Home▸Electromagnetism▸Plasma Globe (2D): Filament Discharge Cross-Section

⚡ Plasma Globe (2D): Filament Discharge Cross-Section

2D cross-section plasma globe: draw electric discharge filaments from a central Tesla electrode to a glass boundary with a canvas physics model — drive frequency, filament count, intensity and jitter are all live parameters with a numeric readout.

Electromagnetism2DEasy60 FPS⇄ 3D version

About this simulation

This is the 2D companion to the shader-driven 3D Plasma Globe. Instead of a GLSL fragment shader evaluating colour per-pixel, every discharge filament here is an explicit polyline: a chain of points walked outward from the central electrode to the glass boundary, bent at each step by value noise and drawn with lineTo(). The same physical picture — a high-voltage electrode ionising low-pressure noble gas, with filaments finding the path of least resistance to the glass — is now something you can watch get built stroke by stroke.

🔬 What it shows

Each filament is computed as 40 connected segments from the electrode radius to the glass radius. At every segment the angle is nudged by a seeded value-noise sample, so the path wanders exactly like the fBm noise in the 3D version — but here you can see the underlying list of (x, y) points that makes up the curve, not just its rendered glow.

🎮 How to use

Filament count (2–14) sets how many discharge paths are drawn. Intensity / glow controls stroke brightness and the additive glow pass. Flicker / jitter scales how far each segment's angle can wander and how fast filaments pulse in brightness. Drive frequency (15–80 kHz) sets how fast the flicker oscillation actually runs — a real parameter, since plasma globes are driven by kHz-range AC through a step-up transformer. Move the pointer over the globe to pull the nearest filament toward it.

💡 Did you know?

A plasma globe's driver typically runs at 20–50 kHz — well above mains frequency and below audio-amplifier range, chosen so the transformer core stays small while the discharge still looks continuous to the eye (above roughly 50 Hz, flicker fuses into an apparently steady glow, the same effect that makes a fluorescent tube look continuously lit).

Frequently asked questions

How is this different from the 3D Plasma Globe?

The 3D version renders filaments as a continuous GLSL fragment-shader field — every pixel independently computes whether it's "inside" a filament. This 2D version instead builds each filament as an explicit sequence of connected points (a polyline) with a JavaScript loop, then strokes it onto a Canvas 2D context. The physical picture is the same, but here the discharge path is literal geometry you could log to the console, not a shader glow field.

What does the Drive frequency slider actually control?

It sets the period of the flicker oscillation used for each filament's brightness and micro-wander — a filament's angle and glow both include a sin(t · frequency) term, so raising the slider from 15 kHz to 80 kHz visibly speeds up the flicker, the same way a real plasma globe's driver frequency sets how fast its discharge re-strikes.

How is the "playful voltage" figure calculated?

Like the 3D version, it's a display-only lookup: filament count (2–14) maps to an approximate voltage range of 4–28 kV in 2 kV steps. No electric-field solve happens — the filaments are geometric polylines shaped by noise, not a physically solved potential field.

Why do the filaments bend toward my pointer?

The nearest filament's target angle is blended toward the pointer's angle (measured from the electrode) each frame, mimicking how your fingertip on a real glass globe provides a lower-resistance path to ground and pulls the nearest arc toward it.

⚙ Under the hood

2D cross-section canvas companion to the 3D shader plasma globe: each discharge filament is an explicit noise-bent polyline walked from a central Tesla electrode to the glass boundary, with live filament-count, intensity, jitter and drive-frequency (kHz) controls plus a numeric readout of voltage, frequency and average filament reach.

plasma globetesla coilelectric dischargeelectromagnetismdrive frequencycanvas physics

2D · HTML5 Canvas 2D · 60 FPS target · runs fully client-side, no install