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The Sun in extreme ultraviolet captured by NASA's Solar Dynamics Observatory — showing intense solar activity during Solar Cycle 25 maximum, with bright active regions and coronal loops visible across the solar disc

Solar Observing Guide · Space Weather · Solar Cycle 25

Solar Flares: Complete Guide — What They Are, How to Track Today's Activity, and Viewing Safety

Solar flares are the most powerful explosions in our solar system — sudden releases of magnetic energy from the Sun's surface that can affect Earth's atmosphere, disrupt communications, and create spectacular aurora displays. With Solar Cycle 25 reaching its peak in 2025–2026, solar activity is at its highest level in over a decade. This guide explains what solar flares are, how they are classified, how to track today's solar activity, and how to safely observe the Sun from your backyard.

Solar CycleCycle 25 (peak 2025–26)
Flare ClassesA, B, C, M, X (10× increase each)
Speed to Earth8 minutes (light) / 1–4 days (CME)
Best resourceNOAA SWPC + NASA SDO
By Elena Reyes Published: Updated: Reviewed & approved by Juhi Sahni, Senior Editor Editorial Standards
Elena Reyes — Senior Science Editor

Elena Reyes

Senior Science Editor

Covers NASA missions, space science discoveries, and astronomical events for Telescope Advisor. Translates complex astrophysical research into practical insights for backyard observers. Based in the San Francisco Bay Area.

What Is a Solar Flare?

A solar flare is a sudden, intense burst of radiation originating from the release of magnetic energy stored in the Sun's atmosphere. These explosions occur near sunspots — regions of intense magnetic activity on the Sun's visible surface — where twisted magnetic field lines become destabilised and reconnect, accelerating charged particles to near-light speed. The resulting flare releases energy across the entire electromagnetic spectrum, from radio waves to gamma rays.

The total energy released by a large solar flare is equivalent to millions of 100-megaton hydrogen bombs exploding simultaneously. An X-class flare — the most powerful category — can release as much energy as one billion megatons of TNT. Despite these staggering numbers, Earth's atmosphere protects us from the direct harmful effects of flare radiation, though the upper atmosphere can be significantly disturbed.

Solar flares are closely related to but distinct from coronal mass ejections (CMEs). A flare is a burst of electromagnetic radiation reaching Earth in 8 minutes; a CME is a cloud of magnetised plasma ejected from the Sun that takes 1–4 days to travel to Earth. Large flares are often accompanied by CMEs, and it is the CME that triggers the most dramatic space weather effects, including brilliant aurora displays at lower latitudes than usual.

Solar Flare Classification: A, B, C, M, and X

Solar flares are classified by their X-ray brightness as measured by NOAA's GOES satellites. The classification system uses letters A through X, each representing a tenfold increase in energy output. Within each class, a number from 1 to 9 provides further granularity.

Class Energy Level Frequency Earth Effects
A-class Lowest detectable Daily during solar max None
B-class Minor Daily during solar max None
C-class Medium Several per day during solar max Usually none; minor radio signal effects
M-class Strong 1–5 per week during solar max Radio blackouts (polar); aurora enhancement
X-class Extreme 1–10 per solar cycle Global radio blackouts; aurora visible at mid-latitudes; satellite damage risk

The most powerful flare ever recorded was the X28 flare on November 4, 2003 (during Solar Cycle 23), which saturated the GOES sensors at X28 but may have been as high as X45. More recently, on May 10, 2024, an X8.7 flare erupted from Active Region 3664 — the same sunspot group responsible for the extreme G5 geomagnetic storm that produced aurora visible as far south as Florida and Mexico. This event, the strongest geomagnetic storm in over 20 years, brought solar activity to mainstream attention worldwide.

How to Track Today's Solar Activity

Tracking solar flares in real time is easier than ever, thanks to free online resources from NASA, NOAA, and other space weather monitoring agencies. Here are the best tools for staying up to date with today's solar activity:

NOAA Space Weather Prediction Center (SWPC)

The official US government source for space weather forecasts, alerts, and real-time data. The SWPC website provides the current solar flare probability, X-ray flux graphs from GOES satellites, proton flux data, and geomagnetic storm watches. The 3-day forecast is particularly useful for planning observing sessions. Bookmark the "Solar X-ray Flux" plot — it shows flare activity in real time, updated every minute.

NASA Solar Dynamics Observatory (SDO)

NASA's SDO spacecraft captures the Sun in multiple wavelengths 24 hours a day. The SDO data page offers near-real-time images in 10 different wavelengths, including the 304 Ångström filter showing the chromosphere (where flares erupt), and the 171 Ångström filter showing coronal loops. The difference between a quiet Sun and an active Sun is immediately obvious when comparing these images day to day.

SpaceWeatherLive.com

A popular third-party website that aggregates data from NOAA and NASA into an easy-to-read dashboard. It provides real-time flare alerts, current geomagnetic conditions, aurora probability maps, and a history of recent flares. The "Solar Activity" page lists the most recent C-class, M-class, and X-class flares with their exact timestamps and peak X-ray flux.

Mobile Apps

The SpaceWeatherLive app (iOS and Android) sends push notifications for M-class and X-class flares. Solar Activity by Inove GmbH provides SDO imagery on mobile. For aurora chasers, the Aurora app (by J. Størmer) and My Aurora Forecast provide real-time Kp-index tracking and push alerts when aurora activity is elevated in your region.

