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)

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

scholarly journals Magnetic Field in the Proto-Planetary Nebula OH17.7–2.0

2003 ◽  
Vol 209 ◽  
pp. 143-144
Author(s):  
Indra Bains ◽  
Tim Gledhill ◽  
Jeremy Yates ◽  
Anita Richards
Keyword(s):  
Magnetic Field ◽  
Planetary Nebula ◽  
Field Structure ◽  
Radio Observations ◽  
Magnetic Field Structure ◽  
First Results ◽  
The Magnetic Field

We have used radio observations of OH masers in proto-planetary nebula (PPN) candidates to probe the magnetic field structure of these objects. Here we present the first results of our study, concerning the PPN OH17.7–2.0.

scholarly journals Properties of the Solar Filigree Structure

1974 ◽  
Vol 56 ◽  
pp. 45-47
Author(s):  
R. B. Dunn ◽  
J. B. Zirker ◽  
J. M. Beckers
Keyword(s):  
Magnetic Field ◽  
Fine Structure ◽  
Solar Physics ◽  
List Type ◽  
Blue Wing ◽  
One To One ◽  
Granulation Pattern ◽  
Network Patterns ◽  
The Magnetic Field ◽  
The Continuum

A number of observers have noted the presence of bright structures near the cores of the chromospheric rosettes when observed in the far wings of the Hα line (eg Hα ±7/8 Å). Dunn and Zirker observed these bright structures with the highest possible resolution using the Sacramento Peak vacuum solar telescope. They find that these bright regions exhibit a very intricate fine structure which can be followed out much further into the Hα line wing (eg Hα + 2 Å) and even into the continuum. They called this fine structure ‘solar filigree’, the name referring mainly to the collective appearance of the fine structure elements. The elements themselves appear as dot-like structures and frequently also as small wiggly structures called ‘crinkles’. The properties of the filigree structure are summarized as follows: (i)Size: Measured diameter of the crinkles and dots equals 0.25, 0.40 and 0.60″ at Hα + 2 Å, Hα ± 7/8 Å and Hα ±5/8 Å respectively. The telescope resolution equals 0.22″ so that at Hα + 2 Å the structure is extremely small. The drawings in Figure 1 show typical sizes of the crinkles and network patterns in the filigree.(ii)Contrast: Filigree is enhanced in the blue wing of the Hα line. Measured contrast, uncorrected for seeing, equals 5–10%.(iii)Relation to the Granulation: The filigree structures tend to lie between the granules. This is, however, not a strict rule. It seems that in the course of their lifetime the granules move the filigree structures around with velocities of about 1.5 km s-1. Some of the crinkles also seem to wash out temporarily until compressed again by a new granule. The detailed structure of the filigree, therefore, changes significantly over times comparable to the granule lifetime. The overall structure is, however, preserved over much longer periods of time. The granulation pattern when observed in the continuum well outside the Hα line appears very peculiar in that it has substantially decreased in contrast. It appears ‘soft’ similar to granulation washed-out by seeing. This abnormal granulation can be traced over long times (> 30 min) and coincides in location to the filigree location. It is, therefore, definitely real.(iv)Relation to the spicules: The filigree structure falls near the center of the Hα chromospheric rosettes. These rosettes consist of dark elongated mottles which should probably be identified with spicules. There is, therefore, at least a coarse relation between the occurrence of spicules and the filigree. There is no clear evidence that variations in the filigree pattern are related to the generation of spicules. Some spicules seem to originate from the spaces between the crinkles. Too few, however, to conclude a definite relation.(v)Relation to the magnetic field: Beckers studied the filigree with the Universal Birefringent Filter in the magnesium b1 and b2 lines. It is very well visible in the far wing of the lines (eg. b1 ±0.8 Å). When traced into the line core the structures increase somewhat in size, as they do in Hα, and form structures similar to, and perhaps identical with, the so-called photospheric network. In the magnetically sensitive b2 line one sees a one-to-one correspondence between these network structures and the magnetic field so that, at least in the layers seen near the core of the b2 line, there is a one-to-one correspondence between the filigree structures and the enhancements in the magnetic field. Simon and Zirker (Solar Physics, submitted for publication) using a spectrograph also found that the filigree occurs in regions of enhanced magnetic field. However, in contrast to the filter observations, they found the magnetic field regions to be much more diffuse (2–3″) so that there is not a one-to-one spatial correspondence between filigree and magnetic field structure.

