Cosmic Ray History

Dan Claes

U Nebraska, Lincoln

CROPhttp://cse.unl.edu/~gsnow/crop/crop.html

Selected, and a few comments added by Jim Linnemann

MSU

“If we knew what we were doing, it wouldn’t be called research, would it?” - Albert Einstein

The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln

Cosmic Rays at the Energy FrontierJames W. Cronin, Thomas K. Gaisser

and Simon P. Swordy

Special issue

Magnificent Cosmos March 1998

Bibliography

Clay, Robert and Bruce Dawson, Cosmic Bullets(Addison-Wesley, Reading, Massachusetts, 1997)

Friedlander, Michael W., Cosmic Rays (Harvard University Press, Cambridge, 1989)

or its update,Friedlander, Michael W., A Thin Cosmic Rain (Harvard University Press, Cambridge, 2000)

Hayakawa, Satio, Cosmic Ray Physics(Wiley-Interscience, New York, 1969)

Rutherford, James, Gerald Holton & Fletcher Watson,The Project Physics Course (Holt, Rinehart and Winston, Inc., New York, 1970)

with additional images from NASA’s archive athttp://antwrp.gsfc.nasa.gov/astropix.html

+

An electron and a proton are set free, near each other, deep in outer space. The electron moves towards the proton with

A) constant velocity ( v constant )B) increasing velocity but constant acceleration ( a constant )C) increasing velocity and increasing acceleration

+

An electron and a proton are set free, near each other, deep in outer space. The electron moves towards the proton with

A) constant velocity ( v constant )B) increasing velocity but constant acceleration ( a constant )C) increasing velocity and increasing acceleration

There is a net force on the electron due to the proton’s charge, so the electron accelerates (A is out). As the electron moves closer to the proton, the force it experiences grows stronger (Coulomb’s Law holds F 1/d2). If the force becomes stronger, and the mass does not change, then Newton’s Second Law (F = ma or a = F/m) says that the acceleration increases. The answer to the question must be (C).

When two identical socks are removed from a clothes dryer, they will usually

A) repel each other B) cling to each other C) no way to predictl

When two identical socks are removed from a clothes dryer, they will usually

A) repel each other B) cling to each other C) no way to predictl

If the socks have acquired a static charge, they will most likely have acquired chargeof the same sign, and repel each other. What determines if a material picks upelectrons is the property called electron affinity. The socks acquire their charge by coming into contact will all the other clothes in the dryer. If the socks come in contact with material of a higher electron affinity, the socks will give up electrons to that material. When they come into contact with materials with a lower electron affinity, they will acquire electrons. Both socks will thus acquire the same charge, for the most part.

Of course, it is possible that in the random mixing of clothes in the dryer, one ofthe socks only comes into contact with materials which take electrons from it, and the other socks rubs against materials which give up electrons. The socks will then have opposite charges and attract. However, this is more unlikely.

The answer is (A).

Moving charge by friction

Some atoms/moleculesattract electrons morestrongly than others.

Affinity: a natural liking or sympathy

far:weaker

attraction

close: strongerattraction

electronjumps

Electron Affinityrabbit’s fur

glasswoolsilk

rubberhard plastic

F 1d2

Different materials have different electrons affinities

fur

plastic rod

When fur is rubbed on a plastic rod, both acquire an equal but opposite charge.

If the fur merely rests on top of the plastic, each will acquire equal and opposite charges.

T) True.F) False. Friction is necessary to provide enough heat (energy) for electrons to jump from the fur to the plastic.

fur

plastic rod

When fur is rubbed on a plastic rod, both acquire an equal but opposite charge.

If the fur merely rests on top of the plastic, each will acquire equal and opposite charges.

T) True.F) False. Friction is necessary to provide enough heat (energy) for electrons to jump from the fur to the plastic.

The answer is True. It is not necessary to rub the fur on the rod. If they simplycome into contact with no motion between them, electrons will still jump from theplastic to the fur. Why, then, is the fur rubbed? Because the contact between theplastic and the fur is a bunch of random, jagged edges. (Remember friction!)

