Live Solar Activity & Geomagnetic Storms

Solar Cycle 25 is in full activity maximum since July 2025 and extending into late 2026. Geomagnetic storms, M and X-class flares, coronal mass ejections, real-time Kp index: this guide compiles everything you need to follow space weather, understand its consequences on Earth, and — for the citizen observer — anticipate aurora windows and operational risks (GPS, satellites, electricity).

Solar Cycle 25 (max July 2025 – late 2026)

The Sun is not a stable ball of fire: its activity varies along an 11-year cycle on average (sometimes 9, sometimes 13), during which the number of sunspots, flare frequency and solar wind intensity oscillate between a minimum (quiet Sun) and a maximum (active Sun). This cycle, discovered by German amateur astronomer Heinrich Schwabe in 1843, structures all of space weather.

Solar Cycle 25, officially started in December 2019, succeeds Cycle 24 (2008-2019), the weakest in a century. The first predictions from the Solar Cycle Prediction Panel (NOAA / NASA) projected a modest maximum around July 2025, with about 115 monthly sunspots. Observations have refuted this: since late 2023, the Sun exceeds 160 monthly sunspots, and the maximum was officially declared reached in October 2024.

The solar panel published a revision in March 2025: Cycle 25 will be more active than predicted, with a plateau of high activity extending into late 2026, followed by a gradual decline toward the minimum estimated in 2030-2031. Concretely, this means 2025 and 2026 are the two most active years of the current decade, with maximum probability of observing auroras at low latitudes — and maximum risk of operationally disruptive storms.

How to explain this underestimation? Predictive models rely on previous solar minimum conditions (polar field intensity) and historical cycle data. Cycle 25 demonstrated the limits of these models: the Sun remains a chaotic object whose internal magnetic dynamics (dynamo effect) retain irreducible unpredictability. This is precisely why modern solar observatories (SDO, Parker Solar Probe, Solar Orbiter) remain essential.

Understanding solar flares (classes A, B, C, M, X)

A solar flare is a sudden release of energy in the solar corona, equivalent to several billion thermonuclear bombs. It manifests as an intense burst of electromagnetic radiation across the spectrum: visible light, ultraviolet, X-rays and gamma. Detection is primarily achieved through measurement of the X-ray flux between 1 and 8 angstroms by NOAA's GOES satellites.

Flares are classified on a logarithmic scale with 5 letters and 9 sub-levels per letter (e.g. X1.7, M9.3):

An X1 flare is ten times more intense than an M1, and a hundred times more than a C1. The most powerful flares ever recorded reached X28-X45 (November 4, 2003, during the "Halloween solar storms" — the sensor saturated). What matters for ground impact is less the flare itself than the coronal mass ejection (CME) sometimes accompanying it — most X-class flares do not generate Earth-directed CMEs.

Flares are observed in near real time by SDO (Solar Dynamics Observatory, NASA), which produces extreme ultraviolet images at a 12-second cadence. Active regions are numbered (e.g. AR3664, source of the May 2024 storms) and their evolution is followed for 14 days, the duration of mean solar rotation seen from Earth.

CMEs — formation, 1-3 day propagation, Earth impact

A coronal mass ejection (CME) is the sudden expulsion of a billion tons of magnetised plasma by the solar corona, at speeds between 250 and 3,000 km/s. It is the mass and magnetic field component of the solar event, as opposed to the purely radiation component of the flare.

The distinction is crucial for terrestrial consequences: an X flare without CME produces an immediate radio blackout (X-rays hit the ionosphere in 8 minutes) but no geomagnetic storm. A CME without strong flare (from an eruptive filament) can produce a major storm if properly oriented. An X flare + full halo CME directed at Earth is the ideal scenario for a severe storm.

Formation and coronagraph imaging

CMEs are visualised by coronagraphs, instruments that artificially occult the solar disk to reveal the corona. Reference images come from SOHO/LASCO C2 and C3 (NASA/ESA, in operation since 1995, updated every 12 minutes) and more recently from Solar Orbiter. A CME appears as a luminous halo in radial expansion around the Sun. When this halo is complete (surrounding the entire solar disk), it is called a full halo CME, signature of an ejection oriented either directly toward or directly away from Earth.

