Solar Flares (Radio Blackouts) | NOAA / NWS Space Weather Prediction Center Skip to main content NOAA Logo NWS Logo Organizations Space Weather Prediction Center National Oceanic and Atmospheric Administration Tuesday, January 09, 2024 17:55:37 UTC Main menu Home About Space WeatherImpactsEarth's Climate Electric Power Transmission GPS Systems HF Radio Communications Satellite Communications Satellite Drag Partners and StakeholdersCommercial Service Providers Federal Agencies International Organizations International Service Providers Space Weather Research PhenomenaAurora Coronal Holes Coronal Mass Ejections Earth's Magnetosphere F10.7 cm Radio Emissions Galactic Cosmic Rays Geomagnetic Storms Ionosphere Ionospheric Scintillation Radiation Belts Solar EUV Irradiance Solar Flares (Radio Blackouts) Solar Radiation Storm Solar Wind Sunspots/Solar Cycle Total Electron Content Additional InfoNOAA Space Weather Scales Customer Needs & Requirements Study Products and DataForecasts27-Day Outlook of 10.7 cm Radio Flux and Geomagnetic Indices 3-Day Forecast 3-Day Geomagnetic Forecast Forecast Discussion Predicted Sunspot Numbers and Radio Flux Report and Forecast of Solar and Geophysical Activity Solar Cycle Progression Space Weather Advisory Outlook USAF 45-Day Ap and F10.7cm Flux Forecast Weekly Highlights and 27-Day Forecast ReportsForecast Verification Geoalert - Alerts, Analysis and Forecast Codes Geophysical Alert Solar and Geophysical Event Reports USAF Magnetometer Analysis Report ModelsAurora - 30 Minute Forecast CTIPe Total Electron Content Forecast D Region Absorption Predictions (D-RAP) Geoelectric Field Models (US Canada 1D & 3D EMTF CONUS) Geospace Geomagnetic Activity Plot Geospace Ground Magnetic Perturbation Maps Geospace Magnetosphere Movies North American (US Region) Total Electron Content North American Total Electron Content Relativistic Electron Forecast Model SEAESRT STORM Time Empirical Ionospheric Correction WSA-Enlil Solar Wind Prediction WAM-IPE ObservationsBoulder Magnetometer GOES Electron Flux GOES Magnetometer GOES Proton Flux GOES Solar Ultraviolet Imager (SUVI) GOES X-ray Flux LASCO Coronagraph Planetary K-index Real Time Solar Wind Satellite Environment Solar Synoptic Map Space Weather Overview Station K and A Indices SummariesSolar & Geophysical Activity Summary Solar Region Summary Summary of Space Weather Observations Alerts, Watches and WarningsAlerts, Watches and Warnings Notifications Timeline ExperimentalACE Real-Time Solar Wind Aurora Viewline for Tonight and Tomorrow Night International Civil Aviation Organization (ICAO) Space Weather Advisory Solar TErrestrial RElations Observatory (STEREO) Data Access DashboardsAurora Aviation Electric Power Emergency Management Global Positioning System Radio Satellites Space Weather Enthusiasts Media and ResourcesEducation and Outreach Glossary News Archive Newsroom Subscribe Annual Meeting Feedback HomeAbout Space WeatherPhenomenaSolar Flares (Radio Blackouts) Search form Search using USASearch NOAA Scales mini https://services.swpc.noaa.gov Space Weather Conditions on NOAA Scales 24-Hour Observed Maximums R none S none G none Latest Observed R none S none G none Predicted 2024-01-09 UTC R1-R2 45% R3-R5 10% S1 or greater 10% G none Predicted 2024-01-10 UTC R1-R2 45% R3-R5 10% S1 or greater 10% G none Predicted 2024-01-11 UTC R1-R2 45% R3-R5 10% S1 or greater 10% G none 1234PrevNext R none S none G none Current Space Weather Conditions on NOAA Scales R1 (Minor) Radio Blackout Impacts HF Radio: Weak or minor degradation of HF radio communication on sunlit side, occasional loss of radio contact. Navigation: Low-frequency navigation signals degraded for brief intervals. More about the NOAA Space Weather Scales Solar Flares (Radio Blackouts) Solar Flares (Radio Blackouts)Solar flares are large eruptions of electromagnetic radiation from the Sun lasting from minutes to hours. The sudden outburst of electromagnetic energy travels at the speed of light, therefore any effect upon the sunlit side of Earth’s exposed outer atmosphere occurs at the same time the event is observed. The increased level of X-ray and extreme ultraviolet (EUV) radiation results in ionization in the lower layers of the ionosphere on the sunlit side of Earth. Under normal conditions, high frequency (HF) radio waves are able to support communication over long distances by refraction via the upper layers of the ionosphere. When a strong enough solar flare occurs, ionization is produced in the lower, more dense layers of the ionosphere (the D-layer), and radio waves that interact with electrons in layers lose energy due to the more frequent collisions that occur in the higher density environment of the D-layer. This can cause HF radio signals to become degraded or completely