@Article{CruzSabaSchuWarn:2022:UpBiLi,
               author = "Cruz, Ivan Toucedo and Saba, Marcelo Magalh{\~a}es Fares and 
                         Schumann, Carina and Warner, Tom A.",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {University of the 
                         Witwatersrand} and {ZT Research}",
                title = "Upward Bipolar Lightning Flashes Originated From the Connection of 
                         Recoil Leaders With Intracloud Lightning",
              journal = "Geophysical Research Letters",
                 year = "2022",
               volume = "49",
               number = "22",
                pages = "1",
             keywords = "The present work shows high-speed videos of two upward flashes 
                         that started with positive upward leaders and, instead of being 
                         followed by negative subsequent return strokes, they were followed 
                         by positive subsequent return strokes. In both cases, after the 
                         positive leaders developed, recoil leaders (RL) appeared in their 
                         decayed branches as would be usual in negative upward lightning 
                         flashes. However, in these flashes the negative end of a recoil 
                         leader connected to a positive leader of an intracloud (IC) flash 
                         nearby. The connection initiated a downward positive leader that 
                         re-ionized the decayed channel of the upward flash all the way to 
                         the tower giving origin to a positive subsequent return stroke. 
                         This work shows that RL do play an important role in the 
                         occurrence of bipolar upward flashes and their interaction with IC 
                         flashes can provide explanations for all types of bipolar upward 
                         flashes initiated by upward positive leaders.Plain Language 
                         SummaryThe increasing number of tall buildings and towers, and the 
                         rapid expansion of wind power generation, has also increased the 
                         concerns about damages caused by upward flashes. Although upward 
                         flashes are not the most common type of flashes in nature, they 
                         can pose a serious threat to tall structures. They are usually 
                         initiated by a positive upward leader that starts at the tip of 
                         the structure. After reaching cloud base, the discharge ends or is 
                         followed by a negative downward leader that strikes the tower and 
                         produces an intense negative discharge known as a return stroke. 
                         This common type of upward flash is named negative upward flash. 
                         The present work presents high-speed videos of a rare type of 
                         upward flash, the bipolar upward flash. In this flash, after the 
                         propagation of the positive upward leader, another positive leader 
                         retraces the same path traveled by the original upward leader, but 
                         in a downward manner resulting in a positive return stroke. The 
                         increased threat of damage caused by this rare flash is due to the 
                         intense positive return stroke and long duration current that 
                         frequently follows. This work explains how this, and other types 
                         of bipolar flashes are possible.",
                  doi = "10.1029/2022GL101072",
                  url = "http://dx.doi.org/10.1029/2022GL101072",
                 issn = "0094-8276",
                label = "lattes: 2485050167650687 1 CruzSabaSchuWarn:2022:UpBiLi",
             language = "en",
           targetfile = "Geophysical Research Letters - 2022 - Cruz - Upward Bipolar 
                         Lightning Flashes Originated From the Connection of Recoil.pdf",
        urlaccessdate = "16 jun. 2024"
}