<p class="1" style="text-indent: 0mm;"><b><span lang="EN-GB">Introduction: </span></b><span lang="EN-GB">Chondrules are sub mm-sized spherical objects in chondritic meteorites. They are thought to be formed by some heating events in an early stage of the Solar System. The chondrule formation mechanism has been debated but not yet identified.<o:p></o:p></span></p><p class="1" style="text-indent: 13.5pt;"><span lang="EN-GB">Formation processes of chondrules have been studied by various measurements and experiments on chondrules. It is considered that the temperature of a dust particle rises suddenly up to about 1800 K and the particle melts. Then the temperature decreases with a rate of the order of 1 - 100 K/h until the dust solidifies and forms a chondrule (e.g., Desch <i>et al.</i> 2012). Though the dust particle experiences a high temperature state, a significant amount of volatile elements are preserved in chondrules, which suggests that chondrules are formed in a dusty environment (Alexander <i>et al</i>. 2008).<o:p></o:p></span></p><p class="1" style="text-indent: 13.5pt;"><span lang="EN-GB">Based on information above, we explore a chondrule formation scenario based on a lightning hypothesis.<o:p></o:p></span></p><p class="1" style="text-indent: 0mm;"><b><span lang="EN-US">Generation of Lightning:</span></b><span lang="EN-US"> We model motions of dust particles in a planetesimal formation regions, collisions among them which leads to an electrification, a flow of charged particles which derives a charge separation and an electric field. If the field is strong enough, a lightning takes place.<o:p></o:p></span></p><p class="1" style="text-indent: 0mm;"><b><span lang="EN-US">Cooling Rate:</span></b><span lang="EN-US"> We numerically simulated the thermal evolution of a cylindrical region which is heated by a lightning. We found that cooling rates of dust particles there are consistent with preferred values (</span><span lang="EN-GB">Kaneko <i>et al</i>. 2023</span><span lang="EN-US">).<o:p></o:p></span></p><p class="1" style="text-indent: 0mm;"><b><span lang="EN-US">Preservation of Volatiles:</span></b><span lang="EN-US"> We numerically simulated the diffusion and estimated he size of chondrule formation region, and found that it is 1 km across or larger. The obtained size is 2 or 3 orders of magnitude smaller than a previous estimation (</span><span lang="EN-GB">Cuzzi & Alexander 2006</span><span lang="EN-US">).<o:p></o:p></span></p><p class="1" style="text-indent: 0mm;"><b><span lang="EN-US">Summary:</span></b><span lang="EN-US"> Chondrule formation by lightning associated with planetesimal formation seems to be a possible scenario, which is worth studying further.<o:p></o:p></span></p>