Of Particular Significance

Heads Up — Northern Lights Possible in Next 24 Hours

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 11/30/2023

[Note added: the predicted storm has begun, as of about 1000 UTC, 5:00 AM NYC time; good for early birds on the west coast and those in Asia.] If you live in Canada, Europe or the northern half of the US, keep an eye to the north late tonight and possibly tomorrow night. A series of solar flares occurred on the Sun in the last couple of days, and when their repercussions reach Earth, they may cause quite a storm in the Earth’s magnetic field… resulting in Northern Lights (Aurora Borealis). [There will be Southern Lights too, though the nights are short right now down south.]

Something to watch: https://www.swpc.noaa.gov/products/ace-real-time-solar-wind , data from the ACE satellite, serves as an early-warning system; if its readings start suddenly going crazy, that typically means a CME (coronal mass emission, i.e. a swarm of particles blown out of the Sun’s outer atmosphere [its corona]) has hit the satellite. Usually that means the CME is an hour at most from hitting Earth, at which point auroras become more likely; the stronger the CME, the more southerly the northern lights will usually reach.

Here’s a picture of some of the ACE data as of 10:30 NYC (330 UTC) time, showing that something already happened a few hours ago, right at around 2300 UTC, enough to start a mild storm. The expectation is that something more dramatic may happen soon, and if it does, you should start making tea to keep you warm when you go out to look.

Readings from the ACE satellite as of 330 UTC Dec 1 (10:30 pm NYC Nov 30); note the sudden jump in the readings at 2300, typical of an arriving CME.

More generally, there’s a lot of data at https://www.swpc.noaa.gov/ , though it is not very user-friendly. A lot of its information is delayed by 3 hours, which is not so useful when you’re trying to catch a fleeting opportunity!

Good spotting! I myself am out of luck again, due to exhaustion tonight and bad weather tomorrow. But we are approaching solar maximum, so we should get multiple chances in 2024.

Share via:


4 Responses

  1. Given that the sun is about 8 light minutes from earth, am I right in thinking that CMEs must move at a substantial fraction of the speed of light?

    1. The X-rays from a flare itself do move at light speed. But the CME from the flare, made of subatomic particles, takes a couple of days; the ACE spacecraft is about a million miles from Earth, so that tells you a CME’s particles move at a couple of million miles per hour, or of order a thousand miles per second. However, the speed varies; strong CME’s travel faster than weak ones. Also, the particles in a CME, mostly electrically charged, don’t travel in straight lines because of the non-zero magnetic field between the Earth and Sun.

    1. Not really. 🙂 I’m no expert. But there are two easy things to say: CME’s have been going on since the birth of the Sun, and life evolved to cope with them… as long as we stay on the ground. The impact on people who are often at high altitude — pilots, flight attendants, and frequent air travelers — is potentially more significant and one should be aware of it. However, studies seem to show that it is quite limited, and that occasional air travelers are not at risk. For instance: https://hps.org/publicinformation/ate/faqs/solarflare.html .

Leave a Reply


Buy The Book

A decay of a Higgs boson, as reconstructed by the CMS experiment at the LHC


It’s always fun and interesting when a measurement of an important quantity shows a hint of something unexpected. If yesterday’s results from DESI (the Dark

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 04/05/2024

I hope that a number of you will be able to see the total solar eclipse next Monday, April 8th. I have written about my

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 04/01/2024