Thin Current Sheet Formation and Reconnection at X ∼ −10 RE During the Main Phase of a Magnetic Storm

The main question addressed in this study is whether particles with relativistic energy can be injected directly into the inner magnetosphere by very near‐Earth reconnection during magnetic storms. We study a sequence of events observed in the solar wind, in the magnetotail, at geosynchronous orbit (GEO), in the inner magnetosphere, and in the ionosphere during the main phase of a geomagnetic storm on 16 June 2012–17 June 2012. The storm was caused by a magnetic cloud with a high dynamic pressure and a strong southward IMF lasting about 10 hr. These conditions caused an extreme compression of the magnetosphere (SymH reached ∼150 nT) and an enhancement of the lobe magnetic field strength to ∼90 nT at R ∼ 10 Earth radii (RE). We focus on an hour‐long interval between 1050 and 1150 UT on 17 June 2012 when the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites were at apogee at geocentric distances R ≈ 12 RE near midnight. At that time a thin current sheet formed between cis‐GEO distances and THEMIS. This thin current sheet reconnected between GEO and THEMIS. A strong lobe magnetic field enabled ion and electron energization to energies E ≈ 600 keV. Fluxes of high energy (up to relativistic) particles at GEO increased within ≈20 s after reconnection onset detected by THEMIS. Fluxes of relativistic electrons at L ∼ 4 in the morning sector increased within about 600 s after reconnection onset. We interpret these observations as signatures of direct injection of reconnected particles into the inner magnetosphere.

[1]  J. Birn,et al.  Electron Anisotropies in Magnetotail Dipolarization Events , 2022, Frontiers in Astronomy and Space Sciences.

[2]  V. Angelopoulos,et al.  Global and local processes of thin current sheet formation during substorm growth phase , 2021 .

[3]  V. Angelopoulos,et al.  Magnetotail Dipolarizations and Ion Flux Variations During the Main Phase of Magnetic Storms , 2021, Journal of Geophysical Research: Space Physics.

[4]  V. Angelopoulos,et al.  Near-Earth Magnetotail Reconnection Powers Space Storms , 2019, Nature physics.

[5]  Daniel J. Price,et al.  Multipoint Observations of the June 2012 Interacting Interplanetary Flux Ropes , 2019, Front. Astron. Space Sci..

[6]  M. Velli,et al.  Explosive Magnetotail Activity , 2019, Space Science Reviews.

[7]  V. Merkin,et al.  Ion Trapping and Acceleration at Dipolarization Fronts: High‐Resolution MHD and Test‐Particle Simulations , 2018, Journal of Geophysical Research: Space Physics.

[8]  A. Runov,et al.  Near‐Earth Reconnection Ejecta at Lunar Distances , 2018 .

[9]  V. Sergeev,et al.  Does a Local B‐Minimum Appear in the Tail Current Sheet During a Substorm Growth Phase? , 2018 .

[10]  D. Baker,et al.  Extreme Space Weather Events: From Cradle to Grave , 2017, Space Science Reviews.

[11]  M. Kuznetsova,et al.  On the origin of plasma sheet reconfiguration during the substorm growth phase , 2017 .

[12]  D. Baker,et al.  The Global Positioning System constellation as a space weather monitor: Comparison of electron measurements with Van Allen Probes data , 2016 .

[13]  V. Angelopoulos,et al.  The role of localized inductive electric fields in electron injections around dipolarizing flux bundles , 2015 .

[14]  J. Birn,et al.  Energetic ions in dipolarization events , 2015 .

[15]  Juan V. Rodriguez,et al.  Source and seed populations for relativistic electrons: Their roles in radiation belt changes , 2015 .

[16]  D. A. Biesecker,et al.  Space weather conditions during the Galaxy 15 spacecraft anomaly , 2015 .

[17]  A. Otto,et al.  Thin current sheet formation in response to the loading and the depletion of magnetic flux during the substorm growth phase , 2015 .

[18]  A. Runov,et al.  Average thermodynamic and spectral properties of plasma in and around dipolarizing flux bundles , 2015 .

[19]  M. Fujimoto,et al.  Ion bulk heating in magnetic reconnection exhausts at Earth's magnetopause: Dependence on the inflow Alfvén speed and magnetic shear angle , 2014 .

[20]  J. Birn,et al.  Energetic electrons in dipolarization events: Spatial properties and anisotropy , 2014 .

[21]  J. B. Blake,et al.  Rapid local acceleration of relativistic radiation-belt electrons by magnetospheric chorus , 2013, Nature.

[22]  A. Runov,et al.  Magnetic flux transport by dipolarizing flux bundles , 2013 .

