SPA-Aeronomy [SA]
SA53C ACC:13 Friday
Applications of High-Power Ionospheric Modification to Studies of Plasma Physics and Magnetosphere-Ionosphere Coupling II
Presiding: D M Wright, Univ. of Leicester; M Kosch, Lancaster Univ.
SA53C-01 INVITED
ELF/VLF Wave-injection Experiments with HAARP
* Inan, U S (
inan@stanford.edu), Stanford University, Packard Bldg., Rm. 355, 350 Serra Mall, Stanford University, CA 94305, United States
The potential use of modulated HF heating of the lower ionosphere as a means to generate ELF/VLF waves has long been recognized. Located conveniently at L ≅ 4.9, thus lying on closed sub-auroral field lines most of the time, the High-Frequency Active Auroral Research Program (HAARP) heater in Gakona, Alaska is well positioned for the conduct of ELF/VLF wave-injection experiments for magnetospheric wave-particle interaction studies. Early results (2004) have alreay demonstrated that whistler-mode wave amplification can be initiated by ELF/VLf signals injected from HAARP, leading to multiple-hop propagation of signals between hemispheres and triggering of discrete emissions. With the upcomign completion of the upgrade of HAARP to full power (3.6 MW radiated), a new set of experiments have become possible, and the first opportunity for the conduct of such experiments is now before us. During February 23-March 6th, Stanford University personnel will be deploying two large Buoys equipped with ELF/VLF erceivers in the geomagneticaly conjugate region of HAARP, and will also conduct continuous ELF/VLF observations on the research ship which will deploy them. The experiments are aimed at generating specially designed ELF/VLF modulation formats, for initiation of wave growth, emission triggering and excitation of one-hop and two-hop whistler-mode waves. ELF/VLf observations will be conducted on teh ship and buoys near the conjugate region, but also on several distributed sites in Alaska as well as on teh DEMETER spacecraft. In this paper, we will discuss these experiments and present initial results from them. This papers constitutes a brief summary of the extensive work contributed by many other not-listed authors, at Stanford University, at AFRL, ONR, and at LPCE/CNRS in Orleans. The presenter listed as the single author is simply the team leader, listed solely for purposes of brevity.
SA53C-02
First Observations of Artificially-Generated ULF Magnetic Pulsations at HAARP
* Parent, A (
aparent@phys.ualberta.ca), University of Alberta, Department of Physics Room #238 CEB 11322-89 Avenue, Edmonton, AB T6E1P4, Canada
Mann, I R (
imann@phys.ualberta.ca), University of Alberta, Department of Physics Room #238 CEB 11322-89 Avenue, Edmonton, AB T6E1P4, Canada
Kosch, M (
m.kosch@lancaster.ac.uk), Lancaster University, Department of Communication Systems InfoLab21, Lancaster, LA14WA, United Kingdom
McCarrick, M (
mike.mccarrick@baesystems.com), BAE Systems, Washington, DC, United States
Pedersen, T (
todd.pedersen@hanscom.af.mil), Air Force Research Laboratory, Space Vehicles Directorate Hanscom AFB, MA 01731, United States
Hayashi, K (
hayashi@geoph.s.u-tokyo-ac.jp), University of Tokyo (retired), 3-30-11 Ohtsugaoka, Chiba, 277-0921, Japan
Over three separate intervals, active ionospheric heating experiments with ULF-modulated power in the 0.1 to 5.0 Hz range were conducted at the HAARP HF heater facility near Gakona, Alaska. On August 23, 2005, 3.2 MHz heating was carried out from 02:45 to 05:00 UT. During the active experiments of March 20 and 21, 2006, a 3.04 MHz frequency was used to heat between 05:00 and 10:00 UT. Each of the intervals involved ULF-modulation of the heater power in repeating sequences that stepped through frequencies starting at 0.1 Hz and ending on 3.0 to 6.0 Hz. Analysis of data from the 10 Hz ground-based search coil magnetometer located at HAARP during each experimental interval indicates the presence of ULF wave signals with frequencies that match the stepped ULF modulation frequencies of the heater power. The search coil instrument is located close (less than 2 km) to the heater array, which means caution must be taken in interpreting the results as an ionospheric signal. However, the magnetic ULF wave signal power varies strongly in the H and D components throughout each experiment as the stepped modulation frequency sequences are repeated, and signal amplitude is also observed to increase significantly during a narrow-band structured Pc1 pearl event that developed during the experiment of March 21, 2006. This suggests that conditions in the ionosphere changed, making them more amenable to artificial generation of ULF waves. Using the magnetometer data and other ionospheric diagnostic instruments, we present the case that the waves observed at HAARP were generated actively by ionospheric modification over the intervals described above. The results suggest that future opportunities to repeat similar ULF experiments at HAARP should include the additional deployment of multiple search coils in a wider area surrounding the heating facility. Beyond our interest in investigating the processes involved in generating artificial ULF waves in the ionosphere, future experiments will focus upon attempting to actively produce ULF waves that may stimulate the Ionospheric Alfven Resonator (IAR).
