‘No Apocalypse In Sight!’ A Heliophysicist Takes Us Behind The Solar Flare Headlines

Have you seen some scary-sounding headlines about the sun lately? I certainly have, and I wanted to figure out what was going on with our star, so I talked with heliophysicist Erika Palmerio. Here’s what she said, edited for brevity.

I've seen some sensational headlines about the sun lately. What’s going on?

Let me say this first: Nothing sensational or mysterious is happening! The solar activity goes through a so-called 11-year cycle, which means that over the course of approximately 11 years, the sun will go from a solar minimum (very little activity) to a solar maximum (very high activity) to a solar minimum again. Our last solar minimum was around December 2019. This means that our next solar maximum should happen sometime around 2025, and the sun's activity is ramping up more and more until then.

So, in general, headlines that, for example, highlight that there have been one or two "scary" X-class flares are not wrong (apart from the "scary" part), but this is nothing to be surprised about because it's exactly what we expect the sun would be doing during the so-called “ascending” phase of the solar cycle — no apocalypse in sight!

Now, the particular event I think you are referring to is what has been called in the media a "solar polar vortex" — in scientific jargon, we call this a "polar crown filament."

Filaments (or prominences) are large suspended plasma structures that are much cooler and denser than the surrounding corona. They appear dark when seen against the solar disc (filaments), and bright when seen off the solar limb (prominence), but they are the same phenomenon. They lie along "filament channels," which are regions above "polarity inversion lines" that separate magnetic fields of opposite polarity (north and south, like on a magnet) on the surface of the sun.

Filaments come in many different sizes and flavors, but the most spectacular ones are without doubt the humongous quiet-sun filaments, which lie in regions of the sun that are characterized by weak magnetic fields (i.e., away from the strong-field active regions). Polar crown filaments are nothing other than quiet-sun filaments that have formed along the line that separates the magnetic field on one of the sun's poles from the nearest opposite-polarity field.

Huge filaments are absolutely spectacular to observe, especially as they are erupting (which happens if something disrupts their equilibrium), but both their eruption and their "vortex-like motion" are really common occurrences! And in the case of polar crown filaments, we usually don't even have to predict whether they will impact Earth, since they tend to move away from the sun either "straight up" or "straight down," away from us (we are facing more or less the sun's equator) — which is exactly what happened to the filament that made the recent headlines and that erupted on February 10.

What should the general public know about solar activity and what to watch out for?

In general, space weather mainly affects space-based assets (such as satellites) and astronauts, together with high-frequency communications on the ground. Most people are not affected by space weather in their daily lives in any significant way.

Now, of course, with a very strong storm, there is the potential to observe larger damages to (things like) power grids. This is why it is important to research and monitor the sun and its effects, but there is no reason to be worried at every single solar eruption. During solar maximum, we are actually impacted by even 40–50 CMEs (coronal mass ejections) in a single year, but most of them pass completely unnoticed to anyone but experts in the field, consumers that are more directly impacted (such as satellite operators), and aurora chasers.

If people want to track solar activity, how can they?

I think the homepage of NOAA's Space Weather Prediction Center provides a nice overview of the main things that are interesting to follow, in six panels. These include a view of the solar corona (where one can see CMEs moving away from the Sun as huge clouds), and the Kp index (a measure of how disturbed our near-Earth environment is. All green = nothing is happening!).

What are you interested in/excited about in your field right now?

I am of course very excited to see what the Solar Cycle 25 maximum brings! And this does not mean that I wish to see a huge storm: One can enjoy the rain without wishing to see a hurricane. But at the moment we have a few spacecraft that are traveling through space closer to the sun than Earth (including NASA's Parker Solar Probe), and one of my favorite aspects of my research is to quite literally "chase" CMEs from one probe to the next as they propagate away from the sun. The more solar eruptions there are, the more chances for some lucky lineups of spacecraft that can be used for some amazing science.

And finally, one thing that I always like to remind people of is that we should not be scared of "normal-size storms" from the sun. On the contrary, the more of these we get, the more we scientists can study them and refine our knowledge and models, so that we are really prepared if and when the "scary one" comes.

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