NAIC/AO Newsletter, July 97
Several short HF campaigns are planned for 1997. The first has already taken place; it consisted of a single experiment with the purpose of detecting and studying artificial periodic irregularities in the D and E region. These irregularities are apparently caused by a powerful HF standing wave. The HF facility becomes an HF radar after a period of heating and is used to detect the irregularities and measure their decay time as has been done at facilities in the former Soviet Union, at EISCAT in Norway, and at HIPAS in Alaska. The first Arecibo measurements occurred the week of June 13,1997. A first look at the preliminary results shows layers in the E region, but surprisingly, not in the D region.
The next campaign begins in the middle of July; the subject is Langmuir turbulence. Several experiments will explore the physics governing the interaction of the HF wave with the narrow layer in the plasma near the O mode reflection height. Beginning about the third week of September, and depending on the availability of the telescope, three experiments will look in more detail at the behavior of artificial periodic irregularities in the D and E and F regions. More diagnostics, including the 430 MHz radar will be available.
Another campaign is slated to begin in mid-November. Most of the experiments in this campaign will use a 50 MHz radar to study the scatter from HF induced irregularities in the F region. This campaign will continue into December as a true winter campaign. The object of winter, solar minimum campaigns is to study large scale ionospheric depletions and the production of HF induced airglow. These experiments work best when the electron density is low in the F region; since solar activity is beginning to show signs of an increase, this coming winter might be the last opportunity to perform these experiments until the next solar minimum.
Finally, the HF facility will be used for one experiment in the rocket campaign which begins in January, 1998.