Yuriy V. Goncharenko

Statistical characteristics of trans-atmospheric UHF signals obtained during strong solar proton events 

 

In my PhD work I investigated the atmospheric response on powerful solar proton events (SPE). It was a part of fundamental investigations of IRE NASU named Solar-Terrestrial relations and Solar Activity influence on weather and climate. The created experimental technique was simple and cost-effective for continuous remote monitoring of atmosphere. Those investigations were focused on searching of trigger mechanisms allowing to convert small-scale (<0.1%) Solar energy variations to middle-scale (0.5-2%) variations of solar power flow in the low atmosphere. Within the framework of the project I have developed radiometric receiver and software for data recording and pre-treatment.

To evaluate the atmospheric changes we used transmission probing technique. As a signal source we have used TV-satellite AsiaSat 3S, the receiver was placed in Kharkov, Ukraine. Carrier frequency of the signal was 3.6GHz.

First of all I'd like to note that full cycle of measurements was performed during more than one year. We couldn't predict strong Solar flare so we had to carry out continuous measurement. As a result we have caught 16 strong solar proton events (SPE).

The variations of signal level wasnt very strong, and we were obliged to do very accurate measurements. With the course of time the real gain of the receiver can changes in 3-4 times (more than 5dB) and I have developed special calibration technique to avoid this type of errors.The measurement precision of our receiver was up to 0.5dB!

On this figure you can see the remote unit of receiver where: 1 - is LNB, 2 is transmitting antenna of calibration unit.

 Remote unit of receiver: 1 - is LNB, 2 is transmitting antenna of calibration unit.

 

At the next picture you can see indoor part of the receiver.  At the screen of spectrum analyzer (top left corner of the picture) you can see the spectrum of satellites signal (part A), and line which is related to calibration signal. We know the real power of this signal and we know resulting power at the output of device. So, we can calculate real gain of receiver and evaluate behavior of transatmospheric signal 

Indoor unit of the receiver

It is found, that during strong SPE the deep rapid fading of signal was appeared.  The probabilities of signal decreasing below fixed level during 6 strong SPE were shown on next figure.

 The probabilities of signal decreasing below fixed level during 6 strong SPE

  1 SPE at 22.05.2003 (p.f.u. = 820); 2 - SPE at 24.07.2003 (p.f.u. = 317); 3 - SPE at 09.11.2003 (p.f.u. = 404); 4 - SPE at 28.10.2004 (p.f.u.=29500); 5 - SPE at 30.10.2004 (p.f.u.= 3300); 6 - SPE at 02.11.2004 (p.f.u.=1570);

 

The power of solar flare can be measured by particle flux unit (p.f.u.). One particle flux unit equals to 1 particle per square centimeter of sensor area.

There were the most powerful events which were appeared during our observation. They had power from 400p.f.u. to 30000 p.f.u. Region A of Part 4 of this figure is a good illustration of Murphy's law. The power supply of receiver had been dead when the biggest solar flare begun.    

Nevertheless, we can see that significant increasing of deep fadings probability appears in 8-12 hours after SPE had begun (zero position at all graphs). This time is related to lag time of high energy solar particles.