Solar activity and HF/VHF propagation page

                                                    CO8TW

                                       Information about radio propagation on HF and VHF for Hams and SWL.

                                           (This page will automatically update every 15 minutes.)

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                                               https://helioforecast.space/solarcycle

                                               https://www.solarham.net/progression.htm

                                                                        Progression of solar cycle.

At 18 minutes past the hour, radio stations WWV and WWVH broadcast the latest solar flux number, the average planetary A-Index and the latest mid latitude K-Index. In addition, they broadcast a descriptive account of the condition of the geomagnetic field and a  forecast for the next three hours. You should keep in mind that the A-Index is a description of what happened yesterday. Strictly speaking, the K-Index is valid only for mid latitudes.

 

http://www.swpc.noaa.gov/products/3-day-forecast     3 day forecast.

http://spawx.nwra.com/spawx/list27do.html     Predicted Sunspot Numbers and Radio Flux for next 27 days.

http://cluster.f5len.org/sun/27do.png     Solar activity forecast for next 27 days..

http://cluster.f5len.org/sun/dsd.png     Last 30 days daily solar data.

ftp://ftp.swpc.noaa.gov/pub/weekly/RecentIndices.txt     Recent Solar Indices of Observed Monthly Mean Values.

          http://cluster.f5len.org/index.php?p=forecast    Propagation forecast.

 

        Pass solar cycles.

http://www.hamqsl.com/solar101vhf.php

http://www.hamqsl.com/solarsun.php

http://www.hamqsl.com/marston.php

                                   Click here to see the most recent image of the far side of the sun at http://gong.nso.edu/data/farside/

Solar X-Rays                                                                                                                         Geomagnetic Field

VHF Aurora      144 MHz E-Skip

                                                                          https://www.swpc.noaa.gov/products/

                                                                          https://www.solarham.net/index.htm

                                                                          Current Space Weather Conditions.

                                                                                                K index.

                                                                               https://helioforecast.space/solarwind/

                                                                                               Solar wind

https://helioforecast.space/static/sync/predstorm_real.txt (From https://helioforecast.space/solarwind)
1 hour time resolution. Updated every 30 minutes. The data shown in the plots are available in ASCII format in a 1 hour time resolution
Currently, this forecast only works for high-speed solar wind streams, and will fail during times when solar storms, also known as coronal mass ejections, impact the Earth's magnetic field

                                                                                  Current solar images.

                                                                        https://www.solarham.net/solarwind.htm

                                                            Real time solar wind (Speed, Bz, density and Temp)

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  Putting it all together

* Higher solar flux levels are generally good for HF
* High K and A indices are generally bad – result in absorption and breakdown of the F region.
* Solar Flux / K index / Solar wind speed and Bz will give you a real-time indication of what bands you should concentrate on.
* Bz going south(-) and an increased solar wind speed (450km/s+) are generally bad news for HF.
* If your signals follow a polar path that cuts through the auroral zone(s) and the K index is high you will have problems.
* Spring/Autumn/Winter are better than Summer as the ionosphere is cooler, denser and MUF is higher during the day. Ionic  composition is different in Winter too. But night time MUFs are higher in summer.
* The opposite is true in the southern hemisphere.
* Spring/Autumn good for trans-equatorial contacts.
* As the sun gets higher D layer absorption grows, but the MUF rises, so follow the MUF up during the day and down at night.

* The center of the visible solar disk is the region that has maximum effect on Earth.

 

  Flares.

 

* Check the higher bands for openings for several hours following a solar flare, or a ten-flare event, due to the enhanced E/F layer ionization, possibly temporarily raising the MUF.
* If you’re in a QSO when a major flare causes an HF blackout, it seldom lasts more than an hour. If you’re working a contest, this hint could be useful. Take a break, but don’t QRT!
* X-rays do provide extra ionization to the E/F layers for improved reflectivity and a higher MUF. Exploit the benefits of a solar flare.
* The most damaging effects of a solar flare is actually the arrival of the shockwave 2-3 days later, triggering a geomagnetic storm.
* Often our magnetic field gets very quiet following a strong geomagnetic storm for 12–24 hours. This is an excellent time to work 40–160M due to very low noise levels.
* Use the current K-Index from WWV or the internet to determine the current geomagnetic conditions. The A-Index is actually yesterday’s geomagnetic condition, and does not represent present conditions.
* As soon as the solar storm ceases, HF noise levels become quiet with an elevated MUF, lasting until sundown. Night time conditions on 80-40M can be excellent. The daytime MUF the next day may be elevated as well.
* when the geomagnetic storm subsides. Night time noise levels on 40-80M can be very low.
* The x-rays from flares (class M5.0 or larger) can be intense enough to have a considerable impact on ionospheric radio communications. In some cases, the absorption can be strong enough to completely blackout all radio communications between points more than 3,000 to 4,000 km up to frequencies as high as 10 MHz for a period of between 15 to 30 minutes. Minor absorption can maintain weaker than normal signal strengths for an additional 20 to 30 minutes. These types of major flares are much less frequent than minor M-class flares.
 

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                                                                                Near real time MUF map.

The following map shows Maximum Usable Frequencies (MUFs) for 3000 kilometer radio signal paths.  More importantly, the current sunspot number (SSN) and Planetary A-index are updated every 30 minutes on the bottom of this image.  Additionally, the grey line position, auroral ovals, and sun position are provided.

                                                                                      Near real time MUF map.

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