HON 301 Surviving the Anthropocene IV. Living with the Sun Profs. E. Mendieta & F. Walter 2 March 2015 Overview
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The Sun
Solar Activity
Effects of Solar Flares
Effects of Coronal Mass Ejections
The Sun
Our Star
Why is the Sun Important
•  Earth is in equilibrium with the Sun on long
time scales
•  The Sun is a variable star
–  This variability affects the Earth
•  Life has evolved to deal with Solar
variability
–  Our technology has not
What we know about the Sun
• Angular Diameter θ = 32 arcmin (from observations)
• Solar Constant f = 1.4 x 106 erg/sec/cm2 (from observations)
• Distance d = 1.5 x 108 km (1 AU).
(from Kepler's Third Law and the trigonometric parallax of Venus)
• Luminosity L = 4 x 1033 erg/s.
(from the inverse-square law: L = 4π d2 f)
• Radius R = 7 x 105 km. (from geometry: R = π d)
• Mass M = 2 x 1033 gm. (from Newton's version of Kepler's Third Law,
M = (4π2/G) d3/P2)
• Temperature T = 5800 K. (from the black body law: L = 4πR2 σ T4)
• Composition about 74% Hydrogen, 24% Helium, and 2% everything
else (by mass). (from spectroscopy)
Why Does the Sun Shine?
What Makes the Sun Shine?
Inside the Sun
Far Side
Gary Larson
Is the Sun on Fire?
Fire (oxidation) produces light and heat, just like the Sun.
Source: chemical potential energy
Suppose the Sun were made of carbon and oxygen.
•  The Sun could contain 3x1055 C plus twice as many O
Reaction: C + O2 = CO2
M¤ = 2 x 1033 gm
MC = 12 x mp (6 protons + 6 neutrons)
MO = 16 x mp (8 protons + 8 neutrons
mp = 1.6 x 10-24 gm (mass of the proton)
MCO2 = (12 + 32) * mp
N = M¤ / MCO2 = 2.6 X 1055 (number of reactions possible)
Is the Sun on Fire?
Fire produces light and heat, just like the Sun
Suppose the Sun were made of carbon and oxygen.
•  The Sun could contain 3x1055 C plus twice as many O
•  Each chemical reaction releases about 10-11 ergs.
•  Total chemical potential would be 1045 ergs.
3 x 1055 reactions x 1.6 x 10-11 erg/reaction ~ 5 x 1044 erg
Is the Sun on Fire?
Fire produces light and heat, just like the Sun
Suppose the Sun were made of carbon and oxygen.
•  The Sun could contain 3x1055 C plus twice as many O
•  Each chemical reaction releases about 10-11 ergs.
•  Total chemical potential would be 1045 ergs.
•  This is the solar luminosity for 4000 years.
τ = 5 x 1044 erg / 4 x 1033 erg/s = 1011 sec = 4000 years
Other classical possibilities
•  Accretion of comets and asteroids
–  Requires 3% increase in mass in 106 years
–  Year would increase by 2 sec/year
•  Gravitational contraction/cooling
–  Good for 3 x 107 years
–  Sun would shrink perceptibly in 2000 yrs
–  Excluded by eclipse records
Total Eclipse
Uganda, 11/3/13
Annular eclipse
Australia, 5/10/13
Nuclear Fusion
How Fusion Works
E=mc2
•  4 H ⇒ He4 + energy
•  The mass of 4 H atoms exceeds the mass of a He atom
by 0.7%.
•  Every second, the Sun converts 6x108 tons of H into
5.96x108 tons of He.
•  The Sun loses 4x106 tons of mass every second.
•  At this rate, the Sun can maintain its present luminosity
for about 1011 years.
Nuclear Fusion
Proton-Proton reaction
How do we know?
•  The p-p reaction also produces neutrinos.
•  Neutrinos
–  do not interact strongly with matter,
–  pass right through the Sun, and
–  arrive at Earth in 8 minutes.
•  Solar neutrinos were first detected by Ray Davis of BNL
in the 1960s
•  The observations agree with predictions for the “standard
solar model”
Cosmic Gall, by John Updike
Neutrinos, they are very small.
