@proceedings {823, title = {Exploring Ionospheric Variability Through Doppler Residuals: A Study Utilizing the HamSCI Grape V1 Receiver}, year = {2024}, month = {03/2024}, publisher = {HamSCI}, address = {Cleveland, OH}, abstract = {

This study leverages the capabilities of the Grape V1 low-IF receiver to analyze both long and short-term patterns of high frequency (HF; 3-30 MHz) skywave signals. The HF spectrum, often used for global long-range communications, also spans the frequencies used for remote sensing of the near-Earth plasma environment. The Grape receiver (callsign K2MFF) used in this study is located at the New Jersey Institute of Technology (NJIT) in Newark, NJ. At a rate of 1 Hz, it samples its link to the WWV broadcasting station transmitting at 10 MHz from Fort Collins, CO. The Doppler shift in this radio link, caused by its interactions with the ionosphere, is measured to study fluctuations in the ionosphere{\textquoteright}s electron density. This methodology provides insight into the effects of geomagnetic activity on the terrestrial ionosphere, caused by complex processes in the coupled Sun-Earth plasma environment. Our results show that the signal received during the daytime is less prone to Doppler shift than when received during the nighttime. This night-day contrast is consistent across most 24-hour cycles, barring dates of antenna maintenance or severe geomagnetic storms. We also found a strong correlation between daytime measurements and Cauchy statistics, and between nighttime measurements and a mixture of exponential power / lognormal statistics, wherein day and night at the geographic midpoint between WWV and NJIT are considered. The identification of these differing statistical regimes per time of day has led us to characterize long-term trends in the dataset by the medians of day and night Doppler measurements, independently. Additionally, the receiver{\textquoteright}s sensitivity and versatility was affirmed through case-studies of atypical Doppler traces captured in the data stream, by identifying characteristic markers of solar flares and solar eclipses.

}, author = {Sabastian Fernandes and Gareth W. Perry and Tiago Trigo and John Gibbons} } @proceedings {836, title = {Possible Drivers of Large Scale Traveling Ionospheric Disturbances by Analysis of Aggregated Ham Radio Contacts}, year = {2024}, month = {03/2024}, publisher = {HamSCI}, address = {Cleveland, OH}, abstract = {

Large Scale Traveling Ionospheric Disturbances (LSTIDs) are quasiperiodic electron density perturbations of the F region ionosphere that have periods of 30 min to over 180 min, wavelengths of over 1000 km, and velocities of 150 to 1000 m/s. These are seen as long slow oscillations in the bottom side of the ionosphere in data from ham radio contacts at 20 meters wavelength on roughly a third of the days in a year. They might be triggered by electromagnetic forces from above, and/or by mechanical pressures from below. The explosion of the Tonga volcano on January 15, 2022 revealed that such a LSTID could be triggered by a violent updraft from the Earth{\textquoteright}s surface into the stratosphere and then detected in the ionosphere over the United States nine hours later. We consider other possible drivers such as the auroral electrojet, the polar vortex, thunderstorms, zonal wind speeds, gravity wave variances, and their time derivatives in 2017.

}, author = {Diego Sanchez and Mary Lou West and Nathaniel A. Frissell and Gareth W. Perry and William D. Engelke and Robert B. Gerzoff and Philip J. Erickson and J. Michael Ruohoniemi and Joseph B. H. Baker and V. Lynn Harvey} } @proceedings {871, title = {Signatures of Space Weather in the NJIT V1 Grape Low-IF Receiver}, year = {2024}, month = {03/2024}, abstract = {

The V1 Grape Low Intermediate Frequency (Low-IF; 10 MHz) Receiver is part of a low-cost Personal Space Weather Station (PSWS) developed by the Ham Radio Science Citizen Investigation (HamSCI) Collective. One of the existing deployed Grapes is located at the New Jersey Institute of Technology (NJIT). The Grape measures the WWV 10 MHz signal originating from Fort Collins, Colorado. Variations in WWV{\textquoteright}s signal intensity and frequency, received by the Grape can be used to investigate\  strong space weather events and their effects on the Earth{\textquoteright}s ionosphere. The Grape data is separated into two parameters, Doppler Shift (Hz) which is a change in frequency introduced by the variability of the ionosphere along the WWV to NJIT link, and Relative Power (dB) which can be used as a proxy for the received signal{\textquoteright}s intensity.\  In this presentation, we will explore the possibility of using the Relative Power parameter for studying ionospheric scintillation due to space weather events.\  We will present several examples of data collected on days with known space weather events to assess the Grape{\textquoteright}s ability to detect the event. We will also discuss our analysis techniques, including our strategies to mitigate the local noise environment at NJIT, and future work.

