A History of Cosmic Rays
Henri Becquerel (1852-1908)
received the 1903 Nobel Prize
in Physics for the discovery
of natural radioactivity.
Wrapped photographic plate
showed clear silhouettes, when
developed, of the uranium salt
samples 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.
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
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
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
Magnitude of Magnetic Force
Lorentz Law
Magnetic force is related to q, v and B
Experimental 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 q from B  F = Fmax sinq
F = q v B sinq
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
Direction of Magnetic Force
Drawing vectors in
tail
head
out of
in to
page
page
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 sinq
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
Right Hand Rule Examples
B
x x x x x x
B
x x x x x x
v
x x x x x x
F q
v
q
F=0
B

v

 q
F
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
What is the direction of the force on a
positive charge when the velocity and
magnetic field B are indicated as below?
B
v
A
v
v
B
The Cosmic Ray Observatory Project
B
C
D
High Energy Physics Group
B
E) none of these
The University of Nebraska-Lincoln
A History of Cosmic Rays
What is the direction of the force on a
positive charge when the velocity and
magnetic field B are indicated as below?
B
B
v
v
B
v
A
B
The Cosmic Ray Observatory Project
C
D
High Energy Physics Group
E) none of these
The University of Nebraska-Lincoln
A History of Cosmic Rays
A positively charged beam enters
a magnetic field region as shown.
What is the direction of B? y
z
A + y (up)
x
B – y (down)
C + x (right)
D + z (out of page)
E – z (into page)
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
An uncharged particle enters a
region with the magnetic field
shown. What path will it follow?
B field
x x x x x x x x x x x x
A
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
x x x x x x x x x x x x
x x x x x x x x x x x x
D
The Cosmic Ray Observatory Project
High Energy Physics Group
C
The University of Nebraska-Lincoln
A History of Cosmic Rays
A charged particle moves
in a straight line through
some region of space.
The net magnetic field
in this region must be zero.
T)True
The Cosmic Ray Observatory Project
F) False
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
B-field
points
into page
From these observations alone,
what definite conclusions can be made?
A.s are positively charged, s negative.
B. s are negatively charged, s positive.
C. can only say , oppositely charged.
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
X
B field
Y
Z
Imagine 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
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
X
B field
Y
Z
Imagine 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
The answer to the first question is (2). A magnetic field exerts forces on moving
charges. If there is no charge (as for a neutral particle) there is no force. The Lorentz
Force 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, which
we 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.
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
B field
out of page
X
Y
Z
Particles A and B have the same charge,
but particle B has more mass. When
particle A enters the magnetic field, it
travels along line Y. When particle B
enters the magnetic field, it will follow line
A) X
B) Y
C) Z
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
B-field
points
into page
From these observations alone, do the
magnitude of their charges compare?
A. q<q
B. q=q
C.  q>q
D. you cannot determine this
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
B-field
points
into page
From these observations alone,
what definite conclusions can be made?
A. s are more massive than s.
B. s are more massive than s.
C. s are more massive than s.
D. Masses cannot be directly compared.
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
1900-01 Studying the deflection of these rays in
magnetic fields, Becquerel and the Curies
establish  rays to be charged particles
Using the procedure developed by J.J. Thomson in 1887
Becquerel determined the ratio of charge q to mass m for
: q/m = 1.76×1011 coulombs/kilogram
identical to the electron!
: q/m = 4.8×107 coulombs/kilogram
4000 times smaller!
Noting helium gas often found trapped in samples of
radioactive 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!
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
s are ionized Helium (bare Helium nuclei)
2-protons, 2-neutrons (positively charged)
s are simply electrons(negatively charged)
q = 2q
m=7296m
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
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
Dubbed this “high” level
radiation
Höhenstrahlung
Hess lands following a
historic 5,300 meter flight.
August 7, 1912
National Geographic photograph
In 1936, Hess was awarded the Nobel prize for this discovery.
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
Cosmic ray
strikes a nucleus
within a layer of
photographic
emulsion
The Cosmic Ray Observatory Project
High Energy Physics Group
50mm
The University of Nebraska-Lincoln
A History of Cosmic Rays
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.
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
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 Wernre Kolhörser build Geiger telescopes
and announce cosmic “rays” contain charged particles
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
1927-28 Jacob Clay travels from Genoa to the Dutch colony
of Java with an ionization chamber and finds
•intensity drops ~6%
•minimum at magnetic equator
1929 Bothe & Kolhorster
•suggest Clay’s Lattitude Effect could be due to
charged primaries deflccted by earth’s magnetic field
•inspired by the Norwegian
mathematician Carl Størmer’s
calculations explaining
colleague
Kristian Birkland’s
theory of the aurora
•
Birkland had
experimented with
electron beams and
a phosphorous-painted
globe of lodestone
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
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 York 10° W
Chicago
0°
L.A.
18° E
Magnetic poles move, and sometimes
reverse direction
Location of S magnetic
pole over last century
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
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
The North pole of a small
magnet (compass) points
towards geographic North
because Earth’s magnetic
South pole is up there!!
The field lines of the
Earth’s field are
not parallel (except
at the equator) to the
surface of the earth “Dip Angle”
1995•
80o
1975•
1948•
1904•
70o
Northwest Territories
The magnetic pole is not exactly
at geographic north (compass
corrections needed). The poles
in fact drift, and occasionally
reverse polarity!
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
1930-33 Arthur Compton (University of Chicago) conducts
a worldwide sea-level
(and mountain 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.
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
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)
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
Positive charged particles headed toward the earth
from space, would tend (at mid-latitudes) to reach
the surface coming down from the
A. North
B. South
C. East
D. West
E. split East and West
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
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!
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
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.
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
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
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
Definite evidence for the celestial generation of Cosmic
Rays came from fortuitous timing of a few high altitude
balloon studies during some spectacular solar flares.
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
Unusual increase in Cosmic ray intensity associated with
an intense solar flare observed
February 28, 1942
the same sunspot associated with this flare erupts again
March 7, 1942
Similarly the
June 4, 1946 solar prominence
is followed by another eruption
July 25, 1946
and the solar flare event of
November 19, 1949
is also captured by airborne cosmic ray instruments
each accompanied by a Sudden Ionospheric Disturbance
which interrupts radio communications on earth
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
During the June 1946 prominence, ultraviolet radiation and
x-rays arrived simultaneous to the visual observation of the
flare. Why? Radio interference began immediately. Charged
particles causing radio blackouts arrived about 3 hours later.
But ground-based monitoring stations at low magnetic latitudes
observed no increase. Why?
However on
November 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 of
Geophysical Research 66
[1961]:p.1363
and the National Bureau of Standards measures
extensive attenuation of radio transmissions
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
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 (The University of Iowa)
reports the first 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!
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of 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
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
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.
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
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.
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
A History of Cosmic Rays
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) into polar orbit. By sampling interplanetary
and magnetospheric particles, contributes to our
understanding of nucleosynthesis and the acceleration of
charged particles.
July 1992
IMAX (Isotope Matter-Antimatter eXperiment) balloonborne 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!
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln
THE
COSMIC
A History
of CosmicRAY
Rays
DEFLECTION SOCIETY
OF
NORTH AMERICA
http://www.geocities.com/SunsetStrip/1483/
The Cosmic Ray Observatory Project
High Energy Physics Group
The University of Nebraska-Lincoln