Flux Transfer Events Research Articles

Crater FTEs: Simulation results and THEMIS observations

The BATS‐R‐US magnetohydrodynamic (MHD) model predicts flux transfer events (FTEs) with strong core magnetic fields embedded within a broadened current layer of weak magnetic field strengths on the equatorial dayside magnetopause during intervals of southward and duskward interplanetary magnetic field (IMF) orientation. Multipoint THEMIS observations at 2202 UT on June 20, 2007 of a southward‐moving FTE on the post‐noon magnetopause confirm the predictions of the model. THEMIS‐E and ‐A with large impact parameters simply observe enhanced magnetic field strengths in draped magnetosheath magnetic field lines, THEMIS‐B and ‐C with moderate impact parameters pass through the broadened current layer to observe crater FTEs with deep troughs bounding a strong core field, while THEMIS‐D with a very low impact parameter observes the core magnetic field strength enhancement embedded in the current layer.

Cluster observations of “crater” flux transfer events at the dayside high‐latitude magnetopause

On 11 January 2002 Cluster detected two “crater”‐like flux transfer event (FTE) signatures. The four spacecraft were in quasi‐linear formation, spread over ∼2 RE in the magnetopause normal direction, and sample a range of distances from it. The observations occur near a southward turning of the IMF, but no solar wind pressure pulses are detected. Analysis reveals: (1) C3, closest to the magnetopause, made two transient excursions into the magnetosheath which bracket two “crater”‐FTE signatures detected at the other three spacecraft; (2) magnetic field deflections observed at the other spacecraft do not match the magnetosheath field direction at C3; (3) these FTE signatures involve encounters with reconnected field lines and associated boundary layers lying just inside the magnetopause, including a “separatrix layer” of accelerated magnetosheath electrons and an injection of magnetosheath ions. Under the observed conditions, reconnected flux tubes created by a transient and localized patch of reconnection located nearer to the subsolar point, will move northward and duskward over Cluster, consistent with observations inside the magnetosphere. The FTE signatures arise from this transient inward motion of reconnection‐associated boundary layers over the spacecraft. We postulate that the transient relocation of C3 into the magnetosheath is due to a region of eroded magnetic flux, lying in the wake of the recoiling FTE, which itself is driven duskward at some fraction of the magnetosheath flow speed. The FTEs pass northward of C3, but the eroded wake, which we term the “traveling magnetopause erosion region” (TMER), is located equatorward of the FTEs and moves duskward over C3.

Seasonal dependence of Interball flux transfer events

[1] J. Raeder (2006) presented the results of a global magnetohydrodynamic simulation indicating that flux transfer events (FTEs) form solely in the winter hemisphere and move poleward in the direction of the background magnetosheath flow during periods of strongly southward interplanetary magnetic field (IMF) orientation. This paper presents results from a statistical survey of flux transfer FTEs observed on the mid-latitude northern and southern magnetopause by the magnetometer on the Interball-1 spacecraft over the course of its five-year mission from 1995 to 1999. Interball-1 observations confirm that FTEs exhibit a strong tendency to occur in the winter hemisphere.

Multiscale/multifluid simulations of flux ropes at the magnetopause within a global magnetospheric model

The magnetopause current sheet is known to have a thickness comparable to an ion gyroradius/skin depth where the magnetic and electric field can differ markedly from that assumed in MHD treatments. Multifluid/multiscale simulations are used to provide the first investigation of these processes in a global simulation that includes high‐resolution (200 km) gridding around the magnetopause. It is shown that the model is able to capture the quadrupole core magnetic field and the fast (tens of ion cyclotron periods) reconnection seen in idealized studies reconnection for a Harris current sheet. Within a global magnetosphere, multiple X‐line reconnection occurs for southward IMF due to localized pinching of the magnetopause current sheet via the convection of the magnetosheath plasma against a three‐dimensional magnetopause. Localized flux ropes with a thickness of a few hundred to a few thousand kilometers develop and can expand laterally due to current sheet acceleration of ions that have a gyroradius comparable to the current sheet thickness. These flux ropes are shown to have essentially the same properties as flux transfer events (FTEs), including being quasi‐periodic with a curvature greater on the magnetosheath side than on the magnetospheric side, a strong core magnetic field, and a mixture of magnetospheric and magnetosheath plasma. The speeds of the plasma flows associated with flux ropes are also similar to those observed with FTEs. The presence of multiple X‐line reconnection is shown to produce the rippling of the magnetopause and gives a nature explanation to the multiple magnetopause encounters that typically occur for slow moving spacecraft. These small‐scale processes are shown to have global effects with a reduction of the cross‐polar cap by as much as 20% seen between simulations with and without high resolution about the magnetopause.

