Preparing for a Total Solar Eclipse

For the first time in seven years, North America is preparing for a total solar eclipse

The total solar eclipse will cover portions of Mexico, the U.S., and Canada on April 8, 2024. A solar eclipse is when the Moon passes between the Sun and Earth, as seen in Figure 1. This blocks the face of the sun, casting a shadow on Earth. Totality is when the Moon completely blocks the sun’s rays. Those in the path of totality can expect the sky to become dark as if it was dawn or dusk. If weather permits, those in the path totality will be also able to see the Sun’s corona, or the outer most part of the Sun’s atmosphere.

Fig. 1. Graphical representation of a solar eclipse.

Eclipse viewers must wear special glasses. Eclipse glasses filter out damaging radiation for direct viewing of the sun. People in the path of totality and partial eclipse area do need eclipse glasses. The only time you can view the eclipse directly is during the brief time of totality, usually a minute or two.

The 2024 total solar eclipse will be one of the most-watched live natural events in history with about 32 million people in the path of totality. Its total path is 9,020 miles long, but only 3,375 miles of it will be over land.

The first location to experience totality is Mexico’s Pacific coast at around 11:07 a.m. PDT. The path continues in a northeasterly direction traveling through Texas, Oklahoma, Arkansas, Missouri, Illinois, Kentucky, Indiana, Ohio, Pennsylvania, New York, Vermont, New Hampshire, and Maine. It continues into Canada through Quebec, New Brunswick, Prince Edward Island and Nova Scotia. The eclipse exits North America at 5:16 p.m. NDT on the Atlantic Coast of Newfoundland, Canada. Check out the interactive map in Figure 2 to follow the path of totality.

Fig. 2. Interaction map showing the 2024 solar eclipse path of totality. Courtesy: Google

The next total solar eclipse in the contiguous United States will be Aug. 23, 2044. Eclipse seekers can see it in Montana, North Dakota, South Dakota and Greenland, Canada.

Phases of a Total Solar Eclipse

A total solar eclipse takes place in five phases. The first phase is a partial eclipse. This is when a crescent shaped moon starts to move in front of the Sun. First contact happens when the Moon first ‘touches’ the Sun. This phase can last 70 to 80 minutes.

Second shadow bands appear. These are rapidly moving, long dark bands separated by white spaces. It is difficult to take photos of shadow bands but they can be see on the side of buildings or the ground. Turbulent cells of air make up the bands. They distort the sharp-edged light from the Sun’s surface, similar to the distortion process that makes stars twinkle.

Fig. 3. Phases of a total solar eclipse. Photos courtesy of NASA.

Next Baily’s Beads form, or points of light shining around the Moon’s edges. These points are actually rays of sunlight shining through valleys along the Moon’s horizon. This sight is short-lived and may not last long enough to be noticeable.

The last phase before totality is the diamond ring stage. This is a single bright spot that remains along the edge of the Moon’s shadow, resembling a diamond on a ring.

When the ring disappears, you have reached totality. This is when there is no direct sunlight shining on Earth. If conditions allow, viewers will be able to see two things usually not visible to the naked eye: the corona and chromosphere. The chromosphere is a region of the Sun’s atmosphere that appears as a thick, pink circle around the Moon. Totality lasts only about a minute or two. Nazas, Mexico will spend the most time in totality at 4 minutes and 28 seconds.

As totality wraps up, the sky begins to brighten, and the stages reappear but in reverse order.

Impacts on Earth’s Atmosphere

Fig. 4. Layers of Earth’s atmosphere.

Solar eclipses can have an impact on Earth’s ionosphere, which is located in the upper Thermosphere. The ionosphere is between 37-190 miles above Earth’s surface and is made of ionized atoms and molecules creating a layer of electrons.

Since solar radiation is the primary source of ionization, an eclipse impacts this layer by reducing the amount of sunlight reaching the Earth’s atmosphere. This decrease in radiation leads to a temporary drop in the density of electrons causing the atmosphere to be less charged. It also leads to cooling temperatures and the potential for changes in ionospheric altitudes. The sudden shift in temperature and density can lead to the formation of ionospheric anomalies such as ionospheric holes or depletions. Fluctuating conditions during an eclipse can change how radio waves propagate causing signal fading, absorption, and refraction. This does have the potential to impact shortwave and satellite communication systems.

Any changes due to an eclipse are generally temporary and localized with the ionosphere returning to normal when the event is over.

Effects on Spacecraft

The ionosphere is home to low-Earth orbiting satellites and the International Space Station. Spacecraft living in this region have to be built to withstand shifting conditions. Failure to do so can lead to shortened lifespans and failed missions.

During the total solar eclipse, spacecraft in the ionosphere will have to be prepared to switch quickly between daytime, high density of electrons, and nighttime, low density of electrons, conditions. Satellites can remain in orbit for decades, and with a total solar eclipse taking place about every 18 months, they could be in the Moon’s shadow on several occasions. This is why eclipse conditions must be considered when building spacecraft.

Testing for Space

Testing spacecraft equipment typically needs to take place in space since materials will react differently than when on Earth. Getting measurements is expensive, time consuming, and the data collected can be extremely limited. However, there is now a less expensive way to get accurate measurements in a fraction of the time.

Measurement

EMA’s Space Environment and Radiation Effects (SERE) commercial test chamber takes detailed measurements of spacecraft components and instruments right in our Pittsfield, MA office. The high vacuum test chamber includes a 24” sample plate for mounting equipment and customizable radiation sources to create realistic spectra associated with various orbits and conditions, including during an eclipse.

Fig. 5. EMA Space Environment and Radiation Effects (SERE) commercial test chamber.

Current radiation sources include:

• An electron flood source that produces energies between 500eV- 100keV with fluxes measurable down to 5pA/cm² and a max output of 5nA/cm² with beam uniformity staying within 80% of max with a 13”x13” square.
• A low plasma generator with an incorporated magnetic filter that produces 5-20eV along with sub-eV electron to mimic the low earth orbit plasma environment. This generator is used with various gases and output currents to produce densities that range from 1×10¹³ – 1×10⁸ #/m³.
• A VUV Krypton arc lamp with a continuous spectrum from 125-165nm and an additional peak at 116nm is used for surface neutralization and lower end solar simulation.

SERE testing is more powerful when combined with Ansys Charge Plus simulation. Charge Plus is a one-of-a-kind commercial solver that combines electromagnetic solvers, fluid solvers, and particle physics solvers for easy-to-use multiphysics simulation.

Applications areas include:

• Space plasma environments and radiation effects
• Electrostatic discharge
• Arcing
• Semiconductor processing plasmas

Simulation

When it comes to simulating accurate space environments, Charge Plus properly considers gas-phase interactions, chemical reactions, and particle physics effects that are critical for plasma dynamics. Run the entire simulation workflow in one interface that easily connects with external databases and tools.

It is the only commercial tool on the market that addresses the effects on spacecraft from the plasma environment and spacecraft materials and electronics from radiation environments using particle physics interactions.

Conclusion

Eclipses are not random and actually take place in overlapping patterns or Saros. The pattern of this total solar eclipse takes place every 18 years, 11 days, and eight hours. This same alignment will take place on April 20, 2042, in Indonesia, Malaysia, and the Philippines. Designers have 18 years to prepare any spacecraft.

Click here to learn more about SERE and get started testing.

Ansys is the exclusive seller of Charge Plus. Start simulating your prodcuts by clicking here.