Effect |
Remarks
/ Explanations |
Earth
Whistlers |
  Whistlers
are produced by lightning and travel along Earth's magnetic
field line from one hemisphere to the other, as shown
in this illustration. In the ionized gas that exists
in this region of space, the high frequencies travel
faster than the low frequencies, thereby dispersing
the wave from the lightning stroke into a whistling
tone that decreases in frequency with increasing time,
hence the term "whistler".
Provided by
Don Gurnett from the University of Iowa.
|
Earth
Multi-hop
Whistlers |
Lightning-generated
whistler waves in Earth's magnetosphere travel along
closed field lines from one hemisphere to the other.
The duration of the whistling tone can vary from one
second to as little as one tenth of a second. The duration
is related to the length of the propagation path. Each
time the whistler wave approaches the base of Earth's
ionosphere and is reflected, it travels back on a slightly
longer path.
A spacecraft traveling in the region
of whistler propagation can detect the same lightning-generated
whistler on successive reflections. The resulting sequence
of descending tones will be separated by the travel
time of the reflected wave (on the order of a second
or more). The duration of each successive tone will
become shorter as the path length becomes longer with
each reflection.
Provided by Don Gurnett from the
University of Iowa. |
Earth
Proton
Whistlers |
A proton
whistler can only be detected in spacecraft measurements
above Earth's ionosphere. The proton whistler will occur
immediately after an upward-propagating whistler has
been generated by a lightning discharge. It is distinct
from the more common, lightning-generated whistler both
in tone and spectral characteristics.
Unlike the
lightning-generated whistler, the proton whistler consists
of a long, slowly rising tone that begins at a low frequency
and levels off in a monotone at a frequency just below
the proton cyclotron frequency, a characteristic frequency
of the ambient plasma. The tone will typically last
several seconds.
Provided by Don Gurnett from the
University of Iowa. |
Earth
Auroral
Kilometric
Radiation
(AKR) |
Auroral
radio emissions are associated with the northern lights
or aurora. Studies, primarily using auroral imagers
and low-frequency radio receivers constructed at The
University of Iowa, have shown the aurora is caused
by energetic electrons striking the atmosphere and that
these same electrons generate intense radio emissions
over a frequency range about 100 to 500 kHz. University
of Iowa instrumentation also revealed that similar radio
emissions occur in association with aurora at Jupiter,
Saturn, Uranus, and Neptune.
Provided by Don Gurnett
from the University of Iowa. |
Earth
Chorus |
Chorus
waves in Earth's magnetosphere are generated in the
Van Allen radiation belts by electrons spiraling along
Earth's magnetic field lines in this region. Once generated,
the chorus waves interact with the moving electrons,
disturbing the spiral orbit of the electrons and causing
them to fall into Earth's upper atmosphere along the
magnetic field lines.
Chorus waves consist of a
rapid succession of intense ascending tones, rising
in frequency over very short time intervals, each tone
lasting typically less than one second. The frequencies
of these rising tones occur in the audio frequency range
and sound like a dawn chorus of chirping birds, a sound
which gives these waves their name.
Provided by
Don Gurnett from the University of Iowa. |
PSR B0329+54 |
This
pulsar is a typical, normal pulsar, rotating with a
period of 0.714519 seconds, i.e. close to 1.40 rotations/sec.
Provided by Michael Kramer from the University of Manchester. |
The Vela Pulsar
PSR B0833-45 |
This
pulsar lies near the centre of the Vela supernova remnant,
which is the debris of the explosion of a massive star
about 10,000 years ago. The pulsar is the collapsed
core of this star, rotating with a period of 89 milliseconds
or about 11 times a second.
Provided by Michael
Kramer from the University of Manchester. |
The Crab Pulsar
PSR B0531+21 |
This
is the youngest known pulsar and lies at the centre
of the Crab Nebula, the supernova remnant of its birth
explosion, which was witnessed by Europeans and Chinese
in the year 1054 A.D. as a day-time light in the sky.
The pulsar rotates about 30 times a second.
Provided
by Michael Kramer from the University of Manchester. |
PSR J0437-4715 |
This
is a recently discovered millisecond pulsar, an old
pulsar which has been spun up by the accretion of material
from a binary companion star as it expands in its red
giant phase. The accretion process results in orbital
angular momentum of the companion star being converted
to rotational angular momentum of the neutron star,
which is now rotating about 174 times a second.
Provided by Michael Kramer from the University of Manchester. |
PSR B1937+21 |
This
is the second fastest known pulsar, rotating with a
period of 0.00155780644887275 seconds, or about 642
times a second. The surface of this star is moving at
about 1/7 of the velocity of light and illustrates the
enormous gravitational forces which prevent it flying
apart due to the immense centrifugal forces. The fastest-rotating
pulsar is PSR J1748-2446ad, which rotates about 10%
faster at 716 times a second.
Provided by Michael
Kramer from the University of Manchester. |
The Pulsars
in 47 Tucanae |
The first
sound file is a sequence of 16 of the known millisecond
pulsars followed by them all played together.
Provided
by Michael Kramer from the University of Manchester. |
The second
file is a sequence of the pulsar sounds as they fade
due to intensity variation caused by interstellar scintillation.
Provided by Michael Kramer from the University of Manchester. |
Sirius |
 Optical
baseband audio scintillation of the star Sirius. If
you click on the icon to the right you can see the setup
Michael OH2AUE used when recording this signal.
|
Betelgeuze |
Optical
baseband audio scintillation of the star Betelgeuze.
If you click on the icon to the right you can see the
setup Michael OH2AUE used when recording this signal. |
