scholarly journals A survey of Galileo plasma wave instrument observations of Jovian whistler-mode chorus

2008 ◽  
Vol 26 (7) ◽  
pp. 1819-1828 ◽  
Author(s):  
J. D. Menietti ◽  
R. B. Horne ◽  
D. A. Gurnett ◽  
G. B. Hospodarsky ◽  
C. W. Piker ◽  
...  
Keyword(s):  
Plasma Wave ◽  
Radiation Belt ◽  
Good Reason ◽  
Radial Distance ◽  
Local Times ◽  
Whistler Mode ◽  
Jovian Magnetosphere ◽  
Spacecraft Trajectory ◽  
Almost All ◽  
The Magnetic Field

Abstract. A survey of plasma wave observations at Jupiter obtained by the plasma wave instrument on board the Galileo spacecraft is presented. The observations indicate that chorus emissions are observed commonly in the Jovian magnetosphere near the magnetic equator in the approximate radial range 6<r<10 RJ. The survey includes almost all local times but not equally sampled in radial distance due to the spacecraft trajectory. The data suggest that chorus emissions are somewhat more intense on the dayside, but this may be a result of insufficient nightside observations. The orbit of Galileo is also restricted to ±3° of the Jovigraphic equator, but the tilt of the magnetic field permits coverage of a range of magnetic latitudes of −13°<λmag<+13°. The similarities of chorus emissions to terrestrial observations are a good reason to speculate that Jovian chorus emission may play a significant role in the stochastic acceleration of electrons in the radial range 6–10 RJ as recent studies indicate. These electrons may then be transported inward by radial diffusion where they are additionally accelerated to form the synchrotron radiation belt source.

scholarly journals First results from the Cluster wideband plasma wave investigation

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1259-1272 ◽  
Author(s):  
D. A. Gurnett ◽  
R. L. Huff ◽  
J. S. Pickett ◽  
A. M. Persoon ◽  
R. L. Mutel ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Wave Packet ◽  
Plasma Wave ◽  
Bright Spot ◽  
Deep Space ◽  
Good Correspondence ◽  
Auroral Kilometric Radiation ◽  
First Results ◽  
One To One ◽  
The Magnetic Field

Abstract. In this report we present the first results from the Cluster wideband plasma wave investigation. The four Cluster spacecraft were successfully placed in closely spaced, high-inclination eccentric orbits around the Earth during two separate launches in July – August 2000. Each spacecraft includes a wideband plasma wave instrument designed to provide high-resolution electric and magnetic field wave-forms via both stored data and direct downlinks to the NASA Deep Space Network. Results are presented for three commonly occurring magnetospheric plasma wave phenomena: (1) whistlers, (2) chorus, and (3) auroral kilometric radiation. Lightning-generated whistlers are frequently observed when the spacecraft is inside the plasmasphere. Usually the same whistler can be detected by all spacecraft, indicating that the whistler wave packet extends over a spatial dimension at least as large as the separation distances transverse to the magnetic field, which during these observations were a few hundred km. This is what would be expected for nonducted whistler propagation. No case has been found in which a strong whistler was detected at one spacecraft, with no signal at the other spacecraft, which would indicate ducted propagation. Whistler-mode chorus emissions are also observed in the inner region of the magnetosphere. In contrast to lightning-generated whistlers, the individual chorus elements seldom show a one-to-one correspondence between the spacecraft, indicating that a typical chorus wave packet has dimensions transverse to the magnetic field of only a few hundred km or less. In one case where a good one-to-one correspondence existed, significant frequency variations were observed between the spacecraft, indicating that the frequency of the wave packet may be evolving as the wave propagates. Auroral kilometric radiation, which is an intense radio emission generated along the auroral field lines, is frequently observed over the polar regions. The frequency-time structure of this radiation usually shows a very good one-to-one correspondence between the various spacecraft. By using the microsecond timing available at the NASA Deep Space Net-work, very-long-baseline radio astronomy techniques have been used to determine the source of the auroral kilometric radiation. One event analyzed using this technique shows a very good correspondence between the inferred source location, which is assumed to be at the electron cyclotron frequency, and a bright spot in the aurora along the magnetic field line through the source.Key words. Ionosphere (wave-particle interactions; wave propagation) – Magnetospheric physics (plasma waves and instabilities; instruments and techniques)

scholarly journals Correlation of morphological parameters of donkey from Austria

