Ionospheric sensors

How HAARP works

As HAARP heats the ionosphere, electron clouds expand creating electron-density enhancements or depressions that align with the magnetic field lines. These are called field-aligned (density) irregularities.

Text based on transcript from video: https://www.youtube.com/watch?v=ZssJ0InqBcw&t=667s

HAARP transmits powerful radio waves into a localized area of the ionosphere above the facility. The altitudes of interest are from 70 to 350 km, i.e. in the D region of the ionosphere up to the F region. The frequencies that are used are those termed here "important characteristic frequencies" (to be described) or their harmonics.

The radio waves that are being transmitted into the ionosphere transfer energy to the electrons there, raising their temperature. Then, the clouds of electrons expand; however they can't expand randomly, but instead they are forced to expand along magnetic field lines. As a result, we have electrons that are lined up with the magnetic field lines and that bunch together creating "field-aligned-irregularities (FAI)". These can be used for many different applications including radio wave scattering, propagation effects and so on.

It is noted that at HAARP, the magnetic field lines are quite steep at about a 76-degree-angle. 


When a satellite transmits through field-aligned (density) irregularities., its signal may be amplified by 40 times.

Text based on transcript from video: https://www.youtube.com/watch?v=ZssJ0InqBcw&t=1022s

Figure 2 shows the HAARP instrument at the bottom and its radiation envelop directly overhead. When it heats in the ionosphere at the area shown, roughly between 200 and 300 kilometers altitude, we will have the formation of field-aligned irregularities in the region along the magnetic field lines*. 

If a satellite is overhead and transmits through these field-aligned irregularities (as shown in Figure 2**), its signal will show scintillation, meaning it will twinkle or flicker, as it will be refracted to a certain degree by the structures on which it will bump; however, quite surprisingly its signal may be characterized by a 16 dB gain, meaning an amplification by 40 times. Usually, the gain is smaller, such as 10 dB, meaning that the signal will be amplified by 10 times, which is still considered as a significant number.

Satellites can use these irregularities as reflection points: these can reflect down to a receiver on the ground. We can also transmit from the ground up into these irregularities; the radio waves will be reflected and can be received on the ground.


*It is noted that the magnetic field lines represent the slope lines of the magnetic field. 

** UHF satellite - signal at 255 MHz

Figure 2: Signal amplification during transmission through field-aligned-irregularities (from https://www.youtube.com/watch?v=ZssJ0InqBcw&t=1022s).

How HAARP generates ULF, ELF and VLF waves.

If HAARP transmits a wave of 5 MHz modulated at 1 kHz, we can obtain an ELF wave of 1 kHz.

https://www.youtube.com/watch?v=ZssJ0InqBcw&t=1135s

Text based on transcript: In Figure 3, we are transmitting a modulated HF signal up into the heated region. If this HF is modulated at some kilohertz frequency, then this gets demodulated by non-linearities in the heated region. As a result, we have propagating out of there the demodulated radio waves from that process. Those are received on the ground.

Figure 3: Generation of ULF, ELF and VLF waves by HAARP (from https://www.youtube.com/watch?v=ZssJ0InqBcw&t=1135s).

HAARP very long-distance propagation

https://www.youtube.com/watch?v=ZssJ0InqBcw&t=1350s

Text based on transcript: HAARP can create artificial ionospheric turbulence or AIT. This is related to non-linear phenomena and takes advantage of a type of wave guide that exists between the E and F regions of the ionosphere. There were some experiments done with this a few years ago for very long distance propagation, from HAARP to Antarctica i.e. a distance of approximately 15 000 kilometers. They used the HAARP to couple a signal into this wave-guide; and then they decoupled it through natural refraction at Antarctica and other locations that are far away. They found that the best propagation was along the solar terminator, also called the "gray line" (shown on the right).

Figure 4: HAARP very long distance propagation (from https://www.youtube.com/watch?v=ZssJ0InqBcw&t=1350s and https://sos.noaa.gov/catalog/datasets/daynight-terminator-daily/)


Modification of the ionosphere with radio waves - the pioneering ionospheric heater/phased array of Platteville (Boulder, Colorado), predecessor of HAARP 

Modifying the ionosphere with radio waves” by W.F. Utlaut

 New Scientist 55, No 808, p.288-290 


Reading notes

The Platteville Atmospheric Observatory near Boulder, Colorado was one of the first major ionospheric heaters in the world. Linked to the Institute of Telecommunication Sciences (ITS) and the U.S. Department of Commerce and Telecommunications, it operated from 1968 to 1984 on ionospheric processes. It is still operational performing wind profile studies. The transmitting aerial array consisted of 10 elements forming a ring of 110 cm in diameter. Using an effective radiating power of 100 MW, the upgoing power would be distributed over a circular area in the ionosphere of 100 Km in diameter with an approximate power flux density of less than 50μW/m2. The installation was designed to perform ionospheric modification with frequencies from 5 MHz to 10 MHz using right or left circular polarization. It was found that depending on the polarization, there were different profiles of velocity and paths transversed during propagation. Right polarization was associated to “ordinary waves” and O-mode, while left polarization to “extraordinary waves” and X-mode. 

When modification was performed with X-mode excitation, electron temperature would increase by 35% in the F-region area attained by the beam. Detection of electron heating was quantified by the attendant effect on the rate of dissociation-recombination of electrons and molecular oxygen ions which leads to the 630 nm emission of oxygen (red line) and the generation of air glow.  For this process, the reaction rate is inversely proportional to electron temperature so that the emission intensity decreases compared to background when the temperature is rapidly increased, and increases after the heater is off. Experiments showed that the increase and decrease of electron temperature occurs within tens of seconds.

When modification was performed with O-mode excitation, there was an unexpected and nearly opposite result; there was an increase in the 630 nm (red) oxygen line after power-on and decrease after power-off. The generation of airglow (enhancement of natural airglow) implied that electrons excited oxygen by collisions. For this process, significant numbers of electrons with energies greater than 2 electron volts (eV) are required, when the ambient level is approximately 0.5 eV. Enhancement of other emission lines indicated that some electrons obtained energies equal to perhaps 10 eV. These processes appear to require generation of plasma "parametric" instabilities. The term "parametric" refers to the periodic modulation of a certain parameter of an oscillating system with sufficient amplitude at a certain frequency to cause the oscillation to become unstable.

Figure 4:  Transmission and reception of a signal using ionospheric-related mechanisms (Source).