Author name code: haerendel
ADS astronomy entries on 2022-09-14
author:"Haerendel, Gerhard"
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Title: The Onset of a Substorm and the Mating Instability
Authors: Haerendel, Gerhard; Frey, Harald
Bibcode: 2021JGRA..12629492H
Altcode:
The paper underlines the view that the appearance of beading and its
nonlinear growth in the onset arc occurs independently from the onset
of reconnection in the tail at about 20 RE. Both events
follow from an extreme thinning of the central current sheet of the
tail at the end of the growth phase. Subsequently, we concentrate on
the processes connected with the onset arc breakup. Its origin lies in
the instability of a high-beta plasma layer building up at the outer
boundary of the dipolar magnetosphere during the substorm growth phase,
the growth phase arc (GPA) being the ionospheric trace. The observation
of auroral streamers triggering the onset arc instability lets us
analyze what is known about auroral streamers with strong support
from high-resolution videos of two substorm onsets. We conclude that
they may be low-entropy content bubbles with a balanced field-aligned
current system, framing a flow channel. However, there are unresolved
questions. The visible streamer is identified as an Alfvénic arc. In
searching for a mechanism by which a streamer bubble lining up along
the GPA can trigger the instability, we are led to the recognition
that an entirely new non-MHD process must be at work. Taking also into
account the surprising fact that the beads are moving oppositely to the
convection in GPA and auroral streamer, we postulate the appearance of
a new current system in the gap between the two. What happens can be
described as the mating of two current sheets, which were completely
separated before. It breaks the stability of the high-beta plasma layer
and channels the release and conversion of free internal energy. For
this reason, we name the process mating instability. A physical analysis
of this process shows consistency with detailed features exhibited by
the two videos
Title: Results of the Electron Drift Instrument on Cluster
Authors: Paschmann, G.; Quinn, J. M.; Torbert, R. B.; McIlwain, C. E.;
Vaith, H.; Haaland, S.; Matsui, H.; Kletzing, C. A.; Baumjohann, W.;
Haerendel, G.
Bibcode: 2021JGRA..12629313P
Altcode:
The electron drift instrument (EDI) on Cluster pioneered a new method
of measuring electric fields, using a beam of electrons to sample the
drift velocity over a km-scale gyro orbit. The technique is especially
well suited to measuring weak, sub-mV/m, convection fields due to
its sensitivity (to both components in the plane perpendicular to B)
and because it is unaffected by the anomalous local electric fields
that are generated by spacecraft-plasma interactions. Because EDI
requires exquisite beam pointing with active tracking of the firing
directions, measurements are less regular, or even impossible, in
rapidly varying electric and magnetic fields; however, in the many
regimes where tracking is successful the resulting measurements are
reliably accurate. We review the EDI technique and instrumentation,
and present six areas of investigation using Cluster data: (1)
Detailed comparisons of EDI data with the electric field and waves
double probe measurements show excellent agreement in many cases but
identify large discrepancies where strong ion outflow in the polar
regions creates local spacecraft wake effects. (2) The wake effect is
exploited to infer quantitative ion outflow rates. Detailed convection
patterns in the (3) polar cap, (4) lobe, and (5) inner magnetosphere
are derived under various driver conditions using statistical analyses
of long term measurements during the Cluster mission. (6) EDI's large
geometric-factor detector is used for extremely high time resolution
measurements of electrons at a specified energy and pitch angle.
Title: Auroral Arcs: The Fracture Theory Revisited
Authors: Haerendel, Gerhard
Bibcode: 2021JGRA..12628194H
Altcode:
The fracture theory for auroral arcs, developed by the author since
1980, compares the decoupling of the magnetic field from the ionosphere
by the auroral acceleration region (AAR) with the breaking of a solid
rod. In the latter elastic energy stored by the bending is converted
into kinetic energy of the stress release motion. Similarly, magnetic
energy stored in sheared magnetic fields is temporarily converted into
stress release motions and finally transported as Poynting flux into the
AAR. The fracture theory has been especially applied to arcs embedded in
the convection of the evening auroral oval. The present study subjects
the different steps in the fracture process to a critical analysis in
the light of new physical insights. This boils down to a revision of the
illustrating cartoon used in the earlier publications, without having
affecting the quantitative evaluations. The first revision concerns
the height extent of the AAR. It must be largely increased. The second
revision introduces a nearly 2 D magnetohydrodynamics (MHD) turbulence
into the state of the AAR. This is supported by high altitude electric
field data and leads to new view of auroral rays. The third revision
describes the transition from the AAR to the ionosphere as structured by
so called potential fingers, which contain substantial fractions of the
total field parallel potential drop. The most important modification
pertains to the average U shaped potential of a spontaneously
propagating AAR. While the leading edge of the auroral current sheet
is structured by stress release motions, the reverse flow in the rear
section escapes simple interpretation. It is proposed that this flow
is driven by a turbulent transport of reversed momentum from front
to rear in response to the incompressibility of the magnetic field in
the acceleration region. This leads to a revision of the field aligned
currents and wavefield in the rear of the arc.
Title: Expanding Auroral Loops
Authors: Haerendel, Gerhard
Bibcode: 2019JGRA..124.8629H
Altcode:
A new scenario is presented for the energy supply to the auroral
acceleration process. It applies to auroral arcs, which are propagating
into regions of magnetic fields with shears with lower than those
existing behind the arc. This pertains in particular to expanding
U-loops or other active protrusions. A Poynting flux, emerging out of
the interior of the associated current system with strongly sheared
field, flows into the auroral acceleration region or fracture zone. One
half of the energy is consumed by the acceleration process. The other
half flows (mainly upward) into the current sheet and is expended
by shearing the newly incorporated field into the direction of the
internal field. This is enabled by the magnetic connectivity being
broken inside the region of parallel electric potential drops. The
latter are formally attributed to the presence of an anomalous
resistivity in the auroral current sheet. Simple relations describe
the energy transport and consumption. An important quantity is the
width of the arc. It follows from the balance of the energy transport
inside and out of the acceleration region. Since the process involves
first breaking of the field lines, to be followed by building up shear
stresses, the name "constructive magnetic fractures" has been chosen
for distinguishing it from "destructive fractures," which applies to
embedded arcs. Which of these two processes is acting can be easily
recognized by the direction of motion of the auroral rays or folds,
whether they are opposed to or in parallel with the convective flow
behind the arc.
Title: Experiments with Plasmas artificially injected into near-Earth
Space
Authors: Haerendel, Gerhard
Bibcode: 2019FrASS...6...29H
Altcode:
Plasma injection experiments in space are being ordered according to
five aspects: (1) Diagnostics of electric fields, (2) Coupling to the
ionosphere, (3) Interactions with the solar wind, (4) Modification
experiments, and (5) Special physical processes. Historically first
were releases of neutral gases with the aim to measure atmospheric
parameters. They were soon followed by plasma injections applied to the
measurement of plasma flows and parallel electric fields. Long-range
coupling to the environment was a most important aspect of the plasma
releases. It concerned, on the one hand, the need for corrections of the
derived diagnostic parameters and, on the other hand, the understanding
of the formation of the ubiquitous striations and deformations of
the plasma clouds. A special application was the investigation of
cometary interactions by releases in the solar wind. Modification
experiments in the ionosphere were done intentionally or occurred
as byproducts of rocket launches or other activities. A particular
goal was to trigger natural large-scale ionospheric instabilities
like equatorial spread F in order to improve the understanding of the
natural phenomena. Large-scale plasma injections in the magnetosphere
have been performed in order to change the conditions of wave-particle
interactions and potentially trigger observable effects. Special
goals were so-called skidding experiments and testing Alfvén's
critical ionization velocity effect. In this review we will emphasize
the principle objectives and illustrate the results from selected
experiments.
Title: Dying Flow Bursts as Generators of the Substorm Current Wedge
Authors: Haerendel, Gerhard
Bibcode: 2018cosp...42E1345H
Altcode:
Many theories or conjectures exist on the driver of the substorm current
wedge, e.g. rerouting of the tail current, current disruption, flow
braking, vortex formation, and current sheet collapse. Magnitude,
spatial scale, and temporal development of the related magnetic
perturbations suggest that the generator is related to the interaction
of the flow bursts with the dipolar magnetosphere after onset of
reconnection in the near-Earth tail. The question remains how much
of the energy feeding the wedge current is derived from flow braking
and how much is contributed by the internal energy of the arriving
plasma. In this presentation I argue that after flow braking the plasma
attaching to the outer magnetosphere still contributes to current
generation. The generator current is the grad-B current at the outer
boundary of high-beta plasma compressed by the contracting magnetic
field. It needs the sequential arrival of several flow bursts to
account for duration and magnitude of the ionospheric closure current.
Title: Reconnection mediated by Magnetic Fractures and the Solar Flare
Authors: Haerendel, Gerhard
Bibcode: 2018cosp...42E1346H
Altcode:
Reconnection of sheared magnetic fields is commonly treated by regarding
the component perpendicular to the anti-parallel components as a
largely inert guide field. In this paper an alternative is proposed in
which the free energy residing in the shear field is being converted
prior to reconnection. This happens in high-density, dissipative
current sheets bordering the reconnection site. A global scenario
is presented in which low-intensity currents out of the photosphere
are converging into the narrow, high-intensity currents at high
altitude. This is enabled by the obliqueness of the latter. The very
short time-scale of the energy conversion causes a lateral propagation
of the current sheets. In a quasi-stationary situation, it balances the
reconnection rate, which turns out to be much lower than in guide-field
approaches. Another important consequence of the obliqueness is the
field-parallel emission of runaway electrons. Accelerated up to tens
of keV, they are possibly important contributors to the production
of hard X-rays during the impulsive phase of a flare, however only in
areas of upward directed currents. Quantitative evaluation of the model
predicts various potentially observable properties, such as width and
propagation speed of the generated flare ribbons, spatial dependences
of the electron spectrum, size of the area of energy deposition,
and successive decrease of the shear angle between conjugate foot
points. The presented theoretical model can account for the observed
brightness asymmetry of flare ribbons with respect to the direction
of the vertical currents.
Title: Reconnection mediated by Magnetic Fractures and the Solar Flare
Authors: Haerendel, Gerhard
Bibcode: 2018tess.conf11404H
Altcode:
Reconnection of sheared magnetic fields is commonly treated by regarding
the component perpendicular to the anti-parallel components as a
largely inert guide field. In this paper an alternative is proposed in
which the free energy residing in the shear field is being converted
prior to reconnection. This happens in high-density, dissipative
current sheets bordering the reconnection site. A global scenario
is presented in which low-intensity currents out of the photosphere
are converging into the narrow, high-intensity currents at high
altitude. This is enabled by the obliqueness of the latter. The very
short time-scale of the energy conversion causes a lateral propagation
of the current sheets. In a quasi-stationary situation, it balances the
reconnection rate, which turns out to be much lower than in guide-field
approaches. Another important consequence of the obliqueness is the
field-parallel emission of runaway electrons. Accelerated up to tens
of keV, they are possibly important contributors to the production
of hard X-rays during the impulsive phase of a flare, however only in
areas of upward directed currents. Quantitative evaluation of the model
predicts various potentially observable properties, such as width and
propagation speed of the generated flare ribbons, spatial dependences
of the electron spectrum, size of the area of energy deposition,
and successive decrease of the shear angle between conjugate foot
points. The presented theoretical model can account for the observed
brightness asymmetry of flare ribbons with respect to the direction
of the vertical currents.
Title: Reconnection Mediated by Magnetic Fractures and the Solar Flare
Authors: Haerendel, Gerhard
Bibcode: 2018ApJ...855...95H
Altcode:
Reconnection of sheared magnetic fields is commonly treated by regarding
the component perpendicular to the antiparallel components as a largely
inert guide field. In this paper an alternative is proposed in which
the free energy residing in the shear field is being converted prior to
reconnection. This happens in high-density, dissipative current sheets
bordering the reconnection site. A global scenario is presented in which
low-intensity currents out of the photosphere are converging into the
narrow, high-intensity currents at high altitude. This is enabled by
the obliqueness of the latter. The very short timescale of the energy
conversion causes a lateral propagation of the current sheets. In a
quasi-stationary situation, it balances the reconnection rate, which
turns out to be much lower than in guide-field approaches. Another
important consequence of the obliqueness is the field-parallel emission
of runaway electrons. Accelerated up to tens of keV, they are possibly
important contributors to the production of hard X-rays during the
impulsive phase of a flare, but only in areas of upward-directed
currents. Quantitative evaluation of the model predicts various
potentially observable properties, such as width and propagation speed
of the generated flare ribbons, spatial dependences of the electron
spectrum, size of the area of energy deposition, and successive
decrease of the shear angle between conjugate footpoints. The presented
theoretical model can account for the observed brightness asymmetry
of flare ribbons with respect to the direction of the vertical currents.
Title: Evidence for Field-parallel Electron Acceleration in Solar
Flares
Authors: Haerendel, G.
Bibcode: 2017ApJ...847..113H
Altcode:
It is proposed that the coincidence of higher brightness and upward
electric current observed by Janvier et al. during a flare indicates
electron acceleration by field-parallel potential drops sustained by
extremely strong field-aligned currents of the order of 104
A m-2. A consequence of this is the concentration of the
currents in sheets with widths of the order of 1 m. The high current
density suggests that the field-parallel potential drops are maintained
by current-driven anomalous resistivity. The origin of these currents
remains a strong challenge for theorists.
Title: Field-parallel Acceleration: Comment on the Paper
“Electric Currents on the Flare Ribbons: Observations
and Standard Model” by Janvier et al. (2014, ApJ, 788, 60)
Authors: Haerendel, G.
Bibcode: 2017ApJ...847..143H
Altcode:
It is proposed that the coincidence of higher brightness and upward
electric current observed by Janvier et al. during a flare indicates
electron acceleration by field-parallel potential drops sustained
by extremely strong field-aligned currents of order 104
A m-2. A few consequences are discussed here.
Title: Joint two-point observations of LF-waves at
67P/Churyumov—Gerasimenko
Authors: Heinisch, Philip; Auster, H. -U.; Richter, I.; Haerendel,
G.; Apathy, I.; Fornacon, K. -H.; Cupido, E.; Glassmeier, K. -H.
Bibcode: 2017MNRAS.469S..68H
Altcode:
After the Rosetta mission reached its target comet
67P/Churyumov-Gerasimenko, the lander Philae touched down on the surface
on 2014 November 12. During the First-Science-Sequence after touchdown
the lander magnetometer ROMAP and the orbiter magnetometer RPC-MAG
were both operating simultaneously which allowed for in situ magnetic
two-point observations of the comet. This analysis aims at determining
the characteristics of the low-frequency plasma waves present in the
nucleus surface region, including frequency, propagation direction
and velocity. These waves propagate predominantly from the nucleus
towards the Sun with a mean phase velocity of ∼5.3 km s-1,
a wavelength of ∼660 km and an average frequency of ∼8 mHz.
Title: Mechanical and electrostatic experiments with dust particles
collected in the inner coma of comet 67P by COSIMA onboard Rosetta
Authors: Hilchenbach, Martin; Fischer, Henning; Langevin, Yves;
Merouane, Sihane; Paquette, John; Rynö, Jouni; Stenzel, Oliver;
Briois, Christelle; Kissel, Jochen; Koch, Andreas; Schulz, Rita;
Silen, Johan; Altobelli, Nicolas; Baklouti, Donia; Bardyn, Anais;
Cottin, Herve; Engrand, Cecile; Fray, Nicolas; Haerendel, Gerhard;
Henkel, Hartmut; Höfner, Herwig; Hornung, Klaus; Lehto, Harry;
Mellado, Eva Maria; Modica, Paola; Le Roy, Lena; Siljeström, Sandra;
Steiger, Wolfgang; Thirkell, Laurent; Thomas, Roger; Torkar, Klaus;
Varmuza, Kurt; Zaprudin, Boris
Bibcode: 2017RSPTA.37560255H
Altcode:
The in situ cometary dust particle instrument COSIMA (COmetary
Secondary Ion Mass Analyser) onboard ESA's Rosetta mission has
collected about 31 000 dust particles in the inner coma of comet
67P/Churyumov-Gerasimenko since August 2014. The particles are
identified by optical microscope imaging and analysed by time-of-flight
secondary ion mass spectrometry. After dust particle collection by
low speed impact on metal targets, the collected particle morphology
points towards four families of cometary dust particles. COSIMA is
an in situ laboratory that operates remotely controlled next to the
comet nucleus. The particles can be further manipulated within the
instrument by mechanical and electrostatic means after their collection
by impact. The particles are stored above 0°C in the instrument and the
experiments are carried out on the refractory, ice-free matter of the
captured cometary dust particles. An interesting particle morphology
class, the compact particles, is not fragmented on impact. One of
these particles was mechanically pressed and thereby crushed into large
fragments. The particles are good electrical insulators and transform
into rubble pile agglomerates by the application of an energetic indium
ion beam during the secondary ion mass spectrometry analysis. This
article is part of the themed issue 'Cometary science after Rosetta'.
Title: Shock aurora: Field-aligned discrete structures moving along
the dawnside oval
Authors: Zhou, Xiaoyan; Haerendel, Gerhard; Moen, Jøran I.;
Trondsen, Espen; Clausen, Lasse; Strangeway, Robert J.; Lybekk,
Bjørn; Lorentzen, Dag A.
Bibcode: 2017JGRA..122.3145Z
Altcode:
Generated by interplanetary shocks or solar wind pressure pulses, shock
aurora has transient, global, and dynamic significances and provides
a direct manifestation of the solar wind-magnetosphere-ionosphere
interaction. As a part of a series of studies of the shock aurora,
this paper focuses on the interaction at the morning magnetopause
and its auroral manifestation at 06 magnetic local time, where the
velocity and magnetic field shears dominate the interaction. Flow
shears can generate wave-like structures inside a viscous boundary
layer or even larger-scale vortices. These structures couple to the
ionosphere via quasi-static field-aligned currents or via kinetic
Alfvén waves. Potential drops along field-aligned filaments may be
generated accelerating electrons to form auroral manifestations of
the structures. A shock aurora event at dawnside is used to test this
scenario. The findings include moving auroral streaks/rays that have
a vertical profile from red (at 250 km altitude) to purple (at 100
km). The streaks moved antisunward along the poleward boundary of the
oval at an ionospheric speed of 3 km s-1. It was mapped to
the magnetopause flank at 133 km s-1, which was consistent
with the observed speed of the magnetopause surface waves generated by
the Kelvin-Helmholtz instability. The calculated field-aligned potential
drop using Haerendel's analytic model was 5 kV that reasonably explained
the observations. The results support the above scenario and reveal
that magnetic and velocity shears at the flanks of the magnetospause
may be the main cause of the fast moving shock aurora streaks.
Title: ROSETTA/COSIMA at comet 67P/Churyumov-Gerasimenko - 2 years
of in-situ dust analysis
Authors: Schulz, Rita; Hilchenbach, Martin; Kissel, Jochen; Langevin,
Yves; Briois, Christelle; Koch, Andreas; Silen, Johan; Baklouti, Donia;
Bardyn, Anais; Cottin, Herve'; Engrand, Cecile; Fischer, Henning; Fray,
Nicolas; Glasmachers, Albrecht; Gruen, Eberhard; Haerendel, Gerhard;
Henkel, Hartmut; Höfner, Hervig; Hornung, Klaus; Jessberger, Elmar;
Lehto, Harry J.; Letho, Kirsi; Ligier, Nicolas; Merouane, Sihane;
Orthous-Daunay, Francois-Regis; Paquette, John; Raulin, F.; Le Roy,
Léna; Rynö, Jouni; Siljeström, Sandra; Steiger, Wolfgang; Stenzel,
Oliver; Stephan, Thomas; Thirkell, Laurent; Thomas, Roger; Torkar,
Klaus; Varmuza, Kurt; Wanczek, Karl-Peter; Zaprudin, Boris
Bibcode: 2016DPS....4811605S
Altcode:
In August 2014 the ROSETTA spacecraft rendezvoused with comet
67P/Churyumov-Gerasimenko and escorted it for more than 2 years
along its orbit around the Sun from 4 AU preperihelion to 4 AU
postperihelion. During this time the COSIMA instrument (COmetary
Secondary Ion Mass Analyser) onboard ROSETTA collected more than
25,000 dust particles in the vicinity of the comet nucleus. All these
particles were collected on a number of specially designed metal target
plates which were regularly imaged with a microscope (14 µm pixel/pixel
resolution, 14mm x 14mm FOV) enabling the analysis of their individual
morphologies, certain physical properties, e.g. tensile strength,
albedo, as well as the overall flux and size distribution of the dust
entering the COSIMA instrument. The images were also used to choose
which of the particles shall go through compositional measurements with
the time-of-flight mass spectrometer (sometimes repeated at a later
time). All these investigations were done over 2 years. This allows to
study the compositional and morphological differences of the particles
collected at the various sections of the pre- and postperihelion orbit,
the evolution of the morphology of the particles on the target plate
with time, and the search for spatial heterogeneity of the composition
within a particle by taking mass spectra at different locations on the
same particle. An overview will be given on the available data and the
results obtained so far in view to the analysis of dust composition and
morphology, as well as dust flux and size distribution along the orbit.
Title: High-molecular-weight organic matter in the particles of
comet 67P/Churyumov-Gerasimenko
Authors: Fray, Nicolas; Bardyn, Anaïs; Cottin, Hervé; Altwegg,
Kathrin; Baklouti, Donia; Briois, Christelle; Colangeli, Luigi;
Engrand, Cécile; Fischer, Henning; Glasmachers, Albrecht; Grün,
Eberhard; Haerendel, Gerhard; Henkel, Hartmut; Höfner, Herwig;
Hornung, Klaus; Jessberger, Elmar K.; Koch, Andreas; Krüger,
Harald; Langevin, Yves; Lehto, Harry; Lehto, Kirsi; Le Roy, Léna;
Merouane, Sihane; Modica, Paola; Orthous-Daunay, François-Régis;
Paquette, John; Raulin, François; Rynö, Jouni; Schulz, Rita;
Silén, Johan; Siljeström, Sandra; Steiger, Wolfgang; Stenzel,
Oliver; Stephan, Thomas; Thirkell, Laurent; Thomas, Roger; Torkar,
Klaus; Varmuza, Kurt; Wanczek, Karl-Peter; Zaprudin, Boris; Kissel,
Jochen; Hilchenbach, Martin
Bibcode: 2016Natur.538...72F
Altcode:
The presence of solid carbonaceous matter in cometary dust was
established by the detection of elements such as carbon, hydrogen,
oxygen and nitrogen in particles from comet 1P/Halley. Such matter
is generally thought to have originated in the interstellar medium,
but it might have formed in the solar nebula—the cloud of gas and
dust that was left over after the Sun formed. This solid carbonaceous
material cannot be observed from Earth, so it has eluded unambiguous
characterization. Many gaseous organic molecules, however, have
been observed; they come mostly from the sublimation of ices at the
surface or in the subsurface of cometary nuclei. These ices could
have been formed from material inherited from the interstellar medium
that suffered little processing in the solar nebula. Here we report
the in situ detection of solid organic matter in the dust particles
emitted by comet 67P/Churyumov-Gerasimenko the carbon in this organic
material is bound in very large macromolecular compounds, analogous
to the insoluble organic matter found in the carbonaceous chondrite
meteorites. The organic matter in meteorites might have formed in
the interstellar medium and/or the solar nebula, but was almost
certainly modified in the meteorites’ parent bodies. We conclude
that the observed cometary carbonaceous solid matter could have the
same origin as the meteoritic insoluble organic matter, but suffered
less modification before and/or after being incorporated into the comet.
Title: Composition of Dust Particles Collected in the Inner Coma of
Comet 67P/Churymumo-Gerasimenko by Rosetta
Authors: Hilchenbach, M.; Kissel, J.; Langevin, Y.; Briois, C.; Koch,
A.; Schulz, R.; Silen, J.; Altobelli, N.; Altwegg, K.; Baklouti, D.;
Bardyn, A.; Colangeli, L.; Cottin, H.; Engrand, C.; Fischer, H.; Fray,
N.; Glasmachers, A.; Grün, E.; Haerendel, G.; Henkel, H.; Höfner,
H.; Hornung, K.; Jessberger, E. -K.; Lehto, H.; Ligier, N.; Martin,
P.; Merouane, S.; Orthous-Daunay, F. -R.; Paquette, J.; Raulin,
F.; Le Roy, L.; Rynö, J.; Silieström, S.; Steiger, W.; Stenzel,
O.; Stephan, T.; Thirkell, L.; Thomas, R.; Torkar, K.; Varmuza, K.;
Wanczek, K. -P.; Zaprudin, B.
Bibcode: 2016LPICo1921.6116H
Altcode:
The dust particle instrument COSIMA - COmetary Secondary Ion Mass
Analyser - on board ESA’s ROSETTA mission is collecting and
analyzing dust particles in the inner coma of Jupiter-family comet
67P/Churyumov-Gerasimenko.
Title: Solar Aurora and a White Light Flare
Authors: Haerendel, Gerhard
Bibcode: 2016cosp...41E.784H
Altcode:
A white light flare analyzed by Krucker et al. (2011) poses a
severe challenge to the solar physicist because of the high energy
fluxes implied by a hitherto not achieved spatial resolution of
simultaneous observations with Hinode and RHESSI. A scenario based
on the auroral acceleration mechanism applied to flare conditions,
'Solar Aurora', is able to reproduce the observations, but implies
several far-reaching assumptions on the mechanism as well as on the
environmental parameters. Unavoidable consequences exist with regard to
the spatial and temporal scales. They are extremely short because of
the high density of the corona and the need for an energy conversion
process involving some kind of anomalous resistivity, i.e. extremely
high electric current densities. A further postulate is that of
spontaneous propagation of an energy conversion front (ENF), once
established, in three dimensions. It is assumed that about one half of
the converted energy appears in form of runaway electrons. Obliqueness
of the ENFs prevents the existence of a return current problem for the
emerging runaway electrons. The key flare parameters are formulated
quantitatively in terms of the environmental properties. Transverse
length scales turn out to be in the ten centimeter range, time-scales
in the range of one millisecond. The energy conversion occurs in 10E3
-10E4 ENFs just above the transition region in a background field of
the order of 2000 G. Observational consequences are being discussed.
Title: Dying Flow Bursts as Generators of the Substorm Current Wedge
Authors: Haerendel, Gerhard
Bibcode: 2016cosp...41E.783H
Altcode:
Many theories or conjectures exist on the driver of the substorm current
wedge, e.g. rerouting of the tail current, current disruption, flow
braking, vortex formation, and current sheet collapse. Magnitude,
spatial scale, and temporal development of the related magnetic
perturbations suggest that the generator is related to the interaction
of the flow bursts with the dipolar magnetosphere after onset of
reconnection in the near-Earth tail. The question remains whether it is
the flow energy that feeds the wedge current or the internal energy of
the arriving plasma. In this presentation I argue for the latter. The
current generation is attributed to the force exerted by the dipolarized
magnetic field of the flow bursts on the preceding layer of high-beta
plasma after flow braking. The generator current is the grad-B current
at the outer boundary of the compressed high-beta plasma layers. It
needs the sequential arrival of several flow bursts to account for
duration and magnitude of the ionospheric closure current.
Title: Two-Point observations of low-frequency waves at 67P/C-G by
ROMAP and RPC-MAG
Authors: Heinisch, Philip; Auster, Hans-Ulrich; Richter, Ingo;
Haerendel, Gerhard; Götz, Charlotte; Apathy, Istvan; Berghofer,
Gerhard; Fornacon, Karl-Heinz; Glassmeier, Karl-Heinz
Bibcode: 2016EGUGA..18.8622H
Altcode:
During PHILAE's First Science Sequence (FSS) the onboard ROMAP
magnetometer and the RPC-MAG magnetometer of the ROSETTA orbiter were
operating simultaneously for about 14h. These measurements provided the
unique possibility to analyze the spatial and temporal evolution of
waves in the magnetic field of the comet boundary region. An initial
analysis revealed, that neither the amplitude nor the direction of
these waves depend on the day-night cycle at the landing site, but
rather on the outgassing of the nucleus. Based on a minimum-variance
analyses two different types of waves could be identified. These mostly
compressible waves have a propagation direction from the comet tail
to the front with a velocity between 2km/s and 10km/s.
Title: Refractory Elements from High Resolution Mass Spectra of 67P
Particles as Found by Rosetta/COSIMA
Authors: Stenzel, O. J.; Hilchenbach, M.; Kissel, J.; Langevin, Y.;
Briois, C.; Koch, A.; Schulz, R.; Silen, J.; Altobelli, N.; Altwegg,
K.; Colangeli, L.; Cottin, H.; Baklouti, D.; Bardyn, A.; Engrand,
C.; Fischer, H.; Fray, N.; Glasmachers, A.; Grün, E.; Haerendel,
G.; Henkel, H.; Höfner, H.; Hornung, K.; Jessberger, E. K.;
Lehto, H.; Lehto, K.; Ligier, N.; Lin, Z.; Martin, P.; Merouane, S.;
Orthous-Daunay, F. R.; Paquette, J.; Raulin, F.; Revillet, C.; Le Roy,
L.; Rynö, J.; Siljeström, S.; Steiger, W.; Stephan, T.; Thirkell,
L.; Thomas, R.; Torkar, K.; Varmuza, K.; Wanczek, K. -P.; Zaprudin, B.
Bibcode: 2016LPI....47.1934S
Altcode:
The dust composition analyzer COSIMA collects and analyzes dust
particles in the coma of comet 67P. We report on the refractory elements
in these particles.
Title: Comet 67P/Churyumov-Gerasimenko: Close-up on Dust Particle
Fragments
Authors: Hilchenbach, M.; Kissel, J.; Langevin, Y.; Briois, C.;
von Hoerner, H.; Koch, A.; Schulz, R.; Silén, J.; Altwegg, K.;
Colangeli, L.; Cottin, H.; Engrand, C.; Fischer, H.; Glasmachers,
A.; Grün, E.; Haerendel, G.; Henkel, H.; Höfner, H.; Hornung,
K.; Jessberger, E. K.; Lehto, H.; Lehto, K.; Raulin, F.; Le Roy,
L.; Rynö, J.; Steiger, W.; Stephan, T.; Thirkell, L.; Thomas, R.;
Torkar, K.; Varmuza, K.; Wanczek, K. -P.; Altobelli, N.; Baklouti,
D.; Bardyn, A.; Fray, N.; Krüger, H.; Ligier, N.; Lin, Z.; Martin,
P.; Merouane, S.; Orthous-Daunay, F. R.; Paquette, J.; Revillet, C.;
Siljeström, S.; Stenzel, O.; Zaprudin, B.
Bibcode: 2016ApJ...816L..32H
Altcode:
The COmetary Secondary Ion Mass Analyser instrument on board ESA's
Rosetta mission has collected dust particles in the coma of comet
67P/Churyumov-Gerasimenko. During the early-orbit phase of the Rosetta
mission, particles and particle agglomerates have been imaged and
analyzed in the inner coma at distances between 100 km and 10 km off
the cometary nucleus and at more than 3 AU from the Sun. We identified
585 particles of more than 14 μm in size. The particles are collected
at low impact speeds and constitute a sample of the dust particles in
the inner coma impacting and fragmenting on the targets. The sizes of
the particles range from 14 μm up to sub-millimeter sizes and the
differential dust flux size distribution is fitted with a power law
exponent of -3.1. After impact, the larger particles tend to stick
together, spread out or consist of single or a group of clumps, and
the flocculent morphology of the fragmented particles is revealed. The
elemental composition of the dust particles is heterogeneous and the
particles could contain typical silicates like olivine and pyroxenes, as
well as iron sulfides. The sodium to iron elemental ratio is enriched
with regard to abundances in CI carbonaceous chondrites by a factor
from ∼1.5 to ∼15. No clear evidence for organic matter has been
identified. The composition and morphology of the collected dust
particles appear to be similar to that of interplanetary dust particles.
Title: COSIMA at Comet 67P/Churyumov-Gerasimenko After Perihelion
Authors: Paquette, J. A.; Altobelli, N.; Altwegg, K.; Briois,
C.; Colangeli, L.; Cottin, H.; Baklouti, D.; Bardyn, A.; Engrand,
C.; Fischer, H.; Fray, N.; Glasmachers, A.; Gruen, E.; Godard, M.;
Haerendel, G.; Henkel, H.; Hilchenbach, M.; von Hoerner, H.; Höfner,
H.; Hornung, K.; Jessberger, E.; Kissel, J.; Koch, A.; Lacerda, P.;
Langevin, Y.; Lehto, H.; Lehto, K.; Le Roy, L.; Ligier, N.; Martin,
P.; Merouane, S.; Orthous-Daunay, F. R.; Raulin, F.; Revillet, C.;
Rynö, J.; Schulz, R.; Silen, J. V.; Siljeström, S.; Steiger, W.;
Stenzel, O.; Stephan, T.; Thirkell, L.; Thomas, R.; Torkar, K.;
Varmuza, K.; Wanczek, K. P.; Lin, Z. Y.; Zaprudin, B.
Bibcode: 2015AGUFM.P31E2089P
Altcode:
COSIMA (the COmetary Secondary Ion Mass Analyser) is one of the three
scientific in-situ dust instruments onboard the Rosetta spacecraft
[1]. Rosetta has been orbiting comet 67P/Churyumov-Gerasimenko since
August of 2014. COSIMA is collecting cometary dust particles in the
inner coma by exposing metal targets. It then images the targets
periodically with COSISCOPE, a microscope/camera, in search of the
captured particles. A variety of particle morphologies are seen. A
sample particle is shown in Figure 1. Some of the identified cometary
particles are further investigated by SIMS (Secondary Ion Mass
Spectrometry). The high resolution mass spectra show the presence of
positive or negative ions of elements, organic molecules and molecular
fragments originating from the selected grain surface. Changes in dust
characteristics with time will be discussed. [1] Kissel et al. (2007),
Sp. Sci. Rev. 128, 823-867. [2] Schulz et al. (2015), Nature, 518,
216-218. Figure 1:A cometary particle collected by COSIMA [2]
Title: Dying Flow Bursts as Generators of the Substorm Current Wedge
Authors: Haerendel, G.
Bibcode: 2015AGUFMSM51E2602H
Altcode:
Many theories or conjectures exist on the driver of the substorm current
wedge, e.g. rerouting of the tail current, current disruption, flow
braking, vortex formation, and current sheet collapse. Magnitude,
spatial scale, and temporal development of the related magnetic
perturbations suggest that the generator is related to the interaction
of the flow bursts with the dipolar magnetosphere after onset of
reconnection in the near-Earth tail. The question remains whether it is
the flow energy that feeds the wedge current or the internal energy of
the arriving plasma. In this presentation I argue for the latter. The
current generation is attributed to the force exerted by the dipolarized
magnetic field of the flow bursts on the preceding layer of high-beta
plasma after flow braking. The generator current is the grad-B current
at the outer boundary of the compressed high-beta plasma layers. It
needs the sequential arrival of several flow bursts to account for
duration and magnitude of the ionospheric closure current.
Title: COSIMA - In-situ dust particles measurements in the inner
coma of comet 67P/Churyumov-Gerasimenko
Authors: Bardyn, Anais; Hilchenbach, Martin; Briois, Christelle;
Kissel, Jochen; Koch, Andreas; Langevin, Yves; Schulz, Rita; Silen,
Johan; Altwegg, Kathrin; Colangeli, Luigi; Cottin, Herve; Engrand,
Cecile; Fischer, Henning; Glasmachers, Albrecht; Grün, Eberhard;
Haerendel, Gerhard; Henkel, Hartmut; Höfner, Herwig; Hornung, Klaus;
Jessberger, Elmar K.; Lehto, Harry; Lehto, Kirsi; Raulin, Francois; Le
Roy, Lena; Rynö, Jouni; Steiger, Wolfgang; Stephan, Thomas; Thirkell,
Laurent; Thomas, Roger; Torkar, Klaus; Varmuza, Kurt; Wanczek,
Karl-Peter; Altobelli, Nicolas; Baklouti, Donia; Fray, Nicolas;
Lacerda, Pedro; Ligier, Nicolas; Lin, ZhongYi; Martin, Philippe;
Merouane, Sihane; Orthous-Daunay, François-Régis; Paquette, John;
Revillet, Claire; Siljeström, Sandra; Stenzel, Oliver; Zaprudin, Boris
Bibcode: 2015DPS....4750308B
Altcode:
COSIMA, the COmetary Secondary Ion Mass Analyzer, is one of the
three in-situ dust instruments onboard the Rosetta spacecraft
[1]. Since August 2014, Rosetta has been escorting the comet
67P/Churyumov-Gerasimenko on its journey toward the inner solar
system.COSIMA is collecting cometary dust particles by exposing metal
targets in the inner coma, from 10 to hundreds of kilometers off the
cometary nucleus [2]. Already several thousands of dust particles have
been collected. The targets are imaged with the microscope COSISCOPE
and some collected particles are then analyzed by SIMS (Secondary Ion
Mass Spectrometry). The mass spectra contain positive and negative ions
revealing components of the grains originating from selected surface
areas. Dust characteristics will be presented and discussed.[1] Kissel
et al. (2007), Sp. Sci. Rev. 128, 82-867. [2] Schulz et al. (2015),
Nature, 518, 216-218.
Title: The nonmagnetic nucleus of comet 67P/Churyumov-Gerasimenko
Authors: Auster, Hans-Ulrich; Apathy, Istvan; Berghofer, Gerhard;
Fornacon, Karl-Heinz; Remizov, Anatoli; Carr, Chris; Güttler, Carsten;
Haerendel, Gerhard; Heinisch, Philip; Hercik, David; Hilchenbach,
Martin; Kührt, Ekkehard; Magnes, Werner; Motschmann, Uwe; Richter,
Ingo; Russell, Christopher T.; Przyklenk, Anita; Schwingenschuh,
Konrad; Sierks, Holger; Glassmeier, Karl-Heinz
Bibcode: 2015Sci...349a5102A
Altcode:
Knowledge of the magnetization of planetary bodies constrains their
origin and evolution, as well as the conditions in the solar nebular
at that time. On the basis of magnetic field measurements during the
descent and subsequent multiple touchdown of the Rosetta lander Philae
on the comet 67P/Churyumov-Gerasimenko (67P), we show that no global
magnetic field was detected within the limitations of analysis. The
Rosetta Magnetometer and Plasma Monitor (ROMAP) suite of sensors
measured an upper magnetic field magnitude of less than 2 nanotesla
at the cometary surface at multiple locations, with the upper specific
magnetic moment being <3.1 × 10-5 ampere-square meters
per kilogram for meter-size homogeneous magnetized boulders. The
maximum dipole moment of 67P is 1.6 × 108 ampere-square
meters. We conclude that on the meter scale, magnetic alignment in
the preplanetary nebula is of minor importance.
Title: Flow bursts, breakup arc, and substorm current wedge
Authors: Haerendel, Gerhard
Bibcode: 2015JGRA..120.2796H
Altcode:
Energy liberated by the reconnection process in the near-Earth tail is
transported via flow bursts toward the dipolar magnetosphere during
substorms. The breakup arc is a manifestation of the arrival of
the bursts under flow braking and energy deposition. Its structure
and behavior is analyzed on the basis of five striking spatial,
temporal, and energetic properties, qualitatively and in part also
quantitatively. A key element is the formation of stop layers. They are
thin layers, of the width of an ion gyro radius, in which the magnetic
field makes a transition from tail to near-dipolar magnetosphere
configurations and in which the kinetic energy of fast flows is
converted into electromagnetic energy of kinetic Alfvén waves. The
flows arise from the relaxation of the strong magnetic shear stresses in
the leading part of the flow bursts. The bright narrow arcs of less than
10 km width inside the broad poleward expanding breakup arc, Alfvénic
in nature and visually characterized by erratic short-lived rays, are
seen as traces of the stop layers. The gaps between two narrow and
highly structured arcs are filled with more diffuse emissions. They
are attributed to the relaxation of the less strained magnetic field
of the flow bursts. Eastward flows along the arcs are linked to the
shrinking gaps between two successive arcs and the entry of auroral
streamers into the dipolar magnetosphere in the midnight sector. Flow
braking in the stop layers forms multiple pairs of narrow balanced
currents and cannot be behind the formation of the substorm current
wedge. Instead, its origin is attributed to the force exerted by the
dipolarized magnetic field of the flow bursts on the high-beta plasma,
after the high magnetic shears have relaxed and the fast flows and stop
layer process have subsided, in other words, to the "dying flow bursts."
Title: Substorm onset: Current sheet avalanche and stop layer
Authors: Haerendel, Gerhard
Bibcode: 2015JGRA..120.1697H
Altcode:
A new scenario is presented for the onset of a substorm and the
nature of the breakup arc. There are two main components, current
sheet avalanche and stop layer. The first refers to an earthward
flow of plasma and magnetic flux from the central current sheet of
the tail, triggered spontaneously or by some unknown interaction with
an auroral streamer or a suddenly appearing eastward flow at the end
of the growth phase. The second offers a mechanism to stop the flow
abruptly at the interface between magnetosphere and tail and extract
momentum and energy to be partially processed locally and partially
transmitted as Poynting flux toward the ionosphere. The stop layer
has a width of the order of the ion inertial length. The different
dynamics of the ions entering freely and the magnetized electrons
create an electric polarization field which stops the ion flow and
drives a Hall current by which flow momentum is transferred to the
magnetic field. A simple formalism is used to describe the operation
of the process and to enable quantitative conclusions. An important
conclusion is that by necessity the stop layer is also highly structured
in longitude. This offers a natural explanation for the coarse ray
structure of the breakup arc as manifestation of elementary paths of
energy and momentum transport. The currents aligned with the rays are
balanced between upward and downward directions. While the avalanche
is invoked for explaining the spontaneous substorm onset at the inner
edge of the tail, the expansion of the breakup arc for many minutes
is taken as evidence for a continued formation of new stop layers
by arrival of flow bursts from the near-Earth neutral line. This
is in line with earlier conclusions about the nature of the breakup
arc. Small-scale structure, propagation speed, and energy flux are
quantitatively consistent with observations. However, the balanced
small-scale currents cannot constitute the substorm current wedge. The
source of the latter must be located just earthward of the stop layer in
the near-dipolar magnetosphere and be powered by the internal energy of
the flow bursts. The stop layer mechanism is in some way the inverse
of reconnection, as it converts flow into electromagnetic energy,
and may have wide applicability in astrophysical plasmas.
Title: In-Situ Cometary Particle Measurements in the Inner Coma of
Comet 67P/Churyumov-Gerasimenko
Authors: Hilchenbach, M.; Langevin, Y.; Engrand, C.; Merouane, S.;
Stenzel, O.; Kissel, J.; Briois, Ch.; Koch, A.; Schulz, R.; Silen,
J.; Altwegg, K.; Colangeli, L.; Cottin, H.; Fischer, H.; Glasmachers,
A.; Grün, E.; Haerendel, G.; Henkel, H.; Höfner, H.; Hornung, K.;
Jessberger, E. K.; Lehto, H.; Lehto, K.; Raulin, F.; Le Roy, L.; Rynö,
J.; Steiger, W.; Stephan, T.; Thirkell, L.; Thomas, R.; Torkar, K.;
Varmuza, K.; Wanczek, K. P.; Altobelli, N.; Baklouti, D.; Bardyn,
A.; Fray, N.; Godard, M.; Martin, P.; Lacerda, P.; Ligier, N.; Lin,
Z.; Orthous-Daunay, F. R.; Paquette, J.; Revillet, C.; Siljeström,
S.; Zaprudin, B.
Bibcode: 2015LPI....46.1936H
Altcode: 2015LPICo1832.1936H
Comet 67P/Churyumov-Gerasimenko has a dusty inner coma and particle
morphology assembles agglomerates.
Title: Substorms
Authors: Haerendel, Gerhard
Bibcode: 2015GMS...207..307H
Altcode:
This chapter deals with the essence of the magnetospheric substorm,
the return of magnetic flux into the magnetosphere after disconnection
from the solar wind magnetic field. There are three fundamental
transport processes involved: (1) thinning of the tail plasma sheet
and accompanying recession of the outer boundary of the dipolar
magnetosphere during the growth phase, (2) flux transport along
the tail toward that boundary after onset of tail reconnection,
and (3) penetration of plasma and magnetic flux into the dipolar
magnetosphere. The chapter then looks at corresponding processes in
the Jupiter and Saturn magnetospheres and tails, which are strongly
dominated by the fast planetary rotations. It elucidates some key
aspects of the entry problem, albeit from a personal vantage point,
and addresses the still open questions. Finally, the chapter addresses
the correlation between solar wind ram pressure and auroral activity
and brightness on Jupiter and Saturn.
