Chromosphere

BBSO full-disk H-alpha 2002-07-26 153931 color

Solar eclips 1999 5

The Solar Chromosphere at the highest possible resolution

Chromosphere is a layer of the Sun's atmosphere located above the photosphere and below the corona. It is approximately 2,000 to 3,000 kilometers deep. The name "chromosphere" comes from the Greek words chroma, meaning color, and sphaira, meaning sphere, referring to the reddish color of this layer, which can be seen during a solar eclipse. The chromosphere is less dense than the photosphere, and is composed mainly of ionized hydrogen, which gives it its characteristic red color due to the H-alpha emission line.

Structure and Features

The chromosphere is characterized by a variety of features including spicules, filaments, and plages. Spicules are small, jet-like projections that extend into the corona from the top of the chromosphere. Filaments are large, dark structures that appear when viewed against the bright background of the Sun, and are essentially dense, cool gas suspended over the chromosphere by magnetic fields. Plages are bright regions associated with sunspots, found in the chromosphere. These features are driven by the Sun's complex magnetic field.

Temperature

Unlike the photosphere, which has a nearly uniform temperature, the chromosphere's temperature increases with altitude, ranging from about 6,000 K at its base to upwards of 20,000 K at its top. This temperature increase is a result of the heating mechanisms that dominate in this layer, including magnetic reconnection and wave heating.

Observation

Observing the chromosphere directly is challenging because it is less bright than the photosphere. However, it can be observed with specialized instruments like the spectroscope during solar eclipses, or at times using filters that isolate the H-alpha emission line. The solar telescopes equipped with these instruments can provide detailed images of the chromosphere's features.

Importance

The chromosphere plays a crucial role in the dynamics of the Sun's atmosphere. It is the region where the solar wind begins to form, which has implications for space weather and its effects on Earth. Understanding the chromosphere is essential for predicting solar flares and other solar activities that can impact satellite operations, communications, and power grids on Earth.

Research and Exploration

Research into the chromosphere is ongoing, with missions like the Parker Solar Probe and the Solar Dynamics Observatory (SDO) providing valuable data. These missions help scientists understand the physical processes that heat the chromosphere and drive solar activity.