European Incoherent Scatter Radar Research Articles

On the Factors Controlling the Relationship Between Type of Pulsating Aurora and Energy of Pulsating Auroral Electrons: Simultaneous Observations by Arase Satellite, Ground‐Based All‐Sky Imagers and EISCAT Radar

AbstractPulsating Aurora (PsA) is one of the major classes of diffuse aurora associated with precipitation of a few to a few tens of keV electrons from the magnetosphere. Recent studies suggested that, during PsA, more energetic (i.e., sub‐relativistic/relativistic) electrons precipitate into the ionosphere at the same time. Those electrons are considered to be scattered at the higher latitude part of the magnetosphere by whistler‐mode chorus waves propagating away from the magnetic equator. However, there have been no actual cases of simultaneous observations of precipitating electrons causing PsA (PsA electrons) and chorus waves propagating toward higher latitudes; thus, we still do not quite well understand under what conditions PsA electrons become harder and precipitate to lower altitudes. To address this question, we have investigated an extended interval of PsA on 12 January 2021, during which simultaneous observations with the Arase satellite, ground‐based all‐sky imagers and the European Incoherent SCATter (EISCAT) radar were conducted. We found that, when the PsA shape became patchy, the PsA electron energy increased and Arase detected intense chorus waves at magnetic latitudes above 20°, indicating the propagation of chorus waves up to higher latitudes along the field line. A direct comparison between the irregularities of the magnetospheric electron density and the emission intensity of PsA patches at the footprint of the satellite suggests that the PsA morphology and the energy of PsA electrons are determined by the presence of “magnetospheric density ducts,” which allow chorus waves to travel to higher latitudes and thereby precipitate more energetic electrons.

Response Time of Joule Heating Rate and Nitric Oxide Cooling Emission During Geomagnetic Storms: Correlated Ground‐Based and Satellite Observations

AbstractJoule heating is the primary source of the high latitude thermospheric energy dissipation during geomagnetic storm period. The nitric oxide (NO) emission at 5.3 μm accounts for the majority of Joule heating energy due to its radiative nature. It is the dominating cooling agent above 100 km that effectively regulates the thermospheric temperature. We studied the relationship between the response time of NO cooling emission and Joule heating rate during geomagnetic storm periods by using the NO emission observations by Sounding of Atmosphere using Broadband Emission Radiometry (SABER) onboard NASA’s Thermosphere‐Ionosphere‐Mesosphere Energetics and Dynamics (TIMED) satellite and the Joule heating rate measured by the European incoherent scatter (EISCAT) radar over Tromsø (geographic:69.59°N, 19.22°E), Norway, and the thermosphere‐ionosphere‐electrodynamics general circulation model (TIEGCM) simulation. We selected seven geomagnetic storms during which there were continuous measurements of the Pederson conductivity and electric fields when the TIMED/SABER satellite was in the northview mode. The TIEGCM gives a fair description of NO cooling. However, it was found that the Joule heating rates obtained with the TIEGCM often do not show good agreement with those from EISCAT observations. The Joule heating rate peaks with 3–7 hr of storm' onset. The NO cooling flux takes longer time to respond to the energy input during storm period. The fastest response of the NO cooling emission to the Joule heating rate is found during the strongest storm. The weakest storm does not have the longest response time. No correlation between the response time of NO cooling flux with respect to the Joule heating rate and storm’s intensity was observed.

The Influence of Field-Aligned Currents on Electron Density in the Ionosphere: Combined Observations of SWARM Satellites and ESR Radar

The results are presented of combined measurements by the SWARM spacecraft (SC) and European incoherent scatter radar on Svalbard for two events of simultaneous observations: in the nighttime ionosphere during substorm activation on January 9, 2014, and in the daytime ionosphere under quiet conditions on February 5, 2017. Onboard magnetometers of the SWARM SC provide measurements of field-aligned current density over the ionosphere. The radar, which is under the flyby trajectory at this time, measures the vertical distribution of the electron density (Ne). Experiments have shown that, under disturbed nighttime conditions, at the location of the field-aligned current flowing from the ionosphere, the plasma density increases throughout the entire slab of the ionosphere and the change in Ne is in agreement with theoretical estimates. In the daytime quiet ionosphere, Ne increases only in the F layer, but practically does not change in the E layer. The differences may be due to the fact that, in the first case, the carriers of the upward directed current are represented by the entire energy spectrum of auroral electrons of 1–10 keV, and in the second case only by the low-energy part.