In the figure above, there are only about three contact points where the atoms areclose enough for the electrons to make the jump. If instead the fur and plastic are rubbed, many, many more atoms come into contact with each other and more electrons can make the big move. The plastic and fur thus acquire more charge,which makes it more noticeable.

plastic

fur

Far apart: electrons stay withtheir own atoms

both atoms neutral

Close: difference in electronaffinity. Electron jumps.

Move apart: electron stays with theatom it jumped to

both atoms charged

electron

Note: only contact between atoms is necessary. The heat of friction plays no role.

1900 While studying atmospheric electricity, J. Estler and H. Geitel note an unknown, but continuously present source of ions “in the air”

Charles T. R. Wilson’s ionization chamber Electroscopes eventually discharge even when all known causes are removed, i.e., even when electroscopes are

•sealed airtight•flushed with dry, dust-free filtered air•far removed from any radioactive samples •shielded with 2 inches of lead

seemed to indicate an unknown radiation with greater

penetrability than x-rays or radioactive raysSpeculating they might be extraterrestrial, Wilson ran underground tests at night in the Scottish railway, but

observed no change in the discharging rate.

1909 Jesuit priest, Father Thomas Wulf , improved the ionization chamber with a design planned specifically for high altitude balloon flights.

A taut wire pair replaced the gold leaf.

This basic design became the pocket dosimeter carried to record one’s total exposure to ionizing radiation.

1909 Taking his ionization chamber first to the top of the Eiffel Tower (275 m) Wulf observed a 64% drop in the discharge rate.

Familiar with the penetrability of radioactive rays, Wulf expected any ionizing effects due to natural radiation from the ground, would have been heavily absorbed by the “shielding” layers of air.

Henri Becquerel (1852-1908) received the 1903 Nobel Prize in Physics for the discovery of natural radioactivity.

Wrapped photographic plateshowed clear silhouettes, whendeveloped, of the uranium saltsamples stored atop it.

1896 While studying the photographic images of various fluorescent and phosphorescent materials, Becquerel finds potassium-uranyl sulfate spontaneously emits radiation capable of penetrating

•thick opaque black paper•aluminum plates•copper plates

Exhibited by all known compounds of uranium (phosphorescent or not) and metallic uranium itself.

1898 Marie Curie discovers thorium (90Th) Together Pierre and Marie Curie discover polonium (84Po) and radium (88Ra)

1899 Ernest Rutherford identifies 2 distinct kinds of rays emitted by uranium:

- highly ionizing, but completely absorbed by 0.006 cm aluminum

foil or a few cm of air - less ionizing, but penetrate many

meters of air or up to a cm of aluminum.

1900 P. Villard finds in addition to rays, radium emits - the least ionizing, but capable of penetrating many cm of lead, several feet of concrete

+

Magnitude of Magnetic Force

Lorentz LawExperimental observations:

• force depends on the direction of v relative to B

• if v is parallel to B F = 0

• if v is perpendicular to B F = Fmax

• if v is at angle from B F = Fmax sin

F = q v B sin

Magnetic force is related to q, v and B

Direction of Magnetic Force

Direction of magnetic force is “sideways”

•force is perpendicular to both v and B

•use “right-hand” or “left-hand rule” to find its direction

F = q v B sin

in to

page

out of

pagehead

tailDrawing vectors in

An uncharged particle enters a

region with the magnetic field

shown. What path will it follow?

x x x x x x x x x x x x

x x x x x x x x x x x x

x x x x x x x x x x x x

x x x x x x x x x x x x

x x x x x x x x x x x x

x x x x x x x x x x x x

B

CD

B fieldA

A charged particle moves A charged particle moves

in a straight line through in a straight line through

some region of space. some region of space.

The net magnetic field The net magnetic field

in this region must be zero.in this region must be zero.

TT)True)True FF) False) False

B field

X

Y

ZImagine three particles A, B and C all with the same mass, but different charges. (Particle B is neutral). When A enters the magnetic field, it follows path Z.

When particle B enters the magnetic field, it will follow path

A) X B) Y C) Z

When particle C enters the magnetic field, it will follow path

A) X B) Y C) Z

From these observations alone, what definite conclusions can be made? As are positively charged, s negative. B. s are negatively charged, s positive. C. can only say , oppositely charged.

