Geomagnetic Storms

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Geomagnetic Storms
Vania K. Jordanova Los Alamos National
Laboratory, Space Science and Applications Los
Alamos, NM 87545, USA

• Solar and interplanetary origin of magnetic
  storms
• What is a geomagnetic storm?
• Sources, acceleration, and losses of ring
  current ions
• Modeling the evolution of the terrestrial
  ring current using multi-satellite data

U N C L A S S I F I E D
LASSO Seminar, 22 July 2008
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Sun-Earth Connection
Earth
Varying output Radiation
Solar Wind Energetic Particles Driven by 11
Year Solar Cycle
Variable Star
Solar Flares
Geomagnetic Storms
98 00 02 04 06
08 10 12 14 16
18
Year
Questions How and why does the Sun vary?
How does the Earth respond? What are the
impacts on life and society?
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The Shape of the Magnetosphere
Art by K. Endo, Nikkei Science Inc., Japan

• The Earths magnetic field is dipolar only
  close to the surface
• Solar plasma streams radially into space at
  high speed
• The solar wind compresses the sunward side of
  the magnetosphere and drags out the nightside
  magnetosphere

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First Discovery by Explorer I, 1958
VAN ALLEN RADIATION BELTS
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SPIRALING
SPIRALING AND BOUNCING FROM POLE TO POLE
INCOMING CHARGED PARTICLES (ELECTRONS PROTONS)
SPIRALING, BOUNCING AND DRIFTING FROM LINE TO LINE

MOTION OF INDIVIDUAL CHARGED PARTICLES
AROUND EARTHS MAGNETIC FIELD LINES
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Regions of the Magnetosphere
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Geomagnetic Storm Ring Current Evolution
Sudden Commencement
main recovery phase

• Composition e-, H, He, O, C, N, He
• Energy Range 1 keV lt E lt 300 keV
• Location 2 lt L lt 8
• Energy Density 10 - 1000 keV/cm3

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Dynamics of Geomagnetic Storms
NOAA Data, 21-24 October, 2001

• Variations lasting several days
• Intensification of the ring current
• Electron acceleration to MeV energies
• gt Spacecraft anomalies
• Key science questions
• Where do these particles come from?
• What causes particle acceleration and loss?
• What determines the effectiveness of the storm?

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Dynamics of Magnetospheric Substorms

• Short term variation minutes
• Injection of hot plasma
• Auroral brightening
• gt Spacecraft charging
• Key science questions
• What causes substorms to occur?
• Where are the substorms initiated?
• How are the particles energized?
• What lights up the sky?

(min)
(min)
Spectacular Auroras at Earth
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Solar - Interplanetary - Magnetosphere Coupling

• Flow of plasma within the magnetosphere
  (convection)

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Magnetospheric Electric Field

• Volland-Stern semiempirical model
• convection potential
• corotation potential
• Drift velocity
• Magnetic field model
• Gradient-Curvature velocity

Lyons and Williams, 1984
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Sources of Ring Current Ions

• Solar wind
• Ionosphere

Chappell et al., 1987
max H solar min quiet conditions max O
solar max active conditions Total ionospheric
flux 10 26 ions/s gt comparable to solar wind
source
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Ring Current Loss Processes
Energetic
Ring Current Belt (1-300 keV) Density Isocontours

Neutral
Plasmapause
Precipitation
Lower Density Cold
Plasmaspheric Plasma
(Dusk Bulge Region)
Dawn
Charge
Exchange
( L4)
Dusk
( L6 )
( L8 )
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NASA IMAGE MissionImager for Magnetopause-to-Aur
ora Global Exploration
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IMAGE/HENA Proton Flux (27-39 keV) April 22

• 05 UT

08 UT
16 UT
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Ring Current Loss Processes
Energetic
Ring Current Belt (1-300 keV) Density Isocontours