SA53C-03
Strong ionospheric perturbations generated by powerful VLF ground-based transmitters
* Parrot, M (
mparrot@cnrs-orleans.fr), LPCE/CNRS, 3A Avenue de la Recherche Scientifique, Orleans, 45071, France
Sauvaud, J (
sauvaud@cesr.fr), CESR/CNRS, 9 avenue du Colonel Roche, Toulouse, 31028, France
Berthelier, J (
jean-jacques.berthelier@cetp.ipsl.fr), CETP, Observatoire de Saint Maur, 4 Avenue de Neptune, Saint Maur des Fosse, 94107, France
Lebreton, J (
Jean-Pierre.Lebreton@esa.int), ESA/ESTEC, Research and Scientific Support Department, Noordwijk, Netherlands
This paper is related to the first in-situ observations of strong ionospheric perturbations close to powerful VLF transmitters. NWC in Australia is one of the most powerful VLF transmitters in the world and it is located at a low L-shell value (L=1.49). Waves and plasma parameters are recorded by the low orbiting satellite DEMETER. Electrostatic waves from HF to ELF ranges are generated and strong turbulence appears. Fluctuations of electron and ion densities are observed as well as increase of temperature. The perturbations are well located to the geographic North of the transmitter and cover a surface of ~ 500,000 km2. This area is centred at the altitude of the satellite (700 km) around the magnetic field line which has a foot at the location of the transmitter. This phenomenon is due to the electron and ion heating of the ionosphere induced by the powerful transmitter VLF wave. A much smaller effect is also observed in the Northern hemisphere at the conjugated location. This ionospheric perturbation observed for the first time is in addition to the already known precipitation of the energetic particles which interact with the VLF wave of the transmitter through a cyclotron resonance mechanism. NAA in US which has the same power as NWC is located at a much higher L value (3.0). Ionospheric perturbations from this transmitter is also detected although intense natural noise is present in this sub-auroral area.
SA53C-04
On the initial perturbation of mesospheric dust associated irregularities by high powered radio waves
* Chen, C (
chenc@vt.edu), Virginia Tech, 302 Whittemore Hall (0111), Blacksburg, VA 24060, United States
Scales, W (
wscales@vt.edu), Virginia Tech, 302 Whittemore Hall (0111), Blacksburg, VA 24060, United States
Important observational manifestations of subvisible mesospheric dust are Polar Mesospheric Summer Echoes PMSE which are produced by scattering from electron irregularities produced by dust charging. It has been observed that the PMSE strength can be artificially modified by using a ground-based ionospheric heating facility to perturb the electron irregularity source region that is believed to produce PMSE. Recently it has become evident that significant diagnostic information may be available about the dust layer from the temporal behavior of the electron irregularities during the heating process which modifies the background electron temperature. Particularly interesting and important periods of the temporal behavior are during the turn-on and turn-on of the radio wave heating. Most past theoretical models and experimental investigations have concentrated primarily on the later period. The objective here is to consider the temporal behavior and possibilities for diagnostic information available during the turn-on period of the radio wave. First, approximate analytical models are developed and compared to a more accurate full computational model as a reference. Then from the temporal behavior of the electron irregularities during the turn-on of the radio wave, the analytical models are used to obtain possible diagnostic information for various charged dust and background plasma quantities. First experimental campain was performed last summer in HAARP, Gakona, AK. Preliminary measurment results show very promising application of the theory.
