= Solar flare
A <solar flare> is a rapid release of magnetic energy in the solar atmosphere, observed as enhanced radiation and often accompanied by <plasma> heating and particle acceleration. Emission spans many wavelengths, with different bands tracing different stages and particle populations. A <solar flare> and a <coronal mass ejection> can accompany the same eruption, but radiation enhancement and expulsion of magnetized material describe different phenomena.<Overview of Solar Flares by NASA>[Magnetic-energy release, plasma heating, acceleration and multiwavelength signatures]{ref}
A simple energy scale comes from the <magnetic energy density>, $B^2/(2\mu_0)$. A hypothetical region with $B=0.01\,\mathrm T$ and volume $10^{21}\,\mathrm m^3$ contains
$$
E_B=\frac{B^2V}{2\mu_0}\simeq4.0\times10^{22}\,\mathrm J.
$$
This is an illustrative field-energy budget, not a measured flare yield. Only the releasable part of the field energy can power an event; geometry and the final magnetic state matter.
Monitoring depends on the instrument. GOES X-ray sensors measure the Sun's irradiance in specified passbands, including $0.1$–$0.8\,\mathrm{nm}$. Their time series can locate the rise and peak of an event, while X-ray images locate emitting regions on the solar disc. NOAA's operational event end uses a prescribed fall from peak towards background, so a reported duration is partly a measurement convention.<GOES X-ray Flux by NOAA Space Weather Prediction Center>[Details and event definitions: passbands, one-minute sampling and halfway-to-background end criterion]{ref}
Soft X-rays commonly trace heated plasma, while hard X-ray signatures can track energetic electrons. Comparing their time profiles tests how rapidly released magnetic energy reaches particles and heat. A single bright image or peak flux cannot by itself provide the total energy released in every channel.<Overview of Solar Flares by NASA>[Time-profile comparison of soft X-rays, hard X-rays and gamma rays]{ref}
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