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Calculating the magnetic flux transfer across the open‐closed boundary (OCB) per unit time and distance—the reconnection electric field—is an important means of remotely monitoring magnetospheric dynamics. Ground‐based measurements of plasma convection velocities together with velocities of the OCB are commonly used to infer reconnection rates. However, this approach is limited by spatial coverage and often lacks robust uncertainty quantification. In this paper, we assimilate Super Dual Auroral Radar Network convection measurements, ground magnetometer data, and estimates of the conductance derived from the Imager for Magnetopause‐to‐Aurora Global Exploration satellite imagers, using the Local mapping of polar ionospheric electrodynamics (Lompe) framework over a region in North America. We present a new method to assess various contributions to uncertainties in the derived reconnection electric fields, including a novel approach to estimate uncertainties in conductance from global auroral imaging. Our method is demonstrated on a substorm event with an associated pseudobreakup during a period of favorable observational coverage. In this case study, the uncertainties in the reconnection electric field are ∼5–10 mV/m at the peak of substorm expansion, roughly 15% of the peak reconnection electric field. We find that the main contributor to the reconnection electric field estimates after substorm onset is the OCB motion, whereas during the pseudobreakup the main contributor is ionospheric plasma convection. Plain Language Summary: The solar wind is a stream of particles and magnetic field flowing away from the Sun. Under certain orientations of the solar wind magnetic field, magnetic reconnection can occur between the magnetic fields of the solar wind and Earth. Magnetic reconnection is the process by which oppositely directed magnetic field lines "break," then merge into a new configuration. Magnetic reconnection is the primary process responsible for coupling the solar wind energy to the Earth's magnetic field, and is ultimately the principal driver of space weather. In the Earth's magnetosphere, reconnection is associated with topological changes at both dayside and nightside, where stored magnetic energy is released through a global reconfiguration of the magnetosphere which is referred to as magnetospheric substorms. We can remotely monitor this reconnection from the ground by studying the transfer of magnetic flux across the boundary between open and closed magnetic field lines. In this study, we combined data from ground‐based radars, ground magnetometers, and space‐based auroral imaging to monitor the reconnection rate across the entire nightside auroral oval for a full substorm event. We additionally derived uncertainties in this reconnection rate stemming from uncertainties in the ionospheric velocities, the ionospheric conductances, and the open‐closed boundary motion. Key Points: We estimate Hall and Pedersen conductance uncertainties using global auroral satellite images from Imager for Magnetopause‐to‐Aurora Global Exploration (IMAGE) for an isolated substormWe calculate uncertainties in ionospheric reconnection electric fields related to conductance, open‐closed boundary (OCB) motion, and convectionWe find that the main contributor to the reconnection electric field estimates after onset is the OCB motion [ABSTRACT FROM AUTHOR]

Abstract The locations of region 1 and 2 field‐aligned current systems were determined using fluxgate magnetometer measurements from 875 dawn‐dusk passes of the Swarm A satellite. Within each field‐aligned current region, the ionospheric Pedersen conductance was derived from the newly corrected Swarm electric and magnetic field measurements. The Pedersen conductances are generally consistent with photoionization models. However, we show that the in situ method of determining Pedersen conductance allows for a more complete description of magnetosphere‐ionosphere coupling and should be used in future studies when possible. We show that, overall, the Pedersen conductance is larger in the upward current region than in the downward region by ∼0.6 S on the dawn side of the Earth. Meanwhile, the dusk side Pedersen conductance is equivalent in both current regions. We attribute this asymmetry to dawn side energetic electron precipitation, commonly associated with substorm electron injections from the magnetotail.

The locations of region 1 and 2 field‐aligned current systems were determined using fluxgate magnetometer measurements from 875 dawn‐dusk passes of the Swarm A satellite. Within each field‐aligned current region, the ionospheric Pedersen conductance was derived from the newly corrected Swarm electric and magnetic field measurements. The Pedersen conductances are generally consistent with photoionization models. However, we show that the in situ method of determining Pedersen conductance allows for a more complete description of magnetosphere‐ionosphere coupling and should be used in future studies when possible. We show that, overall, the Pedersen conductance is larger in the upward current region than in the downward region by ∼0.6 S on the dawn side of the Earth. Meanwhile, the dusk side Pedersen conductance is equivalent in both current regions. We attribute this asymmetry to dawn side energetic electron precipitation, commonly associated with substorm electron injections from the magnetotail. Key Points: In situ Pedersen conductance in field‐aligned current (FAC) regions are obtained from the Swarm measurements of the magnetic field and plasma flow velocityPedersen conductance is larger in the upward than downward FAC regions on the dawn side, the dusk side values are similar in both regionsAsymmetry between dawn and dusk current regions is attributed to intense electron precipitation commonly associated with substorm injections [ABSTRACT FROM AUTHOR]

