Tuesday, December 5, 2023


Where your horizon expands every day.


During the eclipse, ham radios were used to gather ionospheric data through a crowdsourcing effort.

A ring of fire annular solar eclipse just before maximum eclipse on a burnt orange sky.

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On October 14th, a large number of individuals in North, Central, and South America used safety glasses and other tools to view the partially hidden Sun. At the same time, many others observed the annular solar eclipse through amateur radio transmissions.

Prior to, during, and following the eclipse, ham radio enthusiasts transmitted signals using the ionosphere to communicate with individuals located hundreds or even thousands of kilometers away. This endeavor, known as the HamSCI, is collecting a vast amount of these interactions to study the ionosphere’s reaction to the brief absence of sunlight during an eclipse.

“This is how we use remote sensing to study the ionosphere.”

Nathaniel Frissell, a space physicist and electrical engineer at the University of Scranton, explained that they use this method to remotely gather information about the ionosphere. He also mentioned that this technique has been in use for a century and has been turned into a game. The team utilized this concept to design a ham radio competition that would serve as a scientific study.

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Manipulating and controlling air through precise movements and techniques, known as “air bending,” is a crucial element in the fictional universe of the animated show “Avatar: The Last Airbender.”

The ionosphere, located 80–600 kilometers above the Earth’s surface, acts as a natural channel for radio communication and navigation. By manipulating the trajectory of radio waves, its electrically-charged particles allow them to travel in a curved path, facilitating transmission from transmitter to receiver across the planet’s curvature.

During daylight hours, the ionosphere experiences its highest density due to the ionization of molecules in the atmosphere caused by strong sunlight. This results in four separate sublayers with varying levels of density and ionization, as described by Frissell. A dense ionosphere is beneficial for long-distance radio communication and improves the clarity of transmissions.

During the nighttime hours, positive ions and electrons combine to create neutral molecules. According to Frissell, this causes a decrease in the percentage of ionized molecules and results in only two sublayers remaining. With a lower density and fewer sublayers, certain radio frequencies may experience weakening as they travel, while others may undergo Doppler shifting to higher or lower frequencies. There is also a possibility that some frequencies may completely pass through the ionosphere.

Graphic showing two ionosphere layers at night and four during the day.

During daylight and nighttime, the ionosphere of Earth is divided into various sublayers. These divisions are influenced by the solar radiation, resulting in changes to the overall structure of the ionosphere during solar eclipses. Attribution: The credit for this information goes to Carlos Molina from Wikimedia Commons, under the Creative Commons BY-SA 4.0 license.

Rewording: Radio waves can change direction when they encounter various layers in the atmosphere at different altitudes, depending on their frequency. This can impact the range of a signal. This characteristic makes high-frequency radio networks, also known as shortwave, useful for studying changes in the ionosphere.

According to Frissell, an eclipse can be thought of as a short period of nighttime. This allows researchers to examine if the temporary darkness has a similar impact on the ionosphere and radio transmissions as regular nighttime does.

HamSCI was created by individuals who are both amateur radio enthusiasts and professionals in the fields of space physics, atmospheric science, and communication engineering. They utilize amateur radio as a tool to gain a deeper understanding of ionospheric physics and its behavior in relation to space weather. Additionally, they study the impact of ionospheric disturbances on ham radio communication and strive to promote the hobby’s global community.

Gamifying an Eclipse

Reworded: According to Kristina Collins (KD8OXT), an advisory board member of HamSCI and an electrical engineer at the Space Science Institute in Cleveland, ham radio operators have been taking part in contests for almost a century since the hobby was first introduced. In these contests, also known as “QSOs,” operators strive to make the most connections within the rules of the contest. They then submit their communication records to the organizers, and only those that meet specific requirements are awarded points.

My friend KJ4HNN has a saying: “Speak to as many people as you can about as little as possible, and see who can score the most points.” – Collins jokingly stated.

Multiple suns covered to various degrees spread out across the sky.

