Solar minimum and what it could mean
We often take the sun for granted.
Sure, we gripe and grumble about the lack of sunshine on a cloudy day, but, on the whole, other than solar scientists, the vast majority of the Earth's population gives little or no thought at all to the incredibly complex and amazing physics that drives the sun to provide us with light and warmth.
The sun is currently in a period of reduced solar activity, referred to as a solar minimum. The sun operates, more or less, on a nine to 14 year solar cycle (the average being 11 years), with alternating peaks of increased solar activity (called a solar maximum, plural maxima), followed by quiet periods (solar minimum, plural minima) of low solar activity (think of oceans waves, with the 11-year period measured from crest to crest, or trough to trough).
Solar scientists think our sun may, over the next few decades, enter an extended period of reduced solar activity, called a grand solar minimum. The last time this happened was from 16501715 (referred to as the maunder minimum or the little ice age). During this time, in the northern hemisphere, the Earth's average annual surface temperature was significantly lower due to a combination of reduced solar activity and increased aerosols in the atmosphere from concurrent volcanic eruptions. Most solar scientists do not think we will again experience such an event due, primarily, to the impact of climate change, which is resulting in an overall average annual increase in the Earth's surface temperature.
Solar minima and maxima can, however, directly impact space weather, which indirectly impacts the Earth. During a solar minimum, the sun's magnetic field weakens somewhat, thereby providing less shielding to the Earth from cosmic rays (from distant supernovae explosions), posing a danger to astronauts in space.
Solar maxima usually produce large numbers of sunspots (areas of intense magnetic activity), which appear as dark spots on the sun's visible surface. The darkness of the spot is actually the result of these areas being up to 1,500C degrees cooler than the surrounding solar photosphere. Increased sunspot activity is associated with solar flares and coronal mass ejections - when the sun sends increased amounts of charged particles hurtling towards Earth - and other than its often negative impact on satellites, spacecraft, GPS and Earth's communications networks, it often manifests as increased aurora displays in the night sky. Correspondingly, solar minima reduce both the frequency and duration of aurora displays.
Solar scientists do not fully understand the occurrence of extended solar minima but think it may have to do with a much longer 9,000-year lull in the sun's solar activity. The current solar minimum has lasted about 100+ days so far this year (76 per cent with zero sunspots) and follows the 2019 low sunspot level (77 per cent). It is expected to last until mid-2025 when solar activity should begin to increase.
THE PLANETS THIS WEEK
Mercury (magnitude -0.4) will be visible in the evening sky low above the northwest horizon around 9:40 p.m., before setting shortly before 11 p.m. On June 2, Mercury will be at its highest point (10 degrees) in the evening sky, and on June 4, reaches its greatest eastern elongation (angular separation from the sun as seen from Earth).
Venus will reach inferior conjunction (passing in front of) with the sun on June 3, and is currently too close to the sun to be seen.
Saturn (magnitude +0.5) will be visible shortly after midnight above the southeast horizon, reaching about 23 degrees above the southern horizon before fading from view before 5 a.m.
Jupiter (magnitude -2.5) is visible above the southeast horizon shortly after 1 a.m., reaching 22 degrees above the southern horizon before fading by 5 a.m.
Mars (magnitude 0.0) appears around 2 a.m. in the southeastern sky, reaching 23 degrees above the horizon before fading from view shortly before 5 a.m.
There is a partial lunar eclipse on June 6, beginning around 11:30 p.m. However, as this is what is called a penumbral eclipse, with only 57 per cent of the moon passing through the Earth's penumbral shadow (think two-circle bull's eye target, with the penumbral shadow being the fainter outer circle), so the moon will not darken perceptibly. It will all be over by about 11:50 p.m.
The full moon on June 5 is sometimes referred to as the strawberry moon or the rose moon.
Until next week, clear skies.
Events: June 3 - Moon at perigee (closest to Earth)
June 5 - Full (strawberry/ rose) moon