absorbed. This results in a radio blackout – the absence of HF communication, primarily impacting the 3 to 30 MHz band. The D-RAP (D-Region Absorption Prediction) product correlates flare intensity to D-layer absorption strength and spread. Solar flares usually take place in active regions, which are areas on the Sun marked by the presence of strong magnetic fields; typically associated with sunspot groups. As these magnetic fields evolve, they can reach a point of instability and release energy in a variety of forms. These include electromagnetic radiation, which are observed as solar flares. Solar flare intensities cover a large range and are classified in terms of peak emission in the 0.1 – 0.8 nm spectral band (soft x-rays) of the NOAA/GOES XRS. The X-ray flux levels start with the “A” level (nominally starting at 10-8 W/m2). The next level, ten times higher, is the “B” level (≥ 10-7 W/m2); followed by “C” flares (10-6 W/m2), “M” flares (10-5 W/m2), and finally “X” flares (10-4 W/m2). Radio blackouts are classified using a five-level NOAA Space Weather Scale, directly related to the flare’s max peak in soft X-rays reached or expected. SWPC currently forecasts the probability of C, M, and X-class flares and relates it to the probability of an R1-R2, and R3 or greater events as part of our 3-day forecast and forecast discussion products. SWPC also issues an alert when an M5 (R2) flare occurs. The table below provides the correlation between radio blackouts, solar flares, nominal energy flux (watts per square meter), and the designated severity event descriptor Radio Blackout….. X-ray Flare….. Flux (W/m2)….. Severity Descriptor R1 M1 0.00001 Minor R2 M5 0.00005 Moderate R3 X1 0.0001 Strong R4 X10 0.001 Severe R5 X20 0.002 Extreme *IMAGE courtesy of NASA Tags: phenomenaEarth Sun Relationship: near_sunImpacts: HF Radio Communications National Oceanic and Atmospheric Administration National Weather Service National Centers for Environmental Prediction Space Weather Prediction Center 325 Broadway, Boulder CO 80305 Disclaimer Privacy Policy About NOAA's National Weather Service Careers in Weather Large Footer Menu Home About Space WeatherImpactsEarth's Climate Electric Power Transmission GPS Systems HF Radio Communications Satellite Communications Satellite Drag Partners and StakeholdersCommercial Service Providers Federal Agencies International Organizations International Service Providers Space Weather Research PhenomenaAurora Coronal Holes Coronal Mass Ejections Earth's Magnetosphere F10.7 cm Radio Emissions Galactic Cosmic Rays Geomagnetic Storms Ionosphere Ionospheric Scintillation Radiation Belts Solar EUV Irradiance Solar Flares (Radio Blackouts) Solar Radiation Storm Solar Wind Sunspots/Solar Cycle Total Electron Content Additional InfoNOAA Space Weather Scales Customer Needs & Requirements Study Products and DataForecasts27-Day Outlook of 10.7 cm Radio Flux and Geomagnetic Indices 3-Day Forecast 3-Day Geomagnetic Forecast Forecast Discussion Predicted Sunspot Numbers and Radio Flux Report and Forecast of Solar and Geophysical Activity Solar Cycle Progression Space Weather Advisory Outlook USAF 45-Day Ap and F10.7cm Flux Forecast Weekly Highlights and 27-Day Forecast ReportsForecast Verification Geoalert - Alerts, Analysis and Forecast Codes Geophysical Alert Solar and Geophysical Event Reports USAF Magnetometer Analysis Report ModelsAurora - 30 Minute Forecast CTIPe Total Electron Content Forecast D Region Absorption Predictions (D-RAP) Geoelectric Field Models (US Canada 1D & 3D EMTF CONUS) Geospace Geomagnetic Activity Plot Geospace Ground Magnetic Perturbation Maps Geospace Magnetosphere Movies North American (US Region) Total Electron Content North American Total Electron Content Relativistic Electron Forecast Model SEAESRT STORM Time Empirical Ionospheric Correction WSA-Enlil Solar Wind Prediction WAM-IPE ObservationsBoulder Magnetometer GOES Electron Flux GOES Magnetometer GOES Proton Flux GOES Solar Ultraviolet Imager (SUVI) GOES X-ray Flux LASCO Coronagraph Planetary K-index Real Time Solar Wind Satellite Environment Solar Synoptic Map Space Weather Overview Station K and A Indices SummariesSolar & Geophysical Activity Summary Solar Region Summary Summary of Space Weather Observations Alerts, Watches and WarningsAlerts, Watches and Warnings Notifications Timeline ExperimentalACE Real-Time Solar Wind Aurora Viewline for Tonight and Tomorrow Night International Civil Aviation Organization (ICAO) Space Weather Advisory Solar TErrestrial RElations Observatory (STEREO) Data Access DashboardsAurora Aviation Electric Power Emergency Management Global Positioning System Radio Satellites Space Weather Enthusiasts Media and ResourcesEducation and Outreach Glossary News Archive Newsroom Subscribe Annual Meeting Feedback