A Ground‐Based Instrument Suite for Integrated High‐Time Resolution Measurements of Pulsating Aurora With Arase

AbstractA specialized ground‐based system has been developed for simultaneous observations of pulsating aurora (PsA) and related magnetospheric phenomena with the Arase satellite. The instrument suite is composed of (a) six 100 Hz sampling high‐speed all‐sky imagers (ASIs), (b) two 10 Hz sampling monochromatic ASIs observing 427.8 and 844.6 nm auroral emissions, (c) a 20 Hz sampling fluxgate magnetometer. The 100 Hz ASIs were deployed in four stations in Scandinavia and two stations in Alaska, which have been used for capturing the main pulsations and quasi 3 Hz internal modulations of PsA at the same time. The 10 Hz sampling monochromatic ASIs have been operative in Tromsø, Norway with the 20 Hz sampling magnetometer. Combination of these multiple instruments with the European Incoherent SCATter (EISCAT) radar enables us to detect the low‐altitude ionization due to energetic electron precipitation during PsA and further to reveal the ionospheric electrodynamics behind PsA. Since the launch of the Arase satellite, the data from these instruments have been examined in comparison with the wave and particle data from the satellite in the magnetosphere. In the future, the system can be utilized not only for studies of PsA but also for other classes of aurora in close collaboration with the planned EISCAT_3D project.

A Stimulated Emission Diagnostic Technique for Electron Temperature of the High Power Radio Wave Modified Ionosphere

AbstractWe report observations of stimulated electromagnetic emission (SEE) induced by high power high frequency (HF) radio waves near the third electron gyroharmonic (3) at European Incoherent Scatter Radar (EISCAT). It is discovered that stimulated Brillouin scattering (SBS) spectrum behaves similarly as spectral ion lines of the incoherent scatter radar (ISR) for HF pumping frequency above 3. The SBS spectral width shows correlation with electron to ion temperature ratio Te/Ti. A new inversion method is proposed by incorporating the SBS spectral width within an artificial neural network approach to achieve electron temperature inversion for ionospheric turbulent plasmas. This work provides a potential new technique to diagnose parameters in the modified ionosphere when the ISR is not available.

Statistical Study of Electron Density Enhancements in the Ionospheric F Region Associated With Pulsating Auroras

AbstractPulsating auroras (PsAs) are considered to be caused by energetic (>a few keV) electron precipitation. Additionally, soft electron precipitation (<a few keV) has often been observed in PsAs. This soft electron precipitation enhances the electron density in the ionospheric F region. However, to date, the relationship between PsAs and soft electron precipitation has not been well understood. In this study, using the data taken by the European incoherent scatter radar and the auroral all‐sky imager at Tromsø, we conducted two case studies to investigate, in detail, the relationship between the electron density height profile and the type of aurora. Additionally, we conducted statistical studies for 14 events to elucidate how often F region electron density enhancement occurs with a PsA. We consequently found that 76% of electron density height profiles showed a local peak in the F region, with electron temperature enhancements. It was also found that 89% of the F region peak altitudes were above the peak altitude of the ionization rate produced by electrons of characteristic energy below 100 eV. The occurrence rate of these profiles in the hourly magnetic local time (MLT) exceeded 80% in the 22–3 MLT sectors. We suggest that the electron density enhancement in the F region would have been caused by electrostatic electron cyclotron harmonic waves in the magnetosphere. Another candidate would have been polar patches that had traveled from the dayside ionosphere.

Penetration of MeV electrons into the mesosphere accompanying pulsating aurorae

Pulsating aurorae (PsA) are caused by the intermittent precipitations of magnetospheric electrons (energies of a few keV to a few tens of keV) through wave-particle interactions, thereby depositing most of their energy at altitudes ~ 100 km. However, the maximum energy of precipitated electrons and its impacts on the atmosphere are unknown. Herein, we report unique observations by the European Incoherent Scatter (EISCAT) radar showing electron precipitations ranging from a few hundred keV to a few MeV during a PsA associated with a weak geomagnetic storm. Simultaneously, the Arase spacecraft has observed intense whistler-mode chorus waves at the conjugate location along magnetic field lines. A computer simulation based on the EISCAT observations shows immediate catalytic ozone depletion at the mesospheric altitudes. Since PsA occurs frequently, often in daily basis, and extends its impact over large MLT areas, we anticipate that the PsA possesses a significant forcing to the mesospheric ozone chemistry in high latitudes through high energy electron precipitations. Therefore, the generation of PsA results in the depletion of mesospheric ozone through high-energy electron precipitations caused by whistler-mode chorus waves, which are similar to the well-known effect due to solar energetic protons triggered by solar flares.