Modeling a force‐free flux transfer event probed by multiple Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft

A flux transfer event (FTE) was encountered by all five Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft just outside the dusk magnetopause on 20 May 2007. In the present paper, we fit the magnetic field observations from multiple satellites to a flux rope model in order to obtain the critical geometric parameters of this FTE. The model used includes both electromagnetic force and pressure gradient force and reduces to a force‐free model when the magnetic tension is balanced mainly by the magnetic pressure gradient. The cross‐sectional scales of the FTE were estimated to be 0.6 × 1.3 RE. The core field direction is found to differ only slightly from the results of the minimum variance analysis and the Grad‐Shafranov technique. The maximum electric current density within the FTE was ∼100 nA/m2 and the total current was 0.3 MA, which is comparable with the current per RE flowing on the local magnetopause. The magnetic flux inside the FTE was ∼4 × 105 Wb. Magnetic field data and plasma data show that this FTE was fully embedded in the boundary region between the magnetosheath and the magnetosphere. The magnetic configuration and the flow distribution around the FTE suggest that X lines were present both ahead of and behind the FTE, but we cannot determine whether these X lines formed synchronously. Our observations favor the conclusion that multiple X line models are the candidate mechanisms for the generation of this FTE, and some of the FTE's features cannot be understood in the frame of any single X line FTE model.

Simultaneous Cluster and CUTLASS Observations of FTEs on 11 February 2004

AbstractThis paper analyzes the simultaneous observations of the Flux Gate Magnetometer (FGM) and Plasma Electron and Current Experiment (PEACE) on Cluster Spacecraft, and the CUTLASS Finland radar between 11:00 and 11:40 UT on 11 February 2004. In this interval, the Cluster spacecraft array encountered the northern hemisphere high altitude cusp, and crossed the magnetopause into the magnetosheath at about 11:18 UT. A large number of flux transfer events (FTEs) were observed by all 4 Cluster spacecraft. It is found that these FTEs appeared quasi‐periodically with a period of about 130 s. Since all 4 Cluster spacecraft observed these FTEs, we applied the four‐spacecraft techniques “Minimum Directional Derivative (or Difference)” (MDD) and “Spatio‐temporal Difference” (STD) to calculate the dimension, motion and scale of these FTEs. The inferred northwardly reconnected flux tubes for these FTEs are shown to move northward or north‐east and tailward with a quasi‐2‐D structure and a scale of (0.87 ~ 1.81)RE. The ionospheric footprint of the Cluster spacecraft during the boundary passage is shown to map centrally within the field‐of‐view of the CUTLASS Finland radar. It is shown that the backscatter power of CUTLASS data is enhanced in synchronously with the magnetospheric FTEs at the latitude of the Cluster footprint. These radar auroral features in the radar subsequently propagated poleward, forming classic “poleward‐moving radar auroral form” structures at higher latitudes. The FTE motions meanwhile are shown to be consistent with the expected motion of reconnected magnetic flux tubes over the surface of the magnetopause, arising from a predominantly sub‐solar reconnection site during the prevailing upstream conditions.

Reconstruction of a flux transfer event based on observations from five THEMIS satellites

We investigate a flux transfer event (FTE) observed by Time History of Events and Macroscale Interactions during Substorms (THEMIS) near the duskside magnetopause using the reconstruction technique based on solving the Grad‐Shafranov equation; see review by Sonnerup et al. (2006). THEMIS D detected the FTE with the largest core magnetic field. THEMIS B and C observed deep troughs in the magnetic field associated with the FTE. THEMIS A and E sensed only slightly altered magnetic field from their surroundings. Two‐dimensional reconstruction maps of magnetic field and plasma pressure are generated by combining observations from all five THEMIS satellites. These reconstructed maps show distinct differences between a magnetic island and an FTE in terms of vector potential and the derived plasma parameters. The origin of the magnetic field troughs in the crater FTEs can be traced to intrusions of the magnetosheath plasma around the structure in the reconstruction maps. Furthermore, the resulting maps show also cylindrical asymmetry in these parameters between the magnetosheath and magnetospheric sides of the FTE. This asymmetry and the different impact parameters of these satellites with respect to the FTE center together contribute to the different characteristics of the FTE signatures seen by the five THEMIS satellites.

