Transcript LENAs as seen from IMAGE - Southwest Research Institute

Solar Wind-Magnetosphere Interactions
via Low Energy Neutral Atom Imaging
•
•
•
•
•
T E Moore[1], M R Collier[1], M-C Fok[1], S A Fuselier[2], D. G. Simpson[1], G. R. Wilson[3], M. O. Chandler[4]
1. NASA’s Goddard Space Flight Center, Interplanetary Physics Branch, Code 692, Greenbelt, MD 20771
2. Lockheed Martin Advanced Technology Center, Dept. H1-11, Bldg. 255, Palo Alto, CA 94304
3. Mission Research Corporation, 589 W. Hollis St., Suite 201, Nashua, NH 03062
4. National Space Science and Technology Center, NASA MSFC SD50, Huntsville AL 35805
•
•
•
LENA was motivated by need for time-resolved ionospheric outflow observations.
Also responds to neutral atoms with energies up to a few keV (from sputtering).
As a result, we have been able to:
-
•
Show that ionospheric outflow responds to solar wind dynamic pressure variations.
Observe that the response is prompt.
Infer a heating source below 1000 km altitude for the larger flux events.
Use neutral atom emissions to reveal the magnetosheath, with cusp-related structures.
Infer dayside structure in the geocorona. .
Measured the annual variation of the neutral solar wind.
Probe the interstellar gas and dust in the inner solar system.
Directly observe the interstellar neutral atom focusing cone at 1 AU.
LENA imaging has thus proven to be a promising new tool for studying the
interplanetary medium and its interaction with the magnetosphere, even from inside the
magnetosphere.
2001/02/08
T E Moore - SW Interactions via LENA
1
Low Energy Neutral Atoms (LENA)
CME/Storm Onset and Response
Hr Before Hr After Snap
•
•
Perigee
Solar Wind LENA
increase marks CME
arrival at 0915 hrs.
Earth sector LENA
respond within travel
time of 35eV O0.
2001/02/08
T E Moore - SW Interactions via LENA
2
Comparison with Ion Outflows
LENA H/O/Total Images
•
TIDE Polar Ion Outflows
Neutral Fraction
vs
Source Altitude
Preliminary comparisons:
-
Some spatial correspondence (day - night here)
Flux comparison indicates low altitude source region
Best correspondence w/ auroral oval from transverse views (not shown)
Posters AGUsm01: SM72A-14 (Coffey et al.), -15(Wilson et al.)
2001/02/08
T E Moore - SW Interactions via LENA
3
Simulated LENA Emissions
Auroral zone emissions
2001/02/08
Uniform polar emissions
T E Moore - SW Interactions via LENA
4
Sources of Indirect SW-LENA
Collier
et al.
Nov JGR
p.24,893
2001/02/08
T E Moore - SW Interactions via LENA
5
Solar LENA flux profile
Strong similarity to
ram pressure profile
observed at WIND.
Tracking observed at
some time scales, not
others.
2001/02/08
T E Moore - SW Interactions via LENA
6
Simulation of Indirect LENAs
• Simulations performed by M.-C. Fok using MHD magnetosheath.
• Analogous to ring current ENA simulations, using an CCMC
(BatsRUS) MHD model of the magnetosheath, and looking out.
• LOS integration from 8 to 50 RE, excepting antisunward 90° cone.
Images collapsed in polar angle, for IMAGE.
• No true solar LENAs assumed to arrive in solar wind here.
200 eV
Dawn-Dusk Orbit
Noon-Midnight Orbit
2001/02/08
4000 eV
Dawn-Dusk Orbit
Noon-Midnight Orbit
T E Moore - SW Interactions via LENA
7
• Solar wind flux or
dynamic pressure
increases produce a
big reaction in LENA.
• A brightening is seen
especially between
the sun pulse and the
Earth (white line
here).
• Is this the expected
relation between
solar wind intensity
and ENA emission
from this region?
2001/02/08
T E Moore - SW Interactions via LENA
8
We expect a very strong dependence
because so many factors are affected
by solar wind flux (and Pd).
2001/02/08
T E Moore - SW Interactions via LENA
9
Simulation of Magnetosheath CE
• CCMC Simulations based on
BatsRUS Code
• LOS integration from IMAGE
spacecraft by M-C Fok.
• Consider periods of
enhanced Pd solar wind for
compressed magnetopause.
• Remote sensing of cusp and
cleft possible with sufficient
sensitivity and-or Pd.
