High Frequency Active Auroral Research Program - Research

Research

HAARP's main goal is basic science research of the uppermost portion of the atmosphere, termed the ionosphere. Essentially a transition between the atmosphere and the magnetosphere, the ionosphere is where the atmosphere is thin enough that the sun's X-rays and UV rays can reach it, but thick enough that there are still enough molecules present to absorb those rays. Consequently, the ionosphere consists of a rapid increase in density of free electrons, beginning at ~70 km, reaching a peak at ~300 km, and then falling off again as the atmosphere disappears entirely by ~1,000 km. Various aspects of HAARP can study all of the main layers of the ionosphere.

The profile of the ionosphere is highly variable, changing constantly on timescales of minutes, hours, days, seasons, and years. This profile becomes even more complex near Earth's magnetic poles, where the nearly vertical alignment and intensity of earth's magnetic field can cause physical effects like aurorae.

The ionosphere is traditionally very difficult to measure. Balloons cannot reach it because the air is too thin, but satellites cannot orbit there because the air is still too thick. Hence, most experiments on the ionosphere give only small pieces of information. HAARP approaches the study of the ionosphere by following in the footsteps of an ionospheric heater called EISCAT near Tromsø, Norway. There, scientists pioneered exploration of the ionosphere by perturbing it with radio waves in the 2–10 MHz range, and studying how the ionosphere reacts. HAARP performs the same functions but with more power and a more flexible and agile HF beam.

Some of the main scientific findings from HAARP include

1. Generating very low frequency radio waves by modulated heating of the auroral electrojet, useful because generating VLF waves ordinarily requires gigantic antennas
2. Generating weak luminous glow (measurable, but below that visible with a naked eye) from absorbing HAARP's signal
3. Generating extremely low frequency waves in the 0.1 Hz range. These are next to impossible to produce any other way, because the length of a transmit antenna is dictated by the wavelength of the signal it must emit.
4. Generating whistler-mode VLF signals that enter the magnetosphere and propagate to the other hemisphere, interacting with Van Allen radiation belt particles along the way
5. VLF remote sensing of the heated ionosphere

Research at the HAARP includes

1. Ionospheric super heating
2. Plasma line observations
3. Stimulated electron emission observations
4. Gyro frequency heating research
5. Spread F observations (blurring of ionospheric echoes of radio waves due to irregularities in electron density in the F layer)
6. High velocity trace runs
7. Airglow observations
8. Heating induced scintillation observations
9. VLF and ELF generation observations
10. Radio observations of meteors
11. Polar mesospheric summer echoes (PMSE) have been studied, probing the mesosphere using the IRI as a powerful radar, and with a 28 MHz radar, and two VHF radars at 49 MHz and 139 MHz. The presence of multiple radars spanning both HF and VHF bands allows scientists to make comparative measurements that may someday lead to an understanding of the processes that form these elusive phenomena.
12. Research on extraterrestrial HF radar echos: the Lunar Echo experiment (2008).
13. Testing of Spread Spectrum Transmitters (2009)
14. Meteor shower impacts on the ionosphere
15. Response and recovery of the ionosphere from solar flares and geomagnetic storms
16. The effect of ionospheric disturbances on GPS satellite signal quality