General presentation

1. Van Allen Radiation Belt
Katravath Santhosh
18EC63R10,
RF&Microwave Engineering
Indian Institute of Technology Kharagpur
santhoshkatravath@gmai.com
Abstract— In this paper we describe the Van Allen Belt ,
and see how it is effecting on the space program like satellite
launching ,man mission, limiting the orbit availability , reasons
to occur belts , and classifying the belts based on recent studies
done by NASA. We also describe radiation phenomenon.
We see what NASA and other space agencies did till date
on Van Allen Belt. Its effect on crew and satellite, also look in
what type of advanced Shielding we have in order to be
protected,
Our main moto is if we can clear away the high-energy
particles that pose the hazard by different approaches, what
advantages we get by ridding these belts off.
Keywords— Radiation, Whistle mode, MeV (Mega electron
Volts)
I. INTRODUCTION
HE Van Allen Belt is a zone of high energetic charged
particles, most of which originate from the solar
wind(10-15,000MeV), that are captured by and held
around a planet by that planet's magnetic field.
Which are shaped as giant donut, earth has two such belts
and sometimes one other may be temporarily created. Their
properties vary according to solar activities and they
represent a hazard to satellites and humans in space. These
are naturally occurring belts of radiation.
James Van Allen, a physicist at the University of Iowa,
discovered these radiation belts in 1958 after the launch of
Explorer 1, the first U.S. satellite. The radiation belts were
eventually named after him.
The belts are located in the inner region of the Earth's
magnetosphere. The Van Allen belts are most intense over
the Equator and are effectively absent above the poles. No
real gap exists between the two zones; they actually merge
gradually, with the flux of charged particles showing two
regions of maximum density.
Figure 1: Solar flares
II. REASONS OF BELTS FORMATION
A. Due to ionized Charged particle radiation from sun and
deep space
Electrons ,protons, neutrinos and neutrons from sun flew
to earth and react with earth magnetic field ,and some
particles attracted by north-south poles where they create
light in the poles side. And others are captured in the earth
magnetic fields and forms Van Allen Belt.
Also these are formed as a result of cosmic ray collisions
in the upper atmosphere. These particles do not have enough
energy to escape into space. Other nuclei particles like alpha
and beta are found in lesser quantities. The radiation belt can
be a danger to satellites that spend considerable time in the
radiation belt. So the delicate parts should be protected from
radiation with the help of adequate shielding.
III. CLASSIFYING DIFFERENT BELTS
Mainly two belts are there in Van Allen Belt,
A) Inner belt: (energy range of particles in this region 1-
100MeV):
These are at altitude of 600km-6000km above the earth.
This belts contains high concentrations of energetic protons
with energy (>10 MeV) and electrons (>1KeV), trapped by
the strong magnetic fields.
The inner Van Allen belt consists largely of highly
energetic protons, with energy exceeding 30MeV. The peak
intensity of these protons is approximately 20,000 particles
per second crossing a spherical area of one square cm in all
directions. It is believed that the protons of the inner belt
originate from the decay of neutrons produced when high-
energy cosmic rays from outside the solar system collide
with atoms and molecules of Earth’s atmosphere.
Some neutrons are ejected back from the atmosphere
travel through the region of the belt, a small percentage of
them decay into protons and electrons. These particles move
in paths along the lines of force of Earth’s magnetic field
lines.
As the particles approach either of the magnetic poles,
the increase in the strength of the field causes them to be
reflected. Because of this so-called magnetic mirror effect,
the particles bounce back and forth between the magnetic
poles. Over time, they collide with atoms in the thin
atmosphere, resulting in their removal from the belt.
B) Outer (10,000km-65,000km): (energy range of particles
in this region 0.1–10 MeV)
The outer belt consists mainly of high energy electrons
trapped by the Earth's magnetosphere.
T

