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NASA fellowship recipient studies effect of solar flares on Venus' nightglow

Candace Gray spent her childhood with her siblings looking up at the stars and watching for meteor showers. As the recipient of the NASA Earth and Space Science Fellowship, the New Mexico State University graduate student is now keeping her eyes firmly planted on Venus as she tries to determine whether certain oxygen emissions seen in its atmosphere are caused by enhanced solar flux on the planet during solar flares.

Girl sitting at computer
As part of her fellowship, Candace Gray will study how the nightglow changes after solar flares and coronal mass ejections impact Venus. (NMSU photo by Audry Olmsted)

Gray has just completed her second year of the graduate program in the Department of Astronomy. Through her proposal to NASA entitled "Upper Atmosphere Chemistry and Nightglow Variability on Venus and its Connection to Solar Flares," Gray believes she can fill some pieces in the evolutionary puzzle of terrestrial planet atmospheres.

"If you look at our solar system, Venus, Earth and Mars all formed really close to each other,' she said. "They formed with similar materials, under the same conditions and temperatures, and at the same time. We would expect them to evolve similarly and have similar atmospheres, but they don't. This shows that they underwent different evolutionary processes. To understand these processes, we need to understand the chemistry going on and then backtrack in time."

For her part, Gray is studying the effects of solar flares on nightglow on Venus. Nightglow occurs when atoms and ions on the dayside of a planet get transported to the night side and reconnect with atoms and electrons, releasing light at various wavelengths. Theses reactions take place in the mesosphere and the ionosphere.

"One particular nightglow feature on Earth, an oxygen transition that emits green light, is a persistent nightglow feature," Gray said. "However, this feature is highly variable. Sometimes, it is as strong as the emission on Earth, sometimes it is very weak and sometimes it cannot be detected at all."

The oxygen green line nightglow feature has not been detected since 2004.

Gray wonders if the appearance of the planet's nightglow is connected to the solar cycle and the extreme ultra-violet light produced by solar flares and charged particles from coronal mass ejections (CMEs).

"When you have extreme ultra-violet light hitting molecules, it will break them up. They will then travel night side where they can come back together," she said. "But, you need that amount of energy to break these molecules up, to ionize the atoms in order to have an increased amount of emission on the night side. My thought is that solar flares enhance the nightglow."

Gray is conducting a large portion of her work at NMSU's Apache Point Observatory, using the 3.5 meter Astrophysical Consortium Telescope. She has partnered with Tom Slanger, of the Stanford Research Institute for her research.

Based on the data she has researched, Gray has observed that every time the oxygen green light nightglow feature was detected on Venus, there were solar flare eruptions a few days prior. There also appears to be a correlation with CMEs, which can deposit large amounts of charged particles in the ionosphere (part of the upper atmosphere), and may also increase nightglow emission.

Gray will study how the nightglow changes after solar flares and CMEs impact Venus. The emical process responsible for the green line emission on Venus is unknown. Since the feature can occur in the mesosphere and/or ionosphere, the chemical processes from both regions must be considered. Observing the separate effects of EUV light and charged particles on nightglow will help determine what chemical process is dominating.

Gray's advisor, Nancy Chanover, an associate professor of astronomy, said the project will make unique contributions to the field of Venus atmospheric science. Gray's regular access to Apache Point Observatory will enable her to study Venus' nightglow emission as a function of time and solar activity using both optical and near-IR observations, which has never been previously attempted.

"Candace is an incredibly hard worker who has shown a great deal of initiative and creativity in the development of her research project," said Chanover. "She developed the idea for her project completely independently through literature searches, studying NASA's high-level planning documents, and talking with fellow Venus scientists at conferences.

"Candace has established a strong network of collaborators who can provide additional expertise to this project on issues ranging from photochemistry to solar flare processes, and she again did this with very little input from me. She is a careful researcher who works hard to broaden her skill set and knowledge in her subject area."

Gray, who joined the NMSU's Department of Astronomy, said she was "blown away" when she learned she had received the fellowship, since she had just recently started her research and had no results to show. She credits her success with the help and support of her professors at NMSU, who made sure she connected with the right people to conduct her research.

The $30,000 NASA fellowship can be renewed annually for up to three years. Gray said she expects to earn her doctorate in planetary sciences in 2015.