@proceedings {459, title = {Estimation of Ionospheric Layer Height Changes From Doppler Frequency and Time of Flight Measurements on HF Skywave Signals}, year = {2021}, month = {03/2021}, publisher = {HamSCI}, address = {Scranton, PA (Virtual)}, abstract = {

The HamSCI community has been studying apparent frequency shifts in the reception of HF skywave signals from radio station WWV in Ft. Collins, CO. WWV is a standard time and frequency station with atomic clock accuracy. If the receiving station uses a GPS Disciplined Oscillator (GPSDO) for a frequency reference, the atomic clock accuracy on both ends guarantees any observed frequency shifts are attributable only to propagation effects through the ionosphere. Causes for frequency shifts in the received signal are recognized as complex and varied. A leading candidate is Doppler shift resulting from dynamic changes in refraction layer height. These, in turn, are caused by the diurnal transitions between night and day, passage of an eclipse shadow, and ionospheric disturbances originating from solar flares or X-ray events. For the case of changing refraction layer height, an analysis of Doppler frequency and Time of Flight (TOF) data can estimate the changes in skywave path length between the transmitter and receiver.\  This data can be used in conjunction with an assumed geometric model and propagation mode to infer the corresponding height profile over time. This paper postulates one possible mechanism for observed frequency swings and presents supporting experimental evidence. Comparisons between the calculated\  height profile derived from Doppler data and data from ray trace programs and ionosonde measurements are given.

}, author = {Steven Cerwin and Kristina V. Collins and Dev Joshi and Nathaniel A. Frissell} } @conference {540, title = {HamSCI Personal Space Weather Station (PSWS): Architecture and Current Status}, booktitle = {NSF CEDAR (Coupling, Energetics, and Dynamics of Atmospheric Regions)}, year = {2021}, month = {06/2021}, publisher = {CEDAR}, organization = {CEDAR}, address = {Virtual}, abstract = {

Recent advances in geospace remote sensing have shown that large-scale distributed networks of ground-based sensors pay large dividends by providing a big picture view of phenomena that were previously observed only by point-measurements. While existing instrument networks provide excellent insight into ionospheric and space science, the system remains undersampled and more observations are needed to advance understanding. In an effort to generate these additional measurements, the Ham Radio Science Citizen Investigation (HamSCI, hamsci.org) is working with the Tucson Amateur Packet Radio Corporation (TAPR, tapr.org), an engineering organization comprised of volunteer amateur radio operators and engineers, to develop a network of Personal Space Weather Stations (PSWS). These instruments that will provide scientific-grade observations of signals-of-opportunity across the HF bands from volunteer citizen observers as part of the NSF Distributed Array of Small Instruments (DASI) program. A performance-driven PSWS design (~US$500) will be a modular, multi-instrument device that will consist of a dual-channel phase-locked 0.1-60 MHz software defined radio (SDR) receiver, a ground magnetometer with (~10 nT resolution and 1-sec cadence), and GPS/GNSS receiver to provide precision time stamping and serve as a GPS disciplined oscillator (GPSDO) to provide stability to the SDR receiver. A low-cost PSWS (\< US$100) that measures Doppler shift of HF signals received from standards stations such as WWV (US) and CHU (Canada) and includes a magnetometer is also being developed. HF sounding algorithms making use of signals of opportunity will be developed for the SDR-based PSWS. All measurements will be collected into a central database for coordinated analysis and made available for public access.

}, author = {Nathaniel A. Frissell and Dev Joshi and Veronica I. Romanek and Kristina V. Collins and Aidan Montare and David Kazdan and John Gibbons and William D. Engelke and Travis Atkison and Hyomin Kim and Scott H. Cowling and Thomas C. McDermott and John Ackermann and David Witten and Julius Madey and H. Ward Silver and William Liles and Steven Cerwin and Philip J. Erickson and Ethan S. Miller and Juha Vierinen} } @conference {539, title = {HF Doppler Observations of Traveling Ionospheric Disturbances in a WWV Signal Received with a Network of Low-Cost HamSCI Personal Space Weather Stations}, booktitle = {NSF CEDAR (Coupling, Energetics, and Dynamics of Atmospheric Regions)}, year = {2021}, month = {06/2021}, publisher = {CEDAR}, organization = {CEDAR}, address = {Virtual}, abstract = {

Traveling Ionospheric Disturbances (TIDs) are quasi-periodic variations in ionospheric electron density that are often associated with atmospheric gravity waves. TIDs cause amplitude and frequency variations in high frequency (HF, 3-30 MHz) refracted radio waves. We present observations of TIDs made with a network of Ham Radio Science Citizen Investigation (HamSCI) Low-Cost Personal Space Weather Stations (PSWS) with nodes located in Pennsylvania, New Jersey, and Ohio. The TIDs were detected in the Doppler shifted carrier of the received signal from the 10 MHz WWV frequency and time standard station in Fort Collins, CO. Using a lagged cross correlation analysis, we demonstrate a method for determining TID wavelength, direction, and period using the collected WWV HF Doppler shifted data.

