The Sun runs on a cycle of about 11 years, and in October 2024 NASA and NOAA announced that it had reached the most active part of that cycle. This article explains what solar maximum is, what it changes on and around Earth, and what the announcement did and did not say.
What is the solar cycle?
The solar cycle is the Sun’s natural shift between low and high activity. It lasts roughly 11 years. At the height of the cycle, the Sun’s magnetic poles flip. Scientists track the cycle with sunspots, dark patches on the Sun linked to solar activity, which often mark where large flares or coronal mass ejections begin. During solar minimum the Sun is often spotless. A higher sunspot number indicates a stronger cycle, though the NASA page we used does not give a specific number.
What was announced?
On Tuesday, October 15, 2024, representatives from NASA, NOAA and the Solar Cycle Prediction Panel, which is co-chaired by the two agencies, announced in a teleconference that the Sun had reached its solar maximum period. Solar Cycle 25 is the current cycle. The page does not state when the cycle began, or how long the maximum will last, so we do not either.
What is solar maximum?
Solar maximum is the most active phase of the cycle, when the Sun can release large bursts of light, energy and radiation. Those bursts produce what scientists call space weather. Space weather events become more frequent when the Sun is most active. A related point is that solar activity does not change in a smooth line, so a maximum period can include quiet spells and sharp spikes. That last point is a general one and not from the NASA page.
What are the effects of space weather?
- Satellites and astronauts: both can be affected
- Communications: radio and GPS systems can be affected
- Power grids: grids on Earth can be affected
- Aurora: the May 2024 storm increased aurora visibility, and also affected satellites and infrastructure
What was the biggest flare?
On October 3, 2024, the Sun emitted an X9.0 flare, which NASA described as the largest of Solar Cycle 25 so far. That statement was made in October 2024, and the page does not describe flares after that date, so it should not be read as a current record.
Is the maximum a single day?
No. NASA and NOAA refer to a solar maximum period and not a single day. The page we read does not say how long the period lasts or when it peaks, so we do not estimate either.
How is this related to eclipses?
A total solar eclipse, such as the one covered in our article on the total solar eclipse of August 12, 2026, lets observers see the Sun’s corona, the outer atmosphere that feeds the solar wind. Eclipses and solar maximum are separate phenomena, but the corona looks different at different points in the cycle. That is a general observation. Our eclipse explainer describes how eclipses work.
What does this mean for energy and technology?
Because space weather can affect power grids and satellites, operators watch the cycle closely. Solar generation on Earth, such as a solar panel array, depends on sunlight, which changes only slightly across the cycle, and the NASA page does not discuss it. The concern for grids is about disturbances from solar storms, not about changes in sunlight.
Key facts at a glance
- Cycle length: roughly 11 years
- Announcement date: October 15, 2024
- Agencies: NASA and NOAA
- Largest flare of Cycle 25 as of October 2024: X9.0 on October 3, 2024
- Space weather effects: satellites, communications, power grids and aurora
Why does the Sun have a cycle?
The NASA page describes the cycle as a natural shift between low and high activity and notes the flip of the magnetic poles at its height, but it does not explain the underlying cause, so we do not. What the page does make clear is that the cycle is regular enough to be tracked and predicted by a panel, which is why NASA and NOAA can announce when the Sun enters each phase. That regularity is what makes the cycle useful for planning.
Key dates
- May 2024: a storm increases aurora visibility and affects satellites and infrastructure
- October 3, 2024: an X9.0 flare, the largest of Solar Cycle 25 at that point
- October 15, 2024: NASA and NOAA announce that the Sun has reached solar maximum
Glossary: terms used here
- Sunspot: a dark, cooler patch on the Sun’s surface linked to strong magnetic activity
- Solar flare: a sudden burst of light and radiation from the Sun, classified by letters such as X for the strongest
- Coronal mass ejection: a large cloud of solar plasma and magnetic field thrown into space
- Space weather: conditions in space driven by the Sun that can affect technology and the upper atmosphere
- Aurora: light displays in the sky caused by charged particles interacting with Earth’s atmosphere
These definitions are general ones and are not quoted from the NASA page.
How to read the announcement
Our own reading is that the announcement is a status report on the Sun’s position in its cycle, not a forecast of particular storms. Space weather events become more frequent at maximum, as NASA says, but the page does not predict when any specific event will occur. Anyone planning around aurora viewing or satellite operations should rely on live space weather forecasts from NOAA and not on the cycle announcement alone.
Frequently asked questions
What is solar maximum?
The most active phase of the Sun’s roughly 11-year cycle, when flares and space weather are most frequent.
Does solar maximum make the Sun brighter?
The NASA page describes bursts of light, energy and radiation, not a steady change in brightness.
Can solar storms damage power grids?
NASA says space weather can affect power grids on Earth, along with satellites and communications.