What does Kp index mean for aurora photography
The Kp index is the most critical indicator for aurora photographers. It helps to predict the location, position in the sky, activity, shape, and even the colors of the aurora.
The active aurora in the sky in Finland when Kp index is 3
According to the Space Weather Prediction Center, which provides all sorts of geomagnetic activity forecasts and observations, the Kp index is a good indicator of the aurora. Moreover, the aurora's location and brightness directly correlate with Kp.
It means that if you know the Kp index forecast, you can predict all the parameters of the aurora with some level of certainty. Let's talk about each of them.
Visibility of the aurora
Low Kp0-Kp2 implies a faint aurora. You usually can't even see it at the lowest Kp level with the naked eye. But you can capture it with your camera. At Kp3-Kp4, it gets easily visible. At Kp5 or higher, the aurora is so bright that it can illuminate the landscape. Even full mon can't prevent you from taking pictures of such a brilliant aurora.
Location of the aurora
The higher Kp is, the further from the poles the aurora extends. Knowing if it will reach your location is crucial if you are outside the polar region. Read here what Kp you need to see the aurora.
The aurora’s position in the sky
As a logical consequence of the previous paragraph, the Kp index tells you whether you can expect the aurora overhead or on the horizon. Agree that it's essential information for planning your composition in advance.
Activity, shape, and colors of the aurora
When the level of geomagnetic activity is low, the aurora usually has the shape of a bow and doesn't move. And it shows the first signs of movement at Kp2. In the pictures, its color is green, but the human eye can't detect the color of such a dim light, and it looks grey. So, you must take a photo and check whether it's the aurora or a cloud. Rarely, there is a faint red glow above the green bow. A low Kp index doesn't look so exciting, but you can take incredible photos with the green light in the background.
At Kp3-Kp4, the aurora becomes bright and active. It usually has the shape of curtains moving in the wind. You can easily see the green color of the aurora with the naked eye. Sometimes the low edge is bright pink, and the top part could be red or purple.
Kp5 and higher are considered geomagnetic storms. That's where the magic happens. The aurora is bright and moving very fast. If you are in the right location, it could be dancing all over the sky in green, purple, pink, and red colors. Sometimes it's like hundreds of arrows are piercing the sky. It would be best to have a wide lens to get the landscape and as much sky as possible in the frame.
