Studies of ionospheric F-region irregularities from geomagnetic mid-latitude conjugate regions |
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| Affiliation: | 1. Deep Space Exploration Laboratory, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China;2. CAS Center for Excellence in Comparative Planetology, Hefei 230026, China;1. School of Civil, Environmental and Mining Engineering, University of Adelaide, North Terrace Campus, SA 5005, Australia;2. Research Institute for Knowledge Systems, P.O. Box 463, 6211 NC Maastricht, Netherlands;1. Department of Physics, University of Lagos, Lagos, Nigeria;2. Department of Physics, University of Tasmania, Hobart, Australia;3. Department of Physics, Landmark University, Omu-Aran, Nigeria;4. Department of Physical Sciences, Bells University of Technology, Ota, Nigeria;1. Istituto Nazionale di Geofisica e Vulcanologia, Roma, Italy;2. G. D''Annunzio University, Chieti, Italy;3. Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Athens, Greece;4. Centre National d''Etudes Spatiales, Paris, France;1. Research Institute of Physics, Southern Federal University, Rostov-on-Don, 344090, Russia;2. Fedorov Institute of Applied Geophysics, Moscow, 129128, Russia |
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| Abstract: | Scintillation data from near Boston, U.S.A., and spread-F data from Argentine Islands, Antarctica are used to investigate the diurnal and seasonal variations of the simultaneous occurrence of medium-scale (~ 1–10 km) irregularities in the electron concentration in the F-region of the ionosphere at conjugate magnetic mid-latitude regions. It is found that these two stations near 52° CGL observe similar irregularity occurrence on ~75% of occasions at night when the data are considered on an hour by hour basis. During solstices, the relationship is dominated by occasions when irregularities are absent from both ends of the geomagnetic field lines; however, at equinoxes, periods of the simultaneous occurrence and non-occurrence of irregularities are approximately equally frequent. During periods of high geomagnetic activity, processes associated with the convection electric field and particle precipitation are likely to be important for the formation and transport of irregularities over these higher mid-latitude observatories. These processes are likely to occur simultaneously in conjugate regions. On days following geomagnetic activity, two processes may be operating that enhance the probability of the temperature-gradient instability, and hence lead to the formation of irregularities. These are the presence of stable auroral red arcs which occur simultaneously in conjugate locations, and the negative F-region storm effects whereby latitudinal plasma concentration gradients are increased; these effects are only similar in conjugate regions. During very quiet geomagnetic periods, F-region irregularities are occasionally observed, but seldom simultaneously at the two ends of the field lines. There is also an anomalous peak in the occurrence of irregularities over Argentine Islands associated with local sunrise in winter. No explanation is offered for these observations. Photo-electrons from the conjugate hemisphere appear to have no effect on irregularity occurrence. |
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