B-fieldpoints

into page

B field

X

Y

ZImagine three particles A, B and C all with the same mass, but different charges. (Particle B is neutral). When A enters the magnetic field, it follows path Z.

When particle B enters the magnetic field, it will follow pathA) X B) Y C) Z

When particle C enters the magnetic field, it will follow pathA) X B) Y C) Z

The answer to the first question is (2). A magnetic field exerts forces on movingcharges. If there is no charge (as for a neutral particle) there is no force. The LorentzForce Law says that F=qvB when v and B are perpendicular. If q=0, the F=0.

The answer to the second question is (3). The charge of C is opposite that of A, whichwe can write as q(C) = q(A), so F(C) = F(A). A minus sign on a vector means that it points in the opposite direction. So if A follows path X, then C must follow path Z.

1900-01 Studying the deflection of these rays inmagnetic fields, Becquerel and the Curiesestablish rays to be charged particles

Using the procedure developed by J.J. Thomson in 1887Becquerel determined the ratio of charge q to mass m for

: q/m = 1.76×1011 coulombs/kilogramidentical to the electron!

: q/m = 4.8×107 coulombs/kilogram 4000 times smaller!

1900-01Noting helium gas often found trapped in samples ofradioactive minerals, Rutherford speculated that particles might be doubly ionized Helium atoms (He++)

1906-1909 Rutherford and T.D.Royds develop their “alpha mousetrap” to collect alpha particles and show this yields a gas with the spectral emission lines of helium!

1896

1899

1912

s are ionized Helium (bare Helium nuclei)

2-protons, 2-neutrons (positively charged)

s are simply electrons(negatively charged)

q = 2q

m=7296m

1911-12 Austrian physicist Victor Hess, of the Vienna University, and 2 assistants, carried Wulf ionization chambers up in a series of hydrogen balloon flights.

• taking ~hour long readings at several altitudes • both ascending and descending

• radiation more intense above 150 meters than at sea level• intensity doubled between 1000 m to 4000 m• increased continuously through 5000 meters

In 1936, Hess was awarded the Nobel prize for this discovery.

Hess lands following a historic 5,300 meter flight. August 7, 1912National Geographic photograph

Dubbed this “high” level radiation Höhenstrahlung

50m

Cosmic ray strikes a nucleuswithin a layer of

photographicemulsion

1913-14 Werner Kolhörster of Berlin’s Physikalisch-Technische Reichsanstalt

•ascends to 9300 m (height of Mount Everest, cruising altitude of a passenger jet!) •ionization rate 50× that at sea level!

1925-26 Robert Millikan of Caltech (winner of the 1923 Nobel prize) initially fails to duplicate such results

• over San Antonio, Texas, found “not more than 25% of that found by European observers.”

Further high-altitude measurements made in collaboration with Ira S. Bowen confirmed the existence of what Millikan coined “cosmic rays”.

Ionization chambers grow more robust and reliable.Automated to work and be recorded remotely.

1911 Rutherford’s assistant Hans Geiger develops a device registering the passage of ionizing particles.

1924 Walter Bothe and Geiger use multiple Geiger counters to establish the tracks followed by electron beams

1928-29 Bothe and Werner Kolhörster build Geiger telescopes and announce cosmic “rays” contain charged particles

1927-28 Jacob Clay from Genoa to the Dutch colony of Java

•ionization intensity drops ~6% •minimum at magnetic equator

1929 Bothe & Kolhörster •suggest Clay’s Lattitude Effect was due to •deflection by earth’s magnetic field•primaries are charged

• inspired by the Norwegian mathematician Carl Størmer’s calculations explaining colleague Kristian Birkland’s theory of the aurora

• Birkland experimented with electron beams and a phosphorous-painted globe of lodestone

Earth’s magnetic field is approximately that of a bar magnet.• Field strength is not the same everywhere

stronger at the poles• Field angle is different in different locations

vertical at poles, horizontal at magnetic equator• South magnetic pole is at north geographic pole

Magnetic axis does not line up with rotation axis• compass correction depends on location

New York10° WChicago 0°L.A. 18° E

Magnetic poles move, and sometimesreverse direction

Cause: Not fully understood, but is somehow due to motion of charged particles in Earth’s molten interior.But why aren’t poles aligned with rotation axis?