Title: First Results of Plasma And Magnetic Field Measurements
Onboard The Rosetta Lander Philae at The Surface of Comet
67P/Churyumov-Gerasimenko
Authors: Auster, H. U.; Apathy, I. N.; Remizov, A.; Berghofer, G.;
Hilchenbach, M.; Haerendel, G.; Heinisch, P.; Richter, I.; Glassmeier,
K. H.
Bibcode: 2014AGUFM.P34B..02A
Altcode:
The ROMAP (Rosetta Lander Magnetometer and Plasma Monitor) suite of
sensors onboard the Rosetta lander Philae consists of a fluxgate
magnetometer and plasma ion and electron sensors. ROMAP will
measure for the first time the magnetic field as well as electron
and ion distributions on a cometary surface.
First magnetic field
measurements during the Philae descent and plasma investigations during
the first science sequence on the cometary surfce will be presented
together with concurrent magnetic field measurements of the Rosetta
orbiter. Furthermore, we shall discuss the measurement operation
strategy for the long term sequence, for observing the evolution of
the plasma environment by measurements with both plasma packages,
ROMAP on the surface and RPC onboard the Rosetta Orbiter.
Title: Cosima - Cometary Dust Analysis Next to Comet
67P/Churyumov-Gerasimenko
Authors: Hilchenbach, M.; Kissel, J.; Briois, C.; Henkel, H.; Langevin,
Y.; Schulz, R.; Silen, J. V.; Altwegg, K.; Colangeli, L.; Cottin, H.;
Engrand, C.; Glasmachers, A.; Grün, E.; Haerendel, G.; Höfner, H.;
Hornung, K.; Jessberger, E.; Koch, A.; Lehto, H.; Lehto, K.; Raulin,
F.; Le Roy, L.; Rynö, J.; Steiger, W.; Stephan, T.; Thirkell, L.;
Thomas, R.; Torkar, K.; Varmuza, K.; Wanczek, K. P.
Bibcode: 2014AGUFM.P32B..04H
Altcode:
After a long journey through the inner solar system, ESA's corner stone
mission ROSETTA has arrived at comet 67P/Churyumov-Gerasimenko. COSIMA
or the COmetary Secondary Ion Mass Analyzer onboard ROSETTA is a
secondary ion mass spectrometer focussing on in-situ measurements of
the composition of cometary grains collected next to the nucleus and
inner coma. High resolution mass spectra will contain complex mixtures
of mineral and organic elements and molecules as well as molecular
fragments representing the elements and molecules on the surface of
the cometary grains. We will report on first results of the in-situ
analysis of cometary grains as captured, imaged and analysed by COSIMA .
Title: COSIMA - Cometary Dust Analysis in the inner coma of Comet
67P/Churyumov-Gerasimenko
Authors: Hilchenbach, Martin; Kissel, Jochen; Briois, Christelle;
von Hoerner, Hanna; Langevin , Yves; Schulz, Rita; Silen, Johan;
Altwegg, Kathrin; Colangeli, Luigi; Cottin, Herve; Engrand, Cecile;
Glasmachers, Albrecht; Gruen, Eberhard; Haerendel, Gerhard; Henkel,
Hartmut; Höfner, Herwig; Hornung, Klaus; Jessberger, Elmar; Koch,
Andreas; Letho, Harry; Letho, Kirsi; Raulin, Francois; Le Roy, Lena;
Rynö, Jouni; Steiger , Wolfgang; Stephan , Thomas; Laurent, Thirkell;
Thomas, Roger.; Torkar, Klaus; Varmuza, Kurt; Wanczek, Klaus Peter
Bibcode: 2014DPS....4620903H
Altcode:
After a long journey through the inner solar system,
ESA’s corner stone mission ROSETTA has arrived at comet
67P/Churyumov-Gerasimenko. COSIMA or the COmetary Secondary Ion Mass
Analyzer onboard ROSETTA is a secondary ion mass spectrometer focussing
on in-situ measurements of the composition of cometary grains collected
near the nucleus and inner coma. High resolution mass spectra will
contain ions of complex mixtures of mineral compounds and organic
molecules as well as molecular fragments representing the elements
and molecules on the surface of the cometary grains. We will report on
our envisaged in-situ analysis goals of cometary grains as captured,
imaged and analysed by COSIMA.
Title: Role and origin of the poleward Alfvénic arc
Authors: Haerendel, G.; Frey, H. U.
Bibcode: 2014JGRA..119.2945H
Altcode:
Alfvénic arcs are often found adjacent to the poleward border of the
substorm bulge. They are created by precipitating narrow electron beams
with a broad energy distribution, mainly below 1 keV, and dominated
by Alfvénic structures of small scales and frequencies in the 1 Hz
range. They are also associated with transverse ion heating. A balanced
field-aligned current system accompanying the poleward Alfvénic arc
reveals its underlying structure being a broad channel of primary
energy inflow of several tens of kilometers width. The associated
magnetic shear stresses drive a flow along the poleward side of
the substorm current wedge. Polar cap convection passes through
this channel before entering the substorm bulge. The small-scale
electromagnetic structures are developing from the primary energy
inflow by scale breaking and multiple reflections in the ionospheric
Alfvén resonator. By their parallel electric field components these
structures decouple effectively from the ionosphere. Their energy
content is converted into kinetic energy of auroral particles in the
topside ionosphere. A selected data set from FAST, DE 2, and Cluster
is presented for characterizing the energetic and electromagnetic
properties of the Alfvénic arc. Its function in the substorm can be
summarized as a preconditioning of the polar cap plasma and magnetic
field for entry into the magnetosphere through the poleward arc. This
occurs under substantial density depletion.
Title: M-I coupling scales and energy dumping
Authors: Haerendel, Gerhard
Bibcode: 2014GeoRL..41.1846H
Altcode:
The paper reviews three magnetosphere-ionosphere coupling scales
characterizing (1) inverted-V auroral arcs, (2) so-called Alfvénic
arcs, and (3) dense plasma clouds artificially injected into the
magnetosphere. The three scale-breaking processes are different but
follow all from the principle of perfect matching of the wave impedance
of the energy and momentum carrier with the effective resistance of the
energy dump. As a consequence, wave reflections from the ionosphere
are absent or present only in a short initial phase and lead to
quasi-stationary wave fields. In inverted-V auroral arcs the energy
conversion occurs in the low magnetosphere by postacceleration of the
current-carrying hot electrons. For the Alfvénic arc the energy is
transferred first to dispersive Alfvén waves which are then damped
in the topside ionosphere by accelerating electrons along B and ions
transversely to B. Barium plasma clouds break into narrow striations
mapping to ionospheric scales that experience a strongly reduced
Pedersen conductivity and thus achieve the perfect matching. It is also
argued that the scale √(ΣP/K), derived from electrostatic mapping,
is not suited to describe M-I coupling.
Title: Plasma Entry from Tail into the Dipolar Magnetosphere During
Substorms
Authors: Haerendel, Gerhard
Bibcode: 2014cosp...40E1130H
Altcode:
Plasma entering the dipolar magnetosphere from the tail has to overcome
the obstacle presented by the conductivity enhancements caused by the
poleward arc(s). While the arcs move poleward, the plasma proceeds
equatorward as testified by the existence of a westward electric
field. The arcs break into smaller-scale structures and loops with a
tendency of eastward growth and expansion, although the basic driving
force is directed earthward/equatorward. The likely reason is that the
arc-related conductivity enhancements act as flow barriers and convert
normal into shear stresses. The energy derived from the release of the
shear stresses and dissipated in the arcs lowers the entropy content of
the flux tubes and enables their earthward progression. In addition,
poleward jumps of the breakup arcs are quite common. They result from
refreshments of the generator plasma by the sequential arrival of flow
bursts from the near-Earth neutral line. Once inside the oval, the
plasma continues to move equatorward as manifested through north-south
aligned auroral forms. Owing to the existence of an inner border of
the oval, marked by the Region 2 currents, all flows are eventually
diverted sunward.
Title: Dayside auroral hiss observed at South Pole Station
Authors: Yan, X.; Labelle, J.; Haerendel, G.; Spasojevic, M.; Bunch,
N.; Golden, D. I.; Frey, H. U.; Weatherwax, A. T.
Bibcode: 2013JGRA..118.1220Y
Altcode:
We performed a statistical study of low frequency (LF) auroral hiss
recorded at South Pole Station in 2004, 2005, and 2007, and very
low frequency (VLF) hiss recorded in 2000-2008. As expected, most
auroral hiss occurs in the pre-midnight sector. However, there is a
secondary peak in occurrence in the pre-noon sector (1000-1530 UT;
∼ 0630-1200 magnetic local time (MLT)) and somewhat more events
occur in the post-noon sector (1530-2100 UT; ∼ 1200-1730 MLT),
with a null in occurrence around noon MLT. Individual dayside events
appear similar to nightside hiss, but statistically they do not extend
to as high frequencies. Solar wind discontinuities or impulses on the
magnetopause are not correlated with these events. All-sky camera,
photometer, magnetometer, riometer, and VLF receiver data show that
dayside LF hiss almost always extends to the VLF range and is often
associated with active aurora. Examination of interplanetary magnetic
field (IMF), substorm conditions, and Kp/AE/QI indices at times of
dayside hiss suggests differences between the pre-noon and post-noon
events: pre-noon events are associated with IMF By <
0, whereas post-noon events favor Bz < 0 and show a
weaker correlation with By > 0. The correlation between
pre-noon events and By < 0 may arise because under
those conditions, the pattern of field-aligned currents (FACs) shifts
to later magnetic local times, causing upward FACs to be dominant
during pre-noon hours at 74°, the invariant latitude of the South
Pole. Unlike pre-noon events, post-noon events are more often associated
with substorm activity on the nightside and favor elevated Kp indices,
suggesting a connection of post-noon events to nightside activity.
Title: Ionospheric Control of the Distribution of Magnetospheric
Reconnection and Convection
Authors: Zhang, B.; Smith, R. H.; Brambles, O.; Lotko, W.; Ouellette,
J.; Lyon, J.; Haerendel, G.
Bibcode: 2012AGUFMSM22A..05Z
Altcode:
Observations reveal that for southward interplanetary magnetic field
conditions the two-cell convection pattern in Earth's ionosphere rotates
clockwise relative to the sun-earth line (when viewed from above the
pole) with more magnetic flux circulating in the dusk convection cell
than in the dawn cell. For the same interplanetary conditions, the
nightside magnetosphere exhibits enhanced magnetic reconnection along
the premidnight x-line with fast exhaust flows developing in channels in
the premidnight plasmasheet. These asymmetries have been investigated
extensively in isolation and essentially as independent phenomena. It
is shown here for the first time that they are actually different
manifestations of the same coupled process. Global simulations of the
magnetosphere-ionosphere interaction and simple physical considerations
show that the observed asymmetries are a consequence of meridional
gradients in the ionospheric Hall conductance. Causal relationships
are demonstrated through a series of controlled numerical experiments
which would be practically impossible to tease-out observationally.
Title: Birth and life of auroral arcs embedded in the evening auroral
oval convection: A critical comparison of observations with theory
Authors: Haerendel, G.; Frey, H. U.; Chaston, C. C.; Amm, O.; Juusola,
L.; Nakamura, R.; Seran, E.; Weygand, J. M.
Bibcode: 2012JGRA..11712220H
Altcode:
We present and analyze data on auroral arcs obtained during a pass
of the FAST satellite over the field-of-view of the all-sky camera
at Ft. Simpson (Canada), supported by ground-based magnetometer and
SuperDARN radar data, and plasma data from THEMIS-A near the source
region of the auroral currents. The auroral event took place at 19:00
MLT during substorm activity further east. Active auroral arcs were
present over six degrees in latitude moving equatorward with significant
changes in brightness and structure. New arcs were forming continuously
at the polar border of the auroral oval which was marked by an Alfvénic
arc. The data analysis revealed that the equatorward drift of the
arcs was in part due to convective motion of the plasma frame but was
rather dominated by proper motions of the arcs. Interpretation of these
findings in the framework of theoretical work by one of the authors
reproduces quantitatively the observed proper motion as a consequence
of the progressive erosion of magnetic shear stresses. Most important
was the possibility to deduce the interaction time scale between arc
and source region. On average it corresponded to about six to eight
transit times of an Alfvén wave between arc and source plasma or two
fundamental eigenperiods of toroidal mode or azimuthally polarized
Alfvén waves. However, large variations of the interaction times
and corresponding proper motions were found. They are attributed to
temporal and spatial variations of the energy input from the source
plasma. The more remarkable is the fact that analysis on the basis of
a quasi-stationary model produces consistent results. The progressive
release of shear stresses during the equatorward motion of the arcs
leads to the conclusion that they are dying after having reached the
maximum of the poleward Pedersen current.
Title: Magnetosphere-ionosphere coupling and scale breaking of a
plasma cloud in the magnetosphere
Authors: Haerendel, Gerhard; Mende, Stephen B.
Bibcode: 2012JGRA..117.9233H
Altcode: 2012JGRA..11709233H
The goal of this paper is to deliver a long-missing interpretation
of a central issue of the NASA-MPE barium injection experiment
performed in September 1971. It pertains to the interaction with the
ionosphere. Observations of the cloud's motion revealed no obvious sign
of such interaction. The barium vapor was released from a Scout rocket
at an altitude of 31,000 km above South America during late evening
hours and was observed for more than 4000 s. The barium plasma split
into several field-parallel streaks which moved for a long time as if
subject to constant acceleration as viewed from the inertial frame
of the rocket at release. This means that no reflection of energy
due to a mismatch of ionospheric conductivity and the characteristic
impedance of an impinging Alfvén wave was observed. It is this finding
that has never been properly interpreted. Furthermore, after a careful
assessment of the barium cloud properties and environmental parameters,
we find a theoretical coupling time to the ambient flow which turns
out to be substantially longer than observed. Although this appears to
indicate that some interaction with the ionosphere occurred, we can
rule out multiple wave reflections during the observed acceleration
phase. Discarding other possibilities, we interpret the observed motions
as sign of perfect matching of the momentum and energy flux into the
ionosphere with the rate of dissipation. This is achieved during the
initial phase by scale breaking of the cloud into streaks with narrow
widths which allow parallel potential drops along the Alfvén wings
because of the waves' inertial nature and inside the lower ionosphere
owing to the finite parallel resistivity, thereby greatly reducing
the effective Pedersen conductivity. The significance of this finding
goes beyond understanding the barium injection experiment. It sheds
light on how magnetospheric plasma irregularities can share momentum
and energy with the ionosphere in an optimized fashion.
Title: A tool for characterizing and evaluating Type II auroral arcs
Authors: Haerendel, Gerhard
Bibcode: 2012JGRA..117.6214H
Altcode: 2012JGRA..11706214H
The paper is intended as a tool for describing or analyzing auroral arcs
embedded in a Type II current system. The physics has been extensively
described by analytical models in recent papers of the author. Here
it is only briefly summarized to the extent needed to explain the set
of relations describing the gross properties of embedded arcs. The
equations are fully consistent with those derived in the earlier
papers, but more general. A new element is the consideration of what
determines the width of an auroral arc. Two solutions are presented
depending on the relative contributions of the auroral acceleration
process and ionospheric dissipation to the total energy conversion
rate. It is argued that nature chooses the solution of optimum energy
conversion. The equations are best suited to describe structured arcs
in the evening auroral oval with inverted-V particle signature, even
when they appear more dynamic than a quasi-static approach seems to
allow. In spite of the inherent idealizations, the presented relations
may prove to be useful for analyzing data from satellite transits
through auroral current sheets.
Title: Solar Auroras
Authors: Haerendel, Gerhard
Bibcode: 2012ApJ...749..166H
Altcode:
This paper deals with the acceleration of high-energy flare electrons
by field-parallel electric fields in an approach tailored after the
auroral acceleration process. Electromagnetic energy, derived from
the release of magnetic shear stresses, is converted into kinetic
energy of particles. The stress release is enabled by field-aligned
potential drops generated by anomalous resistivity of highly filamentary
currents. The high-energy flare electrons are identified with runaway
particles of this process. The magnetic shear stresses originate
from Alfvén waves emitted from high-beta loop-top plasma which is
produced by braking of the outflow from a reconnection site higher
up in the corona. Partial reflection of the waves at the interface
to the chromosphere leads to evaporation of chromospheric plasma and
creation of a strongly filamentary structure in the sheared coronal
field. The energy conversion process propagates spontaneously, like an
erosion process in three dimensions. The overall stress release site
forms a thin triangular sheet growing along and perpendicular to the
field. After about one second, its cross-section perpendicular to B has
grown to tens of square kilometers. This spontaneous growth strongly
alleviates the demands on the primary filamentary structure posed by
the condition of current criticality. Energy flux and mean energy are
of the magnitude typical for hard X-rays producing electrons. Their
strong dependence on the ambient magnetic field in combination with
the fast propagation of the energy conversion sites could lead to
energy-dependent time delays of a few 100 ms, much longer than the
time-of-flight effects of the electrons.
Title: Alfvén: magnetosphere—ionosphere connection explorers
Authors: Berthomier, M.; Fazakerley, A. N.; Forsyth, C.; Pottelette,
R.; Alexandrova, O.; Anastasiadis, A.; Aruliah, A.; Blelly, P. -L.;
Briand, C.; Bruno, R.; Canu, P.; Cecconi, B.; Chust, T.; Daglis,
I.; Davies, J.; Dunlop, M.; Fontaine, D.; Génot, V.; Gustavsson,
B.; Haerendel, G.; Hamrin, M.; Hapgood, M.; Hess, S.; Kataria, D.;
Kauristie, K.; Kemble, S.; Khotyaintsev, Y.; Koskinen, H.; Lamy, L.;
Lanchester, B.; Louarn, P.; Lucek, E.; Lundin, R.; Maksimovic, M.;
Manninen, J.; Marchaudon, A.; Marghitu, O.; Marklund, G.; Milan, S.;
Moen, J.; Mottez, F.; Nilsson, H.; Ostgaard, N.; Owen, C. J.; Parrot,
M.; Pedersen, A.; Perry, C.; Pinçon, J. -L.; Pitout, F.; Pulkkinen,
T.; Rae, I. J.; Rezeau, L.; Roux, A.; Sandahl, I.; Sandberg, I.;
Turunen, E.; Vogt, J.; Walsh, A.; Watt, C. E. J.; Wild, J. A.;
Yamauchi, M.; Zarka, P.; Zouganelis, I.
Bibcode: 2012ExA....33..445B
Altcode: 2011ExA...tmp...35V; 2011ExA...tmp..160B; 2011ExA...tmp..136B
The aurorae are dynamic, luminous displays that grace the night skies
of Earth's high latitude regions. The solar wind emanating from
the Sun is their ultimate energy source, but the chain of plasma
physical processes leading to auroral displays is complex. The
special conditions at the interface between the solar wind-driven
magnetosphere and the ionospheric environment at the top of Earth's
atmosphere play a central role. In this Auroral Acceleration Region
(AAR) persistent electric fields directed along the magnetic field
accelerate magnetospheric electrons to the high energies needed
to excite luminosity when they hit the atmosphere. The "ideal
magnetohydrodynamics" description of space plasmas which is useful in
much of the magnetosphere cannot be used to understand the AAR. The
AAR has been studied by a small number of single spacecraft missions
which revealed an environment rich in wave-particle interactions,
plasma turbulence, and nonlinear acceleration processes, acting on a
variety of spatio-temporal scales. The pioneering 4-spacecraft Cluster
magnetospheric research mission is now fortuitously visiting the AAR,
but its particle instruments are too slow to allow resolve many of
the key plasma physics phenomena. The Alfvén concept is designed
specifically to take the next step in studying the aurora, by making
the crucial high-time resolution, multi-scale measurements in the
AAR, needed to address the key science questions of auroral plasma
physics. The new knowledge that the mission will produce will find
application in studies of the Sun, the processes that accelerate the
solar wind and that produce aurora on other planets.
Title: Birth and Life of Auroral Arcs Embedded in the Evening
Auroral Oval
Authors: Haerendel, G.; Chaston, C. C.; Frey, H. U.; Amm, O.; Juusola,
L.; Nakamura, R.; Seran, E.; Weygand, J. M.
Bibcode: 2011AGUFMSM31A2072H
Altcode:
We report on all-sky camera observations at Ft. Simpson during the
crossing of the FAST spacecraft on 09 March 2008 at about 19:00
MLT. FAST registered eight auroral arcs with the associated upward
currents and two periods of downward currents during the crossing
time of five minutes. All arcs were moving equatorward with speeds
near 300 m/s. Some of them exhibited local broadening and subsequent
unfolding. Most remarkable was the appearance of new arcs at the
poleward border of the auroral oval, clearly marked by an Alfvénic
arc. The FAST data on energy and energy flux of the precipitating
electrons and the jumps of the transverse magnetic perturbation field
through the arcs were evaluated for five of the arcs following the
formalism of Haerendel [2007]. This led to very consistent values for
the integral wave impedance, field-parallel conductance, Alfvénic
transit time, arc width, proper motion, and total energy release
including the ionospheric dissipation. The most significant result
is that all equatorward motions of the arcs were consistent with
being proper motions in the rest frame of the ambient plasma. This
is observational evidence for the arcs feeding on the magnetic energy
liberated by the release of shear stresses in a region of dominantly
upward field-aligned currents.
Title: Electromagnetic power flows in MI coupling: origins, spatial
scales, and conversion processes
Authors: Haerendel, G.
Bibcode: 2011AGUFMSM41C..01H
Altcode:
There are four dominant sources of e.m. energy flow from the outer
realms of the magnetosphere into the ionosphere, (1) dragging of open
flux tubes by the solar wind, (2) braking of earthward reconnection
flows in the tail, (3) earthward directed forces of hot plasma
piling up at the inner edge of the tail during substorms, and (4)
pressure forces driving the sunward convection along the auroral
oval. The fraction of the energy flux arriving immediately at the
ionosphere varies strongly among these four mechanisms. In (1) most
of the energy first flows into the plasma sheet, while in process
(4) most of the energy flows directly into the ionosphere, or a
fraction of it indirectly via auroral particle production. There are
no intrinsic scales for the direct flow of energy into the ionosphere
and dissipation by ion-neutral collisions, but where energy is first
processed by energization of auroral particles, various transverse
scales appear. They are owed to the matching of Alfvén wave impedance
and field-parallel or ionospheric conductances, or to the dissipative
properties of kinetic Alfvén waves. In all cases, the dumping of the
energy flow involves the release of shear magnetic stresses.
Title: Six auroral generators: A review
Authors: Haerendel, Gerhard
Bibcode: 2011JGRA..116.0K05H
Altcode:
The paper reviews generator processes and configurations of six types
of auroral arcs: embedded arcs, Alfvénic arcs, onset arcs, poleward
arcs during substorms, auroral streamers, and auroral spirals. The
arcs and generators are elements in global current systems, which are
classified as Types I and II after Boström. The arcs may be dominated
by transient processes or be quasi-stationary. The main emphasis of the
paper is on the generator forces. They are pressure gradient forces,
magnetic normal or shear stresses, or inertial forces. For three cases,
the arcs embedded in the oval convection, the poleward arc during
substorms, and the auroral streamers, simple expressions are presented
of the currents injected into the ionosphere by the generator process,
allowing quantitative evaluations. The relations leading from these
currents to other key auroral quantities are summarized. The apparent
conflict between the widths of Alfvénic arcs and the transverse scales
required for energy coupling to the topside ionospheric plasma is solved
by assuming current and field filamentation by multiple reflections in
the ionospheric Alfvén resonator. The substorm generator is described
as a high-beta plasma layer arising from collapse of the tail current
sheet. An essential element in this process is the shedding of excess
flux tube entropy through energy dumping in the auroral acceleration
process and ionospheric dissipation. The dynamics of this process
needs further investigation. The physics of the connection between flow
bursts in the tail plasma sheet and the flows associated with auroral
streamers in the ionosphere is discussed. Regular auroral spirals and
the westward traveling surge have in common a concentration of upward
field-aligned current which demands strongly enhanced dissipation. They
differ by the processes creating the upward current concentration.
Title: Magnetic fractures or reconnection of type II
Authors: Haerendel, Gerhard
Bibcode: 2011IAUS..274...56H
Altcode:
The importance of reconnection in astrophysics has been widely
recognized. It is instrumental in storing and releasing magnetic energy,
the latter often in a dramatic fashion. A closely related process,
playing in very low beta plasmas, is much less known. It is behind the
acceleration of auroral particles in the low-density environment several
1000 km above the Earth. It involves the appearance of field-parallel
voltages in presence of intense field-aligned currents. The underlying
physical process is the release of magnetic shear stresses and
conversion of the liberated magnetic energy into kinetic energy of
the particles creating auroral arcs. In this process, field lines
disconnect from the field anchored in the ionosphere and reconnect
to other field lines. Because of the stiffness of the magnetic field,
the process resembles mechanical fractures. It is typically active in
the low-density magnetosphere of planets. However, it can also lead
to significant energy conversion with high-energy particle production
and subsequent gamma ray emissions in stellar magnetic fields, in
particular of compact objects.
Title: A Droplet Model of Quiescent Prominence Downflows
Authors: Haerendel, G.; Berger, T.
Bibcode: 2011ApJ...731...82H
Altcode:
Observations of quiescent prominences with the Solar Optical
Telescope on the Hinode satellite have revealed the ubiquitous
existence of downflows forming coherent thin and highly structured
vertically oriented threads with velocities between 10 and 20 km
s-1. Their widths range between 300 and 500 km. They are
often initiated at the top of the visible prominence, but sometimes also
at intermediate level. We propose that the downflows are made of plasma
packets that squeeze themselves through the dominantly horizontal field
under the action of gravity. Their origin is assumed to be hot plasma
supplied from either inside or the immediate vicinity of the prominence
and condensing at its top. Under compression and further cooling,
the matter overflows to the flanks of the prominence dragging its
magnetic field with it. Under the increasing action of gravity, vertical
structures are forming which eventually disconnect from the field of
the inflow channel thus forming finite plasma packets. This process is
reminiscent of water flowing over a mountain ridge and breaking up into
a multitude of droplets. Like water droplets being subject to air drag,
the falling plasma droplets experience a drag force by the horizontal
prominence field and assume a steady vertical velocity. This happens via
the excitation of Alfvén waves. Lateral confinement by the prominence
field determines their spatial extent. The small scales of the droplets
and the directional balance of their internal tangled magnetic fields
can explain the absence of appreciable vertical components in magnetic
field measurements. On the basis of the observed width and vertical
speed of the downflows and by adopting a prominence field of about 8 G,
we derive central density and temperature of the droplets, which turn
out to be quite consistent with known prominence characteristics. In
the formulation of the drag force a dimensionless "magnetic drag
coefficient" has been introduced with a value well below unity.
Title: Small and meso-scale properties of a substorm onset auroral arc
Authors: Frey, H. U.; Amm, O.; Chaston, C. C.; Fu, S.; Haerendel, G.;
Juusola, L.; Karlsson, T.; Lanchester, B.; Nakamura, R.; Østgaard,
N.; Sakanoi, T.; Séran, E.; Whiter, D.; Weygand, J.; Asamura, K.;
Hirahara, M.
Bibcode: 2010JGRA..11510209F
Altcode:
We present small and meso-scale properties of a substorm onset arc
observed simultaneously by the Reimei and THEMIS satellites together
with ground-based observations by the THEMIS GBO system. The optical
observations revealed the slow equatorward motion of the growth-phase
arc and the development of a much brighter onset arc poleward of
it. Both arcs showed the typical particle signature of electrostatic
acceleration in an inverted-V structure together with a strong Alfvén
wave acceleration signature at the poleward edge of the onset arc. Two
THEMIS spacecraft encountered earthward flow bursts around the times
the expanding optical aurora reached their magnetic footprints in
the ionosphere. The particle and field measurements allowed for the
reconstruction of the field-aligned current system and the determination
of plasma properties in the auroral source region. Auroral arc
properties were extracted from the optical and particle measurements and
were used to compare measured values to theoretical predictions of the
electrodynamic model for the generation of auroral arcs. Good agreement
could be reached for the meso-scale arc properties. A qualitative
analysis of the internal structuring of the bright onset arc suggests
the operation of the tearing instability which provides a 'rope-like'
appearance due to advection of the current in the sheared flow across
the arc. We also note that for the observed parameters ionospheric
conductivity gradients due to electron precipitation will be unstable
to the feedback instability in the ionospheric Alfvén resonator that
can drive structuring in luminosity over the range of scales observed.
Title: Equatorward moving arcs and substorm onset
Authors: Haerendel, Gerhard
Bibcode: 2010JGRA..115.7212H
Altcode: 2010JGRA..11507212H
Key observations of phenomena during the growth phase of a substorm
are being reviewed with particular attention to the equatorward motion
of the hydrogen and electron arcs. The dynamic role of the electron,
the so-called growth phase arc, is analyzed. It is part of a current
system of type II that is instrumental in changing the dominantly
equatorward convection from the polar cap into a sunward convection
along the auroral oval. A quantitative model of the arc and associated
current system allows determining the energy required for the flow
change. It is suggested that high-β plasma outflow from the central
current sheet of the tail creates the current generator. Assessment of
the energy supplied in this process proves its sufficiency for driving
the arc system. The equatorward motion of the arcs is interpreted as
a manifestation of the shrinkage of the near-Earth transition region
(NETR) between the dipolar magnetosphere and the highly stretched
tail. This shrinkage is caused by returning magnetic flux to the
dayside magnetosphere as partial replacement of the flux eroded by
frontside reconnection. As the erosion of the NETR is proceeding,
more and more magnetic flux is demanded from the central current sheet
of the near-Earth tail until highly accelerated plasma outflow causes
the current sheet to collapse. Propagation of the collapse along the
tail triggers reconnection and initiates the substorm.
Title: Fascinating Plasma Structures (Jean Dominique Cassini Medal
Lecture)
Authors: Haerendel, Gerhard
Bibcode: 2010EGUGA..12.2123H
Altcode:
In this lecture I will discuss three plasma realms, which have attracted
my particular attention because of their fascinating observable fine
structure and the complex underlying physics. The structure is, of
course, owed to the pervading magnetic field. But it is in particular
the role of magnetic tensions that will be highlighted. The three
plasma phenomena are: (1) cometary plasma tails, where magnetic tensions
transfer momentum from the solar wind under mass loading by the comet;
(2) auroral arcs, which owe their energy influx to the release of
magnetic shear stresses; and (3) solar prominences, in which cool
plasma embedded in the hot corona is subject to a balance of magnetic
shear stresses and gravity. The last subject is a recent topic of
my research and still bears many secrets. Images and movies will be
supplemented by brief characterizations of the key physical processes.
Title: Chromospheric evaporation via Alfvén waves .
Authors: Haerendel, G.
Bibcode: 2010MmSAI..81..653H
Altcode:
We summarize a scenario for the chromospheric evaporation during solar
flares. For details we refer to \citet{haerendel2009}.
Title: A droplet model for downflows in hedgerow prominences
Authors: Haerendel, Gerhard; Berger, Thomas
Bibcode: 2010cosp...38.2915H
Altcode: 2010cosp.meet.2915H
Observations of hedgerow prominences with the Solar Optical Telescope of
the Hinode mission have revealed the ubiquitous existence of downflows
forming coherent thin and highly structured near-vertical threads
with velocities between 10 and 20 km/s. Their widths range between
300 and 500 km. They are often initiated at the top of the visible
prominence, but sometimes also at intermediate level. We propose that
the downflows are made of plasma packets that squeeze themselves through
the dominantly horizontal field under the action of gravity. Their
origin is assumed to be hot plasma either supplied from outside along
the arcade field overarching the prominence and condensing at its top,
or along the spine field of the prominence itself. Under compression
and further cooling, the matter sinks into the prominence dragging
its magnetic field with it, but eventually disconnecting it from the
arcade field thus forming finite packets. The horizontal prominence
field exerts a drag force on the downward moving packets like air on a
falling droplet. Balancing the gravitational and drag forces yields an
upper limit on their length of the order of 1000 km. Lateral pressure
balance limits their width to about 500 km. Pushing themselves at high
speed through the horizontal field, the plasma "droplets" excite a
multitude of incoherent Alfvén waves. Nonlinear interactions of these
waves fill the prominence with a spectrum of oscillatory and propagating
wave modes. Absorption of part of that wave energy, whose ultimate
source is gravitational energy, and radiative cooling constitute the
energy balance of the falling matter and determine the mean fall speed (
14 km/s). The small scales of the "droplets" and thus of their frozen-in
magnetic fields explain the absence of vertical components in magnetic
field measurements. The above estimates of the droplet characteristics
rest on prominence parameters with mean density of 2.5x1012 cm-3,
temperature of 7500 K, and horizontal fields of order 8 G.
Title: Towards a European vision for space exploration:
Recommendations of the Space Advisory Group of the European Commission
Authors: Horneck, Gerda; Coradini, Angioletta; Haerendel, Gerhard;
Kallenrode, May-Britt; Kamoun, Paul; Swings, Jean Pierre; Tobias,
Alberto; Tortora, Jean-Jacques
Bibcode: 2010SpPol..26..109H
Altcode:
As a result of increasing public and political interest in 'space'
(i.e. solar system) exploration at the global scale, the Space Advisory
Group of the European Commission has evaluated the situation in
Europe with regard to its potential to participate in this ambitious
global enterprise. Aspects of science, technology, environment and
safety, society, spin-offs and international cooperation were all
considered. The group concluded that Europe possesses sufficient
key technologies and scientific expertise to play a major role in
international space exploration and has recommended that the EU
take a central role to ensure the success of future European space
exploration, not only to give a clear political signal for the way
forward but also to ensure an appropriate financial framework. In this
way Europe would embrace the spirit of the European Space Policy and
contribute to the knowledge-based society by investing significantly
in space-based science and technology, thereby playing a strong role
in international space exploration.
Title: Auroral Small-and Meso-Scale Structures, Origin and Function
Authors: Frey, H. U.; Amm, O.; Chaston, C. C.; Fu, S.; Haerendel, G.;
Juusola, L.; Karlsson, R.; Lanchester, B. S.; Nakamura, R.; Ostgaard,
N.; Sakanoi, T.; Seran, E.; Whiter, D.
Bibcode: 2009AGUFMSM52B..05F
Altcode:
Discrete auroral arcs regularly display small- and meso-scale
distortions that can appear suddenly and move with speeds that are
not related to plasma speeds in the ionosphere but rather represent
properties of the acceleration processes in the magnetosphere. The
temporal and spatial structure of each small-scale structure is thus
evidence for its distinct dynamic role in the interaction between
the hot magnetospheric and the cold, dense ionospheric plasmas. We
analyzed passes of Reimei and FAST over the network of THEMIS
Ground-Based Observatories (GBO) with all-sky cameras to combine
small- and medium-scale auroral imaging with in-situ measurements of
the precipitating particles in order to determine the properties and
characteristics of auroral arcs and embedded small-scale structures. The
THEMIS or Cluster spacecraft provided additional measurements of
magnetospheric plasma and the GBO magnetometers allowed for the
determination of ionospheric currents and their dynamic changes. The
combination of in-situ and remotely determined auroral arc properties
allowed for the complete characterization of a substorm breakup arc
and embedded small-scale structures. We find consistency between
theoretical expectations and observed values for arc and fold speeds
and dimensions. The leading edge of the breakup arc with Alfvenic
accelerated electrons exhibits the fastest fold speeds while the wider
inverted-V arc shows less structure and internal speeds. Twin vortex
shear flows observed by two of the THEMIS spacecraft are related to
the poleward expansion of the breakup arc, the development of the
substorm current wedge, and the appearance of a strong upward/downward
current system. The scale size and motion of the small-scale structures
signifies the dynamics of the magnetospheric plasma and the acceleration
processes responsible for their generation.
Title: ON THE DOWNFLOWS IN HEDGEROW PROMINENCES
Authors: Berger, T. E.; Haerendel, G.
Bibcode: 2009AGUFMSH44A..07B
Altcode:
We analyze the downflows in quiescent prominences with respect to
width, vertical velocity and acceleration, using sequences of images
from the Solar Optical Telescope (SOT) of the Hinode mission. SOT
sequences in both 656.3 nm H-alpha and 396.8 nm Ca II H-line bandpasses
show that the downflows have typical widths of 300 km, lengths up
to 15 Mm, and speeds on the order of 10--20 km/s. Most downflows
initiate near the top of the visible-light prominence in the form
of bright knots and show an initial acceleration before achieving
relatively constant speeds. Downflows typically end either in the
chromosphere below the prominence or on large arches that sometimes
form lower boundaries to the prominences. In some cases, downflows
are strongly deflected by arches indicating a large gradient in the
magnetic field at those locations. The vertical coherence of most of
the threads over much of the prominence height suggests a continuous
stream of plasma. The frozen-field condition implies the presence of
vertical magnetic field dragged by the downflow with balanced up and
down polarity. This explains the absence of vertical components in
magnetic field measurements. The large-scale horizontal field plays
an important role in the dynamics of the downflow, in two ways. It
compresses the thread plasma and field and presents an obstacle
to the downflow. The energy gained by falling in the gravitational
field is in part expended in stretching the vertical field, in part
in pushing the horizontal field out of the way and in part by covering
the radiative losses of the compressed plasma. With total densities of
the order of nearly 10^12 cm-3 and horizontal fields of order 10 G,
energy and force balance yield vertical velocities of about 10 km/s
and temperatures of 7000-8000 K. The threads are nourished by plasma
inflow from outside the prominence along largely horizontal fields
and sudden onset of gravitational instability.
Title: Fundamental Issues of Auroral Arc Formation (Invited)
Authors: Haerendel, G.
Bibcode: 2009AGUFMSM52B..01H
Altcode:
Auroral forms are not footprints of magnetospheric processes,
but the product of an interaction of the source plasma in the
outer magnetosphere and tail with the ionosphere. Alfvén waves,
quasi-stationary or propagating, are the agent of this interaction. They
transport magnetic shear stresses and energy towards the Earth. Two
principles govern the creation of auroral forms, (1) magnetic stress
release and (2) maximization of the energy deposition. The first has
two channels, auroral particle acceleration above or in the topside
ionosphere and ohmic dissipation through Pedersen currents in the
lower ionosphere. Maximization of the energy conversion is achieved by
impedance matching between the incoming Alfvén wave and the effective
resistance of the auroral acceleration region. The latter has various
forms, depending on current direction and background density. The
typical narrow width of auroral forms is a direct result of the
impedance matching. Even thinner forms can arise from cavity formation
at the interface between ionosphere and lower magnetosphere. The
motion of auroral rays is witness of the release of magnetic shear
stresses. Auroral arcs can be classified as (1) embedded arcs, (2)
Hall generator arcs, and (3) Alfvénic arcs. They are distinguished
by the geometry of the generator forces and currents as well as by
the types of closure currents in the ionosphere.
Title: Chromospheric Evaporation via Alfvén Waves
Authors: Haerendel, Gerhard
Bibcode: 2009ApJ...707..903H
Altcode:
This paper presents a scenario for the chromospheric evaporation
during solar flares, which is inspired by the chain of events leading
to the formation of auroral arcs and ionospheric evacuation during
magnetospheric substorms. The plasma, ejected from high coronal
altitudes during a flare reconnection event, accumulates at the tops
of coronal loops by braking of the reconnection flow, possibly by fast
shock formation. A high-beta layer forms and distorts the magnetic
field. Energy contained in magnetic shear stresses is transported as
Alfvén waves from the loop-top toward the chromosphere. It is shown
that under these conditions the Alfvén waves carry enough energy to
feed the chromospheric evaporation process. The second subject of this
investigation is identification of the most effective energy dumping
or wave dissipation process. Several processes are being analyzed:
ion-neutral collisions, classical and anomalous field-aligned current
dissipation, and critical velocity ionization. All of them are being
discarded, either because they turn out to be insufficient or imply
very unlikely physical properties of the wave modes. It is finally
concluded that turbulent fragmentation of the Alfvén waves entering
the chromosphere can generate the required damping. The basic process
would be phase mixing caused by a strongly inhomogeneous distribution
of Alfvénic phase speed and laminar flow breakup by Kelvin-Helmholtz
(K-H) instability. The filamentary (fibril) structure of the
chromosphere thus appears to be essential for the energy conversion,
in which the K-H instability is the first step in a chain of processes
leading to ion thermalization, electron heating, and neutral particle
ionization. Quantitative estimates suggest that a transverse structure
with scales not far below 100 km suffices to produce strong wave damping
within a few seconds. Nonthermal broadening of some metallic ion lines
observed during the pre-impulsive rise phase of a flare might be a
residue of the turbulent breakup process.
Title: Poleward arcs of the auroral oval during substorms and the
inner edge of the plasma sheet
Authors: Haerendel, Gerhard
Bibcode: 2009JGRA..114.6214H
Altcode: 2009JGRA..11406214H
An analytical model for the connection between the near-Earth edge of
the plasma sheet at substorm onset and the auroral arcs at the poleward
edge of the auroral oval is presented. The connection is established
through the existence of a Boström type I current system. Its generator
is assumed to be constituted by a narrow high-beta plasma layer
located at the interface between the near-Earth plasma sheet and the
outer edge of the near-dipolar field of the magnetosphere. The energy
balance between the downward Poynting flux and the energy conversion
in the auroral acceleration region and ionosphere provides a relation
for the electric fields as a function of the upward field-aligned
current. Only the upward current region is being considered in this
work. An interesting effect, incorporated in the energy balance,
is the feedback of the auroral electrojet on the magnetospheric
plasma by dragging the latter eastward from below under the action
of a Hall generator. Thereby a relation arises between the westward
electric field, tangential to the arc, and the equatorward polarization
field. Quantitative solution of the energy equation is achieved by using
the empirical relations between auroral energy flux and electron energy
and the integrated Hall and Pedersen conductivities. Accommodation
of the downward energy flux requires the existence of a minimum arc
length. The resulting quantities are consistent with typical auroral
data sets. Relating the downward energy flux to the parameters of the
generator reveals a strong dependence of polarization electric field,
overall energy dissipation, and total current strength on the plasma
beta of the generator. The dumping of excess energy from the high-beta
plasma layer into the auroral arc(s) allows the stretched tail field
lines to transform into dipolar field lines. It opens, so-to-speak,
the gate into the outer magnetosphere.
Title: Auroral arc and oval electrodynamics in the Harang region
Authors: Marghitu, O.; Karlsson, T.; Klecker, B.; Haerendel, G.;
McFadden, J.
Bibcode: 2009JGRA..114.3214M
Altcode: 2009JGRA..11403214M
Auroral arcs are typically described in terms of an upward field-aligned
current (FAC) sheet above the arc, connected by ionospheric Pedersen
current to a downward FAC sheet near the arc. On the basis of data
measured by the FAST spacecraft, conjugate with ground optical
observations, we present first a wide and stable winter evening arc,
where this standard model does not apply. The arc is observed in
the Harang region during the growth phase of a modest substorm,
poleward of the convection reversal (CR) boundary. Although the
magnetic field data suggest the typical configuration, the two FAC
sheets appear to be decoupled near the satellite footprint: the upward
FAC is fed by the westward electrojet (WEJ), while the downward FAC
feeds the eastward electrojet (EEJ). The examination of the arc by
the newly developed ALADYN technique confirms this peculiar current
topology. For comparison, we apply ALADYN also to a second evening
arc, located within the Harang region equatorward from the CR. The
arc is confirmed to have the standard configuration, consistent with
a former study, but substantial FAC-EJ coupling is inferred in the
auroral oval both poleward and equatorward of the arc. A key element
for the topology of the current closure is the westward component of
the electric field, which influences the relative location of the CR
with respect to the large-scale FAC reversal (FR) boundary. As proved
by tests on synthetic data, a westward component of the electric field
pushes the CR toward the FR, preventing thus the standard FAC closure,
while the conductance and FAC pattern shape the CR profile. Since a
westward electric field is often measured in the Harang region, the
FAC-EJ coupling is expected to be an essential ingredient there. This
has important implications for the current closure in the equatorial
magnetosphere and for the auroral current circuit in the WEJ region,
closely related to the substorm process.