2001/02/08
T E Moore - SW Interactions via LENA
10
2001/02/08
T E Moore - SW Interactions via LENA
11
Seeing Magnetosheath Structure
• LENA spin modulation near
the peak of the 31 March
2001 event at about 0450UT:
04:50:08-04:54:16
• CCMC (BatsRUS) MHD
simulation of the 31 March
2001 event, showing
magnetosheath density
distribution along LENA lines
of sight at about 0450 UT
Azimuthal Sector No. [8° sectors]
45
40
35
30
Sun
25
20
15
Earth
10
5
0
0
50
100
150
200
250
300
350
LENA bkg adjusted H counts
2001/02/08
T E Moore - SW Interactions via LENA
12
Remote-Sensing the Magnetosheath
Simulations indicate features
of the magnetosheath should
be visible and are visible from
inside the magnetosphere.
Sun
MS
2001/02/08
T E Moore - SW Interactions via LENA
13
Evidence for Geocoronal Erosion?
Data: LENA background adjusted flux > 30 eV
Deflectors
5-50 RE
5-12 RE
2001/02/08
T E Moore - SW Interactions via LENA
14
Short term, storm
variations reflect
solar wind intensity
variations, CMEs,
and distribution of
the geocorona.
Observation: Annual Variation of Solar Wind ENA
100.0
Long term, seasonal variations reflect
solar system distribution of neutral gas
(interstellar and other sources)
2001/02/08
LENA H rate [counts/s]
(sun sector apogee)
Mexi can Auror a
Stor m
r adiation s tor m
10.0
1.0
IOC level (x4)
nominal ops level
ppsp l evel (x0. 33)
ppsp stepping (x0.33)
ppsp l evel (x0. 33)
Tsur utani et al ., 1994 events
0.1
0
T E Moore - SW Interactions via LENA
100
200
day of year 2000/2001
300
15
sun_pulse_ltt_09.plt
SW ENA Model of Bzowski et al.
Icarus 1996
2001/02/08
T E Moore - SW Interactions via LENA
16
Limit on Inner Solar System Dust
Collier et al., AGU SM2001
2001/02/08
T E Moore - SW Interactions via LENA
17
Predicted Direct ISN Observations
Fuselier, 1997
2001/02/08
T E Moore - SW Interactions via LENA
18
Direct ISNs, Interpreted?
2001/02/08
T E Moore - SW Interactions via LENA
19
3D Interstellar Neutral Trajectories
2001/02/08
T E Moore - SW Interactions via LENA
20
ISN Flux
12/1
1/1
2/1
3/1
12/1
2001/02/08
1/1
2/1
T E Moore - SW Interactions via LENA
3/1
21
Conclusions
• We have been able to:
- Validate earlier statistical inferences that ionospheric heating
responds to solar wind dynamic pressure variations.
- Observe that the response is prompt, as fast as
hydromagnetic wave propagation speeds.
- Infer that the heating source must lie lower than 1000 km
altitude for the larger flux events.
- Use neutral atom emissions to reveal the magnetosheath,
with cusp-related structures.
- Infer dayside structure in the geocorona, owing to solar wind
erosion by charge exchange.
- Measure the annual variation of the neutral solar wind.
- Interpret annual variation in terms of interstellar neutral gas
and dust in the inner solar system.
- Directly observe the interstellar neutral atom focusing cone at
1 AU.
2001/02/08
T E Moore - SW Interactions via LENA
22
Comparison with Dayside Aurora
• See Fuselier et al.,
GRL 15 March 2001.
• Before/After images
of dayside aurora.
• IMF Bz generally
Northward.
• Similar in many ways
to 24 Sept 98 CME,
with resultant
Ionospheric Mass
Ejection [Moore et
al., GRL, 1999]
2001/02/08
8 June 2000 CME Arrival
T E Moore - SW Interactions via LENA
23
Direct ISNs, Observed
2001/02/08
T E Moore - SW Interactions via LENA
24
SWLENA: A Heliospheric Gas and Dust Probe
• Three charge
exchange media:
– Heliosphericdust
generates const ant
background gas
– Interstellar neutral
s
enter from apex, lost
by P I and CE.
– GeocoronalH near
Earth
2001/02/08
• Three Response Time
Scales:
– Minimum fluxis due
to dust-generated gas
– Annual variation
reflects ISN anisot ropy
– Solar wind response
reflects geocoronalgas
interaction
T E Moore - SW Interactions via LENA
25