2. The outer Van Allen belt contains charged particles of
both atmospheric and solar origin, the latter consisting
largely of helium ions from the solar wind (steady stream of
particles emanating from the Sun).
Figure 2: Concentration of charged particles in two belts
The protons of the outer belt have much lower energies
than those of the inner belt, and their fluxes are much higher.
The most energetic particles of the outer belt are electrons,
whose energies reach up to several hundred million electron
volts.
Mostly variable in size and particle concentration. That is
maximum concentration intensity in donut along earth’s
equator.
Largely fluctuates to solar flares and cosmic waves and
radiation from the interstellar wind.
In 2012, observations from the Van Allen Probes showed
that a third belt can sometimes appear. This third belt
increased the size occupied by them, which is not good for
orbit availability.
IV. RADIATION
In order to have understanding of impact of the solar
wind and sun’s radiation effect, we must have knowledge of
radiation.
Radiation is the process by which energy is emitted as
either particles or waves. It can take the form of sound, heat,
or light. It’s a form of electromagnetic waves, ranging from
radio waves, though the visible light spectrum, and up
through to gamma waves, whole EM spectrum.
Classified based on whether it has enough energy to
knock electrons off atoms that it interacts with, as well as
being able to do lower-energy damage such as breaking
chemical bonds in molecules
Radiation types:
1) Ionizing Radiation: Caused by unstable atoms giving
off energy to reach a more stable state (occur in Van Allen
Belt). For instance, a sunburn is a type of radiation damage.
2) Non-Ionizing Radiation: such as radio and microwave
energy, is considered harmful only to the extent of the
amount of heat energy it transfers to whatever it hits. For
example, microwave ovens use non-ionizing radiation to
cook food. The radiation vibrates water contained in food,
which creates heat. That heat cooks the food.
A. Units
 Absorbed radiation dose:
1Grey=100Rads.
 Dose equivalent radiation :
1Sievert=100Rems
According to the sources
800Rads or Rems may lead to death.
200Rads or Rems lead to headache.
1 X-ray of abdominal takes=1.4Rads
Radiation dosage by Dosimeter in Apollo space travel
V. NASA ANALYSIS ON VAN ALLEN RADIATION BELT
A.
1) Explorer 1, Explorer 3, Pioneer 3, Orion Multi-
Purpose Crew Vehicle.
Figure 3: Third belt found
B. In 2012
Van Allen Probes (2012) spacecraft provide the
measurements needed to characterize and quantify the
processes that produce relativistic ions and electrons. They
measure the dynamic properties of charged particles.
The mission was to understand the sun’s influence on the
earth and near earth space by studying the planet’s radiation
belts on various scales of space and time.
Discovering how the particles ions and electrons in the
belts are accelerated and transported, how electrons are lost
and how the belts change during geomagnetic storms.
In February 2013, a third temporary Van Allen Radiation
Belt was discovered by using data gathered by Van Allen
Probes. The said third belt lasted a few weeks.
1) Findings: Whistle in belts(noise):

3. NASA’s Van Allen Belt mission have recorded audio-
frequency noise made by energetic electrons emitting what's
known as “whistler waves”.
Space is not empty, nor is it silent. Vacuum, space contains
energetic charged particles, governed by magnetic and
electric fields, and it behaves unusual. Particles giving
plasma waves.
Figure 4: Apollo mission trajectory to avoid radiation
belts
Plasma waves, create a rhythmic cacophony that we can
hear. One type of plasma wave fundamental to shaping our
near-Earth environment are whistler mode waves.
There's the plasma sphere around Earth, relatively
dense and cold, which produces different frequencies to
hotter, less dense waves in the Van Allen Belts. Those
waves (going by the snappy name Enhanced EMIC –
Electromagnetic Ion Cyclotron – waves) hiss.
Figure 5: Whistle noise in van allen belt
VI. CAN WE HACK THE RADIATION BELTS ?
Earth’s own magnetic field lines which acts like a huge
ion particle accelerator to ramp these ions up to dangerous
speeds, with huge amount energy which can pass through
large shielding easily.
Many satellites and other orbiting equipment have to shut
off periodically, though, to avoid damage in the belts. That’s
a problem when launching equipment is often the single
most expensive element of a mission even one that makes
them ship expensive shielding into space.
It remains uncertain as to whether removing these
radiation belts might have consequences. At present we don’t
feel there is any downside to not having them, but as with all
things geophysical, it is hard to know all the complex inter
connections between the various systems and estimate the
full effect of removing the radiation belts completely.
Apollo astronauts figured out the human effects of
traveling through the Van Allen belts, now know they’re
mostly dangerous to electrical equipment, like changing
electron-hole pairs in the circuit.
The belts vary with the changing of the seasons, and a
manned mission can usually get through with only a minimal
increase in radiation exposure.
And also in order to have large orbiting space we have to
remove these, to avoid congested orbiting.
A. Different strategies proposed to clear belts:
1) Using carefully tuned electromagnetic waves to drive
these particles out of space and into Earth’s atmosphere.
Initial idea was to elevate electrons in the outer belt, and
latest strategy was to target protons in the inner belt.
One idea of radiation-clearing strategy involves using
very large radio transmitters on the ground to beam very low
frequency (VLF) waves upward. These can in principle
interact with and scatter charges in the radiation belt and
drive them into the upper atmosphere.
Second idea is type of VLF electromagnetic wave
(Electromagnetic ion cyclotron (EMIC) wave) could
potentially disperse protons in the inner belt by a million 15-
meter antennas for one year.
2) Nuclear explosion:
Initial efforts to clear the Van Allen belts targeted
electrons because they tend to get trapped there as the result
of high- altitude nuclear explosions. In 1962.
A U.S. high-altitude nuclear weapons test named
Starfish Prime generated a highly energetic artificial electron
belt that disabled the first commercial communications
satellite, TelStar 1, so researchers sought ways to protect
spacecraft from nuclear weapons used in space.

