Magnetotail Reconnection T. Nagai Tokyo Institute of Technology Harry Petschek Symposium on Magnetic Reconnection March 22, 2006 Wednesday 12:00 – 12:30 AM

Geotail Near-Tail Orbit since x 30 Re July 24, 1992-

Geotail Near-Tail Observations Sun Solar Wind Magetosheath Magnetotail Bow Shock Magnetopause

Magnetotail Reconnection from Geotail Observations 1.In situ Observation of Reconnection Signatures of Reconnection Ion and Electron Behaviors 2.Observations of the Hall Current System Carriers of Currents Structure 3.Location of Magnetic Reconnection Controlling Factor in Solar Wind

Magnetotail Reconnection from Geotail Observations 1.In situ Observation of Reconnection Signatures of Reconnection Ion and Electron Behaviors 2.Observations of the Hall Current System Carriers of Currents Structure 3.Location of Magnetic Reconnection Controlling Factor in Solar Wind

Signatures of Magnetotail Reconnection Fast Tailward Flows Bz < 0 Fast tailward Flows with Bz < 0 Fast Earthward Flows with Bz > 0 Location of Magnetic Reconnection at R E in the Magnetotail Nagai et al. 1998

Bz = -36 nT Bt = 36 nT tail lobe Bt = 24 nT 10 sec Reconnection Event 1 Bz < 0 Fast Tailward Flows Bz Vx (X= -25.2, Y= 4.5, Z= -0.8)

Particle-code simulation for magnetic reconnection by I. Shinohara Bz < 0 Fast Plasma Flows Density Decrease

48 secHighly Accelerated Electrons High-Speed Tailward Flowing Ions

Highly Accelerated Electrons thermal accelerated Electron Energy Spectra Flux Energy

Particle simulation by I. Shinohara

Cluster Reconnection Event on August 24, 2003 Bz Vx Ions Electrons Nakamura et al (-16.8, -3.8, 3.3 Re)

Nagai et al. (JGR 1998) Ion Electron High-Speed Tailward Flowing Ions High ｌｙ Accelerated Electrons V=3000km/s Heated Inflow Ions High V Outflow Ions Convection Reconnection Event 2 EQ off EQ boundary Bz < 0 X GSM =-28.9 Y GSM =5.8 Z GSM =-2.6 R E Less Heated Inflow Ions Low V Outflow Ions Vx < 0

Nagai et al. (JGR 1998) Ion Electron High-Speed Tailward Flowing Ions High ｌｙ Accelerated Electrons V=3000km/s Heated Inflow Ions High V Outflow Ions Convection Reconnection Event 2 Boundary off EQ EQ Less Heated Inflow Ions Low V Outflow Ions CBACBA

Nagai et al. (JGR 1998) Ion Electron High-Speed Tailward Flowing Ions High ｌｙ Accelerated Electrons V=2500km/s Outflow Ions Convection Magnetotail Reconnection Event EQ Magnetic Field Direction B V Convection

Magnetic Field Direction B Distribution Functions V Convection B B VV Stationary Field-aligned flows Convection flows V B Convection flows with counter-streaming components V V //

Nagai et al. (JGR 1998) High-Speed Tailward Flowing Ions High ｌｙ Accelerated Electrons V=2500km/s Outflow Ions Convection Magnetotail Reconnection Event EQ Ion Electron

Nagai et al. (JGR 1998) High-Speed Tailward Flowing Ions High ｌｙ Accelerated Electrons V=3000km/s Heated Inflow Ions High V Outflow Ions Magnetotail Reconnection Event off EQ B Ion Electron

Nagai et al. (JGR 1998) Ion Electron High-Speed Tailward Flowing Ions High ｌｙ Accelerated Electrons V=3000km/s Magnetotail Reconnection Event Boundary Less Heated Inflow Ions Low V Outflow Ions C

Nagai et al. (JGR 1998) Ion Electron High-Speed Tailward Flowing Ions High ｌｙ Accelerated Electrons V=3000km/s Magnetotail Reconnection Event Boundary Less Heated Inflow Ions Low V Outflow Ions C Tailward Escaping Electrons Inflowing Electrons Hall Current Electrons

