The year 2018 produced no total solar eclipse, but it did feature three partial solar eclipses that drew attention from both scientists and casual observers. The most scientifically productive of these was the partial solar eclipse of August 11, 2018, which swept across northern Europe, northeastern Asia, and parts of the Arctic. While it lacked the dramatic totality of the 2017 “Great American Eclipse” the year before, the August 2018 event still offered researchers a valuable opportunity to study how even a partial blocking of the Sun affects everything from the upper atmosphere to animal behavior.
The Three Partial Eclipses of 2018
Solar eclipses come in cycles, and not every year delivers a total eclipse visible from populated areas. In 2018, three partial solar eclipses occurred. The first, on February 15, was visible only from parts of southern South America and Antarctica. The second, on July 13, grazed the coastline of southern Australia and was visible mainly from open ocean. Neither generated much public excitement or scientific data.
The third and final eclipse of the year, on August 11, 2018, was the big one for researchers. Its path of partial obscuration crossed Scandinavia, Greenland, northern Russia, and large sections of China and Mongolia. In northern Scandinavia and the Arctic, the Moon covered roughly two-thirds of the Sun’s disk at maximum eclipse. Across China, the obscuration was more modest but still enough to produce measurable effects on the atmosphere and on solar energy infrastructure. Because China had extensive radio monitoring networks in place, this eclipse became one of the best-instrumented partial eclipses in modern history.
Ionospheric Disturbances Over China
One of the most detailed studies of the August 11, 2018 eclipse focused on what it did to the ionosphere, the electrically charged layer of Earth’s upper atmosphere that plays a key role in radio communications. When the Moon blocks even a fraction of incoming solar radiation, it reduces the energy that ionizes gas molecules at high altitude. The result is a measurable dip in the ionosphere’s electron density, and that dip ripples outward in ways that radio instruments can detect.
Monitoring stations along several paths in China tracked these changes in real time. The eclipse triggered oscillations in electron density with amplitudes of roughly 9 to 14 percent, in a range of periods associated with atmospheric gravity waves. Along the Hailar-to-Harbin radio path, the ionosphere’s E region experienced a maximum electron density decrease of about 26 percent. Radio signals also showed a negative Doppler frequency shift as the eclipse progressed, followed by a smaller positive shift during recovery, a signature of the ionosphere first compressing and then relaxing as sunlight returned.1Radio Science. Radio Monitoring of Dynamic Processes in the Ionosphere Over China During the Partial Solar Eclipse of 11 August 2018
These findings matter beyond pure atmospheric science. The ionosphere is what makes long-distance shortwave radio work, and its behavior during eclipses gives researchers a controlled, predictable “experiment” they can use to test models of how the upper atmosphere responds to sudden changes in solar input. The 2018 eclipse data have since been folded into broader models of ionospheric variability.
What Eclipse Coronae Reveal About the Sun’s Magnetic Field
Total solar eclipses remain the gold standard for studying the Sun’s corona, the wispy outer atmosphere that is normally invisible against the glare of the solar disk. Partial eclipses like those in 2018 do not fully expose the corona, but data from the broader family of eclipses, spanning nearly two complete solar cycles, have produced striking findings about how the Sun’s magnetic field behaves at different altitudes.
A study analyzing 14 unique eclipse coronae found that the coronal magnetic field does not straighten into a purely radial pattern until at least three solar radii from the surface, much farther out than older models assumed. Between about 1.5 and 3 solar radii, the field direction varies considerably depending on latitude and the phase of the solar cycle. Regions above weaker photospheric magnetic fields tend to have the most tangled, nonradial field topologies, while areas above stronger surface fields produce straighter field lines.2The Astrophysical Journal. Coronal Magnetic Field Topology from Total Solar Eclipse Observations
This kind of mapping is only possible during eclipses, when the Moon acts as a natural coronagraph. Space-based coronagraphs block the inner corona with an artificial disk, but they introduce diffraction artifacts that make the region closest to the Sun difficult to study. The eclipse-based measurements fill a critical gap in our understanding of how the Sun’s magnetic field connects its surface to the broader solar wind that streams past Earth.
How Animals React When the Sun Disappears
Eclipses produce rapid changes in light, temperature, and even wind patterns that can confuse animals accustomed to the predictable rhythm of day and night. Much of the best recent data on animal responses comes from the 2017 total solar eclipse, but the patterns documented then are broadly consistent with what observers have reported during partial and total eclipses for centuries.
