July 28th, AR 1532 M6-Class Flare

The above image was taken July 28th at 21:02 UTC by the Atmospheric Imaging Assembly (AIA), at 94 Angstroms, aboard the Solar Dynamics Observatory (SDO). The M6-class solar flare may be seen at the lower left. Image Credit: SDO/AIA

Well lookie there! The sun's Active Region 1532 (AR 1532) is at it, again. And just a day after its M2.7-class flare. On July 28th at about 21:02 UTC (5:02 PM EDT), AR 1532 erupted with a M6-class solar flare. We see above the view in extreme ultraviolet, from NASA's Solar Dynamics Observatory (SDO).

According to the peak flux scale, this flare was considered moderately strong. And as of yet, forecasters cannot confirm whether the flare produced a coronal mass ejection (CME). But even so, Earth would receive a glancing blow, but no more. That might change as that region continues to turn toward Earth.

Since we are talking about flares and CMEs and their potential implications, let's take this opportunity to review our primers on solar flares and CMEs.

Solar Flare Primer

A solar flare is an explosion on the sun that occurs when the energy stored in twisted magnetic fields (usually above sunspots) is suddenly released. Flares produce a burst of radiation across the electromagnetic spectrum, from radio waves to X-rays and gamma-rays.

Solar flares are classified, from lowest to highest, as A, B, C, M and X according to the peak flux (in watts per square meter, W/m^2) of 100 to 800 picometer X-rays near Earth, as measured on the GOES spacecraft. The five categories break down as follows.

A-class: Peak flux of less than 10^-7 Watts/square meter. A-class flares produce no noticeable consequences on Earth.

B-class: Peak flux ranges from 10^-7 to 10^-6 Watts/square meter. B-class flares produce no noticeable consequences on Earth.

C-class: Peak flux ranges from 10^-6 to 10^-5 Watts/square meter. C-class flares produce few noticeable consequences
on Earth.

M-class: Peak flux ranges from 10^-5 to 10^-4 Watts/square meter. M-class flares  can cause brief radio blackouts that affect Earth's polar regions. Minor radiation storms sometimes follow an M-class flare.

X-class: Peak flux is greater than 10^-4 Watts/square meter. X-class flare are major events that can trigger planet-wide radio blackouts and long-lasting radiation storms.

Within each category are nine subdivisions of strength. For example, C1 to C9, M1 to M9, and so on. On July 14, 2000, the sun produced a X6 flare which triggered a major radiation storm around Earth and was nicknamed the Bastille Day event.

Coronal Mass Ejection Primer

A coronal mass ejection (CME) is a massive burst of solar wind, plasma, and magnetic fields rising above the solar corona or being released into space.

CMEs are often associated with other forms of solar activity, most notably solar flares, but a causal relationship between the two has not been established. Most CMEs originate from active regions on Sun's surface, such as groupings of sunspots associated with frequent flares. Near a solar maximum — the period of greatest activity in a solar cycle — the sun produces about three CMEs every day, whereas near a solar minimum — the period of least activity in a solar cycle — there is about one CME every five days.

Wrapping Up

With what have seen so far from AR 1532, things are sure to get interesting in the coming days. Stay tuned...

To monitor solar flare activity minute by minute, visit the "Today's Space Weather" page of NOAA's Space Weather Prediction Center, URL: www.swpc.noaa.gov .

To learn more about the sun and to stay current on solar activity, visit the mission home pages of the Solar Dynamics Observatory (SDO), sdo.gsfc.nasa.gov and the Solar and Heliospheric Observatory (SOHO), sohowww.nascom.nasa.gov .

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