Solar wind signatures in the chromosphere

Coronal holes (CHs) are regions with reduced intensity and enhanced blueshifts when compared to Quiet Sun (QS) regions at coronal temperatures. However, such differences are seen in transition region temperatures only for regions with similar magnetic flux density (|B|). In this work, we study the chromospheric Mg II h&k, the C II doublet lines and transition region Si IV line in CHs and QS as a function of |B|. We find the intensities, velocities and the C II line widths to increase with increasing |B|. For both the chromospheric lines, we find reduced intensity, excess blueshifts as well as excess redshifts in CHs over QS for regions with similar |B|. Moreover, CHs show larger line width in CII than QS for regions with similar |B|. When synergy between the velocities of C II, Mg II and Si IV lines is investigated, we find: (a). Upflows, downflows in all the lines are tightly correlated. (b). Upflows in Mg II and C II have no correlation with downflows observed in Si IV. (c). Downflows of Mg II, C II are correlated with upflows of Si IV, with correlation values increasing from Mg II h2 to C II. These results may be explained if (a). Upflows in Mg II are accelerated till Si IV. (b), Downflows in Si IV are decelerated toward Mg II. (c). Bi-directional flows give rise to correlated transition region upflows and chromospheric downflows. Such bi-directional flows may occur due to impulsive events occurring between the formation height of Mg II/ C II and Si IV . The patterns of observed flows in CHs and QS may be explained by invoking impulsive heating in topologically different regions. These results provide evidence on the formation of solar wind in the chromosphere and further hints towards the unified heating scenario of the solar corona in the QS and CHs.