Since the presentation, I’ve done more research & produced this guide. Hope you find it helpful.
Know When to Look for the Aurora Borealis in Oregon and Washington
The aurora borealis (or australis) is one of nature’s most awe-inspiring things to see. While an aurora can frequently be seen in the far north, you can sometimes see it here in the Pacific Northwest and frequently photograph it with sensitive equipment. This guide will tell you how to know the best times and where to go looking for the aurora in Oregon and Washington.
Sun spot activity on the sun is partially responsible for the solar storms that produce aurora. These follow a roughly 11-year cycle and this one peaked in the last couple of years. Large solar flares and corona holes that can produce aurora usually occur during the 3 to 5 year period after the peak of sunspots. So aurora viewing could be especially good for another few years.
This guide is based on an analysis of the past four years of Oregon and Washington aurora photos on Flickr and NOAA’s index of disturbance of earth’s magnetic field – Kp. I sifted through hundreds of photos. The disturbance of earth’s magnetic field by the solar winds or storms is one of the main causes of aurora. This imperfect data gives us a solid basis for knowing when to look for aurora and clearly demonstrates we can be successful here.
NOAA and NASA have published maps showing what areas of the globe are likely to have viewable aurora for a given level of magnetic disturbance based on satellite observations.
But aurora occurs at altitudes of 35 to 600 miles so it is possible to see or photograph at least the top of an aurora display much further south than indicated by these maps.
The aurora was photographed in Washington 6 to 22 nights each year from 2012 through 2015 for an average of 13 nights per year. For Oregon the numbers were 7 to 14 nights for an average of 10.5 nights a year. This period covers solar maximum years so will not reflect what happens during solar minimum years. There were only 10 nights when aurora was photographed in Washington but not in Oregon over the whole four years and several where the reverse occurred. There were several brilliant aurora such as 9/11/2015 that were captured and posted by as few as two photographers. June and July produced the most frequent aurora photos in both states probably due to clearer sky. October (near the equinox) produced the third largest number of captures of any month. The aurora frequency of occurrence is much higher during the months around the equinox – March, April and September, October. This is when the earth’s magnetic field is more aligned with the sun’s.
Comparison of NOAA’s 3-hour magnetometer measurements, the Kp Index, with the dates when aurora was photographed across the two states confirms useful patterns. During the last four years, there were 11 evenings with Kp=>7 with 2015 being a banner year having 5 of those events. Aurora was photographed in either state on all but 3 of these 11 nights and those three nights had clouds and/or a full moon.
The aurora were often photographed when 3-hour Kp=5 and even lower. For half of all nights aurora was photographed, 3-hour Kp was lower than 5. This can happen if Kp spikes up for a short time and produces an aurora in the PNW but the 3-hour value never gets to 5 or even 4. Perhaps 1/4th of nights that had 3-hour Kp=5 or 6 had an aurora photo captured and posted during the summer and fall months. That seems pretty often considering our frequent cloudiness.
Over the last four years, there were an average of 31 nights per year with 3-hour Kp=>5 (range: 15 to 67 per year) and again 2015 was the most active year with more than half of all Kp=>5 nights for the four years. Clearly, there is large variation between years so it could take a few years of effort to get an aurora image in Oregon or Washington.
There are geographic differences. It is very rare for aurora captures from Oregon to show the characteristic brightest color, a chartreuse green, and they are lower on the horizon than found in Washington. The top of an aurora display most often seen in Oregon is typically red and violet – colors the human eye is less sensitive to but digital cameras can see during longer exposures. This will make recognizing an aurora display harder especially if you have never seen one and do not know what to watch for when the aurora is dim. Watch for faint grey cloud like formations that move differently than clouds. Sometimes aurora is static for long periods however. Be sure to search Flickr yourself. This time-lapse of a distant aurora australis gives a good idea of what might be visible to the eye and what the digital capture might look like: https://youtu.be/oq6GO-i7t4Y Airglow will show the same green as aurora in the camera but does not move and will be visible in every direction. Light pollution is typically yellow orange.
How to know when to consider chasing aurora
Armed with this information, we now know what NOAA forecast Kp levels to watch for to time our search for an aurora here. We start with the long range 27-day forecast published on Mondays: http://www.swpc.noaa.gov/products/27-day-outlook-107-cm-radio-flux-and-geomagnetic-indices . Click and read the Details tab on this page to better understand this forecast. After the peak of a solar cycle, you can add 28 days (one solar rotation) to the dates given in this forecast to get an idea of when active periods are likely to occur during the next two months. Note especially days with highest Kp=5 or greater.
Next turn to the 3-day forecast that is updated every 12 hours: http://www.swpc.noaa.gov/products/3-day-forecast and again watch for Kp=>5. These two forecasts can be used to make adjustments to North Country travel plans or to grab your Go-bag and head to a pre-identified shooting location for an evening. Forecasts are given in universal time, UTC, which is 8 hours before PST so be sure to make the needed conversion. For some hours, conversion includes a date change. Pay particular attention to any hourly forecast Kp=>5 for the UTC hours 0000 (midnight) through 1100 as these times are for our evening and night times. Having Kp reach high levels during our daytime will not produce an aurora we can see so you can ignore other times. Recent and current measured 3-hour Kp levels can be found at: http://www.swpc.noaa.gov/products/planetary-k-index to update an older forecast.
