Sunspot region AR2665 has rotated to a position now directly facing the Earth; courtesy spaceweather.com, NASA
The sun has generally been quiet in recent days as it heads rapidly towards the next solar minimum. In fact, there have been 44 spotless days this year which makes up 23% of the time and this already easily surpasses the 32 days experienced in 2016. The current solar cycle (24) has turned out to be historically weak with the lowest number of sunspots since cycle 14 peaked more than a century ago in 1906. However, even during weak cycles and overall quiet periods on the sun there can be sporadic strong storms and large sunspot regions. Indeed, there is now a very large sunspot region – the largest of the year so far – and it is currently directly facing the Earth.
Daily observations of the number of sunspots since 1 January 1900 according to Solar Influences Data Analysis Center (SIDC). The thin blue line indicates the daily sunspot number, while the dark blue line indicates the running annual average. The recent low sunspot activity of solar cycle 24 is seen in the circled region on the lower, right. Data source: WDC-SILSO, Royal Observatory of Belgium, Brussels. Last day shown: 30 June 2017. Graph courtesy climate4you.com.
There were two days last week that featured a completely spotless sun, but then a new sunspot region started to emerge on July 6th over the sun’s eastern limb and it grew quite rapidly as it rotated into fuller view. In fact, the sunspot region now officially known as AR2665 doubled in size in the subsequent 24 hours and then reached behemoth levels by July 9th – almost as wide as Jupiter stretching more than 125,000 km from end-to-end.
Another view of the sunspot region AR2665 that now directly faces the Earth; image courtesy NASA/SDO
Today AR2665 directly faces the Earth which means any sudden coronal ejection emanating from that region could have an important impact on Earth’s upper atmosphere. According to spaceweather.com, AR2665 has an “unstable beta-gamma magnetic field that harbors energy for M-class explosions”. So far, this biggest sunspot region of the year has been quiet, but we’ll monitor it closely over the next couple of days.
Meteorologist Paul Dorian