Space Weather:

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Space Weather

• The Sun, Magnetosphere, Ionosphere

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Source of Space Weather / Ionospheric
Disturbances The Sun
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The Sun

• Facts (approximate values)
• 149 million kilometers away
• Diameter 1.4 million km
• Mass 2.0x1030 kg
• 4.5 billion years old
• 11 Year sunspot cycle
• Surface temp. 5,900 K.
• Rotation Period 27 days at equator

The Sun for a a couple months in 2001
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Close-up of a Sun Spot
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Local Internal Dynamics
Coronal loops on the Sun
Animation showing our present understanding
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Coronal Mass Ejections
Super prominence
EUV images of Sun with corona as observed from
SOHO
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Coronal Mass Ejection Causing the Aurora
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Magnetosphere
Other effects include satellite damage, power
outages, GPS errors, radio interruptions, etc.
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The Magnetosphere
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The Aurora
As seen in Alaska
As seen from space
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Solar Flares

• EUV
• X-RAY
• White Light

Flare
Extreme Ultraviolet (EUV)
X-ray
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Neutral Atmosphere
Daytime
Nighttime
Thermosphere
F2-Region
F2-Region
Height 100 km 200 km 300 km ?
? ?
F1-Region
E-Region
D-Region
Mesosphere
Stratosphere
Troposphere
Mt. Everest
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Formation of the Ionosphere
SUN
Free Electrons, these reflect radio waves
EUV Light
Positively Charged Ion
?
Photo-ionization
?
Neutral Atoms
A (Atom) ? A (Ion) e- (electron)
Photo-ionization occurs when Extreme Ultraviolet
(EUV) from the Sun strikes neutral atoms to
produce positively charged Ions Types of Atoms
primarily Oxygen Nitrogen Types of Molecules
O2, N2, NO
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Two Types of Recombination
Dissociation recombination, 2 steps
Neutral Atom X
Electron splits AX apart
Ion X
Single Atom A
A
AX
o
?
?
Charge Exchange X A2 ? AX A
Dissociation Recombination AX e- ? A X
Molecule A2
Radiative recombination, 1 step
A
e-
?
Radiative Recombination X e- ? A Radiated
Energy
Ion X
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Reflectivity of the Ionosphere
?
?
?
?
?
?
?
When ions are let go they oscillate in simple
harmonic motion at an Angular Frequency ? ?2 N
e2 / ?0 m N Electron Density e Charge on
electron m Mass of an electron ?0
Permittivity of free space Angular Plasma
Frequency (maximum usable frequency) fN 2? /
? fN Plasma frequency in Hertz fN2 80.5
N Substituting Atomic Constants fc ? 9 x 10-6
vNm fc Critical Frequency, Nm Electron
density
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Electron Density vs. Height

• F2 - Region
• 300 Km
• 106 Ne/cm3 (noon)
• 105 Ne/cm3 (Midnight)

Source The Ionosphere Communications,
Surveillance, and Direction Finding Leo F.
McNamara1991 ISBN 0-89464-040-2

• F1 - Region
• 200 Km
• 2.5x105 Ne/cm3 (noon)
• Absent at night

• E - Region
• 110 Km
• 1.5x105 Ne/cm3 (noon)
• 1.0x104 Ne/cm3 (Night)

• D - Region
• 90 Km, Lower following solar flare
• 1.5x104 Ne/cm3 (noon)
• Absent at Night

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Maximum UseableFrequency
The Maximum Useable Frequency (MUF) is the
largest frequency that can be reflected by the
ionosphere at vertical incidence
Source The Ionosphere Communications,
Surveillance, and Direction Finding Leo F.
McNamara1991 ISBN 0-89464-040-2
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Variability of the Ionosphere
Source The Ionosphere Communications,
Surveillance, and Direction Finding Leo F.
McNamara1991 ISBN 0-89464-040-2

• Diurnal (Thru the day)
• Seasonal (Thru the year)
• Location (Geographic Geomagnetic)
• Solar Activity (Solar Cycles Disturbances)
• Height (at different layers)