Magnetotail Reconnection from Geotail Observations 1.In situ Observation of Reconnection Signatures of Reconnection Ion and Electron Behaviors 2.Observations of the Hall Current System Carriers of Currents Structure 3.Location of Magnetic Reconnection Controlling Factor in Solar Wind

December 10, 1996 High-Speed Ion Flows Highly Accelerated Electrons Reconnection Event 3 Earthward Flows Tailward Flows

Hall Current System Earthward Tailward Northern hemisphere Southern hemisphere Nagai et al. (JGR 2001)

Cluster Observations Asano et al. 2006

Earthward Side Southern Hemisphere Nagai et al. (JGR 2003)

Tailward Side Northern Hemisphere Nagai et al. (JGR 2003)

The Hall current loops exist with the double-current structure in the narrow regions near the separatrix layers. Geotail Observations Nagai et al. JGR 2003

Nagai et al. (JGR 1998) Ion Electron High-Speed Tailward Flowing Ions High ｌｙ Accelerated Electrons V=2500km/s Outflow Ions Convection Magnetotail Reconnection Event EQ Hall current density J = 10 nA/m 2

Particle Simulation by I. Shinohara Currents and By

Magnetotail Reconnection from Geotail Observations 1.In situ Observation of Reconnection Signatures of Reconnection Ion and Electron Behaviors 2.Observations of the Hall Current System Carriers of Currents Structure 3.Location of Magnetic Reconnection Controlling Factor in Solar Wind

In Situ Observations of Magnetic Reconnection by Geotail Early Geotail Results Reconnection most frequently forms at R E Nagai et al. 1998

Nagai et al. (JGR 2005) Question Is there any factor that controls the site of magnetic reconnection in the magnetotail?

In Solar Minimum Low B and Low V Solar Maximum High B and High V Solar Wind IMF Bt Velocity

Geotail Near-Tail Observations 10 x 30 R E orbit Plasma Sheet (β> 1) X GSM = -10 to -31 R E and Y GSM = -5 to +10 R E

Solar Wind Parameters Prior to Each Reconnection Event Total 34 Events Solar Wind Parameters during 60 minutes prior to each reconnection event

Solar Wind Velocity? circles events black dots events

Solar Wind Dynamic Pressure? circles events black dots events

Southward IMF Bz circles events black dots events

Southward IMF Bz X = -25 R E circles events black dots events

Solar Wind Energy Input (Interplanetary Electric Field) circles events black dots events

Solar Wind Energy Input X = -25 R E Near-Tail Midtail circles events black dots events

Average solar wind parameters for the period from -6 to +2 hours Reconnection Start Time 9 events 25 events Near-tail Reconnection Midtail Reconnection

Solar Wind Energy Input Near-tail Reconnection Midtail Reconnection

Near-Tail Reconnection Midtail Reconnection Accumulation of Solar Wind Energy Input

Solar Wind Velocity Near-Tail Reconnection Midtail Reconnection High Velocity 520 km/s Low velocity 460 km/s

Solar Wind Dynamic Pressure Near-Tail Reconnection Midtail Reconnection 2 nPa high velocity and low density 2 nPa low velocity and high density

Near-Tail Reconnection Midtail Reconnection Accumulation of Solar Wind Energy Input Solar Wind Input Energy x 2

Near-Tail Midtail The solar wind energy input controls the magnetic reconnection site.

Past Spacecraft Observations Vela Hones et al., 1971; 1973 IMP Hones and Schindler, 1979 ISEE-11980Cattell and Mozer, 1984 ISEE Angelopoulos et al CDAW-6McPherron and Manka, 1985 IRM Baumjohann et al., 1988,1989,1990,1991 Geotail Nagai et al This study Cluster Nakamura et al., 2004

Russell (1972) Nishida and Nagayama (1973) Earlier Brief “Reconnection Location 15 R E Hones et al., 1973”

Reconnection Locations from Past Spacecraft Observations Vela ReNear-Tail IMP Support Vela Results ISEE-11980> 20 ReMidtail ISEE > 20 ReMidtail IRM > 20 ReMidtail Geotail ReMidtail Cluster ReNear-Tail

