Decoding Solar Flare Classifications

When a solar expert says that there are multiple M-Class solar flares being detected on the Sun, do you know what that means?   From today’s (5 July) posting on

Solar Update / High Solar Activity:
Solar activity is currently at high levels with multiple M-Class solar flares being detected around mostly large Sunspot 1515 in the southern hemisphere. This region retains its Beta-Gamma-Delta magnetic configuration and may produce an X-Class solar flare within the next 24-48 hours. Sunspot 1513 located in the northern hemisphere did generate an M1.8 event on Wednesday and was associated with a possible Earth directed CME. An impact is expected by July 7 the earliest. Minor geomagnetic activity will be possible.” 

This solar update reports M-Class flares are being detected and that an X-Class flare maybe produced in the next 24 to 48 hours.    Are these conditions a threat to Earth?

Knowing the classifications for Solar Flares  may serve you well. The classifications can be found in this website: The HandyMan’s Guide to Solar/Geomagnetic Conditions by Paul Harden, NA5N

Solar Flare Classification  

Flare Class

Type of Flare

HF Radio Effects

Resulting Geomagnetic Storm


Very Small









* Low Absorptons

* Active to Minor



* High absorption

* Minor to Major



* Possible Blackout

* Major to Severe*

*Conditions cited if Earth is in the trajectory of the flare emissions

Flare class is further rated from 1-9, ex. M1, M2, M3…M9

The larger the number, the larger the flare within that class. An X7-X9 is considered a “Grand Daddy” flare. Only a few have occurred over the past 30 years and cause total disruptions to communications, huge auroras, power grid failures, etc. Radio and X-Ray emissions from a flare affect the Earth for the duration of the solar event, usually 30 minutes or less. The Earth is 8 light-minutes from the Sun.

Conflicting Sunspot Classifications

I believe the Sunspot classification shown in  The HandyMan’s Guide to Solar/Geomagnetic Conditions by Paul Harden, NA5N groups the consequences reasonably well.  However,  the Sunspots classifications used in the Solar Update follow the Mount Wilson classification system which can be seen here.  It has a more detailed grouping system, including a gamma designation not included in the HandyMan’s Guide.




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