A study at a zoo during the 2017 total eclipse formally observed 17 species and found that about three-quarters of them changed their behavior noticeably during the event. Most bird species and both reptile species under observation shifted their activity patterns. Some animals began evening routines like heading toward shelters or becoming more vocal, while others became unusually still. The researchers acknowledged that some behavioral changes could have been triggered by the unusual reactions of zoo visitors rather than by the eclipse itself, but many of the observed behaviors matched descriptions in the literature from previous eclipses, suggesting a direct response to the changing light conditions.3PubMed Central. Total Eclipse of the Zoo: Animal Behavior during a Total Solar Eclipse
Radar data told a complementary story on a much larger scale. Weather surveillance radars across the United States can detect biological targets, including birds, bats, and large insects, in the lower atmosphere. During the 2017 eclipse, biological activity measured by radar decreased as the Moon moved toward totality, consistent with daytime flyers landing. At some radar stations, a brief spike of low-altitude biological activity appeared during totality itself, as if some animals interpreted the sudden darkness as dusk and launched short flights. Once the Sun returned, normal daytime patterns resumed. The researchers concluded that eclipse-related cues were strong enough to suppress normal daytime activity but not strong enough to trigger a full nighttime flight comparable to what happens at actual sunset.4PubMed Central. Aeroecology of a solar eclipse
This distinction matters for understanding how animals read environmental cues. A real sunset brings gradual dimming, dropping temperatures, changing insect availability, and shifting wind patterns over the course of an hour or more. An eclipse compresses similar light changes into minutes, but without the supporting temperature and wind cues that animals rely on to initiate genuine nighttime behavior. The result is a kind of half-response: confusion rather than commitment.
What Happens to Plants During an Eclipse
Plants do not simply turn off when the Sun disappears; they throttle down, and how quickly they do so reveals something about how tightly their gas-exchange machinery is tuned to incoming light. During the 2017 total solar eclipse, researchers measured the responses of big sagebrush in real time and found that the plants reduced their water loss through leaves by about 70 percent over the course of the eclipse. Carbon uptake dropped as well, with modeled calculations showing roughly a 14 percent reduction in total carbon assimilation for the day compared to what would have been expected without the eclipse.5PubMed Central. Hydraulic and photosynthetic responses of big sagebrush to the 2017 total solar eclipse
The 70 percent drop in water loss is dramatic and reflects how quickly the tiny pores on leaf surfaces close in response to diminished light. Plants essentially shut down their gas exchange to conserve water when photosynthesis cannot keep pace. This rapid stomatal closure during an eclipse provides a natural stress test that complements laboratory experiments on how plants respond to sudden shading. For ecologists, the 14 percent daily carbon reduction hints at how sensitive regional carbon budgets could be to large-scale light disruptions, although a single eclipse lasting a few hours is obviously too brief to have lasting ecological consequences.
Solar Panels and the Power Grid
As solar energy has grown into a major component of electricity generation, eclipses have gone from astronomical curiosities to grid-management events. During a solar eclipse, photovoltaic output drops in proportion to how much of the Sun’s disk is obscured, and grid operators must compensate by ramping up other power sources. A case study examining two real-world grid-tied solar installations in Florida during the 2017 eclipse, one rated at 1.4 megawatts and the other at 355 kilowatts, documented the magnitude of these effects in detail.6IET Smart Grid. Case study on the effects of partial solar eclipse on distributed PV systems and management areas
The 2018 partial eclipses posed similar challenges wherever significant solar capacity existed along the eclipse path. Northern Europe, which has invested heavily in solar energy, had to manage the August 11 event even though the obscuration was partial. Grid operators in Scandinavia and Germany prepared for the ramp-down and ramp-up in solar generation, using forecasting tools that factored in the eclipse’s timing and magnitude. The experience reinforced a lesson that the European grid had already learned from a partial eclipse in 2015: the problem is not the loss of solar power during the eclipse itself, which is predictable, but the rapid ramp-up afterward, when solar output surges back to full strength and conventional generators must quickly step aside. Countries with high solar penetration now treat eclipse events as routine grid-management exercises, using detailed forecasts of the eclipse’s path and timing to pre-position backup generation.
Eye Safety and Solar Retinopathy
Every solar eclipse brings a surge of public interest in looking at the Sun, and with it a spike in cases of solar retinopathy, damage to the retina caused by staring at the Sun without adequate protection. The risk is real even during partial eclipses, when enough of the Sun’s disk remains exposed to cause injury. In some ways, partial eclipses are more dangerous than total ones, because the lingering brightness discourages the false sense of safety that can occur during the brief totality of a total eclipse.