Neutral
Plasmapause
Precipitation
Lower Density Cold
Plasmaspheric Plasma
(Dusk Bulge Region)
Dawn
Charge
Exchange
Coulomb
Conjugate
Collisions
SAR Arcs
Between
Ring Currents
( L4)
and
Dusk
Thermals
Anisotropic
(Shaded Area)
Energetic
Ion Precipitation
( L6 )
( L8 )
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IMAGE Mission Seeing the invisible

• Simultaneous global images of the plasmasphere
  and the ring current during the storm main phase
  (Dst -133 nT) on May 24, 2000 Burch et al.,
  2001

EUV image of the plasmasphere at 0633 UT from
above the north pole
Superimposed HENA image of 39-60 keV fluxes
showing significant ion precipitation near dusk
The low altitude ENA fluxes peak near dusk and
overlap the plasmapause Burch et al., 2001
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Ring Current Loss Processes
Energetic
Ring Current Belt (1-300 keV) Density Isocontours

Neutral
Plasmapause
Precipitation
Lower Density Cold
Plasmaspheric Plasma
(Dusk Bulge Region)
Dawn
Ion
Cyclotron
Charge
Waves
Exchange
Coulomb
Conjugate
Collisions
SAR Arcs
Between
Ring Currents
( L4)
and
Dusk
Thermals
Anisotropic
(Shaded Area)
Energetic
Ion Precipitation
( L6 )
( L8 )
Wave Scattering
of Ring Current Ions
Isotropic Energetic Ion
Precipitation
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EMIC Waves Observations
EMIC waves recorded using DE1 magnetometer
within 30 MLAT during the 10-year
mission lifetime Erlandson and Ukhorskiy, 2001

• Freja data, April 2-8, 1993 storm, Dst-170 nT,
  Kp8-
• Wave amplitudes decreased with storm evolution
• Waves below O gyrofrequency observed near Dst
  minimum Braysy et al., 1998

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IMAGE FUV Data Detached Proton Arcs
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Theoretical Approaches for Modeling Inner
Magnetosphere Dynamics

• Single particle motion - describes the motion of
  a particle under the influence of external
  electric and magnetic fields
• - trajectory tracing studies
• - mapping of distribution function
• Magnetohydrodynamics and Multi-Fluid theory - the
  plasma is treated as conducting fluids with
  macroscopic variables, allow self-consistent
  coupling of the magnetosphere and ionosphere
• Kinetic theory - adopts a statistical approach
  and looks at the development of the distribution
  function for a system of particles

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Ring Current - Atmosphere Interactions Model
RAM --- Jordanova et al. 1996 2001
Calculates the distribution function of ring
current H, O, and He ions and thermal plasma
from the fundamental kinetic equations
plasma sheet - LANL
sources
initial distribution - Polar
charge exchange
Ring current model
Coulomb collisions
losses
E100 eV 400 keV PA 0º 90º dipole (L
2.0-6.5) all MLT
atmospheric loss
w-p interactions
escape from MP
transport
convection
Plasmasphere model
ionosphere/thermosphere
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Storm-time Ring Current Simulations
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Model Drift of Ring Current Particles
Initial E0.2 keV at L10
Initial E0.4 keV at L10 The 90 deg pitch
angle particle tracings. Asteriks are
plotted at 1 hour
steps within 20 hours

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Plasmasphere Model
Equatorial plasmaspheric electron density Ion
composition 77 H, 20 He, 3 O
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WIND Data Geomagnetic Indices

• CME passage at Earth
• Moderate geomagnetic storm on 10 January,
  1997,
• Dst-83 nT Kp6
• Abundance of data available from ISTP
  spacecraft

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Geosynchronous LANL Data 10 January 1997

• Electron and ion fluxes (10 eV to 40 keV) from
  MPA on geosynchronous LANL satellites
• Hot ion fluxes are used to provide the
  time-dependent nightside boundary conditions of
  the model
• MPA cold ion observations indicated the
  traversal of a dayside plasmaspheric plume in the
  afternoon LT sectors

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Convection Electric Field Comparison with
POLAR/EFI Data