Low‐Altitude Ion Upflow Observed by EISCAT and its Effects on Supply of Molecular Ions in the Ring Current Detected by Arase (ERG)

AbstractDuring the magnetic storm starting on September 7, 2017, the MEP‐i instrument onboard the Arase (ERG) satellite observed molecular ions (O2+/NO+/N2+) in the ring current. The molecular ions were observed by Arase in four orbits during this magnetic storm. This indicates that there was a continuous molecular ion supply from the ionosphere. During the storm main phase around the second Dst minimum (∼−100 nT) on September 8, 2017, the European Incoherent Scatter (EISCAT) radar observed the ion upflow (∼50–150 m s−1) in the low‐altitude (250–350 km) ionosphere together with strong ion heating up to >2,000 K. The convective electric field derived from the electron heating observed by EISCAT at an altitude of approximately 110 km was also enhanced by a factor of 2. The observations suggest that the additional ion heating at low altitudes helps to cause the fast upflow and transport molecular ions upward. The flux decreases from 280 to 350 km altitudes due to the dissociative recombination was estimated to be approximately two orders of magnitude. This resulted in significant molecular ion flux remaining at 350 km altitude. These results suggest that the low‐altitude ion upflow caused by the ion frictional heating enables molecular ions to escape to space against rapid loss by the dissociative recombination.

What Do the New 2018 HIWIND Thermospheric Wind Observations Tell Us About High‐Latitude Ion‐Neutral Coupling During Daytime?

AbstractDaytime thermospheric winds observed by the balloon‐borne instrument HIWIND (High‐altitude Interferometer WIND experiment) during two flights in June 2011 and 2018 from Kiruna (68°N, 20°E), along with simultaneous European Incoherent SCATter radar ion drift data, are analyzed. National Center for Atmospheric Research TIEGCM (Thermosphere Ionosphere Electrodynamics General Circulation Model) simulations for both flights are compared with observations. The observed thermospheric winds from the two flights have many similarities. HIWIND‐observed thermospheric winds tend to be equatorward during the morning hours before noon and close to zero in the afternoon. In contrast, TIEGCM predicts poleward winds before noon and near zero in the afternoon. Southward interplanetary magnetic field Bz, occurring as the balloon passed through morning, was associated with greater equatorward meridional winds. The TIEGCM‐simulated zonal winds have large differences with observations under more active conditions. The second HIWIND flight confirms some important results from the first flight and further shows thermospheric wind variations under different interplanetary magnetic field conditions. HIWIND observations in general provide invaluable data for model validation and highlight deficiencies in current high‐latitude simulations.

Polarization Electric Field Inside Auroral Patches: Simultaneous Experiment of EISCAT Radars and KAIRA

AbstractThe primary focus of this study was the motion of auroral patches and the polarization electric field generated therein observed on 9 November 2015 in an experiment using the European incoherent scatter (EISCAT) radars, Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA), and an all‐sky imager simultaneously. Based on the all‐sky imager data, the drift speed of the auroral patches corresponded to a southward electric field of 14.1( ± 3.7)–17.2( ± 4.5) mV/m. The convective electric field derived from the EISCAT radars and KAIRA observation was approximately 14.6 mV/m in the southward direction. This suggest that the spatial distribution of the auroral patches reflects the distribution of the cold plasma in the magnetosphere. The electron density and the height‐integrated Hall conductance between 80 and 120 km were enhanced by a factor of 2–4 inside the auroral patches. In this situation, a polarization electric field was generated therein. Enhanced ion velocities due to the polarization electric field was observed at up to 200‐km altitude; however, the absolute values of the ion velocities were approximately 40% of what was expected from the polarization electric field. A field‐aligned current (FAC) from 5 to 10 μA/m−2 in the edges of the auroral patches could explain the weakening of the polarization electric field. Since a FAC of that order of magnitude corresponded with that observed by the Swarm satellite, it was suggested that the polarization electric field was weakened by the FAC. Furthermore, the polarization electric field propagated upward from the dynamo region to at least 200 km.

