The aurora forecast is updated for April 9. Keep an eye out for our daily weather forecast update below and tour status as noted on the Anchorage Aurora Quest page. The Kp estimate is for the maximum level forecasted for the time between 10:00 p.m. and 4:00 a.m. Alaska time.
FRI APR 9 – Planetary K-Index [predicted]: Kp 2
SAT APR 10 – Planetary K-Index [predicted]: Kp 1-2
SUN APR 11 – Planetary K-Index [predicted]: Kp 1
Additional Information Affecting Aurora Viewing
Moon: The moon will be down all night, rising after sunrise at 7:26 a.m. (Apr. 10) as a 2:08% waning crescent. This phase of the moon will not interfere with viewing a quiet aurora display.
Solar Winds: Solar wind parameters are expected to be at nominal levels for the rest of 09 Apr. By late on 10 Apr through 11 Apr, a weak connection with a negative polarity Coronal Hole High Speed Stream (CH HSS) is possible.
Geomagnetic Field: The geomagnetic field is expected to be quiet on 09 Apr. Weak HSS effects are possible on 10-11 Apr causing unsettled periods.
Planetary K-Index provides an estimate as to how wide the auroral oval may extend. It does not indicate whether the aurora borealis will appear. The most important factors for aurora viewing are the solar winds and geomagnetic field – so note the information above on those. The Planetary K-Index is measured on a scale of 0-9. Anchorage is within the Kp3 zone (aurora visible overhead), but auroras are often seen here on the horizon as low as Kp1 (except for the early and late season, where a higher Kp is needed.) A fairly accurate Kp index can be determined up to 3-days in advance. For the Kp index indicated in the Anchorage northern lights forecast, that is the maximum Kp predicted during the prime aurora viewing time in the Anchorage area (generally between 9:00 p.m. and 4:00 a.m.). We do not provide the Kp level for a forecast period outside of nominal viewing times (i.e., local daytime).
Last Night’s Aurora
- The Planetary K Index reached Kp0-1 during optimal viewing hours.
- The maximum hemispheric power achieved last night was 14.9 at 3:05 a.m.
- Solar wind parameters were indicative of waning CH HSS influence. Solar wind speed decreased from approximately 475-400 km/s. The highest wind speed for Alaska viewing time was 424 at 3:11 a.m.
- The geomagnetic field was quiet. Total field ranged from 1-5 nT while the Bz component was between +/-3 nT. Phi angle was mostly positive. The best Bz component for Alaska was -3 Bz south at 11;53 p.m. and 1:40 a.m.
Current Aurora Ovation
Hemispheric Power is a measure of auroral activity that helps determine how bright and active auroras might be. It measures the rate of deposition of charged particles (mainly electrons and protons) into the atmosphere, where they collide with upper atmosphere particles and eventually stop. This process transfers their kinetic energy to the upper atmosphere. The higher the number, the more charged particles are depositing in the upper atmosphere. It’s measured on a scale of 5-150 GW [Gigawatts]. A power level of 20 or more is usually adequate to produce auroras visible to the naked eye. Hemispheric Power fluctuates and is a short range forecast that can be determined only up to around 30-90 minutes in advance with relative accuracy.