}, author = {Tiago Trigo and Gareth W. Perry and Sebastian Fernandes and John Gibbons and Nathaniel A. Frissell} } @proceedings {734, title = {Climatology of Large Scale Traveling Ionospheric Disturbances Observed with Amateur Radio Networks}, year = {2023}, month = {03/2023}, publisher = {HamSCI}, address = {Scranton, PA}, abstract = {

A new climatology of Large Scale Traveling Ionospheric Disturbances (LSTIDs) has been observed from ham radio data in 2017. LSTIDs are quasiperiodic electron density perturbations of the F region ionosphere. LSTIDs have periods of 30 min to over 180 min, wavelengths of over 1000 km, and velocities of over 1400 km/hr. In this paper, we show a climatology of observed LSTID events using data from the Reverse Beacon Network (RBN), Weak Signal Propagation Network (WSPRNet), and PSKReporter amateur radio networks. This climatology was performed twice and was cross examined between two members of the research team. Results show that most of the observed LSTIDs occurred during the winter months with a decline towards the summer, with the exception of a spike in June. This paper provides additional insight into the seasonal trends of LSTIDs and provides additional knowledge that will help in the pursuit of what is causing this phenomenon.

}, author = {Diego Sanchez and Mary Lou West and Bob Gerzoff and Gareth W. Perry and Nathaniel A. Frissell and William D. Engelke and Philip J. Erickson} } @proceedings {693, title = {A Few Science Questions that HamSCI Can Help Address During the 2023 and 2024 Eclipses}, year = {2023}, month = {03/2023}, publisher = {HamSCI}, address = {Scranton, PA}, abstract = {

Solar eclipses are an exciting celestial event which can be used to study the terrestrial atmosphere and ionosphere systems. Locally, during a total solar eclipse, totality may only last a few minutes{\textemdash}and the times scales on which solar illumination decreases and then increases is much shorter that what is normally observed during sunrise and sunset. Additionally, on a larger, continental scale, the moon{\textquoteright}s umbra moves at supersonic velocities, tracing out the path of totality. These properties serve to act as an impulse in energy on the atmosphere and ionosphere, generating a wide variety of yet to be specified (or identified) responses in those systems.\ 

As an example of some compelling response effects, the fast depletion-replenishment of the bottomside ionosphere (the portion of the ionosphere that is below the F-region peak) often appears asymmetric{\textemdash}an observation that is not well understood. Therefore, one science question which can be addressed is: will the different geometries of the 2023 and 2024 eclipses as well as the fact that they are an annular and total eclipse, respectively, have a significant effect on the asymmetry of the bottomside evolution during the eclipse? Furthermore, efforts to model and replicate the observed effects of eclipses have significantly improved in recent years; however, observations of the atmosphere and ionosphere are still required to constrain, validate, and ultimately improve our theoretical understanding of these systems. Another eclipse science question which can be addressed is: how well will these models perform for the 2023 and 2024 eclipse and how can we quantify the response of the ionosphere during these events?\ 

Over the past few years, HamSCI has emerged at the forefront of passive remote sensing techniques in solar-terrestrial physics. This is evidenced by HamSCI{\textquoteright}s work using with HF timing signals and HF QSOs, show that both can be used to monitor the bottomside ionosphere on both regional and continental scales. The SEQP during the 2017 total solar eclipse was a resounding success, delivering high-impact and influential science results. Building upon that success, this technique may very well be a gamechanger for identifying and characterizing eclipse generated effects and phenomena during the upcoming 2023 and 2024 eclipses. The purpose of this presentation is to detail a few outstanding eclipse related science questions, and propose how HamSCI can lead the way in addressing them.

