An X-1.1 class solar flare erupted from the Sun on Sunday, March 4 at 11:13 PM EST (0413 UTC March 5), sending an explosion of plasma and charged particles -- a coronal mass ejection (CME) -- hurtling through space. Forecasters at NOAA’s Space Weather Prediction Center (SWPC) are saying that the CME should miss Earth, but will hit Mercury and Venus.

Even if this CME misses, high-latitude sky watchers should still be alert for auroras in the nights ahead. An M3-class eruption from the same sunspot just a day before produced another, wider CME that might intersect Earth. The cloud is expected to deliver a glancing blow to Earth’s magnetic field on March 6 around 0430 UTC. Sunday night’s solar flare is only the second X-class eruption so far this year. X-class flares are the most powerful type of solar storm; M-class eruptions are considered midrange and C-class flares are the weakest.

According to Spaceweather.com, SWPC forecasters are estimating a 75 percent chance of M-class solar flares and a 30 percent chance of an X-flare from big sunspot 1429, which emerged on the Sun on March 2 and is estimated to be at least four to five times larger than Earth. The active region is slowly turning to face Earth, so if any such eruptions do occur, they are increasingly likely to be geoeffective. Forecasters say there is a 30-40 percent chance of polar geomagnetic storms through the rest of the week. The 1429 sunspot region continues to be quite active since it emerged on March 2, and scientists are predicting it will spew more flares as the week goes on.

When a CME hits the Earth’s atmosphere -- approximately 72 hours after exploding on the Sun -- the low bands will be depressed and signals will be weaker the lower the frequency. The absorption rate will be most severe on 160 meters, less on 80 and somewhat better on 40 meters. The maximum usable frequency (MUF) -- the highest frequency by which a radio wave can propagate between given terminals by ionospheric propagation alone, independent of power -- will be lower and auroral propagation on the VHF bands is quite possible.

When aurora occur, the electrons hit the ionosphere at the North and South geomagnetic poles, creating ionization. Waves that would normally travel off into space are bouncing off the aurora and being redirected back toward Earth. This can create opportunities for long-distance propagation via VHF and UHF.

VHF operators greet CMEs as a welcome opportunity for unusual, enhanced propagation. “CMEs can trigger the Aurora Borealis,” explained ARRL Contest Branch Manager and VHF aficionado Sean Kutzko, KX9X. “If the aurora is intense enough, you can use it as a ‘wall’ to bounce signals off of on 6 and 2 meters -- and sometimes higher. If you have a beam on the VHF bands, point it north (or south, if you’re in the Southern Hemisphere) and listen for strange-sounding signals.”

Kutzko noted that aurora can cause audio signals to become very distorted: “On 6 meters, SSB signals become quite difficult to understand, and on 2 meters, it renders sideband practically unusable. CW is the preferred mode of communication during an aurora opening. Even so, the pure tone of a CW signal becomes distorted as well, reducing the pure ‘beep’ tone to a whisper-like ‘pffft.’”

In 2013, solar activity levels are expected to peak with the next solar maximum within the 11-year solar activity cycle. “We now know how powerful space weather can be and how events that begin on the surface of the Sun can end up wreaking havoc here on Earth,” said SWPC Director Tom Bogdan. “This is why NOAA has a Space Weather Prediction Center -- to forecast when space weather is coming our way, so we can avoid or mitigate damages. We’re coming up to the next solar maximum, so we expect to see more of these storms coming from the Sun over the next three to five years.”

Click here for an in-depth look at sunspots, solar flares and coronal mass ejections.