NASA’s Solar Dynamics Observatory, or SDO, captured this solar image, which clearly shows two dark patches, known as coronal holes. The larger coronal hole of the two, near the southern pole, covers an estimated 6- to 8-percent of the total solar surface.
While that may not sound significant, it is one of the largest polar holes scientists have observed in decades. The smaller coronal hole, towards the opposite pole, is long and narrow. It covers about 3.8 billion square miles on the sun – only about 0.16-percent of the solar surface.
Coronal holes are part of the Sun’s corona and are constantly changing and reshaping because the corona is not uniform. Coronal holes are areas where the Sun’s corona is darker, and colder, and has lower-density plasma than average because there is lower energy and gas levels.
The sun contains magnetic fields that arch away from areas in the corona that are very thin due to the lower levels of energy and gas, which cause coronal holes to appear when they do not fall back. Thus, solar particles or solar wind escape and create a lower density and lower temperature in that area. The aurora borealis that is seen at the northern and southern poles are the result of solar wind entering the Earth’s atmosphere.
Coronal holes are lower density and temperature regions of the sun’s outer atmosphere, known as the corona. Coronal holes can be a source of fast solar wind of solar particles that envelop the Earth.
The magnetic field in these regions extends far out into space rather than quickly looping back into the sun’s surface. Magnetic fields that loop up and back down to the surface can be seen as arcs in non-coronal hole regions of the image, including over the lower right horizon.
The bright active region on the lower right quadrant is the same region that produced solar flares last week.
SOLAR DYNAMICS OBSERVATORY
The Solar Dynamics Observatory (SDO) is a NASA mission which has been observing the Sun since 2010. Launched on February 11, 2010, the observatory is part of the Living With a Star (LWS) program.
The goal of the LWS program is to develop the scientific understanding necessary to effectively address those aspects of the connected Sun–Earth system directly affecting life and society.
The goal of the SDO is to understand the influence of the Sun on the Earth and near-Earth space by studying the solar atmosphere on small scales of space and time and in many wavelengths simultaneously.
SDO has been investigating how the Sun’s magnetic field is generated and structured, how this stored magnetic energy is converted and released into the heliosphere and geospace in the form of solar wind, energetic particles, and variations in the solar irradiance.
SDO has three scientific experiments:
- Atmospheric Imaging Assembly (AIA)
- EUV Variability Experiment (EVE)
- Helioseismic and Magnetic Imager (HMI)
SDO’s goal is to understand, driving towards a predictive capability, the solar variations that influence life on Earth and humanity’s technological systems by determining
- how the Sun’s magnetic field is generated and structured ?
- how this stored magnetic energy is converted and released into the heliosphere and geospace in the form of solar wind, energetic particles, and variations in the solar irradiance ?
SDO study how solar activity is created and how Space Weather comes from that activity. Measurements of the interior of the Sun, the Sun’s magnetic field, the hot plasma of the solar corona, and the irradiance that creates the ionospheres of the planets are our primary data products.