Explore the Universe - Aurorae

During times of minimum solar activity in the solar cycle coronal holes are chiefly responsible for geomagnetic storms on Earth.  A coronal hole is a region in the Sun's corona that is cooler and magnetic field lines stretch out away.  The magnetic field lines reach into space and it causes hot gases to escape.  The region typically looks darker because the particle density is much lower.

The solar wind is enhanced at these regions.  When a coronal hole is on the face of the Sun pointing directly at Earth there is an increased chance of geomagnetic disturbances.  These disturbances can typically be seen as an aurora.  For more information about a coronal hole please see the following link.

https://www.spaceweatherlive.com/en/help/what-is-a-coronal-hole

Coronal Hole #82, April 21, 2017 (www.spaceweatherlive.com)

An enhanced solar wind may cause the aurora to be seen at lower latitudes.  In April of 2017 reports were coming in from the US border (49°N) that the aurora could be seen.  We were at the observatory that night and had quite a show that lasted for about 10 minutes starting around 22:55.

In the optional observations in the Solar System section of the Explore the Universe certificate, the aurora is listed.

**As a side note the dictionary refers to the singular as Aurora Borealis and I've seen the plural as Auroras, Aurorae Borealis, Aurorae Borealises and Aurorae Boreales.

I'm not sure why the first three plurals are used except perhaps people nowadays have forgotten the Latin etymology.  Declining the first declension noun Aurora and the third declension adjective Borealis will give Aurorae Boreales.  I will use that as the plural until I find reasoning otherwise.**

April 2017 we first saw a green haze in the distance toward the North.  A few minutes later there were multi-coloured pillars extending vertically in the sky.  At one point a large streak of light extended to a point just above the southern horizon.  The lights were so bright it was interfering with observations through the telescopes; I do not think anyone minded the interruption though.  I quickly used my camera to take 5 second exposures at ISO 1600, F/4.5 with a 15 mm focal length.  These are shown below.

Streak above the observatory

Streaks and pillars of multiple colours (Constellation: Auriga)

Streak extending across the sky

If you would like to observe the aurora there are some good websites to check out that predict its occurrence.

First there is my February blog post on the subject:

http://simonjastronomy.blogspot.com/2017/02/what-is-aurora.html

My favourite site for aurora predictions is Aurorasaurus:

http://www.aurorasaurus.org/

For more extensive solar data SpaceWeatherLive is really good too:

https://www.spaceweatherlive.com/

Finally I really like SolarHam for daily images of sunspots and coronal holes:

http://www.solarham.net/

I hope you have the opportunity to witness this remarkable phenomenon.  Keep your eye on the live maps to see if it will be in your area!