SunEarth System Overview

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Sun-Earth System Overview

• Frank Eparvier
• eparvier_at_colorado.edu
• 303-492-4546

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Who am I?

• Dr. Frank Eparvier
• Research Scientist _at_ LASP
• Training in Aeronomy
• Aeronomy study of how energy inputs drive the
  physics and chemistry a planetary atmosphere
• Experimentalist I like to measure things
• Experiment is the test of all knowledge.
• Currently work with instruments that measure the
  solar photonic output of aeronomical importance
• Co-I on TIMED-SEE
• Co-I on SDO-EVE
• PI on GOES-R EXIS

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Why do We on Earth Care about the Sun?

• The Sun directly or indirectly provides nearly
  all of the energy to the Earth system.
• Photons (light of all wavelengths)
• Plasmas (charged particles and magnetic fields)
• Variability in the solar output drives
  variability in the Earth system.
• How the Earth system reacts to solar
  variability depends on the complicated,
  interconnected mechanisms involved in the
  Sun-Earth system.

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The Sun Side of the Sun-Earth System
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The Earth Side of the Sun-Earth System
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Statistics of the Sun

• Radius 696,000 km ? 109 REarth
• Volume ? 1,300,000 VEarth
• Mass 1.99x1030 kg ? 333,000 MEarth
• Composition

Much of this is in the form of ionized atoms
plasma
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Solar Energy Source

• Pressure at center 250 billion atmospheres
• Temperature at center 15 million Kelvin
• ? Conditions suitable for Nuclear Fusion
• Protons squish together produce
• Helium nucleus
• Subatomic particles
• Light (energy!)
• Release of nuclear binding energy during fusion
  is the Suns internal energy source.

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Energy Output of the Sun

• Measure all photonic energy coming from the Sun
  at all wavelengths
• Total Solar Irradiance 1361 Watt/m2 at 1 AU
• Integrate over entire sphere around Sun
• Power 3.8x1026 Watts
• (Thats a bright light bulb!)

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Energy Flow and Layers of the Sun

• Interior of Sun
• Core Where fusion occurs, 15 million K
• Radiative Zone Energy carried outward slowly
  (200,000 yrs) by photons through a very thick
  region of H He, T5 million K
• Convective Zone Energy carried outward via
  convection (hot plasma rises, reaches surface,
  radiatively cools, then sinks again), T1 million
  K

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Energy Flow and Layers of the Sun (2)

• Atmosphere of Sun
• Photosphere visible surface of Sun, point
  where gases go from being optically thick
  (opaque) to optically thin (transparent), T5700
  K
• Chromosphere bottom layer of atmosphere,
  visible as pink layer of hydrogen during total
  solar eclipses, T10,000 K
• Transition Region narrow (100-1000 km) layer
  between chromosphere and corona where
  temperatures rise rapidly T10,000 K - 1 million
  K
• Corona top of solar atmosphere heated to
  extremes by complex (and not fully understood)
  magnetic means, T 2 million K
• Solar Wind extension of corona into
  interplanetary space, mostly protons and
  electrons streaming out on Suns magnetic field
  at speeds of 400-1000 km/s, T200,000 K at 1 AU

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Differential Rotation of Sun

• Core and Radiative Zone rotate rigidly.
• Outer layers of Sun rotate differentially.

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Looking at the Sun

• Different wavelengths show us a different Sun.
• Features that are dark at one wavelength are
  bright at other wavelengths.

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Granules

• Granules Convection cells on photosphere, size
  1000 km ( size of Texas)

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Sunspots

• Sunspots Magnetically disturbed regions cooler
  than surrounding areas (4000 - 5000 K) of
  photosphere (?darker), usually come in pairs (N
  and S magnetic polarity), size 1500-50,000 km,
  can last for months

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Magnetic Origin of Sunspots
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Prominences

• Prominences Filaments Long-lasting (hours or
  days) condensations of gases held above the
  surface by erupting sections of magnetic field

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Flares

• Flares short duration (minutes to hours) bursts
  of hot material out of surface, very bright at
  all wavelengths

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Coronal Holes

• Coronal Holes areas of open magnetic field
  allowing plasma to stream out into solar wind

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Coronal Mass Ejections

• CMEs large blobs of plasma (hot ionized gases
  enclosed in bubbles of magnetic field) that blow
  off the Sun and travel out through the solar
  system

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Solar Wind and IMF

• Solar Wind Charged particles streaming out from
  Sun
• Interplanetary Magnetic Field (IMF) Solar
  magnetic field at distances of the planets

IMF is twisted into ballerina skirt shape by
solar rotation.
Solar wind flows out along open magnetic field
lines.
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Photon Output of the Sun
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Timescales of Solar Variability
Solar Cycle - months to years Evolution of solar
dynamo with 22-year magnetic cycle, 11-year
intensity (sunspot) cycle
Solar Rotation - days to months Beacon effect of
active regions rotating with the Sun (27-days)
Flares - seconds to hours Related to solar solar
eruptive events due to the interaction of
magnetic fields on Sun
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The Solar Cycle

• 11-year Sunspot or Solar Activity Cycle

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Solar Cycle
Sunspots
Magnetogram
Soft X-Rays
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Source of Solar Cycle

• 11-year sunspot cycle is really a 22-year
  magnetic cycle (magnetic field reverses every 11
  years).

Differential rotation of Sun causes knotting of
originally dipole-like magnetic field. Solar
Maximum Knotting peaks 5.5 years after clean
start. Solar activity and output peaks. Solar
Minimum Sun cleans itself up over next 5.5 years
into a quiet, but reversed dipole field.
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The Solar Constant
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TSI Variability

• Overall, TSI increases during solar max, but
  sunspots can block sunlight, making TSI drop.

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The Earth System

• Earth intrinsically has an atmosphere and a
  magnetic field.
• Place this into the constantly changing space
  environment created by the Sun and you get
  complex responses.

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Earths Atmosphere Composition Density
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Solar Photons and the Atmosphere
The Solar Spectrum at top of atmosphere (similar
to 5800 K blackbody spectrum)
The Solar Spectrum at the surface of the Earth
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Absorption in Atmosphere
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The Atmosphere and TSI
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Typical Atmospheric Temperature Profile
EUV, FUV, Soft X-rays absorption and ionization
heating
Primarily IR radiating to space cooling, Some FUV
absorption heating
MUV Sunlight absorption by O3 heating
Visible, NIR, NUV absoprtion of sunlight by air
and surface, surface heats from below
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EUV Ionizes the Upper Atmosphere
Solar Minimum
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EUV Ionizes the Upper Atmosphere
Solar Maximum
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Ionosphere Reaction to Solar Variability
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Ionosphere in Itself is Complex System
Ionospheric Electrodynamics
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Earth Has a Magnetic Field
Credit Tsurutani, 2005
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Earth Reacting to a CME
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The Aurora
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Space Weather Effects on Humanity
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Summary
The Sun-Earth System is Complex But understandable
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Start with Just Solar Photons
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Add the Earths Magnetic Field
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Add the Solar Wind and IMF
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Add CMEs
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Now you understand the Sun-Earth System!