The ESA Solar Orbiter spacecraft is currently studying the sun. Among the discoveries made by the spacecraft so far is a surprising number of small, very bright regions in the hot solar corona that have not been discovered by other spacecraft. Tiny flares were discovered in the measurement data collected from the Extreme-Ultraviolet Imager (EUI) taken during the instrument’s commissioning in space last year.
The team says that eruptions occur much more frequently than larger flames that occur in the sun. The researchers believe this may be one of the missing pieces of the puzzle they need to explain the “almost inconceivably” high temperatures in the solar corona. The duration of these small flames is 10 to 200 seconds and are known as solar fires.
The temperature of small fires reaches between 1 million and 1.6 million degrees Celsius. Although they are described as tiny, they are actually between 400 and 4,000 kilometers in length and extend 1,000 to 5,000 kilometers above the sun’s photosphere. The solar corona is extremely hot with a temperature of around 1 million degrees Celsius, while the photosphere has a temperature of around 5,500 degrees Celsius.
Researchers have long tried to determine what makes the Sun’s outer atmosphere hotter than its surface, and that question is one of the biggest mysteries in solar physics. The researchers say that computer simulations indicate that reconnection boosts campfires and can generate enough energy to maintain the crown’s temperature.
Solar fires emit extremely short, high intensity ultraviolet light for short periods of time. In the images, they appear as small bright spots. So far, the team has studied the properties of 1,500 campfires, offering the most comprehensive characterization of the phenomena of all time. A study on campfires will be published in the coming weeks.