2021 ◽  
Vol 53 (2) ◽  
Author(s):  
Darko Drobnjak ◽  
Radka Vlaeva ◽  
Goran Stanišić ◽  
Radomir Mandić ◽  
Natalija Grittner ◽  
...  
Keyword(s):  
Body Length ◽  
Pearson Correlation ◽  
Good Reason ◽  
Statistical Correlation ◽  
Head Length ◽  
Chest Circumference ◽  
Average Height ◽  
Face Width ◽  
Equus Asinus ◽  
Almost All

The donkey, as a work animal, is gradually losing its value. Agriculture industrialization, mechanization of many processes on mountain and valley farms have lead to a reduction of donkey livestock. This reduction gives cause for concern, and is good reason to study all aspects of these domestic animals in order to revive its role, to restart livestock growth in its familiar habitats, and to introduce it into new environments. This study focuses on these aspects. The domestic donkey (Equus asinus) originated from Africa, and there are two kinds of African donkeys: Nubian and Somali. Their enormous, almost mystical, endurance is well known. There is no place in the world where a donkey is not able to perform the most difficult work, above all in transporting goods. A donkey has an amazing capability of stable movement through the most difficult places. For study sample consisted of 44 donkeys (28 males and 16 females) from Austria. The following morphometric parameters were analysed: height at the withers, height at the back, height of the croup, body length, chest depth, chest width, chest circumference anterior, chest circumference posterior, shin circumference, head length, skull length, face length, skull width, face width, length of ears. Measurements were performed using a ruler, tape measure and vernier callipers. The average height at the withers of males was 116.40 cm, ranging from 99.60 to 140.60 cm, while for females, the average was 102.38 cm, ranging from 90.50 to 125.70 cm. Body length of males was on average 121.85 cm with a standard deviation of 11.79, while the mean body length for females is 115.80 cm, with a range of 101.00 to 131.00 cm. Male head length ranged from 48.00 to 71.00 cm, with an average of 55.60 cm, while in females, head length was on average 50.06 cm, ranging from 43.00 to 56.00 cm. Using the Pearson correlation, a very significant or significant positive statistical correlation was observed between almost all parameters of males, while for females, Pearson correlation values had slightly different values than for males. There was no statistically significant correlation between chest width and anterior chest circumference with nearly any other parameters. For females, a negative correlation between the skull width and all other parameters was also observed.

Relative Contribution of ULF Waves and Whistler‐mode Chorus to the Radiation Belt Variation during the May 2017 Storm

2021 ◽  
Author(s):  
Naoko Takahashi ◽  
Kanako Seki ◽  
Mei‐Ching Fok ◽  
Yihua Zheng ◽  
Yoshizumi Miyoshi ◽  
...  
Keyword(s):  
Radiation Belt ◽  
Ulf Waves ◽  
Whistler Mode ◽  
Relative Contribution

scholarly journals Solitary potential structures observed in the magnetosheath by the Cluster spacecraft

2003 ◽  
Vol 10 (1/2) ◽  
pp. 3-11 ◽  
Author(s):  
J. S. Pickett ◽  
J. D. Menietti ◽  
D. A. Gurnett ◽  
B. Tsurutani ◽  
P. M. Kintner ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Time Series Data ◽  
Broad Band ◽  
Low Frequency ◽  
Bow Shock ◽  
Local Magnetic Field ◽  
Series Data ◽  
The Individual ◽  
Almost All ◽  
The Magnetic Field

Abstract. Bipolar pulses of ~ 25-100 µs in duration have been observed in the wave electric field data obtained by the Wideband plasma wave instrument on the Cluster spacecraft in the dayside magnetosheath. These pulses are similar in almost all respects to those observed on several spacecraft over the last few years. They represent solitary potential structures, and in this case, electron phase space holes. When the time series data containing the bipolar pulses on Cluster are transformed to the frequency domain by a windowed FFT, the pulses appear as typical broad-band features, extending from the low-frequency cutoff of the bandpass filter, ~ 1 kHz, up to as great as 20-40 kHz in some cases, with decreasing intensity as the frequency increases. The upper frequency cutoff of the broad band is an indication of the individual pulse durations (1/f). The solitary potential structures are detected when the local magnetic field is contained primarily in the spin plane, indicating that they propagate along the magnetic field. Their frequency extent and intensity seem to increase as the angle between the directions of the magnetic field and the plasma flow decreases from 90°. Of major significance is the finding that the overall profile of the broad-band features observed simultaneously by two Cluster spacecraft, separated by a distance of over 750 km, are strikingly similar in terms of onset times, frequency extent, intensity, and termination. This implies that the generation region of the solitary potential structures observed in the magnetosheath near the bow shock is very large and may be located at or near the bow shock, or be connected with the bow shock in some way.