Other astronomical bodies with magnetic fields:Mercury and Jupiter, The Sun, The Milky Way galaxy

Location of S magneticpole over last century

The field lines of the Earth’s field are not parallel (except at the equator) to the surface of the earth “Dip Angle”

1948•

1975•

1995•

1904•70o

80o

Northwest Territories

The magnetic pole is not exactlyat geographic north (compass corrections needed). The poles in fact drift, and occasionallyreverse polarity!

The North pole of a small magnet (compass) points towards geographic Northbecause Earth’s magnetic South pole is up there!!

1930-33 Arthur Compton (University of Chicago) conductsa worldwide sea- and mountain-level lattitude survey of cosmic ray intensities and confirms the Latitude Effect.

The 4 curves correspond to 4 seasons. Physical Review 52 [1937]:p.808

Størmer’s “cutoff energies”: only the fastest cosmics reach sea level near the equator less energetic particles are observable at mid-latitudes unrestricted energies in the polar regions

September 21, 1932 Millikan completed a series of tests on the intensity of cosmic rays at various altitudes in a Condor bomber from March Field, California.

1933-35 Thomas Johnson (of the Carnegie Institute) and Bruno Rossi (Italy) independently mount

Geiger counter telescope arrays to test for the

east-west asymmetry predicted by Georges Lemaître (Belgian)

Positive charged particles headed toward the earthfrom space, would tend (at mid-latitudes) to reach the surface coming down from the

A. NorthB. SouthC. EastD. WestE. split East and West

Although cosmic rays do come “from all directions”,

at high altitudes near the equator the intensity is higher coming from

the West than from the East!

1939 Johnson speculates primaries may be protons!

Electroscopes become so robust, datacan be collected remotely (for example

retreived from unmanned weather balloons)

November 11, 1935

Explorer II, a 113,000 cubic foot

helium balloon ascends to a record 22,066 m while collecting atmospheric and cosmic ray data.

1937-1939 Studies of Extended Air Showers begin in France when by accident Pierre Auger and his Russian colleague Dimitry Skobeltzyn notice apparent coincidence between Cosmic Ray telescopes set up several hundred meters apart.

Cloud chamber photographs by George Rochester and J.G. Wilson of Manchester University showed the large number of particles contained within such showers.

1936 Millikan’s group show that at the earth’s surface showers are dominated by electrons, gammas, and

X-particles capable of penetrating deep underground (to lake bottom and deep tunnel experiments) characterized there by isolated single cloud chamber tracks

Definite evidence for the celestial generation of CosmicRays came from fortuitous timing of a few high altitude balloon studies during some spectacular solar flares.

Unusual increase in Cosmic ray intensity associated withan intense solar flare observed

February 28, 1942the same sunspot associated with this flare erupts again

March 7, 1942Similarly the

June 4, 1946 solar prominence

is followed by another eruptionJuly 25, 1946

and the solar flare event ofNovember 19, 1949

is also captured by airborne cosmic ray instrumentseach accompanied by a Sudden Ionospheric Disturbance

which interrupts radio communications on earth

During the June 1946 prominence, ultraviolet radiation and x-rays arrived

A. shortly before B. simultaneous to C. shortly after

the visual observation of the flare.

Why?

During the June 1946 prominence, charged particles causingradio blackouts arrived

A. hours before B. minutes before

C. simultaneous toD. minutes after

E. hours later

the visual observation of the flare.

Particles causing radio blackouts arrived about 3

hours later.

Why?

During the June 1946 prominence, ultraviolet radiation and x-rays arrived simultaneous to the visual observation of the flare. Why? Radio interference began immediately. Chargedparticles causing radio blackouts arrived about 3 hours later.

But ground-based monitoring stations at low magnetic latitudesobserved no increase. Why?