Characteristics of CME‐ and CIR‐Driven Ion Upflows in the Polar Ionosphere

AbstractWe investigated how velocity and flux of ionospheric ion upflows vary during magnetic storms driven by corotating interaction regions (CIRs) and coronal mass ejections (CMEs), using data from the European Incoherent Scatter (EISCAT) Tromsø UHF and Svalbard radars between 1996 and 2015. The characteristics of ion upflows were compared with ion and electron temperature variations measured with the EISCAT radars and also joule heating rate, electric field, and field‐aligned current distribution derived from the Weimer model. Upward ion velocity increases in the nighttime at Tromsø (66.2 °N geomagnetic latitude) just after the CIR‐ and CME‐driven storms, corresponding to electron temperature enhancements due to soft particle precipitation and also ion temperature enhancements in the strong westward electric field region. The CME‐driven storms have larger upward ion flux (~1.7 × 1013 m−2s−1) than those under the CIR‐driven storms (~0.3 × 1013 m−2s−1). In the daytime, ion upflows are seen at Longyearbyen, Svalbard (75.2 °N geomagnetic latitude), with an upward flux of typically 1013 m−2s−1 for small CIR and CME storm cases. Substantial ion upflows last for a few days after the storm onsets under small CIR storms, whereas they last for only a day under small CME storms. Under both the cases, the substantial ion upflows are associated with an enhancement of the Region 1 field‐aligned current, eastward electric field and Joule heating rate. For large CME storms, substantial ion upflows are absent in the daytime probably due to equatorward expansion of the auroral oval.

IPIM Modeling of the Ionospheric F2 Layer Depletion at High Latitudes During a High‐Speed Stream Event

AbstractOur aim is to understand the effect of high‐speed stream events on the high‐latitude ionosphere and more specifically the decrease of the foF2 frequency during the entire day following the impact. First, we have selected one summertime event, for which a large data set was available: Super Dual Auroral Radar Network (SuperDARN) and European Incoherent SCATter (EISCAT) radars, Tromsø and Sodankylä ionosondes, and the CHAllenging Minisatellite Payload (CHAMP) satellite. We modeled with the IPIM model (IRAP Plasmasphere Ionosphere Model) the dynamics of the ionosphere at Tromsø and Sodankylä using inputs derived from the data. The simulations nicely match the measurements made by the EISCAT radar and the ionosondes, and we showed that the decrease of foF2 is associated with a transition from F2 to F1 layer resulting from a decrease of neutral atomic oxygen concentration. Modeling showed that electrodynamics can explain short‐term behavior on the scale of a few hours, but long‐term behavior on the scale of a few days results from the perturbation induced in the atmosphere. Enhancement of convection is responsible for a sharp increase of the ion temperature by Joule heating, leading through chemistry to an immediate reduction of the F2 layer. Then, ion drag on neutrals is responsible for a rapid heating and expansion of the thermosphere. This expansion affects atomic oxygen through nonthermal upward flow, which results in a decrease of its concentration and amplifies the decrease of [O]/[N2] ratio. This thermospheric change explains long‐term extinction of the F2 layer.

Energetic electron precipitation and auroral morphology at the substorm recovery phase

AbstractIt is well known that auroral patterns at the substorm recovery phase are characterized by diffuse or patch structures with intensity pulsation. According to satellite measurements and simulation studies, the precipitating electrons associated with these aurorae can reach or exceed energies of a few hundreds of keV through resonant wave‐particle interactions in the magnetosphere. However, because of difficulty of simultaneous measurements, the dependency of energetic electron precipitation (EEP) on auroral morphological changes in the mesoscale has not been investigated to date. In order to study this dependency, we have analyzed data from the European Incoherent Scatter (EISCAT) radar, the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) riometer, collocated cameras, ground‐based magnetometers, the Van Allen Probe satellites, Polar Operational Environmental Satellites (POES), and the Antarctic‐Arctic Radiation‐belt (Dynamic) Deposition‐VLF Atmospheric Research Konsortium (AARDDVARK). Here we undertake a detailed examination of two case studies. The selected two events suggest that the highest energy of EEP on those days occurred with auroral patch formation from postmidnight to dawn, coinciding with the substorm onset at local midnight. Measurements of the EISCAT radar showed ionization as low as 65 km altitude, corresponding to EEP with energies of about 500 keV.

