the sun activity and genesis of energy
TRANSCRIPT
THE SUN ACTIVITY AND GENESIS OF THE ENERGY
Milan Milošević Faculty of Science and Mathematics, Niš
Astronomical Society “Alpha”
www.svetnauke.org
Niš, July 23, 2015. BEST Niš - International Academic Course
T.E.S.L.A. - Transforming Environment Sustainably, Looking Ahead!
www.alfa,org,rs
We see it like this...
However, the Sun is more like this!
“When the Sun was God”
http://en.wikipedia.org/wiki/List_of_solar_deities http://ancienthistory.about.com/od/sungodsgoddesses/a/070809sungods.htm
The Colossus of Rhodes (in honor of Apollo)
Helios (Ancient Greece)
God of the Sun and Radiance Aancient Egypt
Stonehenge 3000-2000BC
Where is the Sun?
Hubble Ultra Deep Field
Milky Way
• Galactic plane • Orion arm • 8-10 kpc from the center
(28.000 l.y.) • 230 million years around
the center • Galaxy – 100.000 l.y • “Sweet spot”
• Center: 106 stars/1pc3
• 1 kpc: a few/1pc3
• Here: 1 star per 8pc3
Stelar Evolution
The Sun – our parent star
• Radius 700,000 km • 110 time longer than Earth
• Volume 1.3 milion times larger then Earth • Mass 2⋅1030 kg
• 333,000 time more massive than our planet • 99.8% of the mass of the entire solar system • Mass decrease for 1.5⋅1017 kg per year
More data
• Period 27 day – rotates slowly • Tilt of the axis 7.2O
• Differential rotation: The Sun rotates more rapidly at its equator than at its poles • Equator - 25 days - 2 km/s; • Poles - 29 days- 0.9 km/s
• Proof – the Sun is not solid state body
And more data....
• Very hot body, radiate it’s own energy • Each second 4⋅1026 J • Only a billionth part of a emited enery
arrivea to Earth • Electromagnetic waves – the most visible
light (wavelength: 400 - 800 nm)
And even more data....
• Radiation – from surface layer • Deeper layers - unobservable
• Interior of the Sun – theoretical models • Standard model – R. Sears (1964) • Valid for start about 5⋅109 years old • In core:
• Temperature: 15⋅106 K, • Pressure: 3.4⋅1016 N/m2
Standard solar model
• Spherically – symmetric body, neglect rotation and magnetic field
• State of hydrostatic equilibrium • Change of chemical composition – only
nucler reaction • Mixing of matter – only convective zone • Protosun – homogeneous chemical
composition, evolved without changing the mass during the 4.7 billion years
THE SOLAR INTERIOR
The Solar Interior
• Core (25%)
• Radiation zone (45%)
• Convection zone (30%)
Density and temperature • Average density 1408 kg/m3
• 4 times less then Earth • 1.4 times more than density of water
• Density • 150,000 kg/m3 at the core • 1,000 kg/m3 at 350,000 km • 2⋅10-4 kg/m3 photosphere (10,000 times
less then air at the surface) • 10-23 kg/m3 corona (thin as the best
vacuum in labs on Earth) • Temperature also decreases with increasing
radius in the solar interior, but not as rapidly as the density (15 milion K at the core, 5800 K at the photoshpere)
• Composition – hot gas • Hydrogen 73.4% mass (92% atoms) • Helium 25% (7,8% atoms) • All other (O, C, Fe, N, Ne) 1%
Luminosity
• Size, mass, density, rotation rate, and temperature – familiar, also planets
• Stars and the Sun – energy sources
• Luminosity - the most important of all properties from the point of view of life on Earth
• The Sun radiates energy into space, uniformly in all direction
• Solar constant – 1400 W/m2
• 50-70% reaches surface (clouds reflect 0-20%) • Clear day, sunbather’s body:
• Total surface area about 0.5 m2
• Energy about 500 W (5 x 100 W lightbulbs)
Solar Constant
Solar Energy at Earth
• Optical wavelengths - reaches the top of the atmosphere. • Clouds reflect 17% back into space. • 8% is scattered backwards by air molecules: • 6% is actually directly reflected off the surface back into space
• The total reflectivity of the earth is 31% - Albedo • The 69% of the incoming radiation that doesn't get
reflected back: • 19% gets absorbed directly by dust, ozone and water vapor in the
upper atmosphere (stratosphere, heated by this absorbed radiation) • 4% gets absorbed by clouds located in the troposphere (weather) • remaining 47% of the sunlight that is incident on top of the earth's
atmosphere reaches the surface!