Flux transfer events simultaneously observed by Polar and Cluster: Flux rope in the subsolar region and flux tube addition to the polar cusp

In this paper we present observational evidence of a flux transfer event observed simultaneously at low‐latitude by Polar and at high‐latitude by Cluster. This event occurs on 21 March 2002, when both Cluster and Polar are located near local noon but with a large latitudinal separation. During the event, Cluster is moving outbound from the polar cusp to the magnetosheath and Polar is in the magnetosheath near the equatorial magnetopause. The observations show that a flux transfer event occurs between the equator and the northern cusp. Polar and Cluster observe the FTE's two open flux tubes: Polar encounters the southward moving flux tube near the equator and Cluster encounters the northward moving flux tube at high latitude. The low‐latitude FTE appears to be a flux rope with helical magnetic field lines as it has a strong core field and the magnetic field component in the boundary normal direction exhibits a strong bipolar variation. Unlike the low‐latitude FTE, the high‐latitude FTE observed by Cluster does not exhibit the characteristic bipolar perturbation in the magnetic field. However, the plasma data clearly reveal its open flux tube configuration. It shows that the magnetic field lines have straightened inside the FTE and become more aligned to the neighboring flux tubes as it moves to the cusp. Enhanced electrostatic fluctuations have been observed within the FTE core, both at low and high latitudes. This event provides a unique opportunity to understand high‐latitude FTE signatures and the nature of time‐varying reconnection. It shows that existing FTE models cannot accommodate all the features in global observations, and coordinated measurements from largely spaced multiple spacecraft place important constraints which are crucial to the development and refinement of FTE models.

Electromagnetic energy deposition rate in the polar upper thermosphere derived from the EISCAT Svalbard radar and CUTLASS Finland radar observations

Abstract. From simultaneous observations of the European incoherent scatter Svalbard radar (ESR) and the Cooperative UK Twin Located Auroral Sounding System (CUTLASS) Finland radar on 9 March 1999, we have derived the height distributions of the thermospheric heating rate at the F region height in association with electromagnetic energy inputs into the dayside polar cap/cusp region. The ESR and CUTLASS radar observations provide the ionospheric parameters with fine time-resolutions of a few minutes. Although the geomagnetic activity was rather moderate (Kp=3+~4), the electric field obtained from the ESR data sometimes shows values exceeding 40 mV/m. The estimated passive energy deposition rates are also larger than 150 W/kg in the upper thermosphere over the ESR site during the period of the enhanced electric field. In addition, enhancements of the Pedersen conductivity also contribute to heating the upper thermosphere, while there is only a small contribution for thermospheric heating from the direct particle heating due to soft particle precipitation in the dayside polar cap/cusp region. In the same period, the CUTLASS observations of the ion drift show the signature of poleward moving pulsed ionospheric flows with a recurrence rate of about 10–20 min. The estimated electromagnetic energy deposition rate shows the existence of the strong heat source in the dayside polar cap/cusp region of the upper thermosphere in association with the dayside magnetospheric phenomena of reconnections and flux transfer events.

Interball observations of multiple flux transfer events

We present results from a statistical study of multiple flux transfer events (FTEs) observed by the Interball-1 spacecraft during 1995–1999. We identified 21 days on which Interball-1 observed 10 or more FTEs. In a database of 807 FTEs, 319 can be identified as multiple FTEs with recurrence times ranging between 50 s and 20 min. Multiple events occur at both equatorial and high latitudes but are most frequently seen on Interball-1 passes that graze the flanks of the magnetosphere. The peak-to-peak amplitudes of multiple FTE Bn signatures vary from 3 to 20 nT but typically lie in the range from 3 to 9 nT, less than amplitudes typical for the FTE database as a whole. The durations of individual FTEs increase with increasing inter-arrival times during sequences of multiple FTEs. Multiple FTEs show a marked tendency to occur for southward IMF orientations, but no preference for high or low solar wind dynamic pressures or velocity. Since the conditions favoring the occurrence of multiple FTEs are similar to those for FTEs as a whole, we conclude that sequences of multiple FTEs must be the norm during periods of southward IMF orientation.