scholarly journals The evolution of inverted magnetic fields through the inner heliosphere

2020 ◽  
Vol 494 (3) ◽  
pp. 3642-3655 ◽  
Author(s):  
Allan R Macneil ◽  
Mathew J Owens ◽  
Robert T Wicks ◽  
Mike Lockwood ◽  
Sarah N Bentley ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Radial Distance ◽  
Occurrence Rate ◽  
Slow Solar Wind ◽  
The Sun ◽  
Radial Evolution ◽  
In Transit ◽  
The Magnetic Field ◽  
Inner Heliosphere

ABSTRACT Local inversions are often observed in the heliospheric magnetic field (HMF), but their origins and evolution are not yet fully understood. Parker Solar Probe has recently observed rapid, Alfvénic, HMF inversions in the inner heliosphere, known as ‘switchbacks’, which have been interpreted as the possible remnants of coronal jets. It has also been suggested that inverted HMF may be produced by near-Sun interchange reconnection; a key process in mechanisms proposed for slow solar wind release. These cases suggest that the source of inverted HMF is near the Sun, and it follows that these inversions would gradually decay and straighten as they propagate out through the heliosphere. Alternatively, HMF inversions could form during solar wind transit, through phenomena such velocity shears, draping over ejecta, or waves and turbulence. Such processes are expected to lead to a qualitatively radial evolution of inverted HMF structures. Using Helios measurements spanning 0.3–1 au, we examine the occurrence rate of inverted HMF, as well as other magnetic field morphologies, as a function of radial distance r, and find that it continually increases. This trend may be explained by inverted HMF observed between 0.3 and 1 au being primarily driven by one or more of the above in-transit processes, rather than created at the Sun. We make suggestions as to the relative importance of these different processes based on the evolution of the magnetic field properties associated with inverted HMF. We also explore alternative explanations outside of our suggested driving processes which may lead to the observed trend.

On the absence of plasma wave emissions and the magnetic field orientation in the distant magnetosheath

1994 ◽  
Vol 21 (24) ◽  
pp. 2761-2764 ◽  
Author(s):  
F. V. Coroniti ◽  
E. W. Greenstadt ◽  
S. L. Moses ◽  
B. T. Tsurutani ◽  
E. J. Smith
Keyword(s):  
Magnetic Field ◽  
Plasma Wave ◽  
Field Orientation ◽  
Magnetic Field Orientation ◽  
The Magnetic Field

Effect of relativistic self-focusing on plasma wave excitation by a hollow Gaussian beam

2011 ◽  
Vol 77 (6) ◽  
pp. 777-784 ◽  
Author(s):  
RUCHIKA GUPTA ◽  
M. RAFAT ◽  
R. P. SHARMA
Keyword(s):  
Laser Beam ◽  
Gaussian Beam ◽  
Plasma Wave ◽  
Radial Distance ◽  
Laser Frequency ◽  
Pump Laser ◽  
Wave Excitation ◽  
Paraxial Ray Approximation ◽  
Self Focusing ◽  
Paraxial Ray

AbstractA paraxial-like approach has been invoked to understand the nature of propagation of a hollow Gaussian beam (HGB) propagating in plasma under the influence of relativistic non-linearity. In this approach, the parameters are expanded in terms of the radial distance from the maximum of irradiance rather than that from the axis. This paper investigates the excitation of plasma wave in a hot collision less plasma by HGB. On account of the × force, a plasma wave at 2ω0 (here, ω0 is the pump laser frequency) is generated. The solution of the HGB has been obtained within the paraxial ray approximation. Filamentary structures of the laser beam are observed due to relativistic non-linearity.

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