{"id":772,"date":"2020-02-12T12:00:39","date_gmt":"2020-02-12T12:00:39","guid":{"rendered":"https:\/\/aurorasaurudev.wpengine.com\/?p=772"},"modified":"2023-12-26T21:50:08","modified_gmt":"2023-12-26T21:50:08","slug":"laura-learns-aurora-holey-corona-batman","status":"publish","type":"post","link":"https:\/\/blog.aurorasaurus.org\/?p=772","title":{"rendered":"Laura Learns Aurora: Holey Corona, Batman!"},"content":{"rendered":"

Laura here! I am an aurora enthusiast, but new to the science side. Fortunately, the Aurorasaurus blog and website are full of great resources. Join me in learning more about auroras! ?<\/span><\/p>\n

This week, ESA Solar Orbiter<\/a> blasted off to join NASA’s Parker Solar Probe<\/a> in studying the Sun.\u00a0Solar Orbiter\u00a0will be\u00a0looking specifically at\u00a0the Sun’s poles, including coronal holes. One of these huge structures faced the Earth<\/a> this past Saturday, sending particles hurtling our way. What are coronal holes, and how do they affect aurora? Solar physicist Michael S. Kirk explains.<\/p>\n

“Holey Corona, Batman! What are all of those dark areas on the sun?” by\u00a0Michael S. Kirk was originally published February 2, 2017.<\/em><\/p>\n

\"Image
Image of the sun from the Solar Dynamic Observatory with darker regions, known as coronal holes, labeled. Source: NASA<\/figcaption><\/figure>\n

[Update: DKIST<\/a> is now the most powerful solar telescope in the world and recently sent back\u00a0its first images of the sun<\/a>! Solar Probe+ was renamed Parker Solar Probe<\/a> and has just\u00a0begun its fourth solar encounter. It reached perihelion on Wednesday, January 29, 2020. Whole Heliosphere & Planetary Interactions (WHPI)<\/a> is seeking ground-based observations to complement Parker’s data. More information here<\/a>.]<\/p>\n

When we look at the lowest and middle layers of the sun, it appears relatively uniform with small dark (sunspots) or bright (active regions) blemishes. However, when we look at the outermost layer of the sun\u2019s atmosphere, the corona, something bizarre happens \u2013 large chunks appear to be missing. These large dark regions are called coronal holes and are some of the most fascinating solar features we routinely observe.<\/p>\n

Both casual and scientific descriptions of coronal holes have been documented as far back as the early 1900s during solar eclipses. They were first noticed as rays of light streaming out from the solar poles, which appeared similar to the magnetic field lines of a bar magnet. The first direct images of coronal holes on the disk of the sun didn\u2019t start until early in the space age. In the late 1960s and early 1970s, they could be seen as isolated dark patches in UV and x-ray images. The definition of these dark patches was refined to be what we know now as coronal holes by solar instruments on the Skylab space station in 1973 and 1974. The Skylab data and subsequent rocket missions helped to define characteristics of these holes. They routinely appear as dark caps in both the north and south poles of the sun and as large, often stretched-out expanses in mid-latitude and equatorial regions.<\/p>\n