Is the Sun waking up faster than scientists expected?

For decades, scientists monitoring the Sun believed it was entering a period of declining activity, potentially resembling some of the longest and quietest phases ever recorded in solar history.

However, new findings from Nasa reveal a dramatic and unexpected shift that began in 2008.

Since then, the Sun’s behaviour has reversed course, steadily producing stronger solar winds, more frequent solar storms, and heightened space weather events.

The research, published in The Astrophysical Journal Letters under the title The Sun Reversed Its Decades-Long Weakening Trend in 2008 earlier this month, outlines how this reversal challenges long-held assumptions about the Sun’s behaviour and the dynamics driving its activity.

From a decline to an unexpected surge

The Sun’s behaviour is known to follow approximately 11-year cycles, alternating between periods of heightened activity, known as solar maximum, and quieter phases, known as solar minimum.

During solar maximum, the number of sunspots rises significantly, solar flares erupt more frequently, and coronal mass ejections (CMEs) — massive bursts of plasma and magnetic fields — are more common.

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These events are part of a natural rhythm that has been documented for centuries.

Leading up to the late 2000s, scientists observed a steady decrease in solar activity. This decline began in the 1980s and continued through Solar Cycles 22 and 23, which started in 1986 and 1996 respectively.

The reduction in activity became so pronounced that by the time Solar Cycle 24 began in 2008, it was one of the weakest cycles on record, showing fewer sunspots and diminished flare activity.

Based on these patterns, researchers anticipated that Solar Cycle 25, which began in 2019, would maintain similarly low activity levels.

Many experts believed the Sun was heading toward a prolonged phase of minimal activity, possibly similar to historical events like the Maunder Minimum or Dalton Minimum — periods when solar output dropped dramatically for decades.

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Those expectations were upended by new data.

Nasa’s analysis found that rather than continuing to weaken, the Sun began strengthening at the start of Solar Cycle 24. This upward trend has continued through the current Solar Cycle 25, defying earlier predictions.

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“All signs were pointing to the Sun going into a prolonged phase of low activity,” said Jamie Jasinski of Nasa’s Jet Propulsion Laboratory (JPL) in Southern California, who led the study.

“So it was a surprise to see that trend reversed. The Sun is slowly waking up.”

The evidence behind the discovery

The conclusions are based on a detailed examination of heliospheric data — measurements related to the vast bubble of space influenced by the solar wind, known as the heliosphere.

Researchers studied key indicators of solar wind strength, including its speed, density, temperature, thermal pressure, mass, momentum, energy, and magnetic field magnitude.

This analysis drew upon data collected by multiple Nasa spacecraft, particularly the Advanced Composition Explorer (ACE) and the Wind mission, both launched in the 1990s.

These missions have been continuously monitoring plasma and energetic particles flowing from the Sun toward Earth, providing decades of valuable information.

Using a platform called OMNIWeb Plus, managed by Nasa’s Goddard Space Flight Center, Jasinski and his colleagues compiled and analysed long-term records.

Their findings revealed that in 2008, at the start of Solar Cycle 24, solar wind measurements began to climb rather than decline. This increase has persisted over the past 17 years, indicating a fundamental shift in the Sun’s activity.

“But then the trend of declining solar wind ended, and since then plasma and magnetic field parameters have steadily been increasing,” Jasinski explained.

Why the change matters

The Sun’s changing behaviour is not just a matter of scientific interest. Increased solar activity can have direct and sometimes severe consequences for Earth and human technology.

When solar flares or CMEs erupt, they release huge amounts of energy and charged particles into space. If these particles strike Earth, they interact with the planet’s magnetic field, potentially causing a range of disruptions:

• Communication blackouts: Radio signals, especially those used for aviation and maritime navigation, can be interrupted.

• Satellite damage: Spacecraft can be damaged by the energetic particles, leading to temporary or permanent failures.

• GPS errors: Navigation systems can experience reduced accuracy or outages.

• Power grid failures: Large-scale geomagnetic storms have the potential to overload electrical grids, resulting in blackouts.

• Increased radiation risk: Astronauts and spacecraft beyond Earth’s protective magnetic field are at greater risk from radiation exposure during intense solar events.

On a more visible level, these interactions also produce spectacular natural light displays. Charged particles colliding with Earth’s atmosphere create the auroras — commonly known as the northern lights and southern lights.

As humanity prepares to send astronauts back to the Moon and eventually to Mars, understanding and predicting space weather has become increasingly important.

The Artemis programme, Nasa’s flagship initiative to return humans to the lunar surface for the first time in more than 50 years, requires precise knowledge of solar conditions to protect crews and equipment.

How Nasa is responding

Recognising the heightened risks, Nasa is expanding its space weather research efforts.

Later this month, three major missions are scheduled to launch to improve observations and forecasting capabilities:

• Interstellar Mapping and Acceleration Probe (IMAP): This mission will study how solar wind particles are accelerated and how they interact with interstellar space.

• Carruthers Geocorona Observatory: Focused on observing the outermost layer of Earth’s atmosphere and its interactions with solar activity.

• NOAA’s Space Weather Follow On-Lagrange 1 (SWFO-L1): Positioned at a stable point between Earth and the Sun to provide real-time monitoring of solar activity and space weather conditions.

The data from these missions will play a vital role in preparing for future Artemis missions and other deep space endeavors.

Improved forecasting will allow mission planners to time launches and operations to avoid periods of extreme solar activity, reducing risks for astronauts.

What the Sun’s history tells us

While the Sun follows an approximate 11-year cycle, known as the solar cycle, this is only part of a more complex pattern. During each cycle, the Sun’s magnetic poles reverse polarity.

When two solar cycles are considered together, they form what scientists call the Hale cycle, which lasts about 22 years.

Recent findings suggest that the Hale cycle may be more fundamental than the individual 11-year cycles. By studying paired cycles, researchers hope to gain deeper insight into the underlying mechanisms driving solar changes.

Historically, there have been periods when solar activity dropped far below normal levels.

Two of the most significant events are:

• The Maunder Minimum (1645–1715): A 70-year period when sunspots nearly disappeared, coinciding with some of the coldest decades of the “Little Ice Age.”

• The Dalton Minimum (1790–1830): A 40-year stretch of reduced activity that also saw notable climate impacts on Earth.

These historical events remain poorly understood. “We don’t really know why the Sun went through a 40-year minimum starting in 1790,” said Jasinski.

“The longer-term trends are a lot less predictable and are something we don’t completely understand yet.”

The sudden shift demonstrates the complexity of the Sun’s behaviour. Sunspot counts, while useful, provide only a partial picture.

Jasinski and fellow space physicist Marco Velli point out that a broader range of measurements is needed to fully understand the dynamics of the Sun.

At present, solar wind pressure remains lower than levels observed at the turn of the 20th century, but the trend is upward.

With inputs from agencies