Anomalous night-time peaks in diurnal variations of NmF2 close to the geomagnetic equator: A statistical study |
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| Institution: | 1. School of Mathematics and Physics, North China Electric Power University, Baoding 071003, China;2. Sate Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100190, China;3. Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;1. Department of EEE, Hacettepe University, Beytepe, Ankara 06800, Turkey;2. IZMIRAN, Moscow, 142190 Troitsk, Russia;1. High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO, United States;2. Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China;3. College of Earth Sciences, University of the Chinese Academy of Sciences, Beijing, China;1. Geodynamics Research Laboratory, University of Warmia and Mazury, 1 Oczapowskiego st., 10-719 Olsztyn, Poland;2. West Department of IZMIRAN, 41 Pobeda Av., 236010 Kaliningrad, Russia;1. Institute of Geophysics, University of Tehran, Iran;2. University of New Brunswick, Canada;1. Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China;2. Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing 100029, China;3. University of Chinese Academy of Sciences, Beijing, China;4. State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing, China |
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| Abstract: | We present a study of anomalous night-time NmF2 peaks, ANNPs, observed by the La Paz, Natal, Djibouti, Kodaikanal, Madras, Manila, Talara, and Huancayo–Jicamarca ionosonde stations close to the geomagnetic equator. It is shown for the first time that the probabilities of occurrence of the first and second ANNPs depend on the geomagnetic longitude, and there is a longitude sector close to 110° geomagnetic longitude where the first and second ANNPs occur less frequently in comparison with the longitude regions located close to and below about 34° geomagnetic longitude and close to and above about 144° geomagnetic longitude. The found frequencies of occurrence of the ANNPs increase with increasing solar activity, except of the Djibouti and Kodaikanal ionosonde stations, where the probability of the first ANNP occurrence is found to decrease with increasing solar activity from low to moderate solar activity, and except of the Natal ionosonde station, where the frequencies of occurrence of the first and second ANNPs decrease with increasing solar activity from moderate to high solar activity. We found that the occurrence probabilities of ANNPs during geomagnetically disturbed conditions are greater than those during geomagnetically quiet conditions. The ANNP probabilities are largest in summer and are lowest in winter for the La-Paz, Talara, and Huancayo–Jicamarca sounders. These probabilities are lowest in summer for the Djibouti, Madras, and Manila ionosonde stations, and in spring for the Kodaikanal sounder. The maximums in the probabilities are found to be in autumn for the Djibouti, Madras, and Manila ionosonde stations, and in winter for the Kodaikanal sounder. |
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