Sun-Earth propagation

Sun-Earth distance is 149.6 million km. CME arrival delay strictly depends on its speed:

• Slow CME (250-500 km/s): 4 to 7 days arrival.
• Moderate CME (500-1,000 km/s): 2 to 4 days arrival.
• Fast CME (1,000-2,000 km/s): 1 to 2 days arrival.
• Extreme CME (>2,500 km/s): 15 to 24 hours arrival.

The CME associated with the 1859 Carrington event reportedly traveled in 17h40, making it one of the fastest ever documented. For comparison, the modern record is held by the November 4, 2003 CME, which reached Earth in 19 hours.

L1 measurement by DSCOVR

The DSCOVR satellite (Deep Space Climate Observatory, launched 2015) is positioned at Lagrange point L1, 1.5 million km from Earth, in gravitational equilibrium between Sun and Earth. It measures incoming solar wind with 30 to 60 minutes lead time on its terrestrial arrival. Key parameters: speed (km/s), density (protons/cm³), Bz component of interplanetary magnetic field (nT). A strongly negative Bz (< -10 nT) maximises magnetic reconnection efficiency with Earth's field, triggering the storm.

The Kp index — how to read it, 0-9 scale, NOAA source

The Kp index (from German planetarische Kennziffer) is the world standard unit for measuring Earth's magnetic field disturbances. It is a discrete logarithmic scale 0 to 9, calculated every three hours by NOAA SWPC and GFZ Potsdam from data of thirteen magnetic observatories distributed at mid-latitudes (between 44° and 60°).

The G level is the public and operational counterpart of Kp, used by NOAA in alert bulletins to electrical grid operators, satellites and aviation. A G5 storm is rare: 4 to 5 occurrences per solar cycle, one every 2-3 years during maximum, almost none during minimum.

Real-time official sources to consult: NOAA SWPC (Boulder, Colorado), GFZ Potsdam (Germany), and the ESA Space Weather Office. Vigi-Sky aggregates these feeds in its Auroras page and Space Weather module.

Major geomagnetic storms 2024-2025

The 2024-2025 period will be remembered in space weather annals as one of the most active since the 2003 Halloween storms. Three events deserve detailed analysis.

1. Gannon Storm (May 10-11, 2024) Kp 9 · G5 · first G5 since 2003 Active region AR3664 released between May 8 and 11 five X-class flares (including X8.7), accompanied by five successive CMEs. The merging of these plasma clouds constituted a combined event of exceptional intensity. Auroras observed across mid-latitude Europe, the southern US, Florida, Texas, Mexico. Estimated economic losses: 500 million to 1 billion USD, mainly in US agriculture (precision GPS disturbance during spring planting). Named "Gannon storm" in honour of astrophysicist Jennifer Gannon, who passed away shortly after the event.
2. October 2024 Storm (October 10-11, 2024) Kp 9 · G5 · second G5 of cycle 25 Originating from an X9.0 flare on October 9 from region AR3848. Auroras observed across mid-latitudes including Italy, Greece. Notable: the CME hit Earth head-on with a measured speed of 1,600 km/s and Bz of -45 nT — one of the most negative ever recorded in magnitude. Starlink traffic strongly disrupted, several satellites temporarily out of service.
3. 2025 Events Multiple G3-G4 · 2 G5 · cycle plateau 2025 confirms the high activity plateau. At least six G3 storms and three G4 events occurred between January and September, with two new brief G5 events in June and August. Auroras visible from mid-latitudes have become "ordinary" — a phenomenon changing the cultural relationship of observers with the sky. Some amateur photographers accumulated more aurora observation evenings in the year than during the entire previous decade.

These events also revealed a new technological vulnerability: dependence of agricultural systems on centimetric GPS (RTK), Starlink constellations on ionospheric stability, and polar aviation on solar wind predictability. For the first time since industrialisation, a moderate solar storm (G3-G4) entails measurable economic costs — whereas in the 20th century, only Carrington-type G5 events received serious attention.

Consequences on Earth (auroras, satellites, GPS, transformers, blackouts)

The impact of a geomagnetic storm manifests at different altitudes and through several distinct physical mechanisms. Here is a hierarchical overview of consequences.

