/skills/spedas/spedas_agent_kit/neutral-sheet-distance.svg)](https://agentmods.dev/skills/spedas/spedas_agent_kit/neutral-sheet-distance)
Your own site
<a href="https://agentmods.dev/skills/spedas/spedas_agent_kit/neutral-sheet-distance"><img src="https://agentmods.dev/badge/skills/spedas/spedas_agent_kit/neutral-sheet-distance.svg" alt="Measured on agentmods" height="20"></a>
Per session 101 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,442 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00101 $0.02442
Opus 5 $0.00051 $0.01221
Sonnet 5 $0.00020 $0.00488
Haiku 4.5 $0.00010 $0.00244

Measured 7d ago against content hash 9c3ca85f9ff1, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

neutral-sheet-distance scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.agents/plugins/spedas-codex/skills/neutral-sheet-distance/SKILL.md · 93 lines

How it starts

The opening of the file, as written. The whole thing — 93 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Neutral-sheet distance (magnetotail current-sheet geometry)

Given a spacecraft GSM position time-series in the magnetotail, compute the signed distance from the spacecraft to the model neutral sheet along GSM-z (or the GSM-z coordinate of the sheet itself), pick an empirical neutral-sheet model, and use the sign of the result to decide whether the spacecraft is north or south of the current sheet. This is the geometry context for plasma-sheet / current-sheet crossing studies (THEMIS, MMS, Cluster, Geotail, etc.). There is no dedicated "neutral sheet" MCP tool and there should not be — the value is the position fetch + model call + interpretation procedure.

When to use

  • "How far is THEMIS/MMS from the neutral sheet on ?"
  • "Is the spacecraft north or south of the tail current sheet?"
  • "Did the spacecraft cross the neutral sheet during this interval?" (sign change of sc-to-NS distance)
  • Providing current-sheet geometry context for a tail reconnection / flapping / dipolarization study.

Do not use this on the dayside, far outside the model's near-tail validity region, or for a non-tail orbit — the empirical fits are only meaningful in the magnetotail (roughly the nightside, within ~ -30 Re < X_GSM < a few Re).

Tool chain (all already exist)

plan_spedas_observationcreate_spedas_analysis_bundle → (get_ephemeris or load_data_source / browse_data_parameters / fetch_data_product) to obtain the GSM position → optional transform_coordinates / transform_timeseries_coordinates to land in GSM → a reproducible Python note in the bundle that calls the PySPEDAS neutral-sheet backend → export compact CSV/NPZ → render_tplot for the distance panel. Wrap everything in create_spedas_analysis_bundle for provenance.

MCP/default-surface boundary

pyspedas.neutral_sheet is an external PySPEDAS backend, not an Agent Kit MCP tool (external_runtime_route.not_an_mcp_tool: true). MCP-only clients should produce the GSM position/time artifacts plus a notes/run_neutral_sheet.py or next-step note in the analysis bundle, then report that evaluating the neutral sheet model requires a local Python runtime with PySPEDAS. Do not attempt to call neutral_sheet as an MCP tool.

Read the full file on GitHub · 93 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 7d ago First seen · 93 lines · 101 tokens per session scan A 9c3ca85f9ff1

Subscribe to this mod's changes

neutral-sheet-distance is a skill published in the GitHub repository spedas/spedas_agent_kit (3 stars, last pushed 1mo ago), licensed MIT. It adds 101 tokens to every session and 2,442 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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