They have no charge and have no mass
And do not interact at all.
The earth is just a silly ball
To them, through which they simply pass,
Like dustmaids down a drafty hall
Or photons through a sheet of glass.
They snub the most exquisite gas,
Ignore the most substantial wall,
Cold-shoulder steel and sounding brass,
Insult the stallion in his stall,
And, scorning barriers of class,
Infiltrate you and me! Like tall
And painless guillotines, they fall
Down through our heads into the grass.
At night, they enter at Nepal
And pierce the lover and his lass
From underneath the bed - you call
It wonderful; I call it crass.
Practical Solar Evolution
Driven by pressure balance: 4H -> He
Source: Wikipedia
Nuclear Timescale
•  1010 years
•  Sun has brightened by 30% in 4.5 Gyr
•  Fusion energy takes 105 – 106 yrs to
diffuse out
•  Gamma-rays thermalize to optical photons
Preview:
The Faint Young Sun Problem
The Surface and Atmosphere
•  Neither generate nor store energy
–  Except in magnetic fields
•  Do influence the Earth
•  Timescales:
–  ~100 years: driver unknown
–  11(22) years: magnetic activity cycle
–  27 days: rotation
–  Minutes-hours: magnetic recombination
The Solar Surface
The photosphere. The visible light disk.
Galileo observed sunspots (earlier noted by Chinese observers)
•  Sunspots are regions of intense magnetic fields
•  Sunspots appear dark because they are cooler than the
photosphere
•  A large sunspot is brighter than the full moon.
Galileo
1613
(first
observed
1610)
Hevelius
1644
Maunder Minimum
Little Ice Age
"Sports on a Frozen River" by Aert van der Neer
Coincidence?
Solar Photosphere
Solar Granulation
Real time: 100 minutes
Size: 20,500 x 19,000 km
Naked-eye Sunpots
Sunspots
Pressure balance:
Gas pressure +
magnetic pressure
in spot
=
gas pressure
outside spot
Bs ~ 2kG
Ts ~ 4500K
Photospheric Magnetic Fields
Zeeman Effect
The Solar Magnetic Field
The Solar Magnetic Field
The Solar Magnetic Field
The Solar Magnetic Field
Temperature Profile
Chromospheric/Coronal
Temperatures
•  Higher temperatures generate higher
energy photons
•  These affect Earth’s environment
differently than do optical light.
Solar Atmospheric Structure
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Photosphere: 5760K; 0 km
Temperature minimum: ~4000K, 500 km
Chromosphere: 8000-20000K, 500-2000 km
Transition Region: .02 - 1 MK, 2000 km
Corona: >106 K, >2000 km
Wind: >106 K, >2000 km
•  Note heights are mean, and density-dependent
The Chromosphere
• First noticed in total solar eclipses.
• Name from the red color (from an emission line of Hydrogen)
• Hot (8000-20,000K) gas heated by magnetic fields.
• Bright regions known as plage.
H-alpha image
Sunspots
The Corona
The diffuse outer atmospheres of the Sun.
The X-ray corona
The white-light corona
Also, the K corona - sunlight scattered from interplanetary dust
The Corona
Flares
The Magnetic
Cycle
Spot cycle ~11 years
Magnetic cycle ~22 yrs
The Magnetic Cycle: Butterfly Diagram
Solar Irradiance
Coronal Cycle
What the Sun
Does When
Active
Coronal Mass Ejections
Coronal Mass Ejections
Coronal Mass Ejections
SDO year 5 – a low maximum
So much for the spectacle…
•  Are solar flares dangerous?
•  Are CMEs dangerous?