Title: ESSC-ESF Position Paper-Science-Driven Scenario for Space
Exploration: Report from the European Space Sciences Committee (ESSC)
Authors: Worms, Jean-Claude; Lammer, Helmut; Barucci, Antonella; Beebe,
Reta; Bibring, Jean-Pierre; Blamont, Jacques; Blanc, Michel; Bonnet,
Roger; Brucato, John R.; Chassefière, Eric; Coradini, Angioletta;
Crawford, Ian; Ehrenfreund, Pascale; Falcke, Heino; Gerzer, Rupert;
Grady, Monica; Grande, Manuel; Haerendel, Gerhard; Horneck, Gerda;
Koch, Bernhard; Lobanov, Andreï; Lopez-Moreno, José J.; Marco,
Robert; Norsk, Peter; Rothery, Dave; Swings, Jean-Pierre; Tropea,
Cam; Ulamec, Stephan; Westall, Frances; Zarnecki, John
Bibcode: 2009AsBio...9...23W
Altcode:
In 2005 the then ESA Directorate for Human Spaceflight, Microgravity
and Exploration (D-HME) commissioned a study from the European Science
Foundation's (ESF) European Space Sciences Committee (ESSC) to examine
the science aspects of the Aurora Programme in preparation for the
December 2005 Ministerial Conference of ESA Member States, held in
Berlin. A first interim report was presented to ESA at the second
stakeholders meeting on 30 and 31 May 2005. A second draft report was
made available at the time of the final science stakeholders meeting
on 16 September 2005 in order for ESA to use its recommendations to
prepare the Executive proposal to the Ministerial Conference. The final
ESSC report on that activity came a few months after the Ministerial
Conference (June 2006) and attempted to capture some elements of the new
situation after Berlin, and in the context of the reduction in NASA's
budget that was taking place at that time; e.g., the postponement sine
die of the Mars Sample Return mission. At the time of this study,
ESSC made it clear to ESA that the timeline imposed prior to the
Berlin Conference had not allowed for a proper consultation of the
relevant science community and that this should be corrected in the
near future. In response to that recommendation, ESSC was asked again
in the summer of 2006 to initiate a broad consultation to define a
science-driven scenario for the Aurora Programme. This exercise ran
between October 2006 and May 2007. ESA provided the funding for staff
support, publication costs, and costs related to meetings of a Steering
Group, two meetings of a larger ad hoc group (7 and 8 December 2006
and 8 February 2007), and a final scientific workshop on 15 and 16
May 2007 in Athens. As a result of these meetings a draft report was
produced and examined by the Ad Hoc Group. Following their endorsement
of the report and its approval by the plenary meeting of the ESSC, the
draft report was externally refereed, as is now normal practice with
all ESSC-ESF reports, and amended accordingly. The Ad Hoc Group defined
overarching scientific goals for Europe's exploration programme, dubbed
"Emergence and co-evolution of life with its planetary environments,"
focusing on those targets that can ultimately be reached by humans,
i.e., Mars, the Moon, and Near Earth Objects. Mars was further
recognized as the focus of that programme, with Mars sample return as
the recognized primary goal; furthermore the report clearly states
that Europe should position itself as a major actor in defining and
leading Mars sample return missions. The report is reproduced in
this article. On 26 November 2008 the Ministers of ESA Member States
decided to give a high strategic priority to the robotic exploration
programme of Mars by funding the enhanced ExoMars mission component,
in line therefore with the recommendations from this ESSC-ESF report.
Title: Auroral arcs as current transformers
Authors: Haerendel, Gerhard
Bibcode: 2008JGRA..113.7205H
Altcode:
We treat the effects of an electric field tangential to an auroral arc
on the basis of an analytical model according to which auroral arcs
are energized by the release of magnetic shear stresses and associated
internal energy (Haerendel, 2007). If the tangential field exceeds a
certain (low) threshold, the ionosphere acts as a current generator,
or better transformer, and the magnetosphere as the load. The reason is
that energy supplied by a longitudinal Type I current system, as defined
by Boström in 1964, is transformed into energy of the latitudinal Type
II current system attached to the arc and is mostly consumed by the
auroral acceleration process. Closure of the transformer current in the
upper magnetosphere and energy deposition in form of internal energy
and shear stresses, although small, are crucial for the operation of
this process. It can be visualized as a dragging of magnetic field and
plasma along the arc in the direction of higher magnetospheric pressure
enforced by the electric polarization field. This energy deposition
from below is superimposed on the release of free energy supplied by
the magnetospheric generator. Formulation of this scenario leads to
a set of algebraic equations, whose solution provides quantitative
answers on the interdependence of current closure, energy deposition,
and enhanced auroral energy flux in relation to the imposed tangential
electric field. Contrary to earlier expectations, the polarization field
appears not as a consequence of current blockage, but as manifestation
of its continuation by field-aligned currents and their closure in
the magnetosphere. Another consequence of the energy deposition from
below is a small modification of the arc's proper motion in the ambient
plasma frame. A procedure for evaluating applicable measurements in
terms of the underlying physics is given and a concrete example added.
Title: Chromospheric Evaporation by Pressure-driven Alfven Waves
Authors: Haerendel, Gerhard
Bibcode: 2008cosp...37.1150H
Altcode: 2008cosp.meet.1150H
In analogy to the situation in the near-Earth tail during substorms,
we pursue a flare model in which the hot loop-top plasma, piling up
from the downward reconnection jet, is characterized by high beta (∼1)
and average ion energy substantially above the electron energy. In case
of the magnetosphere, the average ratio is about seven. We envision
flux-tubes with a few thousand km transverse scales, which appear as
post-flare loops when filled with observable plasma due to chromospheric
evaporation. The hot loop-top plasma masses distort the magnetic field,
and the resulting shear stresses propagate as Alfvén waves towards
the solar atmosphere carrying a e substantial amount of momentum and
energy. The lateral flanks of the high-beta plasma concentrations
are unstable and can generate a cascade of small-scale density
perturbations, which act as sources of small-scale Alfvén waves. The
characteristic growth-time of the perturbations e is much shorter than
the travel time of the waves towards the chromosphere and the energy
exchange time between ion and electrons. In spite of a certain amount of
wave reflection at the top of the chromosphere, energy will be quickly
coupled into this region within a few reflection periods. Waves with
transverse scales near 1 km provide the most effective ohmic dissipation
via their associated field-aligned currents. It is demonstrated that
this energy input suffices to heat the chromospheric gas to energies
near 1 keV leading to fast "evaporation" or ablation.
Title: Auroral arcs as sites of magnetic stress release
Authors: Haerendel, Gerhard
Bibcode: 2007JGRA..112.9214H
Altcode: 2007JGRA..11209214H
An analytical model is presented for auroral arcs as the result of a
fast release of magnetic shear stresses. The shear stresses are set
up by a longitudinal convection that is driven by pressure forces in
the outer magnetosphere against the frictional forces exerted in the
lower ionosphere. A distorted-dipole geometry is employed allowing for
high plasma beta near the equator. Steep ledges in the radial pressure
distribution, extending along the direction of convection, are invoked
as the sources of the auroral current sheets. The differential magnetic
energy content of these narrow current sheets is released within a few
Alfvén transit times by the decoupling of the magnetospheric plasma
and field from the ionosphere, owing to the existence of field-aligned
potential drops in the auroral acceleration region, and converted
into kinetic energy of the primary auroral particles. A well-known
current-voltage relation is employed for the formulation of the energy
conversion process. This scenario has two important consequences. (1)
The loss of magnetic energy creates a concomitant decrease of internal
energy of the generator plasma and results in a progression of pressure
ledge and auroral current sheet into the more highly stressed magnetic
field region. This is the reason for the observed proper motion of
auroral arcs with respect to the plasma frame. (2) Plasma and field
undergo a rapid stress relief motion along the arc with large but mostly
reversible displacements. The net displacement, equivalent to a small
S-shaped contribution to the essentially U-shaped potential distribution
above the auroral arc, is consistent with the transit of the field lines
through the progressing current sheet. This scenario is cast into a
set of simple relations expressing the key parameters of auroral arcs,
such as width, energy flux, potential drop, and proper motion. The main
ingredient herein is an auxiliary magnetic perturbation field into which
the main properties of the large-scale current system are condensed. It
corresponds to about twice the transverse magnetic perturbation field
near the arc and thus to the total shear stresses. Two free parameters
are the relative magnitude of the pressure jump at the ledge in the
source plasma and the plasma beta. Matching the quantitative results
of the relations for the arc properties with observed values suggests
pressure jumps of order 10% and beta values between 1 and 5.
Title: ROMAP: Rosetta Magnetometer and Plasma Monitor
Authors: Auster, H. U.; Apathy, I.; Berghofer, G.; Remizov, A.; Roll,
R.; Fornacon, K. H.; Glassmeier, K. H.; Haerendel, G.; Hejja, I.;
Kührt, E.; Magnes, W.; Moehlmann, D.; Motschmann, U.; Richter,
I.; Rosenbauer, H.; Russell, C. T.; Rustenbach, J.; Sauer, K.;
Schwingenschuh, K.; Szemerey, I.; Waesch, R.
Bibcode: 2007SSRv..128..221A
Altcode: 2007SSRv..tmp...29A
The scientific objectives, design and capabilities of the Rosetta
Lander's ROMAP instrument are presented. ROMAP's main scientific goals
are longterm magnetic field and plasma measurements of the surface of
Comet 67P/Churyumov-Gerasimenko in order to study cometary activity
as a function of heliocentric distance, and measurements during
the Lander's descent to investigate the structure of the comet's
remanent magnetisation. The ROMAP fluxgate magnetometer, electrostatic
analyser and Faraday cup measure the magnetic field from 0 to 32 Hz,
ions of up to 8000 keV and electrons of up to 4200 keV. Additional two
types of pressure sensors - Penning and Minipirani - cover a pressure
range from 10−8 to 101 mbar. ROMAP's sensors
and electronics are highly integrated, as required by a combined
field/plasma instrument with less than 1 W power consumption and 1
kg mass.
Title: Cosima High Resolution Time-of-Flight Secondary Ion Mass
Spectrometer for the Analysis of Cometary Dust Particles onboard
Rosetta
Authors: Kissel, J.; Altwegg, K.; Clark, B. C.; Colangeli, L.;
Cottin, H.; Czempiel, S.; Eibl, J.; Engrand, C.; Fehringer, H. M.;
Feuerbacher, B.; Fomenkova, M.; Glasmachers, A.; Greenberg, J. M.;
Grün, E.; Haerendel, G.; Henkel, H.; Hilchenbach, M.; von Hoerner,
H.; Höfner, H.; Hornung, K.; Jessberger, E. K.; Koch, A.; Krüger,
H.; Langevin, Y.; Parigger, P.; Raulin, F.; Rüdenauer, F.; Rynö,
J.; Schmid, E. R.; Schulz, R.; Silén, J.; Steiger, W.; Stephan, T.;
Thirkell, L.; Thomas, R.; Torkar, K.; Utterback, N. G.; Varmuza, K.;
Wanczek, K. P.; Werther, W.; Zscheeg, H.
Bibcode: 2007SSRv..128..823K
Altcode: 2007SSRv..tmp...39K
The ESA mission Rosetta, launched on March 2nd, 2004, carries an
instrument suite to the comet 67P/Churyumov-Gerasimenko. The COmetary
Secondary Ion Mass Anaylzer - COSIMA - is one of three cometary dust
analyzing instruments onboard Rosetta. COSIMA is based on the analytic
measurement method of secondary ion mass spectrometry (SIMS). The
experiment's goal is in-situ analysis of the elemental composition
(and isotopic composition of key elements) of cometary grains. The
chemical characterization will include the main organic components,
present homologous and functional groups, as well as the mineralogical
and petrographical classification of the inorganic phases. All this
analysis is closely related to the chemistry and history of the early
solar system. COSIMA covers a mass range from 1 to 3500 amu with a
mass resolution m/Δm @ 50% of 2000 at mass 100 amu. Cometary dust is
collected on special, metal covered, targets, which are handled by a
target manipulation unit. Once exposed to the cometary dust environment,
the collected dust grains are located on the target by a microscopic
camera. A pulsed primary indium ion beam (among other entities) releases
secondary ions from the dust grains. These ions, either positive or
negative, are selected and accelerated by electrical fields and travel
a well-defined distance through a drift tube and an ion reflector. A
microsphere plate with dedicated amplifier is used to detect the
ions. The arrival times of the ions are digitized, and the mass
spectra of the secondary ions are calculated from these time-of-flight
spectra. Through the instrument commissioning, COSIMA took the very
first SIMS spectra of the targets in space. COSIMA will be the first
instrument applying the SIMS technique in-situ to cometary grain
analysis as Rosetta approaches the comet 67P/Churyumov-Gerasimenko,
after a long journey of 10 years, in 2014.
Title: Exploration needs cooperation
Authors: Haerendel, Gerhard
Bibcode: 2007SpReT.169...32H
Altcode:
No abstract at ADS
Title: Commonalities Between Ionosphere and Chromosphere
Authors: Haerendel, Gerhard
Bibcode: 2007sdeh.book..317H
Altcode:
No abstract at ADS
Title: Commonalities Between Ionosphere and Chromosphere
Authors: Haerendel, Gerhard
Bibcode: 2006SSRv..124..317H
Altcode: 2007SSRv..tmp...46H
Three types of processes, occurring in the weakly ionized plasmas of the
Earth’s ionosphere as well as in the solar chromosphere, are being
compared with each other. The main objective is to elaborate on the
differences introduced primarily by the grossly different magnitudes
of the densities, both with respect to the neutral and, even more so,
to the plasma constituents. This leads to great differences in the
momentum coupling from the plasma to the neutral component and becomes
clear when considering the direct electric current component transverse
to the magnetic field, called “Pedersen current”; in the ionosphere,
which has no quasi-static counterpart in the chromosphere. The three
classes of processes are related to the dynamical response of the two
plasmas to energy influx from below and from above. In the first two
cases, the energy is carried by waves. The third class concerns plasma
erosion or ablation in the two respective regions in reaction to the
injection of high Poynting and/or energetic particle fluxes.
Title: The enigma of auroral spirals
Authors: Haerendel, G.
Bibcode: 2006cosp...36.1991H
Altcode: 2006cosp.meet.1991H
One of the most spectacular forms that the aurora borealis can assume
is the large-scale spiral Spirals are dominantly observed along
the poleward boundary of the auroral oval during active periods Two
concepts have been pursued in explaining their origin and in particular
the counterclockwise sense of rotation of the luminous structures when
viewed along the magnetic field direction An essentially magnetostatic
theory following Hallinan 1976 attributes the spiral pattern to
the twisting of field-lines caused by a centrally located upward
field-aligned current According to Oguti 1981 and followers a clockwise
rotation of the plasma flow produces the anticlockwise structure
There are observations seemingly confirming or contradicting either
theory In this paper it is argued that both concepts are insufficient
in that only parts of the underlying physics are considered Besides
field-aligned currents and plasma flow one has to take into at least
two further aspects The ionospheric conductivity modified by particle
precipitation has an impact on the magnetospheric plasma dynamics
Furthermore auroral arcs are not fixed entities subject to distortions
by plasma flows or twisted field-lines but sites of transient releases
of energy We suggest that auroral spirals are ports of entry or exit
of plasma into or out of the auroral oval This way it can be understood
why a clockwise plasma flow can create an anticlockwise luminous pattern
Title: The FIELDS Instrumentation Package on MMS
Authors: Torbert, R. B.; Ergun, R. E.; Russell, C.; Roux, A.;
Lindqvist, P.; Vaith, H.; Glassmeier, K.; Baumjohann, W.; Torkar,
K.; Steller, M.; Kletzing, C.; Bounds, S.; Eriksson, A.; Andre, M.;
Paschmann, G.; Haerendel, G.; Slavin, J.; Farrell, W.; Anderson,
B.; Westfall, J.; Bylander, L.; Auster, U.; Bouabdellah, A.; Corbel,
C.; Le Contel, O.; Means, J.; Marklund, G.; Quinn, J.; Needell, G.;
Kudirka, F.; Rau, D.; Bodet, D.; Tyler, J.
Bibcode: 2005AGUFMSM23A0392T
Altcode:
One of the most challenging scientific requirements of MMS is to
provide precise measurements of ExB flows and parallel electric
fields within and around the diffusion regions associated with
reconnection. The FIELDS suite as part of the selected SMART payload
will resolve transient structures on scales down to 1 km (sampling
time scales of 1-10 ms), determine boundary orientation and motion,
and detect plasma waves that play a critical role in reconnection. The
FIELDS instrumentation combines the most accurate 3D double-probe
electric-field measurement yet assembled for high-altitude missions
with two precise fluxgate instruments, a set of electric and magnetic
wave detectors, and a flight-proven electron drift instrument in
one integrated package in which time bases are coordinated, offsets
inter-determined, and in-flight calibration performed. This talk
will describe the FIELDS instrumentation and how it will address the
critical measurements that must be performed on MMS to improve our
understanding of the reconnection process.
Title: COSIMA: a High Resolution Time-of-Flight Secondary Ion
Mass Spectrometer for Cometary Dust Particles on Its Way to Comet
67P/Churyumov-Gerasimenkov
Authors: Kissel, J.; Höfner, H.; Haerendel, G.; Czempiel, S.; Eibl,
J.; Henkel, H.; Koch, A.; Glasmachers, A.; Torkar, K.; Rüdenauer, F.;
Steiger, W.; Krueger, F. R.; Jessberger, E. K.; Stephan, T.; Gruen,
E.; Thomas, R.; Langevin, Y.; von Hoerner, H.; Silen, J.; Rynö, J.;
Genzer, M.; Hornung, K.; Schulz, R.; Hilchenbach, M.; Fischer, H.;
Krüger, H.; Tubiana, C.; Thirkell, L.; Varmuza, K.; Cosima Team
Bibcode: 2005LPICo1280...94K
Altcode:
No abstract at ADS
Title: ALADYN: A method to investigate auroral arc electrodynamics
from satellite data
Authors: Marghitu, O.; Klecker, B.; Haerendel, G.; McFadden, J.
Bibcode: 2004JGRA..10911305M
Altcode:
In the simplest representation of an auroral arc current system,
the arc consists of a homogeneous block of increased conductance
infinitely extended in longitudinal direction; field-aligned current
(FAC) sheets that flow in and out of the ionosphere at the boundaries
of the arc are connected through Pedersen current across the arc,
while the electrojet (EJ) that flows along the arc as Hall current
is divergence-free. To evaluate the deviation of the real arc current
system from this ideal configuration, we developed the ALADYN (Auroral
Arc Electrodynamics) method, based on a parametric model of the arc,
that allows the derivation of the parameters by numerical fit to the
experimental data. The method is illustrated with a wide, stable,
winter evening arc, for which both Fast Auroral Snapshot (FAST)
Explorer measurements at 3850 km altitude and ground optical data are
available. We find that in order to obtain consistent results, one has
to take into account, as a minimum, the ionospheric polarization, the
contribution of the Hall current to the meridional closure of the FAC,
and the coupling between the FAC and the EJ.
Title: Subauroral morning proton spots (SAMPS) as a result of
plasmapause-ring-current interaction
Authors: Frey, H. U.; Haerendel, G.; Mende, S. B.; Forrester, W. T.;
Immel, T. J.; ØStgaard, N.
Bibcode: 2004JGRA..10910305F
Altcode:
The proton aurora imager SI-12 on the IMAGE spacecraft occasionally
observes subauroral morning proton spots (SAMPS) that rotate with 70-95%
of the Earth's corotation speed. Coincident particle measurements by
DMSP confirm the source to be pure precipitating protons with mean
energies likely above the detector limit of 30 keV. The spots appear in
the recovery phase after magnetic storms and last for 1-4 hours in the
magnetic local time region of 0300-1200 hours. The latitude location
is strongly related to the minimum Dst of the previous geomagnetic
storm with the lowest latitude observations after the strongest
storms. The rotation speed is related to the latitude (L shell) of
the spots with the largest corotation lags for spots that map to the
largest L shells. IMAGE-EUV observations of the plasmasphere indicate a
relationship with density gradients in the expanding plasmasphere after
magnetic storms. We interpret these spots as the result of wave-particle
interaction. As one likely process, we suggest the interaction of ring
current protons with electromagnetic ion-cyclotron (EMIC) waves as a
result of the expansion and subrotation of the dense, cold plasmasphere
ions. The appearance of subauroral proton spots is therefore a
consequence of the plasmasphere refilling after geomagnetic storms.
Title: Cluster observes formation of high-beta plasma blobs
Authors: Haerendel, G.; Georgescu, E.; Glassmeier, K.; Klecker, B.;
Bogdanova, Y.; Rème, H.; Frey, H.
Bibcode: 2004AnGeo..22.2391H
Altcode:
Available from http://www.copernicus.org/site/EGU/annales/22/7/2391.htm?FrameEngine=false;
Title: The European White Paper on space: enough support for basic
science?
Authors: Worms, J. -C.; Haerendel, G.
Bibcode: 2004SpPol..20...73W
Altcode:
Where is European space science heading? The 'Green Paper on
European Space Policy' served as the main background document for a
European-wide consultation process on space-related issues which took
place in 2003, but none of the 12 questions posed in that document
specifically addressed nor recognised the role of fundamental research
in underpinning any policy for space. As a result of that consultation,
this approach was partly corrected in the European Commission's 'White
Paper' on space, but uncertainties remain. Involvement in first-class
science is absolutely essential for the promotion of European
interests and leadership, as it imparts a strong strategic drive to its
technological and industrial system. This article discusses the contents
of the White Paper and attempts to suggest lines of action concerning
space science in relation with the strategy laid out in that document.
Title: Cometary and Interstellar Dust Analyzer for comet Wild 2
Authors: Kissel, J.; Glasmachers, A.; Grün, E.; Henkel, H.; Höfner,
H.; Haerendel, G.; von Hoerner, H.; Hornung, K.; Jessberger, E. K.;
Krueger, F. R.; Möhlmann, D.; Greenberg, J. M.; Langevin, Y.; Silén,
J.; Brownlee, D.; Clark, B. C.; Hanner, M. S.; Hoerz, F.; Sandford, S.;
Sekanina, Z.; Tsou, P.; Utterback, N. G.; Zolensky, M. E.; Heiss, C.
Bibcode: 2003JGRE..108.8114K
Altcode:
The Cometary and Interstellar Dust Analyzer (CIDA) instrument analyzes
the composition of individual grains in the cometary coma. As each
particle impacts a silver plate, the high-impact energy due to the
relative velocity of the spacecraft as it flies through the coma
causes the elements and molecular compounds in the particle to become
ionized. Using a fast time-of-flight mass spectrometer, a complete set
of ions are detected for each impact, from a mass range of 1 (atomic
hydrogen) up to a few thousand atomic mass units, encompassing all
elements in the periodic table and many molecules, such as organic
compounds. This experimental technique has already been applied with
excellent success at Halley's comet, and the CIDA derivative instrument
is flying on the Stardust mission, which will encounter comet Wild 2
in January of 2004. The data returned will give clues to the elemental
and chemical composition of the dust component of this comet.
Title: Shock aurora: FAST and DMSP observations
Authors: Zhou, X. -Y.; Strangeway, R. J.; Anderson, P. C.; Sibeck,
D. G.; Tsurutani, B. T.; Haerendel, G.; Frey, H. U.; Arballo, J. K.
Bibcode: 2003JGRA..108.8019Z
Altcode:
Global signatures of the aurora caused by interplanetary shocks/pressure
pulses have been studied in recent years using ultraviolet imager
data from polar orbiting spacecraft. The signatures include the
occurrence of the aurora first near local noon and then propagation
antisunward along the auroral oval at very high speeds. To better
understand the mechanisms of particle precipitation, in this paper we
study shock auroras using near-Earth observations of the FAST and DMSP
satellites. We have studied the events that occurred during 1996-2000
where FAST and/or DMSP crossed the dawnside or duskside auroral zone
within 10 min after shocks/pressure pulses arrived at the nose of the
magnetopause. It is found that the electron precipitation increased
significantly above the dawnside and duskside auroral oval zone after
the shock/pressure pulse arrivals. The precipitation structure is
low-energy electrons (<∼1 keV) at higher latitudes (∼75°-83°
ILAT within 0600-0900 MLT) and high-energy electrons (∼1-10 keV)
at lower latitudes (∼65°-79° ILAT) of the auroral zone. There are
a few degrees (1°-4° ILAT) of overlap between these two categories
of precipitated electrons. The precipitation of low-energy electrons
was along highly structured field-aligned currents. The precipitation
of the high-energy electrons was highly isotropic filling the loss
cone. Possible mechanisms of field-aligned current generation are
some dynamic processes occurring on the dayside magnetopause, such as
magnetic shearing, magnetopause perturbation, magnetic reconnection,
and Alfvén wave generation. Adiabatic compression might have caused
the high-energy electron precipitation. On the basis of observations
of FAST and DMSP, shock auroras are speculated to be diffuse auroras
at the lower latitudes of the dayside auroral oval and discrete auroras
on the poleward boundary of the oval with a few latitude degree overlap
of the two types of auroras.
Title: Inductive electromagnetic effects in solar current-carrying
magnetic loops
Authors: Khodachenko, M.; Haerendel, G.; Rucker, H. O.
Bibcode: 2003A&A...401..721K
Altcode:
Effects of electromagnetic inductive interactions in groups of slowly
growing current-carrying loops are studied. Each loop is considered as
an equivalent electric circuit with variable resistivity and inductive
coefficients. These parameters depend on the geometry of the loop, its
position with respect to neighboring loops, as well as on the plasma
temperature and density in the magnetic tube. By means of such a model
the process of generation of currents and temperature change in coronal
loops moving relative to each other, and their dynamic interaction
were studied. There are three main results of this analysis. First,
the possibility of a relatively quick development of a significant
longitudinal current in a rising and initially current-free magnetic
loop is demonstrated. Second, the processes of fast, flare-like,
plasma temperature increase in inductively connected growing loops
with high enough currents, ~ 1010 - 1011 A,
as well as run-away electrons acceleration in the loops by inductive
electric fields are modelled. And third, based on the analysis of
a ponderomotoric interaction of current-carrying magnetic loops,
conditions for their oscillations or a fast change of the loops
inclination, possibly resulting in their coalescence and magnetic
reconnection, are studied. The main characteristics of the oscillatory
dynamics of a loop were calculated.
Title: The Ground-based Calibration of SWS
Authors: Feuchtgruber, H.; Katterloher, R. O.; Jakob, G.; Lutz,
D.; Barl, L.; Bauer, O. H.; Becher, K.; Beintema, D. A.; Boonstra,
A. J.; Boxhoorn, D. R.; Coté, J.; Czempiel, S.; van Dijkhuizen, C.;
de Graauw, T.; Drapatz, S.; Evers, J.; Frericks, M.; Genzel, R.;
Glas, M.; de Groene, P.; Haerendel, G.; Haser, L.; Heras, A. M.;
Horinga, W.; van der Hucht, K. A.; van der Hulst, T.; Huygen, R.;
Jacobs, H.; Kamm, N.; Kampermann, T.; Kester, D. J. M.; Koornneef,
J.; Kunze, D.; Lahuis, F.; Lamers, H. J. G. L. M.; Leech, K.; van der
Lei, S.; van der Linden, R.; Luinge, W.; Melzner, F.; Morris, P. W.;
Ploeger, G. R.; Price, S. D.; Roelfsema, P. R.; Salama, A.; Schaeidt,
S. G.; Sijm, N.; Spakman, J.; Späth, H.; Steinmayer, M.; Stöcker,
J.; Sturm, E.; Valentijn, E. A.; Vandenbussche, B.; Waelkens, C.;
Wesselius, P. R.; Wieprecht, E.; Wiezorrek, E.; Wijnbergen, J. J.;
Wildeman, K.; Young, E.
Bibcode: 2003ESASP.481...67F
Altcode: 2003clim.conf...67F
We present a summary of all ground based SWS instrument tests and
calibrations together with a description of test equipment and
environment. The contents and results of the SWS ground calibration
are discussed and their value for the in-flight calibration of SWS
is demonstrated.
Title: The interstellar environment of the heliosphere
Authors: Breitschwerdt, Dieter; Haerendel, Gerhard
Bibcode: 2003ieh..conf.....B
Altcode:
No abstract at ADS
Title: Conditions for auroral particle acceleration
Authors: Haerendel, G.
Bibcode: 2002AdSpR..30.1763H
Altcode:
Auroral particle acceleration is the result of the appearance of
effective resistance in field-parallel electric currents and of the
voltages needed to overcome them. The basic condition for that to
occur is that the field-aligned current density somewhere in the
system approaches the thermal flux of the background electrons. The
generation of such high-current density is a result of the dynamic
interaction of the magnetospheric and ionospheric plasmas. The free
magnetic energy stored in the current system is converted into kinetic
energy by the auroral acceleration process and, consequently, magnetic
shear stresses are released. Thus auroral acceleration can be seen as
the manifestation of a magnetic elasticity problem in low-beta plasmas,
a problem that may arise in any cosmic system with sufficiently strong
magnetic field. The lecture concentrates on mechanisms for current
concentration and the dynamic consequences of energy conversion and
stress release on the overall system.
Title: Opening Address of the COSPAR President to the COSPAR
Colloquium on Space Weather Study Using Multi-point Techniques
Authors: Haerendel, G.
Bibcode: 2002swsm.confD...7H
Altcode:
No abstract at ADS
Title: Reconnection
Authors: Haerendel, G.
Bibcode: 2002css1.book.1007H
Altcode:
No abstract at ADS
Title: Equator-S observation of reconnection coupled to surface waves
Authors: Nikutowski, B.; Büchner, J.; Otto, A.; Kistler, L. M.;
Korth, A.; Moukis, C.; Haerendel, G.; Baumjohann, W.
Bibcode: 2002AdSpR..29.1129N
Altcode:
In the morning sector of its near equatorial orbit Equator-S observed
large magnetic oscillations in the Pc 5 frequency range. The poloidal
part of the observed oscillations is usually interpreted as being caused
by surface waves of the magnetopause driven by a Kelvin-Helmholtz
instability (KHI). We found, however, that these oscillations are
sometimes additionally superposed with reconnection signatures. This
occurs during periods of northward interplanetary magnetic field. In
fact, the Walen relation as a test for reconnection is satisfied for
many short periods of time. This indicates transient and thin layers
of reconnection, embedded in the large scale motion. We compared our
observations with appropriate magnetohydrodynamic simulations allowing
reconnection in the case of shear flows. Comparing the simulation
results with the magnetic field and plasma observations we found good
agreement of simulations and observations. We conclude that Equator-S
has observed reconnection embedded in Kelvin-Helmholtz instability
generated vortices in its nonlinear phase.
Title: Correlation studies of compressional Pc5 pulsations in space
and Ps6 pulsations on the ground
Authors: Vaivads, A.; Baumjohann, W.; Georgescu, E.; Haerendel, G.;
Nakamura, R.; Lessard, M. R.; Eglitis, P.; Kistler, L. M.; Ergun, R. E.
Bibcode: 2001JGR...10629797V
Altcode:
Compressional Pc5 pulsations in space and Ps6 pulsations on the
ground are common features observed in the morning sector. Here we
use a conjunction study of Equator-S, Geotail, and ground stations in
Canada to show that Ps6 pulsations can be the ground counterpart of
compressional Pc5 pulsations observed by satellites. Because strong
Ps6 pulsations are associated with optical omega-band signatures,
we also suggest that the omega-band counterparts in space might be
compressional pulsations on the Pc5 scale. We also discuss the magnetic
field configuration that makes all these observations consistent.
Title: Simultaneous multispectral imaging of the discrete aurora
Authors: Semeter, Joshua; Lummerzheim, Dirk; Haerendel, Gerhard
Bibcode: 2001JASTP..63.1981S
Altcode: 2001JATP...63.1981S
A unique multispectral imager and an associated multispectral analysis
framework are described which together constitute a new diagnostic
tool for auroral research. By acquiring spatial and spectral data
simultaneously, multispectral imaging allows one to exploit physical
connections between auroral morphology and the auroral optical spectrum
in a way that sequential spectral imaging cannot. The initial research
focus is on imaging the transition in the incident energy spectrum
during the formation of discrete arcs-that is, when the precipitating
population is characterized by <1keV electrons. A technique is
presented which uses two spectral bands (centered at 4278 and 7325Å)
to extend the effective dynamic range of passive imaging to much
lower energies.
Title: The eruptive events on September 30, 1998: 1. The jet
Authors: Bagalá, L. G.; Stenborg, G.; Schwenn, R.; Haerendel, G.
Bibcode: 2001JGR...10625239B
Altcode:
The jet on September 30, 1998, is part of a complex event that
involved also other eruptive phenomena. Changes in the coronal
magnetic field topology were observed during the ejection of the
jet, as deduced from the Fe XIV green line emission. The whole event
was well observed by both the H-Alpha Solar Telescope for Argentina
(HASTA) and the Mirror Coronagraph for Argentina (MICA), which are
installed in the German-Argentinean Solar Observatory at El Leoncito,
Argentina. The Soft X-ray Telescope (SXT) on board Yohkoh also observed
the jet. In this work, observations of the first part of this complex
event showing the evolution of the jet and release of blobs are
presented. Certain features observed are interpreted as signatures
of a magnetic reconnection process in the region. We conclude that
existing theoretical and phenomenological models based on magnetic
reconnection mechanisms could explain our observations, which span
three temperature regimes far apart from each other.
Title: Equator-S magnetopause crossings at high time resolution
Authors: Lucek, E. A.; Cargill, P.; Dunlop, M. W.; Kistler, L. M.;
Balogh, A.; Baumjohann, W.; Fornacon, K. -H.; Georgescu, E.;
Haerendel, G.
Bibcode: 2001JGR...10625409L
Altcode:
The analysis of 37 Equator-S magnetopause crossings with exceptionally
smooth profiles in magnetic field magnitude is presented. The crossings
are distributed through 10 orbits and occur under both northward
and southward interplanetary magnetic field (IMF) conditions. Under
northward IMF, when subsolar reconnection is not believed to occur,
the ramp and the field rotation generally overlap. In all 17 cases
with a southward magnetosheath field, the field rotation to a northward
direction lies sunward of the start of the ramp in field magnitude. Of
these cases, five show a field magnitude dip during the field rotation,
with shorter field rotations tending to be associated with deeper
minima. We suggest that this characteristic of some of the crossings
under southward IMF might reflect the distance of the crossing from
a reconnection site. Field maxima sometimes appear just inside the
magnetopause, but the occurrence of these features is not confined to
those crossings showing field minima in the magnetosheath. Examination
of the field rotation shows that the rotation is rarely circularly
polarized, even when a field magnitude minimum is absent. Comparison
with recent two-dimensional hybrid models shows good qualitative
agreement.
Title: Cluster EDI convection measurements across the high-latitude
plasma sheet boundary at midnight
Authors: Quinn, J. M.; Paschmann, G.; Torbert, R. B.; Vaith, H.;
McIlwain, C. E.; Haerendel, G.; Bauer, O.; Bauer, T. M.; Baumjohann,
W.; Fillius, W.; Foerster, M.; Frey, S.; Georgescu, E.; Kerr, S. S.;
Kletzing, C. A.; Matsui, H.; Puhl-Quinn, P.; Whipple, E. C.
Bibcode: 2001AnGeo..19.1669Q
Altcode:
We examine two crossings of three Cluster satellites from the polar
cap into the high-latitude plasma sheet at midnight local time,
using data from the Electron Drift Instrument (EDI). EDI measures
the full electron drift velocity in the plane perpendicular to the
magnetic field for any field and drift directions. The context of the
measured convection velocities is established by their relation to the
intense enhancements in 1 keV electrons, also measured by EDI, as the
satellites move from the polar cap into the plasma sheet boundary. In
both cases presented here, the cross B convection in the polar cap is
anti-sunward (toward the nightside plasma sheet) with a small duskward
component. As the satellites enter the plasma sheet boundary region,
the dawn-dusk convective flow component reverses its sign, and the
flow in the meridianal plane (toward the center of the plasma sheet)
drops substantially. The relatively stable convection in the polar
cap becomes highly variable as the PSBL is encountered. The timing
and sequence of the boundary crossings by the Cluster satellites
are consistent with a relatively static structure on a time scale of
the few minutes in satellite separations. In one of the two events,
the plasma sheet boundary has a spatially separate structure that is
crossed by the satellites before entering the plasma sheet.
Title: The Electron Drift Instrument on Cluster: overview of first
results
Authors: Paschmann, G.; Quinn, J. M.; Torbert, R. B.; Vaith, H.;
McIlwain, C. E.; Haerendel, G.; Bauer, O. H.; Bauer, T.; Baumjohann,
W.; Fillius, W.; Förster, M.; Frey, S.; Georgescu, E.; Kerr, S. S.;
Kletzing, C. A.; Matsui, H.; Puhl-Quinn, P.; Whipple, E. C.
Bibcode: 2001AnGeo..19.1273P
Altcode:
EDI measures the drift velocity of artificially injected electron
beams. From this drift velocity, the perpendicular electric field
and the local magnetic field gradients can be deduced when employing
different electron energies. The technique requires the injection of
two electron beams at right angles to the magnetic field and the search
for those directions within the plane that return the beams to their
associated detectors after one or more gyrations. The drift velocity
is then derived from the directions of the two beams and/or from the
difference in their times-of-flight, measured via amplitude-modulation
and coding of the emitted electron beams and correlation with the
signal from the returning electrons. After careful adjustment of
the control parameters, the beam recognition algorithms, and the
onboard magnetometer calibrations during the commissioning phase, EDI
is providing excellent data over a wide range of conditions. In this
paper, we present first results in a variety of regions ranging from the
polar cap, across the magnetopause, and well into the magnetosheath.
Key words. Electron drift velocity (electric fields; plasma
convection; instruments and techniques)
Title: Persistent quasiperiodic precipitation of suprathermal ambient
electrons in decaying auroral arcs
Authors: Semeter, Joshua; Vogt, Joachim; Haerendel, Gerhard; Lynch,
Kristina; Arnoldy, Roger
Bibcode: 2001JGR...10612863S
Altcode:
An analysis of ground-based images and rocket-borne electron data from
the Physics of Auroral Zone Electrons II rocket experiment suggests
that suprathermal ambient electrons, precipitating in field-aligned
bursts, may play an active role in regulating the decay of auroral
potential structures. A set of discrete arcs were observed to form in
quasiperiodic succession behind a passing westward traveling surge. The
nascent arcs faded rapidly, losing 90% of their luminosity within
15 s. The fading then abruptly stopped at a brightness consistent
with a peak electron energy of ~1.5 keV. Rocket-borne measurements
of energetic electrons over the residual arcs 2 min later revealed a
superposition of hot isotropic and cold ionospheric electrons, the
latter precipitated in dispersive periodic (3-5 Hz) bursts from a
source altitude of 3000-6000 km. A combined analysis of the optical
and particle data showed that the FAB component (1) was present for
at least 1 min, (2) precipitated in spatial scales of ~10 km and (3)
carried a number flux comparable to that of the overlying isotropic
population. Bulk plasma parameters calculated in the vicinity of the
fading arcs revealed an inverse relationship between parallel potential
drop and number flux carried by the field-aligned population.
Title: Evidence for an extended reconnection line at the dayside
magnetopause
Authors: Phan, T. D.; Freeman, M. P.; Kistler, L. M.; Klecker, B.;
Haerendel, G.; Paschmann, G.; Sonnerup, B. U. Ö.; Baumjohann, W.;
Bavassano-Cattaneo, M. B.; Carlson, C. W.; DiLellis, A. M.; Fornacon,
K. -H.; Frank, L. A.; Fujimoto, M.; Georgescu, E.; Kokubun, S.;
Moebius, E.; Mukai, T.; Paterson, W. R.; Reme, H.
Bibcode: 2001EP&S...53..619P
Altcode:
We report in-situ detection by two spacecraft of oppositely directed
jets of plasma emanating from a magnetic reconnection site at the
Earth's dayside magnetopause, confirming a key element inherent in all
reconnection scenarios. The dual-spacecraft (Equator-S and Geotail)
observations at the flank magnetopause, together with SuperDARNHalley
radar observations of the subsolar cusp region, reveal the presence
of a rather stable and extended reconnection line which lies along the
equatorial magnetopause. These observations were made under persistent
southward interplanetary magnetic field (IMF) conditions, implying
that under these conditions the reconnection sites are determined by
the large-scale interactions between the solar wind magnetic field
and the dayside magnetosphere, rather than by local conditions at
the magnetopause. Control by local conditionswould result in patchy
reconnection, distributed in a less well-organized fashion over the
magnetopause surface.
Title: Inter-comparison of Electric Fields measured by the Electron
Drift Instrument (EDI) and the Electric Field and Waves Instrument
(EFW ) on the CLUSTER Spacecraft
Authors: Torbert, R. B.; Paschmann, G.; Quinn, J.; Mozer, F. S.;
Kistler, L.; Mouikis, C.; Haerendel, G.; Puhl-Quinn, P.; Andre, M.;
Gustafsson, G.; Vaith, H.; Foerster, M.; Georgescu, E.; McIlwain,
C.; Kerr, S.; kletzing, C.; Matsui, H.; Lindqvist, P.; Pedersen, A.;
Fillius, W.
Bibcode: 2001AGUSM..SM21B02T
Altcode:
On CLUSTER, electric fields are measured by the double-probe technique
(EFW) and by the Electron Drift Instrument (EDI). EFW measures the
potential difference between spherical probes spinning in a plane,
and computes the two components of the field in that spin plane. EDI
measures the drift-step vector, which is the displacement of electron
orbits after one gyro-period, and computes the two components of the
field in the plane perpendicular to the magnetic field. Comparison of
the field along the axis which is common to these two planes, shows
very good agreement in many geophysical regions. Combining the two
measurements yields a fully three-dimensional electric field measurement
which we use to determine the electric fields in several interesting
geophysical events seen in the early data from CLUSTER. These electric
field data will be used also to compare with particle flow data in
these events.
Title: Auroral acceleration in astrophysical plasmas
Authors: Haerendel, Gerhard
Bibcode: 2001PhPl....8.2365H
Altcode:
The essentials of the auroral acceleration process are summarized,
and a simple set of relations is derived which enables the analysis
of parallel potential drops and related parameters in relevant
astrophysical systems. The main condition for the occurrence of such
potential drops is the existence of intense field-aligned currents
driven by forces in the outer, weak magnetic fields of an astrophysical
object. In the strong fields near the object the currents may reach
a critical limit where the mirror force or current-driven anomalous
resistivity require the setup of parallel potential drops for the
maintenance of current continuity. Analysis of three candidate systems,
solar flares, cataclysmic variables and accreting neutron stars,
reveals the possibility of fast and efficient production of highly
relativistic electrons manifesting themselves by gamma ray emission.
Title: Initial Results from the Cluster Electron Drift Instrument
Authors: Quinn, J.; Paschmann, G.; Torbert, R.; McIlwain, C.;
Haerendel, G.; Vaith, H.; Puhl-Quinn, P.; Foerster, M.; Georgescu,
E.; Kletzing, C.; Baumjohann, W.; Whipple, E.; Frey, S.; Kerr, S.;
Fillius, W.
Bibcode: 2001AGUSM..SM21B01Q
Altcode:
We present an overview of initial results from the electron drift
instrument (EDI) on the Cluster mission. EDI measures the local electron
drift velocity by firing two weak electron-beams perpendicular to
the magnetic field, and detecting their return after one or more gyro
orbits. Depending on the magnitudes of the drift velocity and magnetic
field, the measurement uses either a time-of-flight or "triangulation"
technique to deduce the drift velocity. EDI inherently measures both
components of the drift velocity in the plane perpendicular to the
magnetic field, indpendent of the orientation of the spacecraft
spin-axis. The measured drift velocity, from which we deduce the
electric field, is usually dominated by the ExB drift. However EDI
uses two different beam energies to identify the grad-B contribution
to the drift.
Title: Compressional Pc5 type pulsations in the morningside plasma
sheet
Authors: Vaivads, A.; Baumjohann, W.; Haerendel, G.; Nakamura, R.;
Kucharek, H.; Klecker, B.; Lessard, M. R.