Reconstruction of the reconnection rate from Cluster measurements: Method improvements

[1] A remote-sensing method for reconstructing the reconnection rate and the location of X-line from single-spacecraft observations developed recently is extended to a compressible plasma and an asymmetric magnetic field configuration. The method is based on the two-dimensional analytical model of time-dependent Petschek-type magnetic reconnection. The reconstruction technique is applied to a nightside flux transfer event recorded by Cluster spacecraft in the near-Earth magnetotail on 26 September 2005. The reconnection rate is found to be 3.7–4.8 mV/m; the reconnection distance is around 9–11 Re in the tail.

Reversed flow events in the winter cusp ionosphere observed by the European Incoherent Scatter (EISCAT) Svalbard radar

High‐resolution fast azimuth sweeps by the European Incoherent Scatter (EISCAT) Svalbard radar provide an unparalleled opportunity to study small‐scale flow disturbances in the cusp ionosphere. Observations from 11 days of the winter cusp ionosphere of high‐resolution ion flow data have been analyzed. Transient channels of reversed plasma flow appear to be a regular feature of the cusp, and they were seen in 16% of 767 analyzed EISCAT Svalbard Radar (ESR) scans. We introduce a new descriptive term, reversed flow events (RFEs), for this class of events. RFEs are defined as longitudinally elongated segments of transiently enhanced ion flow in the direction opposite to the background flow. RFEs typically occurred near the cusp inflow region in association with enhancements in the polar cap convection observed by the Super Dual Auroral Radar Network (SuperDARN). Their lifetime was found to be ∼19 min on average. Their longitudinal dimension typically exceeded the ESR field of view (>400–600 km), and ranged from ∼50 to 250 km in latitude. The occurrence rate of RFEs appears independent of the BZ and BY component polarity of the interplanetary magnetic field (IMF), and RFEs occurred for clock angles between 40° and 240°. RFE ion flow was in 95% of the cases documented to oppose the magnetic tension force, and RFEs cannot be interpreted in terms of newly opened flux. RFEs formed one by one and never simultaneously in pairs. To explain these observations, we propose an asymmetric version of the Southwood (1987) twin cell flux transfer event model to account for significant IMF BY, in which only the poleward cell located on open field lines develops.

Motion of flux transfer events: a test of the Cooling model

Abstract. The simple model of reconnected field line motion developed by Cooling et al. (2001) has been used in several recent case studies to explain the motion of flux transfer events across the magnetopause. We examine 213 FTEs observed by all four Cluster spacecraft under a variety of IMF conditions between November 2002 and June 2003, when the spacecraft tetrahedron separation was ~5000 km. Observed velocities were calculated from multi-spacecraft timing analysis, and compared with the velocities predicted by the Cooling model in order to check the validity of the model. After excluding three categories of FTEs (events with poorly defined velocities, a significant velocity component out of the magnetopause surface, or a scale size of less than 5000 km), we were left with a sample of 118 events. 78% of these events were consistent in both direction of motion and speed with one of the two model de Hoffmann-Teller (dHT) velocities calculated from the Cooling model (to within 30° and a factor of two in the speed). We also examined the plasma signatures of several magnetosheath FTEs; the electron signatures confirm the hemisphere of connection indicated by the model in most cases. This indicates that although the model is a simple one, it is a useful tool for identifying the source regions of FTEs.

Magnetosphere–Ionosphere Convection as a Compound System

Convection is the most fundamental process in understanding the structure of geospace and disturbances observed in the magnetosphere–ionosphere (M–I) system. In this paper, a self-consistent configuration of the global convection system is considered under the real topology as a compound system. Investigations are made based on the M–I coupling scheme by analyzing numerical results obtained from magnetohydrodynamic (MHD) simulations which guarantee the self-consistency in the whole system under the Bv (magnetic field and velocity) paradigm. It is emphasized in the M–I coupling scheme that convection and field-aligned current (FAC) are different aspects of same physical process characterizing the open magnetosphere. Special attention is given in this paper to the energy supplying (dynamo) process that drives the FAC system. In the convection system, the dynamo must be constructed from shear motion together with plasma population regimes to steadily drive the convection. Convection patterns observed in the ionosphere are also the manifestation of achievement in global self-consistency. A primary approach to apply these concepts to the study of geospace is to consider how the M–I system adjusts the relative motion between the compressible magnetosphere and the incompressible ionosphere when responding to given solar-wind conditions. The above principle is also applicable for the study of disturbance phenomena such as the substorm as well as for the study of apparently unique processes such as the flux transfer event (FTE), the sudden commencement (SC), and the theta aurora. Finally, an attempt is made to understand the substorm as the extension of enhanced convection under the southward interplanetary magnetic field (IMF) condition.