•  Life has survived until now
•  The terrestrial atmosphere protects us
Types of radiation
Particulate
• Alpha particles
• Beta particles
• Neutrons
• Fission Fragments
Electromagnetic
• Ionizing
• Non-ionizing
Particulate Radiation
Alpha particles
• Helium nuclei
• penetrate < 10 cm in air, 60 µm in tissue
• stopped by paper
Beta particles
• Electrons
• Penetrate a few mm into tissue
Neutrons
Fission Fragments
Electro-Magnetic Radiation
Penetrating radiation:
• X-rays
• γ rays
Radiation Sources
• Radioactive decay
• High energy collisions
• Particle acceleration
• Astrophysical processes
Definitions
1 Becquerel (Bq) = 1 disintegration/second (dps)
1 Curie = 3.7 x 1010 dps
1 Röntgen = amount of ionizing radiation that
produces 1 esu/cm3 in dry air
1 rad (Röntgen absorbed dose) = 100 erg/gm
1 Gray (Gy) = 100 rads = 1 Joule/kg
Dose = 0.869 f R
f = mass absorption coefficient/air
Rem (biological equivalent dose) = rads x QF
QF (quality factor) ≈ # ion pairs / cm
1 Sievert (Sv) = 100 rem
1 Banana Equivalent Dose (BED) = 0.1 Sv
Half Life
Time for half the original sample to decay
N = N0 e-0.693 T1/2 t
After 1 half life: ½ parent; ½ daughter
After 2 half lives: ¼ parent, ¾ daughter
After 3 half lives: 1/8 parent, 7/8 daughter
How Radiation Kills
Ionizing/penetrating radiation breaks chemical bonds
Particles/ionizing radiation deposits energy
Lethal dose: 500 rad kills half
Can You Avoid Radiation?
No!
Other risks
Solar Flares
•  No consequence on Earth –  γ-­‐rays, X-­‐rays absorbed in atmosphere –  UV absorbed by ozone •  Important for unshielded astronauts Radiation Risks
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Earliest Onset of Radiation Sickness:75,000 mrad
Onset of hematopoietic syndrome: 300,000 mrad
Onset of gastrointestinal syndrome: 1,000,000 mrad
Onset of cerebrovacular syndrome: 10,000,000 mrad
Threshold for cataracts (dose to the eye): 200,000 mrad
Expected 50% death without medical attention: 3 – 5 x105 mrem
Doubling dose for genetic effects: 100,000 mrad
Doubling dose for cancer: 500,000 mrad
Dose for increase cancer risk of 1 in a 1,000: 1,250 mrem (8%/Sv)
Consideration of theraputic abortion threshold: 10,000 mrem (in utero)
SL1 Reactor Accident highest dose to survivor: 27,000 mrem
Three Mile Island (dose at plant duration of the accident): 80 mrem
CMEs and Astronauts
•  Contain high energy protons and
electrons, which can be dangerous
•  Contain magnetic fields, which can
deflect cosmic rays (Forbush Decrease)
How Solar Storms Affect Earth •  GeomagneScally Induced Currents (GIC) •  Charges parScles in upper atmosphere cause varying magneSc fields •  Ampere’s law: changing B -­‐> induces electric fields. •  Electric potenSals drive currents in ground •  Current strength depends on conducSvity •  Current flow in power lines can overload the grid. The 1 Sept 1859 Flare
•  9/1: Carrington observed white-light flare
•  9/2: Brilliant auroras seen
(as far south as the Caribbean)
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Telegraphs functioned w/o batteries
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Telegraph operators shocked
•  First solar flare recorded
•  Strongest in ~500 years
•  Today it would
–  Bring down the electrical grid
–  Fry satellites
The 23 July 2012 Flare
•  2 CMEs recorded
•  At least as energetic as the Carrington 1859 event
•  Missed the earth by about 1 week
•  Estimated economic impact:
–  $2 trillion ($2 x 1012) – 20 x greater than Katrina
–  Heavy-duty transformers destroyed; take years to
manufacture
–  Power grid impacted for years
http://science.nasa.gov/science-news/science-at-nasa/
2014/23jul_superstorm/
Economic Impact
•  Schrijver et al. analyzed insurance claims,
2000-2010
–  Claims increase with geomagnetic activity
–  ~4% of US power grid disturbances due to
geomagnetic storms and GICs
•  59% caused by “electrical surges”
•  Implies about 500 disturbances/year
–  Estimated losses $118-188B/year (2000)
The Odds
12% in the next decade
Space Weather •  GeomagneSc Storms: G (1-­‐5) •  Solar RadiaSon Storms: S (1-­‐5) •  Radio Blackouts: R (1-­‐5) •  h_p://spaceweather.com/ NOAA Space Weather Scales
Category
Scale
Effect
Descriptor
G4
G3
G2
G1
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Extreme
Severe
Strong
Moderate
Minor
Average Frequency
(1 cycle = 11 years)
Duration of event will influence severity of effects
Geomagnetic Storms
G5
Physical
measure
Power systems: widespread voltage control problems and protective system problems can occur, some grid
systems may experience complete collapse or blackouts. Transformers may experience damage.
