Category Archives: Tips

How To Read The WSA-Enlil Model Output

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When there is a solar storm on its way towards Earth, or when there is a geomagnetic storm watch posted (as in the watch currently in effect), we often post an image of the WSA-Enlil model output. WSA in the name is an acronym of the three researchers who contributed to the model, Drs. Wang, Sheeley and Arge. Enlil in the name comes from the Sumerian God of wind and storms.

The model output can be confusing or disorienting at first. The following is a walk through of some features which should help in understanding how to read the output. We’ll use a snapshot of the today’s output (click for a larger view)

WSA-Enlil Model Output Jan 24, 2015
Labeled WSA-Enlil Model Output Jan 24, 2015

The two main features on this image are higher than average proton density expected to arrive this evening and the large area of high speed solar wind expected to arrive Wednesday from the southern coronal hole. We’ve labeled the image, here is a quick guide:

Label “A”: This is Earth! The left two radial graphs show the Solar System from the north think of is as “from above”, The Sun is in the center. The red and blue circles on the other side of the Sun are the two satellites (Stereo ahead and Stereo behind. At the time on the snapshot, plasma density at Earth is elevated but decreasing.

Label “B”: The two sets of graphs on the right show the data over time, the yellow bar shows the point in time the radial graphs are displaying. The plasma density, or the amount of material moving through space, is shown in the upper graph. The bottom shows the speed that material is moving as it arrives at the measurement location. Label B shows Stereo A (ahead), was seeing increased plasma density during the first part of Jan 23. The space weather at this location has no impact on geomagnetic conditions at Earth. We sometimes see people excited that the levels are increasing at this remote satelite wondering if there will be aurora – probably not, sorry.

Label “C”: This small increase in density shown is responsible for this evening’s predicted geomagnetic storm. The plasma density is elevated, you can see looking at the date along the bottom of the graph that this is likely to peak towards the end of the 24 hour period.

Label “D”: The two meridional slices (the image between the circle and the graph) show a side view of the Earth and the Sun. Above the earth is what is happening in space above our North Pole, below is the South Pole. In this image, we’ve freeze-framed the video at 19:00 UTC on 1/28, next Wednesday. There is a large area of high speed wind (orange and red) south of Earth that is coming from the Large Southern Hemisphere Coronal hole shown below in AIA 211 as the dark area.

Southern Coronal Hole on 1/24/2015 in AIA 211
Southern Coronal Hole on 1/24/2015 in AIA 211

Finally, Label “E”: This graph shows the expected solar wind speed at the same three measurement locations. This shows an increase to 500 km/s. This increase is related to the high speed wind from the coronal hole reaching a little father north. If this increase in solar wind is accompanied by an increase in plasma density because of an Earth-directed eruption on the Sun’s surface, we may see an additional geomagnetic watch and again have the possibility of seeing Aurora.

The NOAA Space Weather Prediction Center makes the WSA-Enlil model output available on their site.

Happy Hunting

Last Minute Aurora Viewing Preparation Guide

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We wait a long time before the is an opportunity to potentially see the Aurora Borealis. Conditions have to come together just right. There has to be a sun spot, it has to be in the correct location on the solar disk, it has to have the correct magnetic complexity, it has to produce a solar flare, the solar flare has to be directed towards Earth. All of those elements give you a 3 day window to know when there *might* be Northern Lights visible. Then the weather has to be clear, the flare has to hit Earth when it is nighttime at your location, and it helps if the Moon is in the right Phase.

All of those elements are coming together tonight. Here’s a last minute check-list you can use any time you are going to go out viewing Aurora.

1) Is there a potential storm?

Generally, the Space Weather Predicition Center will issues alerts when there might be a light show. These will be rated G1, G2 and G3 – three being the most likely to see northern lights the furthest south. Tonight – there is a G3 watch posted.

2) Will it be clear?

Aurora happen in the uppermost part of the atmosphere. If it is cloudy, you won’t see aurora. The easiest way to tell if it is clear is to stick your head out the window. If you are locked in an office, you can check cloudiness on your local weather. If you live in the United States, the Weather Channel Website offers a current and predicted map of cloud cover over the next 4-6 hours.

3) Is it dark?

This sounds obvious, but it has to be dark to see Aurora. The darker the better. Choose a viewing location that has as little light pollution as possible. If you live near big cities, get as much of the light from them to your back as possible. The moon produces light too. You can view current Moon phases at SunriseSunset, enter your location and be sure to check the box to display moon phases and moonrise and moonset. If at all possible, time your viewing for after moonset or before moonrise.

4) Is the Kp high enough?

Know your local Kp value. Kp is a global average of Geomagnetic activity happening on Earth. The scale ranges from 0 – 9. This handy map will show you what Kp value you need to possibly see Aurora at your location. Track the current and near-term predicted Kp values on Northern Lights Now’s Live KP page. You will see near term predicted Kp values on the right sidebar.

globeNW

5) Are you dressed warmly enough?

When waiting for Aurora, you will likely sit outdoors for hours before you see anything (unless you are LUCKY!). It will be night, and it will probably be cold. Make sure to wear enough layers. Wear layers like you would if it was about 20 degrees colder than the actual temperature.

6) Are your camera and tripod ready?

You don’t have to take pictures of Aurora, but many people like to. Most standard digital Cameras will do a good job capturing Aurora, but you may need a 20-40 second exposure. You will definitely need a tripod.

7) Are your expectations correct?

Many people hunt Aurora their entire life and don’t get to see it. It is a rare and exciting moment when it happens. But many factors have to come together just right for you to see them. If you don’t see Northern Lights this time out, keep your hopes up, you may get to see them next time.

If you do see northern lights, we’d love to hear your stories and see your picture!

Good Luck

Short Term Prediction Down? Use This!

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The solar flares that are producing the predicted geomagnetic storms (1/8/2014 – 1/10/2014) have also produced a solar radiation storm at level S2. This solar radiation storm has temporarily taken the ACE (Advanced Composition Explorer) satellite out of service. The data this satellite collects is one of the main inputs used for short term Kp prediction.

The data from ACE is used when estimating the short term Kp values – the ones you see in the sidebar. When this data is bad, there are two alternatives. First, the USAF reports the current Kp index every three hours. NLN will post the USAF current Kp value in the side bar when the short term Kp values are not dependable.

Second, the NOAA Ovation model predicts the near term 30-45 minute current Northern Hemisphere Aurora visibility. This model works well for Kp values under 7, but is not proven yet for higher Kp values. Here is the current Ovation model output for the northern hemisphere.

Ovation forecast model - Northern hemisphere

Hopefully if you came to this post because the ACE satellite is down, it will be back up soon!