Many thanks to SWLing Post contributor, Eric (WD8RIF), who writes:
This came in the most recent ARRL Contest newsletter:
The Sun, The Earth, and Near-Earth Space: A Guide to the Sun-Earth System by J. A. Eddy is a readable and accessible textbook that explains the dynamics of the Sun and its interaction with the Earth’s ionosphere. It’s available as a free download, courtesy of NASA and the International Living with a Star Program. Anyone using the ionosphere as a medium for radio wave transmission and wants to better understand propagation should find this book of interest. (Ward, N0AX)
Thank you for the stellar tip, Eric!
As an avid amateur astronomer, solar observation has been quite boring during 2018. As a shortwave radio enthusiast, the lack of solar activity has impacted that hobby as well.
Well, the catchword of the day is “surprise”!
I was alerted yesterday evening by Spaceweather.com that a large sunspot had emerged and developed into a group – with the two main sunspots’ diameter about as large as the earth.
Credit: Spaceweather.com – Sunspot group AR2720, photographed by Thierry Legault on Aug. 25th from the Saint-Véran/Astroqueyras observatory in the French Alps. An image of Earth has been inserted for scale (Link).
Another overnight email notification from Spaceweather.com stated a “surprise” G-3 Class Geomagnetic storm is underway (now!) caused by a coronal mass ejection.
Credit: Spaceweather.com – According to a NOAA computer model, almost 80 billion watts of power surged through Earth’s auroral oval during today’s geomagnetic storm (This image/forecast is updated every 30-minutes at this link).
Has this “surprise” impacted your radio weekend? I know it has impacted my astronomy weekend … I’ll be out there, soon, setting up my solar telescope to view today’s show in hydrogen-alpha!
Go to spaceweather.com to follow the developments.
Edit: Yes indeed, even excluding the sunspots the solar disc yielded more surface detail today via my H-alpha solar telescope than I’ve seen all year – as well as several nice solar prominences along the limb. I encourage anyone who has the proper telescope AND proper filters to take a look at ‘Ole Sol today (and hopefully for the next several days). I’ll have to check the shortwaves later.
Guest Post by Troy Riedel
Not a sunspot to be found. (Credit: SDO/HMI via Spaceweather.com)
Unfortunately, this is not news to brighten your day. According to Spaceweather.com, sunspots are disappearing faster than expected:
Sunspots are becoming scarce. Very scarce. So far in 2018 the sun has been blank almost 60% of the time, with whole weeks going by without sunspots. Today’s sun, shown here in an image [above] from NASA’s Solar Dynamics Observatory, is typical of the featureless solar disk.
The fact that sunspots are vanishing comes as no surprise. Forecasters have been saying for years that this would happen as the current solar cycle (“solar cycle 24”) comes to an end. The surprise is how fast.
“Solar cycle 24 is declining more quickly than forecast,” stated NOAA’s Space Weather Prediction Center on April 26th. This plot shows observed sunspot numbers in blue vs. the official forecast in red:
“The smoothed, predicted sunspot number for April-May 2018 is about 15,” says NOAA. “However, the actual monthly values have been lower.”
Continue reading the full story at Spaceweather.com.
I will be very happy to see sunspot numbers rise again–they eventually will, of course. I’ve almost forgotten what a proper band opening feels like.