Spacecraft operations: may experience extensive surface charging, problems with orientation, uplink/downlink
and tracking satellites.
Other systems: pipeline currents can reach hundreds of amps, HF (high frequency) radio propagation may be
impossible in many areas for one to two days, satellite navigation may be degraded for days, low-frequency radio
navigation can be out for hours, and aurora has been seen as low as Florida and southern Texas (typically 40°
geomagnetic lat.).**
Power systems: possible widespread voltage control problems and some protective systems will mistakenly trip
out key assets from the grid.
Spacecraft operations: may experience surface charging and tracking problems, corrections may be needed for
orientation problems.
Other systems: induced pipeline currents affect preventive measures, HF radio propagation sporadic, satellite
navigation degraded for hours, low-frequency radio navigation disrupted, and aurora has been seen as low as
Alabama and northern California (typically 45° geomagnetic lat.).**
Power systems: voltage corrections may be required, false alarms triggered on some protection devices.
Spacecraft operations: surface charging may occur on satellite components, drag may increase on low-Earth-orbit
satellites, and corrections may be needed for orientation problems.
Other systems: intermittent satellite navigation and low-frequency radio navigation problems may occur, HF
radio may be intermittent, and aurora has been seen as low as Illinois and Oregon (typically 50° geomagnetic
lat.).**
Power systems: high-latitude power systems may experience voltage alarms, long-duration storms may cause
transformer damage.
Spacecraft operations: corrective actions to orientation may be required by ground control; possible changes in
drag affect orbit predictions.
Other systems: HF radio propagation can fade at higher latitudes, and aurora has been seen as low as New York
and Idaho (typically 55° geomagnetic lat.).**
Power systems: weak power grid fluctuations can occur.
Spacecraft operations: minor impact on satellite operations possible.
Other systems: migratory animals are affected at this and higher levels; aurora is commonly visible at high
latitudes (northern Michigan and Maine).**
Kp values*
determined
every 3 hours
Number of storm events
when Kp level was met;
(number of storm days)
Kp=9
4 per cycle
(4 days per cycle)
Kp=8
100 per cycle
(60 days per cycle)
Kp=7
200 per cycle
(130 days per cycle)
Kp=6
600 per cycle
(360 days per cycle)
Kp=5
1700 per cycle
(900 days per cycle)
Flux level of >
10 MeV
particles (ions)*
Number of events when
flux level was met**
105
Fewer than 1 per cycle
Based on this measure, but other physical measures are also considered.
For specific locations around the globe, use geomagnetic latitude to determine likely sightings (see www.swpc.noaa.gov/Aurora)
Solar Radiation Storms
Biological: unavoidable high radiation hazard to astronauts on EVA (extra-vehicular activity); passengers and
crew in high-flying aircraft at high latitudes may be exposed to radiation risk. ***
G2
G1
*
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Moderate
Minor
Power systems: high-latitude power systems may experience voltage alarms, long-duration storms may cause
transformer damage.
Spacecraft operations: corrective actions to orientation may be required by ground control; possible changes in
drag affect orbit predictions.
Other systems: HF radio propagation can fade at higher latitudes, and aurora has been seen as low as New York
and Idaho (typically 55° geomagnetic lat.).**
Power systems: weak power grid fluctuations can occur.