}, author = {Gareth W. Perry and Nathaniel A. Frissell and Joseph D. Huba} } @proceedings {764, title = {Medium Scale Traveling Ionospheric Disturbances and their Connection to the Lower and Middle Atmosphere}, year = {2023}, month = {03/2023}, publisher = {HamSCI}, address = {Scranton, PA}, author = {Nathaniel A. Frissell and Francis Tholley and V. Lynn Harvey and Sophie R. Phillips and Katrina Bossert and Sevag Derghazarian and Larisa Goncharenko and Richard Collins and Mary Lou West and Diego F. Sanchez and Gareth W. Perry and Robert B. Gerzoff and Philip J. Erickson and William D. Engelke and Nicholas Callahan and Lucas Underbakke and Travis Atkison and J. Michael Ruohoniemi and Joseph B. H. Baker} } @article {667, title = {Amateur Radio: An Integral Tool for Atmospheric, Ionospheric, and Space Physics Research and Operations}, journal = {White Paper Submitted to the National Academy of Sciences Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033}, year = {2022}, doi = {10.3847/25c2cfeb.18632d86}, author = {Nathaniel A. Frissell and Laura Brandt and Stephen A. Cerwin and Kristina V. Collins and David Kazdan and John Gibbons and William D. Engelke and Rachel M. Frissell and Robert B. Gerzoff and Stephen R. Kaeppler and Vincent Ledvina and William Liles and Michael Lombardi and Elizabeth MacDonald and Francesca Di Mare and Ethan S. Miller and Gareth W. Perry and Jonathan D. Rizzo and Diego F. Sanchez and H. Lawrence Serra and H. Ward Silver and David R. Themens and Mary Lou West} } @proceedings {628, title = {Climatology of Large Scale Traveling Ionospheric Disturbances Observed by HamSCI Amateur Radio with Connections to Geospace and Neutral Atmospheric Sources}, year = {2022}, month = {03/2022}, publisher = {HamSCI}, address = {Huntsville, AL}, abstract = {

Traveling Ionospheric Disturbances (TIDs) are propagating variations of F-region ionospheric electron densities that can affect the range and quality of High Frequency (HF, 3-30 MHz) radio communications. TIDs create concavities in the ionospheric electron density profile that move horizontally with the TID and cause skip-distance focusing effects for high frequency radio signals propagating through the ionosphere. TIDs are of great interest scientifically because they are often associated with neutral Atmospheric Gravity Waves (AGWs) and can be used to advance understanding of atmosphere-ionosphere coupling. Large scale TIDs (LSTIDs) have periods of 30-180 min, horizontal phase velocities of 100 - 250 m/s, and horizontal wavelengths of over 1000 km and are believed to be generated either by geomagnetic activity or lower atmospheric sources. The signature of this phenomena is manifest as quasi-periodic variations in contact ranges in HF amateur radio communication reports recorded by automated monitoring systems such as the Weak Signal Propagation Reporting Network (WSPRNet) and the Reverse Beacon Network (RBN). Current amateur radio observations are only able to detect LSTIDs. In this study, we present a climatology of LSTID activity using RBN and WSPRNet observations on the 1.8, 3.5, 7, 14, 21, and 28 MHz amateur radio bands from 2017. Results will be organized as a function observation frequency, longitudinal sector (North America and Europe), season, and geomagnetic activity level. Connections to geospace are explored via SYM-H and Auroral Electrojet indexes, while neutral atmospheric sources are explored using NASA{\textquoteright}s Modern-Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2).

}, author = {Diego S. Sanchez and Nathaniel A. Frissell and Gareth W. Perry and V. Lynn Harvey and William D. Engelke and Anthea Coster and Philip J. Erickson and J. Michael Ruohoniemi and Joseph B. H. Baker} } @article {670, title = {Fostering Collaborations with the Amateur Radio Community}, journal = {White Paper Submitted to the National Academy of Sciences Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033}, year = {2022}, doi = {10.3847/25c2cfeb.09fe22b4}, author = {Nathaniel A. Frissell and Laura Brandt and Stephen A. Cerwin and Kristina V. Collins and Timothy J. Duffy and David Kazdan and John Gibbons and William D. Engelke and Rachel M. Frissell and Robert B. Gerzoff and Stephen R. Kaeppler and Vincent Ledvina and William Liles and Elizabeth MacDonald and Gareth W. Perry and Jonathan D. Rizzo and Diego F. Sanchez and H. Lawrence Serra and H. Ward Silver and Tamitha Mulligan Skov and Mary Lou West} } @proceedings {637, title = {Potential Science Opportunities for HamSCI in Antarctica}, year = {2022}, month = {03/2022}, publisher = {HamSCI}, address = {Huntsville, AL}, abstract = {

