This propagation produces strong constant signals with minimal fading. These signals can remain present for hours.
This mode is caused by a temperature inversion. A temperature inversion is when the air above is hotter in temperature than the air below
Scenario 1 Scenario 2 Upper Troposphere Upper Troposphere Warmer & Reduced Humidity Normal Temp Colder & Increased Humidity Warmer & Reduced Humidity Warmer & Reduced Humidity Colder & Increased Humidity (Fog) Ground Level Ground Level
It has been noted that relative barometric pressure needs to be above or equal to 1020 hPa for tropo to appear
The signals reflected via the E layer often are over in a matter of minutes. These E signals build into a strong signal and then fade back as quickly as they arrived.
The science in the section is based on observations of patterns of external influences which might be triggering sporadic E
Noteable Sporadic E times during May to Sep in the day are:
- 08:00 - 10:00
- 12:00 - 14:00
- 17:00 - 19:00
Can be triggered by intense thunder storms. The mid point between 2 DX stations is often where the thunder storm is. In the image below X's marks the thunder storm activity
Can be triggered by a sudden rising of barometric pressure. Sudden rising such as a difference of around 20 hPa in 2 days.
Can be triggered 24 hours later by an Earth facing C class solar flare
Seems to also be better when there are no Sun spots
Seems to happen within a couple of hours of a solar flare
Seems to happen when there has been several days of no solar activity and suddenly a sun spot with crackling magnetic fields appear over the edge of the sun
Waves of ionisation across Europe caused by solar flares seems to result in Sporadic E
Signals are similar in characteristics to Sporadic E except the signals flutter in strength as apposed to fading in/out
Solar flares from the sun! energising the E layer