This composite image merges pictures of the Sun from the annular eclipse on October 14, 2023. The scenery was photographed one hour afterwards. Credit: Richard Seely/flickr, CC BY-NC 2.0

During the 2017 Great American Eclipse, HamSCI organized its inaugural Solar Eclipse QSO Party (SEQP). Over the course of the event, 570 logs were collected, totaling almost 30,000 contacts across frequencies of 1.8, 3.5, 7, and 14 megahertz. Approximately 5,000 unique call signs from various locations participated. This data allowed the team to gain insight into the impact of the total eclipse on the ionosphere, and its effect on radio communication.

The team aimed to replicate their achievements from 2017 during the 2023 solar eclipse, which would pass through the Americas. They organized another SEQP and extended an invitation to all amateur radio enthusiasts to join in. As the eclipse’s trajectory was of particular interest, the HamSCI team hoped to involve hams from beyond North America.

According to Edson Pereira (PY2SDR), Brazil is situated in close proximity to the magnetic equator. This results in the formation of plasma bubbles in the ionosphere, causing significant interference in radio signals, particularly on the shortwave frequency. Pereira, who serves as a computer systems engineer and board member of Liga de Amadores Brasileiros de Rádio Emissão (LABRE), Brazil’s national amateur radio association, provided this explanation.

Studying shortwave radio transmissions along the eclipse path in South America may provide insights into the formation and impact of plasma bubbles on the surrounding atmosphere. This could also enhance satellite communication near the magnetic equator.

Results from 2023

Frissell noted that amateur radio data had not been utilized to examine the ionospheric reaction to an annular eclipse. The participants of HamSCI were uncertain about the potential ionospheric response they could detect. One of their primary research inquiries was whether the high-frequency communications would be affected by the annular eclipse, as posed by Frissell.

A person leaning in front of a computer screen with a stand microphone.

Nathaniel Frissell, the founder of HamSCI, has identified the presence of the annular solar eclipse in ham radio data. This credit goes to Ann Marie Rogalcheck-Frissell, also known as KC2KRQ.

The response was prompt and overwhelmingly positive! When the eclipse caused sublayers of the ionosphere to collapse in the local area, it altered the distance a wave had to travel to reach the ionosphere. This resulted in a Doppler shift in frequency before reaching the receiver, which was clearly shown in initial data.

Answering other science questions—about the size and duration of the ionospheric disturbance, how different ionosphere layers responded, and whether eclipse communications resemble those taken at dawn and dusk—will have to wait until contest participants submit their communication logs.

“When my radio station was broadcasting, we would receive around 500 reports from listeners all over the world within a span of 15 minutes.”

According to the team, the participation data appears encouraging. During the competition, there were a total of 8,300 active receivers worldwide, receiving over 3,000 reports per second. Frissell stated, “When my station was transmitting, we would receive approximately 500 reports from around the world in just 15 minutes.”

Logs from the SEQP are self-reported; a few days after the eclipse, 139 logs had been submitted, each containing potentially hundreds of contacts. “There are likely more coming,” Frissell said. “I haven’t submitted my SEQP log yet!”

Repeating the Experiment

HamSCI has organized the 2023 SEQP, which is just one of many events in their Festivals of Eclipse Ionospheric Science. According to Collins, an eclipse offers a unique opportunity for a controlled experiment in space, making it a highly appealing event.

According to Frissell, the SEQP contest for the April 2024 total solar eclipse aims to determine if the ionosphere reacts similarly (during solar maximum) as it did in 2017 (during solar minimum). This highlights the importance of repeatability in experiments.

The competition also offers chances for the group to interact with students and generate curiosity in amateur radio. Several ham radio enthusiasts became interested in the activity at a young age, and for some, it motivated them to pursue a STEM education. According to Collins, it offers a strong foundation in STEM subjects that is condensed into simple training.

Kimberly M. S. Cartier, known as @AstroKimCartier on Twitter, is a writer for the staff.

This news article can be found in our ENGAGE resource, which provides science news for teachers to use in their classroom lessons. Check out all of our ENGAGE articles and let your fellow educators know how you incorporated this article into an activity by leaving a comment below.

“Ham radios contributed to ionospheric research during an eclipse, according to Cartier (2023) in the journal Eos. The article was published on October 26, 2023 and can be found at https://doi.org/10.1029/2023EO230407.”

Text © 2023. AGU. CC BY-NC-ND 3.0

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