Theory and simulation predict:
-
Upload
tiger-graves -
Category
Documents
-
view
27 -
download
4
description
Transcript of Theory and simulation predict:
Cusp Radiation Source: A Challenge for Theory and Simulation
Jiasheng Chen, Theodore A. Fritz, Katherine E. Whitaker,Forrest S. Mozer, and Robert B. Sheldon
In cooperation with:J. F. Fennell, M. Klida, K. Kudela, V. N. Lutsenko, J. Niehof, J. S. Pickett, J. Roeder, C. T. Russell,
G. L. Siscoe, W. N. Spjeldvik, and K. Trattner
Theory and simulation predict:
• Cusp is a precipitation region for particles;
• A positive IMF By would move the dayside northern cusp into post-noon;
• A negative IMF By would move the dayside northern cusp into pre-noon (e.g., Cowley et al., JGR, 96, 5557, 1991).
Cusp Diamagnetic Cavities (CDC): |B|
CDC at 9:30 MLT
(pre-noon)
with turbulence.
Cusp energetic Particle (CEP)
Cusp
CDC at 14-23 UT on 5/13/99 with a size of ~ 6 Re.
Solar wind conditions for the 5/13/99 CDC
Since By < 0,a CDC at pre-noon
was expected.
By < 0
Other CDC observations under different solar wind conditions:
1. Normal solar wind speed, vsw = 450 km/s
2. Fast solar wind stream, vsw = 900 km/s
3. Slow solar wind flow, vsw = 380 km/s (two examples presented)
1. Normal solar wind speed, vsw=450 km/s
4/22/99
(Fritz et al., JGR, 108, A1, 1028, 2003)
Pre-noon
Post-noon
By>0, <Dst>=1.6 nT, CDC at pre-noon; unexpected
By>0
CDC at10:30 MLT
2. Fast solar wind stream, vsw=900 km/s
6/28/99
Cusp energetic He++
Cusp energetic O+
By>0, <Dst>=14.7 nT, CDC at 7MLT; unexpected
CDC
+ +
3a. Slow solar wind flow, vsw=380 km/s4/25/99
POLAR,4/25/99
By>0, <Dst>=5.5 nT, CDC at pre-noon; unexpected
By>0
CDC at10:20 MLT
3b. Slow solar wind flow, vsw=380 km/s
15 UT
19 UT
15 UT
19 UT
By>0, <Dst>=-82 nT, CDC at 8:30 MLT; unexpected
By>0
CDC
10/30/78
ISEE-1
ISEE-3
IMF
Energetic Charged Particles in CDC
CEP electron
CEP proton
CDC
CEP Energy Spectrum
CEP vs. Outer Radiation Belt ParticlesProton phase space density
He++ & O+ phase space densities: Cusp Radiation Source
CEP and Fields
1. CEP flux increase with E-field increase and B-field Decrease.
2. Emax = 50 mV/m
Blow up cusp E-field near peak fluctuation
Showing some polarizationWaves at different Frequencies.
Left-hand polarization
Left-hand polarization
Summary• CDC is a large radiation region, and CEP is a new
radiation source.
• Under different solar wind and geomagnetic conditions, CDCs have been observed at pre-noon in the northern hemisphere when IMF By >0 (duskward).
• These observations are unexpected by the existing models and MHD simulations and provide a new challenge for the current theory and simulations.
• Cusp ions can be energized by both resonant and stochastic acceleration mechanisms.