How Solar Flares Affect Earth

Solar flares affect Earth in three primary ways: radio communications, satellite operations, and aurora activity. The severity of each effect depends on the flare's class and whether it is accompanied by a coronal mass ejection.

Radio Blackouts: X-rays from flares ionise the D-layer of Earth's ionosphere, absorbing high-frequency (HF) radio waves. During M-class flares, high-latitude radio communications can be disrupted. During X-class flares, global shortwave blackouts can occur, particularly on the sunlit side of Earth. This effect is immediate — the radio disruption begins the moment the X-rays arrive, 8 minutes after the flare erupts.

Geomagnetic Storms: If the flare is accompanied by a CME, the ejected plasma takes 1–4 days to reach Earth. When it arrives, it compresses Earth's magnetosphere and accelerates particles along magnetic field lines. This produces geomagnetic storms rated on a G1–G5 scale. During G5 storms (like the May 2024 event), aurora can be visible as far south as Florida, Texas, and the Mediterranean — a bucket-list experience for aurora chasers. Even G1–G2 storms produce visible aurora at high latitudes.

Satellite Risk: Energetic particles from flares and CMEs can damage satellite electronics, increase drag on low-Earth orbit satellites (heating and expanding the upper atmosphere), and pose radiation risks to astronauts. During major flares, satellite operators may power down sensitive instruments or adjust orbits. The 2003 Halloween storms caused more than 30 satellites to malfunction and forced the ISS crew to shelter in the more heavily shielded Zvezda module.

Solar Cycle 25: Why Now Is the Best Time to Observe

The Sun follows an approximately 11-year activity cycle, fluctuating between solar minimum (few sunspots, rare flares) and solar maximum (many sunspots, frequent flares). Solar Cycle 25 began in December 2019 and is currently at or near its peak (2025–2026), with sunspot numbers and flare activity exceeding early predictions.

The Space Weather Prediction Center's Solar Cycle 25 Prediction Panel originally forecast a peak sunspot number of 115, but actual activity has been significantly higher — the monthly sunspot number reached 195 in June 2025, more than 70% above the initial forecast. This means we are experiencing the most active solar period since Solar Cycle 23's peak in 2001–2002, making this an exceptional time for solar observing.

For amateur astronomers, this translates to more frequent and more dramatic solar observing opportunities. Large sunspot groups are visible on most days, M-class flares occur multiple times per week, and the possibility of witnessing an X-class flare — the kind that makes global news — is at its highest in nearly two decades. Whether you use a white-light solar filter for basic sunspot viewing or an H-alpha telescope for prominence watching, there has never been a better time to take up solar observing.

Safe Solar Observing: Never Look at the Sun Without Protection

WARNING: Never look at the Sun directly with your eyes, binoculars, or a telescope without proper solar filters. Permanent, irreversible eye damage can occur in seconds. Even during a solar eclipse, you must use certified solar viewing equipment. This cannot be overstated.

For safe solar observing, you have two main options:

White-Light Solar Filters (See Sunspots)

These filters fit over the front of your telescope and block 99.999% of incoming sunlight, allowing only a tiny fraction of visible light through. They reveal sunspots — dark regions of intense magnetic activity — and some subtle surface granulation. White-light observing is the most accessible form of solar astronomy and requires no special equipment beyond the filter. Always ensure the filter is securely attached and free of any pinholes or damage before use.

H-Alpha Telescopes (See Flares and Prominences)

Dedicated hydrogen-alpha telescopes use ultra-narrowband filters to isolate a specific wavelength of light (656.28 nm) emitted by excited hydrogen atoms in the Sun's chromosphere. These telescopes reveal solar flares, prominences (giant loops of plasma arcing above the solar surface), filaments, and the dynamic structure of active regions. H-alpha is the only way to see flares visually from your backyard. For the best options, see our Best H-Alpha Solar Telescope guide.

Frequently Asked Questions

What is a solar flare?

A solar flare is a sudden, intense burst of radiation from the Sun's surface, caused by the release of magnetic energy stored in the solar atmosphere. Flares release energy across the entire electromagnetic spectrum and can affect Earth's upper atmosphere.

How are solar flares classified?

Flares are classified as A, B, C, M, or X based on their X-ray brightness. Each letter represents a tenfold increase in energy output. X-class flares are the most powerful; M-class flares are moderate; C-class and below are minor.

Can I see a solar flare with my telescope?

Yes, but only with a dedicated H-alpha (hydrogen-alpha) solar telescope. White-light filters show sunspots but not flares. H-alpha telescopes reveal the chromosphere where flares erupt, making them visible as bright flashes of light. A standard telescope with a white-light filter will not show flares.

How long does it take a solar flare to reach Earth?

The electromagnetic radiation from a flare (X-rays, ultraviolet) reaches Earth in about 8 minutes — the time it takes light to travel from the Sun to Earth. If the flare includes a coronal mass ejection (CME), the particle cloud takes 1–4 days to arrive.

Where can I track solar flares today?

The NOAA Space Weather Prediction Center (swpc.noaa.gov) provides real-time X-ray flux graphs, flare alerts, and 3-day forecasts. NASA's Solar Dynamics Observatory (sdo.gsfc.nasa.gov) offers near-real-time images of the Sun. Third-party sites like SpaceWeatherLive.com aggregate this data into easy-to-read dashboards.

When is Solar Cycle 25 expected to peak?

Solar Cycle 25 is currently at or near its peak (2025–2026), with activity exceeding early predictions. The initial forecast was a peak sunspot number of 115, but actual numbers have reached 195, making this the most active solar period in over 20 years.