scholarly journals Small scale observation of magnetopause motion: preliminary results of the INTERBALL project

1997 ◽  
Vol 15 (5) ◽  
pp. 562-569 ◽  
Author(s):  
J. Safrankova ◽  
G. Zastenker ◽  
Z. Nemecek ◽  
A. Fedorov ◽  
M. Simersky ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Time Resolution ◽  
Simultaneous Measurement ◽  
Small Scale ◽  
Satellite Measurements ◽  
Preliminary Results ◽  
Plasma Device ◽  
First Results ◽  
The Magnetic Field ◽  
Interball Project

Abstract. Two satellites of the INTERBALL project were launched on 3 August 1995. The main goals of the present paper are (1) to give a brief information about the VDP plasma device onboard the INTERBALL-1 satellite, (2) to present the Faradays cup data taken in different magnetospheric regions and (3) to expose first results of the two satellite measurements of the magnetopause motion. The presented data illustrate magnetopause crossings as seen by two satellites when separated by about ~ 1000 km. This separation combined with the Faraday's cup time resolution allows to estimate the velocity of the magnetopause and to reconstruct a possible structure of the boundary. Simultaneous measurement of the magnetic field supports the interpretation of the observed ion fluxes as a signature of the wavy motion of the boundary.

scholarly journals On dynamo action in the giant star Pollux: first results

2013 ◽  
Vol 9 (S302) ◽  
pp. 363-364 ◽  
Author(s):  
Ana Palacios ◽  
Allan Sacha Brun
Keyword(s):  
Magnetic Field ◽  
Magnetic Field Intensity ◽  
Rotation Period ◽  
Dynamo Action ◽  
Convective Envelope ◽  
Giant Star ◽  
First Results ◽  
The One ◽  
3D Mhd Simulation ◽  
The Magnetic Field

AbstractWe present preliminary results of a 3D MHD simulation of the convective envelope of the giant star Pollux for which the rotation period and the magnetic field intensity have been measured from spectroscopic and spectropolarimetric observations. This giant is one of the first single giants with a detected magnetic field, and the one with the weakest field so far. Our aim is to understand the development and the action of the dynamo in its extended convective envelope.

scholarly journals The surface and inner temperatures of magnetars

2012 ◽  
Vol 8 (S291) ◽  
pp. 386-388
Author(s):  
Z. F. Gao ◽  
N. Wang ◽  
Q. H. Peng
Keyword(s):  
Magnetic Field ◽  
Neutrino Emission ◽  
Effective Surface ◽  
X Ray ◽  
One To One ◽  
Field Decay ◽  
Neutrino Luminosity ◽  
The Magnetic Field

AbstractAssuming that the timescale of the magnetic field decay is approximately equal to that of the stellar cooling via neutrino emission, we obtain a one-to-one relationship between the effective surface thermal temperature and the inner temperature. The ratio of the effective neutrino luminosity to the effective X-ray luminosity decreases with decaying magnetic field.

scholarly journals MHD simulations of cool core clusters

2008 ◽  
Vol 4 (S259) ◽  
pp. 565-566
Author(s):  
Frederico Stasyszyn ◽  
Klaus Dolag
Keyword(s):  
Magnetic Field ◽  
Core Region ◽  
Thermal Pressure ◽  
Magnetic Field Profile ◽  
Mhd Simulations ◽  
Reference Cluster ◽  
First Results ◽  
Smoothed Particle ◽  
The Magnetic Field

AbstractUsing Smoothed Particle Magneto Hydrodynamics (Dolag & Stasyszyn), we study the effects of magnetic fields in galaxy clusters with the aim to infer their dynamical role within the cool core region. Therefore we we investigate the role of regularization as well as divergence cleaning schemes (Stasyszyn & Dolag 2009). We run cosmological simulations of a reference cluster in order to evaluate our various implementation in a realistic scenario. The preliminary results indicate that the final magnetic field profile in the simulations depends only on the amount of artificial dissipation, but not in the amount of numerical div(B) present in the different implementation. We also present first results from simulations which are including radiative cooling and star formation. Even at the this low resolution we find a strong additional amplification of the magnetic field within the cool core region indicating that magnetic pressure could become comparable to the thermal pressure in theses regimes.

