What is Sunspots?
Sunspots is an interactive, real-time 3D model of the Sun that displays live space weather data from two official U.S. government sources: NASA's CCMC DONKI (Community Coordinated Modeling Center Database Of Notifications, Knowledge, Information) and NOAA's Space Weather Prediction Center (SWPC).
The visualization shows active sunspot regions, solar flare events, coronal mass ejections, and ambient space weather conditions including solar wind speed, proton density, interplanetary magnetic field strength, and the Kp geomagnetic index. All data updates automatically, ranging from every 1 minute for solar wind to every 15 minutes for active region positions.
What You Can Track
Solar Flare Classification
Solar flares are classified by their peak X-ray flux as measured by NOAA's GOES satellites in the 1-8 angstrom wavelength band. Each class represents a 10x increase in energy output.
| Class | Peak Flux (W/m²) | Impact |
|---|---|---|
| X | ≥ 10&sup-4; | Extreme. Widespread HF radio blackouts, satellite damage, power grid failures. Can trigger S and G scale events. |
| M | ≥ 10&sup-5; | Moderate. Brief HF radio blackouts at polar regions, minor radiation storms for astronauts in EVA. |
| C | ≥ 10&sup-6; | Small. Few noticeable effects on Earth. Most common type of significant flare. |
| B | ≥ 10&sup-7; | Minor. No significant Earth impact. |
| A | < 10&sup-7; | Background level. No Earth impact. |
NOAA R, S, and G Scales
NOAA uses three standardized scales to communicate space weather severity, each ranging from 1 (minor) to 5 (extreme).
R — Radio Blackout Scale
Measures high-frequency (HF) radio communication disruption caused by solar flare X-ray emissions ionizing Earth's dayside ionosphere. R1 causes weak degradation; R5 causes complete HF radio blackout on the entire sunlit side of Earth lasting hours.
S — Solar Radiation Storm Scale
Measures energetic proton flux at geosynchronous orbit. Elevated proton levels are hazardous to astronauts, can damage satellite electronics, and at S5 levels cause complete satellite blackout and elevated radiation at aviation altitudes.
G — Geomagnetic Storm Scale
Measures disturbance to Earth's geomagnetic field, typically caused by CME impacts. G1 storms produce weak power grid fluctuations and aurora visible at high latitudes. G5 storms can cause widespread voltage collapse in power systems and aurora visible as far south as Florida and southern Texas.
Where the Data Comes From
All data is sourced from official U.S. government space weather services. No API keys or authentication are required.
| Endpoint | Data | Refresh |
|---|---|---|
| DONKI FLR | Solar Flares | 5 min |
| DONKI CME | CME Events | 5 min |
| plasma-5-minute.json | Solar Wind | 1 min |
| mag-5-minute.json | IMF Bt | 1 min |
| noaa-planetary-k-index.json | Kp Index | 5 min |
| solar_regions.json | Active Regions | 15 min |
| swpc_observed_ssn.json | Daily SSN | 15 min |
| noaa-scales.json | R/S/G Scales | 5 min |
| suvi-primary-304.json | SUVI 304A | 15 min |
Space Weather FAQ
What are sunspots and why do they matter?
Sunspots are temporary dark areas on the Sun's visible surface (photosphere) caused by concentrated magnetic field lines inhibiting convection. They appear darker because they're cooler than surrounding plasma — roughly 3,500 K compared to 5,800 K for the normal photosphere.
Sunspots matter because they are the primary source of solar flares and coronal mass ejections. More sunspots generally means more space weather activity, which can affect satellite operations, radio communications, power grids, GPS accuracy, and aurora visibility. The number of sunspots follows an approximately 11-year solar cycle.
How are solar flares classified?
Solar flares are classified by their peak X-ray brightness in the 1-8 angstrom wavelength band, measured by NOAA's GOES satellites. The five classes, from weakest to strongest, are A, B, C, M, and X. Each letter represents a 10x increase in energy output. Within each class, a linear 1-9 scale provides further precision (e.g., M3.2 is roughly three times stronger than M1.0).
M-class flares can cause brief HF radio blackouts and minor radiation storms. X-class flares are the most powerful, capable of causing planet-wide radio blackouts, satellite damage, and when associated with CMEs, severe geomagnetic storms.
What is a coronal mass ejection (CME)?
A coronal mass ejection is a massive burst of solar wind and magnetic fields rising above the solar corona or being released into space. CMEs can contain billions of tons of magnetized plasma and travel at speeds from 250 km/s to over 3,000 km/s.
When a CME is directed toward Earth, it typically arrives in 1-3 days. The impact compresses Earth's magnetosphere and can trigger geomagnetic storms, producing enhanced aurora activity and potentially disrupting power systems, satellite operations, and communications.
What is the Kp index and how does it relate to auroras?
The Kp index is a global measure of geomagnetic activity on a 0-9 scale, derived from ground-based magnetometer stations. It quantifies disturbances in Earth's magnetic field caused by solar wind and CME interactions.
Kp 0-3: Quiet. Aurora visible only at high latitudes (Alaska, Iceland, northern Scandinavia).
Kp 4: Unsettled. Aurora extends to northern US states and southern Canada.
Kp 5-6 (G1-G2): Storm. Aurora visible in northern US, UK, and central Europe.
Kp 7-9 (G3-G5): Severe storm. Aurora potentially visible at mid-to-low latitudes.
What is solar wind?
Solar wind is a continuous stream of charged particles — mostly protons and electrons — flowing outward from the Sun's corona at speeds of 300-800 km/s. Normal solar wind has a density of roughly 3-10 protons per cubic centimeter at Earth's distance.
