Decoding Celestial Secrets: When a Phenomenon Named STEVE and the Green 'Picket Fence' Masquerades as Auroras

The aurora borealis and aurora australis, known as the northern lights and southern lights respectively, are one of nature's most spectacular sights. These phenomena result from solar energy interacting with Earth's atmosphere, concentrated by magnetic fields at the poles, predominantly visible in polar regions.

But what if another phenomenon on Earth's night sky is masquerading as an aurora? How does this happen, and when is it typically observed?

Meet STEVE: Colorful Bands of Light That Looks Like an Aurora

Claire Gasque, a UC Berkeley physics graduate student, proposes a novel explanation for aurora-like phenomena, distinct from traditional auroras. Collaborating with researchers at the Space Sciences Laboratory, she suggests launching a NASA rocket into the aurora to test her hypothesis.

As the Sun enters its active 11-year cycle, the increasing occurrence of vibrant auroras and phenomena like STEVE (Strong Thermal Emission Velocity Enhancement) and the picket fence provides an opportune moment to study these rare events triggered by solar storms and coronal mass ejections.

In a recent study, titled "It's Not Easy Being Green: Kinetic Modeling of the Emission Spectrum Observed in STEVE's Picket Fence" published in the journal Geophysical Research Letters, Gasque and her team explained the physics behind it.

Auroras, triggered by solar storms and coronal mass ejections, result from ions colliding with oxygen and nitrogen in Earth's atmosphere, emitting green, red, and blue light. In contrast, STEVE, observed as purple or mauve light with a green picket fence, emits no blue light and occurs at lower latitudes than auroras.

The study proposes that STEVE and the picket fence are generated by low-altitude electric fields parallel to Earth's magnetic field, distinct from the mechanisms of traditional auroras.

Moreover, the findings suggest that the light from the picket fence is created by particles energized by a parallel electric field in space, a mechanism different from known auroras.

Brian Harding, a co-author, notes that Claire Gasque's research reveals exotic physics behind STEVE and demonstrates that parallel electric fields can explain its unique spectrum. While the energized particles likely don't originate from the sun, the study suggests that solar storms still trigger these phenomena by disrupting Earth's atmosphere.

Rocket Mission to Unravel Celestial Mysteries

The next phase involves launching a rocket from Alaska through the observed phenomena to measure the strength and direction of electric and magnetic fields. Scientists at the Space Sciences Laboratory (SSL) initial target for measurement is an enhanced aurora, which resembles a normal aurora but with picket fence-like emissions.

The goal is to launch a rocket through the enhanced aurora to measure parallel electric fields, enhancing our understanding of the upper atmosphere, ionosphere, and Earth's magnetosphere, as the enhanced aurora, marked by bright layers resembling the picket fence, is believed to be more commonly shaped by parallel electric fields.

The researchers propose launching a second rocket to measure particles at higher altitudes, differentiating the conditions causing these phenomena from those leading to traditional auroras. The team expects to hear back from NASA in the first half of 2024 regarding the selection of the proposed sounding rocket campaign, aligning with NASA's Low-Cost Access to Space (LCAS) program.

The rocket experiment is crucial for grasping the upper atmosphere, ionosphere, and Earth's magnetosphere, highlighting the need for future studies on electric field generation, their association with waves, and their impact on energy transfer, with Gasque valuing insights from collaborators studying the middle ionosphere and stratosphere.

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