The magnetic field experiment IMSC and its data processing onboard DEMETER: Scientific objectives, description and first results

2006 ◽  
Vol 54 (5) ◽  
pp. 441-455 ◽  
Author(s):  
M. Parrot ◽  
D. Benoist ◽  
J.J. Berthelier ◽  
J. Błęcki ◽  
Y. Chapuis ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Data Processing ◽  
Field Experiment ◽  
First Results ◽  
The Magnetic Field ◽  
Magnetic Field Experiment

scholarly journals Search for surface magnetic fields in Mira stars: first results on χ Cyg

2013 ◽  
Vol 9 (S302) ◽  
pp. 385-388 ◽  
Author(s):  
Agnès Lèbre ◽  
Michel Aurière ◽  
Nicolas Fabas ◽  
Denis Gillet ◽  
Fabrice Herpin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Zeeman Effect ◽  
Stellar Atmosphere ◽  
Asymptotic Giant Branch ◽  
Photospheric Level ◽  
First Results ◽  
Weak Surface ◽  
Surface Fields ◽  
The Magnetic Field

AbstractSo far, surface magnetic fields have never been reported on Mira stars, while observational facilities allowing detection and measurement of weak surface fields through the Zeeman effect have become available. Then, in order to complete the knowledge of the magnetic field and of its influence during the transition from Asymptotic Giant Branch (AGB) to Planetary Nebulae (PN) stages, we have undertaken a search for magnetic fields at the surface of Miras. We present the first spectropolarimetric observations (performed with the Narval instrument at Télescope Bernard Lyot-TBL, Pic du Midi, France) of the S-type Mira star χ Cyg. We have detected a polarimetric signal in the Stokes V spectra and we have established its Zeeman origin. We claim that it is likely to be related to a weak magnetic field present at the photospheric level and in the lower part of the stellar atmosphere. The origin of this magnetic field is discussed in the framework of shock waves periodically propagating throughout the atmosphere of a Mira.

scholarly journals The role of magnetic energy on plasma localization during the glow discharge under reduced pressure

Nukleonika ◽  
2016 ◽  
Vol 61 (2) ◽  
pp. 191-194 ◽  
Author(s):  
Rafal Chodun ◽  
Katarzyna Nowakowska-Langier ◽  
Krzysztof Zdunek ◽  
Sebastian Okrasa
Keyword(s):  
Magnetic Field ◽  
Glow Discharge ◽  
Breakdown Voltage ◽  
Magnetic Energy ◽  
Minimum Energy ◽  
Electrode System ◽  
Reduced Pressure ◽  
First Results ◽  
Paschen Curve ◽  
The Magnetic Field

Abstract In this work, we present the first results of our research on the synergy of fields, electric and magnetic, in the initiation and development of glow discharge under reduced pressure. In the two-electrode system under reduced pressure, the breakdown voltage characterizes a minimum energy input of the electric field to initiate and sustain the glow discharge. The glow discharge enhanced by the magnetic field applied just above the surface of the cathode influences the breakdown voltage decreasing its value. The idea of the experiment was to verify whether the contribution of potential energy of the magnetic field applied around the cathode is sufficiently effective to locate the plasma of glow discharge to the grounded cathode, which, in fact, is the part of a vacuum chamber wall (the anode is positively biased in this case). In our studies, we used the grounded magnetron unit with positively biased anode in order to achieve favorable conditions for the deposition of thin films on fibrous substrates such as fabrics for metallization, assuming that locally applied magnetic field can effectively locate plasma. The results of our studies (Paschen curve with the participation of the magnetic field) seem to confirm the validity of the research assumption. What is the most spectacular - the glow discharge was initiated between introduced into the chamber anode and the grounded cathode of magnetron ‘assisted’ by the magnetic field (discharge did not include the area of the anode, which is a part of the magnetron construction).

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