Total Energy
• In all directions • Sphere - radius 1 AU
• Surface area 4π x (1 AU)2, i.e. 3⋅1023 m2 • Luminosity = Solar Constant x Total Area • Luminosity = 4 x 1026 W • That energy can:
• Detonation of 10 milion 1-megaton nuclear bombs • Evaporate all oceans in 6 seconds • Melt Earth’s crust in 3 minutes
Energy Production
• Mass: 2 x 1030 kg, Luminosity = 4 x 1026 W • Efficiency = luminosity / mass = 2 x 10-4 W/kg • “Nothing” – 0.0002 J per kg per second! • A piece of burning wood generates about a million
times more energy per unit mass per unit time • However, have you seen logs burnig for bilions of
year?!?! • Total amount of energy generated by each gram of
solar matter over the entire lifetime of the Sun as a star
Energy Production
• Age of the Sun – 5 bilion years • Total energy – 3 x 1013 J/kg • Average: 60 trilion joules per kilogram! • Not explosive; slow and stady • Uniform and long-lived rate of energy
production • Only one known mechanism:
• Nuclear fusion!
The Core
• 1.6% volume, 0.25 radius • Center - 15 million K • Density 150,000 kg/m3 (20 times of iron) • Pressure 35,000 Mbar
• Huge pressure, however... • Totally ionized gas plasma • Bottom of convective zone
• 1,000 times lower density
Nuclear Fusion
• Combining of light nuclei into heavier ones • Nucleus 1 + nucleus 2 -> nucleus 3 + energy • During a fusion reaction, the total mass
decreases—the mass of nucleus 3 is less than the combined masses of nuclei 1 and 2
• Mass-energy equivalece: E = mc2
• 1 kg of matter – 9 x 1016 J
• Example of the law of conservation of mass and energy
Fundamental Interactions
Nuclear Fusion!
• Hight speed • Strong nuclear force • Distance: 10-15 m • Speed: few 100 km/s • Temperature: 107 K
The Proton-proton Chain
1 1 2eH H H e ν++ → + +
2 1 3H H He γ+ → +3 3 4 1 1He He He H H γ+ → + + +
1 44( ) 2 eH He ν γ→ + +
Solar Neutrinos
• Detectors: large quantities of chlorine or gallium; new nuclei – radioactive
• Other detector – collision with electron in water
• Probability – 1 in 1015 neutrinos passing
• Solar neutino problem • 50-70% are missing!
• Neutino ossiclations! • Super Kamiokane (1998)
• Other (radioactive) sources
• Sudbury Neutrino Observatory (SNO) – 2001 ! ! !
Super-Kamioka Neutrino Detection Experiment
How much energy? • Careful laboratory experiments have determined
the masses of all the particles • 4 protons: 6.6943◦10-27kg • Helium-4 nucleus: 6.6466◦10-27kg • Neutrinos – massles (let’s say!)
• Difference: 0.048◦10-27kg => 4.3◦10-12J (26.7 MeV) • 1 kg hydrogen => 6.4◦1013 J
• 0.71% of the original mass to energy! • 2% kinetic energy of neutrinos; all the rest – gamma rays
• Each second 600 million tons of hydrogen • small mountain; • 4.3 milion tons per second of solar mass is converted to radiation!
Transmission of the Energy
Radiative Zone
• Energy transport by radiation • 0.25 – 0.85 radius of the Sun • Temperature decrease • At begining – 7 milion K • Density:
• 15,000 kg/m3 (2 times Fe) • 350,000 km – density of water
• There is no nuclear reaction!
Radiative Zone • Photons – multiple scattering
• Wavelength – from gamma and
X ray “convert” to visible
• Primary photons – milion years!
• Top border: • temperature is low enought, first
neutral atoms appear (He, H) • All photons – been absorbed
(500,000 km) • Becomes almost totally opaque!
Convective Zone • Depth – 150,000 – 200,000 km • Begins at 500,000 km from the center:
• 2 milion degrees K • 150 kg/m3 (6 times less than water)
• Hot solar gas moves outward while cooler gas above it sinks, creating a characteristic pattern of convection cells
• Archimedes' principle: • Heats and expands - going up • Cools, it becomes denser - going down
• Change of the temperature: • Slow – equilibrium, the end • Rapid – stays hotter, loss of energy by
radiation
SURFACE OF THE SUN
Photosphere
• Bright disk we see from Earth • 350 – 400 km above convective zone • Density – halved at each 130 km
• Average: (1 – 3) 10-4 kg/m3
• thickest layer, much less than Earth's atmosphere (density at 60 km)
• Temperature: 9,000 – 4,500 K • The simplest molecules (CO, H2,CH, CN,...)
