@proceedings {829, title = {Plans to Observe Changes to the Ionosphere During the April 8 Eclipse Using Doppler Shifts of AM Broadcast Stations}, year = {2024}, month = {03/2024}, publisher = {HamSCI}, address = {Cleveland, OH}, abstract = {

Variations in the ionosphere can be tracked by observing the Doppler-shifted carriers of clear-channel AM broadcast stations.\  An expansive system of receivers using Software-Defined Radios, frequency stabilized by GPS is being deployed to collect data in the eastern United States.\  This network is expected to be able to detect and track changes due to the shadow of the April 8, 2024 Total Eclipse of the Sun.

}, author = {David McGaw and James LaBelle and John Griffin and Terrence Kovacs and Margaret Klein and Jack Bonneau and Justin Lewis and Jackson Gosler} } @proceedings {719, title = {An Expanded System to Track Traveling Ionospheric Disturbances and Other Effects Using Doppler-shifts of AM Broadcast Stations}, year = {2023}, month = {03/2023}, publisher = {HamSCI}, address = {Scranton, PA}, abstract = {

Traveling Ionospheric Disturbances, propagating variations in the ionosphere, can be tracked by observing the Doppler-shifted carriers of clear-channel AM broadcast stations.\  A system of receivers using Software-Defined Radios frequency stabilized by GPS has been developed, deployed and collecting data in the northeast United States.\  The existing system of 6 receivers will be built out to as many as 15 to cover much of the eastern US.\  This expanded network promises to be able to detect and track these TIDs as well as terminator, Spread-F and eclipse effects.

}, author = {David McGaw and Jackson Gosler and Justin Lewis and James LaBelle} } @proceedings {703, title = {Observing Auroral Radio Emissions in Conjugate Hemispheres}, year = {2023}, month = {03/2023}, publisher = {HamSCI}, address = {Scranton, PA}, abstract = {

In addition to its beautiful optical displays, the aurora produces radio emissions of various types, including cyclotron harmonic emissions, auroral hiss, medium frequency burst (MFB), and auroral kilometric radiation (AKR). These emissions enable remote sensing of ionospheric processes and provide a natural laboratory for studying physics of radio emissions that also occur in planetary, solar, and astrophysical environments. Similar to the optical aurora, these radio emissions are generated separately in the northern and southern hemispheres. Nevertheless, optical aurora sometimes exhibit similar features simultaneously in the two hemispheres because aurora in both hemispheres are ultimately driven by the interaction between the solar wind and the magnetosphere. The same should be true of radio emission. At very low frequencies (VLF), auroral hiss has previously been detected at conjugate observatories in Iceland and Antarctica, and satellite-borne radio receivers have observed AKR simultaneously emanating from conjugate sources; however, the other types of radio emission have never been studied at both ends of a magnetic field line. To accomplish this, LF/MF/HF radio receivers have recently been installed at Qikiktarjuaq and Iqaluit, Nunavut, observatories of the Canadian High Arctic Ionospheric Network (CHAIN) which straddle the nominal magnetic conjugate point of South Pole Station, Antarctica, where Dartmouth College operates LF/MF/HF receivers. The Arctic observations employ a dedicated 10-m^2 magnetic loop antenna with active preamp, and a feed from the horizontal linear dipole antennas used for reception of CHAIN ionosonde signals. The Antarctic observations use magnetic loops of areas 2.5-40 m^2 depending on frequency range. Both systems have collected data since October, 2022. Conjugate auroral hiss events have been detected in both equinoctial and solstice conditions. In the latter case, the hiss observed in the daylit hemisphere was weaker than that in the dark ionosphere. Based on initial data, the characteristics and seasonal dependence of conjugate LF auroral hiss appears consistent with previous observations at VLF. Many hiss and cyclotron harmonic emissions have been observed in one hemisphere but not the other. Upcoming 2023 Spring equinox will bring a period of simultaneous darkness at South Pole and Qikiktarjuaq ideal for conjugate medium frequency burst and cyclotron harmonic emissions.

}, author = {James LaBelle and David McGaw and T. Kovacs and A. Kashcheyev and P.T. Jayachandran} } @proceedings {623, title = {Broadband Loop Antennas and Preamplifiers for Receiving VLF to HF}, year = {2022}, month = {03/2022}, publisher = {HamSCI}, address = {Huntsville, AL}, abstract = {

Wire loop antennas have been used to receive natural and man-made signals over wide bands from 100kHz to 10MHz.\  This talk will cover size considerations and preamplifier design.

}, author = {David McGaw and Mike Trimpi and James LaBelle} } @proceedings {464, title = {Traveling ionospheric disturbances tracked through Doppler-shifted AM radio transmissions}, year = {2021}, month = {03/2021}, publisher = {HamSCI}, address = {Scranton, PA (Virtual)}, abstract = {

A comprehensive understanding of the ionosphere is critical for many technologies, particularly those that rely on the propagation of radio waves. This study shows that traveling ionospheric disturbances (TIDs), dawn and dusk signal divergence (terminators), and spread F\ can be tracked and analyzed using clear channel AM radio transmissions and a set of geographically distributed receivers. Early attempts by our research group to track TIDs by AM radio signals reflected from the F region of the ionosphere generated results in conflict with those derived from GPS/TEC mapping methods [Chilcote et al., 2015]. This study seeks to resolve those conflicts with a more sophisticated array of receivers spread throughout the northeastern United States. Specifically, the receivers form a ring around an 810 kHz AM radio station in Schenectady, New York. A minimum of four receivers have been operational from 3/19/20 to the present and Doppler-shifted signals, attributed to TID events, have been consistently visible across several radio channels with frequencies between 800 to 1600kHz. We have focused our study thus far on the terminator signals which appear to be consistent with photochemistry effects and on TID wave characteristic analysis. We have collected a set of exceptional TID events over the past nine months and have correlated our calculated wave characteristics with the data from GNSS TEC, digisonde, and SuperDARN in general finding good agreement between our technique and these established methods. While our study still seeks to clarify discrepancies in our data similar to those seen by Chilcote in the original study, the consistency with which our data typically agrees with other methods supports the validity of using AM radio transmissions to track TIDs in addition to other ionospheric phenomena such as the terminator.\ 

Reference: Chilcote, M., et al. (2015), Detection of traveling ionospheric disturbances by medium-frequency Doppler sounding using AM radio transmissions, Radio Sci., 50, doi:10.1002/2014RS005617.

}, author = {Claire C. Trop and James LaBelle and Philip J. Erickson and Shunrong Zhang and David McGaw and Terrence Kovacs} }