Clinical case reports from multiple eclipses show a consistent pattern. Patients who viewed the eclipse without proper eye protection present with blurred vision, central scotomas (blind spots), and color vision disturbances. A case series of four young patients who observed the 2011 total eclipse without protection documented acute, severe retinal damage visible on examination.7PubMed Central. Acute eclipse retinopathy: a small case series More recent imaging studies have shown that the damage extends to specific layers of the retina, particularly the outer retinal layers and the Henle fiber layer, with some evidence of vascular involvement as well. Follow-up imaging reveals that while some patients recover, others experience lasting structural changes in the retina.8PubMed. Impact of Solar Eclipses on Vision: Insights from Optical Coherence Tomography and Optical Coherence Tomography Angiography Analysis
The only safe way to look directly at a partially eclipsed Sun is through certified solar viewing glasses that meet the ISO 12312-2 standard, or by using indirect projection methods such as a pinhole projector. Regular sunglasses, even very dark ones, do not block enough infrared and ultraviolet radiation to prevent retinal burns. During the brief seconds of totality in a total eclipse, when the Moon completely covers the Sun’s bright surface, it is safe to look without filters, but the moment any sliver of the Sun reappears, the danger returns instantly. Public health messaging around every eclipse hammers this point, yet emergency departments reliably see retinopathy cases in the days following each event.
Why 2018 Sits in the Shadow of 2017
One reason the 2018 eclipses received relatively little public attention is that they followed the 2017 total solar eclipse, which crossed the entire continental United States and was one of the most widely observed astronomical events in American history. An estimated tens of millions of people watched the 2017 event in person, and it generated an enormous volume of scientific data, citizen science contributions, and media coverage. By comparison, the three partial eclipses of 2018 were visible from less populated regions and lacked the spectacle of totality.
That disparity in public interest does not map neatly onto scientific value, though. Partial eclipses like those in 2018 provide data that total eclipses cannot. The gradual dimming during a partial eclipse creates a smoother experimental ramp that is useful for studying dose-response relationships in plants, atmospheric physics, and solar energy systems. The ionospheric data from the August 2018 eclipse over China, for instance, benefited from the fact that the eclipse was partial: the gradual onset and recovery of the shadow allowed researchers to track the ionosphere’s response over a longer and more continuous time window than a total eclipse would have provided.9Radio Science. Radio Monitoring of Dynamic Processes in the Ionosphere Over China During the Partial Solar Eclipse of 11 August 2018
Each eclipse, whether partial, annular, or total, adds another data point to long-running research programs. The coronal magnetic field study that analyzed 14 eclipses’ worth of data is a good example: no single eclipse would have been sufficient to map how the corona’s field structure changes across nearly two full solar cycles. The 2018 events did not make headlines the way 2017 did, but they contributed quietly to the slow accumulation of knowledge that makes eclipse science possible.10The Astrophysical Journal. Coronal Magnetic Field Topology from Total Solar Eclipse Observations
When the Next Eclipses Came
For eclipse chasers disappointed by 2018’s partial-only menu, 2019 offered a total solar eclipse on July 2 visible from the South Pacific and parts of Chile and Argentina. The next total solar eclipse to cross the continental United States did not arrive until April 8, 2024, when a path of totality swept from Texas to Maine. That event rekindled the kind of mass public engagement last seen in 2017 and gave researchers yet another opportunity to deploy instruments, survey animal behavior, and stress-test power grids.
The rhythm of eclipses follows the geometry of the Moon’s orbit, which is tilted about five degrees relative to Earth’s orbit around the Sun. This tilt means that most new moons pass above or below the Sun from our perspective, producing no eclipse at all. Only when a new moon falls near one of the two points where the Moon’s orbital plane crosses Earth’s, called nodes, does the alignment produce a solar eclipse. The node positions shift gradually, so eclipse paths migrate across different regions over the years. Any given location on Earth sees a total solar eclipse roughly once every 375 years on average, which is why the events draw such intense interest whenever the path happens to cross a populated area.
Partial eclipses like those in 2018 are considerably more common at any given location and receive far less attention. But the scientific infrastructure deployed during one eclipse often remains in place or is easily reactivated for the next, creating a continuity of measurement that spans years and sometimes decades. The 2018 eclipses were modest events by the standards of public spectacle, but they contributed meaningfully to the long observational record that gives eclipse science its power.