The Sun speaks up

By Phil Plait | July 7, 2012 6:31 am

It’s been a while since we’ve had a big flare from the Sun. Active region 1515 was looking like it might do the trick — over the past week this group of sunspots has been hissing and spitting, but the flares have been relative small. Astronomers rate flares by their X-ray energy: A, B, C, M, and X, where X is the highest. Some of the flares from AR1515 were C class and some M class – moderately strong.

Between July 5 and 6 it put out about a dozen of those smaller flares:

Then, late on July 6, it blew out the first X-class flare of the summer:

This sequence of images from the Solar Dynamics Observatory shows the flare over a bunch of different ultraviolet wavelengths, where flares are most obvious. You can see that it was pretty bright! Here’s a video showing it erupting:

The video again shows the Sun at different wavelengths of UV light. The flickering is due to the software automatically setting the brightness level; when the flare gets bright it sets the image to be dimmer, so the Sun appears to flicker. The long dashed-line spikes are not real; those are due to the way the detector in SDO sees X-ray light, like the spikes you see in bright stars in some telescopic images.

Flares occur when the Sun’s magnetic field gets tangled up. In a sense, the field short-circuits, releasing vasts of built-up energy, and we call that a flare. A big one can release 10% of the entire energy of the Sun! This can emit high-energy light and a huge blast of subatomic particles which cross the inner solar system and slam into us. While we’re safe on the ground, this can damage satellites, cause blackouts, and of course trigger gorgeous aurorae — the northern and southern lights.

This flare was still pretty small even for an X class; we had bigger ones over the past year (see the Related Posts for links to some of those). This particular group of sunspots is heading over the edge of the Sun now as our star rotates, so we probably won’t be seeing it again; sunspots tend not to last that long. But there will be more. We’re still approaching the peak of the sunspot cycle, probably late next year, so expect plenty more — and more powerful — flares to come.

Tip o’ the welder’s goggles to Camilla Corona SDO on Google+. Image credit: NASA/SDO

Related Posts:
HD Footage of last night’s flare
The Sun lets out a brief flare
The Sun aims a storm right at Earth: expect aurorae tonight!
GORGEOUS solar eruption!
The birth of a sunspot cluster

MORE ABOUT: SDO, solar flare, Sun

Comments (8)

  1. jearley

    Not so fast, Phil. I was at a talk two weeks ago at the NOAO where data was presented showing that the max for Cycle 24 may have already passed. That is a prediction, but it was backed up with some good evidence from past cycles. I’ll have to look at my notes to find the details.
    In any event, thanks to the SDO team and you for putting this up.

  2. AliCali

    I heard the solar maximum is the end of this year…maybe December, 2012???

  3. Nathan


    Spotless Days
    Current Stretch: 0 days
    2012 total: 0 days (0%)
    2011 total: 2 days (<1%)
    2010 total: 51 days (14%)
    2009 total: 260 days (71%)

    Considering an average 11 years for a solar cycle, with actual length being anywhere from 9 – 14 years and that this maximum got spun up in 2010 (mid~) then that could put maximum peak anywhere in the neighborhood of 2013-2015 depending on specific cycle length.

    If max/min is tracked by flare strength though, I could see an argument made that we're on the tail end, but remember the previous minimum appeared to have lasted a bit longer than normal so predictions may be off a bit at this point.

    The NOAO predictions appear to be off at this point. Marshal Space Flight has updated their prediction notes as of 7/2/2012:

    “The current prediction for Sunspot Cycle 24 gives a smoothed sunspot number maximum of about 60 in the Spring of 2013. We are currently over three years into Cycle 24. The current predicted size makes this the smallest sunspot cycle in about 100 years.” (quoted 7/7/2012)

  4. John

    “Then, late on July 6, it blew out the first X-class flare of the summer”

    Which summer is that? Is it summer on the Sun??

  5. MadScientist

    That’s awesome – it’s so bright that the image is telling us a bit about how the mirror is supported.

  6. Wow, that’s pretty neat. But since it’s so hot today and I have the a/c on, I hope the flares don’t cause my house to lose the electr

  7. Marina Stern

    Please let there be aurorae in Northern Oregon! It has been overcast every time there has been sunspot activity since I moved here. Clear tonight; fingers crossed.

  8. David Krauss

    “A big one can release 10% of the entire energy of the Sun!”

    Do you mean make the sun 10% brighter as seen from Earth, or increase the total power output by 10%?

    Releasing 10% of its potential energy all at once would be a bad day.


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