Post on 22-Feb-2016
description
transcript
Multipoint observations of nightside auroral activity:
the Cascades2 sounding rocket mission
K A Lynch, Dartmouth College
2009 Fall AGU SM53D-05
Dartmouth CollegeCornell UniversityNASA Wallops Flight FacilityUniversity of New Hampshire NSROCUniversity of Alaska Fairbanks PFISRKTH-StockholmPoker Flat Research RangeSRISSL/UCB
Outline• Cascades2 mission and goals• March 2009 PFRR nightside event• Three science topics
– PBI case study (Themis, PFISR, cameras, in situ observations)– Measurement of DCE shear frequencies– Deconvolving a tall-ray event
• Summary and ongoing efforts
Science objectives and questions(1) Does dynamic aurora move with respect to the background ionosphere? How much? Does it matter? Proper motion and evolution of arc structures…
(2) What is the spatial as compared to temporal variation of auroral parameters like B and E? What does this mean for theories of energy transfer? Quantifying shears…
(3) Alfven waves carry disturbances and changes down to and through the auroral zone, giving us structured and dancing aurora. They are pretty: do they matter? Are these structures significant for magnetosphere/ionosphere coupling? Do direct observations of these motions validate theories and models? Deconvolving a tall-ray event…
Bo
PFRRPFISR Toolik Kaktovic
E and B along Bo
e- across Bo
Fast e- down Bo
Image down Bo
Ground cameras
Radar
GPS position and timing
C2 array:
Event:20 March 2009 11:11:11UT apogeeNear local magnetic midnight564 km apogeeRepeating PBI event
PBI case study• First two, unaccelerated (or minimally accelerated) Maxwellians
• Different from “typical” inverted-V arcs, but discrete
• 3rd, wave accelerated, field-aligned
Shear Frequencies
Time Max North Difference
Assuming Perp Shear
Assuming Parallel Shear
602.2-602.5 .052 V/m 3.714 Hz .186 Hz
602.5-602.8 .054 V/m 5.5 Hz .19 Hz
602.8-603.3 .148 V/m 10.57 Hz .528 Hz
Time Max East Difference
Assuming Perp Shear
Assuming Parallel Shear
602.2-602.5 .077 V/m 5.5 Hz .275 Hz
602.5-602.8 .093 V/m 6.64 Hz .332 Hz
602.8-603.3 .065 V/m 4.57 Hz .232 Hz
Tall rays
Array size: 4-6 km along B ~0.5 km across BStructure: footpoint 100-200 km altitude 2 km wide/13 km/sec = 0.15sec
Other ongoing• Magnetometer deconvolution• Ion motion up and down field line• Further development of onboard camera• Plasma density measurements• Stereo camera imaging
• Multiple-point measurements separating d/dx from d/dt….3 payloads, 4 payloads, 5 payloads, …10?
www.dartmouth.edu/~aurora