During CME events, solar wind speed can exceed 1,000 km/s and density can spike to 50+ p/cm³. The Sunspots app displays real-time measurements from NOAA's DSCOVR satellite positioned at the L1 Lagrange point, about 1.5 million km sunward of Earth, giving roughly 15-60 minutes of advance warning.
What is Solar Cycle 25?
Solar Cycle 25 is the current approximately 11-year cycle of solar magnetic activity. It began in December 2019 at solar minimum and has been significantly more active than predicted, with monthly sunspot numbers exceeding forecasts by 50-100%.
Solar maximum for Cycle 25 is expected around 2024-2026, with elevated sunspot counts, more frequent M and X-class flares, and increased CME activity. The Sunspots app tracks the daily observed sunspot number (SSN), which is one of the key indicators of where we are in the cycle.
What does the SUVI 304A image show?
The SUVI (Solar Ultraviolet Imager) 304 angstrom channel captures the Sun's chromosphere and transition region at approximately 50,000 K. This wavelength reveals active regions, prominences, filaments, and coronal holes that are invisible in white light.
The Sunspots app blends the latest SUVI 304A image with procedural noise to create an animated, realistic solar surface. The bright regions in the image correspond to areas of intense magnetic activity — the same regions that produce flares and CMEs.
How do space weather events affect Earth?
Space weather can impact Earth in several ways:
Radio & GPS: Solar flare X-ray emissions ionize the dayside ionosphere, disrupting HF radio and degrading GPS accuracy for minutes to hours.
Satellites: Energetic particles can damage electronics, degrade solar panels, and cause anomalous charging. Atmospheric drag increases during storms, altering orbits.
Power Grids: Geomagnetically induced currents (GICs) from severe storms can damage transformers and cause voltage instability.
Aviation: Increased radiation at polar flight altitudes and disrupted HF communications can force flight rerouting.
Aurora: Enhanced geomagnetic activity pushes aurora to lower latitudes, becoming visible to more people.
Can I view historical solar data?
Yes. The Sunspots app includes a timeline scrubber showing 30 days of flare activity and a date picker for jumping to specific historical dates. Dragging the timeline or selecting a date switches from live mode to historical mode, fetching archived flare and CME data from NASA DONKI for the selected period.
Note that real-time solar wind and Kp data are only available for the current period. Historical mode focuses on solar flare events, CMEs, and active region positions.
Is Sunspots free? Do I need an API key?
Completely free. No API keys, no accounts, no rate limits, no premium tiers. All data comes from publicly accessible U.S. government APIs (NASA CCMC DONKI and NOAA SWPC) that require no authentication.
What browser do I need?
Sunspots requires a browser with WebGL support, which includes all modern browsers: Chrome, Firefox, Safari, Edge, and their mobile equivalents. For the best experience, use a recent version of Chrome or Firefox on desktop. The app is fully responsive and works on mobile devices, though the 3D visualization is more detailed on larger screens.
What is the interplanetary magnetic field (IMF)?
The interplanetary magnetic field is the Sun's magnetic field carried outward by the solar wind. The key measurement is Bt (total field strength, in nanotesla) and Bz (the north-south component). When Bz turns strongly southward (negative), it can couple with Earth's magnetic field, allowing solar wind energy to enter the magnetosphere and triggering geomagnetic storms.
The Sunspots app displays the IMF Bt value from NOAA's real-time magnetometer data.
Space Weather Glossary
| Term | Definition |
|---|---|
| Active Region | An area on the Sun with strong, complex magnetic fields, often associated with sunspot groups and flare production. |
| Aurora | Light emissions caused by charged particles colliding with atmospheric gases, triggered by geomagnetic storms. Aurora borealis (north) and aurora australis (south). |
| CME | Coronal Mass Ejection. A large-scale eruption of magnetized plasma from the Sun's corona into interplanetary space. |
| Corona | The Sun's outermost atmosphere, extending millions of kilometers into space. Visible during total solar eclipses and in extreme ultraviolet imagery. |
| DSCOVR | Deep Space Climate Observatory. A NOAA satellite at the L1 Lagrange point providing real-time solar wind data. |
| DONKI | Database Of Notifications, Knowledge, Information. NASA's comprehensive space weather event database. |
| Geomagnetic Storm | A disturbance of Earth's magnetosphere caused by efficient exchange of energy from the solar wind into Earth's magnetic environment. |
| GIC | Geomagnetically Induced Current. Electric currents induced in power lines and pipelines during geomagnetic storms. |
| Heliographic Coordinates | A coordinate system on the Sun's surface using latitude (N/S from equator) and longitude (E/W from central meridian as seen from Earth). |
| Kp Index | Planetary K index. A 0-9 scale of global geomagnetic activity derived from ground magnetometer networks. |
| L1 Point | The first Lagrange point, ~1.5 million km sunward of Earth, where gravitational and orbital forces balance. Ideal for solar monitoring. |
| Photosphere | The visible surface of the Sun, with a temperature of approximately 5,800 K. Where sunspots appear. |
| Proton Density | Number of protons per cubic centimeter in the solar wind. Normal is 3-10 p/cm³; elevated during CME impacts. |
| Solar Cycle | An approximately 11-year periodic variation in solar activity measured by sunspot number, flare frequency, and magnetic polarity. |
| Solar Wind | A continuous flow of charged particles from the Sun's corona, traveling 300-800+ km/s through interplanetary space. |
| SSN | Sunspot Number. A daily count of sunspot groups and individual spots, used to track the solar cycle. |
| SUVI | Solar Ultraviolet Imager. An instrument on NOAA's GOES satellites capturing the Sun in extreme ultraviolet wavelengths. |
| SWPC | Space Weather Prediction Center. NOAA's official source for space weather forecasts, watches, and alerts. |