Role of poleward moving auroral forms in the dawn‐dusk auroral precipitation asymmetries induced by IMF By

In a case study we document the detailed spatial/temporal structure of the aurora in the 0900–1500 magnetic local time (MLT) sector during an interval of steady southeast IMF orientation. Emphasis is placed on ground‐based observations of structure that is often averaged out in large statistical studies. A central feature is the phenomenon of poleward moving auroral forms (PMAFs), an ionospheric manifestation of pulsed magnetopause reconnection in the form of flux transfer events, FTEs, whose evolution in both prenoon and postnoon MLTs can be monitored under similar interplanetary conditions. Differences in auroral precipitation associated with PMAFs about the noon meridian related to IMF By are documented. While the prenoon PMAFs develop in three stages spanning a latitude range of ≥500 km, the highest‐latitude stage is absent in postnoon PMAFs for By > 0, which, after the initial intensification, progressively fade. We suggest that this auroral precipitation asymmetry is closely related to the different field‐aligned current configuration in PMAFs/prenoon and PMAFs/postnoon and the underlying plasma convection pattern. We detail the association between the high‐latitude component of PMAFs in the prenoon sector (By > 0) and a channel of plasma convection located in the dawnside convection cell. The latter convection channel, located in the regime of old open flux, represents an aspect of the Svalgaard‐Mansurov effect which is not included in the traditional description. The auroral and plasma convection data are placed in the context of recent work on solar wind‐magnetosphere interconnection topology for a southward pointing IMF with a strong By‐component.

Flux transfer events in the cusp

We use 2.5‐dimensional global hybrid (kinetic ions, fluid electrons) simulations to study the evolution of Flux Transfer Events (FTEs) and their interaction with the cusp during their poleward motion. A southward pointing interplanetary magnetic field is considered. It results in low‐latitude, time‐dependent reconnection and the formation of multiple FTEs with a variety of sizes ranging from a few hundred to thousands of km. FTEs are found to travel along the magnetopause surface with velocities exceeding the surrounding magnetosheath by ∼1 local Alfven speed. As a result, a slow mode bow wave and a pile up of plasma and magnetic field precede larger, but not smaller, FTEs. As an FTE encounters the cusp, a secondary magnetic reconnection is initiated which ultimately leads to its disintegration as it moves to higher latitudes. Both the slow mode bow wave and reconnection accelerate plasma into the cusp and enhance the flux of energetic ions in this region. The downward flux of ions at a given energy moves poleward in time, exhibiting characteristics similar to the poleward moving auroral forms previously attributed to FTEs.

On the location of dayside magnetic reconnection during an interval of duskward oriented IMF

Abstract. We present space- and ground-based observations of the signatures of magnetic reconnection during an interval of duskward-oriented interplanetary magnetic field on 25 March 2004. In situ field and plasma measurements are drawn from the Double Star and Cluster satellites during traversals of the pre-noon sector dayside magnetopause at low and high latitudes, respectively. These reveal the typical signatures of flux transfer events (FTEs), namely bipolar perturbations in the magnetic field component normal to the local magnetopause, enhancements in the local magnetic field strength and mixing of magnetospheric and magnetosheath plasmas. Further evidence of magnetic reconnection is inferred from the ground-based signatures of pulsed ionospheric flow observed over an extended interval. In order to ascertain the location of the reconnection site responsible for the FTEs, a simple model of open flux tube motion over the surface of the magnetopause is employed. A comparison of the modelled and observed motion of open flux tubes (i.e. FTEs) and plasma flow in the magnetopause boundary layer indicates that the FTEs observed at both low and high latitudes were consistence with the existence of a tilted X-line passing through the sub-solar region, as suggested by the component reconnection paradigm. While a high latitude X-line (as predicted by the anti-parallel description of reconnection) may have been present, we find it unlikely that it could have been responsible for the FTEs observed in the pre-noon sector under the observed IMF conditions. Finally, we note that throughout the interval, the magnetosphere was bathed in ULF oscillations within the solar wind electric field. While no one-to-one correspondence with the pulsed reconnection rate suggested by the ground-based observation of pulsed ionospheric flow has been demonstrated, we note that similar periodicity oscillations were observed throughout the solar wind-magnetosphere-ionosphere system. These findings are consistent with previously proposed mechanisms of solar wind modulation of the dayside reconnection rate.