Reconnection Locations from Past Spacecraft Observations Vela ReNear-TailHigh Kp IMP Support Vela ResultsHigh Kp ISEE-11980> 20 ReMidtailLow Kp ISEE > 20 ReMidtailLow Kp IRM > 20 ReMidtailLow Kp Geotail ReMidtailLow Kp Cluster ReNear-TailHigh Kp

Midtail Near-Tail VB = 1171Kp-18

Near-Tail Midtail The solar wind energy input controls the magnetic reconnection site. High Kp Low Kp

Conclusions on Magnetotail Reconnection from Geotail Observations 1.ReconnectionAcceleration and Heating Ion Scale High-speed outflowing ions and electrons Heated inflowing ions Large (negative) Bz 2.Hall Current System Ion - Electron Medium-energy inflowing electrons Decoupling Double-sheet structure 3.Location of Magnetic Reconnection MHD Controlled by solar wind energy input Magnetic reconnection forms close to (far from) the Earth in the magnetotail for high (low) solar wind energy input conditions

Bz 0 Tailward Flow Earthward Flow Encounter of Magnetic Reconnection Flow Reversal inside the plasma Sheet Geotail May 15, 2003 Event

SCOPE In planning phase at ISAS/JAXA Launch ~2015 High-time resolution Electron measurements The daughter s/c dedicated to wave-particle Interaction issue Ion scale dynamics monitors Electron scale Ion scale

SCOPE ele.-scale kernel ～１００ｋｍ Ion-scale shell ～１０００ｋｍ MHD-scale monitors ESA-ISAS “CrossScale”

Nagai et al. (JGR 1998) Ion Electron High-Speed Tailward Flowing Ions High ｌｙ Accelerated Electrons V=2500km/s Outflow Ions Convection Magnetotail Reconnection Event EQ Hall current density J = 10 nA/m 2

The Hall current loops exist with the double-current structure in the narrow regions near the separatrix layers. Geotail Observations Nagai et al. JGR 2003

Particle Simulation by I. Shinohara Currents and By

Hall Current System Model

Event /01/30 expansion phase ~60 min onset

Event /01/30

active aurorano active aurora no flow interval Event /01/30 multiple-onset substorm Geotail Foot Point MLT

no flow interval Event /01/30 multiple-onset substorm まとめー２ 個々のオンセットが それぞれ磁気リコネクションに対応 Substorm often has multiple onset. Each onset is associated with new magnetic reconnection. 磁気リコネクションが起きていない時は active aurora が 存在しない。

170934UT.

174014UT.

180446UT.

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Counterstreaming Ions Magnetic Field Nagai et al., Phys. Plasmas 9, 3705, 2002

M. S. Nakamura Hybrid-code Simulation

Counterstreaming Ions Magnetic Field Magnetic Reconnection in the Distant Tail Nagai et al., Phys. Plasmas 9, 3705, 2002

Event /02/26 double-peak ions counter-streaming Inflowing from NS electrons (Hall current) UT UT Bz Bt Vx 20 minutes

Counterstreaming Electrons

By By < 0 Southern Hemisphere Northern Hemisphere

m e /m i 1/100 Particles33,554,432(Av. 128 /grid) Grid Size512 x 512 Ion Inertial Length32 grids Electron Inertial Length3.2 grids Initial Current Thickness0.5 i (Harris Current Sheet) Double-Periodic Boundary Conditions Resultsat time  i t = D Full Particle Simulations I. Shinohara

October 2003 Storm 2104 UT 30 October 2003 Solar wind V > 1300 km/s Bz = -30 nT Vx = -150 km/s Bz = -50 nT Geotail X GSM =-8.6R E

Location of Magnetic Reconnection in the Magnetotail VelaEvent studiesKp = 3+ (5-)Near-Tail IMP 6Event StudiesKp = 3+ (2+)Near-Tail ISEE 1,2Event StudiesKp = 3- SurveyKp = 2Midtail IRMSurveyKp = 2Midtail GeotailSurveyKp = 2-Solar MinMidtail SurveyKp = 2+Solar Max ClusterEvent StudiesKp = 3+Near-Tail