Spacecraft operations: minor impact on satellite operations possible.
Other systems: migratory animals are affected at this and higher levels; aurora is commonly visible at high
latitudes (northern Michigan and Maine).**
Kp=6
600 per cycle
(360 days per cycle)
Kp=5
1700 per cycle
(900 days per cycle)
Flux level of >
10 MeV
particles (ions)*
Number of events when
flux level was met**
105
Fewer than 1 per cycle
104
3 per cycle
103
10 per cycle
102
25 per cycle
10
50 per cycle
GOES X-ray
peak brightness
by class and by
flux*
Number of events when
flux level was met;
(number of storm days)
X20
(2x10-3)
Fewer than 1 per cycle
X10
(10-3)
8 per cycle
(8 days per cycle)
Based on this measure, but other physical measures are also considered.
For specific locations around the globe, use geomagnetic latitude to determine likely sightings (see www.swpc.noaa.gov/Aurora)
Solar Radiation Storms
S5
S4
S3
Extreme
Severe
Strong
S2
Moderate
S1
Minor
Biological: unavoidable high radiation hazard to astronauts on EVA (extra-vehicular activity); passengers and
crew in high-flying aircraft at high latitudes may be exposed to radiation risk. ***
Satellite operations: satellites may be rendered useless, memory impacts can cause loss of control, may cause
serious noise in image data, star-trackers may be unable to locate sources; permanent damage to solar panels
possible.
Other systems: complete blackout of HF (high frequency) communications possible through the polar regions,
and position errors make navigation operations extremely difficult.
Biological: unavoidable radiation hazard to astronauts on EVA; passengers and crew in high-flying aircraft at
high latitudes may be exposed to radiation risk.***
Satellite operations: may experience memory device problems and noise on imaging systems; star-tracker
problems may cause orientation problems, and solar panel efficiency can be degraded.
Other systems: blackout of HF radio communications through the polar regions and increased navigation errors
over several days are likely.
Biological: radiation hazard avoidance recommended for astronauts on EVA; passengers and crew in high-flying
aircraft at high latitudes may be exposed to radiation risk.***
Satellite operations: single-event upsets, noise in imaging systems, and slight reduction of efficiency in solar
panel are likely.
Other systems: degraded HF radio propagation through the polar regions and navigation position errors likely.
Biological: passengers and crew in high-flying aircraft at high latitudes may be exposed to elevated radiation
risk.***
Satellite operations: infrequent single-event upsets possible.
Other systems: effects on HF propagation through the polar regions, and navigation at polar cap locations
possibly affected.
Biological: none.
Satellite operations: none.
Other systems: minor impacts on HF radio in the polar regions.
*
Flux levels are 5 minute averages. Flux in particles·s-1·ster-1·cm-2 Based on this measure, but other physical measures are also considered.
** These events can last more than one day.
*** High energy particle (>100 MeV) are a better indicator of radiation risk to passenger and crews. Pregnant women are particularly susceptible.
Radio Blackouts
R5
R4
Extreme
Severe
HF Radio: Complete HF (high frequency**) radio blackout on the entire sunlit side of the Earth lasting for a
number of hours. This results in no HF radio contact with mariners and en route aviators in this sector.
Navigation: Low-frequency navigation signals used by maritime and general aviation systems experience outages
on the sunlit side of the Earth for many hours, causing loss in positioning. Increased satellite navigation errors in
positioning for several hours on the sunlit side of Earth, which may spread into the night side.
HF Radio: HF radio communication blackout on most of the sunlit side of Earth for one to two hours. HF radio
contact lost during this time.
Navigation: Outages of low-frequency navigation signals cause increased error in positioning for one to two
S3
Strong
S2
Moderate
S1
Minor
Satellite operations: single-event upsets, noise in imaging systems, and slight reduction of efficiency in solar
panel are likely.
Other systems: degraded HF radio propagation through the polar regions and navigation position errors likely.
Biological: passengers and crew in high-flying aircraft at high latitudes may be exposed to elevated radiation
risk.***
Satellite operations: infrequent single-event upsets possible.
