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Pedersen conductivity is one of the main parameters in atmospheric electrodynamics, magnetosphere‐ionosphere‐thermosphere coupling, and several other geophysical processes. It is determined by the collision frequency between charged and neutral components and the Earth's magnetic field intensity through the gyrofrequency. This work analyzes the contribution of different ionic species to the variability of Pedersen conductance in time scales from hours to years within the period 1964–2008 based on the results of various atmospheric and ionospheric models. The main results are (1) there is a positive correlation between O+ density and Pedersen conductance, (2) Pedersen conductance of F layer has a larger increase with the solar activity than that of E layer, (3) Pedersen conductance has a long‐term trend that is determined by Earth's magnetic field intensity and electron density, and (4) at midlatitudes trends are mainly governed by the Earth's magnetic field and modulated by the electron density, while at high latitudes both are important. Key Points: Pedersen conductance calculation on different time scalesIonic contribution to Pedersen conductance considering days, months, and years [ABSTRACT FROM AUTHOR]

Changes in the Earth's magnetic field can deeply modify the polar caps and auroral zones, which are the regions of most frequent precipitation of energetic particles. The present field is characterized by a dominant dipole plus weaker multipolar components. The field varies greatly in time, with the most drastic changes being polarity reversals that take place on average every ∼200 000 yr. During a polarity transition the field magnitude may diminish to about 10 per cent of its value prior to the reversal due to a decreasing dipolar component and by becoming mostly multipolar in nature. Polar caps depend on the geomagnetic field configuration so changes in their morphology are expected as a consequence of the variation and reversal of this field. We model polar caps' location by considering a superposition of the internal geomagnetic field and a uniform external field and then following the open field lines to the Earth's surface. Polar caps' location and shape for different magnetic field reversal scenarios are analysed in this work. Two polar caps near the present dipole axis intersection with the Earth's surface prevail for a dipole decrease to a certain extent, below which the southern hemisphere polar cap moves to mid-latitudes. An axial dipole collapse gives a pair of polar caps both at mid-latitudes of the southern hemisphere, while in a dipole rotation scenario the polar caps reside at the equator. If reversals occur due to an energy cascade from the dipole to higher degrees, more than two polar caps may appear. In our energy cascade scenario, four polar caps at various latitudes of both hemispheres prevail. These results indicate that during reversals auroral zones may reach mid- and low-latitude regions, and the atmosphere may become more vulnerable to the direct effect of energetic particle precipitation. This vulnerability is particularly striking at the southern hemisphere where reversed flux patches appear on the core–mantle boundary and weak intensity characterizes the present field at the Earth's surface. [ABSTRACT FROM AUTHOR]

Ionospheric conductivity is a key parameter to understand the upper atmosphere electrodynamics, magnetosphere‐ionosphere‐thermosphere coupling and several geophysical processes. In the case of Pedersen conductivity, ions and electrons are moving in opposite direction, so that it results from the addition of the separate contributions. In this work, the role of the three main ions, that is, NO+, O2+, and O+, in the conductivity height profile and in the conductance global pattern is analyzed for different solar activity levels and seasons. NO+ is the is the main contributor for the maximum conductivity in all the cases in the E layer; however, O+ takes relevance with a significant percentage of the conductance at certain regions such as the South Atlantic Anomaly and the crests at the equatorial ionization anomaly, becoming the main conducting ion in these zones when the solar activity is high. Regarding seasonal effects, the role of NO+ in the conductivity is maximum on summer hemisphere, while O+ becomes important in winter and maximum with high solar activity. O2+ has maximum percentage close to magnetic poles, where the magnetic field strength is intense lowering the peak conducting level. Key Points: The relative contribution of each ion spicies to Pedersen conductance is variableAtomic oxygen is the main conducting ion near of magnetic field minimum and with high solar activityMolecular oxygen contribution to conductance is maximum near of geomagnetic poles [ABSTRACT FROM AUTHOR]