SA53C-05 INVITED
Capabilities of and Results From the SPEAR Ionospheric Heating Facility
* Yeoman, T K (
tim.yeoman@ion.le.ac.uk), University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom
Robinson, T R (
txr@ion.le.ac.uk), University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom
Dhillon, R S (
rsd6@ion.le.ac.uk), University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom
Wright, D M (
dmw7@ion.le.ac.uk), University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom
Baddeley, L J (
ljb14@ion.le.ac.uk), University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom
The SPEAR (Space Plasma Exploration by Active Radar) high power radio frequency system at 78 degrees north on Svalbard started operations in 2004. Several campaigns coordinated with the EISCAT Svalbard Radar (ESR) have been run since that time. The capabilities of the SPEAR system have been extended during each campaign, and the current capabilities of the system will be described, along with the plans for the development of the system over the next few years. The results of high power ionospheric modification experiments performed with SPEAR in coordination with both the ESR, the CUTLASS HF coherent radars and HF Doppler experiments during the first years of operations will be summarised, and future experimental plans outlined.
SA53C-06
Power Thresholds of SPEAR-induced Irregularities at Very High Latitudes
* Wright, D M (
Darren.Wright@ion.le.ac.uk), Radio and Space Plasma Physics Group, Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom
Yeoman, T K (
yxo@ion.le.ac.uk), Radio and Space Plasma Physics Group, Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom
Robinson, T R (
txr@ion.le.ac.uk), Radio and Space Plasma Physics Group, Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom
Thomas, E C (
ect@ion.le.ac.uk), Radio and Space Plasma Physics Group, Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom
Baddeley, L J (
ljb14@ion.le.ac.uk), Radio and Space Plasma Physics Group, Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom
Dhillon, R S (
rsd6@ion.le.ac.uk), Radio and Space Plasma Physics Group, Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom
SPEAR (Space Plasma Exploration by Active Radar) is a high power facility uniquely located to study the plasma physics and geophysics of the very high latitude magnetosphere and ionosphere. Recently, experiments have been undertaken to investigate the power thresholds required to excite field-aligned irregularities (FAIs). The artificially stimulated FAI act as intense targets in the fields of view of the CUTLASS HF coherent radar pair. Data derived using this artificial backscatter technique demonstrate that SPEAR effective radiated powers (ERPs) of the order of 1 MW or less are capable of initiating the formation of the FAI. This represents only 1/30th of the heating capability of SPEAR. Ionospheric hysteresis was also observed to occur during the experiments. This relates to the nature of the instability which leads to their excitation.
http:www.ion.le.ac.uk/spear
SA53C-07
The Future of HF-Interaction Experiments at EISCAT
* Rietveld, M T (
mike.rietveld@eiscat.uit.no), EISCAT Scientific Association, Tromso, Ramfjordbotn, 9027, Norway
The EISCAT HF facility, co-located with two incoherent scatter radars, has some of the best diagnostics available for doing research in plasma physics and actively probing the ionosphere, upper atmosphere and magnetosphere. The facility is presently undergoing some improvements which will keep it at the forefront of such research. Direct digital synthesis of the HF wave will allow fast changes of frequency and beam direction, and increased flexibility in pulsing. Some of the more important recent results are outlined, and the directions for further progress are suggested. These results include the effect of electron heating on the charging of mesospheric dust which changes the strength of VHF radar echoes from the polar summer mesosphere. Other results involve Langmuir and thermal plasma instabilities from the F region which show a rich variety of dependences on pumping frequency and direction to the Earth's magnetic field. Some of the geometrical effects observed in plasma line observations and artificial optical emissions remain largely unexplained.
Authors (2007), Title, Eos Trans. AGU, 88(23), Jt. Assem. Suppl., Abstract xxxxx-xx