Exploring Mutual Information between IRIS Spectral Lines. I. Correlations between Spectral Lines during Solar Flares and within the Quiet Sun.

Spectral lines allow us to probe the thermodynamics of solar atmosphere, but shape a single spectral line may be similar for different thermodynamic solutions. Multiline analyses are therefore crucial, computationally cumbersome. We investigate correlations between several chromospheric and transition region restrain solutions atmosphere during flares. used machine-learning methods capture statistical dependencies 6 sourced from 21 large flares observed by NASA's Interface Region Imaging Spectrograph (IRIS). The techniques based on an information-theoretic quantity called mutual information (MI), which captures both linear nonlinear lines. MI is estimated using categorical numeric method, performed separately collection quiet Sun flaring observations. Both approaches return consistent results, indicating weak under conditions, substantially enhanced with some line-pairs such as Mg II C having normalized score high 0.5. find that certain couple more readily than others, coherence in over many scale heights flares, all correlated GOES derivative, positive relationship correlation strength energy input. Our provide highly stable flexible framework quantifying physical quantities allowing obtain three-dimensional picture its state.