Average field‐aligned ion velocity over the EISCAT radars

AbstractLong‐term measurements by the European Incoherent Scatter (EISCAT) radars at Tromsø (69.6°N, 19.2°E) and Svalbard (78.2°N, 16.0°E) are used to determine the climatology of the field‐aligned ion velocity in the F region ionosphere (175–475 km) at high latitudes. The average ion velocity is calculated at various altitudes and times of day. The magnitude of the average field‐aligned ion velocity is on the order of 10 m/s, similar to previous results at middle and low latitudes. The results obtained for the two radars are in good agreement. During daytime the direction of the average field‐aligned ion velocity changes from downward to upward around 350 km, while during nighttime it is upward at all heights. The reversal height of the daytime field‐aligned ion velocity depends on solar activity. It is elevated by more than 100 km during high solar flux periods compared to low solar flux periods. The Thermosphere Ionosphere Electrodynamics General Circulation Model reproduces the main features of the field‐aligned ion velocity climatology. The simulation results suggest that the plasma pressure gradient force and gravity force play a dominant role for the daytime field‐aligned ion motion. The height pattern of the field‐aligned ion velocity tends to be preserved in different solar activity conditions at constant pressure surfaces, but not at constant altitudes, which explains the observed dependence on solar activity. During nighttime, the effect of the neutral wind dominates the field‐aligned ion velocity.

Postmidnight ionospheric troughs in summer at high latitudes

AbstractIn this article we identify possible mechanisms for the formation of postmidnight ionospheric troughs during summer, in sunlit plasma. Four events were identified in measurements of European Incoherent Scatter and ESR radars during CP3 experiments, when the ionosphere was scanned in a meridional plan. The spatial and temporal variation of plasma density, ion, and electron temperatures were analyzed for each of the four events. Super Dual Auroral Radar Network plasma velocity measurements were added, when these were available. For all high‐latitude troughs the ion temperatures are high at density minima (within the trough), at places where the convection plasma velocity is eastward and high. There is no significant change in electron temperature inside the trough, regardless of its temporal evolution. We find that troughs in sunlit plasma form in two steps: the trough starts to form when energetic electron precipitation leads to faster recombination in the F region, and it deepens when entering a region with high eastward flow, producing frictional heating and further depleting the plasma. The high‐latitude plasma convection plays an important role in formation and evolution of troughs in the postmidnight sector in sunlit plasma. During one event a second trough is identified at midlatitudes, with different characteristics, which is most likely produced by a rapid subauroral ion drift in the premidnight sector.

Three‐dimensional modeling of high‐latitude scintillation observations

AbstractGlobal Navigation Satellite System signals exhibit rapid fluctuations at high and low latitudes as a consequence of propagation through drifting ionospheric irregularities. We focus on the high‐latitude scintillation problem, taking advantage of a conjunction of European Incoherent Scatter Radar (EISCAT) observations and a GPS scintillation monitor viewing the same line of sight. Just after 20:00 UT on 17 October 2013, an auroral E region ionization enhancement occurred with associated phase scintillations. This investigation uses the scintillation observations to estimate the ionospheric electron density distribution beyond the spatial resolution of EISCAT (5–15 km along the line of sight in this case). Following the approach of Deshpande et al. (2014), signal propagation is modeled through a specified density distribution. A multiple phase screen propagation algorithm is applied to irregularities conforming to the description of Costa and Kelley (1977) and constrained to match the macroscopic conditions observed by EISCAT. A 50‐member ensemble of modeled outputs is approximately consistent with the observations according to the standard deviation of the phase (σp). The observations have σp = 0.23 rad, while the ensemble of modeled realizations has σp = 0.23 + 0.04–0.04. By comparison of the model output with the scintillation observations, we show that the density fluctuations cannot be a constant fraction of the mean density. The model indicates that E region density fluctuations whose standard deviation varies temporally between 5 and 25% of the mean (EISCAT‐observed) density are required to explain the observed phase scintillations.