• It is not smooth and homogeneous • Year 1784 - “... like a plate of rice soup..."
Granulation
• Jets of gas • 100 – 130 K higher temperature • 10 – 30% brighter • Dark areas
• 35-40% lower brightness, 350-400 K cooler • Dimensions
• 200 – 1,500 km, dark areas 1000 km • About 2 milions each moment • 5 – 15 minutes, velociy (0.3 – 1) km/s
Slika: Thomas Berger; ISP / Royal Swedish Academy of Sciences
Supergranulation
• much larger-scale flow on the solar surface – supergranulation
• 30,000 km across, life-time – few hours • Larger then granulation, convection is more intense • The upwelling gas is hotter and therefore emits more radiation
than the cooler, downward-moving gas. • Cover whole surface of the Sun, each momement – about 2,000 • The gas is displacing magnetic field
• Magnetic field lines are compressed at the boundary, the field is stronger • Matter flow along the field lines • Separates supergranules and prevents mixing of matter
THE SUN’S ATMOSPHERE
THE SUN
The Sun
Solar Spectrum - Fraunhofer lines German physicist
Joseph von Fraunhofer(1787–1826) Photo: Harvard-smithsonian Center for Astrophysics
The Chromosphere
• Above the photosphere • emits very little light of its own and cannot be
observed visually under normal conditions • Characteristic red color, name due the color • Emission of hydrogen Hα line • Discovered – year 1869 • Inhomogeneous
• Lower (upto 1,500 km) • Middle (1,500 – 4,000 km) • Top (4,000 – 10,000 km)
The Chromosphere
• Minimal temperature – lower chromospheres, 4,200K • Stars to raise, maximal 10,000 K ! ! !
• Specter is changed, absorption lines appear • Concentrations of particles decrease
• 1,000 km – 1019 m-3 hydrogen atoms • 10,000 km – 1015 m-3
• Ionisation • 2,000 – 3,000 km – mostly neutral • Above 6,000 km – ionised • Top chromosphere – strongly ionised (25,000 – 300,000 K)
• Far from tranquil • intense turbulent movement of gas
• Every few minutes, small solar storms erupt, expelling jets of hot matter known as spicules into the Sun’s upper atmosphere
• Borders of supergranules • Temperature about 15,000 K • Heigh 3,000 – 4,000 km, upto
7,000 – 12,000 km • Faculas (“little torch”)
• Bright spots, 200 – 300 each day
Transition Zone
The Corona
• Hottest leyer, minimum density • The most spacious, dimmer than the chromosphere • The size and shape depend on the activity
• Minimum - compressed above the poles • Several radius of the Sun
• Transit to interplanetary space • Gas – very high temperatures (up to several million
degrees) and very low density • Strange spectrum – nonterrestrial element “coronium”?
• Fe13+ - green line • 9, 10 and 13 times ionized Fe, 11 and 12 times Ca, 11-15 times Ni
• Different forms of activities • Flares, Coronal mass ejection (CME), Prominences and filaments,
etc
THE ACTIVE SUN
The Active Sun
• The “normal” (peaceful) Sun: Most of the luminosity results from continuous emission from the photosphere. Shine in the same way for the last 5 billion years
• The active Sun - superimposed on this steady, predictable aspect of our star’s energy output is a much more irregular component, characterized by explosive and unpredictable surface activity. It contributes little to the Sun’s total luminosity and probably has no significant bearing on the evolution of the Sun, but it does affect us here on Earth
Sunspots • The most important kind of activity • Numerous dark areas of irregular shape
on the surface of the Sun • The first data – 320 BC • The first study - Galileo, 1613 • One of the first clues that the Sun was not a perfect,
unvarying creation, but rather a place of constant change
Sunspots • Appear 5 – 52 degree south and north of
equator, most often zone 8 – 30 degree • Diametar 1,000 – 100,000 km (groups) • Smaller 1-2 days, developed 10-20 days • Umbra and penumbra • Average:
• 17,500 km – umbra, 37,000 km penumbra • Brightness:
• Umbra 20-30%, penumbra 75-80% • 5,000 times brightner than full Moon!
