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Themis Burst Modes

Themis Burst Modes. How much burst data can be transmitted What phenomena do we want to catch A burst trigger algorithm and applications. Burst data volume / orbit. Particle (high data rate) Burst data: P1, P2: ~ 60 min P3, P4, P5: ~ 70 min Wave (higher data rate) “Burst 1” data:

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Themis Burst Modes

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  1. Themis Burst Modes • How much burst data can be transmitted • What phenomena do we want to catch • A burst trigger algorithm and applications

  2. Burst data volume / orbit • Particle (high data rate) Burst data: • P1, P2: ~ 60 min • P3, P4, P5: ~ 70 min • Wave (higher data rate) “Burst 1” data: • P1: 4 min • P2: 6 min • P3, P4, P5: 7 min • Wave (highest data rate) “Burst 2” data: • P1: 1 min • P2: 2 min • P3, P4, P5: 2 min

  3. Example of data rates in burst modes: EFI • Slow survey: • Spin-averaged E field and spacecraft potential • Fast survey: • 32 samples/s E; 8 samples/s SC potential • Particle burst: • 128 samples/s E; 32 samples/s SC potential • Wave burst 1: • 1024 samples/s E; 256 samples/s SC potential • Wave burst 2: • 4096 samples/s E; 1024 samples/s SC potential

  4. Relationship between particle and wave bursts • Two options: • Wave bursts occur only within particle bursts • Wave bursts independent of particle bursts

  5. What do we want to catch? • Tail: Current disruption, BBF, PSBL • Flanks: Magnetopause/bow shock/foreshock • Dayside: • Magnetopause/boundary layer • Bow shock • Foreshock magnetic cavities and hot flow anomalies

  6. Burst trigger algorithm: Basic concept(modeled after FAST) • Onboard selection of best data intervals during each orbit • Each data segment has a quality factor Q • Q computed from combination of particles and fields data Q = Q1 Density + Q2 Velocity + Q3 BRMS + Q4 E +…

  7. An example of burst trigger algorithm • To catch gradients such as the crossings of PSBL, MP, bow shock, diamagnetic cavities, onset of BBF, CD: Q = Q1 (N-N_smooth)2 + Q2 (V-V_smooth)2 +… where smooth i+1= [smooth i (2M-1) + data i] / 2M

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