HFU HF Underground
General Category => General Radio Discussion => Topic started by: ChrisSmolinski on April 29, 2019, 2128 UTC
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Low solar activity got you down? Lack of NVIS conditions on 43 meters causing grief?
When a solar wind stream hits the Earth, we all know it tends to mess up the geomagnetic field, raising the K index is generally disrupting HF communications. BUT... I have noticed the first few hours after the stream hits, there is a bump in the foF2 level of the ionosphere. This usually increases the MUF so that 43 meters is open for NVIS (no skip zone). It only lasts for a few hours at most, so you need to time it well. The best way to do this is to monitor the HFU propagation page. Go down to the Skip Zone section, where there are real time foF2 plots. I find the Wallops Island VA station gives relatively valid information for the East Coast, where most of us live. https://www.hfunderground.com/propagation/index.html#skipzone
Here is the plot in question:
(https://i.imgur.com/GBHISYR.png)
The blue trace is the current day. You want it to be at or above 7 MHz (or as close as we can get this part of the solar cycle). It may take frequent monitoring to catch the short bump, but can be very worthwhile. Assuming folks at the other end of the ionosphere are also monitoring this and get on the air.
As it turns out, the next solar wind stream arrival is forecast for May 2nd.
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The solar wind arrived early! You can see it arrived just before 1300 UTC, and that produced a bump (increase) in the foF2 value as measured at Wallops Island Virginia. foF2 is the highest frequency which is reflected with a vertical incidence.
(https://i.imgur.com/uT3zT7Z.png)
(https://i.imgur.com/8GKM8To.png)