# ARRL

## tenthwave

 Joined: Wed, Dec 5th 2018, 16:38 Roles: N/A Moderates: N/A

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Exra Exam E3C09 anwer error? Jan 23rd 2020, 13:46 6 10,162 on 2/8/21

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Exra Exam E3C09 anwer error? tenthwave on 24/1/20
I kept reading. Wikimedia is clear and consistent with references. The letter classifications C,M,X are each 10x stronger than the previous letter classification. The letters are a quick way to express the exponent of the measure of total flux of X-rays in the 1 to 8 angstrom wavelength range in W/m^2 as seen by the GOES satellite. The X-class range begins at X1 or 1x10^-4 W/m^2 with the index 1 being the "significand" of the exponential notion. (I had to look that up) The X2 classification is then 2x10^-4 W/m^2. M3 is 3x10^-4 W/m^2, etc. The wiki even specifically answers E3C09 by saying that M3 is 50% stronger than M2. If the X subscript really indicated successive factors of 2 in power then the X28 flare of 2003 would have been 2^27 or 1.3x10^8 times more powerful than an M1 rather than a mere 28 times more powerful. Who keeps track of these errors?
Exra Exam E3C09 anwer error? tenthwave on 23/1/20
Hi All
I'm studying for the Amateur Extra exam. I'm throwing this forum question into "Propagation" to match the Extra exam classification.

Question E3C09 asks about the relative strength of an X3 solar flare compared to an X2 solar flare. The "official" answer seems to be that an X3 is TWICE as strong as an X2, suggesting that the subscript uses a logarithmic scale. A different answer for that question in the exam is that an X3 is 50% stronger than an X2, suggesting that (within the X-class) the subscript uses a linear scale. I think that the "wrong" answer is actually correct.

From what I read on a number of sites on the internet the correct answer should be that, within the X class, the subscripts are linear.
Normally the subscripts range from 1 to 9 except for the X class which can be extended.

The strongest X class flare to date is an X28 which is 28X as strong as an X1.

All of the practice sites say that an X3 is twice as strong as an X2.

Am I missing something here?... misreading the question?

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