Bibcode: 2001AnGeo..19..311V
Altcode:
We study compressional pulsations in Pc5 frequency range observed in
the dawn-side at distances of about 10 RE , close to the magnetic
equator. We use data obtained during two events of conjunctions
between Equator-S and Geotail: 1000 1700 UT on 9 March 1998,
and 0200 0600 UT on 25 April 1998. In both events, pulsations are
observed after substorm activity. The pulsations are antisymmetric
with respect to the equatorial plane (even mode), and move eastward
with phase velocity close to plasma velocity. The pulsations tend to
be pressure balanced. We also discuss possible generation mechanisms
of the pulsations.
Title: The magnetopause at high time resolution: Structure and
lower-hybrid waves
Authors: Lucek, E. A.; Cargill, P.; Dunlop, M. W.; Kistler, L. M.;
Balogh, A.; Baumjohann, W.; Fornacon, K. -H.; Georgescu, E.;
Haerendel, G.
Bibcode: 2001GeoRL..28..681L
Altcode:
Equator-S made many magnetopause crossings between 06 00 and 10 40 LT,
taking magnetic field data at 64 or 128 vectors/s. This allows structure
within the shortest crossings to be examined, and examples having an
exceptionally smooth ramp in |B| are presented. These crossings show no
significant structure at sub-kilometre scales. Strong electromagnetic
wave activity did not occur within the ramp, although some crossings
have extremely low amplitude compressional waves in part of the
field ramp close to the magnetosphere, with frequencies close to the
lower hybrid frequency. These initial results suggest that physical
processes on sub-km scales play no role in determining the structure
of the current layer.
Title: The UV aurora and ionospheric flows during flux transfer events
Authors: Neudegg, D. A.; Cowley, S. W. H.; McWilliams, K. A.; Lester,
M.; Yeoman, T. K.; Sigwarth, J.; Haerendel, G.; Baumjohann, W.;
Auster, U.; Fornacon, K. -H.; Georgescu, E.
Bibcode: 2001AnGeo..19..179N
Altcode:
Far Ultra Violet (FUV) signatures in the polar ionosphere during a
period of magnetopause reconnection are compared with ionospheric
flows measured in the cusp ‘throat’ and dusk cell by the CUTLASS
Hankasalmi HF radar. Regions of peak FUV emission in the 130.4 nm
and 135.6 nm range, observed by the Polar spacecraft’s VIS Earth
Camera, consistently lie at the turning point of the flows from the
dusk cell, poleward into the throat, and at the equatorward edge of
the region of high and varied radar spectral-width associated with
the cusp. The Equator-S spacecraft was near the magnetopause at the
time of the ionospheric observations and geomagnetically conjugate
with the region of ionosphere observed by the radar. Flux transfer
events (FTEs), suggestive of bursty reconnection between the IMF and
geomagnetic fields, were observed by Equator-S prior to and during
the periods of high FUV emission. Enhanced poleward ionospheric flow
velocities in the polar cusp region, previously shown to be associated
with bursty reconnection, consistently lie poleward of the enhanced
FUV optical feature. The enhanced optical feature is consistent with
the expected position of the largest upward region 1 field-aligned
current, associated with electron precipitation, on the dusk edge of the
merging gap. The optical feature moves duskward and equatorward during
the course of the reconnection sequence, consistent with expansion
of the merging line and the polar cap with newly added open magnetic
flux by the FTEs. The DMSP F14 spacecraft passed through the enhanced
FUV region and measured strong, structured electron precipitation far
greater than in the adjacent regions.
Title: Interplanetary Shocks, Magnetopause Boundary Layers and
Dayside Auroras: The Importance of a Very Small Magnetospheric Region
Authors: Tsurutani, B. T.; Zhou, X. -Y.; Vasyliunas, V. M.; Haerendel,
G.; Arballo, J. K.; Lakhina, G. S.
Bibcode: 2001SGeo...22..101T
Altcode:
Dayside near-polar auroral brightenings occur when interplanetary shocks
impinge upon the Earth''s magnetosphere. The aurora first brightens near
local noon and then propagates toward dawn and dusk along the auroral
oval. The propagation speed of this wave of auroral light is 10 km s-1
in the ionosphere. This speed is comparable to the solar wind speed
along the outer magnetosphere. The fundamental shock-magnetospheric
interaction occurs at the magnetopause and its boundary layer. Several
physical mechanisms transferring energy from the solar wind directly
to the magnetosphere and from the magnetosphere to the ionosphere
are reviewed. The same physical processes can occur at other solar
system magnetospheres. We use the Haerendel (1994) formulation to
estimate the acceleration of energetic electrons to 50 keV in the
Jovian magnetosphere/ionosphere. Auroral brightenings by shocks could
be used as technique to discover planets in other stellar systems.
Title: IMF-By controlled reconnection at the magnetopause
Authors: Marcucci, M. F.; Bavassano Cattaneo, M. B.; di Lellis, A. M.;
Cerulli Irelli, P.; Kistler, L. M.; Phan, T. -D.; Haerendel, G.
Bibcode: 2001MmSAI..72..614M
Altcode:
We report evidence of a long lasting reconnection event during
which the accelerated plasma flow direction changes in response to an
interplanetary magnetic field (IMF) By reversal, indicating
a change in the reconnection site at the magnetopause. Our observations
confirm that the dayside reconnection configuration is controlled by the
IMF, as opposed to local control, but also stresses the importance of
the IMF dawn-dusk component, in addition to the north-south component,
in determining the global configuration of the reconnection.
Title: Stanislaw Grzedzielski — An appreciation
Authors: Haerendel, G.
Bibcode: 2001CIBu..150...10H
Altcode:
No abstract at ADS
Title: COSPAR colloquium on the interstellar environment of the
heliosphere in honour of Stanislaw Grzedzielski on his retirement
Authors: Breitschwerdt, D.; Haerendel, G.
Bibcode: 2001CIBu..150....8B
Altcode:
No abstract at ADS
Title: The probable chemical nature of interstellar dust particles
detected by CIDA on Stardust
Authors: Kissel, J.; Krüger, F. R.; Silén, J.; Haerendel, G.
Bibcode: 2001ohnf.conf..351K
Altcode:
No abstract at ADS
Title: Physics of Mass Loaded Plasmas
Authors: Szegö, Károly; Glassmeier, Karl-Heinz; Bingham, Robert;
Bogdanov, Alexander; Fischer, Christian; Haerendel, Gerhard; Brinca,
Armando; Cravens, Tom; Dubinin, Eduard; Sauer, Konrad; Fisk, Len;
Gombosi, Tamas; Schwadron, Nathan; Isenberg, Phil; Lee, Martin;
Mazelle, Christian; Möbius, Eberhard; Motschmann, Uwe; Shapiro,
Vitali D.; Tsurutani, Bruce; Zank, Gary
Bibcode: 2000SSRv...94..429S
Altcode:
In space plasmas the phenomenon of mass loading is common. Comets are
one of the most evident objects where mass loading controls to a large
extent the structure and dynamics of its plasma environment. New charged
material is implanted to the fast streaming solar wind by planets,
moons, other solar system objects, and even by the interstellar neutral
gas flowing through our solar system. In this review we summarize both
the current observations and the relevant theoretical approaches. First
we survey the MHD methods, starting with a discussion how mass loading
affects subsonic and supersonic gasdynamics flows, continuing this
with single and multi-fluid MHD approaches to describe the flow when
mass, momentum and energy is added, and we finish this section by
the description of mass loaded shocks. Next we consider the kinetic
approach to the same problem, discussing wave excitations, pitch angle
and energy scattering in linear and quasi-linear approximations. The
different descriptions differ in assumptions and conclusions; we point
out the differences, but it is beyond the scope of the paper to resolve
all the conflicts. Applications of these techniques to comets, planets,
artificial ion releases, and to the interplanetary neutrals are reviewed
in the last section, where observations are also compared with models,
including hybrid simulations as well. We conclude the paper with a
summary of the most important open, yet unsolved questions.
Title: Evidence for interplanetary magnetic field By
controlled large-scale reconnection at the dayside magnetopause
Authors: Marcucci, M. F.; Cattaneo, M. B. Bavassano; Di Lellis,
A. M.; Irelli, P. Cerulli; Kistler, L. M.; Phan, T. -D.; Haerendel,
G.; Klecker, B.; Paschmann, G.; Baumjohann, W.; Möbius, E.; Popecki,
M. A.; Sauvaud, J. A.; Rème, H.; Korth, A.; Eliasson, L.; Carlson,
C. W.; McCarthy, M.; Parks, G. K.
Bibcode: 2000JGR...10527497M
Altcode:
We report evidence of a long-lasting reconnection event during
which the accelerated plasma flow direction changes in response to an
interplanetary magnetic field (IMF) By reversal, indicating
a change in the reconnection site location. The observations were made
by Equator-S on the dawn flank of the magnetopause and consist of a
large number of plasma jets detected mostly within magnetospheric flux
transfer events. The plasma jets were found in quantitative agreement
with the theoretical predictions for reconnection. The reversal of
the plasma flow direction in the jets following the reversal of the
By component not only confirms that the dayside reconnection
configuration is controlled by the IMF, as opposed to local control,
but also stresses the importance of the IMF dawn-dusk component,
in addition to the north-south component, in determining the global
configuration of the reconnection.
Title: First combined observations in the German-Argentinean solar
observatory: correlations in quiet and eruptive phenomena at the limb
Authors: Stenborg, G.; Bagalá, L. G.; Bauer, O. H.; Borda, R. F.;
Francile, C.; Haerendel, G.; Rovira, M. G.; Schwenn, R.
Bibcode: 2000JASTP..62.1553S
Altcode: 2000JATP...62.1553S
This is a first report of combined observations form the solar
instruments at the recently inaugurated German-Argentinean
Solar-Observatory at El Leoncito, San Juan, Argentina. The /Hα
telescope (HASTA) and the mirror coronagraph (MICA) daily image the
solar disk and the inner solar corona respectively with high temporal
and spatial resolution. The excellent weather conditions for solar
studies of the Observatory, and its south equatorial location allow a
complementary summer-condition data with respect to the majority of the
other observatories, mainly located in the northern hemisphere. In this
paper, we present four events in order to study possible correlations
between observations taken by both telescopes. Since each instrument
records data in quite different temperature regimes, correlation between
both set of data appears when the phenomena span a broad range of
temperatures. This is explicitly shown for two of the four set of data
presented here. On the other hand, the four cases are good examples
of the contributions the two instruments can provide to the better
understanding of the mechanisms at work in the inner solar atmosphere.
Title: ICPP: Auroral Acceleration in Astrophysical Plasmas
Authors: Haerendel, Gerhard
Bibcode: 2000APS..DPPGI2006H
Altcode:
The acceleration of electrons in astrophysical systems, such as
supernova remnants, is still an enigma. Although the presence of
highly relativistic electrons manifests itself through synchrotron
or inverse Compton radiation, it remains unclear how they can reach
Lorentz factors of 2000 above which they can be efficiently accelerated
in shock waves. Various proposals have been made how to overcome the
so-called injection problem. In view of this lack of understanding,
it is surprising how little attention has been paid to the auroral
acceleration process in the wider astrophysical context. By summarising
the basic ingredients of this process and casting them into simply
applicable relations, it will be shown how field-aligned potential
drops may be set up in the environment of magnetised stars. This can
make them efficient accelerators of highly relativistic electrons
manifesting themselves as gamma-ray sources. Particular attention
will be given to field-aligned particle acceleration in solar flares,
which appears to be the nearest realisation of the auroral process
operating in a hot stellar environment.
Title: Compressional Pc5 pulsations as sloshing in the plasma sheet
Authors: Vaivads, A.; Haerendel, G.; Baumjohann, W.; Nakamura, R.;
Kucharek, H.; Georgescu, E.; Klecker, B.; Kistler, L. M.
Bibcode: 2000JGR...10523287V
Altcode:
In the morningside plasma sheet close to the equatorial plane,
satellites often observe magnetic field amplitude variations on
timescales of several minutes (Pc5 range). Here we present an event
study which shows that in some cases these variations can be a result
of magnetospheric regions with different magnetic field amplitudes
sloshing back and forth past the satellite. The sloshing is caused by
toroidal Alfvén oscillations.
Title: MHD effects triggered by beams of charged particles in solar
magnetic tubes and their possible relation to plasma heating during
solar flares.
Authors: Khodachenko, M. L.; Haerendel, G.; Rieger, E.
Bibcode: 2000BAAS...32R.821K
Altcode:
No abstract at ADS
Title: MHD Effects Triggered by Beams of Charged Particles in Solar
Magnetic Tubes and Their Possible Relation to Plasma Heating during
Solar Flares
Authors: Khodachenko, M. L.; Haerendel, G.; Rieger, E.
Bibcode: 2000SPD....31.0256K
Altcode:
MHD reaction of plasma on the low solar atmosphere to a changing
current system of a flaring magnetic tube, containing a beam of fast
non-thermal electrons, is studied. We estimate locally the disturbances
of a current system of magnetic tube when the beam is injected into
it, using the classical idea of a return current. We note that any
changes of current density in magnetic tube change the Joule heating
and disturb thermodynamical equilibrium of the tube. Heating of
plasma destroys as well the force balance and starts the process of
a complex dynamics of the whole plasma-magnetic structure. Impulsive
character of a beam injection causes two natural stages of dynamical
behavior of the tube. In the first one, characterized by the presence
of a beam, the preliminary equilibrium state of the magnetic tube is
disturbed and the complex dynamics of plasma starts in the region of
beam propagation, during the second stage, when injection of the beam
is already over, plasma and magnetic field continue to evolve from
the disturbed state and gradually relax to the equilibrium state. The
dynamical behavior of a magnetic tube is studied on the basis of known
self-similar solutions of plasma MHD. M.L.Khodachenko is grateful to
the Max-Planck-Gesellschaft for the research fellowship supporting
his work in 1999-2001 years.
Title: Magnetospheric lion roars
Authors: Baumjohann, W.; Georgescu, E.; Fornacon, K. -H.; Auster,
H. U.; Treumann, R. A.; Haerendel, G.
Bibcode: 2000AnGeo..18..406B
Altcode:
The Equator-S magnetometer is very sensitive and has a sampling
rate normally of 128 Hz. The high sampling rate for the first time
allows detection of ELF waves between the ion cyclotron and the
lower hybrid frequencies in the equatorial dawnside magnetosphere. The
characteristics of these waves are virtually identical to the lion roars
typically seen at the bottom of the magnetic troughs of magnetosheath
mirror waves. The magnetospheric lion roars are near-monochromatic
packets of electron whistler waves lasting for a few wave cycles only,
typically 0.2 s. They are right-hand circularly polarized waves with
typical amplitudes of 0.5 nT at around one tenth of the electron
gyrofrequency. The cone angle between wave vector and ambient field
is nearly always smaller than 1°.
Title: A survey of magnetopause FTEs and associated flow bursts in
the polar ionosphere
Authors: Neudegg, D. A.; Cowley, S. W. H.; Milan, S. E.; Yeoman, T. K.;
Lester, M.; Provan, G.; Haerendel, G.; Baumjohann, W.; Nikutowski,
B.; Büchner, J.; Auster, U.; Fornacon, K. -H.; Georgescu, E.
Bibcode: 2000AnGeo..18..416N
Altcode:
Using the Equator-S spacecraft and SuperDARN HF radars an extensive
survey of bursty reconnection at the magnetopause and associated
flows in the polar ionosphere has been conducted. Flux transfer
event (FTE) signatures were identified in the Equator-S magnetometer
data during periods of magnetopause contact in January and February
1998. Assuming the effects of the FTEs propagate to the polar ionosphere
as geomagnetic field-aligned-currents and associated Alfvén-waves,
appropriate field mappings to the fields-of-view of SuperDARN radars
were performed. The radars observed discrete ionospheric flow channel
events (FCEs) of the type previously assumed to be related to pulse
reconnection. Such FCEs were associated with sim80% of the FTEs and the
two signatures are shown to be statistically associated with greater
than 99% confidence. Exemplary case studies highlight the nature of the
ionospheric flows and their relation to the high latitude convection
pattern, the association methodology, and the problems caused by
instrument limitations.
Title: Extended magnetic reconnection at the Earth's magnetopause
from detection of bi-directional jets
Authors: Phan, T. D.; Kistler, L. M.; Klecker, B.; Haerendel, G.;
Paschmann, G.; Sonnerup, B. U. Ö.; Baumjohann, W.; Bavassano-Cattaneo,
M. B.; Carlson, C. W.; DiLellis, A. M.; Fornacon, K. -H.; Frank,
L. A.; Fujimoto, M.; Georgescu, E.; Kokubun, S.; Moebius, E.; Mukai,
T.; Øieroset, M.; Paterson, W. R.; Reme, H.
Bibcode: 2000Natur.404..848P
Altcode:
Magnetic reconnection is a process that converts magnetic energy into
bi-directional plasma jets; it is believed to be the dominant process by
which solar-wind energy enters the Earth's magnetosphere. This energy
is subsequently dissipated by magnetic storms and aurorae. Previous
single-spacecraft observations revealed only single jets at the
magnetopause-while the existence of a counter-streaming jet was
implicitly assumed, no experimental confirmation was available. Here we
report in situ two-spacecraft observations of bi-directional jets at the
magnetopause, finding evidence for a stable and extended reconnection
line; the latter implies substantial entry of the solar wind into
the magnetosphere. We conclude that reconnection is determined by
large-scale interactions between the solar wind and the magnetosphere,
rather than by local conditions at the magnetopause.
Title: High- and low-altitude observations of adiabatic parameters
associated with auroral electron acceleration
Authors: Shiokawa, K.; Baumjohann, W.; Haerendel, G.; Fukunishi, H.
Bibcode: 2000JGR...105.2541S
Altcode:
Electron density and temperature, adiabatic thermal current,
and field-aligned conductivity have been estimated on the basis
of observations by the Defense Meteorological Satellite Program
(DMSP) satellites above the auroral oval and from measurement by the
Active Magnetospheric Particle Tracer Explorers/Ion Release Module
(IRM) satellite in the near-Earth plasma sheet. We found that the
estimated densities are comparable between these two satellites,
while the temperatures obtained from an accelerated Maxwellian
fitting procedure used on the DMSP spectra are far lower than those
measured by IRM in the near-Earth plasma sheet. From this temperature
discrepancy we conclude that the accelerated electrons do not come from
the equatorial plane of the magnetosphere but from the region just
above the field-aligned potential difference at an altitude of a few
RE. The DMSP data show that a large field-aligned potential
difference, which accelerates auroral electrons downward, is formed in
the region with low field-aligned conductivity. The IRM data show that
the field-aligned conductivity decreases with increasing XGSM
distance, increasing AE index, and after earthward high-speed flow
passage. The adiabatic thermal current estimated from the IRM data is
found to be not enough to supply typical auroral current. Though the
mechanism that produces field-aligned potential difference has not been
identified yet, these results suggest that field-aligned potential
difference is formed to keep the balance between the field-aligned
current generated by magnetospheric processes and the current carried
away from the generator region by accelerated electrons.
Title: EQUATOR-S: The Mission and First Coordinated Measurements
with Geotail
Authors: Haerendel, G.
Bibcode: 2000AdSpR..25.1277H
Altcode:
An overview of the origin of the EQUATOR-S mission, the spacecraft
development and the mission history is given. In spite of its short
operational life of only five months, the major goals were fulfilled,
except that its contribution to IASTP science is restricted to the
morning sector of the outer magnetosphere. A few data sets illustrating
the satellite's capability are presented.
Title: Outstanding Issues in Understanding the Dynamics of the Inner
Plasma Sheet and Ring Current During Storms and Substorms
Authors: Haerendel, G.
Bibcode: 2000AdSpR..25.2379H
Altcode:
The paper deals with five selected issues of the dynamical coupling of
the near-Earth plasma sheet and magnetosphere, (1) substorm initiation,
(2) dipolarization, (3) pressure release of the outer magnetosphere
via the auroral energy conversion process, (4) magnetization of the
very high beta plasma assembling at the inner edge of the tail, and
(5) penetration of energetic particles into the ring current below L
≅ 4. One outstanding and strongly debated subject is not discussed
here, the origin of the substorm current wedge. The main conclusions
(or personal preferences) are: (1) the substorm is initiated by
formation of a near-Earth neutral line; (2) dipolarization occurs
through magnetic flux transport by the earthward reconnection flow and
not by current diffusion; (3) the auroral energy conversion process, the
``auroral pressure valve'', contributes substantially to the pressure
release during the substorms; (4) high beta (> 10) plasma breaks
up into smaller scale blobs under slow magnetization; and (5) deep
and prolonged penetration of hot plasma sheet plasma into the middle
magnetosphere produces currents and electric fields which lead to the
growth of the storm-time ring current
Title: Testing electric field models using ring current ion energy
spectra from the Equator-S ion composition (ESIC) instrument
Authors: Kistler, L. M.; Klecker, B.; Jordanova, V. K.; Möbius, E.;
Popecki, M. A.; Patel, D.; Sauvaud, J. A.; Rème, H.; di Lellis,
A. M.; Korth, A.; McCarthy, M.; Cerulli, R.; Bavassano Cattaneo,
M. B.; Eliasson, L.; Carlson, C. W.; Parks, G. K.; Paschmann, G.;
Baumjohann, W.; Haerendel, G.
Bibcode: 1999AnGeo..17.1611K
Altcode:
During the main and early recovery phase of a geomagnetic storm on
February 18, 1998, the Equator-S ion composition instrument (ESIC)
observed spectral features which typically represent the differences
in loss along the drift path in the energy range (5-15 keV/e) where
the drift changes from being E × B dominated to being gradient and
curvature drift dominated. We compare the expected energy spectra
modeled using a Volland-Stern electric field and a Weimer electric
field, assuming charge exchange along the drift path, with the observed
energy spectra for H+ and O+. We find that using the Weimer electric
field gives much better agreement with the spectral features, and with
the observed losses. Neither model, however, accurately predicts the
energies of the observed minima.
Title: CDS/SOHO Observations of Abundance Variations and
Doppler-Shifts in Active Regions NOAA-8208
Authors: Rank, G.; Czaykowska, A.; Bagalá, L. G.; Haerendel, G.
Bibcode: 1999ESASP.448..349R
Altcode: 1999ESPM....9..349R; 1999mfsp.conf..349R
No abstract at ADS
Title: Introduction: The Equator-S mission
Authors: Haerendel, G.; Torbert, R. B.; Höfner, H.
Bibcode: 1999AnGeo..17.1499H
Altcode:
In spite of its short operational life of only five months, the
major goals of the Equator-S mission were fulfilled, except that its
contribution to the ISTP science is restricted to the morning sector
of the outer magnetosphere. A set of twelve papers following this
introduction is a first documentation of the achievements. They span
from the successful testing and operation of the most advanced and
complex way of measuring electric fields in a hot plasma environment
by means of electron beams, to various investigations at or near the
equatorial magnetopause and in the plasma sheet.
Title: Magnetopause boundary structure deduced from the high-time
resolution particle experiment on the Equator-S spacecraft
Authors: Parks, G. K.; Datta, S.; McCarthy, M.; Lin, R. P.; Reme,
H.; Sauvaud, J. A.; Sanderson, T.; Baumjohann, W.; Haerendel, G.;
Torkar, K.
Bibcode: 1999AnGeo..17.1574P
Altcode:
An electrostatic analyser (ESA) onboard the Equator-S spacecraft
operating in coordination with a potential control device (PCD) has
obtained the first accurate electron energy spectrum with energies
approx7 eV-100 eV in the vicinity of the magnetopause. On 8 January,
1998, a solar wind pressure increase pushed the magnetopause inward,
leaving the Equator-S spacecraft in the magnetosheath. On the return
into the magnetosphere approximately 80 min later, the magnetopause
was observed by the ESA and the solid state telescopes (the SSTs
detected electrons and ions with energies approx20-300 keV). The
high time resolution (3 s) data from ESA and SST show the boundary
region contains of multiple plasma sources that appear to evolve in
space and time. We show that electrons with energies approx7 eV-100 eV
permeate the outer regions of the magnetosphere, from the magnetopause
to approx6Re. Pitch-angle distributions of approx20-300 keV electrons
show the electrons travel in both directions along the magnetic field
with a peak at 90176 indicating a trapped configuration. The IMF during
this interval was dominated by Bx and By components with a small Bz.
Title: EDI electron time-of-flight measurements on Equator-S
Authors: Paschmann, G.; Sckopke, N.; Vaith, H.; Quinn, J. M.; Bauer,
O. H.; Baumjohann, W.; Fillius, W.; Haerendel, G.; Kerr, S. S.;
Kletzing, C. A.; Lynch, K.; McIlwain, C. E.; Torbert, R. B.; Whipple,
E. C.
Bibcode: 1999AnGeo..17.1513P
Altcode:
We present the first electron time-of-flight measurements obtained with
the Electron Drift Instrument (EDI) on Equator-S. These measurements are
made possible by amplitude-modulation and coding of the emitted electron
beams and correlation with the signal from the returning electrons. The
purpose of the time-of-flight measurements is twofold. First, they
provide the drift velocity, and thus the electric field, when the
distance the electrons drift in a gyro period becomes sufficiently
large. Second, they provide the gyro time of the electrons emitted by
the instrument, and thus the magnitude of the ambient magnetic field,
allowing in-flight calibration of the flux-gate magnetometer with high
precision. Results of both applications are discussed.
Title: Waveform and packet structure of lion roars
Authors: Baumjohann, W.; Treumann, R. A.; Georgescu, E.; Haerendel,
G.; Fornacon, K. -H.; Auster, U.
Bibcode: 1999AnGeo..17.1528B
Altcode:
The Equator-S magnetometer is very sensitive and has a sampling
rate of normally 128 Hz. The high sampling rate allows for the first
time fluxgate magnetometer measurements of ELF waves between the ion
cyclotron and the lower hybrid frequencies in the equatorial dayside
magnetosheath. The so-called lion roars, typically seen by the Equator-S
magnetometer at the bottom of the magnetic troughs of magnetosheath
mirror waves, are near-monochromatic packets of electron whistler
waves lasting for a few wave cycles only, typically 0.25 s. They are
right-hand circularly polarized waves with typical amplitudes of 0.5-1
nT at around one tenth of the electron gyrofrequency. The cone angle
between wave vector and ambient field is usually smaller than 1.5°.
Title: Dynamics and local boundary properties of the dawn-side
magnetopause under conditions observed by Equator-S
Authors: Dunlop, M. W.; Balogh, A.; Baumjohann, W.; Haerendel, G.;
Fornacon, K. -H.; Georgescu, E.; Nakamura, R.; Kokubin, S.
Bibcode: 1999AnGeo..17.1535D
Altcode:
Magnetic field measurements, taken by the magnetometer experiment (MAM)
on board the German Equator-S spacecraft, have been used to identify and
categorise 131 crossings of the dawn-side magnetopause at low latitude,
providing unusual, long duration coverage of the adjacent magnetospheric
regions and near magnetosheath. The crossings occurred on 31 orbits,
providing unbiased coverage over the full range of local magnetic
shear from 06:00 to 10:40 LT. Apogee extent places the spacecraft in
conditions associated with intermediate, rather than low, solar wind
dynamic pressure, as it processes into the flank region. The apogee
of the spacecraft remains close to the magnetopause for mean solar
wind pressure. The occurrence of the magnetopause encounters are
summarised and are found to compare well with predicted boundary
location, where solar wind conditions are known. Most scale with
solar wind pressure. Magnetopause shape is also documented and we
find that the magnetopause orientation is consistently sunward of a
model boundary and is not accounted for by IMF or local magnetic shear
conditions. A number of well-established crossings, particularly those
at high magnetic shear, or exhibiting unusually high-pressure states,
were observed and have been analysed for their boundary characteristics
and some details of their boundary and near magnetosheath properties
are discussed. Of particular note are the occurrence of mirror-like
signatures in the adjacent magnetosheath during a significant fraction
of the encounters and a high number of multiple crossings over a long
time period. The latter is facilitated by the spacecraft orbit which
is designed to remain in the near magnetosheath for average solar wind
pressure. For most encounters, a well-ordered, tangential (draped)
magnetosheath field is observed and there is little evidence of large
deviations in local boundary orientations. Two passes corresponding to
close conjunctions of the Geotail spacecraft are analysed to confirm
boundary orientation and motion. These further show evidence of an
anti-sunward moving depression on the magnetopause (which is much
smaller at Equator-S). The Tsyganenko model field is used routinely to
assist in categorising the crossings and some comparison of models is
carried out. We note that typically the T87 model fits the data better
than the T89 model during conditions of low to intermediate KP index
near the magnetopause and also near the dawn-side tail current sheet
in the dawnside region.
Title: EDI convection measurements at 5-6 R E in the post-midnight
region
Authors: Quinn, J. M.; Paschmann, G.; Sckopke, N.; Jordanova, V. K.;
Vaith, H.; Bauer, O. H.; Baumjohann, W.; Fillius, W.; Haerendel, G.;
Kerr, S. S.; Kletzing, C. A.; Lynch, K.; McIlwain, C. E.; Torbert,
R. B.; Whipple, E. C.
Bibcode: 1999AnGeo..17.1503Q
Altcode:
We present the first triangulation measurements of electric fields with
the electron drift instrument (EDI) on Equator-S. We show results from
five high-data-rate passes of the satellite through the near-midnight
equatorial region, at geocentric distances of approximately 5-6 RE,
during geomagnetically quiet conditions. In a co-rotating frame of
reference, the measured electric fields have magnitudes of a few tenths
of mV/m, with the E × B drift generally directed sunward but with
large variations. Temporal variations of the electric field on time
scales of several seconds to minutes are large compared to the average
magnitude. Comparisons of the DC baseline of the EDI-measured electric
fields with the mapped Weimer ionospheric model and the Rowland and
Wygant CRRES measurements yield reasonable agreement.
Title: Identification of magnetosheath mirror modes in Equator-S
magnetic field data
Authors: Lucek, E. A.; Dunlop, M. W.; Balogh, A.; Cargill, P.;
Baumjohann, W.; Georgescu, E.; Haerendel, G.; Fornacon, K. -H.
Bibcode: 1999AnGeo..17.1560L
Altcode:
Between December 1997 and March 1998 Equator-S made a number of
excursions into the dawn-side magnetosheath, over a range of local times
between 6:00 and 10:40 LT. Clear mirror-like structures, characterised
by compressive fluctuations in |B| on occasion lasting for up to 5 h,
were observed during a significant fraction of these orbits. During
most of these passes the satellite appeared to remain close to the
magnetopause (within 1-2 Re), during sustained compressions of the
magnetosphere, and so the characteristics of the mirror structures
are used as a diagnostic of magnetosheath structure close to the
magnetopause during these orbits. It is found that in the majority of
cases mirror-like activity persists, undamped, to within a few minutes
of the magnetopause, with no observable ramp in |B|, irrespective
of the magnetic shear across the boundary. This suggests that any
plasma depletion layer is typically of narrow extent or absent at
the location of the satellite, at least during the subset of orbits
containing strong magnetosheath mirror-mode signatures. Power spectra
for the mirror signatures show predominately field aligned power, a
well defined shoulder at around 3-10 × 10-2 Hz and decreasing power at
higher frequencies. On occasions the fluctuations are more sinusoidal,
leading to peaked spectra instead of a shoulder. In all cases mirror
structures are found to lie approximately parallel to the observed
magnetopause boundary. There is some indication that the amplitude
of the compressional fluctuations tends to be greater closer to the
magnetopause. This has not been previously reported in the Earth's
magnetosphere, but has been suggested in the case of other planets.
Title: High-beta plasma blobs in the morningside plasma sheet
Authors: Haerendel, G.; Baumjohann, W.; Georgescu, E.; Nakamura, R.;
Kistler, L. M.; Klecker, B.; Kucharek, H.; Vaivads, A.; Mukai, T.;
Kokubun, S.
Bibcode: 1999AnGeo..17.1592H
Altcode:
Equator-S frequently encountered, i.e. on 30% of the orbits between
1 March and 17 April 1998, strong variations of the magnetic field
strength of typically 5-15-min duration outside about 9RE during the
late-night/early-morning hours. Very high-plasma beta values were
found, varying between 1 and 10 or more. Close conjunctions between
Equator-S and Geotail revealed the spatial structure of these plasma
blobs and their lifetime. They are typically 5-10° wide in longitude
and have an antisymmetric plasma or magnetic pressure distribution with
respect to the equator, while being altogether low-latitude phenomena
(< 15°). They drift slowly sunward, exchange plasma across the
equator and have a lifetime of at least 15-30 min. While their spatial
structure may be due to some sort of mirror instability, little is
known about the origin of the high-beta plasma. It is speculated that
the morningside boundary layer somewhat further tailward may be the
source of this plasma. This would be consistent with the preference of
the plasma blobs to occur during quiet conditions, although they are
also found during substorm periods. The relation to auroral phenomena
in the morningside oval is uncertain. The energy deposition may be
mostly too weak to generate a visible signature. However, patchy aurora
remains a candidate for more disturbed periods.
Title: The magnetic field experiment onboard Equator-S and its
scientific possibilities
Authors: Fornacon, K. -H.; Auster, H. U.; Georgescu, E.; Baumjohann,
W.; Glassmeier, K. -H.; Haerendel, G.; Rustenbach, J.; Dunlop, M.
Bibcode: 1999AnGeo..17.1521F
Altcode:
The special feature of the ringcore fluxgate magnetometer on
Equator-S is the high time and field resolution. The scientific
aim of the experiment is the investigation of waves in the 10-100
picotesla range with a time resolution up to 64 Hz. The instrument
characteristics and the influence of the spacecraft on the magnetic
field measurement will be discussed. The work shows that the applied
pre- and inflight calibration techniques are sufficient to suppress
spacecraft interferences. The offset in spin axis direction was
determined for the first time with an independent field measurement
by the Equator-S Electron Drift Instrument. The data presented gives
an impression of the accuracy of the measurement.
Title: Multi-wavelength Observations of the September 30, 1998 Event
at the German-Argentinian Solar Observatory
Authors: Bagalá, L. G.; Stenborg, G.; Schwenn, R.; Bauer, O. H.;
Fernández Borda, R.; Haerendel, G.
Bibcode: 1999ESASP.448..959B
Altcode: 1999mfsp.conf..959B; 1999ESPM....9..959B
No abstract at ADS
Title: Substorm observations in the early morning sector with
Equator-S and Geotail
Authors: Nakamura, R.; Haerendel, G.; Baumjohann, W.; Vaivads, A.;
Kucharek, H.; Klecker, B.; Georgescu, E.; Birn, J.; Kistler, L. M.;
Mukai, T.; Kokubun, S.; Eglitis, P.; Frank, L. A.; Sigwarth, J. B.
Bibcode: 1999AnGeo..17.1602N
Altcode:
Data from Equator-S and Geotail are used to study the dynamics of the
plasma sheet observed during a substorm with multiple intensifications
on 25 April 1998, when both spacecraft were located in the early morning
sector (03-04 MLT) at a radial distance of 10-11 RE. In association
with the onset of a poleward expansion of the aurora and the westward
electrojet in the premidnight and midnight sector, both satellites in
the morning sector observed plasma sheet thinning and changes toward
a more tail-like field configuration. During the subsequent poleward
expansion in a wider local time sector (20-04 MLT), on the other
hand, the magnetic field configuration at both satellites changed
into a more dipolar configuration and both satellites encountered
again the hot plasma sheet. High-speed plasma flows with velocities
of up to 600 km/s and lasting 2-5 min were observed in the plasma
sheet and near its boundary during this plasma sheet expansion. These
high-speed flows included significant dawn-dusk flows and had a shear
structure. They may have been produced by an induced electric field
at the local dipolarization region and/or by an enhanced pressure
gradient associated with the injection in the midnight plasma sheet.
Title: The New Hα Solar Telescope at the German-Argentinian Solar
Observatory
Authors: Bagalá, L. G.; Bauer, O. H.; Fernández Borda, R.; Francile,
C.; Haerendel, G.; Rieger, R.; Rovira, M. G.
Bibcode: 1999ESASP.448..469B
Altcode: 1999ESPM....9..469B; 1999mfsp.conf..469B
No abstract at ADS
Title: Abundance Variations and Flows in Plage Regions Observed
with CDS/SOHO
Authors: Rank, G.; Bagalá, L. G.; Czaykowska, A.; Haerendel, G.
Bibcode: 1999ESASP.446..561R
Altcode: 1999soho....8..561R
We present results from CDS/SOHO observations of the spotless active
region NOAA-8208, obtained on 28th April 1998 near disk center. MDI
images show a bipolar magnetic configuration. The regions of enhanced
He I emission correspond to the areas with strong magnetic flux and
also with bright plage areas seen in Ca II and H-alpha images. A high
correlation is found between intensity maps of the transition region
lines He I (logTmax = 4.3), O III (logTmax = 5.0), and O V (logTmax =
5.4). The line-of-sight velocities of He I reveal a strong downflow in
the plage areas. Further, the line-of-sight velocities of He I, O III,
and O V are well correlated, showing that the downflow pattern exists
up to temperatures of about 0.25 MK. At higher temperatures (Mg VIII
at logTmax = 5.8) this flow is not detected, suggesting that material
streams into the plage region from sideways in the high transition
region. Maps of the electron density in the transition region have been
constructed from several line ratios yielding densities of about 9.0
cm-3 in the plage regions, about dex 0.5 cm-3
higher compared to the surrounding. To study the spatial variation of
the first ionization potential (FIP) effect, the abundance ratio has
been mapped for the ion ratio MgVI/NeVI. The ratio is highly variable
on spatial scales down to a few arcsec from photospheric values to
enhancements of a factor of 10. The strongest FIP enhancements are not
correlated with transition region line emission, but are found outside
of the plage regions. Some areas of strong FIP enhancement appear
stretched and elongated, suggesting that the material is confined in
loop-like structures.
Title: Flow braking and the substorm current wedge
Authors: Birn, J.; Hesse, M.; Haerendel, G.; Baumjohann, W.;
Shiokawa, K.
Bibcode: 1999JGR...10419895B
Altcode:
Recent models of magnetotail activity have associated the braking of
earthward flow with dipolarization and the reduction and diversion
of cross-tail current, that is, the signatures of the substorm
current wedge. Estimates of the magnitude of the diverted current by
Haerendel [1992] and Shiokawa et al. [1997, 1998] tend to be lower
than results from computer simulations of magnetotail reconnection
and tail collapse [Birn and Hesse, 1996], despite similar underlying
models. An analysis of the differences between these estimates on
the basis of the simulations gives a more refined picture of the
diversion of perpendicular into parallel currents. The inertial currents
considered by Haerendel [1992] and Shiokawa et al. [1997] contribute
to the initial current reduction and diversion, but the dominant and
more permanent contribution stems from the pressure gradient terms,
which change in connection with the field collapse and distortion. The
major effect results from pressure gradients in the z direction,
rather than from the azimuthal gradients [Shiokawa et al., 1998],
combined with changes in By and Bx. The reduction
of the current density near the equatorial plane is associated with a
reduction of the curvature drift which overcompensates changes of the
magnetization current and of the gradient B drift current. In contrast
to the inertial current effects, the pressure gradient effects persist
even after the burst of earthward flow ends.
Title: Dawnside magnetopause observed by the Equator-S Magnetic
Field Experiment: Identification and survey of crossings
Authors: Dunlop, M. W.; Balogh, A.; Baumjohann, W.; Haerendel, G.;
Fornacon, K. -H.; Georgescu, E.
Bibcode: 1999JGR...10417491D
Altcode:
The German Equator-S spacecraft provided long-duration, low-latitude
coverage of the dawnside magnetopause and adjacent magnetosheath. We
document 131 magnetopause crossings from 31 orbits, giving coverage from
0600 to 1040 LT and exhibiting a wide range of local magnetic shear. The
Tsyganenko model field is used routinely to assist identification and
in categorizing the crossings. The apogee of the spacecraft remains
close to the magnetopause for mean solar wind pressure. Consequently,
magnetosheath intervals often extending several hours are observed,
many containing a high number of crossings. For most encounters, a
well-ordered, tangential (draped) magnetosheath field is observed;
30% containing extended intervals of strong mirror signatures. The
occurrence of the crossings is summarized, and locations are found
to compare well to predicted boundary positions using observed,
upstream solar wind IMF and pressure values; some corresponding to
unusually high solar wind ram pressure. Other crossing characteristics
have also been analyzed, such as boundary normals. Although these
are broadly consistent with fitted, model magnetopause orientations,
they typically lie sunward of these, suggesting a blunter magnetopause
shape in this region than predicated. No strong evidence is found of
large deviations in local boundary orientations, possibly consistent
with the highly draped magnetosheath field configuration.
Title: Shear velocity profiles associated with auroral curls
Authors: Vogt, J.; Frey, H. U.; Haerendel, G.; Höfner, H.; Semeter,
J. L.
Bibcode: 1999JGR...10417277V
Altcode:
Optical observations using high-resolution television cameras frequently
show that auroral curls are associated with shear velocities in
the apparent optical flow. The present study examines in detail
one particular curl system event which happened to yield sufficient
resolution to determine the fine structure of velocity and vorticity
profiles by means of a new analysis technique. Those observations
of curl system evolution are contrasted with large velocity shear
events where small-scale quasiperiodic distortions were subject to
sudden decay rather than development into vortices. The results are
discussed in light of an electrostatic picture of auroral acceleration
and the Kelvin-Helmholtz instability model. We suggest that the latter
cannot fully explain the nonlinear phase of the observed curl system
event and that curl models should take auroral acceleration processes
into account.
Title: Mirror mode structures observed in the dawn-side magnetosheath
by Equator-S
Authors: Lucek, E. A.; Dunlop, M. W.; Balogh, A.; Cargill, P.;
Baumjohann, W.; Georgescu, E.; Haerendel, G.; Fornacon, K. -H.
Bibcode: 1999GeoRL..26.2159L
Altcode:
The Equator-S satellite was ideally positioned to make magnetic
field observations in the dawn-side magnetosheath, relatively close
to the magnetopause. The magnetosheath data were particularly rich in
compressional signatures, consistent with mirror mode structures, which
occurred during ∼30% of orbits crossing into the magnetosheath. In
most, although not all cases, strongly compressive signatures
extended up to the magnetopause boundary, with no increase in the
underlying magnetic field magnitude on the time scale of ten to thirty
minutes. The proximity and character of mirror-like fluctuations near
the magnetopause suggest that in the dawn-side magnetosheath the plasma
depletion layer (PDL) is of narrower extent than is generally observed
closer to the subsolar point, or is absent.
Title: The Age of NGC 6426, a Metal-poor Globular Cluster in the
Galactic Halo
Authors: Hatzidimitriou, D.; Papadakis, I.; Croke, B. F. W.;
Papamastorakis, I.; Paleologou, E. V.; Xanthopoulos, E.; Haerendel, G.
Bibcode: 1999AJ....117.3059H
Altcode:
We present B, V, R, and I photometry of the metal-poor globular
cluster in the galactic halo, NGC 6426. The observations were
performed using the 1.3 m Telescope at Skinakas Observatory in
Crete. We derived the reddening of the cluster to be E(B-V)=0.39+/-0.02
[E(V-I)=0.53+/-0.03]. The metal abundance of the cluster was estimated
from the shape of the red giant branch following the techniques
by Sarajedini and by Da Costa & Armandroff. It was found to
be [Fe/H]=-2.33+/-0.15 dex. The mean V magnitude of the RR Lyrae
variables found in the cluster is 18.14+/-0.02 (based on a paper
in preparation). The resulting distance modulus of the cluster is
16.41+/-0.07. Finally, we derived the relative age of NGC 6426. Using
the methodology of Harris et al., we found that NGC 6426 is marginally
older than M92 (by ~=0.7 Gyr). Following the Chaboyer, Demarque, &
Sarajedini method we found NGC 6426 to have the same age as the mean
metal-poor globular cluster of the galactic halo.
Title: A flux transfer event observed at the magnetopause by the
Equator-S spacecraft and in the ionosphere by the CUTLASS HF radar
Authors: Neudegg, D. A.; Yeoman, T. K.; Cowley, S. W. H.; Provan,
G.; Haerendel, G.; Baumjohann, W.; Auster, U.; Fornacon, K. -H.;
Georgescu, E.; Owen, C. J.
