1. BARREL/Van
Allen
probes
campaign
Global-­‐scale
coherence
modula;on
of
radia;on-­‐belt
electron
loss
from
plasmaspheric
hiss:
a
further
analysis
Sadie
Tetrick1,
Aaron
Breneman
2,
and
Cynthia
CaGell2
1Augsburg
College,
MN,
2University
of
Minnesota,
MN
Summer
Sponsor:
UMN
Physics
REU
Abstract
Enhancements
of
the
Earth’s
radiaDon
belts
during
geomagneDc
storms
–
an
important
aspect
of
space
weather
–
strongly
effects
the
lifeDme
of
orbiDng
satellites
and
accuracy
of
technologies,
such
as
GPS,
that
our
society
has
come
to
rely
upon.
In
the
high-­‐density
plasma
region
that
overlaps
with
the
radiaDon
belts,
called
the
plasmasphere,
a
wave
called
hiss
plays
a
dominant
role
in
reducing
radiaDon
belt
energy
levels
back
to
nominal
levels
following
enhancements.
The
recent
Nature
arDcle
“Global-­‐scale
coherence
modulaDon
of
radiaDon-­‐belt
electron
loss
from
plasmaspheric
hiss”
(Breneman
et.
al.,
2015)
1
showed
that
changes
in
the
dynamics
of
electron
loss,
caused
by
hiss,
occur
on
Dmescales
as
short
as
one
to
twenty
minutes,
and
that
these
loss
dynamics
are
coherent
with
hiss
dynamics
on
a
global
scale.
The
cause
of
this
coherence
is
large-­‐scale
modulaDon
of
hiss
caused
by
the
propagaDon
of
ultra
low
frequency
(ULF)
1-­‐20
min
period
electromagneDc
waves,
originaDng
in
the
solar
wind.
This
discovery,
only
made
possible
through
the
analysis
of
simultaneous
satellite
(Van
Allen
Probes)
and
Balloon
Array
for
RadiaDon
Belt
RelaDvisDc
Electron
Losses
(BARREL)
datasets,
has
important
implicaDons
for
simulaDon
and
predicDon
of
the
Earth’s
radiaDon
belt
environment
and
its
effect
on
satellites.
This
project’s
goal
was
to
further
our
understanding
of
this
nearly
global-­‐scale
coherence
by
analyzing
the
enDre
balloon
dataset.
We
start
by
presenDng
observaDons
of
large
spaDal
scale
coherence
of
electron
loss
as
a
funcDon
of
MLT
and
Lshell
for
a
single
payload
combinaDon
(balloons
K
and
L)
during
a
geomagneDcally
acDve
Dme
on
January
7,
2014.
This
analysis
was
repeated
for
all
71
balloon
combinaDons.
We
observe
significant
coherence
around
noon
MLT.
This
is
likely
caused
by
solar
wind
structures
impacDng
the
bow
shock
and
then
affecDng
the
magnetosheath,
creaDng
compressional
waves
which
propagate
through
the
magnetosphere.
The
results
of
this
project
will
be
compared
to
observaDons
of
ULF
wave
populaDons
in
the
solar
wind.
Example
“coherence
event”
and
analysis
(Balloons
2K
and
2L,
Jan
7th,
2014)
Figure
5.
Example
“coherence
event”
between
balloon
payloads
2K
and
2L.
The
first
two
plots
are
BARREL
X-­‐ray
count
rate
(0
–
177.6
keV
energies)
detrended
over
30
minutes.
The
boeom
plot
is
the
coherence
spectra
for
1-­‐20
min
periods.
Only
coherence
values
>=
0.7
are
ploeed.
High
coherence
values
indicate
a
likelihood
that
the
fluctuaDons
on
the
two
balloons
represent
the
same
precipitaDon
event.
References
1A.
W.
Breneman,
A.
Halford,
R.
Millan,
M.
McCarthy,
J.
Fennell,
J.
Sample,
L.
Woodger,
G.
Hospodarsky,
J.
R.
Wygant,
C.
A.
Caeell,
J.
Goldstein,
D.
Malaspina
&
C.
A.
Kletzing
,
”
Global-­‐
scale
coherence
modulaDon
of
radiaDon-­‐belt
electron
loss
from
plasmaspheric
hiss."
Nature,
2015.
For
further
informa;on
Please
contact
Sadie
Tetrick
at:
tetrick@augsburg.edu
Acknowledgments:
I
acknowledge
the
University
of
Minnesota,
the
NaDonal
Science
FoundaDon,
and
the
BARREL
team
for
use
of
BARREL
data.
Also,
a
huge
thanks
goes
to
Aaron
Breneman
and
Cynthia
Caeell
for
their
support
and
help
with
the
research
that
I
conducted.
I
also
would
like
to
thank
the
University
of
Minnesota
for
the
use
of
their
faciliDes.
Observa;on
of
global
coherence
scale
(Jan
3rd,
2014)
Figure
3.
(a)
Spectrogram
of
hiss
observed
on
Probe
A.
(b)
RMS
hiss
amplitude
(black)
and
X-­‐ray
counts
(2I
in
red).
Despite
the
large
separaDon
in
MLT
and
L,
both
2I
and
Probe
A
observe
similar
1-­‐20
min
modulaDons
of
hiss
amplitude
and
X-­‐ray
counts
[Breneman
et
al.,
2015].
Figure
4.
Google
Earth
mapping
of
locaDon
of
balloons
2K
(leq)
and
2L(right)
on
January
7,
2014
in
AntarcDca.
