In May and June 2024 we saw the highest sunspot numbers on the sun since 2002, but have we reached solar maximum?
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The sun follows an 11-year solar cycle of waxing and waning activity. Although he was not the first astronomer to discover the solar cycle, the solar cycle numbering and naming convention was first introduced in 1852 by Swiss astronomer Johann Rudolf Wolf. By then, the sun was already in Solar Cycle 9. As of December 2019, we are now in Solar Cycle 25.
A given solar cycle begins at solar minimum, when the sun is almost free of sunspots. During this period, no solar flares or mass ejections (CMEs) can occur for several months. From this period of solar minimum, solar activity gradually increases over the years, until the period of solar maximum. During solar maximum, large solar flares and CMEs are most common.
Because solar maximum is defined by the peak of this 13-month smoothed curve, solar maximum may not actually occur in the month with the highest sunspot count. Taking Solar Cycle 24 as an example, the highest monthly sunspot count was recorded in February 2014, but the official solar maximum was reached in June 2014.
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Meanwhile, in the current solar cycle, May 25 and June 2024 saw the highest monthly sunspot count since September 2022. It is possible that these months will have the highest sunspot counts we will see, even if the 13-month smoothed value (which defines solar maximum) continues to rise for a few more months. Alternatively, it is also possible that the following months will see sunspot counts higher than May and June.
The latest modeling efforts from NOAA, which use existing sunspot data to predict the peak of the solar cycle, estimate a solar maximum between July 2024 and January 2025. However, while the peak of the solar cycle may be imminent, it will be some time beyond that time frame before we can confirm when solar maximum will actually occur.
During solar maximum, geomagnetic storms often occur. Geomagnetic storms are not dangerous to the human body on the surface of the Earth. But they can affect some terrestrial technologies, such as power grids, communications, and satellites in orbit around the Earth. Almost everything the modern world relies on could be knocked out of sync if knocked out by a sufficiently severe solar storm.
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With an expected solar maximum from July 2024 to January 2025, we could easily reach the end of 2025 or 2026 before we can confidently state when solar maximum occurred.
Source: space.com
