@proceedings {644, title = {An Overview of Oblique Soundings from Chirp Ionosondes}, year = {2022}, month = {03/2022}, publisher = {HamSCI}, address = {Huntsville, AL}, abstract = {

An ionospheric sounder, typically known as an ionosonde, is a radar device which is used to make observations of the ionized layer of the Earth{\textquoteright}s upper atmosphere known as the ionosphere. The ionosonde works by transmitting high frequency (HF, 3-30 MHz) radio waves and observing the time delay of the ionospheric echoes. Ionosondes play an especially crucial role in our understanding both ionospheric dynamics and how radio wave propagation is impacted by the ionosphere. The data from an ionosonde is displayed in a type of plot known as an ionogram. A chirp ionosonde is a type of ionospheric sounder that produces ionograms by transmitting an HF signal that changes linearly in frequency with time. Conventional chirp ionosondes are used in a vertical sounding mode, in which signals are transmitted directly up to the ionosphere. This allows for measurements of electron density as a function of height for the bottomside ionosphere. Chirp ionosondes may also be used in an oblique sounding configuration, in which the transmitter and receiver are separated by a significant geographic distance. While the measurements of an oblique sounder are more complicated to interpret than a vertical sounder, a single transmitter can be used simultaneously by receivers in many different locations, thus allowing for a cost-effective increase in the number of ionospheric sampling points. The HamSCI Personal Space Weather Station plans to take advantage of this fact by using signals-of-opportunity from the global network of pre-existing chirp ionosonde transmitters. In this presentation, we give a brief overview of chirp ionosondes and their uses in studying ionospheric dynamics.

}, author = {Simal Sami and Nathaniel A. Frissell and Mary Lou West and Dev Raj Joshi and Juha Vierinen} } @conference {536, title = {Observations of Mid-latitude Irregularities Using the Oblique Ionosonde Sounding Mode for the HamSCI Personal Space Weather Station}, booktitle = {NSF CEDAR (Coupling, Energetics, and Dynamics of Atmospheric Regions)}, year = {2021}, month = {06/2021}, publisher = {CEDAR}, organization = {CEDAR}, address = {Virtual}, abstract = {

The spread in the echoes of high-frequency (HF, 3-30 MHz) radio waves from the F-region of the ionosphere has been the earliest indication of plasma density irregularities in the mid-latitude F region ionosphere. Although mid-latitude spread F has been widely studied, the plasma instability mechanisms for these irregularities are still largely unknown. This phenomenon can cause radio wave scintillation effects that degrade the performance of man-made technologies such as satellite communications and global navigation satellite systems (GNSS). Understanding these irregularities so that they can be anticipated and mitigated are important aspects of space weather research. The occurrence climatology and variability can also be helpful in modeling efforts of these irregularities. Here, we present signatures of mid-latitude irregularities observed in oblique ionograms received near Scranton, PA transmitted by the Relocatable Over-the-Horizon Radar (ROTHR) in Chesapeake, Virginia. These observations are collected with the GNU Chirpsounder2 software, an open-source software package capable of creating ionograms from frequency modulated (FM) chirp ionosondes. This ionospheric sounding mode will be implemented in the currently under development Ham Radio Science Citizen Investigation (HamSCI) Personal Space Weather Station (PSWS), a ground-based multi-instrument system designed to remote-sense the ionosphere using signals of opportunity.

}, author = {Dev Joshi and Nathaniel A. Frissell and William Liles and Juha Vierinen} }