9
However,
ULF
(1-­‐20
min)
fluctuaDons
of
density
and
magneDc
field
cause
global-­‐
scale
coherence
of
the
hiss
source
[Breneman
et
al.,
2015].
Thus
widely
spaced
balloon
payloads
oqen
observe
the
same
electron
loss
dynamics.
Figure
2.
LocaDon
of
BARREL
balloon
2I
and
Van
Allen
Probe
A
at
20,
21,
and
22
UT
showing
a
large
MLT
and
L
separaDon.
BARREL
consists
of
two
~6
week
campaigns
(each
with
18
balloons)
in
AntarcDca.
The
balloons
measure
bremsstrahlung
X-­‐rays
produced
by
precipitaDng
relaDvisDc
electrons
as
they
collide
with
neutrals
in
Earth's
atmosphere.
Van
Allen
probes
(labeled
A
and
B)
pass
through
the
hiss
source
region
on
field
lines
that
connect
to
the
BARREL
balloons.
Figure
1.
An
example
magneDc
conjuncDon
between
a
balloon
and
probe
A,
shown
as
the
shaded
green
area.
Electron
loss
caused
by
hiss
near
A
will
be
observed
as
enhanced
X-­‐rays
on
the
balloon.
Probe
B
is
not
in
conjuncDon
with
the
balloon,
and
a-­‐
priori
we
wouldn’t
expect
loss
near
B
to
be
observed
on
the
balloon.
100
0.01
0.1
1
10
-20
-10
0
10
20
30
2000 2100 2200hhmm
2014 Jan 03
30
Frequency(Hz)
500
DetrendedhissRMSintensity
from30-500Hz(pT)
VanAllenProbeA
3
2
1
|MLT|(hrs)MLT(hrs)L
20
16
12
6
4
2
Magneticfieldspectralpower
(pT2
/Hz)
DetrendedballoonI
X-raycounts/sec
750
500
250
0
-250
-500
-750
Balloon I
Van Allen Probe A
Slot region
Outer plasmasphere
(a)
(b)
(c)
(e)
(d)
3
2
1
0
|L|(RE
)
20:00
21:00
22:00
Conclusion
ObservaDons
of
large
spaDal
scale
coherence
of
electron
loss
have
been
presented
as
a
funcDon
of
MLT
and
L
for
the
enDre
balloon
data
set
for
clear
“coherence
events”.
We
expected
to
see
larger
coherence
at
noon
MLT
and
possibly
at
the
flanks
(occur
a
few
hours
before
and
aqer
noon)
which
may
correspond
to
Kelvin-­‐Helmholz
waves.
Our
findings
reflect
the
expected
results
for
coherence
at
noon
MLT.
This
study
will
be
conDnued
to
improve
the
quality
of
recorded
coherence
events
throughout
the
enDre
mission.
The
results
will
then
be
compared
to
ULF
wave
populaDons
in
the
solar
wind,
illuminaDng
which
wave
populaDons
are
“geoeffecDve”,
i.e.
have
a
significant
effect
on
radiaDon
belt
electron
loss
dynamics.
These
results
will
be
expanded
to
all
balloon
payload
combinaDons
to
provide
the
first
ever
survey
of
the
large
scale
coherence
of
electron
loss
in
the
magnetosphere.
“Coherence
events”
final
results
over
en;re
mission
Figures
6
and
7.
ObservaDons
of
large
spaDal
scale
coherence
of
electron
loss
as
a
funcDon
of
MLT
for
when
payload
combinaDons
are
inside
the
plasmasphere
(top
plot)
and
outside
(middle
plot)
for
balloons
2K
and
2L.
Maximum
coherence
values
(0.7
or
greater)
for
each
Dme
in
1
–
20
min.
periods
(total
of
118
coherence
values
per
Dme
sampled)
were
ploeed.
Figure
8.
Histogram
of
the
number
of
samples
at
each
MLT
value.
Figures
9
and
10.
ObservaDons
of
large
spaDal
scale
coherence
of
electron
loss
as
a
funcDon
of
L
for
when
payload
combinaDons
are
inside
the
plasmasphere
(top
plot)
and
outside
(middle
plot)
for
balloons
2K
and
2L.
Maximum
coherence
values
(0.7
or
greater)
for
each
Dme
in
1
–
20
min.
periods
(total
of
118
coherence
values
per
Dme
sampled)
were
ploeed.
Figure
11.
Histogram
of
the
number
of
samples
at
each
Lshell
value.
There
are
71
balloon
combinaDons
that
will
be
used
to
calculate
large
spaDal
scale
coherence.
Results
below
include
combinaDons
IK,
IL,
IW,
KL,
and
KW
over
the
enDre
mission.
MLT
Lshell
Number of Samples vs. MLT
Number of Samples vs. Lshell
Maximum coherence (outside plasmasphere) vs. MLT
Maximum coherence (outside plasmasphere) vs. Lshell
Maximum coherence (inside plasmasphere) vs. MLT
Maximum coherence (inside plasmasphere) vs. Lshell
MaximumCoherence
MaximumCoherence
NumberofSamples
MaximumCoherence
MaximumCoherence
NumberofSamples
KLCoherence
Logarithmic
16:00
17:00
18:00
2K
2L
20
40
60
80
100
120
140
BARREL
PeakDetector
2L
0000
Jan 07
0800 1600 0000
Jan 08
hhmm
2014
Flowpressure
(nPa)
Figure
12.
ULF
wave
populaDons
in
the
solar
wind
(black)
compared
to
BARREL
peak
detector
on
payload
2L
(red)
for
Jan.
7,
2014.
6.
7.
8.
9.
10.
11.