Beyond detection: How TRIDENT will identify the source of a TID

Ian Collett, Ionospheric Scientist 

In an earlier blog, we introduced TRIDENT, a next-generation high-frequency (HF) sounding system designed by Orion to advance our understanding of traveling ionospheric disturbances (TIDs).  

In this follow-up, we dive deeper into TRIDENT’s capabilities and how they address one of the most persistent challenges in TID research: the ability to fully characterize TIDs in both horizontal and vertical dimensions. This breakthrough gives researchers a more complete view of how we study, model and even predict the behavior of these disturbances.

MOVING BEYOND TRADITIONAL METHODS 

Currently, many TID studies rely on global navigation satellite system total electron content (TEC) data to infer TID characteristics. While TEC data provides valuable insight, it only captures horizontal information, which offers a two-dimensional view of the ionosphere’s behavior. Critical vertical information, which is necessary to fully understand the propagation and origin of TIDs, is often missing.  

With a network of six sites, two transmitters and four receivers, TRIDENT provides measurements of both horizontal and vertical propagation characteristics. Its dual-frequency transmission capability allows each transmitter to simultaneously broadcast on two frequencies that reach different heights in the ionosphere—higher frequencies penetrate to greater altitudes—enabling vertical propagation measurements. 

This means key details like wavelength, azimuth, period and phase speed will all be captured, offering an unprecedented 3D view of a TID’s journey through the ionosphere.  

PREDICTING AND CLASSIFYING TIDS 

TRIDENT isn’t just collecting data; it’s also laying the foundation for prediction. At Orion, we’re developing a regional model that combines TRIDENT observations with climatological data to forecast TID propagation and identify the origins of the disturbances.  

Here’s the plan:  

1. Characterizing TIDs: By using advanced spectral analysis techniques, such as the N-Dimensional Lomb-Scargle Periodogram, TRIDENT determines the k-vector of each TID. This allows us to identify its propagation properties and, in some cases, trace it back to its source. For example, thunderstorm-driven TIDs help researchers explore how localized atmospheric events send ripples through the ionosphere. 
   

2. Distinguishing propagation modes: Using modeled temperature profiles and frequency analysis, we’ll determine whether a TID is driven by atmospheric gravity waves or acoustic waves. This classification helps researchers better understand the physical mechanisms behind TIDs and their link to global atmospheric and geomagnetic activity.  
   

3. Building predictive models: By using historical data from an earlier version of the system, we are actively building dynamic models to predict TID behavior. Now that TRIDENT is fully deployed, these models will be refined to provide real-time insights into ongoing disturbances. 
   

MOVING TOWARD A MORE PREDICTABLE IONOSPHERE 

The potential applications of this approach are transformative. By integrating TRIDENT observations into regional ionospheric models, we will not only improve our understanding of TID behavior but also empower industries like aviation, defense and telecommunications to anticipate and mitigate disruptions caused by ionospheric disturbances. 

Furthermore, by identifying the origins of TIDs, whether they’re triggered by geomagnetic storms, thunderstorms or human-made events like rocket launches, we can begin to paint a clearer picture of the Earth-atmosphere-ionosphere connection.  

WHAT LIES AHEAD 

Thunderstorm-driven TIDs are just the beginning. Now that the first full TRIDENT system is operating in the field, data from the system are being used to examine TIDs across a wide range of sources and scales, creating a comprehensive view of how Earth’s atmosphere interacts with the ionosphere.  

As TRIDENT continues to evolve, it promises not only to advance the field of space weather science but also to bring greater reliability and resilience to the technology systems we depend on every day.  

Stay tuned as we continue to explore the boundaries of what TRIDENT can achieve and what its data will reveal about our dynamic atmosphere.  

ABOUT THE AUTHOR 

Dr. Ian Collett is a senior research scientist at Orion, specializing in radio frequency remote sensing of the ionosphere. His expertise spans HF through L-band frequencies, signal processing and data science. He leads Orion's development of HF algorithms for TRIDENT and serves as principal investigator for Orion’s work on the IARPA SINTRA program.