Bibcode: 1999AnGeo..17..707N
Altcode:
Observations of a flux transfer event (FTE) have been made
simultaneously by the Equator-S spacecraft near the dayside magnetopause
whilst corresponding transient plasma flows were seen in the
near-conjugate polar ionosphere by the CUTLASS Finland HF radar. Prior
to the occurrence of the FTE, the magnetometer on the WIND spacecraft
~226 RE upstream of the Earth in the solar wind detected a southward
turning of the interplanetary magnetic field (IMF) which is estimated to
have reached the subsolar magnetopause ~77 min later. Shortly afterwards
the Equator-S magnetometer observed a typical bipolar FTE signature in
the magnetic field component normal to the magnetopause, just inside
the magnetosphere. Almost simultaneously the CUTLASS Finland radar
observed a strong transient flow in the F region plasma between 78°
and 83° magnetic latitude, near the ionospheric region predicted to
map along geomagnetic field lines to the spacecraft. The flow signature
(and the data set as a whole) is found to be fully consistent with the
view that the FTE was formed by a burst of magnetopause reconnection.
Title: MPE Jahresbericht 1998 / Annual report 1998.
Authors: Haerendel, G.
Bibcode: 1999mpja.book.....H
Altcode:
No abstract at ADS
Title: Origin and dynamics of thin auroral arcs
Authors: Haerendel, G.
Bibcode: 1999AdSpR..23.1637H
Altcode:
Thin auroral structures are discussed from the side of observations,
basic auroral arc theory and the non-linear response of the topside
ionosphere. The reported structures of widths down to ~ 100 m are likely
to be embedded in broader luminous regions. Determination of their width
depends sensitively on the imaging contrast. The basic theory of auroral
arcs, which attributes the energy carried by the primary electrons to
the conversion of electromagnetic energy via field-aligned potential
drops above the topside ionosphere, is incapable of reconciling the
observed energies and current densities with narrow widths. The lowest
values it allows for lie near 5 km. It is suggested that cool plasma,
eroded at the boundaries of propagating auroral acceleration regions,
creates upwelling ion tongues of narrow widths which are the sites of
additional potentials drops, energy conversion and shear flows. They
may well underlie the formation of thin auroral substructures.
Title: First ELF wave measurements with the Equator-S magnetometer
Authors: Baumjohann, W.; Haerendel, G.; Treumann, R. A.; Bauer,
T. M.; Rustenbach, J.; Georgescu, E.; Auster, U.; Fornacon, K. H.;
Glaßmeier, K. -H.; Lühr, H.; Büchner, J.; Nikutowski, B.; Balogh,
A.; Cowley, S. W. H.
Bibcode: 1999AdSpR..24...77B
Altcode:
The magnetometer onboard the Equator-S satellite is very sensitive and
has a high sampling rate of up to 128 Hz. These specifications allow
for the first fluxgate magnetometer measurements of ELF waves between
the ion cyclotron and the lower hybrid frequencies in the equatorial
dayside magnetosheath. The so-called lion roars, typically seen by
the Equator-S magnetometer at the bottom of the magnetic troughs of
magnetosheath mirror waves, are near-monochromatic packets of electron
whistler waves lasting for 0.2-1 sec. They are right-hand circularly
polarized shear waves with typical amplitudes of 0.5-1 nT at frequencies
of 15-40 Hz, i.e., around one tenth of the electron gyrofrequency.
Title: Keynote address
Authors: Haerendel, Gerhard
Bibcode: 1999msrt.conf....3H
Altcode:
This chapter discusses the importance of small and mini-satellites
in space research. These tools have a role complementary to that
of big observatories and space probes, adding flexibility, short
lead-times, and an alternate means of procurement and of sharing
responsibility. For many tasks in astronomy, solar system research,
and Earth observations, big missions will be indispensable and,
after careful analysis, may prove to be more cost effective than a
number of small missions accomplishing the same work. The world has
witnessed successful launches of important space projects, such as the
National Aeronautics and Space Administration/European Space Agency
(NASA/ESA) Cassini/Huygens mission to Saturn and its satellite Titan
and the deployment of the Haruka space radio-telescope by Institute of
Space and Astronautical Science (ISAS), the space segment of the MLBI
Observatory. The Italian-Dutch Beppo-SAX satellite for X-ray astronomy
detected the X-ray afterglow of gamma-ray bursts, combined with optical
and radio data. It positively proved, after three decades of debate,
that these enigmatic bursts originate at cosmological distances.
Title: Max-Planck-Institut für extraterrestrische
Physik. Jahresbericht für 1998.
Authors: Haerendel, G.
Bibcode: 1999MitAG..82..269H
Altcode:
No abstract at ADS
Title: Keynote Address
Authors: Haerendel, Gerhard
Bibcode: 1999mart.conf....3H
Altcode:
No abstract at ADS
Title: A model for the reflection of Alfvén waves at the source
region of the Birkeland current system: The tau generator
Authors: Vogt, J.; Haerendel, G.; Glassmeier, K. H.
Bibcode: 1999JGR...104..269V
Altcode:
The source region of the Birkeland current system, also called the
generator of the auroral current circuit, is probably located in the
outer equatorial magnetosphere on closed magnetic field lines. Alfvén
waves have often been suggested as carriers for field-aligned currents,
momentum, and electromagnetic energy which is converted to particle
kinetic energy and ohmic heat at the polar end of the auroral flux
tubes. In this report we present a model for the interaction of Alfvén
waves with the plasma in the generator region: the tau generator. We
show that existing concepts like current and voltage generators
correspond to extreme values of the intrinsic parameter τ. A frequency
dependent reflection coefficient can be found which has considerable
effect on the evolution of magnetospheric oscillations. Furthermore,
we discuss the physical significance of the parameter τ and relate
it to some measure for the effective height of the generator region.
Title: Telescopio Solar en Hα (HASTA)
Authors: Fernández Borda, R.; Francile, C.; Bagala, G.; Bauer, O.;
Haerendel, G.; Rieger, E.; Rovira, M.
Bibcode: 1999BAAA...43...79F
Altcode:
El Telescopio Solar en Hα (Hα Solar Telescope for Argentina (-HASTA-)
fue recientemente instalado en la Estación Astronómica de Altura
Carlos Ulrrico Cesco (OAFA) en El Leoncito. Este instrumento estudiará
la evolución de las fulguraciones solares desde tierra con alta
resolución temporal y espacial. HASTA es un telescopio refractor de
110 mm con una distancia focal de 165 cm, un filtro Lyot sintonizable
(±1Å) con un ancho de banda de 0.3 Å y una cámara CCD de alta
resolución (1280×1024 pixels). Todo el conjunto es controlado en
forma remota por una PC, la cual además adquiere datos del Sistema de
Posicionamiento Global (GPS) y de la estación meteorológica. Diseñado
para detectar fulguraciones, el instrumento trabaja en dos modos
(patrullaje y fulguración) con una resolución espacial de 1.5 arcseg
por pixel y una resolución temporal de 2 seg. HASTA comenzó a operar
en Mayo de 1998 y, junto con otros tres instrumentos solares, que se
están instalando o se instalaron, harán de El Leoncito un polo de
observación solar importante en el Hemisferio Sur.
Title: Equator-S: Mission and first results
Authors: Baumjohann, W.; Haerendel, G.
Bibcode: 1999ASIC..537....1B
Altcode: 1999iip..conf....1B
No abstract at ADS
Title: Weakly damped Alfven waves as drivers for spicules
Authors: de Pontieu, B.; Haerendel, G.
Bibcode: 1998A&A...338..729D
Altcode:
We present an analytical model for the damping of Alfven waves in
the partially ionized chromosphere. The damping is due to collisions
between ions and neutrals. The ion-neutral collision frequency in this
environment is such that the ion and neutral populations are almost
perfectly collisionally coupled, leading the Alfven wave to behave as
if it acts on the whole plasma (i.e. including neutrals). The small
but finite coupling time between ions and neutrals leads to damping of
the Alfven waves. We find that this type of damping of upward traveling
Alfven waves with frequencies between 0.2 and 0.6 Hz, can cause not only
significant heating but also upward motion of the upper chromospheric
plasma. In addition the upward force and heating associated with this
type of damping can sustain, both dynamically and thermodynamically,
an already formed chromospheric spicule. The energy flux carried by
the Alfven waves needed for this type of support of a spicule does
not seem to be in contradiction with observational and theoretical
evidence for the presence of Alfven waves in the chromosphere.
Title: Reply [to “Comment on ‘Braking of high-speed flows in the
near-Earth Tail’ by K. Shiokawa, W. Baumjohann, and G. Haerendel”]
Authors: Haerendel, G.; Shiokawa, K.; Baumjohann, W.
Bibcode: 1998GeoRL..25.3503H
Altcode:
No abstract at ADS
Title: MPE Jahresbericht 1997 / 1997 Annual report.
Authors: Haerendel, G.
Bibcode: 1998mpja.book.....H
Altcode:
No abstract at ADS
Title: Azimuthal pressure gradient as driving force of substorm
currents
Authors: Shiokawa, K.; Haerendel, G.; Baumjohann, W.
Bibcode: 1998GeoRL..25..959S
Altcode:
We have studied the azimuthal pressure gradient in the central plasma
sheet during substorms using plasma and magnetic field data obtained
by the AMPTE/IRM satellite at nightside in radial distances of 9-15
RE. The pressure gradient is statistically estimated for
the interval when the magnetic field shows a dipolar configuration
(elevation angle >45°). It is found that by this criterion,
most data are obtained during and after the passage of high-speed
ion flow in the vicinity of the neutral sheet during magnetically
active times. We show that there is an azimuthal gradient of plasma
pressure in the dipolar field region. The pressure gradient can drive
a substantial amount of field-aligned current (4.1×105 A
per 2-hour local time sector). We suggest that this current is a source
of the substorm current system after the high-speed ion flow stops.
Title: Freja and ground-based analysis of inverted-V events
Authors: Frey, H. U.; Haerendel, G.; Clemmons, J. H.; Bochm, M. H.;
Vogt, J.; Bauer, O. H.; Wallis, D. D.; Blomberg, L.; Lühr, H.
Bibcode: 1998JGR...103.4303F
Altcode:
During two campaigns, ground-based auroral observations were performed
in coordination with Freja. The high temporal and spatial resolution
of the satellite instruments as well as the real-time recording with a
stereoscopic camera system from the ground enabled detailed comparison
of small- and large-scale optical phenomena with particle and field data
measured by the satellite. Three passes of the satellite over inverted-V
auroral arcs and over precipitation regions with strong field-aligned
electron spectra are investigated. Brightness modulations within auroral
arcs coincide with modulations of primary electron fluxes. The dynamics
of small-scale structures within arcs as well as the proper motion of
arcs are analyzed and compared with electric fields measured by the
satellite and with BARS radar measurements. Energy fluxes independently
determined from the ground and from the satellite are used to calculate
the field-aligned conductance. The results agree with predictions of
the kinetic theory of the mirror force, if we allow for variations of
the density and thermal energy of the electrons in the source region
of the magnetosphere. Detailed comparison of electron spectra and
electric and magnetic field perturbations provide evidence of different
acceleration mechanisms for the electrons, electrostatic acceleration
inside inverted-V's, and wave acceleration in transient regions.
Title: Introduction to special section: The Freja Mission
Authors: Lundin, Rickard; Haerendel, Gerhard; Grahn, Sven
Bibcode: 1998JGR...103.4119L
Altcode:
Freja was a joint Swedish and German scientific satellite project
to study the interaction between hot magnetospheric plasma and the
topside atmosphere/ionosphere. Freja was launched on October 6, 1992,
and it operated successfully during 4 years until October 1996 when
the command system ceased to work. Freja enabled high temporal/spatial
resolution measurements of auroral plasma characteristics. With a
high telemetry rate (520 kbit/s) and ~15Mbyte distributed onboard
memories Freja could resolve mesoscale and microscale phenomena in
the 100 m range for particles and the 1-10 m range for electric and
magnetic fields. Novel plasma instruments enabled Freja to increase the
spatial/temporal resolution orders of magnitudes above that achieved by
its predecessors. The main scientific objective of Freja was to study
the interaction between the hot magnetospheric plasma with the topside
atmosphere/ionosphere. This interaction leads to a strong energization
of magnetospheric and ionospheric plasma and an associated erosion,
and loss, of matter from the Terrestrial exosphere. Freja orbited
with an altitude of ~600-1750km, thus covering the lower part of
the auroral acceleration region. This altitude range hosts processes
that heat and energize the ionospheric plasma above the auroral zone,
leading to the escape of ionospheric plasma and the formation of large
density cavities.
Title: High-speed ion flow, substorm current wedge, and multiple Pi
2 pulsations
Authors: Shiokawa, K.; Baumjohann, W.; Haerendel, G.; Paschmann,
G.; Fennell, J. F.; Friis-Christensen, E.; Lühr, H.; Reeves, G. D.;
Russell, C. T.; Sutcliffe, P. R.; Takahashi, K.
Bibcode: 1998JGR...103.4491S
Altcode:
We have studied the onset timing of earthward high-speed ion flow
observed by the AMPTE/IRM satellite at 12.3 Earth radii (RE)
and 0100 MLT in the central plasma sheet during an isolated substorm
event on March 1, 1985. The timing of this onset is compared with that
of the substorm current wedge and Pi 2 magnetic pulsations observed
by a large number of ground-based stations and the AMPTE/CCE, GOES 5,
and ISEE 1 satellites and with that of high-energy particle injection
observed at Los Alamos geosynchronous satellite 1982-019. The onset
of earthward high-speed flow is observed 3 min before the onset
of the global current wedge formation and 6 min before the onset of
high-energy particle injection. The three bursts of the high-speed flow
observed at AMPTE/IRM are likely to correspond to three compressional
pulses observed at AMPTE/CCE at 6 RE and three Pi 2 wave
packets observed at midlatitude ground stations. On the basis of these
observations we conclude that the substorm current wedge is caused
by inertia current and the current due to flow shear at the braking
point of the earthward high-speed flow during the initial stage of the
substorm expansion phase. The braking point is well separated from the
near-Earth neutral line. It is also suggested that the compressional
pulses and fluctuations of field-aligned currents generated at the flow
braking point can be the initial cause of the Pi 2 magnetic pulsations
in the inner magnetosphere.
Title: Reflection and transmission of Alfvén waves at the auroral
acceleration region
Authors: Vogt, J.; Haerendel, G.
Bibcode: 1998GeoRL..25..277V
Altcode:
Alfvén waves transfer field-aligned currents, momentum and energy
from the source region in the equatorial magnetosphere along Earth's
magnetic field lines to the polar ionosphere and play therefore an
important role in auroral electrodynamics. The parallel potential
drop of some kV in the auroral acceleration region (AAR) at altitudes
of some 1000 km has considerable effect on the propagation of these
waves. The purpose of this report is to investigate the reflection
and transmission properties of the AAR in the frame of a thin sheet
approximation. Combining key relations of auroral electrodynamics with
the requirement of current continuity results in an easy-to-handle
physical description of the problem. The model provides an opportunity
to study different acceleration mechanisms. It turns out that the
reflection properties of the auroral zone depends strongly on the
perpendicular scale length of the incident wave.
Title: Max-Planck-Institut für extraterrestrische
Physik. Jahresbericht für 1997.
Authors: Haerendel, G.
Bibcode: 1998MitAG..81..229H
Altcode:
No abstract at ADS
Title: 40 Years of COSPAR
Authors: Haerendel, G.; Grzedzielski, S.; Cavallo, G.; Battrick, B.
Bibcode: 1998fyc..conf.....H
Altcode:
No abstract at ADS
Title: Braking of High-Speed Flow and Azimuthal Pressure Gradient
as Driving Forces of Substorm Currents
Authors: Shiokawa, K.; Baumjohann, W.; Haerendel, G.
Bibcode: 1998ASSL..238..355S
Altcode: 1998subs.conf..355S
No abstract at ADS
Title: What is the Role of the Inner Magnetosphere During Substorms?
Authors: Reeves, G. D.; Haerendel, G.
Bibcode: 1998ASSL..238..743R
Altcode: 1998subs.conf..743R
No abstract at ADS
Title: Plasma Flow and Critical Velocity Ionization in Cometary Comae
(GRL 13(3) 1986)
Authors: Haerendel, Gerhard
Bibcode: 1998coen.book..202H
Altcode:
No abstract at ADS
Title: Opening address of the cospar president to the cospar
colloquium on magnetospheric research with advanced techniques
Authors: Haerendel, G.
Bibcode: 1998mrat.conf....3H
Altcode:
COSPAR has been conceived at the beginning of the space era to promote
space research and related applications with emphasis on the exchange
of results, information, and opinions. By concentrating on data,
methods, and scientific insights, COSPAR has always managed to keep
clear of political interference, on the contrary, to build bridges
across political barriers. After the fall of the iron curtain, the
bridging function of COSPAR in the area of space research may appear
to have lost importance; however, several barriers continue to exist
and new challenges are emerging that need the platform offered by
the COSPAR committee to bring together colleagues form East and West,
from South and North, from poor and rich, and from well-established
and newly entering space-faring nations. The COSPAR conference is
meant as a forum for concerned space agencies, other institutions,
and administration with the aim to establish closer cooperation and
to learn from each other in science and applications.
Title: New Wavelength Determinations of Mid-Infrared Fine-structure
Lines by Infrared Space Observatory Short Wavelength Spectrometer
Authors: Feuchtgruber, H.; Lutz, D.; Beintema, D. A.; Valentijn,
E. A.; Bauer, O. H.; Boxhoorn, D. R.; De Graauw, Th.; Haser, L. N.;
Haerendel, G.; Heras, A. M.; Katterloher, R. O.; Kester, D. J. M.;
Lahuis, F.; Leech, K. J.; Morris, P. W.; Roelfsema, P. R.; Salama,
A.; Schaeidt, S. G.; Spoon, H. W. W.; Vandenbussche, B.; Wieprecht, E.
Bibcode: 1997ApJ...487..962F
Altcode:
We report accurate new wavelengths for 29 mid-infrared ionic
fine-structure lines, based on observations with the Short Wavelength
Spectrometer (SWS) on board the Infrared Space Observatory (ISO). Our
results originate from observations of NGC 7027, NGC 6543, NGC 6302,
the Circinus galaxy, Sgr A West, and W51 IRS 2. The obtained accuracies
(λ/Δλ) range from 3 × 104 to 1 × 105,
depending on instrumental mode and uncertainty in radial velocities. Based on observations made with ISO, an ESA project with instruments
funded by ESA Member States (especially the PI countries: France,
Germany, The Netherlands, and the United Kingdom) and with the
participation of ISAS and NASA. The SWS is a joint project of SRON
and MPE.
Title: The distribution of stars and dust in spiral galaxies: the
edge-on spiral UGC 2048.
Authors: Xilouris, E. M.; Kylafis, N. D.; Papamastorakis, J.;
Paleologou, E. V.; Haerendel, G.
Bibcode: 1997A&A...325..135X
Altcode:
We compare B, V, I surface photometry of the edge-on spiral galaxy UGC
2048 with corresponding surface photometry calculated from a realistic
model of spiral galaxies, taking into account both absorption and
scattering by dust. Our goal is to determine the distribution of stars
and dust in the galaxy from the observed surface photometry. In the
model that we use we assume that the stars and the dust in the disk
are distributed axisymmetrically and exponentially in both directions,
the radial and the perpendicular to the plane of the disk. The de
Vaucouleurs R^1/4^ law and the modified Hubble profile are used to fit
the central region of the galaxy and a comparison is made between the
two. For UGC 2048 we have found a face-on central optical depth of less
than one in all three bands. This means that, if the galaxy were seen
face-on, it would be transparent in the optical region of the spectrum,
despite the prominent dust lane seen in the edge-on picture. We have
also determined the scalelengths and scaleheights of the stars and
the dust in the disk, the bulge characteristics and the inclination
angle of the galaxy.
Title: ASPI experiment: measurements of fields and waves on board
the INTERBALL-1 spacecraft
Authors: Klimov, S.; Romanov, S.; Amata, E.; Blecki, J.; Büchner, J.;
Juchniewicz, J.; Rustenbach, J.; Triska, P.; Woolliscroft, L. J. C.;
Savin, S.; Afanas'yev, Yu.; de Angelis, U.; Auster, U.; Bellucci, G.;
Best, A.; Farnik, F.; Formisano, V.; Gough, P.; Grard, R.; Grushin, V.;
Haerendel, G.; Ivchenko, V.; Korepanov, V.; Lehmann, H.; Nikutowski,
B.; Nozdrachev, M.; Orsini, S.; Parrot, M.; Petrukovich, A.; Rauch,
J. L.; Sauer, K.; Skalsky, A.; Slominski, J.; Trotignon, J. G.; Vojta,
J.; Wronowski, R.
Bibcode: 1997AnGeo..15..514K
Altcode:
The plasma-wave experiment ASPI (analysis of spectra of plasma waves
and instabilities) on board the INTERBALL spacecraft is a combined
wave diagnostics experiment. It performs measurements of the DC and
AC magnetic field vector by flux-gate and search-coil sensors, the DC
and AC electric field vector by Langmuir double probes and the plasma
current by Langmuir split probe. Preliminary data analysis shows the
low noise levels of the sensors and the compatibility of new data with
the results of previous missions. During several months of in-orbit
operation a rich collection of data was acquired, examples of which
at the magnetopause and plasma sheet are presented in second part of
the paper.
Title: Braking of high-speed flows in the near-Earth tail
Authors: Shiokawa, K.; Baumjohann, W.; Haerendel, G.
Bibcode: 1997GeoRL..24.1179S
Altcode:
We have studied possible braking mechanisms of high-speed ion flows in
the near-Earth central plasma sheet for radial distances between 9 and
19 Earth Radii (RE) on the basis of observations made by
the AMPTE/IRM satellite. Flows with velocities in excess of 400 km/s
are almost always Earthward for this range, indicating that the source
of the flows is beyond 19 RE. Though the occurrence rate
of the high-speed flows substantially decreases when the satellite
comes closer to the Earth, high-speed flows with velocities higher
than 600 km/s are still observed. We suggest that the high-speed flows
are stopped at a clear boundary between the regions of dipolar field
and tail-like field in the plasma sheet. The boundary corresponds to
the inner edge of the neutral sheet. The average jump of the magnetic
field at the boundary, which is estimated from the observations by
assuming a pressure balance, is 6.7 nT. The inertia current caused
by the braking of the flow and the current caused by pileup of the
magnetic flux at the stopping point are quantitatively estimated and
discussed in relation to the formation of the substorm current wedge.
Title: Dynamics of Structures in the Plasma Tail of Comet Hale-Bopp
Authors: Fischer, Ch. Th.; Haerendel, G.; Bogdanov, A. T.
Bibcode: 1997EM&P...77..279F
Altcode: 1999EM&P...77..279F
No abstract at ADS
Title: Sedimentation of barium ions from the CRRES G-9 release
Authors: Frey, H. U.; Haerendel, G.; Valenzuela, A.
Bibcode: 1997GeoRL..24..763F
Altcode:
The CRRES G-9 barium release was designed for the investigation of
the field line tracing between the release point at 17.4°N latitude
and the area of ion cloud sedimentation at about -41°S latitude. Very
recently published images of the ion cloud after the release showed the
development of at least two weak filaments between the release point
and the main ion cloud [Zaitsev et al., 1996]. Observations made from
an aircraft in the south Atlantic region verify that at least one of
these filaments survived the transequatorial transit and was still
separated from the main barium cloud during sedimentation.
Title: MPE Jahresbericht / Annual report 1996.
Authors: Haerendel, G.
Bibcode: 1997mpja.book.....H
Altcode:
No abstract at ADS
Title: Rosetta Lander - In Situ Investigation of a Comet's Nucleus
Authors: Ulamec, S.; Feuerbacher, B.; Wittmann, K.; Rosenbauer, H.;
Bibring, J. P.; Moura, D.; Mugnuolo, R.; Haerendel, G.
Bibcode: 1997LPI....28.1461U
Altcode:
No abstract at ADS
Title: Max-Planck-Institut für Extraterrestrische
Physik. Jahresbericht für 1996.
Authors: Haerendel, G.
Bibcode: 1997MitAG..80..227H
Altcode:
No abstract at ADS
Title: The COSPAR colloquium on space remote sensing of subtropical
ocean. 12-16 September 1995 Taipei, Taiwan
Authors: Haerendel, Gerhard
Bibcode: 1997srss.conf....7H
Altcode:
This chapter presents the speech of Professor Gerhard Haerendel,
president of the Committee on Space Research (COSPAR), on the opening
ceremony of the second colloquium on Space Remote Sensing of Subtropical
Oceans held in Taiwan. The chapter discusses the role of COSPAR in
promoting space research and related applications worldwide with an
emphasis on the exchange of results, information, and opinions. This
insistence on tangible results and on scientific data collected in
space or about space constitutes the core of COSPAR's activity and
has allowed it to steer the clearance of many political reef in
past decades. COSPAR's expertise in international cooperation can
be of benefit to countries involved in programs of space research
and related applications. One of these expertise is its ability of
monitoring and keeping surveillance of the global human environment,
including the surface of land areas and of oceans. In addition, space
observations are of great help in monitoring the geographic extent of
disasters-natural or induced by man-and in controlling the efficiency of
steps undertaken to mitigate the nefarious effects of such calamities.
Title: The Electron Drift Instrument for Cluster
Authors: Paschmann, G.; Melzner, F.; Frenzel, R.; Vaith, H.; Parigger,
P.; Pagel, U.; Bauer, O. H.; Haerendel, G.; Baumjohann, W.; Scopke,
N.; Torbert, R. B.; Briggs, B.; Chan, J.; Lynch, K.; Morey, K.; Quinn,
J. M.; Simpson, D.; Young, C.; McIlwain, C. E.; Fillius, W.; Kerr,
S. S.; Mahieu, R.; Whipple, E. C.
Bibcode: 1997SSRv...79..233P
Altcode:
No abstract at ADS
Title: Presidential address
Authors: Haerendel, G.
Bibcode: 1997AdSpR..20.1325H
Altcode:
No abstract at ADS
Title: Auroral-arc splitting by intrusion of a new convection channel
Authors: Frey, H. U.; Haerendel, G.; Buchert, S.; Lanchester, B. S.
Bibcode: 1996AnGeo..14.1257F
Altcode: 1997AnGeo..14.1257F; 1996AnG....14.1257F
During a run of the Common Programme Three of the EISCAT radar the
splitting of an auroral arc was observed by high time-resolution,
ground-based cameras when the UHF radar beam was close to the
arc. The evening eastward electrojet situation with a large-scale
northward ionospheric electric field was disturbed by the intrusion
of a convection channel with southward electric field from the
east. The interaction of the new convection channel with the auroral
arc caused changes in arc brightness and arc splitting, i.e. the
creation of a new arc parallel to the pre-existing auroral arc. The
event is described as one possibility for the creation of parallel
arcs during slightly disturbed magnetic conditions far from the
Harang discontinuity. Acknowledgements. We would like to thank the
director and staff of EISCAT for the data used in this study. EISCAT
is supported by the scientific research councils of Finland, France,
Germany, Norway, Sweden and the UK. We would like to express our special
thanks to A. P. van Eyken and U. P. Løvhaug for their cooperation and
assistance in running the IPS campaigns and to W. P. Wilkinson for
discussions on fast-stream/slow-stream interaction regions. Two of
us (ARB and PJM) are supported by PPARC. Topical Editor D. Alcaydé
thanks J. F. Mckenzie and M. Pick for their help in evaluating this
paper.--> Correspondence to: A. R. Breen-->
Title: Observing with the ISO Short-Wavelength Spectrometer.
Authors: de Graauw, T.; Haser, L. N.; Beintema, D. A.; Roelfsema,
P. R.; van Agthoven, H.; Barl, L.; Bauer, O. H.; Bekenkamp, H. E. G.;
Boonstra, A. -J.; Boxhoorn, D. R.; Cote, J.; de Groene, P.; van
Dijkhuizen, C.; Drapatz, S.; Evers, J.; Feuchtgruber, H.; Frericks,
M.; Genzel, R.; Haerendel, G.; Heras, A. M.; van der Hucht, K. A.;
van der Hulst, T.; Huygen, R.; Jacobs, H.; Jakob, G.; Kamperman, T.;
Katterloher, R. O.; Kester, D. J. M.; Kunze, D.; Kussendrager, D.;
Lahuis, F.; Lamers, H. J. G. L. M.; Leech, K.; van der Lei, S.; van
der Linden, R.; Luinge, W.; Lutz, D.; Melzner, F.; Morris, P. W.; van
Nguyen, D.; Ploeger, G.; Price, S.; Salama, A.; Schaeidt, S. G.; Sijm,
N.; Smoorenburg, C.; Spakman, J.; Spoon, H.; Steinmayer, M.; Stoecker,
J.; Valentijn, E. A.; Vandenbussche, B.; Visser, H.; Waelkens, C.;
Waters, L. B. F. M.; Wensink, J.; Wesselius, P. R.; Wiezorrek, E.;
Wieprecht, E.; Wijnbergen, J. J.; Wildeman, K. J.; Young, E.
Bibcode: 1996A&A...315L..49D
Altcode:
The Short-Wavelength Spectrometer (SWS) is one of the four instruments
on-board ESA's Infrared Space Observatory (ISO), launched on November
17, 1995. The spectrometer covers the wavelength range of 2.38 to
45.2μm with a spectral resolution ranging from 1000 to 2000. By
inserting Fabry-Perot filters the resolution can be enhanced by a
factor 20 for the wavelength range from 11.4 to 44.5μm. An overview
is given of the instrument, its in-orbit calibration, performance,
observing modes and off-line processing software.
Title: Microsatellites and space station for science and technology
utilisation
Authors: Spallicci, A.; Graf, E.; Perino, M.; Matteoni, M.; Piras,
A.; Arduini, C.; Catastini, G.; Ellmers, F.; Hall, D.; Haerendel,
G.; Nobili, A.; Iess, L.; Pinto, I.; Stocker, J.
Bibcode: 1996AcAau..39..605S
Altcode:
The main results of an ESTEC study on microsatellites and the
International Space Station (ISS) are shown herein. One of the original
objectives of the space station has been to be a staging post for
assembly, check-out and deployment of satellites and deep-space
missions. ISS will not be equipped to process and launch large
spacecraft requiring complex assembly and propellant operations, but
deployment of a microsatellite might still be feasible and advantageous,
as other international partners show similar interests. The assembly,
launch and retrieval of small satellites with ISS (e.g. up to 225 kg,
100 W of power from body mounted solar cells or 225 W from solar panels,
size less than 1.6 × 0.8 × 1 m, 250 b s -1 to 2 kb s
-1 of up and down link data) is a future but a technically
viable option to raise the attractiveness of ISS for those payloads
whose requirements would not be satisfied by internal or external
accommodation on ISS. Two classes of payloads were identified: (1)
Space Station investigation (SSI) type; (2) Space Station exploitation
(SSE) type. SSI payloads conduct investigations of direct interest to
ISS as electromagnetic, radiation and particle near-environment (ISS
sniffers). Instead, SSE investigations are totally unrelated to ISS and
they make solely advantage of its infrastructure and facilities. For
the latter it will be necessary to compare the same experiment with
and without ISS in the mission scenario, as a proof of effectiveness
(in costs and/or scientific return) with respect to satellites launched
by traditional means. Such effectiveness may be represented by (i)
simplicity of design, e.g. the proximity of ISS eases the TT&C
subsystem, (ii) servicing and re-utilisation for successive experiments,
(iii) readiness to launch when a specific and unpredictable event
occurs (e.g. supernovae). Different scenarios and implementations have
been studied for launch and operations. Safe orbital trajectories
have been identified also without a propulsion system. In case of a
on-board propulsion system, about 50 kg for cold gas fuel and another
50 kg for dry propulsion system, were found necessary for a mission
lifetime in ISS neighbourhood (within 50 km) up to about 6 months. The
study has conceived 13 proposals in disciplines ranging from metrology
and general physics, to space science and technology, as examples of
potential applications but in no manner constituting an exhaustive
picture of user interests. An SSI experiment for the analysis of ISS
environment was selected as potential first mission.
Title: Auroral emission profiles extracted from three-dimensionally
reconstructed arcs
Authors: Frey, S.; Frey, H. U.; Carr, D. J.; Bauer, O. H.; Haerendel,
G.
Bibcode: 1996JGR...10121731F
Altcode:
The mathematics of emission-computed tomography is applied to the
analysis of stereoscopic observations of auroral arcs. The incomplete
data problem for three-dimensional computerized tomography, due to
the very limited angular range and the small number of observers, is
solved by an iterative least squares method. A theoretical example
with the projection of two auroral arcs can be reconstructed with
projection root-mean-square errors of the order of 1%. Application
of noise deteriorates the quality of reconstruction, but with
suitable low-pass filtering, root-mean-square errors of less than
5% can be obtained. The agreement between observed and calculated
projections, as well as between the original and the reconstructed
volume emission distribution, is quantitatively discussed for different
observation geometries. With only two observation sites the range of
acceptable observation geometries is limited to distances of 25 to
50 km between the observers but depends on the actual location and
the morphology of the aurora. Sources of distortion of real auroral
observations with intensified CCD cameras are discussed and correction
procedures proposed. The complete procedure is applied to a real
stereoscopic auroral observation. The correspondence of original
pictures and projections of the reconstructed volume is discussed,
and emission profiles along magnetic field lines are extracted from
the three-dimensionally reconstructed arc.
Title: Momentum coupling in the ``CRIT II'' critical ionization
velocity experiment
Authors: Liou, K.; Torbert, R. B.; Haerendel, G.
Bibcode: 1996JGR...10119649L
Altcode:
A unified theory has been developed to explain the formation of a
quasi-dc electric pulse (ω<=Ωi) induced by an ionizing
neutral barium beam across an ionospheric plasma. We obtained a
generalized form for the dc electric field in the plane perpendicular
to the magnetic field within a simplified slab barium cloud moving
perpendicular to the geomagnetic fields. A current system associated
with the quasi-dc electric field was also proposed to provide a way to
transfer the momentum between the streaming barium cloud and the ambient
plasma. The characteristic time derived by using this model for momentum
coupling between the streaming barium cloud and the ambient plasma
is found to be in agreement with the previous result. The quasi-dc
electric field predicted by this model is reasonably consistent with
the ``CRIT II'' critical ionization velocity measurements. On the
basis of the constrains of the conservation of energy and momentum,
we found that Alfvén's critical ionization velocity (CIV) effect is a
self-limiting ionization process in a finite extent neutral cloud. It
may be the reason why the CIV effect took place in CRIT II but lasted
only for a very short period, and it may have resulted in low ionization
yields in most of space CIV experiments.
Title: Curiosity and chance
Authors: Haerendel, Gerhard
Bibcode: 1996JGR...10110541H
Altcode:
The author recounts some stations of his professional life, which
was to a large extent dedicated to active experimentation with plasma
clouds in space and to the development of theoretical concepts for some
intriguing plasmaphsical processes. The human and political environment
of this work receives some coverage as well as his opinion of state
and future of his discipline.
Title: MPE Jahresbericht / Annual report 1995.
Authors: Genzel, R.; Haerendel, G.
Bibcode: 1996mpja.book.....G
Altcode:
No abstract at ADS
Title: Optical and radar observations of auroral arcs with emphasis
on small-scale structures.
Authors: Haerendel, G.; Olipitz, B. U.; Buchert, S.; Bauer, O. H.;
Rieger, E.; La Hoz, C.
Bibcode: 1996JATP...58...71H
Altcode:
During a campaign in January 1988 the authors observed auroral arcs
with the EISCAT UHF radar system and a low light level TV camera. The
aim was to compare apparent motions of the arc and its small-scale
structures with plasma motions in the adjacent F-region.
Title: A balloon-borne experiment to investigate the Martian
magnetic field
Authors: Schwingenschuh, K.; Feldhofer, H.; Koren, W.; Jernej, I.;
Stachel, M.; Riedler, W.; Slamanig, H.; Auster, H. -U.; Rustenbach,
J.; Fornacon, H. K.; Schenk, H. J.; Hillenmaier, O.; Haerendel, G.;
Yeroshenko, Ye.; Styashkin, V.; Zaroutzky, A.; Best, A.; Scholz, G.;
Russell, C. T.; Means, J.; Pierce, D.; Luhmann, J. G.
Bibcode: 1996AdSpR..17i..81S
Altcode: 1996AdSpR..17...81S
The Space Research Institute of the Austrian Academy, of Sciences
(Graz, Austria) in cooperation with MPE (Berlin, Germany), GFZ Potsdam
(Obs. Niemegk, Germany) IZMIRAN/IOFAN (Moscow, Russian) and IGPP/UCLA
(Los Angeles, USA) is designing the magnetic field experiment
MAGIBAL (MAGnetic field experiment aboard a martian BALloon) to
investigate the magnetic field on the surface of Mars. The dual sensor
fluxgate magnetometer is part of the MARS-98/MARS-TOGETHER balloon
payload. During a ten days period the balloon will float over a distance
of about 2000 km at altitudes between 0 and 4 km. Due to the limited
power and telemetry allocation the magnetometer can transmit only one
vector per ten seconds and spectral information in the frequency range
from 2 - 25 Hz. The dynamic range is +/- 2000 nT. The main scientific
objectives of the experiment are: • Determination of the magnetism
of the Martian rocks • Investigation of the leakage of the solar
wind induced magnetosphere using the correlation between orbiter and
balloon observations • Measurement of the magnetic field profile
between the orbiter and the surface of Mars during the descent phase
of the balloon. Terrestrial test flights with a hot air balloon were
performed in order to test the original MAGIBAL equipment under balloon
flight conditions.
Title: Optical and radar observations of the motion of auroral arcs.
Authors: Frey, H. U.; Haerendel, G.; Knudsen, D.; Buchert, S.; Bauer,
O. H.
Bibcode: 1996JATP...58...57F
Altcode:
During a nine-day observational campaign in February 1992 the authors
used an image-intensified CCD TV camera along with the EISCAT radar to
observe auroral arcs in the magnetic zenith above Kiruna. The authors
determine the normal motions of auroral arcs near magnetic zenith and
compare them with the plasma velocities measured by EISCAT. The interest
focuses on the relative motions of arcs and ionospheric plasma and the
changes of tangential velocity as the plasma traverses the arcs. In
all six cases, relative motions of arc and plasma of the order of 200
m s-1 are found. They are interpreted in relation to the
current system to which the arc belongs as a trace of an upward-directed
field-aligned sheet current. In most cases the arc moves so as to reduce
the size and energy content of the current system, but the opposite
case is also observed. There is a striking correlation between the
N-S motion of arcs and plasma, but the arcs tend to lag behind.
Title: Studies of auroral arcs using Freja satellite and ground-based
data
Authors: Frey, H. U.; Haerendel, G.; Clemmons, J.; Wallis, D. D.;
Vogt, J.; Bauer, O. H.; Rieger, E.; Boehm, M. H.; Lühr, H.
Bibcode: 1996AdSpR..18h.107F
Altcode: 1996AdSpR..18..107F
During two Freja passes over auroral arc systems special wide-angle
CCD cameras were operated from the ground. Comparisons of the
optical observations with satellite-measured plasma parameters are
performed. Motions of fine structures of the arcs are interpreted
in terms of high-altitude electric fields shielded from the lower
ionosphere. Independent measurements of current density, accelerating
voltage and energy flux are evaluated and show good agreement.
Title: ESA and the Central Issues of Space Plasma Physics
Authors: Haerendel, Gerhard
Bibcode: 1995ESASP.387...65H
Altcode: 1995tyec.conf...65H
No abstract at ADS
Title: Observation of electromagnetic oxygen cyclotron waves in a
flickering aurora
Authors: Lund, E. J.; LaBelle, J.; Torbert, R. B.; Liou, K.; Peria,
W.; Kletzing, C. A.; Kelley, M. C.; Baker, S. D.; Primdahl, F.;
Stenbaek-Nielsen, H. C.; Ranta, A.; Haerendel, G.; Frey, H. U.
Bibcode: 1995GeoRL..22.2465L
Altcode:
Instruments on the Auroral Turbulence rocket detected several intervals
of weak electromagnetic oscillations at frequencies of 6-13 Hz in a
strongly flickering auroral arc. These oscillations have amplitudes of
up to δB ∼ 3 nT and δE ∼ 4 mV/m and have downward field-aligned
Poynting fluxes of up to ∼10-5 W/m². Fluctuations in the
parallel electron flux at about 9 Hz were observed in association with
the strongest of these oscillations. Simultaneous ground-based optical
data show that the arc was flickering at frequencies of 8-15 Hz. The
observed frequencies would match the oxygen cyclotron frequency at
∼4500 km altitude. In one wave/particle event the apparent lag of
the waves behind the modulated electrons implies a modulation source
altitude of 2500-5000 km. We interpret these waves as electromagnetic
ion cyclotron waves originating in the auroral acceleration region.
Title: Technical Challenge, Scientific Thrill: A Long Term Lander
on an Active Comet
Authors: Ulamec, S.; Feuerbacher, B.; Wittmann, K.; Rosenbauer, H.;
Haerendel, G.; Lura, F.
Bibcode: 1995LPI....26.1431U
Altcode:
No abstract at ADS
Title: Message from the President of COSPAR
Authors: Haerendel, Gerhard
Bibcode: 1995CIBu..133....1H
Altcode:
No abstract at ADS
Title: Micro and Meso Scale Measurements by the Freja Satellite
Authors: Lundin, R.; Haerendel, G.
Bibcode: 1995GMS....86..295L
Altcode: 1995spcb.book..295L
Freja, a joint Swedish and German scientific satellite launched on
October 6 1992, is designed to give high temporal/spatial resolution
measurements of the auroral plasma characteristics. A high telemetry
rate (520 kbits/s) and ≈15 Mbyte distributed on board memories
(give ≈2 Mbits/s during one minute) enables Freja to resolve meso
and micro scale phenomena in the 100 m range for particles and 1-10
m range for electric and magnetic fields. The on-board UV imager will
resolve auroral structures of kilometer size with a time resolution of
one image per 6 s. Novel plasma instruments give Freja the capability
to increase the spatial/temporal resolution orders of magnitudes above
that achieved on satellites before. The scientific objectives
of Freja is to study the interaction between the hot magnetospheric
plasma with the topside atmosphere/ionosphere. This interaction leads
to a strong energization of magnetospheric and ionospheric plasma
and an associated erosion, and loss, of matter from the terrestrial
exosphere. Freja orbits with an altitude of ≈600 -1750 km, thus
covering the lower part of the auroral acceleration region. This
altitude range hosts processes that heat and energize the ionospheric
plasma above the auroral zone, leading to the escape of ionospheric
plasma and the formation of large density cavities.
Title: Magnetic energy conversion in the Corona and Magnetosphere
Authors: Haerendel, G.
Bibcode: 1995HiA....10..302H
Altcode:
No abstract at ADS
Title: The Electron Beam Instrument (F6) on Freja
Authors: Paschmann, G.; Boehm, M.; Höfner, H.; Frenzel, R.; Parigger,
P.; Melzner, F.; Haerendel, G.; Kletzing, C. A.; Torbert, R. B.;
Sartori, G.
Bibcode: 1994SSRv...70..447P
Altcode:
The Electron Beam Instrument (F6) onFreja is the first attempt to apply
the electron drift technique in a region of large ambient magnetic
fields. The paper describes the operational principles, the technical
realization, and the difficulties encountered in the derivation of
the electric fields.
Title: The double probe electric field experiment on Freja: Experiment
description and first results
Authors: Marklund, G. T.; Blomberg, L. G.; Lindqvist, P. -A.;
Fälthammar, C. -G.; Haerendel, G.; Mozer, F. S.; Pedersen, A.;
Tanskanen, P.
Bibcode: 1994SSRv...70..483M
Altcode:
A description is given of theFreja double-probe electric field
instrument. Its capability to perform high-resolution measurements
of the aurora and its fine-structure as well as collect information
on sub-auroral and low-latitude phenomena is illustrated by selected
results from the first six months of operation. The instrument is highly
flexible and possible to operate in a number of different modes. It is
also equipped with a 4-Megabyte burst memory for high data sampling
rate and temporary storage of data. It has been fully operational
since October 1992, and delivers data from ≈22 hr day-1
including about 5 6 auroral crossings of the northern and southern
auroral ionosphere. New and important information on the auroral fine
structure and electrodynamics is obtained by means of burst resolution
data (6144 samples s-1) and normal resolution data (768
samples s-1). Common burst data collection triggered by the
electric field event detector has turned out to be very useful for the
selection of scientifically interesting events. This is illustrated by
high-resolution data of a pair of extremely intense and narrow electric
field structures (1 V m-1) which are associated with a total
absence of precipitating particles, depletions of the thermal plasma
and with an intense wave activity. The low inclination of theFreja
orbit provides a new perspective for studying largescale phenomena
associated with east-west gradients as is exemplified by electric
field data from a satellite crossing over north-south oriented auroral
structures presumably resulting from rotational distortions of east-west
aligned auroral arcs. The different plasma regimes encountered byFreja
are continuously monitored by means of current sweeps applied to the
probes and by the satellite potential. In addition, overview data (8
samples s-1) are collected from full orbits and stored in
the on-board memory and have proved to be extremely valuable, providing
new information on global electric field phenomena at subauroral and
lower latitudes, such as the intense poleward electric fields and
Pc-1 observations that have been made near the plasmapause during
substorm activity.