4. B. Shielding to satellite and crew:
1) There are ways to make spacecraft more resistant
against this radiation. Spikes on their surfaces known as
electron emitters can radiate away excess lower-energy
electrons that might otherwise accumulate and cause a spark.
2) Shielding can help keep high-energy protons and
electrons from penetrating non-conducting materials and
building up inside them, which could lead to a damaging
discharge.
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VII. BELTS EFFECT ON CREW & SATELLITE
A. On satellite :
Ionization creates charges (electron-hole pairs) which
leads to change properties of basic circuits .
Radiation has bad effects on electronics - in a total dose
(the accumulation of damage from lots of small hits) and in a
“increased probability of single event effects ”(bit flips, latch
up, ).
B. On astronaut:
Body parts can be damaged at level as low as 200 rads .
Causes severe problems such as DNA molecule impair ,
cancer. Skin burns or acute radiation syndrome can occur
when doses of radiation exceed certain levels.
Figure 6: Radiation impact on DNA
Beyond certain thresholds, radiation can impair the
functioning of tissues, organs. Skin redness, hair loss, brain .
1) Blood System:
When a person is exposed to around 100 rads, the blood's
cell count will be reduced, leaving the victim to more
infection.
2) Heart:
Intense exposure to radioactive material at 1,000 to 5,000
rads would do immediate damage to small blood vessels and
probably cause heart failure and death directly.
3) Brain:
Since brain cells do not reproduce, they won't be
damaged directly unless the exposure is 5,000 rads or
greater. Like the heart, radiation kills nerve cells and small
blood vessels.
VIII. SHIELDING
Apollo 14 crew experienced 0.16-1.14rad≈2 CT scans
of abdominal (x-ray), Shielding absorbed/deflected most of
that.
Space suits provide protection from the UV rays, but they
provide limited protection from particle radiation and gamma
and x ray. If particles have enough energy they simply pass
through the space suit.
Light weight radiation materials used for shielding (such
as Lead) which emits low x-ray particles.
LEAD: Effective at stopping gamma-rays and x-rays,
lead is used as radiation protection in applications ranging
from x-ray imaging and PET rooms to nuclear reactors.
Space agencies use well-guarded capsules to not let
radiation from space to pass through spacecraft, Crew
capsule like ISRO-Gaganyaan, Space-X Dragon capsule,
NASA-Orion capsule.
Spikes on their spacecraft surfaces known as electron
emitters (avoid sparks by low energy particles), Shielding
can help keep high-energy protons and electrons (avoid
penetrating, discharging)
Using carefully tuned electromagnetic waves to drive
these particles out of space and into Earth’s atmosphere.
Polyethylene, Aluminum, Stainless steel also used for
shielding.
IX. CONCLUSION
1) They (belts) deflect the radiation, solar wind and solar
storms that the Sun emits. Helps in not letting the interstellar
wind and solar wind to directly enter into our atmosphere
2) Plasma Aurora in earth pole side formed as energetic
electrically charged particles (mostly electrons) accelerate
along the magnetic field lines into the upper atmosphere,
where they collide with gas atoms, causing the atoms to give
off light.
3) Energy of an electron here (1-15KeV) Research on
this belts are still on way to understand exact behavior of
outer most belt.

5. 4) To avoid these deadly radiation scientist found low
radiation trajectory. Established almost conclusively the
existence of a Van Allen radiation belt on the planet Jupiter.
Apollo vehicles were traveling quite fast and only spent
about 15 minutes in the most dangerous region and less than
an hour total in the belts (each way).
Figure 7: Plasma Aurora
REFERENCES
[1] Converion of radiation dosage https://www.convert-
me.com/en/convert/radiation/?u=rrgastro&v=1
[2] Analysis of the passage of a spacecraft between the Van Allen belts
considering a low and high solar activity (M R da Silva1 and E M
Rocco1)
[3] nasa.gov Van Allen Belt
[4] A study of the duration of the passage through the Van Allen Belts for a
Spacecraft going to the Moon ( T C Oliveira )
[5] Can we hack the van allen belts -- spectrum.ieee.org
[6] http://adsbit.harvard.edu
[7] https://www.univie.ac.at/geographie
[8] The Deadly Van Allen Belts http://spacemath.gsfc.nasa.gov
[9] https://www.space.com/27979-van-allen-belts-barrier-particles.html