Strong Thermal Emission Velocity Enhancement (STEVE)

Introduction

Recent highlights include the crucial role of citizen scientists in identifying and documenting STEVE. There is potential in studying STEVE to unravel the mysteries of its origin, creation, physics, and nature. The name “Steve” is now an homage to the initial, informal name given by the discoverers and represents Strong Thermal Emission Velocity Enhancement.

Atmospheric Optical Phenomenon

STEVE is an atmospheric optical phenomenon that has similarities to the Aurora Borealis and Australis. However, unlike the auroras, which are caused by the interactions of particles like electrons and protons with the Earth’s atmosphere, STEVE is caused by hot gases.

Appearance

STEVE manifests as a thin ribbon of purple and green light visible in the sky. This distinctive feature sets it apart from typical auroral displays.

Naming

The phenomenon was named in late 2016 by a group of aurora watchers from Alberta, Canada. The name STEVE was initially a placeholder, but it has since been adopted formally to represent Strong Thermal Emission Velocity Enhancement.

Primary Feature

The primary feature of STEVE is a purple or mauve color arc that is approximately east-west aligned. This is distinct from the equatorward boundary aurora, which has a different color palette and alignment.

Altitude Profiles

The altitude profiles of STEVE have been determined during specific events, such as the one on July 17, 2018. These profiles have been measured using calibrated photographs taken by citizen scientists.

Continuum Spectrum

The continuum spectrum of STEVE has been explained through spacecraft observations. It is known to co-occur with subauroral ion drifts, which are typically invisible plasma flows.

Discovery and Research

The discovery and ongoing research of STEVE are significantly bolstered by citizen science contributions.

Citizen Science Contributions

Reports of STEVE have been shared in online forums, with an example being 30 reports between 2015 and 2016. Projects like Aurorasaurus, funded by NASA and the National Science Foundation, track aurora borealis through user-submitted reports and tweets.

Ground and Satellite Views

STEVE has been observed for the first time from both ground and space. These observations have been documented by all-sky cameras run by the University of Calgary and the University of California, Berkeley, as well as the Swarm satellite of the European Space Agency (ESA).

Importance in Research

Research on STEVE helps in understanding Earth’s magnetic fields and their interaction with charged particles in space. It provides valuable insight into the chemical and physical processes in Earth’s upper atmosphere, as well as their effects on the lower parts of the atmosphere.

Characteristics and Behavior

STEVE is not a normal aurora. While auroras typically occur globally in an oval shape and can last for hours with primary colors of greens, blues, and reds, STEVE is characterized by a purple color with a green “picket fence” structure and lasts for a shorter duration.

Creation Process

The process begins with the Sun sending charged particles toward Earth, which applies pressure on the magnetic field. This leads to magnetic reconnection, an explosive process that causes a glow in the upper atmosphere, generating both auroras and STEVE.

Uniqueness

STEVE is unique in that it travels along different magnetic field lines than the aurora and appears at lower latitudes, such as in southern Canada. It comprises a fast-moving stream of extremely hot particles, known as subauroral ion drift (SAID), which was previously studied without a known visual effect.

Location

STEVE is observed in the subauroral zone, at lower latitudes than most auroras, in an area that has not been well researched.

Connection to Auroras

STEVE often appears in the presence of auroras, indicating a chemical or physical connection between the higher latitude auroral zone and the lower latitude subauroral zone.

Challenges in Studying

The study of STEVE poses challenges as simultaneous ground and space recordings are rare. The Swarm satellite orbits the Earth every 90 minutes, and since STEVE can last up to an hour in a specific area, capturing it becomes a challenge of perseverance and probability.

Conclusion

STEVE represents a vibrant example of community involvement in scientific discovery, bridging the gap between amateur enthusiasm and professional research, enriching our understanding of atmospheric phenomena.