Title: The Freja science mission
Authors: Lundin, R.; Haerendel, G.; Grahn, S.
Bibcode: 1994SSRv...70..405L
Altcode:
Freja *, a joint Swedish and German scientific satellite
launched on october 6 1992, is designed to give high temporal/spatial
resolution measurements of auroral plasma characteristics. A
high telemetry rate (520 kbits s-1) and ≈15 Mbyte
distributed on board memories that give on the average 2 Mbits
s-1 for one minute enablesFreja to resolve meso and micro
scale phenomena in the 100 m range for particles and 1 10 m range for
electric and magnetic fields. The on-board UV imager resolve auroral
structures of kilometer size with a time resolution of one image per 6
s. Novel plasma instruments giveFreja the capability to increase the
spatial/temporal resolution orders of magnitudes above that achieved
on satellites before. The scientific objective ofFreja is to study
the interaction between the hot magnetospheric plasma with the topside
atmosphere/ionosphere. This interaction leads to a strong energization
of magnetospheric and ionospheric plasma and an associated erosion,
and loss, of matter from the Terrestrial exosphere.Freja orbits
with an altitude of ≈600 1750 km, thus covering the lower part of
the auroral acceleration region. This altitude range hosts processes
that heat and energize the ionospheric plasma above the auroral zone,
leading to the escape of ionospheric plasma and the formation of large
density cavities.
Title: The TESP electron spectrometer and correlator (F7) on Freja
Authors: Boehm, M.; Paschmann, G.; Clemmons, J.; Höfner, H.; Frenzel,
R.; Ertl, M.; Haerendel, G.; Hill, P.; Lauche, H.; Eliasson, L.;
Lundin, R.
Bibcode: 1994SSRv...70..509B
Altcode:
The two-dimensional electron spectrometer onFreja consists of
a ‘top-hat’-type electrostatic analyzer with the addition
of entrance aperture deflection plates. The field of view of the
concentric-hemisphere analyzer is modified from a plane to a cone up
to 25° from this plane by application of bipolar high voltages to the
deflection plates. Fast high-voltage sweeps allow full 10 eV 25 KeV,
500-point distribution function measurements in 32 ms. Constant-energy
or limited energy-sweep modes allow time resolutions down to 1 ms. A
set of electronics combines the electron data with F4 wave data to
allow on-board calculations of cross-correlations between electron
fluxes and wave electric fields. Additionally, a fast signal processor
is capable of searching the electron pulse sequence from one or several
channeltrons for high-frequency modulations in the electron flux.
Title: Inverted-V events simultaneously observed with the Freja
satellite and from the ground
Authors: Haerendel, G.; Frey, H. U.; Bauer, O. H.; Rieger, E.;
Clemmons, J.; Boehm, M. H.; Wallis, D. D.; Lühr, H.
Bibcode: 1994GeoRL..21.1891H
Altcode:
The paper reports data received from the Freja satellite during two
passes over broad auroral arc systems or inverted-V events above
Gillam/Manitoba when special wide-angle CCD cameras were operated at
this location in addition to the CANOPUS network. Detailed comparisons
of the visible structures with modulations of the primary electron
fluxes are performed. Motions of this fine structures are interpreted
in terms of high-altitude electric fields shielded from the lower
ionosphere. Simultaneous readings of current density, accelerating
voltage and energy flux, the latter determined both from particle
and auroral brightness measurements, are found to be internally
consistent. We calculate from these data the effective resistance
encountered by the electric currents and find agreement with the kinetic
theory of the mirror impedance, if we allow for substantial variations
in density and energy of the source electrons in the magnetosphere.
Title: Signatures of energy-time dispersed electron fluxes measured
by Freja
Authors: Clemmons, J. H.; Boehm, M. H.; Paschmann, G. E.; Haerendel, G.
Bibcode: 1994GeoRL..21.1899C
Altcode:
Two measurements of velocity-dispersed electron fluxes at altitudes near
1750 km are reported. The energy-time signatures of both observations
are interpreted in terms of a simple time-of-flight (TOF) scenario. The
first measurement occurred at low magnetic latitude (∼62°)
and consisted of three injection events. Analysis yields a source
location near the equator ∼6.5 RE from the spacecraft and
provides evidence that the injections were periodic. The injections
are interpreted as being the result of interactions with waves near
the earthward edge of the equatorial plasma sheet, and the presence
of fine structure in the fluxes with timescales of a few hundred ms
provides new information on the injection process. Analysis of the
second measurement leads to the determination of a source location
about 850 km above the spacecraft. Although the simple model is able
to explain the observations at small pitch angles, the measurements at
large pitch angles require that the model be refined, and a modification
which invokes pitch-angle diffusion is suggested.
Title: The Freja Project
Authors: Lundin, R.; Haerendel, G.; Grahn, S.
Bibcode: 1994GeoRL..21.1823L
Altcode:
Freja is a joint Swedish and German scientific satellite project
to study the interaction between hot magnetospheric plasma and the
topside atmosphere/ionosphere. This interaction leads to a strong
energization of magnetospheric and ionospheric plasma and an associated
erosion and loss of matter from the terrestrial atmosphere. Using
novel plasma instruments and a high data rate Freja have provided
a number of “firsts” in high resolution plasma diagnostics from
satellites. Freja's high spatial/temporal resolution permits studies
of meso- and micro-scale phenomena in the 100-m range for particles
and in the 10-m range for electric and magnetic fields. The Freja
satellite was successfully launched on October 6, 1992 into an orbit
with 63° inclination, an apogee of 1750 km and perigee of 600 km.
Title: Freja observations of narrow inverted-V electron precipitation
by the Two-Dimensional Electron Spectrometer
Authors: Boehm, M. H.; Paschmann, G.; Clemmons, J.; Haerendel, G.;
Eliasson, L.; Lundin, R.
Bibcode: 1994GeoRL..21.1895B
Altcode:
Observations of several steady, ∼1-5 km scale inverted-V's by
the Freja F7 Two-dimensional Electron Spectrometer (TESP) are
described. Such narrow structures are not common, but provide an
opportunity for observing edge precipitation and the movement of arcs
through the plasma. Velocities of inverted-V potential structures in
the plasma frame can be derived from the observed time delay between
precipitating and mirrored electrons. These velocities determine
whether horizontal plasma flow into a potential structure can provide
the source population for arc edge precipitation. It is found that
the intensity of the arc edge precipitation is not associated in any
expected way with this velocity, indicating another source of plasma
for arc edge precipitation is required.
Title: Large-scale auroral plasma density cavities observed by Freja
Authors: Lundin, R.; Eliasson, L.; Haerendel, G.; Boehm, M.;
Holback, B.
Bibcode: 1994GeoRL..21.1903L
Altcode:
Freja, the joint Swedish and German scientific satellite, has an orbit
inclination that allows it to traverse the auroral oval tangentially and
stay for minutes on field lines connected to the auroral energization
region. One signature of the auroral energization process is the
heating/transverse energization of ionospheric ions. Associated
with such transverse heating/energization of ionospheric ions is a
depletion of cold plasma in the topside ionosphere. We have studied
several Freja passes at ≈1700 km altitude with long time periods of
plasma depletion and transverse ion acceleration. Inside these depletion
regions the density may decrease by more than two orders of magnitude
(from 1000 to ≈10 cm-3). This suggests that transverse ion
heating is indeed a very strong mechanism for plasma density depletion
in the topside ionosphere.
Title: Electric fields derived from electron drift measurements
Authors: Kletzing, C. A.; Paschmann, G.; Boehm, M. H.; Haerendel, G.;
Sckopke, N.; Baumjohann, W.; Torbert, R. B.; Marklund, G.; Lindqvist,
P. -A.
Bibcode: 1994GeoRL..21.1863K
Altcode:
The first observations of electric fields derived from electron E ×
B drift measurements aboard the Freja spacecraft are presented. The
instrument injects a weak beam of 3 keV electrons and measures the
displacement of the returning electrons after one gyroperiod. After
removing effects due to beam-detector geometry and applying an empirical
calibration based upon comparison with the computed υ × B electric
field induced by the spacecraft motion, good agreement is found
when the electron drift measurements are compared with the electric
field components measured by the double probe experiment. Examples
are presented in which moderately large electric fields are observed
near the edges of or adjacent to electron precipitation regions with
little or no electric field within.
Title: Acceleration from Field-Aligned Potential Drops
Authors: Haerendel, Gerhard
Bibcode: 1994ApJS...90..765H
Altcode: 1994IAUCo.142..765H
Unstable field-aligned currents are seen as the origin of field-aligned
potential drops. They convert energy stored in magnetic shear stresses
into kinetic energy. A good fraction of this energy is carried by
runaway electrons and ions out of the acceleration region. The paper
emphasizes the analogy with mechanical fractures. Simple expressions
for the energy conversion rate and the parallel potential drop are
derived, the two being linked by the critical current density needed
for instability. The origin of the currents (generator) lies mostly in
a region remote from that of energy conversion (fracture zone). The
transmission of shear stresses and energy from the generator plasma,
where the primary forces are applied to the fracture zone is also
considered. A closed set of relations allows quantitative evaluation of
the energetic particle production efficiency . The decoupling of the
plasma on either side of the fracture zone which allows fast stress
relief is described in detail, as well as a stationary model of the
Alfven wave interaction between fracture zone and generator plasma. A
simple concept of the nature of the anomalous resistivity generated by
the unstable current leads to an expression for the magnetic diffusivity
inside the fracture zone and an estimate of the latter's extent parallel
to the magnetic field, whereas its width and length transverse to B
follow from the macroscopic relations. Finally and as an example,
the theory is applied to the problem of fast electron (and ion)
acceleration well above 1 MeV seen to occur in many solar flares. It
is obvious that this process belongs to the most powerful production
processes of high-energy particles in stellar magnetic fields.
Title: Numerical Simulation of Chromospheric Spicules Driven by
Weakly-Damped Alfven Waves
Authors: de Pontieu, B.; Haerendel, G.
Bibcode: 1994scs..conf..323D
Altcode: 1994IAUCo.144..323D
The authors perform a time-dependent numerical simulation of the
momentum transfer from weakly-damped Alfvén waves to the solar
chromospheric plasma in a spatially expanding flux tube. The momentum
transfer is due to the effect of ion-neutral collisions of Alfvén
waves. By solving one-dimensional and time-dependent hydrodynamic
equations, the authors study the formation of spicules.
Title: First high-resolution measurements by the Freja satellite.
Authors: Lundin, R.; Eliasson, L.; Norberg, O.; Marklund, G.; Zanetti,
L. R.; Whalen, L. A.; Holback, B.; Murphree, J. S.; Haerendel, G.;
Boehm, M.; Paschmann, G.
Bibcode: 1994GMS....84..247L
Altcode:
The joint Swedish-German Freja satellite was successfully launched on
October 6, 1992. Freja contains an extensive set of plasma and field
instruments for high time-resolution measurements of the auroral plasma
in the altitude range 600 - 1750 km. The satellite also contains two UV
imagers to monitor the auroral activity at the geomagnetic footprint of
the satellite. In this paper the authors review the first few months of
operation and the first scientific data from the Freja experiments. Of
particular interest are the density cavities observed within the auroral
energization region and the rather unique perspective obtained from
the Freja orbit.
Title: Incoherent scatter radar spectrum distortions from intense
auroral turbulence
Authors: Knudsen, D. J.; Haerendel, G.; Buchert, S.; Kelley, M. C.;
Steen, A.; Brandstrom, U.
Bibcode: 1993JGR....98.9459K
Altcode:
We present EISCAT (European Incoherent Scatter Radar Facility)
measurements of >2000 K enhancements of the apparent ion temperature
which occurred simultaneously over a latitude range of at least 100
km for brief periods (less than 1 min) in the auroral F region. One
event occurred during a substorm onset and a second during passage of a
westward-traveling surge. The apparent Ti increases showed
significant anisotropy, with measurements oriented less parallel to
B0 exhibiting the largest amount of apparent Ti
increase. In these examples the vector electric fields measured by
EISCAT were much too low to account for the temperature increases
via frictional heating, and also too low to generate non-Maxwellian
ion velocity distributions, which can cause errors in ion temperature
estimates. We argue that the measured Ti increases are not
real, and that both their magnitude and their anisotropy with respect
to B0 can be satisfactorily explained by turbulent plasma
flows with peak amplitudes of ~2 km/s but which could not be directly
resolved by EISCAT, because they varied with a time scale less than
the 10-s integration period, or possibly because their scale size was
smaller than the ~3-5 km antenna beam width. While such unresolved but
inferred turbulent flows can themselves cause ion frictional heating,
we show that an equally important cause of high Ti estimates
in our case was the distortion of the measured spectra by strongly
varying Doppler shifts. We also present a counter example which shows
a bright auroral arc in the radar common volume but with no large
increases in the radar-measured Ti, indicating that not all
auroral structures are associated with electric fields which vary with
sufficient intensity to distort incoherent scatter radar spectra.
Title: On the proper motion of auroral arcs
Authors: Haerendel, G.; Buchert, S.; La Hoz, C.; Raaf, B.; Rieger, E.
Bibcode: 1993JGR....98.6087H
Altcode:
The ability of the tristatic UHF radar of EISCAT to measure plasma
velocities in the F region has been employed for the assessment of such
motions in the proximity of and relative to auroral arcs. This required
real-time tracking of the arcs with the radar upon command from the
ground station monitoring the aurora. Slow relative motions of arc and
plasma of the order of 30-90 m s-1 were deduced
from the observations, but the error sources are considerable. Three
cases are presented, representing different situations. The arc may
move into an auroral current system or out of it. The first case
corresponds to an energy reduction, the second to a build-up of the
energy content of the current system. Oscillatory motions, alternating
between these situations, exist. The oscillations lie in the Pc 5 range
and testify for an interaction of the energy release region (auroral
acceleration region) and the generator via shear Alfvén waves. The
events are interpreted in the light of the ``fracture model'' of auroral
arcs developed by the first author. Although relative motions of the
observed magnitude are predicted by this theory, other explanations
are conceivable.
Title: The Electron Drift Instrument for Cluster
Authors: Paschmann, G.; Melzner, F.; Haerendel, G.; Bauer, O. H.;
Baumjohann, W.; Sckopke, N.; Treumann, R.; McIlwain, C. E.; Fillius,
W.; Whipple, E. C.; Torbert, R. B.; Quinn, J. M.
Bibcode: 1993ESASP1159..115P
Altcode: 1993cmps.book..115P
No abstract at ADS
Title: Detection of optical emission in the area of G127.1+0.5.
Authors: Xilouris, K. M.; Papamastorakis, J.; Paleologou, E. V.;
Andredakis, Y.; Haerendel, G.
Bibcode: 1993A&A...270..393X
Altcode:
Diffuse optical emission has been detected around the area of the
galactic SNR G127.1+0.5 for the first time. Deep H-alpha CCD images have
been used to identify the nebulosity that correlates with both the IR
emission evident on the IRAS maps and the radio contours of the galactic
remnant G127.1+0.5. The optical filaments of the known nearby remnant G
126.2+1.6 have also been observed in order to evaluate the detection
ability of our instrumental set-up. The intensity of the optical
emission from the nebulosity has been determined by comparison with
the standard star BD +28 deg 4211. The detection of the diffuse optical
emission is established beyond doubt. The structure of the surrounding
area is discussed and an attempt is made to identify the origin of
the detected emission by studying this area at other wavelengths.
Title: Weakly damped Alfvén waves as drivers of solar chromospheric
spicules
Authors: Haerendel, Gerhard
Bibcode: 1992Natur.360..241H
Altcode:
THE solar chromosphere, which separates the photosphere (temperature
T ~ 6,400 K) from the hotter solar corona (T ~ 106 K),
has a very inhomogeneous structure which is strongly influenced by
the magnetic field. In the lowest 2,000 km of chromospheric altitude,
the density falls by six orders of magnitude, and the temperature
stays below 8,000 K. Above this altitude the transition to the corona
is extremely irregular. It is dominated by spicules: thin (<
1,000 km) protrusions of cool chromospheric material which extend,
with speeds of 25 km s-1 and for durations of 5-10 min,
up to 10,000 km into the corona with little change in density. Their
origin is not yet understood, and I suggest here that the force that
propels them against gravity may be the transfer of momentum from
upward-moving Alfvén waves. In the upper chromosphere the ionized
plasma component is collisionally coupled to the neutral gas, but the
coupling is not perfect, so that the neutral material can acquire a net
velocity with respect to the ionized component. This process is known
to damp the Alfvén waves12, but I show that it can also,
as the chromosphere peters out, transfer enough momentum to local
volumes to create and drive the spicules.
Title: Momentum transport through the chromosphere.
Authors: Haerendel, Gerhard
Bibcode: 1992ESASP.346...23H
Altcode: 1992ssts.rept...23H
Chromosphere and ionosphere have in common that they contain weakly
ionized plasmas. There are other similarities, but also striking
differences. A most important one lies in the ratio of neutral-ion
coupling time to the propagation time of an Alfvén wave through
the respective regions. In the ionosphere this ratio is large,
in the chromosphere very small. This has the consequence that only
a.c. Pedersen currents exist in the latter region. Their properties
are derived and their role for chromospheric heating and lifting
of cool and dense plasma out of the chromosphere into the corona,
to form spicules, is discussed.
Title: Theory for Modeling the Equatorial Evening Ionosphere and
the Origin of the Shear in the Horizontal Plasma Flow
Authors: Haerendel, G.; Eccles, J. V.; Cakir, S.
Bibcode: 1992JGR....97.1209H
Altcode:
Companion papers in this series present (1) the role of equatorial
E region postsunset ionosphere, (2) the origin of horizontal plasma
shear flow in the postsunset equatorial ionosphere (this paper), (3)
the Coloured Bubbles experiments results, and (4) computer simulations
of artificial initiation of plasma density depletions (bubbles) in the
equatorial ionosphere. Within this paper, equations describing the time
evolution of the equatorial ionosphere are developed using flux tube
integrated and flux weighted quantities which model the chemistry,
dynamics, and electrodynamics of the equatorial ionosphere. The
resulting two-dimensional set of equations can be used to investigate
equatorial electric fields neglecting small-scale phenomena (λ<1
km). An immediate result derived from the integrated current equations
is an equation describing the physics of the shear in the horizontal
flow of the equatorial plasma during the evening hours. The profile of
the horizontal flow has three important contributing terms relating to
the neutral wind dynamo, Hall conduction, and the equatorial electrojet
current divergence. Using a one-dimensional model of the velocity shear
equation and the integrated ionospheric transport equations, a time
history of the development of the shear feature during the postsunset
hours is presented. The one-dimensional model results are compared to
the velocity shear measurements from the Coloured Bubbles experiments.
Title: The Role of the Equatorial Electrojet in the Evening Ionosphere
Authors: Haerendel, G.; Eccles, J. V.
Bibcode: 1992JGR....97.1181H
Altcode:
This paper focuses on the role of the equatorial E region in
the electrodynamics of the evening ionosphere. The influence and
reaction of the electrojet current on the equatorial ionosphere at
sunset is investigated using a field line integrated, one-dimensional,
electrodynamic model. The one-dimensional, time-varying model predicts
the divergence of the horizontal current of the equatorial electrojet
for a given time variation of the horizontal electric field. The
negative divergence of the horizontal current during the evening
hours provides a net upward current out of the equatorial E region
into the integrated ionosphere of higher equatorial altitudes (and
equivalent latitudes). This upward current affects the vertical field
magnitudes and subsequent horizontal plasma drifts of the overlying
ionosphere. The model allows for chemical recombination and dynamic
redistribution of ionization within the electrojet region under the
assumption that the profile of the ionization density along a field
line is proportional to the chemical equilibrium profile. The
eastward horizontal electric field and the net upward current during
the 2 hours after sunset combine to light the ionization out of the E
region in ionization densities less than the equilibrium values. As the
ionization densities (conductivities) are reduced, the electrodynamics
of the equatorial ionosphere is altered. This model of the equatorial
electrojet current divergence can be used as a lower boundary to global,
two-dimensional models of the equatorial electric fields. Finally,
it is proposed that the equatorial electrojet current near sunset has
a significant role in the determination of the postsunset enhancement
of the horizontal electric field. The electrojet region provides the
best avenue to be channeled from the dayside to meet the vertical
current demands of the F region neutral wind dynamo after sunset. The
conductivity reduction in the E region due to the recombination of
ionization and the plasma uplift enhances the horizontal (eastward)
electric field and thereby increases the speed of the uplift. Thus
the dynamic adjustment of ionization has an unstable, feedback
relationship with the electric fields which may explain the night to
night variability of the horizontal electric field enhancement.
Title: Modeling the Ionospheric Response to Artificially Produced
Density Enhancements
Authors: Cakir, S.; Haerendel, G.; Eccles, J. V.
Bibcode: 1992JGR....97.1193C
Altcode:
The motion of plasma density enhancements (barium clouds) artificially
introduced into the postsunset equatorial E region is investigated
with a two-dimensional model incorporating flux tube integrated
quantities. The temporal development of the ionosphere, in which the
density perturbations are imbedded, is derived from a one-dimensional
set of relations modeling plasma transport and the vertical electric
field from initial conditions and a prescribed variation of the
horizontal electric field as a function of time. The calculations show
that the strong horizontal shear flows existing at the nighttime F
region ledge (where the perturbations were placed) reduce the growth
of polarization fields associated with the enhancements and adjacent
relative depletions of plasma for weak perturbations. The reason
is that the perturbations develop a strong tilt with respect to the
horizontal. More massive density perturbations lead to stronger drop
velocities with respect to the rising ambient plasma. At a later
time they develop secondary horizontal density perturbations on the
side unstable to E×B drift instability due to the motion of neutral
constituents. When rising ``bubbles'' of low density are produced,
they (1) form on the steepened eastward side of the enhancement
perturbation, (2) have a width comparable to the scale of the
enhancement perturbation, and (3) are most easily produced when the
enhancement perturbation size is comparable to the scale height of the
integrated density. These simulations show why experimental efforts
of initiating rising bubbles and equatorial spread F have not been
successful. The experiments require larger-scale and stronger density
perturbations than what can be achieved with conventional sounding
rocket releases of barium vapors.
Title: Stimulated auroral precipitation by wave-particle interactions:
Implications from the CRRES satellite mission
Authors: Schriver, David; Haerendel, Gerhard
Bibcode: 1991JGR....9611403S
Altcode:
The interaction of charged particles with plasma waves is one of the
mechanisms which can cause the precipitation of energetic particles
from the Earth's radiation belts. In the inner plasma sheet of the
magnetotail, electromagnetic cyclotron waves can resonate with the bulk
of the ambient energetic electron distribution only if an additional
cold dense plasma population is present. In an attempt to artificially
stimulated auroral electron precipitation, one experiment to be carried
out during the Combined Release and Radiation Effects Satellite
(CRRES) mission will be to release lithium close to the Earth's
equatorial plane near geosynchronous orbit, along field lines that
map to the diffuse auroral region. As the lithium is photoionized, a
dense cold plasma cloud will be created within the background energetic
population causing increased whistler wave growth. To support the CRRES
Stimulated Electron Precipitation (STEP) experiment theoretically,
a quantitative study is presented examining wave growth, propagation,
and trapping of electromagnetic whistler waves within the released
cold plasma cloud. Results show that for a background thermal electron
temperature anisotropy of T⊥/T∥>1.2,
whistler wave growth rates are greatly increased by the presence of the
cold electrons, and the waves can be trapped in the cloud. Because of
a maserlike effect, intense standing waves with amplitudes the order
of a few nanotesla will be generated within a frequency range of about
50×500 Hertz. The waves will reach their largest amplitudes about 20
s after release, causing strong electron pitch angle diffusion into the
loss cone, which can be detected as enhanced diffuse aurora at Earth.
Title: Interpretation of the electric fields measured in an
ionospheric critical ionization velocity experiment
Authors: Brenning, N.; Fälthammar, C. -G.; Haerendel, G.; Kelley,
M. C.; Marklund, G.; Pfaff, R.; Providakes, J.; Stenbaek-Nielsen,
H. C.; Swenson, C.; Torbert, R.; Wescott, E. M.
Bibcode: 1991JGR....96.9719B
Altcode:
This paper deals with the quasi-dc electric fields measured in the
CRITI ionospheric release experiment, which was launched from Wallops
Island on May 13, 1986. The purpose of the experiment was to study the
critical ionization velocity (CIV) mechanism in the ionosphere. Two
identical barium shaped charges were fired from distances of 1.99 km
and 4.34 km towards a main payload, which made full three-dimensional
measurements of the electric field inside the streams. There was
also a subpayload separated from the main payload by a couple of
kilometers along the magnetic field. The relevance of earlier proposed
mechanisms for electron heating in CIV is investigated in the light
of the CRITI results. It is concluded that both the ``homogeneous''
and the ``ionizing front'' models probably apply, but in different
parts of the stream. It is also possible that electrons are directly
accelerated by a magnetic-field-aligned component of the electric field;
the quasi-dc electric field observed within the streams had a large
magnetic-field-aligned component, persisting on the time scale of the
passage of the streams. The coupling between the ambient ionosphere and
the ionized barium stream in CRITI was more complicated than is usually
assumed in CIV theories, with strong magnetic-field-aligned electric
fields and probably current limitation as important processes. One
interpretation of the quasi-dc electric field data is that the
internal electric fields of the streams were not greatly modified by
magnetic-field-aligned currents, i.e., a state was established where the
transverse currents were to a first approximation divergence-free. It
is argued that this interpretation can explain both a reversal of the
strong explosion-directed electric field in burst 1 and the absence
of such a reversal in burst 2.
Title: Optical observations on the CRIT-II Critical Ionization
Velocity Experiment
Authors: Stenbaek-Nielsen, H. C.; Wescott, E. M.; Haerendel, G.;
Valenzuela, A.
Bibcode: 1990GeoRL..17.1601S
Altcode:
A rocket borne Critical lonization Velocity (CTV) experiment was
carried out from Wallops Island at dusk on May 4, 1989. Two barium
shaped charges were released below the solar terminator (to prevent
photoionization) at altitudes near 400 km. The ambient ionospheric
electron density was 5×105 cm-3. The neutral
barium jet was directed upwards and at an angle of nominally 45 degrees
to B which gives approximately 3×1023 neutrals with super
critical velocity. Ions created by a QV process in the region of the
neutral jet would travel up along B into sunlight where they can be
detected optically. Weïï defined ion clouds (max. brightness 750 R)
were observed in both releases. An ionization rate of 0.8%s-1
(125s ionization time constant) can account for the observed ion cloud
near the release field line» but the ionization rate falls off with
increasing distance from the release. It is concluded that a CIV process
was present in the neutral jet out to about 50 km from the release,
which is significantly further than allowed by current theories.
Title: A model for the electric fields and currents during a strong
Ps 6 pulsation event
Authors: Buchert, S.; Haerendel, G.; Baumjohann, W.
Bibcode: 1990JGR....95.3733B
Altcode:
On April 21, 1985, an intense Ps 6 pulsation event was observed with
the EISCAT radar and the EISCAT magnetometer cross. These measurements
serve as a reference for a new electrostatic model for the ionospheric
conductances, electric fields, and currents of the auroral structures
associated with the pulsations, whose auroral signatures are the
Ω bands. All parameters are essentially derived from the input
field-aligned current distribution. By varying this distribution and a
few free parameters in the relation between the conductances and the
upward current, the model is adjusted to the data. We find that by
a rearrangement of the upward current from a one-dimensional sheet
configuration to tongelike poleward extensions the observed event
is reproduced in a satisfactory way. Compared to previous works,
the Hall current is modulated in a different, less symmetric way,
and considerably lower field-aligned current densities are required.
Title: Climatological distribution of planetary waves in the middle
atmosphere
Authors: Brenning, N.; Faelthammar, C. -G.; Marklund, G.; Haerendel,
G.; Kelley, M.; Pfaff, R.
Bibcode: 1990AdSpR..10g..63B
Altcode: 1990AdSpR..10...63B
In the rocket experiment CRIT I, launched from Wallops Island on
May 13, 1986, two identical Barium-shaped charges were fired from
distances of 1.3 km and 3.6 km towards the main experiment payload,
which was separated from a sub-payload by a couple of km along the
magnetic field. The relevance of earlier proposed mechanisms for
electron heating in ionospheric critical velocity experiments is
investigated in the light of the CRIT I results. It is concluded
that both the 'homogeneous' and the 'ionizing front' models can be
applied, in different parts of the stream. It is also possible that
a third, entirely different, mechanism may contribute to the electron
heating. This mechanism involves direct energization of electrons in
the magnetic-field-aligned component of the dc electric field.
Title: Electrodynamic interaction between the CRIT I ionized barium
streams and the ambient ionosphere
Authors: Brenning, N.; Fälthammar, C. -G.; Haerendel, G.; Kelley,
M.; Marklund, G.; Providakes, J.; Stenbaek-Nielsen, H. C.; Swensson,
C.; Torbert, R. B.; Wescott, E. M.
Bibcode: 1990AdSpR..10g..67B
Altcode: 1990AdSpR..10R..67B
In the CRIT I Critical Velocity experiment, launched from Wallops
Island on 13 May, 1986, two fast barium streams were ejected by means
of shaped charges. Their electrodynamic interaction with the ambient
ionosphere is discussed. An outstanding feature of the DC electric
field observed within the streams was a large magnetic-field-aligned
component, persisting on the time scale of the passage of the
streams. One interpretation of the DC electric field data is that the
internal electric fields of the streams is not greatly modified by
Birkeland currents, i.e. a state is established, where the transverse
currents are to a first approximation divergence-free. It is argued
that this interpretation can explain why a reversal of the strong
explosion-directed electric field was observed in the first explosion
but not in the second (more distant one).
Title: Dynamics of a barium release in the magnetospheric tail
Authors: Mende, S. B.; Swenson, G. R.; Geller, S. P.; Doolittle,
J. H.; Haerendel, G.; Valenzuela, A.; Bauer, O. H.
Bibcode: 1989JGR....9417063M
Altcode:
The second magnetospheric tail Ba release of the AMPTE program on
May 13, 1985, was observed by several field stations. A Fabry-Perot
imager was operated at Mt. Hamilton, California, to measure the
line-of-sight velocity of the barium ions in the tail. Simultaneous
imaging observations were made from there and from El Leoncito in
Argentina. From the two-station imaging data sets we have obtained
cloud position by triangulation. The ion cloud bulk velocity was
obtained from the position measurements and was intercompared with the
Fabry-Perot direct velocity measurements. The triangulated barium ion
cloud appeared to be field aligned, and its triangulated direction
was in excellent agreement with the Tsyganenko-Usmanov magnetic
field model. Following the initial expansion phase and the magnetic
cavity formation, the barium cloud became magnetized by the ambient
magnetospheric magnetic field. The bulk of the ion cloud was moving
very slowly compared to the ambient ion velocity, which was measured
by the nearby IRM satellite and which was of the order of several
hundred kilometers per second. The slow motion of the barium ions was
attributed to an ``electrostatic cavity'' formation at the boundary
of the high-density cloud, which excluded the ambient electric field
by polarization. Several morphological changes of the ion cloud were
obsevbed during the following period, which resulted in the bifurcation
of the cloud and the formation of a distinct S shape. Thus the cloud
appeared to exclude the ambient convection electric fields, and at
the same time it remained responsive to some time-dependent field
configuration changes. Thirty-five minutes after cloud release, the
cloud suddenly brightened and accelerated in the antisunward direction,
tending to take up the local plasma velocity. This acceleration
coincided with an increase in the ambient magnetic field and the plasma
velocity. There was no clear evidence that the change in the ambient
conditions was a direct cause of the observed cloud behavior.
Title: Cosmic linear accelerators.
Authors: Haerendel, G.
Bibcode: 1989plap.work...37H
Altcode:
The existence of field-aligned potential drops is related to unstable
field-aligned currents. It is postulated that the region of instability,
once set up, can propagate spontaneously into the interior of the
current circuit, like a fracture in a stressed solid body, and thus
achieve a fast magnetic stress relief. Most of the released magnetic
energy is converted into kinetic energy of field-aligned particle
beams. Parallel voltage and energy flux depend on the primary magnetic
stress, the propagation properties of shear Alfvén-waves, and the
threshold for current instability. Numerical examples for the efficiency
of such an acceleration process are given for three cosmical situations.
Title: Three-dimensional plasma structures with anomalous flow
directions near the Earth's bow shock
Authors: Paschmann, G.; Haerendel, G.; Sckopke, N.; Möbius, E.;
Lühr, H.; Carlson, C. W.
Bibcode: 1988JGR....9311279P
Altcode:
We have examined AMPTE IRM data obtained in the solar wind near the
Earth's bow shock and found 16 well-defined cases where a region of
hot subsonic plasma is embedded in the solar wind. Such structures had
been observed first with instruments on ISEE 1 and 2 and later on AMPTE
UKS and distinguished from bow shock crossing. Our observations confirm
some of the earlier findings, notably the event profile, showing a hot,
low-density core flanked by narrow regions of high density and strong
magnetic field. We also find the low (~200 km/s) flow velocities,
strongly deflected from the solar wind, and we substantially strengthen
the local time dependence of the flow which invariably is directed
dawnward from prenoon events and duskward for postnoon events. Our
results differ from the reported ISEE results in two respects. First,
the flows we observe tend to have larger angles relative to the solar
wind, and they often even have a sunward component. Second, the events
we have selected cannot be described as diamagnetic cavities. On the contrary, the magnetic fields are usually significantly
enhanced. This apparent discrepancy may simply result from different
event selection criteria. A quantitative analysis of the regions
flanking the hot core shows they consist of fast, nearly perpendicular,
supercritical shocks on the outside and tangential discontinuities on
the inside. We find a systematic difference between the orientations
of the leading and trailing edge boundary normals. While the former are
directed largely transverse to the solar wind flow, the latter are more
aligned with the solar wind. Another new finding concerns the presence
of enhanced fluxes of >70-keV nearly electrons which appear to be
of magnetospheric origin. The majority of events are associated with
directional discontinuities in the interplanetary magnetic field. We
have also found events which are not embedded in the solar wind but
occur between the solar wind and the magnetosheath, at times replacing
the regular bow shock. Among the mechanisms discussed as causes for
these events are the formation of sunward directed plasma jets from
magnetopause reconnection, or from amplification of magnetic stresses
associated with rotational discontinuities in the interplanetary
medium; sudden and localized enhancements of bow shock reflection;
and the interaction of the bow shock with tangential discontinuities
having a specific internal structure.
Title: Auroral arcs as manifestations of magnetic fractures.
Authors: Haerendel, G.
Bibcode: 1988aaam.book.....H
Altcode:
Properties of structured auroral arcs are derived from a model
according to which magnetic energy is dominantly converted into kinetic
energy of field-aligned particle beams. After a summary of the main
features of the fracture model, the author addresses the relative
and absolute transverse scale lengths implied by this model. Then he
looks into the impact of the interaction between emitted Alfvén waves
and current generator on the structure of auroral arcs. He checks
the appropriateness of the used macroscopic description vis-à-vis
kinetic effects and presents an attempt to reconcile the current
instability/Alfvén wave picture with the mirror resistivity concept.
Title: Magnetometer and incoherent scatter observations of an intense
Ps 6 pulsation event
Authors: Buchert, S.; Baumjohann, W.; Haerendel, G.; La Hoz, C.;
Luehr, H.
Bibcode: 1988JATP...50..357B
Altcode:
A Ps 6 pulsation event during the recovery phase of a geomagnetic storm
in the morning sector of April 21, 1985 was recorded by the EISCAT
magnetometer cross in northern Scandinavia. Simultaneous measurements of
E- and F-region plasma parameters were taken by the EISCAT incoherent
scatter radar with a latitudinal scanning program. Electric fields
and height-integrated Hall and Pedersen conductivities are derived and
two-dimensional patterns of these quantities are constructed for one Ps
6 period. The observations can be explained by the ionospheric current
and electric field model suggested by Opgenoorth et al. (1983) which
includes the effects of both electric fields and conductance variations.
Title: The duskside plasmapause/ring current interface: Convection
and plasma wave observations
Authors: LaBelle, J.; Treumann, R. A.; Baumjohann, W.; Haerendel,
G.; Sckopke, N.; Paschmann, G.; Lühr, H.
Bibcode: 1988JGR....93.2573L
Altcode:
Three time intervals have been selected during which the Active
Magnetospheric Particle Tracer Explorers (AMPTE) Irm satellite traversed
the plasmapause around 2130, 1900, and 1730 LT. The cold plasma density
is monitored with the wave experiment whose frequency range includes the
upper hybrid and the plasma frequencies; in this manner, the plasmapause
is easily observed as a reduction in the plasma density from 10-100
cm-3 to 0-5 cm-3. The AMPTE
IRM three-dimensional plasma instrument detects ions in the energy range
20 eV to 40 keV and allows the determination of the inner edge of the
ring current ions, which penetrate the duskside plasmapause by 0.5-2
RE. This boundary is characterized by termination
of the plasmaspheric hiss and an outward pointing gradient in the
energetic ions. Another signature of this boundary is an eastward
current which is detectable by the plasma instrument as well as the
magnetometer; this current is consistent in direction and magnitude
with the diamagnetic current associted with the observed gradient in
the ring current ions. In two of the three cases, current-driven lower
hybrid waves occur. On all three days, the ring current overlap with the
plasmasphere is marked by sunward convection (opposite to corotation)
and by a plateau formation in the density profile, both of which
indicate that the ring current has a significant effect on the electric
field. On one of the three days (June 6, 1985), the region where the
ring current overlaps the plasmasphere is marked by electromagnetic
waves with frequencies below the local helium gyrofrequency. These
waves appear to be about an equal mix of the left-hand-polarized L
mode and the right-hand-polarized R mode ion cyclotron waves and seem
to support the general explanation of such low-frequency waves based
on GEOS and ATS observations. On all three days, the overlap
region is populated by magnetic pulsations with periods of the order
of minutes. These are accompanied by fluctuations in the cold plasma
density which are in phase with the compressional part of the pulsations
and seem roughly consistent with adiabatic variation in the cold plasma
density in response to the changes in the field.
Title: Observation of nonlinear wave decay processes in the solar
wind by the AMPTE IRM plasma wave experiment
Authors: Koons, H. C.; Roeder, J. L.; Bauer, O. H.; Haerendel, G.;
Treumann, R.
Bibcode: 1988STIN...8823713K
Altcode:
Nonlinear wave decay processes have been detected in the solar wind
by the plasma wave experiment aboard the AMPTE-IRM spacecraft. The
main process is generation of ultra-low-frequency ion-acoustic
waves from the decay of Langmuir waves near the electron plasma
frequency. Frequently this is accomplished by an enhancement of
emissions near twice the plasma frequency. This enhancement is
most likely due to the generation of electromagnetic waves from the
coalescence of two Langmuir waves. These processes occur within the
electron foreshock in front of the earth's bow shock.
Title: A model for transient electric fields associated with chemical
release experiments by rockets
Authors: Marklund, G.; Brenning, N.; Holmgren, G.; Haerendel, G.
Bibcode: 1988AdSpR...8a..85M
Altcode: 1988AdSpR...8R..85M
As a follow-up to the chemical release experiment Trigger in 1977,
the TOR rocket was launched from Esrange on 24 October 1984. A large
amplitude electric field pulse of 250 mV/m was detected shortly after
the explosion. The central part of the pulse was found to be clearly
correlated with an intense layer of swept up ambient particles behind a
propagating shockfront. The field was directed towards the centre of the
expanding ionized cloud, which is indicative of a polarisation electric
field source. An expression for this radial polarisation field is
derived and found to result in an excellent agreement with observations.
Title: Ionospheric response to chemical releases in the high latitude
E and F regions
Authors: Holmgren, G.; Marklund, G.; Eliasson, L.;
Opgenoorthf. Söraas, H.; Primdahl, F.; Haerendel, G.; Kintner, P. M.
Bibcode: 1988AdSpR...8a..79H
Altcode: 1988AdSpR...8...79H
The release of dense chemical clouds in the ionosphere has strong
influence on the electric field, plasma waves, and the energetic and
thermal plasma. The observed effects are associated with the expanding
neutral gas and with the localized conductivity enhancement caused
by the ionized cloud. We report the first results of an experiment
(Tor) performed at Esrange in October 1984. The observations are
compared with observations made in a similar experiment (Trigger) in
September 1977. In both experiments, strong electric field pulses were
observed immediately after the releases. Also, in both experiments,
enhanced energetic electron flux associated with the releases were
observed. However, the details of the energetic electron response
differ between the two experiments. This paper gives an overview of
the experiment and the associated Eiscat measurements. Details of the
observed electric field and particle observations are discussed in
separate papers.
Title: Active experiments. Proceedings of Symposium 1 of the COSPAR
Twenty-sixth Plenary Meeting, held in Toulouse, France, 30th June -
11th July 1986.
Authors: Haerendel, G.; Mendillo, M.
Bibcode: 1988AdSpR...8a....H
Altcode: 1988AdSpR...8Q....H
Recent investigations of the thermosphere, ionosphere, magnetosphere,
and solar wind by means of active experiments are examined in reviews
and reports. Topics discussed include plasma and neutral-gas injections,
electron- and ion-beam injections, vehicle-environment interactions,
and active wave experiments. Particular attention is given to the
results of the AMPTE experiments, computer simulations of ion-beam
propagation, the Charge-2 tethered rocket experiment, opportunities
for active wave experiments on the Space Station, and the physical
processes involved in ionospheric-heating experiments.
Title: A substorm resulting from energy storage in the magnetosphere
Authors: Jorgensen, T. S.; Lassen, K.; Heikkila, W. J.; Wickwar,
V. B.; Haerendel, G.
Bibcode: 1987AnGeo...5..511J
Altcode:
In order to study the problem whether magnetospheric substorms are
directly driven by solar wind energy or result from unloading of
such energy temporarily stored in the magnetosphere, it is necessary
to investigate substorms following long quiescent periods and to
observe solar wind parameters in proximity to the magnetosphere as
well as many high-latitude ionospheric parameters with good temporal
resolution. This study presents such observations obtained on November
29, 1984 by the AMPTE-IRM spacecraft just outside the bow shock and by
the Sondrestrom incoherent scatter radar plus several other instruments
in the earth's polar region. It is inferred from the observations that
solar wind energy was accumulated during a one to two hour period in
the magnetosphere before being unloaded and dissipated in the polar
ionosphere.
Title: On the potential role of concentrated field-aligned currents
in solarphysics.
Authors: Haerendel, Gerhard
Bibcode: 1987ESASP.275..205H
Altcode: 1987sspp.symp..205H
The consequences of the existence of intense field-aligned currents
on energy storage and dissipation in the solar atmosphere are
investigated. Joule heating may be the reason for the chromospheric
network as seen in H alpha and for plages in active regions. A wide
range of Ohmic dissipation rates can exist without altering the local
chromospheric temperature by more than a factor of two. Generation
of narrow current tubes by turbulent motions in and below the
photosphere could provide the energy to the corona released during
flares. The primary energy release during these events could proceed
by untwisting of the flux tubes. The high and strongly inhomogeneous
pressure distribution set up in the corona as a result of reconnection
in multiple narrow current sheets can act as generator of even more
intense currents (up to 1000 a/sqm A/m2). They generate the low
temperature flare by classical Joule heating of the chromosphere
and particle beams greater than 100 MeV by linear acceleration in
localized field-aligned potential drops, which may be preferentially
set up below the transition region.
Title: Plasma Transport Near the Magnetic Cavity Surrounding Comet
Halley
Authors: Haerendel, G.