However onNovember 14, 1960 Explorer VII detects solar flares causing “extremely severe” magnetic disturbances in the Earth's atmosphere. The sea level neutron counter at Deep River, Canada records:

J.F.Steljes, H.Carmichael,K.McCracken, Journal ofGeophysical Research 66[1961]:p.1363

and the National Bureau of Standards measures extensive attenuation of radio transmissions

May 11, 1950 A Naval Research Viking research rocket fired from the U.S.S. Norton Sound near Jarvis Island in the Pacific collects cosmic ray and pressure and temperature data.

1952-57 James A. Van Allen (University of Iowa) reports the 1st high altitude survey of total cosmic-ray intensity and latitude variation of heavy nuclei in primary cosmic radiation, from his “Rockoon” (balloon-launched rocket).

February - March, 1958 U.S. Satellites Explorer I and II carry Geiger-Müller counters for Van Allen looping through highly eccentric (50 km perigee, 2600 km apogee) orbits every 2½ hours.

Cosmic ray intensities increase steadily with altitude until 2000 km when counters suddenly registered nothing. Lab tests of duplicate counters suggested they had been overloaded by a region with a sudden 15000× increase in cosmic rays!

1958 Explorer IV and Sputnik III confirm, what is eventually mapped as 2 gigantic radiation belts of trapped ions.

October 13, 1959 Explorer VII was launched. into an Earth orbit. By late December its data reveals

•inner belt mostly protons•outer belt mostly electrons

July 31, 1961 NASA funds high-altitude balloon measurements of the proton and alpha-particle spectrum of primary cosmic radiation conducted by the University of Chicago above Uranium City, Saskatchewan, Canada.

August 17, 1961 Explorer XII radios data on magnetic fields and cosmic rays from a 54,000 mile apogee (and 170 mile perigee).

1962 Enroute to Venus Mariner II detects a continuously flowing solar wind of fast and slow streams, cycling in 27 day intervals (the rotational period of the Sun).

July 1969 Apollo 11 astronauts trap cosmic ray particles on exposed aluminum foil, returned to earth for analysis of its elemental and isotopic composition. With no atmosphere or magnetic field of its own, the moon’s surface provides a constant bombardment of particles.

July 1969 Apollo 11 astronauts trap cosmic ray particles on exposed aluminum foil, returned to earth for analysis of its elemental & isotopic composition. With no atmosphere or magnetic field of its own, the moon’s surface is exposed to a constant barrage of particles.

March 3, 1972 Pioneer 10 launched -on its flyby mission, studies Jupiter's magnetic field and radiation belts.

December 1972 Apollo 17’s lunar surface cosmic ray experiment measured the flux of low energy particles in space (foil detectors brought back to Earth for analysis.

October 26, 1973 IMP-8 launched. Continues today measuring cosmic rays, Earth’s magnetic field, and the near-Earth solar wind from a near-circular, 12-day orbit (half the distance to the moon).

October 1975 to the present GOES (Geostationary Orbiting Environmental Satellite) An early warning system which monitors the Sun's surface for flares.

1977 The Voyager 1 and 2 spacecraft are launched. Each will explore acceleration processes of charged particles to cosmic ray energies.

August 31, 1991 Yohkoh spacecraft launched - Japan/USA/England solar probe - studied high-energy radiation from solar flares.July 1992 SAMPEX (Solar Anomalous and Magnetospheric Particle Explorer) in polar orbit. By sampling inter- planetary & magnetospheric particles, contributes to our understanding of nucleosynthesis and the acceleration of charged particles.

July 1992 IMAX (Isotope Matter-Antimatter eXperiment) balloon- borne superconducting magnetic spectrometer measured the galactic cosmic ray abundances of protons, anti-protons, hydrogen, and helium isotopes.

August 25, 1997 Advanced Composition Explorer (ACE) was launched!

A few more practical

Cosmic Ray effects

• Produces Carbon 14 from Nitrogen 14 – nuclear transmutation– basis of radiocarbon dating– depends on near-constant flux of cosmic

rays

• Cause computer memory errors!

