Solar Physics
Solar Prominence
Magnetic loops of plasma extending into the corona — visible above the Sun's limb
A solar prominence is a large, bright structure of plasma extending outward from the Sun's surface, anchored by magnetic field loops. Visible against the dark sky during eclipses or with H-alpha filters as pink/red arches. Quiescent (stable) prominences last weeks-months; eruptive prominences explode outward. When seen against the bright solar disk, they're called "filaments" (dark against the bright background).
- Typical scale50,000-100,000 km (Earth-sized to 10× Earth)
- Plasma temperature~10,000 K (much cooler than corona at 1 M K)
- Density100× denser than surrounding corona
- LifetimeDays to months (quiescent); minutes to hours (eruptive)
- Color (H-alpha)Pink/red emission
- Same feature on diskCalled "filament" (silhouette against bright disk)
Interactive visualization
Press play, or step through manually. The visualization is yours to drive — try it before reading on.
Watch the 60-second explainer
A condensed visual walkthrough — narrated, captioned, under a minute.
Why prominences matter
- Magnetic field structure. Direct visualization of solar magnetic loops.
- Space weather. Eruptive prominences cause CMEs.
- Plasma physics. Lab for studying magnetic confinement.
- Eclipse observation. Most spectacular feature during totality.
- Solar minimum/maximum. Prominences ubiquitous; activity cycle traceable.
- Educational. Easily seen with H-alpha filters.
- Predictive. Monitoring filaments warns of CMEs.
Common misconceptions
- Prominences are made of fire. They're plasma — ionized gas held by magnetism.
- Prominences are hot. Cooler than corona around them (~10,000 K vs 1 M K).
- Filaments are different from prominences. Same thing; viewed differently.
- All prominences erupt. Most quiescent (stable for weeks-months).
- Prominences only at solar max. Throughout cycle, but more abundant during maximum.
- Naked-eye visible. Only during eclipse; otherwise need filter or spacecraft.
Frequently asked questions
How are prominences supported?
Magnetic field loops act like "cradles" — magnetic tension holds plasma against gravity. Plasma is much cooler/denser than surrounding corona; without magnetic support, it would fall back to surface. Loop geometry is anchored at both ends to photospheric magnetic features. Stability depends on field configuration.
Why pink/red?
H-alpha emission from hydrogen at ~6563 Å (red part of spectrum). Plasma at ~10,000 K excites hydrogen to specific energy levels — emits red light when electrons return to lower states. Specialized H-alpha filters block other wavelengths to make prominences (and other chromospheric features) visible.
What's the difference between prominence and filament?
Same feature, different viewing geometry. Prominence — seen at solar limb (edge), against dark space → bright. Filament — seen against bright solar disk → dark silhouette (because plasma is cooler than surrounding photosphere). They are the same magnetic structures viewed from different angles.
When do prominences erupt?
Eruption occurs when magnetic stability breaks. Field reconnects, loop opens — plasma is expelled outward as coronal mass ejection (CME). Erupting prominence accelerates from km/s to thousands of km/s within minutes. Some material returns; some escapes solar gravity into solar wind.
How are prominences observed?
(1) Total solar eclipses — naked eye when corona becomes visible. (2) H-alpha filters with telescope. (3) Coronagraphs with prominence-detection capability. (4) UV/EUV imaging from space. (5) Spacecraft (SOHO, SDO, Solar Orbiter). Easily observable feature even with amateur equipment.
How big are typical prominences?
Length 50,000-100,000 km (Earth-sized comparable). Width 10,000-30,000 km. Some span 600,000 km — half the Sun's diameter. Heights variable. Quiescent prominences can be huge; eruptive ones often more dynamic and shorter-lived.
Are prominences related to flares?
Often co-located. Flares and prominence eruptions both occur near sunspot regions and active magnetic features. Major eruption can trigger flare; flare can destabilize prominence. Same underlying physics — magnetic energy storage and release in active regions.