Solar flares are graded by letter — A, B, C, M, X — and every letter is ten times the one below. Drawn on an ordinary ruler, the Sun is one spike and an otherwise dead-flat line; you'd see the rare giant and nothing else. Drawn on the logarithmic staircase below, the whole Sun shows at once: the quiet X-ray hum down in the basement, the barks that climb a band, the M-flare that pokes a full step above the noise. The scale has a floor — the calm Sun never goes silent — and no roof: X has no successor letter, so the largest flares simply keep counting upward, and a Carrington-grade event runs clean off the top of this chart. Live soft-X-ray flux from NOAA's GOES watch, the past three days.
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the Sun right now — soft-X-ray class
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loudest flare in the last 7 days
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flares logged in the last 7 days
10,000×
A to X — four decades, and X has no top letter
Soft-X-ray flux (0.1–0.8 nm) on a logarithmic ladder · each band ten times the one below · three days replayedreplaying…
X-ray fluxflare peakbands: A · B · C · M · X — ×10 each
Read the ladder from the bottom. The faint trace never reaches the floor and never flattens — the quiet Sun still glows in soft X-rays, a basement hum that holds steady at A and B class. A flare is the trace climbing through a band line: cross into C and the X-ray output of the whole star has gone up tenfold; cross into M, a hundredfold; into X, ten thousand times the basement. Because every step is a power of ten, the bands sit evenly spaced on the screen while the physics between them is anything but even — the M-flare that looks "a little higher" than the hum is a hundred times the energy.
And the ladder has no top rung. After X there is no letter Y — the strongest flares are simply X10, X20, X45, counting on past the chart's edge into the arrow at the top. The Carrington event of 1859, the storm that set telegraph lines sparking, is reckoned around X45: it would draw forty-five times above the X line, off this page entirely. We are near the noisy peak of the eleven-year sunspot cycle, so the barks come often — count them in the figure above. Most are basement business. Every so often one crosses a band you can feel from ninety-three million miles away: a radio blackout on Earth's daylit side, minutes after the light arrives.
How this was built. One-minute soft-X-ray irradiance from the GOES X-Ray Sensor (long channel, 0.1–0.8 nm — the band that defines flare class), via NOAA SWPC's open JSON feed (no key, fetched in your browser, trailing three days), with the flare catalogue from the matching 7-day flare list. Class is read straight off the flux: a flare's letter is the power-of-ten band its peak long-channel irradiance falls in (B = 10⁻⁷, C = 10⁻⁶, M = 10⁻⁵, X = 10⁻⁴ W m⁻²), and the number is the multiplier within that band — flux 6.9×10⁻⁵ W m⁻² is M6.9. The vertical axis is log₁₀ of that flux, which is why ten-times steps land as equal heights. The Carrington estimate (~X45) is from peak-flux reconstructions of the 1859 storm; it is an estimate, not a GOES measurement — the satellite era has never seen one.
The PloverData: NOAA SWPC · GOES-18 X-Ray Sensor · Fetched in-browser · No build step · Source on request