Electrodynamic structure of the morning high‐latitude trough region

AbstractWe describe the electrodynamics of a postmidnight, high‐latitude ionospheric trough, observed with the European Incoherent Scatter radar in northern Scandinavia on 24–25 June 2003 around 22:00–02:30 UT during quiet conditions. The UHF radar made meridian scans with a 30 min cadence resulting in nine cross sections of ionospheric parameters. The F region electric field was also determined with the tristatic system. Ionospheric equivalent currents, calculated from ground magnetometer data, mostly show an electrojet‐like current that is reasonably uniform in the longitudinal direction. Combined analysis of the conductances and equivalent current with a local Kamide‐Richmond‐Matsushita (KRM) method yields the ionospheric electric field and field‐aligned current (FAC) in a 2‐D (latitude‐longitude) area around the radar. We conclude that the most likely scenario is one where the trough is initially created poleward of the auroral oval by downward FAC that evacuates the F region, but as the trough moves to lower latitudes during the early morning hours, it becomes colocated with the westward electrojet. There the electron density further decreases due to increased recombination caused by enhanced ion temperature, which in turn is brought about by a larger convection speed. Later in the morning the convection speed decreases and the trough is filled by increasing photoionization.

A sporadic sodium layer event detected with five‐directional lidar and simultaneous wind, electron density, and electric field observation at Tromsø, Norway

AbstractA sporadic sodium layer (SSL) was detected with five‐directional lidar observation on 15 December 2012 at Tromsø, Norway. We have derived the horizontal velocity of the SSL front from the SSL onset times at the five positions and compared it with the background wind velocity from the collocated meteor radar and European Incoherent Scatter (EISCAT) radar. As a result, both velocities were fairly consistent. The increase rate in the height‐integrated sodium density around the SSL onset was 3–6 ×1010 m−2 s−1, which was comparable to relatively large cases in the previous studies. However, the EISCAT‐observed electric field was too small to induce such a rapid sodium atom production. In addition, the amounts of the sodium atom increases at the five positions were mostly same. Thus, there were no clear signatures for the sodium atom production. These results strongly indicate that the observed SSL was just advected by the background wind.

Auroral ion acoustic wave enhancement observed with a radar interferometer system

Abstract. Measurements of naturally enhanced ion acoustic line (NEIAL) echoes obtained with a five-antenna interferometric imaging radar system are presented. The observations were conducted with the European Incoherent SCATter (EISCAT) radar on Svalbard and the EISCAT Aperture Synthesis Imaging receivers (EASI) installed at the radar site. Four baselines of the interferometer are used in the analysis. Based on the coherence estimates derived from the measurements, we show that the enhanced backscattering region is of limited extent in the plane perpendicular to the geomagnetic field. Previously it has been argued that the enhanced backscatter region is limited in size; however, here the first unambiguous observations are presented. The size of the enhanced backscatter region is determined to be less than 900 × 500 m, and at times less than 160 m in the direction of the longest antenna separation, assuming the scattering region to have a Gaussian scattering cross section in the plane perpendicular to the geomagnetic field. Using aperture synthesis imaging methods volumetric images of the NEIAL echo are obtained showing the enhanced backscattering region to be aligned with the geomagnetic field. Although optical auroral emissions are observed outside the radar look direction, our observations are consistent with the NEIAL echo occurring on field lines with particle precipitation.

Solar wind effect on Joule heating in the high‐latitude ionosphere

AbstractThe effect of solar wind on several electrodynamic parameters, measured simultaneously by the European Incoherent Scatter (EISCAT) radars in Tromsø (TRO, 66.6° cgmLat) and on Svalbard (ESR, 75.4° cgmLat), has been evaluated statistically. The main emphasis is on Joule heating rate QJ, which has been estimated by taking into account the neutral wind. In addition, a generally used proxy QE, which is the Pedersen conductance times the electric field squared, has been calculated. The most important findings are as follows. (i) The decrease in Joule heating in the afternoon‐evening sector due to winds reported by Aikio et al. (2012) requires southward interplanetary magnetic field (IMF) conditions and a sufficiently high solar wind electric field. The increase in the morning sector takes place for all IMF directions within a region where the upper E neutral wind has a large equatorward component and the F region plasma flow is directed eastward. (ii) At ESR, an afternoon hot spot of Joule heating centered typically at 14–15 magnetic local time (MLT) is observed during all IMF conditions. Enhanced Pedersen conductances within the hot spot region are observed only for the IMF Bz + /By− conditions, and the corresponding convection electric field values within the hot spot are smaller than during the other IMF conditions. Hence, the hot spot represents a region of persistent magnetospheric electromagnetic energy input, and the median value is about 3 mW/m2. (iii) For the southward IMF conditions, the MLT‐integrated QE for By− is twice the value for By+ at TRO. This can plausibly be explained by the higher average solar wind electric field values for By−.