Generation of Artificial Acoustic-Gravity Waves and Traveling Ionospheric Disturbances in HF Heating Experiments

Abstract

We report the results of our ionospheric HF heating experiments to generate artificial acoustic-gravity waves (AGW) and traveling ionospheric disturbances (TID), which were conducted at the High-frequency Active Auroral Research Program facility in Gakona, Alaska. Based on the data from UHF radar, GPS total electron content, and ionosonde measurements, we found that artificial AGW/TID can be generated in ionospheric modification experiments by sinusoidally modulating the power envelope of the transmitted O-mode HF heater waves. In this case, the modulation frequency needs to be set below the characteristic Brunt-Vaisala frequency at the relevant altitudes. We avoided potential contamination from naturallyoccurring AGW/TID of auroral origin by conducting the experiments during geomagnetically quiet time period. We determine that these artificial AGW/TID propagate away from the edge of the heated region with a horizontal speed of approximately 160 m/s.

Ionosonde observations of ionospheric disturbances due to the 15 February 2013 Chelyabinsk meteor explosion

“…Based on the time delays and the great circle distances from Chelyabinsk, we have inferred the overall propagation speed to be 171 ± 14 m/s. This inferred speed very much agrees with the typical propagation speed of medium‐scale TIDs (MSTIDs) from various natural and/or artificial sources [ Ogawa et al , ; Tsugawa et al , ; Pradipta et al , ].…”

“…It is also generally accepted that large‐scale TIDs propagate at a significantly higher velocity (and survive a longer propagation distance) than smaller‐scale TIDs [see, e.g., Francis , ]. For the most part, the speed inferred in this analysis (∼171 m/s) is closer to the typical propagation speed of medium‐scale TIDs (MSTIDs) from natural as well as artificial sources [ Ogawa et al , ; Tsugawa et al , ; Pradipta et al , ].…”

Ionospheric Density Irregularities, Turbulence, and Wave Disturbances During the Total Solar Eclipse Over North America on 21 August 2017

“…Based on other related works, there are theoretical grounds for eclipse-related AGW/TID. Temperature gradients that formed around the path of the eclipse might act as a source of AGW/TID, similar to the way AGW/TID can be generated by the solar dawn/dusk terminators (Galushko et al, 1998;Liu et al, 2009), by anomalous temperature gradients associated with extreme heat wave events (Pradipta et al, 2017) or by time-varying temperature gradients artifically induced during ionospheric high-frequency (HF) heating experiments (Kunitsyn et al, 2012;Mishin et al, 2012;Pradipta, Lee et al, 2015). It is also important to note that the lunar shadow during a solar eclipse (∼110 km in diameter) typically traverses at a supersonic speed (600-1,500 m/s)-faster than the propagation velocity of small-scale or medium-scale TIDs (see, e.g., Ding et al, 2011).…”

Radiotomography and HF ray tracing of the artificially disturbed ionosphere above the Sura heating facility

“…These structures are 60–110 km in crossfield direction with the relative increase of electron density ~20–40% [ Rapoport et al , ; Frolov et al , , ; Milikh et al , ; Milikh et al , ]. Moreover, theoretical studies [ Grigor'ev , ; Grigor'ev and Trakhtengerts , ] and recent experiments [ Burmaka et al , ; Chernogor et al , ; Mishin et al , ; Kunitsyn et al , ; Pradipta et al , ] show that a periodic modification of the ionosphere by high‐power O‐mode HF radio wave where the effective radiated power (ERP) is modulated by a meander with frequency below or of the order of the Brunt‐Vaisala frequency at the ionospheric heights leads to the generation of traveling ionospheric disturbances (TIDs) associated with acoustic‐gravity waves (AGWs) with rather high amplitudes, which can be detected at farther distances up to ~1000 km away from the heater. These irregularities can significantly affect HF propagation in this region.…”