Electromagnetic energy carried by magnetohydrodynamic modes is an important mechanism in the energy transfer between the magnetosphere and the ionosphere. Alfvén waves are known to carry field‐aligned currents and thus play an important role in the dynamics of the ionosphere‐magnetosphere coupling. The role of Hall conductance in this interplay has been explored in magnetohydrodynamic models of the ionosphere but has hitherto not been observed in situ. We use 5 years of observations from the Swarm mission to shed light on this interplay. We present a high‐latitude climatology of both the measured Poynting flux and the measured Alfvén wave reflection coefficient. Our results indicate that high‐energy precipitation, which penetrates deep into the ionosphere and directly leads to strongly enhanced Hall conductance, is an important cause of positively interfering Alfvén wave reflection. We present such observational evidence and, with that, suggest that Hall conductance is substantially more important in the ionospheric wave reflection climatology than hitherto believed. Key Points: Enhanced Hall conductance plays a major role in driving Alfvén wave reflection, especially on the nightside ionosphereHigh‐energy precipitation provided by the nightside aurora provides an explanation for the enhanced Hall conductancePedersen conductance and solar zenith angle are strong indicators for Alfvén wave reflection on the dayside ionosphere [ABSTRACT FROM AUTHOR]

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]

We show that a white‐light all‐sky imager can estimate Pedersen conductance with an uncertainty of 3 mho or 40%. Using a series of case studies over a wide range of geomagnetic activity, we compare estimates of Pedersen conductance from the backscatter spectrum of the Poker Flat Incoherent Scatter Radar with auroral intensities. We limit this comparison to an area bounding the radar measurements and within a limited area close to (but off) imager zenith. We confirm a linear relationship between conductance and the square root of auroral intensity predicted from a simple theoretical approximation. Hence, we extend a previous empirical result found for green‐line emissions to the case of white‐light off‐zenith emissions. The difference between the radar conductance and the best‐fit relationship has a mean of −0.76 ± 4.8 mho and a relative mean difference of 21% ± 78%. The uncertainties are reduced to −0.72 ± 3.3 mho and 0% ± 40% by averaging conductance over 10 min, which we attribute to the time that auroral features take to move across the imager field being greater than the 1‐min resolution of the radar data. Our results demonstrate and calibrate the use of Time History of Events and Macroscale Interactions during Substorms all‐sky imagers for estimating Pedersen conductance. This technique allows the extension of estimates of Pedersen conductance from Incoherent Scatter Radars to derive continental‐scale estimates on scales of ~1–10 min and ~100 km2. It thus complements estimates from low‐altitude satellites, satellite auroral imagers, and ground‐based magnetometers. Plain Language Summary: The Sun is a rotating magnetic plasma ball that releases energetic charged particles and magnetism in a "solar wind." Sometimes, this wind "shakes hands" with the Earth's magnetic field, allowing energy to be pumped into region near the Earth, stretching magnetic field lines like an elastic band. Much energy is released explosively in a "substorm" causing complex and brilliant auroral light displays about the size of a continent. This can be examined really well over several kilometers by radars on the ground. However, the radars cannot tell you what is happening for the whole substorm which is the size of a continent. It had been suggested that you can use a surface camera with a filter on it to estimate the part of the conductivity that tells us how much electric currents are heating the atmosphere. We asked whether the network of nonfiltered cameras stretching across North America could measure the conductivity as well as a radar can. We found they do half as well as the radar. This means we can use this camera network and its data archive to learn more about how much substorms heat up the atmosphere and how complicated and changeable this behavior is. Key Points: We use a white‐light all‐sky imager to estimate Pedersen conductance to within an uncertainty of 3 mho or 40%We relate Pedersen conductance to the optical intensity with a single parabolic relationship across a wide range of geomagnetic activityOur results enable the exploitation of white‐light camera networks to study continental‐scale phenomena such as substorms [ABSTRACT FROM AUTHOR]

Abstract: The conductivity of the ionosphere is extremely important in geophysical processes and plays a critical role in magnetosphere‐ionosphere‐thermosphere coupling. Understanding its nature is essential to understand the physics of ionospheric electrodynamics. Earth's magnetic field, which varies greatly in geological time scales, is among the main variables involved in ionospheric conductivity. The present field can be approximated by a magnetic dipole that accounts for ~80% of the magnetic field at the Earth's surface, plus multipolar components making up the remaining ~20%. During a polarity transition the field magnitude diminishes to about 10% of its normal value at the expense, most likely, of decreasing the dipolar component and becoming mostly multipolar in nature. The effects of geomagnetic field variations on the spatial structure of Hall and Pedersen conductances are analyzed in the present work considering some possible reversal scenarios. The spatial structure of both conductances changes significantly with sharp spatial gradients. The conductivity peak heights also change, moving to upper heights as expected for weaker field configurations. [ABSTRACT FROM AUTHOR]