Bibcode: 1987GeoRL..14..673H
Altcode:
The dominant forces resisting the transport of magnetic field into
the inner coma of a comet are ion mass loading from and friction
with the expanding neutral atmosphere. A magnetic cavity is thereby
created. Close to it the frictional force is most important. Careful
interpretation of the magnetic field profile measured during the
Giotto flyby of comet P/Halley reveals the existence of an inward
directed component of plasma flow of a few km/s, which drops to zero
at the boundary of the cavity. The energy transferred from the neutral
gas to the plasma by friction and mass loading is responsible for the
strongly elevated ion temperatures outside the magnetic cavity. Fitting
of the observed magnetic profile and ion temperature distribution yields
quantitative determinations of some crucial parameters of the coma.
Title: Observations and theory of the AMPTE magnetotail barium
releases
Authors: Bernhardt, P. A.; Roussel-Dupre, R. A.; Pongratz, M. B.;
Haerendel, G.; Valenzuela, A.; Gurnett, D. A.; Anderson, R. R.
Bibcode: 1987JGR....92.5777B
Altcode:
The barium releases in the magnetotail during the Active Magnetospheric
Particle Tracer Explorers (AMPTE) operation were monitored by
ground-based imagers and by instruments on the Ion Release Module. After
each release, the data show the formation of a structured diamagnetic
cavity. The cavity grows until the dynamic pressure of the expanding
ions balances the magnetic pressure on its surface. The magnetic field
inside the cavity is zero. The barium ions collect on the surface of the
cavity, producing a shell. Plasma irregularities form along magnetic
field lines draped over the surface of the cavity. The scale size of
the irregularities is nearly equal to the thickness of the shell. The
evolution and structuring of the diamagnetic cavity are modeled using
magnetohydrodynamics theory.
Title: Electron cyclotron harmonic waves observed by the AMPTE-IRM
plasma wave experiment following a lithium release in the solar wind
Authors: Roeder, J. L.; Koons, H. C.; Holzworth, R. H.; Anderson,
R. R.; Gurnett, D. A.; Bauer, O. H.; Haerendel, G.; Häusler, B.;
Treumann, R.
Bibcode: 1987JGR....92.5768R
Altcode:
An unexpected occurrence following the second lithium release by
the AMPTE-IRM spacecraft in the solar wind on September 20, 1984,
was the appearance of electron cyclotron harmonic emissions. These
emissions began about 50 s after the release and continued for several
minutes. Narrow-band emissions polarized perpendicular to the magnetic
field with amplitudes of approximately 10-5 V m-1
were observed in each of the first five harmonic bands. Unpolarized
diffuse emissions were also present at the same time. The diffuse
emissions extended from below the lowest measured frequency channel to
above the highest narrow-band emission with a maximum below the electron
cyclotron frequency. It will be shown that these observations are
inconsistent with their generation by several ion beam instabilities.
Title: Observation of nonlinear wave decay processes in the solar
wind by the AMPTE IRM plasma wave experiment
Authors: Koons, H. C.; Roeder, J. L.; Bauer, O. H.; Haerendel, G.;
Treumann, R.; Anderson, R. R.; Gurnett, D. A.; Holzworth, R. H.
Bibcode: 1987JGR....92.5865K
Altcode:
Nonlinear wave decay processes have been detected in the solar wind by
the plasma wave experiment aboard the Active Magnetospheric Particle
Tracer Explorers (AMPTE) IRM spacecraft. The main process is the
generation of ultralow-frequency ion acoustic waves from the decay of
Langmuir waves near the electron plasma frequency. Frequently, this
is accompanied by an enhancement of emissions near twice the plasma
frequency. This enhancement is most likely due to the generation of
electromagnetic waves from the coalescence of two Langmuir waves. These
processes occur within the electron foreshock in front of the earth's
bow shock.
Title: AMPTE IRM Observations of waves associated with flux transfer
events in the magnetosphere
Authors: LaBelle, J.; Treumann, R. A.; Haerendel, G.; Bauer, O. H.;
Paschmann, G.; Baumjohann, W.; Lühr, H.; Anderson, R. R.; Koons,
H. C.; Holzworth, R. H.
Bibcode: 1987JGR....92.5827L
Altcode:
The AMPTE IRM wave instrument has been applied to the study of flux
transfer events (FTE's). This initial investigation concentrates on
FTE's observed in the magnetosphere during the fall of 1984. The wave
morphology consists of four significant features: at frequencies below
the ion gyrofrequency, magnetic fluctuations occur with amplitudes of
the order of 1 nT; at frequencies from a few hertz to a few hundred
hertz, electric field fluctuations are observed which have a broadband
amplitude of a few millivolts per meter, which are perpendicularly
polarized at the lowest frequencies, and which are partly electrostatic
and partly electromagnetic; in the frequency range from 100 Hz to 10
kHz, broadband spikelike waves occur with a time-averaged amplitude
of about 0.1 mV/m; and near the electron plasma frequency, bursts
of waves occur at the boundaries of FTE's. In none of the 25 events
surveyed does the total broadband amplitude of all the waves exceed
a few millivolts per meter, an amplitude far too small to provide
the dissipation required by ``traditional'' reconnection models
in which the dissipation region has a thickness the order of an ion
gyroradius. Thus, either all of the FTE's are observed at some distance
from the difusion region, or the observable waves play no significant
role in the diffusion process, or ``traditional'' reconnection models
do not apply to reconnection in FTE's.
Title: On transient electric fields observed in chemical release
experiments by rockets
Authors: Marklund, G.; Brenning, N.; Holmgren, G.; Haerendel, G.
Bibcode: 1987JGR....92.4590M
Altcode:
As a follow-up to the successful chemical release experiment Trigger in
1977, the Trigger Optimized Repetition rocket was launched from Esrange
on October 24, 1984. As in the Trigger experiment, a large-amplitude
electric field pulse of 200 mV/m was detected shortly after the
explosion. The central part of the pulse was found to be clearly
correlated with an intense layer of swept up ambient particles behind
a propagating shock front. The field was directed toward the center
of the expanding ionized cloud, which is indicative of a polarization
electric field source. Expressions for this radial polarization field
and the much weaker azimuthal-induced electric field are derived from
a simple cylindrical model for the field and the expanding neutral
cloud. Time profiles of the radial electric field are shown to be in
good agreement with observations.
Title: Entry and dissipation of energy in the Earth's magnetosphere
Authors: Baumjohann, W.; Haerendel, G.
Bibcode: 1987ESASP.268..121B
Altcode: 1987sass.conf..121B
After a brief overview on topography and the flow of energy in
the earth's magnetosphere the authors will first focus on the
different processes by which solar wind energy enters the earth's
magnetosphere. Subsequently they will discuss some aspects of that
process by which most of this energy is dissipated, namely the
magnetospheric substorm.
Title: Erdmagnetismus und extraterrestrische Vorgänge
Authors: Baumjohann, Wolfgang; Haerendel, Gerhard
Bibcode: 1987NW.....74..181B
Altcode:
No abstract at ADS
Title: Das "Short Wavelength Spectrometer (SWS)" für das "Infrared
Space Observatory ISO"
Authors: Drapatz, S. W.; Genzel, R.; Haerendel, G.; Haser, L.;
Katterloher, R.; Melzner, F.; Stöcker, J.; de Graauw, Th.; Beintema,
D. A.; Luinge, W.; Ploeger, G.; Wesselius, P. R.; Wildeman, K.;
Wijnbergen, J.; Kamperman, Th. M.; van der Hucht, K. A.; van
Dijkhuizen, C. A. W.
Bibcode: 1987MitAG..68..201D
Altcode:
No abstract at ADS
Title: The short-wavelength spectrometer for ISO (Poster)
Authors: de Graauw, Th.; Beintema, D. A.; Luinge, W.; Ploeger, G.;
Wesselius, P. R.; Wildeman, K.; Wijnbergen, J.; Drapatz, S. W.; Genzel,
R.; Haerendel, G.; Haser, L.; Katterloher, R.; Melzner, F.; Stöcker,
J.; Kamperman, Th. M.; van der Hucht, K. A.; van Dijkhuizen, W. C. A.
Bibcode: 1987iawa.conf..438D
Altcode:
The Short-Wavelength Spectrometer for ISO comprises two grating
spectrometers with a resolving power of 1000 in the range 2.3 to 45
μm. Fabry-Perot etalons can boost the resolution to 30,000 in the
range 15 to 35 μm. The baseline detector configuration has Si:In,
Si:Ga, Si:P and Ge:Be detectors from the Battelle-Institut.
Title: Active plasma experiments.
Authors: Haerendel, Gerhard
Bibcode: 1987swe..conf..214H
Altcode:
Contents: Comets. Barium. Motions. Ion jets. Structure. Space as a
laboratory. Stimulation of equatorial spread-F. Critical velocity
ionization. Artificial comets.
Title: Tail exploration and tail formation with artificial plasma
clouds
Authors: Haerendel, G.
Bibcode: 1987magp.book..337H
Altcode:
The formation processes of cometlike tails in barium releases in
the solar wind are considered. The momentum coupling between the
two plasmas is studied from an MHD and a one-particle point of view,
respectively. The formation of a tail is believed to be a consequence
of momentum balance leading to ion injection from the rear side of
the plasma cloud in the downstream direction. It is noted that other
processes contributing to the formation and dynamics of the tail are ion
drag along the magnetic field due to the expansion of a heated electron
component and separations of magnetic substructures from the comet head.
Title: Waves and electric fields associated with the first AMPTE
artificial comet
Authors: Gurnett, D. A.; Anderson, R. R.; Ma, T. Z.; Haerendel, G.;
Paschmann, G.; Bauer, O. H.; Treumann, R. A.; Koons, H. C.; Holzworth,
R. H.; Lühr, H.
Bibcode: 1986JGR....9110013G
Altcode:
A variety of plasma wave and electric field effects were observed
during the AMPTE (Active Magnetospheric Particle Tracer Explorers)
solar wind barium release on December 27, 1984. Electron plasma
oscillations provided measurements of the electron density during
the entire event. Inside the diamagnetic cavity created by the ion
cloud, the electron density reached a peak of about 2×105
cm-3 and then decreased approximately as t-2
as the cloud expanded. A static electric field of about 1-2 mV/m
was detected in the diamagnetic cavity. This electric field is in
the same direction as the solar wind electric field, suggesting
that the solar wind electric field may be able to penetrate into the
cloud. As the spacecraft passed through the boundary of the diamagnetic
cavity, a region of compressed plasma and magnetic field was detected
upstream of the ion cloud with a peak density of about 104
cm-3 and magnetic field strength of 130 nT. This region of
compressed plasma is believed to be caused by solar wind plasma and
magnetic field lines draped around the nose of the ion cloud. Inside the
diamagnetic cavity, electrostatic emissions were observed in a narrow
band centered on the barium ion plasma frequency and in another band
at lower frequencies. These waves are believed to be short-wavelength
ion acoustic waves. Bursts of electrostatic waves were also observed
at the boundaries of the diamagnetic cavity, apparently caused by
an electron drift current along the boundary. An intense burst of
broadband electrostatic noise was observed near the outer boundary of
the plasma compression region with intensities of up to 140 mV/m. This
noise is apparently associated with a shocklike interaction between
the ion cloud and the solar wind. Growth rate computations show that
the noise can be accounted for by an electrostatic ion beam-plasma
interaction between the nearly stationary barium ions and the rapidly
moving solar wind protons.
Title: Complementary analysis and interpretation of the shocklike
electrostatic noise observed during the AMPTE solar wind lithium
releases
Authors: Brinca, A. L.; Moreira, A. A.; Serra, F. M.; Haerendel, G.;
Paschmann, G.
Bibcode: 1986JGR....9110167B
Altcode:
The original interpretation of the electrostatic noise observed
during the AMPTE solar wind lithium releases is complemented to
clarify the nature of the intervening instabilities, the role of the
particle populations on wave excitation, and the generation of the
higher-frequency (a few kilohertz) noise. The results suggest that
the lower frequencies are created by an electron beam instability
providing growth within a broad range of wave vector directions,
whereas a negative-energy, slow proton beam mode might contribute to
the existence of the higher noise frequencies.
Title: Electric field measurements during the Condor critical
velocity experiment
Authors: Kelley, M. C.; Pfaff, R. F.; Haerendel, G.
Bibcode: 1986JGR....91.9939K
Altcode:
The barium explosion of the Condor critical velocity experiment created
a complex electric field pulse detected in situ by a single-axis
electric field double probe on a separate spacecraft a few kilometers
away. The measured component of the pulse had a peak amplitude which
exceeded 320 m V/m. The sign of this component was consistent with
an electric field pointed back toward the explosion point. The large
electric field pulse arrived nearly simultaneously with the fastest
minor ions associated with the explosion. Just ahead of the pulse a
packet of nearly monochromatic waves (3460 Hz) was detected near the
oxygen lower hybrid frequency, with a measured electric field component
of 6 mV/m along the double-probe direction. The bulk of the barium
beam was accompanied by a quasi-dc electric field whose amplitude
was between 100 and 200 mV/m. The E×B drift associated with this
latter field was less than the speed of the main beam estimated fom
the time delay of the arrival of the initial beam-related waves and
particles. This implies a counterstreaming between the neutrals and
ions in excess of the critical ionization velocity for barium. This
region of the beam was accompanied by a peaked distribution in the soft
electron fluxes and by intense electric field fluctuations with peak
(one component) amplitudes exceeding 375 mV/m. The wave frequencies
were in the range 0.1fLH<=f<=fLH
where fLH is the barium lower hybrid frequency
((ΩiΩe)1/2/2π). The most
significant electron heating was associated with the most intense wave
activity. The observations provide evidence of several important links
which may be required in the critical velocity chain and are consistent
with theories which appeal to either the modified two-stream instability
or to an ion beam process. For example, the data support the hypothesis
that mechanical energy in the beam is converted to electrical energy
associated with cross-field currents and that these currents are
unstable to lower hybrid wave generation which subsequently heats
the electron gas. In principle, the electrons then ionize the neutral
gas to complete the loop. The observed (one component) lower hybrid
electric field wave intensity was less than that predicted for a fully
developed modified two-stream instability, which may be related to
the fact that the fastest-growing modes are inhibited by the finite
dimension of the beam parallel to the magnetic field. In turn, the
reduction in the observed lower hybrid wave amplitude may be related
to the low efficiency of the Alfvén process in the Condor experiment
geometry reported in the companion papers.
Title: Plasma waves associated with the first AMPTE magnetotail
barium release
Authors: Gurnett, D. A.; Anderson, R. R.; Bernhardt, P. A.; Lühr,
H.; Haerendel, G.; Bauer, O. H.; Koons, H. C.; Holzworth, R. H.
Bibcode: 1986GeoRL..13..644G
Altcode:
Plasma waves observed during the March 21, 1985, AMPTE magnetotail
barium release are described. Electron plasma oscillations provided
local measurements of the plasma density during both the expansion and
decay phases. Immediately after the explosion the electron density
reached a peak of about 4 × 105 cm-3, and
then started decreasing approximately as t-2.4 as the
cloud expanded. About 6 minutes after the explosion the electron
density suddenly began to increase, reached a secondary peak of
about 2.4 × 10² cm-3, and then slowly decayed down to
the pre-event level over a period of about 15 minutes. The density
increase is believed to be caused by the collapse of the ion cloud
into the diamagnetic cavity created by the initial expansion. The
plasma wave intensities observed during the entire event were quite
low. In the diamagnetic cavity electrostatic emissions were observed
near the barium ion plasma frequency, and in another band at lower
frequencies. A broadband burst of electrostatic noise was also observed
at the boundary of the diamagnetic cavity. Except for electron plasma
oscillations no significant wave activity was observed outside of the
diamagnetic cavity.
Title: Ion flow at comet Halley
Authors: Johnstone, A.; Coates, A.; Kellock, S.; Wilken, B.; Jockers,
K.; Rosenbauer, H.; Studemann, W.; Weiss, W.; Formisano, V.; Amata,
E.; Cerulli-Irelli, R.; Dobrowolny, M.; Terenzi, R.; Egidi, A.; Borg,
H.; Hultquist, B.; Winningham, J.; Gurgiolo, C.; Bryant, D.; Edwards,
T.; Feldman, W.; Thomsen, M.; Wallis, M. K.; Biermann, L.; Schmidt,
H.; Lust, R.; Haerendel, G.; Paschmann, G.
Bibcode: 1986Natur.321..344J
Altcode:
The three-dimensional positive ion analyser aboard the Giotto
spacecraft has been used to study the interaction between protons
and α-particles in the solar wind and positive ions from comet
Halley. Although the first impression of the overall structure is that
the plasma flow evolves smoothly as the nucleus is approached, three
sharp transitions of relatively small amplitude can be identified on
both the inbound and outbound legs of the trajectory. The outermost
one, at ~106 km from the nucleus, appears to be a multiple
crossing of a weak bow shock. The innermost one, at 80,000 km, is the
boundary where the flowing plasma becomes depleted. On a microscopic
scale, the turbulence created by the interaction between the two ion
populations extends to a distance of several million kilometres from
the nucleus. At Giotto's closest approach to the nucleus, the plasma
produced around the spacecraft by dust and gas impacts was much more
energetic than had been expected.
Title: The AMPTE artificial comet experiments
Authors: Valenzuela, A.; Haerendel, G.; Föppl, H.; Melzner, F.;
Neuss, H.; Rieger, E.; Stöcker, J.; Bauer, O.; Höfner, H.; Loidl, J.
Bibcode: 1986Natur.320..700V
Altcode:
In July last year and in December 1984, barium clouds were injected into
the solar wind from the AMPTE satellite. The clouds resembled those
of natural comets in that a head and tail were clearly visible. Tail
rays formed with speeds of a few tens of kilometres per second, and
other structures separated at even higher speeds. The comet head,
instead of moving slowly downstream, performed a lateral excursion of
several hundred kilometres. In the first of a series of six articles,
the properties of the `artificial comet' are described.
Title: Dynamics of the AMPTE artificial comet
Authors: Haerendel, G.; Paschmann, G.; Baumjohann, W.; Carlson, C. W.
Bibcode: 1986Natur.320..720H
Altcode:
Sweeping the plasma before it, the interplanetary magnetic field
quickly penetrated into an initially diamagnetic barium plasma
cloud. The field was strongly compressed and extended in the flow
direction. Ions accelerated by electric polarization fields formed
a visible tail at the rear of the cloud; their recoil balancing the
magnetic stresses. The dominant lateral motion of the head of the
artificial comet is attributed to a recoil of ions extracted by the
interplanetary electric field.
Title: Dayside equatorial-plane convection and IMF sector structure
Authors: Baumjohann, W.; Nakamura, R.; Haerendel, G.
Bibcode: 1986JGR....91.4557B
Altcode:
Using 1290 hours of GEOS-2 electron gun measurements between 0800 LT
and 1900 LT we have analyzed the dependence of dayside magnetospheric
convection in the equatorial plane at L=6.6 RE on
the IMF sector structure, i.e. IMF By≶0 and IMF
Bx≶0. For all IMF sector orientations the plasma flow
at noon is directed predominantly sunward with a slight dawnward
component. For positive IMF By the plasma convection
around 0900 LT has a duskward component which turns into a dawnward
component for negative IMF By values. The ratio
between the electric field amplitudes at 1500 LT (dusk sector)
and those at 0900 LT (dawn sector) increases from about 2 for
IMF By positive to 3-4 for negative IMF By
components. The convection pattern does neither show a dependence
on the Bx component of the IMF nor is it significantly
different for gardenhose (Bx.By<0) and
nongardenhose (Bx.By>0) orientations of the
IMF. These results support the idea of component merging rather than
the antiparallel merging hypothesis.
Title: Plasma flow and critical velocity ionization in cometary comae
Authors: Haerendel, G.
Bibcode: 1986GeoRL..13..255H
Altcode:
The plasma flow in the cometary coma is described by a simple relation
which results from the balance of magnetic stresses and drag forces,
the latter being mainly due to ion mass loading. Inertial and pressure
effects are not explicitly considered, but lumped into a correcting
factor of order unity. The relation is used to infer the ionization rate
due to the critical velocity effect. The limits, rcrit and
rlim, between which the effect dominates over photoionization
are evaluated. Critical velocity ionization stabilizes the plasma flow
speed at η-1/2 vcrit, where η is the overall
efficiency of energy transfer to the ionizing electrons. This speed is
estimated to be close to 20 km/s. At the outer limit, rlim,
there is a strong rise of plasma density as seen from outside. Inside
rcrit, recombination and ion-neutral friction come
into play. The contact surface is found to be largely determined
by ion-neutral collisions. A second neutral component of the order
of 10² cm-3 is predicted to originate from recombination
inside rlim. It is characterized by an antisunward flow with
∼ 20 km/s. Numerical values for the radial profile of ni
and of the critical boundaries (except the bow shock) are given. The
high plasma density found by ICE at the closest approach to comet
Giacobini-Zinner is interpreted as a result of the critical velocity
effect.
Title: Plasma waves observed by the IRM and UKS spacecraft during
the AMPTE solar wind lithium releases: Overview
Authors: Häusler, B.; Woolliscroft, L. J.; Anderson, R. R.; Gurnett,
D. A.; Holzworth, R. H.; Koons, H. C.; Bauer, O. H.; Haerendel, G.;
Treumann, R. A.; Christiansen, P. J.; Darbyshire, A. G.; Gough, M. P.;
Jones, S. R.; Norris, A. J.; Lühr, H.; Klöcker, N.
Bibcode: 1986JGR....91.1283H
Altcode:
The two September 1984 solar wind lithium releases produced a rich
variety of plasma waves which have been measured in situ by the plasma
wave instrumentation on board the Active Magnetospheric Particle
Tracer Explorers (AMPTE) IRM and UKS spacecraft. Reflection of the
natural galactic and terrestrial electromagnetic radiation from the
dense Li plasma caused a cutoff in the high-frequency electric field
intensities from which the temporal and spatial variation of the plasma
density can be determined. Inside the diamagnetic cavity the electron
plasma frequency and also temporarily the Li plasma frequency have
been excited. The emission at the electron plasma frequency is
near the thermal fluctuation level. In addition, weak low-frequency
ion acoustic waves were observed. The boundary between the diamagnetic
cavity and the external magnetic field was found to be surprisingly
stable and contained extremely low levels of wave activity. In the
transition region from the diamagnetic cavity to the solar wind, high
wave activity at the medium and very low frequencies propagating mainly
in the ion acoustic and electrostatic cyclotron harmonic modes was
encountered. No wave magnetic fields were detected in this region. The
upstream edge of the transition region was characterized by a steep
decay in magnetic field strength and density and by a sudden increase
in the quasi-static electric field. At this time the ELF/MF rms wave
amplitude explosively increased to a value of 50 mV/m and remained
at an enhanced level for more than 1 min. The spectrum of this wave
activity is similar t the electrostatic noise observed in collisionless
shocks. Data from UKS indicate that during the releases, UKS was in
the magnetic transition zone. The wave activity at UKS was distinctly
different from that encountered by IRM. The intense emission at the
electrostatic shocklike transition was weaker than that on IRM and for
the second release appeared at a different time. This can be related
to the different positions of the two spacecraft with respect to the
interaction regions. Despite the high wave intensities the estimated
wave energy densities are, however, too low by orders of magnitude
of drive significant magnetic field diffusion during the in situ
observation times. Some differences in the wave excitations for the
two releases can be traced back to the different solar wind conditions.
Title: AMPTE lithium tracer releases in the solar wind: Observations
inside the magnetosphere
Authors: Krimigis, S. M.; Haerendel, G.; Gloeckler, G.; Mcentire,
R. W.; Shelley, E. G.; Decker, R. B.; Paschmann, G.; Valenzuela, A.;
Potemra, T. A.; Scarf, F. L.; Brinca, A. L.; Lühr, H.
Bibcode: 1986JGR....91.1339K
Altcode:
A release of approximately 3.3×1025 lithium
atoms was made on September 11 and again on September 20, 1984,
by the Active Magnetospheric Particle Tracer Explorers (AMPTE)
Ion Release Module (IRM) spacecraft at a geocentric distance of
~18.8 Re in the subsolar direction, creating an ion cloud
approximately 4 Re in diameter after one hour. Detailed
modeling of ion propagation to the bow shock and transport through
the magnetosheath shows that >20% (September 11) and >50%
(September 20) of the ions mapped to a 36-Re2
area around the stagnation point on the magnetopause. The AMPTE Charge
Composition Explorer (CCE) satellite, located inside the magnetosphere
with an apogee of 8.78 Re and inclination of 4.8°, at a
local time of about 1300 MLT, was instrumented to detect lithium ions
over the energy range from a few eV to >6 MeV. Detailed analysis of
the data for the several hours following the lithium releases shows
that no measurable lithium ion fluxes reached the location of the
CCE; upper limits to the lithium flux at L>8 are about 50 to 70
(cm2-sec-sr)-1 in the range 25-300
keV/e (Li/H>2×10-5), and about 0.1 to 1
(cm2-sec-sr)-1 in the range 45-100
keV/nucleon (Li/H~1×10-6). The implications
of these results are discussed in the context of current theoretical
models of plasma entry into and transport within the magnetosphere.
Title: Analysis and interpretation of the shocklike electrostatic
noise observed during the AMPTE solar wind lithium releases
Authors: Gurnett, D. A.; Ma, T. Z.; Anderson, R. R.; Bauer, O. H.;
Haerendel, G.; Häusler, B.; Paschmann, G.; Treumann, R. A.; Koons,
H. C.; Holzworth, R.; Lühr, H.
Bibcode: 1986JGR....91.1301G
Altcode:
During the Active Magnetospheric Particle Tracer Explorers (AMPTE) solar
wind lithium release on September 11, 1984, and again on September 20,
1984, an intense burst of electrostatic noise was observed near the
upstream edge of the ion cloud. Comparisons with measurements by the
IMP 6 and ISEE 1 spacecraft show that the spectrum and overall features
of this noise are very similar to electrostatic noise observed at the
earth's bow shock. A stability analysis using realistic parameters shows
that the electrostatic noise can be accounted for by an ion beam-plasma
instability caused by the solar wind proton beam streaming through the
nearly stationary lithium cloud. The growth rate of this instability is
largest when the ion density and solar wind proton density are similar,
which explains why the noise only occurs near the outer edge of the ion
cloud. The similarity to the noise in the earth's bow shock suggests
that a shock may exist in the solar wind plasma flow upstream of the
ion cloud. If the noise is associated with a shock, then it must be an
electrostatic shock, since the ion cyclotron radii are too small for the
existence of a MHD shock. Since the electrostatic instability occurs at
phase velocities near the lithium thermal velocity, the electrostatic
turbulence may play a role in heating the lithium ions and transferring
momentum from the solar wind to the ion cloud. The noise may also play a
role in the pitch angle scattering and diffusion of energetic electrons
observed in the vicinity of the ion cloud. Because of the similarity
to the solar wind interaction with the gaseous envelope of a comet,
it is expected that similar types of wave-particle effects may occur
upstream of comets.
Title: Plasma observations on AMPTE/IRM during the lithium releases
in the solar wind
Authors: Paschmann, G.; Carlson, C. W.; Baumjohann, W.; Loidl, H.;
Curtis, D. W.; Sckopke, N.; Haerendel, G.
Bibcode: 1986JGR....91.1271P
Altcode:
This paper investigates the lithium releases in the solar wind as
they appear in the measurements of ions and electrons above 20 eV/q
and 15 eV, respectively, made with the Max-Planck-Institut für
extraterrestrische Physik/University of California, Berkeley, fast
three-dimensional plasma instrument on AMPTE/IRM. The dominant effects
are the pick up of the newly created Li ions by the solar wind electric
field and the heating of electrons. When first observed, the beam of Li
ions is substantially broadened, probably as a result of its interaction
with the cross-streaming solar wind. Later on, when the Li density has
decreased, the Li beam becomes narrower than can be resolved by the
instrument. The observed increase of beam energies with time to more
than ~1 keV can be directly attributed to the expansion of the lithium
atoms with a maximum speed of ~3.8 km/s. Throughout the observations
the Li ions move nearly along the electric field direction. This is
a result of their large gyroradius. Shortly after the release, while
the spacecraft is still within the magnetic cavity, hot (E>70 eV)
electrons are observed. Their density and temperature is further
enhanced when entering the magnetic field compression region ahead of
the cavity, consistent with adiabatic heating. There is no evidence
in our data of a shock in the upstream region, nor of reflected solar
wind ions.
Title: Dayside Convection Viscous Interaction and Magnetic Merging
Authors: Baumjohann, Wolfgang; Haerendel, Gerhard
Bibcode: 1986ASSL..126..415B
Altcode: 1986swmc.conf..415B
Data from the GEO-2 electron gun experiment are used to analyze the
dependence of the dayside convection electric field at L = 6.6 on
solar wind and IMF conditions. The results indicate that dayside
convection is predominantly driven by dayside merging rather than
viscous interaction. The LT-dependence yields a dawn-dusk asymmetry with
the disk sector electric fields being about twice as strong as those
in the dawn sector. The regression coefficients are consistent with
a merging efficiency of about 20 percent. The regression constants,
of order 0.05 mV/m, apparently describe an electric field stemming
from the ionospheric wind dynamo.
Title: Active plasma experiments
Authors: Haerendel, G.
Bibcode: 1986ape..book.....H
Altcode:
The use of barium plasma clouds for spaceborne experiments and
ground-based observation is described. Luminous plasma clouds are
generated from releases of barium metal vapor in near-Earth space and
subsequently ionized by solar UV radiation. The clouds interact with
the magnetic and electric fields, constitute visible tracers of plasma
transport, develop odd shapes, and fine structure and can be used for
a variety of experiments simulating cosmic processes.
Title: Electron plasma waves in the solar wind: AMPTE/IRM and UKS
observations
Authors: Treumann, R. A.; Bauer, O. H.; Labelle, J.; Haerendel, G.;
Christiansen, P. J.; Darbyshire, A. G.; Norris, A. J.; Woolliscroft,
L. J. C.; Anderson, R. R.; Gurnett, D. A.; Holzworth, R. W.; Koons,
H. C.; Roeder, J.
Bibcode: 1986AdSpR...6a..93T
Altcode: 1986AdSpR...6R..93T
Selected events of plasma wave and electromagnetic emissions in
the earth's electron fore-shock region have been studied. Strong
emissions are observed in the plasma-wave band when the site of
the satellite is magnetically connected to the bow shock. These
emissions are generally highly fluctuating. Under certain conditions
one observes electromagnetic radiation at the second harmonic produced
locally. Electromagnetic emission generated at a position far away
from the site of the spacecraft is occasionally detected giving rise
to remote sensing of the bow shock. These emissions are related to
energetic electron fluxes.
Title: Observations of the artifically injected Porcupine xenon ion
beam in the ionosphere
Authors: Häusler, B.; Treumann, R. A.; Bauer, O. H.; Haerendel, G.;
Bush, R.; Carlson, C. W.; Theile, B.; Kelley, M. C.; Dokukin, V. S.;
Ruzhin, Yu. Ya.
Bibcode: 1986JGR....91..287H
Altcode:
A heavy (xenon) ion beam injected approximately perpendicular to
the ambient magnetic field into the collisionless ionospheric plasma
during the Porcupine campaign in March 1979 was observed over a range
of distances from the ion source and of time by instruments on board
the main payload and on a spatially separated probe. Plasma and field
measurements from these instruments are presented for different phases
of beam propagation. After an initial development of a diamagnetic
cavity around the ion source, one finds a buildup of the beam current
in the near zone of the beam for distances of less than R=15 m. At
larger distances the beam represents a current carrying about 90% of the
initial beam current of 4 A. The signature of the transverse magnetic
field is consistent with a strong current flowing in the vicinity of the
ion source at R<3 m along the magnetic field into the source. This
current is carried by the escaping beam electrons. In the near zone
the electric field is saturated (>0.1 V m-1),
indicating that part of the electron population follows the beam by
EΛB drift motion. In the intermediate and far zones the electric field
E⊥ is only about 10% of the expected maximum polarization
field. Neutralization of the beam has to be provided for different
processes and constitutes a major problem. From current conservation
it is concluded that field-aligned electron fluxes contribute to
depolarization of the beam, thereby closing the beam current system. No
significant deceleration or scattering of the beam ions is observed
over distances up to half of the ion gyroradius, so there is no violent
scattering of ions on self-generated ion plasma waves on the time scale
of observation. This is in agreement with one-dimensional numerical
simulations (Roth et al., 1983). The strong parallel electric fields
observed in the beam are attributed either to density gradients or to
anomalous resistivity. In future missions it will be most important
to resolve the electron distribution function on a time scale short
enough to obtain information about the field-aligned electron fluxes
contributing to the overall and local charge neutralization and current
closure in the beam.
Title: Künstliche Kometen.
Authors: Haerendel, G.
Bibcode: 1986PhyBl..42..134H
Altcode: 1986PhB....42..134H
No abstract at ADS
Title: Solar wind-plasma interaction - The AMPTE solar wind plasma
releases
Authors: Bauer, O. H.; Baumjohann, W.; Foeppl, H.; Haerendel, G.;
Haeusler, B.
Bibcode: 1986csms.coll..189B
Altcode:
A summary is given of the most important effects observed during the 3
AMPTE solar wind ion releases. Some of these effects may be of relevance
in comparable astrophysical situations when large amounts of matter are
injected into an ambient magnetized plasma streaming with a velocity
much larger than the sonic and Alfvenic Mach numbers. For detailed
presentations the reader is referred to the original publications
listed in the References.
Title: Plasma waves associated with the AMPTE artificial comet
Authors: Gurnett, D. A.; Anderson, R. R.; Häusler, B.; Haerendel,
G.; Bauer, O. H.; Treumann, R. A.; Koons, H. C.; Holzworth, R. H.;
Lühr, H.
Bibcode: 1985GeoRL..12..851G
Altcode:
Numerous plasma wave effects were detected by the AMPTE/IRM spacecraft
during the artificial comet experiment on December 27, 1984. As the
barium ion cloud produced by the explosion expanded over the spacecraft,
emissions at the electron plasma frequency and ion plasma frequency
provided a determination of the local electron density. The electron
density in the diamagnetic cavity produced by the ion cloud reached
a peak ≳5×105 cm-3, then decayed smoothly
as the cloud expanded, varying approximately as t-2. As
the cloud began to move due to interactions with the solar wind, a
region of compressed plasma was encountered on the upstream side of
the diamagnetic cavity. The peak electron density in the compression
region was about 1.5×104 cm-3. Later, a very
intense (140 mVolt/m) broadband burst of electrostatic noise was
encountered on the sunward side of the compression region. This noise
has characteristics very similar to noise observed in the earth's bow
shock, and is believed to be a shock-like interaction produced by an
ion beam-plasma instability between the nearly stationary barium ions
and the streaming solar wind protons.
Title: Waves and electric fields associated with the December 27,
1984, artificial comet
Authors: Gurnett, D. A.; Ma, T. Z.; Anderson, R. R.; Haerendel, G.;
Paschmann, G.
Bibcode: 1985iowa.reptT....G
Altcode:
A variety of plasma wave and electric field effects were observed during
the AMPTE (Active Magnetospheric Particle Tracer Explorers) solar wind
barium release. Electron plasma oscillations at the local electron
plasma frequency provided measurements of the electron density during
the entire event. A static electric field of about 1 to 2 mVolt/m
was detected in the diamagnetic cavity. This electric field is in
the same direction as the solar wind electric field, suggesting that
polarization charges in the ion cloud are not effective at shielding
out an external electric field. As the spacecraft passed through the
boundary of the diamagnetic cavity, a region of compressed plasma and
magnetic field was detected upstream of the ion cloud. This region of
compressed plasma is believed to be caused by solar wind plasma and
magnetic field lines draped around the noise of the ion cloud. Inside
the diamagnetic cavity electrostatic emissions were observed in a narrow
band centered on the barium ion plasma frequency and in another band
at lower frequencies. These waves are believed to be short wavelength
ion acoustic waves. Bursts of electrostatic waves were also observed
at the boundaries of the diamagnetic cavity, apparently caused by an
electron drift current along the boundary.
Title: A statistical study of wave poynting vectors measured during
long-period magnetospheric pulsations at geostationary orbit
Authors: Junginger, H.; Haerendel, G.; Melzner, F.
Bibcode: 1985JGR....90.8301J
Altcode:
Electric and magnetic field data measured by the electron beam
experiment and the magnetometer on board the geostationary satellite
GEOS 2 were used to investigate wave Poynting vectors associated with
long-period (150-600 s) magnetospheric pulsations. A total of 3580
vectors were calculated for pulsations occurring during 186 days in
the dayside magnetosphere. The ratio between the electric and magnetic
field wave amplitudes was in general well above the local Alfvén speed
and was found to increase with increasing wave frequency. The fraction
of electric field pulsations for which magnetic wave components could
also be identified was therefore larger for the low- and smaller for
the high-frequency events in the range 1.67-6.67 mHz. Poynting fluxes
were found to have values between 1010 and 10-5
W/m2. For most pulsations with periods between 400 and
600 s the part of the vectors perpendicular to the ambient magnetic
field had an inward component and was directed toward the nose of the
magnetosphere in the prenoon and afternoon sectors. The behavior of
the corresponding components of the pulsations with a 150- to 300-s
period was not as clear. For all events observed in the winter season
(between November 1, 1978, and February 28, 1979), 59% of the vectors
had a field-aligned component directed into the northern hemisphere,
whereas 41% of the vectors were directed southward. The frequency
dependence of the E/B ratio, the magnitudes of the Poynting vectors,
and their directional distributions are consistent for most events
with the picture of standing shear Alfvén waves caused by solar wind
driven surface waves on the outer boundaries of the magnetosphere.
Title: Magnetospheric convection observed between 0600 and 2100 LT:
Solar wind and IMF dependence
Authors: Baumjohann, W.; Haerendel, G.
Bibcode: 1985JGR....90.6370B
Altcode:
Using data from the GEOS 2 electron gun experiment, we have analyzed the
dependence of the dayside convection electric field at L=6.6 (averaged
into 3-hour LT bins) on solar wind and interplanetary magnetic field
conditions. The convection electric field does not correlate at all
with the solar wind momentum flux density (correlation coefficients
of <0.25). Hence viscous interaction plays only a minor role
for equatorial magnetospheric convection at L=6.6. The correlation
coefficients for convection electric field versus merging electric field
are of the order of 0.5-0.6, thus indicating that dayside convection is
predominantly driven by dayside merging. The regression coefficients,
describing the (LT-dependent) transfer of the merging electric field
to synchronous orbit, are of the order of 0.1-0.2. Their LT dependence
follows approximately that described by a Volland-Stern model with γ=2,
except that the regression analysis yields a dawn-dusk asymmetry with
the dusk sector electric fields being about twice as strong as those in
the dawn sector. For the above shielding factor (γ=2) the regression
coefficients are consistent with a merging efficiency of about 20%. The
regression constants (of the order of 0.05 mV/m) apparently describe an
electric field stemming from the ionospheric wind dynamo. A comparison
of the electric field described by the regression constants and two
empirical models of quite day electric fields implies that these models
still include a substantial dawn-to-dusk electric field, thus indicating
the presence of solar wind dynamo action even during quite intervals.
Title: Plasma waves associated with the AMPTE artificial comet
Authors: Gurnett, D. A.; Anderson, R. R.; Hausler, B.; Haerendel,
G.; Bauer, O. H.
Bibcode: 1985iowa.reptS....G
Altcode:
Numerous plasma wave effects were detected by the AMPTE/IRM
spacecraft during the artificial comet experiment on December 27,
1984. As the barium ion cloud produced by the injection expanded
over the spacecraft, emissions at the electron plasma frequency and
ion plasma frequency provided a determination of the local electron
density. The electron density in the diamagnetic cavity produced by the
ion cloud reached a peak > or approximately 500,000/cc, then decayed
smoothly as the cloud expanded, varying approximately as 1/t sq. As
the cloud began to move due to interactions with by the solar wind,
a region of compressed plasma was encountered on the upstream side of
the diamagnetic cavity. The peak electron density in the compression
region was about 15000/cc. Later, a very intense (140 mVolt/m) broadband
burst of electrostatic noise was encountered on the sunward side of the
compression region. This noise has characteristics very similar to noise
observed in the Earth's bow shock, and is believed to be a shock-like
interaction produced by an ion beam-plasma instability between the
nearly stationary barium ions and the streaming solar wind protection.
Title: Analysis and interpretation of the shock-like electrostatic
noise observed during the AMPTE (Active Magnetospheric Particle
Tracer Explorers) solar wind lithium releases
Authors: Gurnett, D. A.; Ma, T. Z.; Anderson, R. R.; Bauer, O. H.;
Haerendel, G.
Bibcode: 1985iowa.reptR....G
Altcode:
During the AMPTE (Active Magnetospheric Particle Tracer Explorers) solar
wind lithium release on September 11, and again on September 20, 1984,
an intense burst of electrostatic noise was observed near the upstream
edge of the ion cloud. Comparisons with measurements by the IMP-6 and
ISEE-1 spacecraft show that the spectrum and overall features of this
noise are very similar to electrostatic noise observed at the Earth's
bow shock. A stability analysis using realistic parameters shows that
the electrostatic noise can be accounted for by an ion beam-plasma
instability caused by the solar wind proton beam streaming through the
nearly stationary lithium cloud. The growth rate of this instability is
largest when the ion density and solar wind proton density are similar,
which explains why the noise only occurs near the outer edge of the ion
cloud. The similarity to the noise in the Earth's bow shock suggest
that a shock may exist in the solar wind plasma flow upstream of the
ion cloud. If the noise is associated with a shock, then it must be
an electrostatic shock, since the ion cyclotron radii are too small
for the existence of a MHD shock. Since the electrostatic instability
occurs at phase velocities near the lithium thermal velocity, the
electrostatic turbulence may play a role in heating the lithium ions
and transferring momentum from the solar wind to the ion cloud.
Title: Magnetospheric convection observed between 0600 and 2100 LT:
variations with Kp
Authors: Baumjohann, W.; Haerendel, G.; Melzner, F.
Bibcode: 1985JGR....90..393B
Altcode:
Using data from the GEOS 2 electron gun experiment, we have constructed
average patterns of the convective flow of plasma in the equatorial
plane at L=6.6 between 0600 and 2100 LT and for Kp ranging between 0 and
4. During very quiet conditions (Kp=0-1) the plasma flows predominantly
westward with an outward component before noon and an inward component
thereafter. The most likely dominant agent for this kind of convection
is the atmospheric dynamo electric field. For moderate activity (Kp=3-4)
the plasma flows as predicted by a Volland-Stern-type dawn-to-dusk
cross-tail electric field model (if the atmospheric dynamo effect is
subtracted) with a shaping factor close to 3 and the axis of symmetry
rotated toward earlier local times. The shielding of the cross-tail
electric field from the inner magnetosphere seems to be somewhat
weaker on the dayside than on the eveningside. During times of Kp=2
sunward convection and atmospheric dynamo effect seem to compete,
i.e., sunward convection prevails, but our average pattern apparently
is still substantially influenced by the atmospheric dynamo field.
Title: Overview of Li and Ba plasma injections in the solar wind.
Authors: Haerendel, G.
Bibcode: 1985JHATD...6..263H
Altcode:
No abstract at ADS
Title: Plasma wave observations during the AMPTE lithium and barium
releases.
Authors: Gurnett, D. A.; Anderson, R. R.; Bauer, O. H.; Haerendel,
G.; Häusler, B.; Treumann, R. A.; Koons, H. C.; Holzworth, R. H.
Bibcode: 1985JHATD...6..264G
Altcode:
No abstract at ADS
Title: Numerical simulations of Ba- and Li-plasma injections in the
solar wind.
Authors: Sachs, W.; Haerendel, G.
Bibcode: 1985JHATD...6Q.264S
Altcode:
No abstract at ADS
Title: Plasma observations on AMPTE/IRM for the lithium and barium
releases in the solar wind.
Authors: Paschmann, G.; Baumjohann, W.; Sckopke, N.; Haerendel, G.;
Carlson, C. W.; Curtis, D. W.
Bibcode: 1985JHATD...6..264P
Altcode:
No abstract at ADS
Title: Doppler imaging of the AMPTE "Artificial comet" release.
Authors: Rees, D.; Haerendel, G.; Bryant, D.
Bibcode: 1985JHATD...6..263R
Altcode:
No abstract at ADS
Title: An ion beam-plasma instability for explaining the electrostatic
noiseassociated with the AMPTE solar wind ion releases.