The maturation and proliferation of passive radio receivers based on software defined radio principles and architecture herald a new era of radio remote sensing in solar-terrestrial physics. Antarctica is a region of interest for deploying HF radio receivers for many reasons. The significant offset of the geographic and magnetic poles allows one to study multiple terrestrial magnetosphere-ionosphere-thermosphere regions of interest, e.g., the polar, auroral, and sub-auroral zones, using ground-based instruments. Additionally, the significant snow and ice coverage in Antarctica is a strong absorber of HF radio waves. This severely mitigates intracontinental multi-hop propagation modes, which may be advantageous for geolocating geophysical features detected by HF radio techniques, thereby improving remote sensing performance. In this poster presentation, we will analyze a case of a QSO between two operators, captured by a receiver located at McMurdo Station in Antarctica. We will discuss the signal characteristics of each transmission and pay particularly close attention to how variations in the CW transmissions may be linked to geophysical processes occurring in the region at the time. The overarching goal of this presentation is to incite discussion on how existing and future passive HF receiving systems in Antarctica can leveraged to advance not only the art of radio but solar-terrestrial physics in Antarctica.

}, author = {Gareth W. Perry and Nathaniel A. Frissell} } @proceedings {622, title = {Properties and Drivers of Plasma Irregularities in the High-Latitude Ionosphere Computed using Novel Incoherent Scatter Radar Techniques}, year = {2022}, month = {03/2022}, publisher = {HamSCI}, address = {Huntsville, AL}, abstract = {

To provide new insights into the relationship between geomagnetic conditions and plasma irregularity scale-sizes, high-latitude irregularity spectra are computed using novel Incoherent Scatter Radar (ISR) techniques. This new technique leverages: 1) the ability of phased array Advanced Modular ISR (AMISR) technology to collect volumetric measurements of plasma density, 2) the slow F-region cross-field plasma diffusion at scales greater than 10 km, and 3) the high dip angle of geomagnetic field lines at high-latitudes. The resulting irregularity spectra are of a higher spatiotemporal resolution than has been previously possible with ISRs. Spatial structures as small as 20 km are resolved in less than two minutes (depending on the radar mode). In this work, we focus on Resolute Bay ISR observations operating in high-beam modes, such as the imaginglp mode. In addition to having an unprecedented view of the size and occurrence of irregularities as they traverse the polar cap, we find that near magnetic local noon the spectral power shifts to scales greater than 50 km, and from 15 to 5 magnetic local time the spectral power shifts to structures less than 50 km. This either reflects the role of polar cap convection in breaking down structures as they travel from the dayside ionosphere to the nightside, or the role of photoionization "smoothing" the dayside ionosphere. Additionally, during periods of enhanced geomagnetic conditions, such as periods with low AL indices, the spectral power shifts to structures 50 km and larger. This presentation will discuss these findings, as well as show seasonal variations.

}, author = {Lindsay V. Goodwin and Gareth W. Perry} } @conference {545, 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 = {Annual (Summer) Eastern Conference}, year = {2021}, month = {07/2021}, publisher = {Society of Amateur Radio Astronomers (SARA)}, organization = {Society of Amateur Radio Astronomers (SARA)}, 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. One way to detect TIDs is through the use of a Grape Personal Space Weather Station (PSWS). The Grape PSWS successfully detected TIDs in the Doppler shifted carrier of the received signal from the 10 MHz WWV frequency and time standard station in Fort Collins, CO. This paper will present an explanation of how the Grape PSWS was used to collect data, and how scientist can use this data to further investigate the ionosphere.