Aurora borealis and australis

The best-known visual consequence. During a G5 storm, the auroral oval, normally centred on the poles between 65° and 75° latitude, descends to 40-45° latitude, making auroras visible from Spain, southern US, New Zealand. No health danger associated with observation. See our complete auroras guide for details.

GPS and navigation disturbances

GPS signals cross the ionosphere, whose density fluctuates abruptly during a storm. Consequences: positioning errors of several meters (vs a few centimeters in differential RTK mode), intermittent signal loss, inability to use differential corrections. Critical sectors: precision agriculture, geodesy, civil aviation (GPS landing), directional oil drilling.

Low-orbit satellites

Starlink, ISS, telecommunications and Earth observation satellites are on the front line. Effects: atmospheric heating (the atmosphere expands, increases orbital drag, forces correction manoeuvres), electrostatic charging on surfaces (risk of damaging discharge), memory upset by energetic particles (embedded program bugs). In February 2022, SpaceX lost 40 Starlink satellites in a single moderate storm, the increased drag preventing their insertion into operational orbit.

High-voltage electrical transformers

This is the most systemic risk. Geomagnetically induced currents (GIC) flow through long continental power lines and enter high-voltage transformers via grounding. In vulnerable transformers (unprotected magnetic saturation), this causes overheating, insulation degradation, and destruction. The Hydro-Québec blackout of March 13, 1989 (Kp 9) remains the iconic incident: 9 hours of total outage for 6 million people, following the shutdown of transformers in 90 seconds.

Polar aviation

Trans-polar flights (Europe-Asia via the North Pole) are systematically rerouted to lower routes in case of severe storm, to avoid the increased radiation doses received by crew and passengers (going from 5 µSv/h to over 50 µSv/h). Cost per rerouting estimated at 100,000 USD (additional fuel, cascading delays).

The 1859 Carrington event — the worst known storm

On September 1, 1859, British amateur astronomer Richard Carrington observes from his Surrey residence a flare of unprecedented intensity — a white luminous flash directly visible to the eye through the telescope, lasting five minutes above a sunspot group. Seventeen hours later, in the night of September 1 to 2, Earth is struck by the most violent geomagnetic storm ever documented.

The estimated intensity of the Carrington storm exceeds Kp 11 or 12 on a modern scale capped at 9. Greenland ice core analyses (presence of beryllium-10 and nitrates) confirm the exceptional magnitude.

On the geological scale, even more powerful events have been documented. The 774-775 Miyake event, identified by carbon-14 anomalies in Japanese cedar tree rings, corresponds to a solar storm estimated 10 to 20 times more powerful than Carrington. If such an event hit modern industrial civilisation, the impact would be catastrophic.

How to prepare? (citizen preparedness + light survivalism)

The question of preparing for solar storms has become mainstream since 2024. The reasonable approach lies between indifference (what can one do at the individual level?) and catastrophism (bunker-type preparation). Here is a graduated protocol, from minimal to prudent.

Level 1 — Information and alerts (10 min)

• Subscribe to NOAA SWPC alerts (free, email).
• Follow the Vigi-Sky Space Weather widget on the homepage.
• Mobile app Space Weather Live (push alerts).

Level 2 — Digital protection (1 h)

• Regular offline backup of critical documents (external hard drive, USB stick).
• Preventive download of offline road maps (Maps.me, OsmAnd).
• Keep a printed list of emergency contacts.

Level 3 — Short-duration autonomy (2 h, < $100)

• Flashlight + spare batteries or solar-rechargeable.
• Power bank (10,000-20,000 mAh) kept charged.
• Battery or hand-crank radio (AM/FM, NOAA band if international).
• Water reserves (3-5 L per person) and long-shelf-life food (3-7 days).

Level 4 — Prudent preparation (one weekend, < $500)

• Small portable generator or nomad battery type EcoFlow / Jackery.
• Portable solar panel (100 W) to recharge batteries during outage.
• Self-contained gas stove (butane cartridges).
• Pharmacy contents renewed (chronic medications 1 month, first-aid kit).

For private individuals, this Level 4 is an investment that also serves in case of regular storms, network outages, post-natural-disaster situations. The most dangerous is not the solar storm itself, it is generalised panic and supply disruptions that follow. Discreet preparation is also a civic act.

The Sun does not threaten us. It simply reminds us that our technological civilisation rests on a fragile balance with a star we have forgotten to listen to.