Short term forecasts can be accessed via a smart device while you are traveling to a shooting location to help you know of recent changes: NOAA 1 & 4 hr. forecasts: http://www.swpc.noaa.gov/products/wing-kp NOAA 30 min.: http://www.swpc.noaa.gov/products/aurora-30-minute-forecast
Again, be sure to read the details to understand these somewhat complicated charts. Short-term forecasts are useful because aurora sub-storms can occur 2-3 times a night and cause the aurora to move southward and intensify.
There are also several alert services. U of A Fairbanks provides an all in one format for these long and short-term forecast: http://www.gi.alaska.edu/AuroraForecast/Alaska NOAA will send emails for any G1 (Kp=>5) or higher forecast storm. Sign up is here: http://www.swpc.noaa.gov/news/receive-swpc-alerts-and-warnings . These can help you know when to pay close attention to more detailed data but are only helpful if you monitor your email at least daily. It is easy to miss an email alert.
For a fee, there are a number of alert services and an app that will send alerts via text or twitter. I have no experience with any of these – caveat emperor:
Astronomy North: http://astronomynorth.com/aurora-forecast/
AuroraMax Twitter Alerts: https://twitter.com/AuroraMAX?ref_src=twsrc%5Etfw
Custom Alerts: https://twitter.com/Aurora_Alerts
Real Time Space Weather: https://twitter.com/_SpaceWeather_
Aurora Service N.A.: http://www.aurora-service.org
Aurora Alert App: http://www.aurora-alert.com
Picking a location and times to go shoot
Check the weather and moon phase. The web site http://www.cleardarksky.com/csk/index.html provides detailed information on visibility and darkness in a compact format for 2.5+ days out for a number of known dark sites. Pick one close to your chosen location. Again read the details. Accuweather and others provide hourly cloud cover forecasts for more locations but lacks information about light pollution, moon light and visibility factors: http://www.accuweather.com/en/north-america-weather Both sites rely on NOAA cloud cover forecasts – a difficult area of weather forecasting. Be aware of what astronomers call a “sucker hole”. That’s a break in the clouds that’s moved somewhere else by the time you get there.
This aurora/weather forecasting workflow works equally well for locations much further north. The surprise from this analysis is that Kp 5 and lower levels can produce visible aurora here in the PNW. In the aurora belt up north, aurora often occurs when Kp is 2.
High elevation and dark conditions will help for seeing the top of a dim aurora from Oregon or Washington. A quarter moon or less may be ok but a bright moon will interfere with all but the brightest aurora. Get out of the trees. Avoid being close to any geography where much of the northern horizon is obscured. Favorite locations are high lakes with a distant mountain on the north side and road access. Cascade range lakes, Trout Lake, Trillium Lake, Sparks Lake, Paulina Lake and Crater Lake, are examples. High valleys, the Methow, and eastern fields/deserts are also used. The east sides of our states have more clear nights.
The best time of night for aurora is generally 10 pm to 2 am local time. However 2/3rds of PNW aurora photos with capture time data were made before midnight PST. But the aurora belt typically moves the furthest south at magnetic midnight when your location is aligned with the magnetic pole and the sun on the opposite side of the earth. That is well after midnight PST. So seriously consider shooting into the early morning hours. Some of my best aurora captures in the Yukon were after 2 a.m. Other nights, it faded after that.
Aurora is most likely to appear from NW to NE except for intense displays. Look and aim the camera in this direction but consider optional compositions should the aurora appear at one end of this band. Except during intense events, the aurora will be low on the horizon so you might start with the camera in landscape orientation. Expect to need high ISO >800, a wide fast lens and a camera with good high ISO performance. Sometime during the night, shot a starry night landscape photo so that you get a satisfying image from your efforts even if there is no aurora. Search Flickr for ideas.
If you are not shooting time lapse or star trails, perhaps set the camera for one 20 second exposure, ISO 3200, f2.8 every minute or two for as long as your battery will last or the aurora appears. Clearly, you’ll need to periodically check the monitor to find out if the camera is seeing something you don’t and to adjust exposure and camera direction if needed. Do not assume that you should stop shooting because you haven’t seen anything. The aurora may only be active for 15 minutes on some nights. Success will come from frequent shooting.
As mentioned, many aurora photos were captured when 3-hour Kp levels were below 5. If you happen for other reasons to be in a good location that provides the needed visibility, consider setting up a camera with interval shooting whenever Kp is forecast to be above 2. You might have the same success many other PNW photographers have had.
Be safe shooting at night. Scout your location and possible compositions during the day. Know how to get back to your car/dwelling/camp in the dark. Some locations might warrant using portable GPS for nighttime way finding. Bring a dim red light, two flashlights, food, water and appropriate clothing. Tell someone where you are going. Get out there and good luck!