Multi Spacecraft Observation of Compressional Mode ULF Waves Excitation and Relativistic Electron Acceleration

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1 Multi Spacecraft Observation of Compressional Mode ULF Waves Excitation and Relativistic Electron Acceleration X. Shao 1, L. C. Tan 1, A. S. Sharma 1, S. F. Fung 2, Mattias Tornquist 3,Dimitris Vassiliadis 3 1. University of Maryland, College Park, MD, USA 2.Goddard Space Flight Center, NASA, Greenbelt, MD, USA 3. West Virginia University, Morgantown, WV, United States. Acknowledgement: K. Papadopoulos, M. Hudson, I. Mann 1

2 Abstract Observations by Cluster spacecraft, ground magnetometer station measuring ULF waves, and LANL, GOES spacecraft measuring energetic electron fluxes during a SSC event on September 25, [Tan et al., JGR, 2011] Evidence of relativistic electron acceleration by the compressional mode ULF waves. Energetic electron flux measured by LANL shows modulation of low energy electrons and acceleration of high energy electrons by the compressional poloidalmode electric field oscillations within 2 3 hours. Preliminary global MHD simulation through NASA/CCMC Remaining Questions and Implication for RBSP Mission 2

3 Solar Wind Condition and Geomagnetic Response during September 25, 2001 Vsw > 500 km s - 1 Recovery SSC, D st = 14 nt AE > 1000 nt

4 Spacecraft Configuration during Sept. 25, 2011 Magnetic conjunction b/w Cluster 3 & 20:21 UT, MLT= 10, L = 6.6

5 ULF Wave Excitation and Magnetospheric Relativistic Electron (MRE) Acceleration Long period of Pc5 ULF waves observed by Geotail in the solar wind, GOES satellite, and ground magnetometer Solar wind with broadband ULF wave fluctuations drive the ULF oscillations observed by GOES and on the ground. LANL MRE flux enhancements ~ 3-4 times GOES MRE flux increases 4-5 times.

6 ULF Electric Field Fluctuations observed by Cluster 3 and Geomagnetic Field Fluctuations Cluster-3 Sept. 25, 2001 Cluster 3 observed strong Pc5 ULF waves in electric field [Max Edusk (1-8 mhz) ~ 20 mvm-1 (p-p)] Ground magnetometer observation shows that ULF activity occurs largest at L =9.5 and decreases inward, Favors radial diffusion.

7 Evidence of Compressional Mode ULF Wave Excitation Compressional mode ULF wave supports harmonic oscillations across substantial radial distances inside the magnetosphere The observed ULF wave frequency spectra are of wide band with multiple peaks. During the entire solar wind driving process we see broadband ULF oscillations existing at all observation points. Within the shaded gray region, we see significant spectral strength for magnetic field amplitude at ULF wave frequency. Therefore, the observed ULF waves are compressional in nature.

8 Day night Asymmetry in Azimuthal Wave Number for Compressional Mode From ground station magnetometer observation to determine azimuthal wave mode number: m = 3.3 ± 1.2 at day side m = 0.9 ± 0.4 at night side

9 Coherent Electron & E Field Modulations Seen by CLUSTER and LANL91 on Sept 25, 2001 (20:00 24:00 UT) Conjunction of LANL 91 and Cluster 3 Cluster 3 EFW Cluster 3 RAPID/IES LANL91 Cluster-3 LANL91 Flux peak correlated with negative E 9

10 Observations from LANL Geosynchronous Satellites kev kev MeV Threshold Value of Accelerated Electron Energies Is about kev kev MeV

11 Observed Result on Threshold Value of Accelerated Electron Energies Energy Threshold ~ MeV SM33A AGU Fall Meeting 11

12 Acceleration of MREs by Drift Resonant Interaction with ULF Waves W q E ulf ds q Particle energy change E ulf ~ e imi t e i t Drift path wave electric field t wave phase in particle frame Drift path E E z Toroidal mode E Poloidal mode ds First two adiabtic invariants are conserved.. W 0 from azimuthal driftresonant interactions d dt m d W q dt 0 or m d E E Drift period Toroidal mode V d dt Poloidal mode

13 Drift Resonant Acceleration by E Perturbations (Compressional (Poloidal) Mode) W q q Y (Re) Drift period Drift period E E Drift period E X (Re) V d dt q Drift period d dt d dt dt e E d E V d dt E 0 E f (t) * cos( )g(l) 2 Eφ ~ 10 mv/m Wave period: 5 min W ~ 200 kev gain/drift period

14 Explanation of the threshold by theory of Drift Resonant Acceleration E > E0 300 kev Drift Resonant m 0 0 3m M q Condition: Degeling et al., r M

15 Global MHD Simulation Conducted real event simulation with Lyon Fedder Mobbary (LFM) 3D global MHD model through NASA/CCMC Time Dependent Inflow Boundary Conditions Start Time: 2001/09/25 18:00 End Time: 2001/09/25 23:59 Dipole tilt updated with time Ionospheric conductance model 10.7 cm Radio Flux : Coordinate System for the Output: SM Output step: every 3 min. (Improving output interval to every 30 seconds is worked on.)

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18 GOES Satellite Observation Comparison GOES 10 GOES 8

19 Science Questions for RBSP ULF Wave Excitation and distribution Solar wind driving: narrow band vs. broadband; Pdyn, IMF, and MC K H Instability: high speed stream Toroidal vs. Poloidal mode; FLR vs. Compressional Azimuthal mode number difference at dayside and nightside during SSC. Related to Alfven Velocity difference? Plasmasphere and movements of plasma pause effects MRE acceleration by ULF waves Acceleration efficiency difference by FLR vs. coimpressional model Understanding ULF wave modulation of low energy electrons and the acceleration of high energy electrons by the ULF waves. Distribution of ULF waves for effective MRE acceleration Simultaneous multi spacecraft and ground magnetometer observations are needed to understand above questions Look forward to RBSP

20 Our Experience with L* Coordinate Calculation Xi Shao, Lun C. Tan (UMD) and Shing F. Fung (NASA/GSFC) NOAA POES (NOAA 05 to NOAA14, >20 years) Energetic Proton and Electron data processed and derived McIlwain B/Bmin and L* coordinate at 1 min resolution. 4 magnetic field models used including T89, T96. Hourly solar wind and geomagnetic parameters obtained from OMNI to drive the T89 (Kp), and T96 (Pdym, Dst etc.) model. NASA Linux cluster is used. (Intensive field line tracing performed with MPI.) Products archived at NASA SPDF/CDAWeb.

21 Electron (> 300 kev) Belt Dynamics ( ) (from NOAA 5-14 POES Satellites) Inner (peak near L=1.6 ) and Outer (peak near L= 4-5) Electron Belts Variability of outer belt; Relative stable inner belt.

22 Proton (> 80 MeV) Belt Dynamics ( ) (from NOAA 5-14 POES Satellites) Only one (peak near L=1.5 ) Proton Belt. Stably Trapped for years.