• Enhanced electric fields are measured below L5
  during the main phase of the storm on the
  duskside (MLT?18)
• Such electric fields appear about an hour or
  more before a strong ring current forms
• Much smaller electric fields at larger L shells
  (L5-8) and on the dawnside (MLT?6)
• Good agreement with the MACEP model we developed
  on the basis of the ionospheric AMIE Richmond,
  1992 model and a penetration electric field
  Ridley and Liemohn, 2002

Boonsiriseth et al., 2001
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Millstone Hill Radar Observations Enhanced
Electron Temperature, January 10, 1997
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Model Results Dst Index, Jan 10, 1997
IMF dependent

• Comparison of
• Kp-dependent Volland-Stern model
• IMF-dependent model
• gt An IMF-dependent model like MACEP predicts
  larger electric field, which results in larger
  injection rate and stronger ring current buildup

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Ring Current Asymmetry
A very asymmetric ring current distribution
during the main phase of the storm due to freshly
injected particles on open drift paths The
total energy density peaks near midnight using
MACEP, near dusk using Volland-Stern Ring
current ions penetrate to lower L shells and gain
larger energy in MACEP than in Volland-Stern
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Effects of Collisional Losses
Comparison of model results with POLAR data
Larger effect on - postnoon spectra - low
L shells - high magnetic latitudes - slowly
drifting 1-30 keV ions
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Heating of Plasmaspheric Electrons
Maximum heating occurs initially on the
nightside at L3.5 just inside the plasmapause
It moves earthward to L2.75 with storm
development gt in agreement with Millstone Hill
radar observations, indicating the predominant
role of ring current H as a magnetospheric heat
source
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IMAGE FUV Data Detached Arcs

• Images from the proton imaging channel (SI-12) of
  the Far Ultraviolet Imager (FUV) at 12 minute
  intervals beginning at 2102 UT on January 23.
• Dashed contours indicate geomagnetic latitudes of
  25, 50, 75
• direction to the Sun
• detached arc
• Characteristics of the events subauroral arcs
  separated from the main oval and extending over
  several hours local time in the afternoon sector

Immel et al., 2002
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Observations of Detached Subauroral Proton Arcs

• IMAGE/FUV data on 23 January 2001 images in
  geographical coordinates and mapped into
  geomagnetic coordinates. The proton arc was
  observed from 23 UT until 24 UT after which
  the spacecraft began its perigee pass
• Energy spectrograms of precipitating electrons
  and ions measured by the FAST electrostatic
  analyzer (energies lt30 keV) conjugate to the
  IMAGE observations
• Three peaks in the ion energy flux, no peaks in
  the electron energy flux equatorward of ?-69.5
• Consistent with DMSP observations of 3-30 keV
  proton precipitation above the detached arc and
  lt10 keV protons over the main oval
• ? What causes this proton precipitation?

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Subauroral Proton Arcs Observations and Modeling
RAM simulations June 17-18, 2001
Hours after 00 UT, June 17, 2001
Direct link between a subauroral arc (MLT13 to
16.5) and a global observations of a
plasmaspheric plume by IMAGE Spasojevic et al.,
2004
EMIC waves are excited in the afternoon MLT
sector causing intense ion precipitation
Jordanova et al., 2007
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Space Weather How Does Solar VariabilityAffect
Life and Society?
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Conclusions

• Geomagnetic storms are among the most adverse
  space weather phenomena. To provide their
  accurate specification and forecasting
• Develop an advanced understanding of the
  fundamental physical processes of the space
  environment from the Sun to Earth
• Integrate this understanding into physics-based
  models
• solar wind
• Earths magnetosphere
• solar wind-magnetosphere coupling
• Physics-Based Models of the Space Environment at
  LANL
• Building on more than 40 years of space science
  heritage at the Laboratory
• unique scientific expertise
• exceptional computational capabilities
• unique data to constrain and validate the models
• Support national security mission to maximize
  the safety of civilian and military satellites