}, url = {https://rasdr.org/store/books/books/journals/proceedings-of-annual-conference}, author = {Veronica I. Romanek and Nathaniel A. Frissell and Dev Raj Joshi and William Liles and Claire C. Trop and Kristina V. Collins and Gareth W. Perry} } @proceedings {495, title = {K2MFF: Nearly a Century of Advancing the Radio Art at NJIT}, year = {2021}, month = {03/2021}, publisher = {HamSCI}, address = {Scranton, PA (Virtual)}, abstract = {

The New Jersey Institute of Technology Amateur Radio Club (NJITARC), K2MFF, has been an active part of the NJIT community for nearly a century.\  K2MFF has been a diligent community member, volunteering in such large-scale events as the New York City Marathon for over 30 years.\  Not only that, K2MFF, has been a fertile ground for developing young technical talent and advances in the radio art.\  Indeed, K2MFF has been a supporter and contributor to the HamSCI effort since its inception.\  In this presentation, we will offer a brief history of K2MFF, and discuss the current status and activities of the club.\  We will also offer some prognosis of the club{\textquoteright}s future directions.

}, url = {https://hamsci2021-uscranton.ipostersessions.com/?s=6A-73-A8-1F-B3-F9-DE-00-42-92-9A-F7-6B-59-C4-ED}, author = {Gareth W. Perry and F. Chu and Peter Teklinski} } @conference {537, title = {Observing Large Scale Traveling Ionospheric Disturbances using HamSCI Amateur Radio: Climatology with Connections to Geospace and Neutral Atmospheric Sources}, 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 lonospheric Disturbances (TIDs) are propagating variations in ionospheric electron densities that affect radio communications. LSTIDs create concavities in the ionospheric electron density profile that move horizontally with the LSTID and cause skip-distance focusing effects for high frequency (HF, 3-30 MHz) radio signals propagating through the ionosphere. This phenomena manifests as quasi-periodic variations in contact ranges in HF amateur radio communications recorded by automated monitoring systems such as RBN and WSPRNet. In this study, members of the Ham Radio Science Citizen Investigation (HamSCI) present a climatology of LSTID activity as well as using RBN and WSPRNet observations on the 1.8, 3.5, 7, 14, 21, and 28 MHz amateur radio bands from 2017. Results will be organized as a function observation frequency, longitudinal sector, season, and geomagnetic activity level. Connections to neutral atmospheric sources are also explored.

}, author = {Diego F. Sanchez and Nathaniel A. Frissell and Gareth W. Perry and William D. Engelke and Anthea Coster and Philip J. Erickson and J. Michael Ruohoniemi and Joseph B. H. Baker} } @proceedings {465, title = {Observing Traveling Ionospheric Disturbances using HamSCI Amateur Radio: Validation and Climatology}, year = {2021}, month = {03/2021}, publisher = {HamSCI}, address = {Scranton, PA (Virtual)}, abstract = {

Traveling lonospheric Disturbances (TIDs) are propagating variations in ionospheric electron densities that affect radio communications and can help with understanding energy transport throughout the coupled magnetosphere-ionosphere-neutral atmosphere system. Large scale TIDs (LSTIDs) have periods T\ \approx30-180\ min, horizontal phase velocities v_H\approx‍100-‍250 m/s, and horizontal wavelengths \lambda_H\>1000 km and are believed to be generated either by geomagnetic activity or lower atmospheric sources. TIDs create concavities in the ionospheric electron density profile that move horizontally with the TID and cause skip-distance focusing effects for high frequency (HF, 3-30 MHz) radio signals propagating through the ionosphere. The signature of this phenomena is manifest as quasi-periodic variations in contact ranges in HF amateur radio communication reports recorded by automated monitoring systems such as the Weak Signal Propagation Reporting Network (WSPRNet) and the Reverse Beacon Network (RBN). First in this study, members of the Ham Radio Science Citizen Investigation (HamSCI) present a case study showing consistency in LSTID signatures in RBN and WSPRNet are also present in Super Dual Auroral Radar Network (SuperDARN), Global Navigation Satellite System (GNSS), and ionosonde measurements. Then, we present a climatology of LSTID activity as well as\  using RBN and WSPRNet observations on the 1.8, 3.5, 7, 14, 21, and 28 MHz amateur radio bands from 2017. Results will be organized as a function observation frequency, longitudinal sector (North America and Europe), season, and geomagnetic activity level.

