On April 8, a spectacular total solar eclipse will traverse North America, casting a diagonal path of darkness across the continent. Those located in the “path of totality” will witness an awe-inspiring moment when the moon completely obscures the sun, creating a few surreal minutes of daylight transformed into dusk.
The last time a solar eclipse graced the continental United States was in August 2017, tracing a line from Oregon through to South Carolina. This year, however, the moon will follow a closer trajectory to Earth, creating a broader arc that extends from Mexico, through Texas, and up to Maine and Eastern Canada. Notably, this eclipse will pass over more densely populated areas than its predecessor, providing over 31 million people with the chance to experience complete darkness, while other regions will enjoy a partial eclipse depending on local weather conditions.
As many prepare with their eclipse-safe glasses, MIT’s Haystack Observatory is gearing up with a variety of advanced instruments to investigate the eclipse and its impacts on the upper atmosphere. Their primary focus will be the ionosphere—the outer layer of the atmosphere where numerous satellites orbit. This layer, spanning from 50 to 400 miles above Earth, is constantly bombarded by the sun’s ultraviolet and X-ray radiation, which ionizes gas molecules, leading to a fluctuating sea of electrons and ions that responds to variations in solar energy levels.
Similar to 2017, researchers at Haystack will examine how the ionosphere reacts before, during, and after the eclipse, particularly as solar radiation experiences a sudden decline. This year, they will introduce two innovative technologies that allow them to capture the eclipse’s effects on local, regional, and national scales. The findings may provide valuable insights into how our atmosphere reacts to sudden shifts in solar radiation, such as those seen during solar storms or flares.
The key figures behind this eclipse study at Haystack are research scientists Larisa Goncharenko, who specializes in ionospheric physics using varied observational data, and John Swoboda, who focuses on developing instruments for monitoring near-Earth phenomena. In a recent discussion with MIT News, they shared how they plan to observe the eclipse and what they expect to discover during this rare celestial event.
Q: With so much excitement surrounding the upcoming solar eclipse, can you explain how a total eclipse influences the atmosphere?
Goncharenko: We have gathered significant insights. One of the most pronounced effects is the considerable drop in electron density in the ionosphere as the moon’s shadow sweeps across the continent. The sun acts as a primary source of ionization, and when that source is obscured, electron density decreases, creating a gap in the ionosphere that follows the moon’s path.
Goncharenko: During an eclipse, solar heating is interrupted, simulating a rapid sunset and sunrise, leading to cooling in the atmosphere. This creates a cold area of low ionization that moves in both latitude and longitude. Additionally, these temperature alterations disturb wind patterns, affecting the distribution of plasma—essentially, the electrons—within the ionosphere, resulting in large-scale changes.
From the cold region trailing totality, we can also observe various types of waves emerging. Picture a boat navigating through water; it generates bow shock waves that travel outward. These electron density waves, although small, can encompass vast areas. Similar waves were seen during the 2017 eclipse, but every event is distinct. Thus, we will treat this eclipse as a one-of-a-kind laboratory experiment and monitor shifts in electron density, temperature, and wind patterns in the upper atmosphere as the eclipse traverses the continental U.S.
Q: What methods will you employ to capture these atmospheric changes during the eclipse?
Swoboda: We’ll analyze local atmospheric variations and ionospheric conditions using two cutting-edge radar technologies. The first, Zephyr, developed by Haystack research scientist Ryan Volz, examines how meteors disintegrate in our atmosphere. When sand-sized particles burn up, they leave behind plasma trails that follow higher altitude wind patterns. Zephyr emits signals that reflect off these plasma trails, allowing us to study how winds in the upper atmosphere fluctuate during the eclipse.
The second radar system, known as EMVSIS [Electro-Magnetic Vector Sensor Ionospheric Sounder] , will gauge the electron density and bulk velocity of charged particles in the ionosphere. This new system combines multiple transmitters and receivers to send and receive radio waves across different frequencies for measurements. Unlike traditional ionospheric sounders, which require large, high-power transmitters and towers, our compact system—approximately the size of a refrigerator—will be deployed across New England for both local and regional measurements.
Goncharenko: Additionally, we will conduct regional assessments using two antennas at the Millstone Hill Geospace Facility in Westford, Massachusetts. One is a fixed vertical antenna, spanning 220 feet, designed to observe parameters in the ionosphere at altitudes ranging from 90 to 1,000 kilometers above ground. The other, a steerable 150-foot diameter antenna, allows us to monitor alterations as far off as Florida and throughout the central U.S. Both antennas will be instrumental in capturing data during the eclipse.
We will also analyze information gathered from a national network of nearly 3,000 GNSS [Global Navigation Satellite System] receivers across the U.S., with new installations planned for less-sampled areas along the totality path. These receivers will document variations in the ionosphere’s electron content before, during, and after the eclipse.
This is an exciting opportunity, as it marks the first time we will employ all four technologies concurrently. Each technology offers a unique perspective, and as a scientist, I feel like a child anticipating Christmas morning. New discoveries await, and I can’t wait to delve into the data we collect.
Q: As you prepare for this unique observation, what outcomes do you anticipate from your measurements?
Goncharenko: I expect surprises. This will be our first chance to observe near-Earth space with a coordinated deployment of four different technologies simultaneously in the same geographic area. We anticipate increased sensitivity, which should enhance our resolution in time and space. By probing the upper atmosphere using this array of diagnostic tools, we hope to gather previously unattainable simultaneous observations—ultimately mapping four-dimensional factors such as wind flow, electron density, ion temperature, and plasma motion. We will study their changes throughout the eclipse and investigate how fluctuations in one segment of the upper atmosphere connect to disturbances in other time and spatial areas.
Swoboda: We are also thinking about long-term implications. The eclipse allows us to showcase the capabilities of these technologies, sparking a question: what if we could continuously operate them? A radar network for space weather monitoring could revolutionize our understanding, much like we do for lower atmospheric conditions. Considering how frequently satellites are launched and affected by space weather, such a network is crucial.
Goncharenko: There is a vast amount of atmospheric space to explore. The eclipse serves as just a dramatic highlight in our endeavors. Ultimately, these systems promise to yield invaluable data regarding the upper atmosphere’s behavior during other disturbances, such as storms, lightning activity, coronal mass ejections, and solar flares. All this work contributes to a larger mission to deepen our understanding of near-Earth space and address the demands of our modern technological society.
Photo credit & article inspired by: Massachusetts Institute of Technology