• Temperature • 25-30% lower than the surface, 4200K
• Around spots – photospheric faculae (“torch”), 10% brighter than surface
Sunspots
Sunspots
• May, 2012 • 100,000 kilometers!
How do sunspots form? • Lines of axial magnetic field
are passing through the layers of the Sun, warp and bend
• The reason - the radial plasma convection and differential rotation
• a part of them goes in front of the other (Babcock’s theory).
Photo: HOA, www.hao.ucar.edu
The Sun’s Magnetic Field
• The magnetic field is about 1000 times greater than the field in neighboring, undisturbed photospheric regions
• Field lines are closed and form ring • One part of it is below the photosphere,
and the second part is above (in the form of arches or loops).
• At the intersection of the formed ring with the surface of the photosphere
• Spots - opposite magnetic polarity • Activity centers on the Sun occur in
places where twisted magnetic field lines emerge from the photosphere.
The Creation of Sunspots
• Stronger magnetic field in the spots opposes further convective motion.
• The weakening or stopping of convection suppress the heat transfer
• Photosphere is cooled in the spots, the glow becomes dimmer than the surroundings.
Coronal Loops
• Magnetic field lines above active spots
Coronal Holes
• Density about 10 times lower • Lines of magnetic field extend from the surface to
outer space • Charged particles follow the field lines • in other areas - field lines near the surface of the Sun • Size - the largest: several hundred thousand
kilometers (occur rarely), usually about ten thousand kilometers - every few hours
• Solar wind is transmitted through them, 600-800 km/s
Explosions • Explosions in the chromosphere and corona • One of the most significant forms of activity • A sudden, short-term processes in which high gain of intens
radiation is emmitted in limited areas of the photosphere • The result of the rapid liberation of magnetic energy and its
transition into kinetic energy, heat and light • They occur above the "neutral" area between two spots of
opposite polarity; usually occur in multipolar groups
Explosions • Before the explosion – stronger radiation of ionized gas of the
corona • In a period of about 1 min – electrons accelerate -> X rays are
emitted • In a few minutes the highest peak intensity is reached, decreases
during next hours • Complex phenomena occurring through the entire depth of the
atmosphere
Explosions
• 20% of energy - optical spectrum • Other: ultraviolet, X and radio rays, heating
and expelling clouds of ionized gas • Traveling through interplanetary space at a
speed of 1,500 km/s
Explosions • During the transition of a group of sunspots
across the disk – 30-50, maximal activity 300! • 100+ per day on the sun; • Strong - several times a year
February, 2014 Class X4.9
Ranking Explosions
• Maximum of energy density of emitted rays during the 5 minutes • Class B - I < 10-6
• Class C - 10-6 < = I < 10-5
• Class M - 10-5 < = I < 10-4
• Class X - I > = 10-4
• Usually X1 and X2
October 24 – 27, 2002.
http://soho.nascom.nasa.gov
September 10 – 11, 2012
http://soho.nascom.nasa.gov
Group 486
• The maximum was in 2001 • However, the end of October 2003 • Three large groups – each larger than
Jupiter (143,000 km) • One – the largest in the last 13 years • Three explosions – in the TOP10 list since
year 1976 • Novembar 4th – record X28 • On the edge of the solar disk
Group 486
Prominences
• Different size and shape • temperature – about 10,000 K, lower than surrounding
chromosphere • Higher density – brighter • Lasting about 3 rotations of the Sun, few - several years • Stability and survival in lower density of corona - only if
the gas pressure of corona is equal to the pressure of gas of protuberance
• Pressure = density x temperature; density 100 times greater than the corona
• the movement of substances - under the influence of a magnetic field; materialization of magnetic field lines
Prominences
• Active prominences • very rapid development (from 10 minutes to
several hours) • Usually formed by condensation in the corona
and dropping down into the chromosphere • Activities - lasting for several hours • Speed of material - several hundred km/s • Temperature of 25,000 K
Eruptive prominences
• Reach great heights, over one million kilometers • The most commonly in the form of an arc, rapidly
growing, after cracking the material falls back into the chromosphere
• Prominences of sunspots – always related to the group of sunspots; form strictly follow the line of strong magnetic fields; when they are at the edge of the Sun can be seen in the form of loop
Prominences - filaments • Sunspots - on the edge of the disc • Filaments - prominences observed
from "above", projection of prominences on the surface
• February 10 - 858,000 kilometers (67x Earth)
• October 2014 - 1 million km!
Solar Wind • EM radiation and
particles continuously leave the Sun
• Solar wind - corpuscular radiation (p, e, He cores)
• The high temperature of the corona makes possible the formation of the solar wind.