[23]  K. Mursula,et al.  Correcting the NOAA/MEPED energetic electron fluxes for detector efficiency and proton contamination , 2013 .

[24]  V. Angelopoulos,et al.  Electron bulk heating in magnetic reconnection at Earth's magnetopause: Dependence on the inflow Alfvén speed and magnetic shear , 2013 .

[25]  V. Angelopoulos,et al.  On the current sheets surrounding dipolarizing flux bundles in the magnetotail: The case for wedgelets , 2013 .

[26]  V. Angelopoulos,et al.  The effects of transient, localized electric fields on equatorial electron acceleration and transport toward the inner magnetosphere , 2012 .

[27]  V. Angelopoulos,et al.  Comparison between SuperDARN flow vectors and equivalent ionospheric currents from ground magnetometer arrays , 2012 .

[28]  D. Baker,et al.  Particle Acceleration in the Magnetotail and Aurora , 2012 .

[29]  Vassilis Angelopoulos,et al.  The ARTEMIS Mission , 2011 .

[30]  Martin Connors,et al.  Magnetic flux transfer in the 5 April 2010 Galaxy 15 substorm: an unprecedented observation , 2011 .

[31]  V. Angelopoulos,et al.  Application and validation of the spherical elementary currents systems technique for deriving ionospheric equivalent currents with the North American and Greenland ground magnetometer arrays , 2011 .

[32]  V. Angelopoulos,et al.  A THEMIS survey of flux ropes and traveling compression regions: Location of the near-Earth reconnection site during solar minimum , 2011 .

[33]  E. Quataert,et al.  Ion heating resulting from pickup in magnetic reconnection exhausts , 2009 .

[34]  V. Angelopoulos,et al.  Toward adapted time‐dependent magnetospheric models: A simple approach based on tuning the standard model , 2009 .

[35]  V. Angelopoulos,et al.  First application of a Petschek‐type reconnection model with time‐varying reconnection rate to THEMIS observations , 2009 .

[36]  I. J. Rae,et al.  The Upgraded CARISMA Magnetometer Array in the THEMIS Era , 2008 .

[37]  R. Abiad,et al.  The THEMIS ESA Plasma Instrument and In-flight Calibration , 2008 .

[38]  V. Angelopoulos,et al.  Study of near-Earth reconnection events with Cluster and Double Star , 2008 .

[39]  U. Auster,et al.  First Results from the THEMIS Mission , 2008 .

[40]  Werner Magnes,et al.  The THEMIS Fluxgate Magnetometer , 2008 .

[41]  A. Sharma,et al.  Transient and localized processes in the magnetotail: a review , 2008 .

[42]  J. D. Means,et al.  THEMIS Ground-Based Magnetometers , 2008 .

[43]  M. Fujimoto,et al.  Solar wind control of the radial distance of the magnetic reconnection site in the magnetotail , 2005 .

[44]  M. Henderson.  The May 2–3, 1986 CDAW‐9C interval: A sawtooth event , 2004 .

[45]  R. Skoug,et al.  Tail-dominated storm main phase: 31 March 2001 , 2003 .

[46]  A. Viljanen,et al.  Ionospheric disturbance magnetic field continuation from the ground to the ionosphere using spherical elementary current systems , 1999 .

[47]  J. Borovsky,et al.  Calculation of Moments from Measurements by the Los Alamos Magnetospheric Plasma Analyzer , 1999 .

[48]  Rumi Nakamura,et al.  Structure and dynamics of magnetic reconnection for substorm onsets with Geotail observations , 1998 .

[49]  V. A. Sergeev,et al.  Magnetospheric source region of discrete auroras inferred from their relationship with isotropy boundaries of energetic particles , 1997 .

[50]  L. J. Cahill,et al.  Magnetometer array for cusp and cleft studies observations of the spatial extent of broadband ULF magnetic pulsations at cusp/cleft latitudes , 1995 .

[51]  R. Nemzek,et al.  Flux dropouts of plasma and energetic particles at geosynchronous orbit during large geomagnetic storms: Entry into the lobes , 1995 .

[52]  M. F. Thomsen,et al.  Magnetospheric plasma analyzer for spacecraft with constrained resources , 1993 .

[53]  G. Gisler,et al.  High‐Z energetic particles at geosynchronous orbit during the Great Solar Proton Event Series of October 1989 , 1992 .

[54]  David G. Sibeck,et al.  An ISEE 3 study of average and substorm conditions in the distant magnetotail , 1985 .

[55]  V. A. Sergeev,et al.  Pitch-angle scattering of energetic protons in the magnetotail current sheet as the dominant source of their isotropic precipitation into the nightside ionosphere , 1983 .

[56]  S. Krimigis,et al.  Variability of plasma sheet dynamics , 1980 .