TC1 and Cluster observation of an FTE on 4 January 2005: A close conjunction

Observations of a Flux Transfer Event (FTE) signature at the dayside magnetopause are reported, which was consecutively observed on 4 January 2005 by both the Double Star/TC1 spacecraft and the Cluster quartet, while the spacecraft were traversing through the northern‐dusk magnetopause. The event occurred as a magnetosheath FTE first at the Cluster spacecraft at about 07:13 UT on 4 January 2005 and crossed each of the others within 2 minutes. The spatial separations between the Cluster spacecraft were of the order of 200 km. The TC1 signature occurred about 108s after Cluster. All findings including magnetic fluxes, orientations and hot ion velocity distributions strongly suggest that Cluster and TC1 encountered the magnetosheath branch of the same flux tube at two different positions along its length and this is borne out by computation of the expected time delay. Four‐spacecraft timing is used to obtain the velocity of FTE.

Review of Ionospheric Effects of Solar Wind Magnetosphere Coupling in the Context of the Expanding Contracting Polar Cap Boundary Model

This paper reviews the coupling between the solar wind, magnetosphere and ionosphere. The coupling between the solar wind and Earth’s magnetosphere is controlled by the orientation of the Interplanetary Magnetic Field (IMF). When the IMF has a southward component, the coupling is strongest and the ionospheric convection pattern that is generated is a simple twin cell pattern with anti-sunward flow across the polar cap and return, sunward flow at lower latitudes. When the IMF is northward, the ionospheric convection pattern is more complex, involving flow driven by reconnection between the IMF and the tail lobe field, which is sunward in the polar cap near noon. Typically four cells are found when the IMF is northward, and the convection pattern is also more contracted under these conditions. The presence of a strong Y (dawn-dusk) component to the IMF leads to asymmetries in the flow pattern. Reconnection, however, is typically transient in nature both at the dayside magnetopause and in the geomagnetic tail. The transient events at the dayside are referred to as flux transfer events (FTEs), while the substorm process illustrates the transient nature of reconnection in the tail. The transient nature of reconnection lead to the proposal of an alternative model for flow stimulation which is termed the expanding/contracting polar cap boundary model. In this model, the addition to, or removal from, the polar cap of magnetic flux stimulates flow as the polar cap boundary seeks to return to an equilibrium position. The resulting average patterns of flow are therefore a summation of the addition of open flux to the polar cap at the dayside and the removal of flux from the polar cap in the nightside. This paper reviews progress over the last decade in our understanding of ionospheric convection that is driven by transient reconnection such as FTEs as well as by reconnection in the tail during substorms in the context of a simple model of the variation of open magnetic flux. In this model, the polar cap expands when the reconnection rate is higher at the dayside magnetopause than in the tail and contracts when the opposite is the case. By measuring the size of the polar cap, the dynamics of the open flux in the tail can be followed on a large scale.

Modeled variations of the reconnection electric field at the dayside magnetopause during continued flux transfer event activity

Three periods of repeated flux transfer event (FTE) observations made by the Cluster satellites are investigated by a novel method for extracting from the observations the reconnection electric field Erec. On 21 January 2001, a series of FTEs is observed at the poleward edge of the cusp around 15 magnetic local time (MLT). Another series of FTEs is observed on 14 February 2001, at somewhat earlier MLTs at the high‐latitude magnetopause at the equatorward edge of the cusp. In both cases, ground‐based radar observations confirm that Cluster observations refer to transient reconnection. Additionally, we consider an event of several magnetosheath FTEs on 26 January 2001, during very steady interplanetary conditions. Here we apply a model based on time‐dependent Petschek‐type magnetic reconnection to the in situ magnetic field data to obtain the temporal variations of the reconnection electric field responsible for each FTE of the three series. On 14 February 2001 we find peak average values of Erec = 2.1 ± 0.4 mV/m for the magnetospheric FTEs and peak average values Erec = 0.9 ± 0.5 mV/m for the magnetosheath FTEs. The corresponding result for the four FTEs on 21 January 2001 is 3.7 ± 0.8 mV/m. Finally, the four FTEs observed on 26 January 2001 give a reconnection rate of 2.85 ± 1.68 mV/m. These results are discussed in the context of estimates of the reconnection electric field at the magnetopause obtained from diverse techniques.