Solar surges related to UV bursts

Surges are cool and dense ejections typically observed in chromospheric lines closely related to other solar phenomena like UV bursts or coronal jets. Our aim is address the current lack of inverted models diagnostics surges as well characterizing their plasma properties. We have analyzed different with Interface Region Imaging Spectrograph (IRIS) on 2016 April. The mid- low-chromosphere examined by getting representative Mg II h&k line profiles through k-means algorithm performing inversions them using STiC code. studied far-UV spectra focusing O IV 1399.8 1401.2 \r{A} lines, carrying out density determine transition region properties these ejections. also used experiments performed Bifrost code for comparisons. Thanks k-means, we reduce number invert a factor 43.2. show that temperatures mainly around T $=6$ kK at $ -6.0 \le \log_{10}(\tau) -3.2$. For electronic density, $n_e$, line-of-sight velocity, $V_{\mathrm{LOS}}$, most reliable results from within -4.8$, $n_e$ ranging $\sim1.6 \times 10^{11}$ up $10^{12}$ cm$^{-3}$, $V_{\mathrm{LOS}}$ few km s$^{-1}$. find, first time, observational evidence enhanced emission surges, indicating considerable impact even weakest lines. emitting layers electron densities $2.5\times 10^{10}$ cm$^{-3}$. simulations provide theoretical support terms topology location surges.