}, author = {Veronica I. Romanek and Nathaniel A. Frissell and Dev Joshi and William Liles and Clair Trop and Kristina Collins and Gareth Perry} } @proceedings {458, title = {Mid-latitude Irregularities in the Early Results from the Ionospheric Sounding Mode Using Chirp Ionosondes of Opportunity for the HamSCI Personal Space Weather Station}, year = {2021}, month = {03/2021}, publisher = {HamSCI}, address = {Scranton, PA (Virtual)}, abstract = {

The objective of the Ham Radio Science Citizen Investigation (HamSCI) Personal Space Weather Station (PSWS) project is to develop a distributed array of ground-based multi-instrument nodes capable of remote sensing the geospace system. This system is being designed with the intention of distribution to a large number of amateur radio and citizen science observers. This will create an unprecedented opportunity to probe the ionosphere at finer resolution in both time and space as all measurements will be collected into a central database for coordinated analysis. Individual nodes are being designed to service the needs of the professional space science researcher while being cost-accessible and of interest to amateur radio operators and citizen scientists. At the heart of the HamSCI PSWS will be a high performance 1 {\textendash} 50 MHz software defined radio (SDR) with GNSS-based precision timestamping and frequency reference. This SDR is known as the TangerineSDR and is being developed by the Tucson Amateur Packet Radio (TAPR) amateur radio organization. The primary objective of PSWS system is to gather observations to understand the short term and small spatial scale ionospheric variabilities in the ionosphere-thermosphere system. These variabilities are important for understanding a variety of geophysical phenomena such as Traveling Ionospheric Disturbances (TIDs), Ionospheric absorption events, geomagnetic storms and substorms. We present early results suggesting signatures of Traveling Ionospheric Disturbances (TIDs) from an ionospheric sounding mode that we intend to implement on the PSWS system, currently implemented on an Ettus N200 Universal Software Radio Peripheral (USRP) using the open source GNU Chirpsounder data collection and analysis code.

}, author = {Dev Joshi and Nathaniel A. Frissell and William Liles and Juha Vierinen and Ethan S. Miller} } @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} } @conference {542, title = {Sources of Large Scale Traveling Ionospheric Disturbances Observed using HamSCI Amateur Radio, SuperDARN, and GNSS TEC}, booktitle = {NSF CEDAR (Coupling, Energetics, and Dynamics of Atmospheric Regions)}, year = {2021}, month = {06/2021}, publisher = {CEDAR}, organization = {CEDAR}, address = {Virtual}, abstract = {

Large Scale Traveling Ionospheric Disturbances (LSTIDs) are quasi-periodic variations in F region electron density with horizontal wavelengths \> 1000 km and periods between 30 to 180 min. On 3 November 2017, LSTID signatures were detected in simultaneously over the continental United States in observations made by global High Frequency (HF) amateur (ham) radio observing networks and the Blackstone (BKS) SuperDARN radar. The amateur radio LSTIDs were observed on the 7 and 14 MHz amateur radio bands as changes in average propagation path length with time, while the LSTIDs were observed by SuperDARN as oscillations of average scatter range. LSTID period lengthened from T ~ 1.5 hr at 12 UT to T ~ 2.25 hr by 21 UT. The amateur radio and BKS SuperDARN radar observations corresponded with Global Navigation Satellite System differential Total Electron Content (GNSS dTEC) measurements. dTEC was used to estimate LSTID parameters: horizontal wavelength 1136 km, phase velocity 1280 km/hr, period 53 min, and propagation azimuth 167{\textdegree}. The LSTID signatures were observed throughout the day following ~400 to 800 nT surges in the Auroral Electrojet (AE) index. As a contrast, 16 May 2017 was identified as a period with significant amateur radio coverage but no LSTID signatures in spite of similar geomagnetic conditions and AE activity as the 3 November event. We hypothesize that atmospheric gravity wave (AGW) sources triggered by auroral electrojet intensifications and associated Joule heating are the source of the LSTIDs, and that seasonal neutral atmospheric conditions may play a role in preventing AGW propagation in May but not in November.

}, author = {Nathaniel A. Frissell and Diego F. Sanchez and Gareth W. Perry and Dev Joshi and William D. Engelke and Evan G. Thomas and Anthea Coster and Philip J. Erickson and J. Michael Ruohoniemi and Joseph B. H. Baker} } @proceedings {478, title = {A Survey of HF Doppler TID Signatures Observed Using a Grape in New Jersey}, year = {2021}, month = {03/2021}, publisher = {HamSCI}, address = {Scranton, PA (Virtual)}, url = {https://hamsci2021-uscranton.ipostersessions.com/?s=6A-B6-94-74-A1-46-CF-D2-AC-BA-F3-58-2E-71-17-97}, author = {Veronica I. Romanek and Nathaniel A. Frissell and Dev Joshi and William Liles and Kristina Collins and John Gibbons and David Kazdan} }