Other systems: effects on HF propagation through the polar regions, and navigation at polar cap locations
possibly affected.
Biological: none.
Satellite operations: none.
Other systems: minor impacts on HF radio in the polar regions.
102
25 per cycle
10
50 per cycle
GOES X-ray
peak brightness
by class and by
flux*
Number of events when
flux level was met;
(number of storm days)
X20
(2x10-3)
Fewer than 1 per cycle
X10
(10-3)
8 per cycle
(8 days per cycle)
X1
(10-4)
175 per cycle
(140 days per cycle)
M5
(5x10-5)
350 per cycle
(300 days per cycle)
M1
(10-5)
2000 per cycle
(950 days per cycle)
*
Flux levels are 5 minute averages. Flux in particles·s-1·ster-1·cm-2 Based on this measure, but other physical measures are also considered.
** These events can last more than one day.
*** High energy particle (>100 MeV) are a better indicator of radiation risk to passenger and crews. Pregnant women are particularly susceptible.
Radio Blackouts
R5
Extreme
R4
Severe
R3
Strong
R2
Moderate
R1
Minor
*
**
HF Radio: Complete HF (high frequency**) radio blackout on the entire sunlit side of the Earth lasting for a
number of hours. This results in no HF radio contact with mariners and en route aviators in this sector.
Navigation: Low-frequency navigation signals used by maritime and general aviation systems experience outages
on the sunlit side of the Earth for many hours, causing loss in positioning. Increased satellite navigation errors in
positioning for several hours on the sunlit side of Earth, which may spread into the night side.
HF Radio: HF radio communication blackout on most of the sunlit side of Earth for one to two hours. HF radio
contact lost during this time.
Navigation: Outages of low-frequency navigation signals cause increased error in positioning for one to two
hours. Minor disruptions of satellite navigation possible on the sunlit side of Earth.
HF Radio: Wide area blackout of HF radio communication, loss of radio contact for about an hour on sunlit side
of Earth.
Navigation: Low-frequency navigation signals degraded for about an hour.
HF Radio: Limited blackout of HF radio communication on sunlit side of the Earth, loss of radio contact for tens
of minutes.
Navigation: Degradation of low-frequency navigation signals for tens of minutes.
HF Radio: Weak or minor degradation of HF radio communication on sunlit side of the Earth, occasional loss of
radio contact.
Navigation: Low-frequency navigation signals degraded for brief intervals.
Flux, measured in the 0.1-0.8 nm range, in W·m-2. Based on this measure, but other physical measures are also considered.
Other frequencies may also be affected by these conditions.
URL: www.swpc.noaa.gov/NOAAscales
April 7, 2011
Early Warning Spacecraa at L1 provide: •  Up to 4 days warning for CMEs •  ~30 min warning for fast flare protons •  No warning for photons L1 = the inner Lagrangian point •  where terrestrial and solar graviSes balance •  about 1 million miles towards the Sun Forecasts are improving All CopaceSc? All CopaceSc? Not so fast. Superflares
•  Solar flares:
–  dN/dE ~ E-1.7+/- 0.2
–  Brightest observed ~ 1032 erg
•  Schaefer et al. (2000) reported 9 larger
flares on solar-like stars
•  Maehara et al. (2012) analyzed Kepler
database for superflares (E>1033 erg)
Superflares
•  Maehara et al. (2012) found
–  dN/dE = E-2.3+/- 0.3
–  365 superflares on 148 solar-like stars
–  14 superflares on 10 old/inactive stars
•  Conclusion:
–  A 1035 erg solar flare could be expected
every 5000 years
More Pictures and References
•  Solar Data Analysis Center (SDAC): http://umbra.nascom.nasa.gov/
includes links to SOHO, SDO, HINODE, and YOHKOH
Other Solar Missions:
–  STEREO:
http://www.nasa.gov/mission_pages/stereo/main/index.html
–  TRACE: http://trace.lmsal.com/
Solar Storms
–  https://medium.com/starts-with-a-bang/the-truth-about-solarstorms-1ab160203da4