High-frequency Active Auroral Research Program (HAARP) is based in Alaska and it's a high-power, high frequency (HF) transmitter for studying the ionosphere. The principal instrument is a phased array of 180 HF crossed-dipole antennas capable of radiating 3.6 megawatts into the upper atmosphere and ionosphere. Transmit frequencies are selectable in the range of 2.7 to 10 MHz.
The research team have announced that they will be carrying out tests from the 28th of February to the 3rd of March 2024.
The press release is shown below and I've added a map to show location and distance.
To: Amateur Radio & Radio Astronomy Communities
From: HAARP Program Office
Subject: Notice of Transmission
The High-frequency Active Auroral Research Program (HAARP) will be conducting a research
campaign February 28-March 3 UTC, with operating times specified in the table below. Operating
frequencies will vary, but all HAARP transmissions will be between 2.8 MHz and 10 MHz. Actual
transmit days and times are highly variable based on real-time ionospheric and/or geomagnetic
conditions. All information is subject to change.
Some examples of experiments planned for this research campaign are the production of ELF and VLF emissions and studies on the effects of ionospheric plasma waves on orbiting satellites. These experiments will help lead to a greater understanding of the production and enhancement of ELF/VLF waves, as well as lay groundwork for future studies of satellite interactions with space plasma. For more information on ELF/VLF wave generation with HAARP, see the online HAARP FAQ at
https://haarp.gi.alaska.edu/faq.
Note that numerous experiments will operate at frequencies based on the f0F2 frequency from the
Gakona ionograms. Experiments that are dependent on f0F2 will typically operate 0.5-1 MHz below
f0F2 at the time of transmission. There are no specific data collection requests from funded
investigators, but reception reports are appreciated and may be submitted to uaf-gihaarp AT alaska DOT edu or to: HAARP, PO Box 271, Gakona, AK 99586
The image above is an annotated ionogram from HAARP that describes features that may be of
interest. Note that f0F2 is calculated at the top left.
f0F2 is the critical frequency of the F2 layer of the Earth’s ionosphere. This is the frequency at
which radio signals stop refracting off the ionosphere and begin passing through to outer space.
For certain HAARP experiments that deal with interactions in the ionosphere, transmission
frequencies below f0F2 are desirable, while for other experiments (such as those involving high altitude satellites), staying above f0F2 is required.
