R. H. W. Friedel1 ; S.K. Morley1 ; E. Spanswick1,2; T. E. Cayton1; E. Noveroske1
[email protected]
(1- LANL, 2-U. Calgary)
BDD-I
ns10
10/1984-11/1992
BDD-I
ns18
01/1990- 12/1995
BDD-II
ns24
11/1991–11/2000
BDD-II
ns28
05/1992- 09/1996
BDD-II
ns39
07/1993–10/2005
BDD-II
ns33
04/1996–01/2007
BDD-II
ns41
12/2000 – today
BDD-IIR
ns54
02/2001 – today
CXD
ns56
02/2003 – today
CXD
ns60
07/2004 – today
CXD
ns59
04/2004 – today
CXD
ns61
11/2004 – today
CXD
ns53
10/2005 – today
CXD
ns58
12/2006 – today
CXD
ns55
10/2007 - today
CXD
ns57
01/2008 – today
CXD
100/200 keV – 10 MeV electrons
ns48
03/2008 – today
BDD-IIR
5/9 MeV – 60 MeV protons



Stream Interface
4 RE circular, 50o inclination


Reversal in azimuthal flow velocity.
Extremely high proton density of ~60cm-3
Bz switches polarity across interface and reaches
-15nT, remains variable afterwards
Dst reaches +34nT during density enhancement
and then falls to -21nT (very small storm)
Kp 4-5, high convection
Riometer absorption maps from 21 stations
for period around 7 May 2007
L- and L*-sorted CXD data from 7 GPS Satellites
for period around 7 May 2007

Combined CXD Data
07/1983 02/1984
[A Rapid, global and prolonged electron radiation belt dropout observed with the Global Positioning System Constellation, S. K.
Morley, R. H. W. Friedel, T.E Cayton and E. Noveroske, GRL submitted, December 2009]
Stream Interface from high-resolution OMNI
data for period around 7 May 2007
Los Alamos energetic
electron data from the
GPS constellation
ns08

Resolution 0.1 in L and 1hr in time
No adjustments in raw count data needed



21 Stations (10 Canadian, 7 Finnish, 4 Antarctic)
Increased absorption is pre noon during the time
frame of the GPS dropout (middle left panel).
Riometers provide no information on the
precipitating energy flux (it is an integrated effect
above 30keV) but they identify the spatial extent
of the precipitation region and also its lifetime.
CXD instruments highly
inter-calibrated – can be
combined in L, time
with NO adjustments.
L-value
GPS Data Density
FOR A DETAILED SURVEY OF THE LOSS RESPONSE OF THE ELECTRON RADIATION BELT IN RESPONSE TO
HIGH-SPEED SOLAR WIND STREAMS, PLEASE SEE STEVE MORLEY’S POSTER (# SM11A-1571 ON MONDAY)
We present a case study of a very fast energetic electron dropout observed in the electron radiation belts between
1530 and 1730 UTC on 7 May 2007. The rapid loss occurred over the range L*>4 and across all observed energies
above 230keV, over timescales of ~2hrs. The timescale for this event is incompatible with currently accepted loss
mechanisms (magnetopause shadowing/outward diffusion or EMIC wave interaction). Initial ground-based
precipitation measurements from riometers indicate a strong local time dependence (pre noon) that is statistically
consistent with the occurrence location of high-latitude chorus.
Combined Riometer Data
A Detailed Look at Energetic Electron Dynamics in Response to Solar
Wind Drivers at GPS Orbit
MLT
Yields unprecedented
temporal and spatial
coverage in region
L
= 4-10:
1hr in time
0.1 in L
One day – April 1, 2008
BDD Block IIR
CXD Block IIR
At and beyond geosynchronous orbit electron fluxes drop off slowly and roughly track the motion of the magnetopause - consistent with
outward diffusion (Fig. 2, Panel 1). In the bottom three panels of Fig. 2 the edge of the sorted data marks the last closed drift shell for T89.
Similarity between L and L* sorted data show that the Dst effect for this event is small/absent. Dropout was coincident with arrival of stream
interface. Energies below ~410 keV recover strongly (plasmasheet source) while higher energies lack a recovery. Model plasmapause position
indicates formation of a drainage plume, favoring EMIC loss mechanism yet this is unlikely as resonant energies would need to fall to ~230410 keV. Outward radial diffusion is further an unlikely candidate since transport timescales at L=4 are of the order of days.
Riometer data however do indicate a significant absorption event in the 6-hour window bracketing the GPS loss even, in a MLT location
consistent with statistical maps of high latitude chorus occurrence, indicating that precipitation by these waves could be a possibility.
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
UNCLASS IFIED
Figure 3: Averaged riometer data surrounding the May 7th
2007 event. Each panel is a 6 hour average of data
binned into 30 minute MLT and 5 degree latitude bins.
To our knowledge this is the fastest and most globally observed dropout reported to
date (thanks to the unprecedented CXD data density).
 Losses beyond geosynchronous are well correlated with magnetopause motion.
 Inside GEO unrealistically large radial diffusion would be needed for losses to the
magnetopause - riometer data shows possible precipitation loss by high latitude
chorus.
 However, current estimates of loss timescales dues to wave-particle interaction (hiss,
chorus, EMIC or combination) are too low.

Acknowledgements: The authors thank Geoff Reeves (LANL) and Mike Henderson (LANL) for helpful discussions. Figures 1 and
2 were generated using the new SpacePy library in Python written by Steve Morley (under development at ISR-1, LANL).
Conclusions
BDD
Block II,IIA
Figure 1: Solar wind and planetary index data for the interval
of 5 May to 10 May 2007. Panel 1 (top) shows KP, panel 2
Dst, panel 3 the plasma bulk speed, panel 4 the solar wind
number density and panel 5 the interplanetary magnetic
field z-component.
Figure 2: Panel 1 (top) shows (0.77-1.25 MeV) electrons sorted
by T89 L; overplotted in red is the Shue et al. [1977]
magnetopause standoff distance; overplotted in black is the
Moldwin et al. [2002] plasmapause model. Lower three
panels are 230-410 keV, 0.77-1.25 meV and 1.7-2.2 MeV
energetic electrons sorted by L* (T89).