• For the first time - Mariner 2 (1962)
Solar Wind
• 10 million km from the Sun – temperature is high enough -> particles are fast enough, so they can overcome the gravity of the Sun
• Solar wind: 108 -109 kg each second • Lost material – reimurse from the surface (it
will evaporate in just 1-2 days without this) • Wind has so far carried of 0.1% of the total
mass of the Sun
Solar Wind
• The heliosphere - the area where the wind reaches
• Voyager 1 to 120 AU • Speed of particles - increases
with distance from the Sun! • 50km / s (at a distance of a
few radii) to several hundred km/s.
• The distance of Earth - 300-750 km/s
The Sun and Earth
The Solar Cycle
• Total number of sunspots on the Sun periodically changes • Conclusion - based on a few centuries of observation • sunspot cycles • maximum on average every 11 years, then decreases • the period between 7 and 15 years
• Heliographic latitude on which sunspots appear • Minimum - a few spots, two narrow zones 25 and 30° from the
equator; • Maximum – zone of 15° to 20° north and south of the equator • End of the cycle - a small number of spots, the zone around the
equator to 10° • The first year of the new cycle overlaps with the last year
of the previous
Maunderov minimum 1645-1715. god
Solar and Heliospheric Observatory (SOHO) The 20 images of the Sun were taken over the 20 years of SOHO’s scientific exploration, all of them in springtime
The Last Maximum
• 24th solar cycle; Maximum was expected during the year 2014.
• “Small” maximum
Ron Turner (Analytic Services, Inc.), number of sunspots since 1755
March 11, 2015.
• The strongest storm in this year, X2.2
Geomagnetical Storms
• September 1-2, 1859 • Carrington’s "event"; the largest recorded! • Eating telegraph lines, electric shock, fire • Aurora: Hawaii, Mexico, Cuba
• March 13, 1989 • Six million people without electricity for 9 hours • Quebec, Canada • Aurora, Texas
• July 14, 2000 • Class X5, right to the Earth • There was no interference • Detected by Voyager 1 and Voyager 2
Geomagnetical Storms
• Sudden perturbations of the Earth's magnetic field, mainly under the influence of the solar wind.
• They occur 17-21 hours after the explosion, or coronal mass ejection. Rapid fluctuations in strength or direction magnetic fields occur at the beginning of the storm, and return to normal within 2-3 days.
Carrington’s Event
• Richard Carrington • Brewer and amateur
astronomer • He watched a projection of
the Sun • Two bright sunspots within
large group • The sudden jump of induced
voltage in telegraph wires has enabled telegraphs to worke without batteries!
Carrington’s Event • Carrington saw the second of, not
so frequent, twin explosions on the Sun.
• The first is arrived to Earth for 40-60 h
• It “cleaned” the way for 2nd that has arrived to the Earth in just 17 hours.
• Magnetosphere of Earth flattened from 60,000 km to only 7,000 km and temporarily destroyed the Van Alen.
• If it happens today damages would cost about 1-2 trilion $$$.
Dst (Distrubance Storm Indeks) – measure "space" weather. It provides information about the strength of the currents caused by solar protons and electrons near the Earth
ASTRONOMY IN NIŠ
Astronomy in Niš
The "Astronomy from the chair" has being implemented by students of Department of Physics, in colaboration with Faculty of Science and Mathematics and Astronomycal Society “Alpha”, within the framework of the “Pokreni se za budućnost" (PZB) sponsored by Philip Morris Inc. Operations
Astronomy in Niš
Astronomy in Niš
The Sun (by AS “Alpha”)
The Sun (by AS “Alpha”)
Astronomy in Niš
М13 у Херкулесу
М57 у Лири
Astronomy in Niš
References:
• M. Milošević; Sunce – tu pored nas, Astronomija vol. 2, pp. 51-54 (2003) • M. Milošević; Sunce – tu pored nas, Astronomija vol. 3, pp. 31-34 (2003) • D. Gajić; Fizika Sunca, Prosveta Niš (2005) • E. Chaisson, S. McMillan; Astronomy Today, 2nd Ed., Prentice Hall (1997) • A. Fraknoi, D. Morrison, S. Wolff; Voyages through the Universe, Saunder
College Publishing (1997) • Web: http://www.svetnauke.org/series/sunce-tu-pored-nas-2
• Photos: • NASA, SOHO, “Astronomy Today”, Wikipedia, Space.com, etc