}, author = {Diego F. Sanchez and Nathaniel A. Frissell and Gareth W. Perry and William D. Engelke and Anthea Coster and Philip J. Erickson and J. Michael Ruohoniemi and Joseph B. H. Baker} } @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} } @conference {361, title = {Large Scale Traveling Ionospheric Disturbances Observed using HamSCI Amateur Radio, SuperDARN, and GNSS TEC}, booktitle = {American Geophysical Union Fall Meeting}, year = {2019}, month = {12/2019}, publisher = {American Geophysical Union}, organization = {American Geophysical Union}, address = {San Francisco, CA}, 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 observations made by Reverse Beacon Network (RBN) and the Weak Signal Propagation Reporting Network (WSPRNet) for the first time. The RBN and WSPRNet are two large-scale High Frequency (HF, 3-30 MHz) amateur (ham) radio observing networks that provide data to the Ham Radio Science Citizen Investigation (HamSCI). The LSTIDs were observed on the 7 and 14 MHz amateur radio bands, and are detected by observing changes in average propagation path length with time. LSTID period lengthened from T ~ 1.5 hr at 12 UT to T ~ 2.25 hr by 21 UT. Simultaneous LSTID signatures were present in ham radio observations over the continental United States, the Atlantic Ocean, and Europe. LSTIDs observed with amateur radio were consistent with LSTIDs observed by the Blackstone SuperDARN HF radar and in differential GNSS Total Electron Content (TEC) measurements. GNSS TEC maps were used to estimate LSTID parameters: horizontal wavelength 1100 km, phase velocity 950 km/hr, period 70 min, and propagation azimuth 135{\textdegree}. The LSTID signatures were observed throughout the day following ~800 nT surges in the Auroral Electrojet (AE) index at 00 and 12 UT. We will discuss potential generation hypotheses for the observed LSTIDs, including atmospheric gravity wave (AGW) sources triggered by auroral electrojet intensifications and associated Joule heating.

}, url = {https://agu.confex.com/agu/fm19/meetingapp.cgi/Paper/581488}, author = {Nathaniel A. Frissell and Diego F. Sanchez and Evan Markowitz and Gareth W. Perry and William D. Engelke and Anthea Coster and Philip J. Erickson and J. Michael Ruohoniemi and Joseph B. H. Baker} } @conference {325, title = {Sounding the Ionosphere with Signals of Opportunity in the High-Frequency (HF) Band}, booktitle = {HamSCI Workshop 2019}, year = {2019}, month = {03/2019}, publisher = {HamSCI}, organization = {HamSCI}, address = {Cleveland, OH}, abstract = {

The explosion of commercial off-the-shelf (COTS) education- and consumer-grade hardware supporting software-defined radio (SDR) over the past two decades has revolutionized many aspects of radio science, bringing the cost and calibration of traditionally complex receiver hardware within the grasp of even advanced amateur experimenters. Transmission has now become the limiter of access in many cases, particularly through spectrum management and licensing considerations. Fortunately, several classes of signals endemic to the HF band lend themselves to processing for ionospheric characteristics: time and frequency standard broadcasters, surface-wave oceanographic radars, amateur radio transmissions, and ionospheric sounders.

This presentation is a tour of these signals of opportunity and techniques for collecting and processing them into ionospheric characteristics, with emphasis on distributed receivers collecting on a small number (four or fewer) of coherent channels. Receiving techniques will be discussed for near-vertical ({\textquotedblleft}quasi-vertical{\textquotedblright}) incidence skywave (NVIS or QVI), long-distance oblique soundings, and transionospheric sounding. Soundings will be demonstrated from space-based, ground-based, and maritime platforms.

Binary, Doppler, delay, cone angle of arrival, and polarization observations will be exploited, depending on the signal type and capability of the collector. Each of these techniques conveys different, but not always {\textquotedblleft}orthogonal,{\textquotedblright} information about the ionospheric skywave channel. The information content of each datum will be discussed with respect to the implications for inverting the local or regional ionosphere from the observations. More importantly than inverting the full ionosphere, some of these techniques are sensitive indicators of ionospheric irregularities, structures, and instabilities, that might otherwise be difficult to study due to limited geographic coverage with larger, more exquisite instrumentation.

}, author = {Ethan S. Miller and Gary S. Bust and Gareth W. Perry and Stephen R. Kaeppler and Juha Vierinen and Nathaniel A. Frissell and A. A. Knuth and Philip J. Erickson and Romina Nikoukar and Alexander T. Chartier and P. Santos and C. Brum and J. T. Fentzke and T. R. Hanley and Andrew J. Gerrard} }