• Natural source of genetic mutations– Worse in Denver– And for those on airplanes a lot

• Everyday demonstration of special relativity

Change a proton to a neutron and

Nitrogen 14 becomes Carbon 14

http://pearl1.lanl.gov/periodic/default.htm

brief communications

680 © 2003 Nature Publishing Group NATURE | VOL 422 | 17 APRIL 2003 | www.nature.com

Space travel

Dual origins of lightflashes seen in space ight flashes are unusual visual phenomena that are observed in space and are caused by the interaction of energetic cosmic-ray particles with the human visual system. Using data gathered on

board the Mir space station during the Sileye-2 experiment1 , we show here that there are two separate components of cosmic rays that cause these flashes: one due to heavy nuclei and one dueto protons. This indicates that perception by an astronaut’s visual apparatus could involve two complementary mechanisms. Ever since light flashes in space were predicted2 before the first space mission and subsequently reported by early Apollo astronauts, attempts to determine their cause have been made both in space and using ground-based particle accelerators3. As a result, several explanations have been proposed to account for the phenomenon ( see ref. 4 and references therein ). The measured rate of occurrence of light flashes (LF) varies for different missions: on Mir5, it is much lower ( Sileye-1, 0.18 0.02 LF min-

1; Sileye-2, 0.130.01 LF min-1) than on Apollo6 ( 0.23 0.1 LF min-1), Skylab7 ( 1.3 0.1 LF min-1) and ASTP8 (0.460.05 LF min-1). This effect is probably due chiefly to a reduction in the speed of low-energy particles by Mir’s hull material (aluminium more than 3 mm thick) and the equip- ment inside the craft. As light flashes are caused by particles inter- acting with the human visual apparatus, their occur- rence should be proportional to particle rate (the so-called ‘latitude effect’). Particle rates outside the region of the South Atlantic Anomaly ( SAA ) depend on the geomagnetic cut-off, which is a function of the position-dependent geomagnetic field intensity and direction. The cut-off C represents the minimum rigidity for cosmic rays to reach Mir’s orbit without being deflected outwards;

it is lower at high geomagnetic latitudes ( for Mir’s orbit, the lowest cut-off is C = 0.6 gigavolts (GV)) and higher at the geomagnetic equator ( where maximum cut-off is C = 16 GV). The lower the cut-off, the higher the rate of particles coming from outside the Earth’s magnetosphere ( we use the vertical cut-off at each location of Mir). Light-flash and particle rates measured inside Mir were divided in 3-GV bins that separated the regions outside ( C ≤ 18 GV ) and inside the SAA (3 ≤ C ≤15 GV, selected for Earth’s magnetic field B 2.510-5 tesla; Fig. 1). The light-flash rate, RLF, is plotted against the particle rate, P, for all particles (almost exclusively protons) in Fig.1a. In Fig.1b, RLF is plotted as a function of the rate of relativistic nuclei, Pn, with charge Z ≥ 6, obtained by selecting particles with high linear-energy transfer ( 20 keV m-1) to guarantee the complete removal of the proton component. From the all-particle plot (Fig. 1a), it is possible to see that RLF is not linearly proportional to proton flux in all regions: in the SAA, it is roughly independent of proton rate ( even though statistical errors preclude any further claim ). For instance, at the centre of the SAA (9≤C≤12 GV), where particle

Figure 1 Rate of occurrence of light flashes on board the Mir space station as a function of particle rate for all particles and for relativistic nuclei inside(circles) and outside(squares) the South Atlantic Anomaly.a, Plot of light-flash rate against proton rate; b, light-flash rate against particle rate for particles with linear-energy transfer of §20 keV mm-1. Linear fits for each region are shown. Data are from the Sileye-2 experiment1, where astronauts wore light-excluding helmets integratedwith cosmic-ray particle-flux detectors, enabling the frequency of flashes to be recorded as a function of background flux & orbit position.

L

A new view of the atmosphere?

• Cosmic ray target• Cosmic ray shield

Cosmic Rays Have Had

A Typical Scientific Cyclic History

“Interesting” is a relative term:

• First an annoying ill-understood effect that muddies measurements– A “background”

• Study and understand the phenomenon– Now a signal

• Use as a tool to probe the unknown– High energy physics discoveries ’30’s –

50’s• Highest energy accelerator available!

– Currently: exploring the universe

• Well-understood parts become an annoying background to the interesting parts

http://www.geocities.com/SunsetStrip/1483/

THE COSMIC RAY DEFLECTION SOCIETY

OFNORTH AMERICA