Authors: Ma, T. Z.; Gurnett, D. A.; Anderson, R. R.; Bauer, O. H.;
Haerendel, G.; Häusler, B.; Paschmann, G.; Treumann, R. A.; Koons,
H. C.; Holzworth, R. H.
Bibcode: 1985JHATD...6..265M
Altcode:
No abstract at ADS
Title: Electron number density from the AMPTE/IRM plasma wave
experiment during solar wind lithium and barium releases.
Authors: Anderson, R. R.; Gurnett, D. A.; Häusler, B.; Treumann,
R. A.; Bauer, O. H.; Haerendel, G.; Koons, H. C.; Holzworth, R. H.
Bibcode: 1985JHATD...6..265A
Altcode:
No abstract at ADS
Title: Upstream VLF waves seen following the AMPTE plasma releases.
Authors: Holzworth, R. H.; Onsager, T.; Koons, H. C.; Anderson, R. R.;
Gurnett, D. A.; Haerendel, G.; Bauer, O. H.; Treumann, R. A.
Bibcode: 1985JHATD...6..265H
Altcode:
No abstract at ADS
Title: AMPTE-IRM (Active Magnetospheric Particle Tracer Explorers -
IonRelease Modul). Flugerfahrung nach einjähriger Mission.
Authors: Häusler, B.; Bauer, O. H.; Haerendel, G.; Melzner, F.;
Stöcker, J.
Bibcode: 1985MPERp..45.....H
Altcode:
No abstract at ADS
Title: Observations of a pulsation event from the ground with balloons
and with a geostationary satellite
Authors: Iversen, I. B.; Block, L. P.; Broenstad, K.; Grard, R.;
Haerendel, G.; Junginger, H.; Korth, A.; Kremser, G.; Madsen, M. M.;
Niskanen, J.
Bibcode: 1984ESASP.217..633I
Altcode: 1984aims.rept..633I
A magnetospheric pulsation event with a period of 6 to 8 min was
observed with satellite and ground based instruments in the morning
sector. The GEOS 2 satellite observed a magnetosonic wave with a
Poynting vector directed towards the Earth. The variations of the
electric field at the satellite are almost identical to those at
the northern footprint of the geomagnetic field line through the
satellite. Balloon measurements of auroral X-rays and particle and VLF
measurements on the satellite suggest the existence of a wave-particle
interaction process.
Title: Simultaneous observations of a pulsation event from the ground,
with balloons and with a geostationary satellite on August 12, 1978
Authors: Iversen, I. B.; Madsen, M.; Block, L. P.; Brøntad, K.;
Ullaland, S.; Grard, R.; Haerendel, G.; Korth, A.; Kremser, G.;
Niskanen, J.; Tanskanen, P.; Torkar, K. M.; Reidler, W.
Bibcode: 1984JGR....89.6775I
Altcode:
A pulsation event with a period of 6-8 min has been observed
simultaneously by the geostationary satellite GEOS 2 and two balloon
located in the area magnetically conjugate to the satellite. The
balloons were equipped with electric field and X ray instruments. The
pulsation event occurred in the magnetic local time sector 0600-1100
determined by ground-based meaurements. The satellite instruments
observed the signature of a magnetosonic wave having a radially inward
directed Poynting vector. The electric field associated with the wave
was closely correlated with the electric field detected by the balloon
instrument near the footprint of the magneic field line through GEOS
2. The ground-based observations show that the wave phase pattern was
north-south straited and that it moved from east to west. The balloon
x-ray measurements showed a strongly pulsating particle precipitation,
in close correlation with the intensity of the energetic electron
flux and the VLF electromagnetic radiation measured on the satellite,
suggesting a wave-particle interaction process. The pulsations seem
to originate beyond the geosynchronous orbit. The study demonstrates
the usefulness of simultaneous measurements with a geostationary
satellite and instruments in the ground area magnetically conjugate
to the satellite.
Title: A statistical study of dayside magnetospheric electric field
fluctuations with periods between 150 and 600 s
Authors: Junginger, H.; Geiger, G.; Haerendel, G.; Melzner, F.; Amata,
E.; Higel, B.
Bibcode: 1984JGR....89.5495J
Altcode:
One hundred eighty-six days of electric field data from the GEOS
2 electron beam experiment have been used to study magnetospheric
fluctuations at geostationary orbit with periods between 150 and 600
s. While fluctuations are nearly always present in the electric field
data from the dayside magnetosphere with typical amplitudes between
0.2 and 0.5 mV/m, it is often hard to find well-defined concurrent
pulsations in the GEOS 2 magnetic field data. Most events occur near
noon and have the same characteristics: They are toroidal and nearly
linearly polarized, the sense of polarization and the orientation angles
of the polarization ellipses change sign near noon, the instantaneous
frequency of the fluctuations is correlated with the instantaneous
electron density, and in a given sector of the magnetosphere the sense
of polarization depends on the frequency. There is strong evidence
that these fluctuations are fundamental mode eigenoscillations of
field lines in the vicinity of the spacecraft which are generated in
the inhomogeneous plasma of the magnetosphere by some kind of solar
wind-driven surface waves at the magnetopause or at the low-latitude
boundary layer.
Title: Resonant Alfvén waves excited by a sudden impulse
Authors: Baumjohann, W.; Junginger, H.; Haerendel, G.; Bauer, O. H.
Bibcode: 1984JGR....89.2765B
Altcode:
On March 6, 19879, long-period hydromagnetic waves were excited in
the forenoon magnetosphere by a sudden impulse (SI). The plasma drift
velocity and magnetic field oscillations associated with these waves
were observed by the electron gun experiment and the magnetometer,
respectively, onboard the GEOS 2 satellite in the equatorial
plane. The waves had both compressional and transverse components and
had their probable source in a single, tailward traveling, large-scale
magnetopause surface ``wavelet'' (i.e., a single rarefaction/compression
pulse) caused by the passage of an interplanetary shock front. This
surface wavelet apparently coupled into the inner magnetosphere via
the field line resonance mechanism. The satellite observations and the
Poynting vectors calculated from these consistent with a location of
the resonance region earthward of GEOS 2 during the first 5 min after
the SI while the satellite was located just inside the resonance region
at later times. This shift in the relative location of the resonance
region was probably caused by an increase of the Alfvén velocity
as a result of a compression of the magnetosphere associated with
the sudden impulse. The stronger-than-usual compressional magnetic
field component most likely had its origin in the relatively larger
wavelength of the SI-excited surface wavelet (compared with that of
Kelvin-Helmholtz-excited surface waves).
Title: Local time dependence of the response of the equatorial
electrojet toDP2 and SI disturbances.
Authors: Papamastorakis, I.; Haerendel, G.; Baumjohann, W.
Bibcode: 1984JGZG...54..213P
Altcode:
By using a method recently described by Papamastorakis and Haerendel
(1983), the local time dependence of equatorial magnetic-field
perturbations caused by the response of the equatorial electrojet to
DP2 and SI disturbances could be derived from geomagnetic records from
the Indian observatory Annamalainagar. For both types of disturbances,
Delta-H and thus the equatorial current shows a pronounced LT asymmetry
with the peak current density observed near 10 LT. This LT asymmetry
of the equatorial current is due to a tilt of the two-vortex electric
equipotential pattern (associated with a dawn-to-dusk polar-cap field)
towards earlier local times at low latitudes. This tilt has its origin
in the day-night asymmetry of the ionospheric conductivity distribution.
Title: Report of ESA's topical team on space plasma physics.
Authors: Dobrowolny, M.; Eliasson, L.; Gendrin, R.; Haerendel, G.;
Johnstone, A.; McKenna, S.; Morfill, G.; Vasyliunas, V.
Bibcode: 1984ESASP1070...38D
Altcode:
No abstract at ADS
Title: Magnetospheric plasma drift during a sudden impulse
Authors: Baumjohann, W.; Bauer, O. H.; Haerendel, G.; Junginger, H.;
Amata, E.
Bibcode: 1983JGR....88.9287B
Altcode:
An interplanetary shock front (monitored by the ISEE 1/2 satellite
pair) hit the earth's magnetosphere on October 17, 1978, around 0430
UT. The changes in magnetospheric plasma drift and magnetic field
associated with this sudden impulse (SI) were measured by GEOS 2 in the
equatorial plane near the dawn meridian. After the SI the plasma drift
first increased (in an inward direction), followed by an exponential
decay. The magnetic field changes were purely compressional with an
amplitude increase which also exponentially decayed. These features can
be explained by adiabatic (quasi-static) compression of the magnetopause
due to the increased solar wind pressure behind the shock front. In
addition, both data sets exhibit also the excitation of a highly damped
compressional hydromagnetic oscillation by the SI, thus hinting of a
second, wavelike component in the compression of the magnetosphere.
Title: Altitude and structure of an auroral arc acceleration region
Authors: Paschmann, G.; Papamastorakis, J.; Sckopke, N.; Haerendel,
G.; Shelley, E. G.
Bibcode: 1983JGR....88.7121P
Altcode:
During a rocket flight in the dayside auroral oval on December 17, 1974,
several examples of velocity dispersions of precipitating electrons
were observed. It is shown that the commonly employed interpretation of
such dispersions as resulting from a purely temporal modulation of the
source is not unique: the same dispersion effects can also be caused by
a moving source of finite width and constant intensity. This spatial
model is further improved by adding the dispersion originating from
a superimposed convection velocity. In general the source altitudes
implied by the two models (temporal and spatial) differ. For one of
the events analyzed the temporal model yielded a source altitude
of ~3000 km. Because of special circumstances this did not differ
significantly from the result obtained with the spatial model. The
second case analyzed was inconsistent with the temporal model and
required further modification of the spatial model to include an energy
dependent source width, in line with expectations from an acceleration
in a V shaped electric field pattern. Applying the latter model we
derive a source altitude of ~3500 to ~5000 km.
Title: Plasma drift measurements with the electron beam experiment
on GEOS-2 during long period pulsations on April 7, 1979
Authors: Junginger, H.; Bauer, O. H.; Haerendel, G.; Melzner, F.;
Higel, B.; Amata, E.
Bibcode: 1983GeoRL..10..667J
Altcode:
During almost the whole day of April 7, 1979, wave activity with
frequencies between 2 and 5 mHz and amplitudes between 5 and 20 km/sec
has been observed with the electron beam experiment on GEOS-2. No
corresponding activity showed up in the magnetic field data. The
waves observed in the dayside magnetosphere are nearly toroidal
and elliptically polarized. Their polarization is left-handed in
the forenoon sector and right-handed in the afternoon sector of the
magnetosphere. The orientation angles of the polarization ellipses on
average change sign near local noon. A comparison between the electron
number density as measured on the same spacecraft and the observed wave
frequencies shows that these waves are consistent with fundamental
mode eigenoscillations of the magnetic field. The model according to
which solar wind driven surface waves at the outer boundaries of the
magnetosphere are the energy sources for this kind of pulsations is
supported by the tilt of the polarisation ellipses and by a switch in
the sense of polarization near local noon. GEOS-2 should be located
on the earthward side of the resonance in terms of this model.
Title: The Active Magnetospheric Particle Tracer Explorers (AMPTE)
program
Authors: Krimigis, S. M.; Haerendel, G.; McEntire, R. W.; Paschmann,
G.; Bryant, D. A.
Bibcode: 1983ESASP.195..317K
Altcode: 1983aes..rept..317K
The Active Magnetospheric Particle Tracer Explorers (AMPTE) spacecraft
carry out the release and monitoring of tracer ions (lithium and
barium) in the solar wind and within the distant magnetosphere for
studies of access of solar wind ions to the magnetosphere and the
convective-diffusive transport and energization of magnetospheric
particles. A single massive release of barium in the dawn magnetosheath
creates an artificial comet in the flowing solar wind plasma within
which diamagnetic effects, ionization, momentum exchange, ion transport
and visible phenomena are studied. Comprehensive measurements of the
composition and dynamics of the ambient Z or = 2 magnetospheric particle
populations at the geomagnetic equator, including the energy interval
(20 to 200 keV) of importance to the ring current are proposed.
Title: The Active Magnetospheric Particle Tracer Explorers program.
Authors: Krimigis, S. M.; Haerendel, G.; McEntire, R. W.; Paschmann,
G.; Bryant, D. A.
Bibcode: 1983JHATD...4....3K
Altcode:
The Active Magnetospheric Particle Tracer Explorers (AMPTE) mission
will release and monitor tracer ions (lithium and barium) in the solar
wind and within the distant magnetosphere in order to study access of
solar wind ions to the magnetosphere and the processes that transport
and accelerate magnetospheric particles. In addition, a single massive
release of barium in the dawn magnetosheath will create a visible
artificial comet in the flowing solar wind plasma within which studies
of a number of different plasma effects will be made.
Title: Towards an artificial comet.
Authors: Haerendel, G.
Bibcode: 1983ESAJ....7..135H
Altcode:
The Active Magnetospheric Particle Tracer Explorers mission will
perform a large barium release in the magnetosphere, on its morning
flank. The barium plasma's interaction with the solar wind flow will
in many ways resemble the processes occurring in the ionized coma of a
comet. The downstream side may develop a turbulent wake and be slowly
filled with rays emerging from the head of the artificial comet which
are caused by a fast trapping of the solar wind magnetic field in the
plasma cloud a few minutes after maximum expansion, due to anomalous
transport effects. The heating and acceleration of the ions causes
brightening because of the Doppler shifting of the barium resonance
lines out of the bottom of the solar Fraunhofer lines. Although the
visual phenomena may only last for several minutes, low light level
TV systems will be able to track the phenomena for 30-60 min.
Title: Über den Ursprung des Nordlichts.
Authors: Haerendel, G.
Bibcode: 1982S&W....21..508H
Altcode:
The Northern Lights arise from the interaction of the solar wind with
the earth's magnetosphere, atmosphere, and a region in between these
two. The physical processes giving rise to the Lights, the cause of
the Lights' structure and dynamics, the source of their energy, and the
reasons for their occurrence in particular areas are addressed. The role
of Alfven waves, field-parallel currents, ionization and dissociation
reactions, and feedback is considered. The ionosphere's action as a
screen and end resistance are discussed, showing how different types
of electromagnetic radiation and heating and acceleration of inert
gases result.
Title: Plasma and magnetic field characteristics of magnetic flux
transfer events
Authors: Paschmann, G.; Haerendel, G.; Papamastorakis, I.; Sckopke,
N.; Bame, S. J.; Gosling, J. T.; Russell, C. T.
Bibcode: 1982JGR....87.2159P
Altcode:
Plasma and magnetic field data from ISEE 1 and 2 are examined for
5 passes of the magnetopause region at 20°-40° northern latitudes
and ~0800 to 1215 hours local time. These intervals contained a total
of 15 well-defined magnetic flux transfer events, which occurred in
the magnetosheath as well as the magnetosphere. In either case, flux
transfer events are characterized by a mixture of magentosheath and
magnetospheric particles. This fact strongly supports the hypothesis
that flux transfer events represent encounters of reconnected flux
tubes. Inside all of the studied events, the magnetic field strength
as well as the sum of plasma and magnetic pressures is strongly
enhanced. This excess pressure appears to be balanced by the tension
of the ambient magnetic field lines as they are draped around the
reconnected flux tube. The different observed magnetic field signatures
are consistent with expectations for encounters of the flux tubes at
different relative locations. Only those events that appear to be
crossings of the flux tube close to its magnetopause crossing show
large (~100 km s-1) plasma flow speed ehnancements. These
increased velocities are restricted to the trailing portion of the
events and are directed at large angles with respect to the magnetic
field. One hypothesis is that the increased flow speeds are caused by
continued reconnection at the low-latitude boundaries of the flux tubes.
Title: Energetic ion composition in the subsolar magnetopause and
boundary layer
Authors: Peterson, W. K.; Shelley, E. G.; Haerendel, G.; Paschmann, G.
Bibcode: 1982JGR....87.2139P
Altcode:
Energetic ion mass spectrometer data obtained on ISEE 1 have shown
that the plasma in the subsolar magnetospheric boundary layer,
magnetopause, and adjacent magnetosheath have an ionospheric
component (He+ and O+) in addition to the
solar wind component (H+ and He++). We have
examined in detail nine intervals where the location of the subsolar
magnetopause and boundary layer are well defined by the ISEE 1 fast
plasma and magnetic field measurements. In five of the identified
boundary layer intervals, keV He+ ions were observed;
energetic O+ ions were seen, above background, in two of
the boundary layers where He+ was observed. The temporal
resolution of the ion mass spectrometer was too coarse to rule out
the possibility of He+ or O+ ions being present
in the four remaining intervals. Ionospheric He+ ions were
also observed in the magnetosheath in two (and O+ in one)
of the nine intervals studied.
Title: An Artificial Comet Experiment
Authors: Haerendel, G.; Haeusler, B.; Foeppl, H.; Paschmann, G.;
Rieger, E.; Valenzuela, A.
Bibcode: 1982ncgb.conf..181H
Altcode: 1982gbhc.work..181H
The joint U.S., West German and British Active Magnentospheric Particle
Tracer Explorers experiment (AMPTE) employs detectors from three
different satellites and will involve the injection of plasma into the
solar wind. The experimental situation is analogous to that of a comet
in that expanding neutral gases (barium and lithium) will interact with
the solar wind while they are being ionized. Such cometary coma plasma
interaction processes as the trapping of magnetic filed, the stretching
of field lines, and the erosion and acceleration of cometary plasma,
are expected to occur and to be visible through both remote imaging
and in situ plasma diagnostics carried by the three AMPTE satellites.
Title: Interaction of the Solar Wind with the Dayside Magnetosphere
Authors: Haerendel, G.; Paschmann, G.
Bibcode: 1982DEPS....4...49H
Altcode:
No abstract at ADS
Title: Alfvén's critical velocity effect tested in space.
Authors: Haerendel, G.
Bibcode: 1982ZNatA..37..728H
Altcode: 1982ZNaT...37..728H
A sounding rocket experiment involving the injection of a barium gas
jet in the upper ionosphere provided an opportunity of investigating
quantitatively several aspects of the beam-plasma interaction that
is the substance of Alfven's critical velocity effect. Whereas the
experimental data are presented elsewhere, this paper contains some
theoretical considerations of (1) the limiting neutral density for
which the ionization process can operate, (2) the interaction of
the freshly injected ions with the background plasma, and (3) the
microprocess which leads to collisionless electron tail formation. The
observed distribution of injected ions is consistent with the Townsend
condition on the beam-plasma discharge. The mass loading on the ambient
plasma, although locally high, has a weak effect on the dynamics of
the involved flux-tube because of the limited extent of the beam. The
most likely process by which energy is transferred from the freshly
generated ions to the electrons is an ion beam instability leading to
the excitation of lower hybrid waves
Title: Evidence for magnetic field reconnection at the earth's
magnetopause
Authors: Sonnerup, B. U. O.; Paschmann, G.; Papamastorakis, I.;
Sckopke, N.; Haerendel, G.; Bame, S. J.; Asbridge, J. R.; Gosling,
J. T.; Russell, C. T.
Bibcode: 1981JGR....8610049S
Altcode:
Eleven passes of the ISEE satellites through the frontside terrestrial
magnetopause (local time 0900-1700 GSM latitude 2-43°N) have been
identified, where the plasma velocity in the magnetopause and boundary
layer was substantially larger than it was in the magnetosheath. This
paper examines the nature of the plasma flow, magnetic field, and
energetic particle fluxes in these regions, with a view to determining
whether the velocity enhancements can be explained by magnetic-field
reconnection. The principle question is whether the observed difference
in tangential plasma velocity Δv between a point in the magnetopause or
boundary layer and a reference point in the adjacent magnetosheath, had
the direction and magnitude Δvtheory produced by the Maxwell
stresses in the magnetopause, assuming that the magnetosheath plasma
moved across the boundary. Except for its sign, Δvtheory
is shown to be independent of the normal magnetic field component
Bn and flow component vn. For the 11 cases, the
average ||Δv||/||Δv||theory was in the range 0.6-1.2, with
a composite average of 0.8. The average angular error was <25°,
with a composite average of 10°. The plasma results would require
10 of the crossings to have been located north of the reconnection
line (Bn<0), and one (at 2.4° N latitude) south of it
(Bn<0). The Bn values obtained from minimum
variance analysis of the magnetic data were mostly poorly determined,
but in general their signs were consistent with the plasma results. The
flow velocity across the magnetopause was also poorly determined but it
had a negative (inward) composite average as expected. In several cases
energetic magnetospheric particles with the proper flow anisotropy and
in one case, reflected magnetosheath particles, were observed outside
but adjacent to the magnetopause. All of these results support the
reconnection hypothesis. The energetic particles were also used to
identify the outer separatrix surface. In one case it was possible
to conclude from its location relative to the magnetopause that the
reconnection side was in the vicinity of the equatorial plane and
not in the cusp. The electric field tangential to the magnetopause is
inferred to be in the range 0.4-2.8 mV/m.
Title: Measurement of plasma drifts in planetary magnetospheres
Authors: Grard, R.; Haerendel, G.; Melzner, F.
Bibcode: 1981ESASP.164...97G
Altcode: 1981sse..conf...97G
The GEOS satellites instrumentation is described. Plasma drift velocity
and electric field are measured simultaneously and independently. The
electric field sensor is an antenna made of two spherical probes
separated by a distance of 40 m along a direction perpendicular
to the spin axis. The field component measured by the aerial is
derived from the difference between the electric potential of the two
electrodes. The strength and orientation of the total field vector is
computed, assuming that the electric and ambient magnetic fields are
perpendicular. Plasma drift is measured, using four electron guns and
one electron detector. The drift is evaluated by injecting an artificial
beam with a 90 deg pitch angle and measuring its displacement after
one or two gyrations.
Title: Balloon observation of ionospheric magnesium ions
Authors: Valenzuela, A.; Bauer, O.; Haerendel, G.
Bibcode: 1981JATP...43..785V
Altcode:
No abstract at ADS
Title: Gestaltbildung durch Instabilität
Authors: Haerendel, Gerhard
Bibcode: 1981NW.....68..314H
Altcode:
The terms growth and evolution can as well be applied to unstable
physical systems. The ability of instabilities to create visible shape
is being investigated. There are innumerable examples of that in the
universe. One class occurring in cosmical plasmas results from the
localized dissipation of energy stored in strongly sheared magnetic
fields. It leads to the appearance of dynamic luminous structures,
as for instance in solar flares and in the northern lights.
Title: A Cometary Plasma Experiment for the Mission to Comet Halley
Authors: Johnstone, A.; Bryant, D.; Edwards, T.; Hultquist, B.;
Formisano, V.; Biermann, L.; Luest, R.; Schmidt, H. U.; Feldman, W.;
Cerulli-Irelli, P.; Dobrowolny, M.; Egidi, A.; Terenzi, R.; Jockers,
K.; Rosenbauer, H.; Studemann, W.; Wilken, B.; Wallis, M.; Haerendel,
G.; Paschmann, G.; Winningham, J. D.; Reme, H.
Bibcode: 1981giot.proc...17J
Altcode:
No abstract at ADS
Title: Structure of the low-latitude boundary layer
Authors: Sckopke, N.; Paschmann, G.; Haerendel, G.; Sonnerup,
B. U. Oe.; Bame, S. J.; Forbes, T. G.; Hones, E. W., Jr.; Russell,
C. T.
Bibcode: 1981JGR....86.2099S
Altcode:
Observations at high temporal resolution of the frontside magnetopause
and plasma boundary layer, made with the Los Alamos Scientific
Laboratory/Max-Planck-Institut, Institut für Extraterrestrische
Physik, fast plasma analyzer on board the Isee 1 and 2 spacecraft, have
revealed a complex quasi-periodic structure of some of the observed
boundary layers: cool tailward streaming boundary layer plasma is seen
intermittently, with intervening periods of hot tenuous plasma which has
properties similar to the magnetospheric population. While individual
encounters with the boundary layer plasma last only a few minutes,
the total observation time may extend over 1 hour or more. One such
crossing, at 0800 hours local time and 40° northern GSM latitude, is
examined in detail, including a quantitative comparison of the boundary
layer entry and exit times of the two spacecraft. The data are found
to be compatible with a boundary layer that is always attached to the
magnetopause but where the layer thickness has a large-scale spatial
modulation pattern which travels tailward past the spacecraft. Included
are periods when the thickness is essentially zero and others when it is
of the order of 1 RE. The duration of these periods is highly
variable but is typically in the range of 2-5 min, corresponding to a
distance along the magnetopause of the order of 3-8 RE. The
observed boundary layer features include a steep density gradient at
the magnetopause, with an approximately constant boundary layer plasma
density amounting to about 25% of the magnetosheath density, and a
second abrupt density decrease at the inner edge of the layer. It
also appears that the purely magnetospheric plasma is ocassionally
separated from the boundary layer by a halo region in which the
plasma density is somewhat higher, and the temperature somewhat lower,
than in the magnetosphere. A tentative model is proposed in which the
variable boundary layer thickness is produced by the Kelvin-Helmholtz
instability of the inner edge of the layer and in which eddy motion
provides effective mixing within the layer.
Title: Further determination of the characteristics of magnetospheric
plasma vortices with Isee 1 and 2
Authors: Hones, E. W.; Birn, J.; Bame, S. J.; Asbridge, J. R.;
Paschmann, G.; Sckopke, N.; Haerendel, G.
Bibcode: 1981JGR....86..814H
Altcode:
Further studies of the vortices in magnetospheric plasma flow with
the Los Alamos Scientific Laboratory/Max-Planck-Institut (LASL/MPI)
fast plasma experiment on Isee 1 and 2 have revealed that the
pattern of vortical flow has a wavelength of ~20-40 RE
and moves tailward through the magnetosphere at speed of several
hundred kilometers per second. The tendency toward vorticity pervades
the total breadth of the plasma sheet tailward of the dawn-dusk
meridian. The sense of rotation of the plasma flow (as viewed from
above the ecliptic plane) is clockwise in the morningside of the
plasma sheet and counterclockwise in the eveningside. The sense of
rotation in the morning and evening boundary layers is reversed from
that in the contiguous regions of the plasma sheet. The occurrence of
vortical flow is independent of the level of geomagnetic activity but
is associated with long-period geomagnetic pulsations. We believe that
the source of the vortical motion is a Kelvin-Helmholtz instability
of the plasma boundary layer's inner surface (i.e., the interface
between the plasma sheet and the boundary layer) that has recently
been proposed by Sonnerup [1980].
Title: Artifical plasma jet in the ionosphere
Authors: Haerendel, G.; Sagdeev, R. Z.
Bibcode: 1981AdSpR...1b..29H
Altcode: 1981AdSpR...1...29H
The PORCUPINE sounding rocket project provided the opportunity to
study the dynamics of an artificially injected plasma beam in the
near-Earth space. The structure of the plasma beam, its propagation
across the magnetic field as well as the resulting wave phenomena will
be discussed.
Title: Electric fields in the dayside auroral oval
Authors: Jorgensen, T. S.; Mikkelsen, I. S.; Lassen, K.; Haerendel,
G.; Reiger, E.; Valenzuela, A.; Mozer, F. S.; Temerin, M.; Holback,
B.; Bjoern, L.
Bibcode: 1980JGR....85.2891J
Altcode:
The results from four independent electric field experiments flown
on three Black Brant 4 rockets in the forenoon dayside auroral oval
in December 1974 and January 1975 are correlated with ground-based
observations and rocket particle data. The electric field varied from
zero to 150 mV/m. The predominant plasma convection was toward noon
along the auroral oval with a smaller component directed toward the
polar cap. In one case, however, a reversal occurred within the oval
with plasma convection away from noon. Comparisons with magnetometer
data indicate that in the dayside auroral oval. Hall currents
sometimes are responsible for magnetic fluctuations observed on the
ground. Comparisons with particle data show that the magnitude of the
electric fields is inversely correlated with the electron energy flux.
Title: The Aries heat sink
Authors: Haerendel, G.; Jerger, J. J.; Jerger, J. H.
Bibcode: 1980ESASP.152..189H
Altcode: 1980urbp.symp..189H
The failure analysis performed for ARIES sounding rocket motor
failures, and the remedy developed for motor overheating are
described. The principal failure hypothesis was that the motor-dome
insulator fails under high gravity boost and the subsequent radiant
heating of the titanium motor dome weakens the pressure vessel. The
supporting heat transfer and ablation analyses are summarized. These
detailed analyses and digital simulations quantitatively correlated the
precise time-of-failure with known ablation and heat transfer rates and
established firm design criteria for the aluminum heat sink. Analysis
of the international magnetospheric study test rocket temperature data
is described. This analysis confirmed the validity of the design and
the effectiveness of the heat sink.
Title: The barium ion jet experiments of the Porcupine project
Authors: Haerendel, G.
Bibcode: 1980ESASP.152..507H
Altcode: 1980urbp.symp..507H
The injection of a barium plasma from a sounding rocket by the shaped
charge technique offers several possibilities that cannot be achieved
by conventional releases. This is due to high initial velocities of the
atoms of up to 14 km/sec. Most of the the applications are related to
the great heights that the ions can reach, but some depend directly
on the initial momentum. Typical applications are: tracing at high
altitudes, modifications, and alternate Ionization processes. Project
Porcupine contributions in this field are summarized.
Title: Auroral particle acceleration - an example of a universal
plasma process.
Authors: Haerendel, G.
Bibcode: 1980ESAJ....4..197H
Altcode:
The occurrence of discrete and narrow auroral arcs is attributed
to a sudden release of magnetic tensions set up in an intense
magnetospheric-ionospheric current circuit. At altitudes of several
thousand kilometers the condition of frozen-in magnetic fields can
be broken temporarily in thin regions corresponding to the observed
width of auroral arcs. This implies magnetic-field-aligned potential
drops of several kilovolts supported by certain anomalous transport
processes which can be maintained only in a quasi-stationary manner if
the current density exceeds a certain critical limit. The region of
field-aligned potential drops is structured by two pairs of standing
waves, which are generalized Alfven waves of large amplitude across
which the parallel electric field undergoes a finite jump.
Title: Plasma wave turbulence at the magnetopause: Observations from
ISEE 1 and 2
Authors: Gurnett, D. A.; Anderson, R. R.; Tsurutani, B. T.; Smith,
E. J.; Paschmann, G.; Haerendel, G.; Bame, S. J.; Russell, C. T.
Bibcode: 1979JGR....84.7043G
Altcode:
In this paper we investigate plasma wave electric and magnetic fields in
the vicinity of the magnetopause by using recent measurements from the
ISEE 1 and 2 spacecraft. Strong electric and magnetic field turbulence
is often observed at the magnetopause. The electric field spectrum of
this turbulence typically extends over an extremely large frequency
range, from less than a few hertz to above 100 kHz, and the magnetic
field turbulence typically extends from a few hertz to about 1 kHz. The
maximum intensities usually occur in the magnetopause current layer
and plasma boundary layer. Somewhat similar turbulence spectra are also
sometimes observed in association with flux transfer events and possible
'inclusions' of boundary layer plasma in the magnetosphere. In addition
to the broad-band electric and magnetic field turbulence, narrow-band
electrostatic emissions are occasionally observed near the electron
plasma frequency in the vicinity of the magnetopause. Two possible
plasma instabilities, the electrostatic ion-cyclotron instability
and the lower-hybrid-drift instability, are considered the primary
candidates for explaining the broad-band electric field turbulence. The
narrow-band electrostatic emissions near the local electron plasma
frequency are believed to be either plasma oscillations or electrostatic
waves near the upper-hybrid-resonance frequency.
Title: Plasma acceleration at the earth's magnetopause - Evidence
for reconnection
Authors: Paschmann, G.; Papamastorakis, I.; Sckopke, N.; Haerendel,
G.; Sonnerup, B. U. Oe.; Bame, S. J.; Asbridge, J. R.; Gosling, J. T.;
Russel, C. T.; Elphic, R. C.
Bibcode: 1979Natur.282..243P
Altcode:
Observations of high-speed plasma at the magnetopause in agreement
with theoretical predictions of magnetic field reconnection are
reported. Plasma ion and electron distributions measured by the
quadrispherical analyzers on board the ISEE 1 and 2 spacecraft
were obtained during the outbound traversal of the subsolar
magnetopause. Plasma flow speeds of up to 450 km/sec were observed in
the magnetopause layer, in contrast to speeds of 50 to 100 km/sec in the
adjacent magnetosheath. The observations agree with the predictions
of the reconnection model of the dayside magnetopause, in which
the magnetopause is described as a rotational discontinuity, or a
large-amplitude Alfven wave. It is noted that the lack of observations
of plasma acceleration in most other cases of favorable magnetic field
orientation could be a product of the rarity of magnetic recombination,
or its small scale and nonstationarity.
Title: The motion of depleted plasma regions in the equatorial
ionosphere
Authors: Anderson, D. N.; Haerendel, G.
Bibcode: 1979JGR....84.4251A
Altcode:
Depleted plasma regions in the equatorial ionosphere and their
associated motions have been observed by a variety of ground-based,
rocket-borne, and satellite instruments. Various theories based
primarily on the Rayleigh-Taylor instability mechanism, have been
proposed for the formation and motion of these bubbles. Numerical
studies in the past have incorporated local electron density depletions,
with Pedersen conductivities involving local ion-neutral collision
frequencies. Realizing that bubbles are actually depleted magnetic
flux tubes, we investigate the vertical E×B motion of these depleted
regions, incorporating flux tube integrated quantities of electron
content and Pedersen conductivity. A simple expression for the
polarization electric E1 inside the depleted flux tube is
used. The resulting calculations show that the vertical bubble velocity
as a function of time critically depends on the background ionospheric
electric field and that this dependence extends to much greater heights
than was previously thought. Bubble which are initiated at 350-km
altitude (1900 LT) with a 5% depletion in electron content attain an
upward velocity of 200 m/s at 1920 LT when the background electric
field is 0.6 mV/m. Bubble altitude at this time is 447 km with an 88%
depletion in electron content. In the absence of an ambient electric
field, 1 hour is required for the vertical bubble velocity to reach
200 m/s.
Title: Max-Planck-Institut für Physik und Astrophysik, Institut für
Astrophysik und Institut für extraterrestrische Physik. Jahresbericht
für 1978.
Authors: Kippenhahn, R.; Haerendel, G.
Bibcode: 1979MitAG..46..187K
Altcode:
No abstract at ADS
Title: Magnetospheric boundary layers. A Sydney Chapman
Conference. Proceedings of an international conference held in
Alpbach, Austria, 11 - 15 June 1979.
Authors: Battrick, B.; Mort, J.; Haerendel, G.; Ortner, J.
Bibcode: 1979ESASP.148.....B
Altcode: 1979mbl..rept.....B
No abstract at ADS
Title: Imaging the ionosphere in the light of magnesium ions from
balloon altitudes.
Authors: Valenzuela, A.; Bauer, O.; Haerendel, G.; Haser, L.
Bibcode: 1979scba.conf..203V
Altcode: 1979subr.proc..203V
Magnesium ions are continually produced in the lower E-region by
vaporization of meteorites and subsequent ionization. These ions can
serve as tracers for ionospheric transport processes in much the same
way as artificial barium clouds. Possible applications are: (1) in the
E-layer: wind-shear, turbulence, conductivity discontinuities; (2) in
the F-layer: ExB-drifts, in particular the equatorial fountain effect,
spread-F irregularities, and, possibly, anomalous transport effects
along magnetic field lines. MgII has two resonance lines at 279.5 and
280.2 microns. These lines can be observed from a balloon at height of
about 38 km. A payload with a wide-range camera has been developed and
will be flight-tested for the first time in November 1978. The camera
has a viewing angle of 90 deg and can resolve fine-structure of 400
to 800 m wavelength at 100 km altitude. The images are obtained with
an image converter - image intensifier - SEC TV-camera system. The
sensitivity limit is close to 100 rayleighs. Brightnesses of several
100 R up to a few kR are expected. Observations can be made when the
shadow line at 280 microns is above 85 km altitude and below the level
under investigation.
Title: The barium ion jet experiment of Porcupine 2
Authors: Rieger, E.; Foeppl, H.; Haerendel, G.; Valenzuela, A.; Zhulin,
I. A.; Gaidanskii, V. I.; Dokoulin, V. S.; Ruzhin, Iu. Ia.; Hallinan,
T. J.
Bibcode: 1979spre.conf..367R
Altcode: 1979spre.proc..367R
A shaped charge produced barium cloud was observed up to about 5000
km altitude from ground-based and air-borne stations. In contrast to
earlier shaped charge injections, no distinct ion jet was obtained;
rather a broad diffuse band was seen, in which three structures could
be identified. The high velocity parts of the structures travelled
upward in accordance with adiabatic motion. The transverse velocities
were directed predominantly west-south-westward. Differences between
the orientation of the Ba+-structures and model fields are attributed
to field-aligned currents.
Title: ISEE Plasma Observations near the Subsolar Magnetopause
(Article published in the special issues: Advances in Magnetospheric
Physics with GEOS- 1 and ISEE - 1 and 2.)
Authors: Paschmann, G.; Sckopke, N.; Haerendel, G.; Papamastorakis,
J.; Bame, S. J.; Asbridge, J. R.; Gosling, J. T.; Hones, E. W., Jr.;
Tech, E. R.
Bibcode: 1978SSRv...22..717P
Altcode:
The early ISEE orbits provided the opportunity to study the
magnetopause and its environs only a few Earth radii above the subsolar
point. Measurements of complete two-dimensional ion and electron
distributions every 3 or 12 s, and of three-dimensional distributions
every 12 or 48 s by the LASL/MPI instrumentation on both spacecraft
allow a detailed study of the plasma properties with unprecedented
temporal resolution. This paper presents observations obtained during
four successive inbound orbits in November 1977, containing a total
of 9 magnetopause crossings, which occurred under widely differing
orientations of the external magnetic field. The main findings are:
(1) The magnetosheath flow near the magnetopause is characterized by
large fluctuations, which often appear to be temporal in nature. (2)
Between ∼ 0.1 and ∼ 0.3R E outside the magnetopause,
the plasma density and pressure often start to gradually decrease as
the magnetopause is approached, in conjunction with an increase in
magnetic field strength. These observations are in accordance with
the formation of a depletion layer due to the compression of magnetic
flux tubes. (3) In cases where the magnetopause can be well resolved,
it exhibits fluctuations in density, and especially pressure and
bulk velocity around average magnetosheath values. The pressure
fluctuations are anticorrelated with simultaneous magnetic field
pressure changes. (4) In ope case the magnetopause is characterized
by substantially displaced electron and proton boundaries and a
proton flow direction change from upwards along the magnetopause to a
direction tranverse to the geomagnetic field. These features are in
agreement with a model of the magnetopause described by Parker. (5)
The character of the magnetopause sometimes varies strongly between
ISEE-1 and -2 crossings which occur ∼ 1 min apart. At times this is
clearly the result of highly non-uniform motions. There are also cases
where there is very good agreement between the structures observed by
the two satellites. (6) In three of the nine crossings no boundary
layer was present adjacent to the magnetopause. More remarkably,
two of the three occurred while the external magnetic field had a
substantial southward component, in clear contradiction to expectations
from current reconnection models. (7) The only thick (low-latitude)
boundary layer (LLBL) observed was characterized by sharp changes at
its inner and outer edges. This profile is difficult to reconcile with
local plasma entry by either direct influx or diffusion. (8) During the
crossings which showed no boundary layer adjacent to the magnetopause,
magnetosheath-like plasma was encountered sometime later. Possible
explanations include the sudden formation of a boundary layer at this
location right at the time of the encounter, and a crossing of an
‘inclusion’ of magnetosheath plasma within the magnetosphere. (9)
The flow in the LLBL is highly variable, observed directions include
flow towards and away from the subsolar point, along the geomagnetic
field and across it, tangential and normal to the magnetopause. Some
of these features clearly are nonstationary. The scale size over which
the flow directions change exceeds the separation distance (several
hundred km) of the two spacecraft.
Title: Plasma composition experiment on ISEE-A.
Authors: Shelley, E. G.; Sharp, R. D.; Johnson, R. G.; Geiss, J.;
Eberhardt, P.; Balsiger, H.; Haerendel, G.; Rosenbauer, H.
Bibcode: 1978ITGE...16..266S
Altcode:
The plasma composition experiment on ISEE-A consists of a pair of
high-sensitivity high-resolution energetic ion mass spectrometers. They
cover the entire mass range from 1 AMU to over 150 AMU in 64 channels
at each of 32 energy channels covering the energy per charge range
from 0 to approximately 17 keV/e. The objectives of the experiment are
to study the ion composition of the ring current, the plasma sheet,
the plasmasphere, the magnetosheath, and the solar wind in order to
establish the origin of the plasmas in the various regimes of the
magnetosphere and to identify mass and charge dependent acceleration,
transport, and loss processes.
Title: The frontside boundary layer of the magnetosphere and the
problem of reconnection
Authors: Haerendel, G.; Paschmann, G.; Sckopke, N.; Rosenbauer, H.;
Hedgecock, P. C.
Bibcode: 1978JGR....83.3195H
Altcode:
Further Heos 2 plasma and magnetic field data obtained in the frontside
boundary layers of he magnetosphere are presented. They reveal
hat the low-latitude extension of the entry layer is of a somewhat
different nature. The most pronounced difference with respect to the
entry layer in the cusp region is the substantial density jump at
the magnetopause. Furthermore, the low-latitude boundary layer tends
to be thinner and less turbulent, and the flow velocity inside the
layer is always lower than that of the adjacent magnetosheath. This
observation excludes large-scale reconnection at the front of the
magnetosphere as he origin of the layer. It is suggested that diffusive
entry of magnetosheath plasma and/or heating of detached plasma from the
plasmasphere leads to the formation of the layer. It appears likely that
reconnection is dominantly occurring as a transient process in the cusp
region and accompanies the eddy convection inside the entry layer. As
a consequence, magnetic flux is being eroded from the front of the
magnetosphere. This is in agreement with the signature of short-term
large-amplitude magnetic perturbations observed in the low-latitude
boundary layer.
Title: Microscopic plasma processes related to reconnection.
Authors: Haerendel, G.
Bibcode: 1978JATP...40..343H
Altcode:
A brief review of both macroscopic (hydromagnetic) and microscopic
theories of the reconnection or merging of magnetic field lines is
given. The importance of phenomena similar to vortex formation and
eddy convection in hydrodynamics is emphasized. Fluctuations observed
by HEOS 2 are shown to result from the passage of convection cells. An
eddy diffusion coefficient can be defined.
Title: The entry layer.
Authors: Paschmann, G.; Haerendel, G.; Sckopke, N.; Rosenbauer, H.
Bibcode: 1978JATP...40..257P
Altcode:
This paper summarizes briefly the plasma observations in the
magnetospheric entry layer and its environment made by the Max-Planck
Institute Instrument aboard the Heos 2 satellite. The main results are:
(1) the clear distinction between the entry layer (and its low-latitude
extension) and the plasma mantle, (2) the establishment of a further
division between the entry layer proper in the high-latitude polar
cusp regions, and a less dense layer at lower latitudes. If one also
considers the observed lack of correlation between the proprties of the
boundary layers and the orientation of the external magnetic field,
and the failure to detect the characteristic plasma flow expected
from magnetic merging in the sub-solar region, a reconsideration of
the processes and the location of solar wind plasma entry into the
magnetosphere appears necessary.
Title: Vertical winds and turbulence over Thumba
Authors: Anandarao, B. G.; Raghavarao, R.; Desai, J. N.; Haerendel, G.
Bibcode: 1978JATP...40..157A
Altcode:
Features of the barium cloud released over Thumba, India at an altitude
of 93 km are reported. The initial cloud form, two rings joined by a
knot, was distorted by a north-south wind shear and a vertical wind
gradient so that the rings became elongated loops. The upper loop was
unaffected by turbulence during the 10 minutes of observation, while 280
sec elapsed before the development of turbulence occurred in the lower
loop. This finding could be evidence for the coexistence of turbulent
and nonturbulent regions in the 93-95 km altitude range. Vertical
velocities for the cloud as well as for other barium clouds released at
lower altitudes indicate a profile which suggests the presence of an
internal atmospheric gravity wave. The possibility is considered that
gradients in the vertical wind could lower the turbopause level, found
to be 95 + or - 2 km, about 10 km lower than the level observed earlier.
Title: Microscopic plasma processes related to reconnection
Authors: Haerendel, G.
Bibcode: 1976STIN...7733011H
Altcode:
First, estimates for the thickness of the Chapman-Ferraro current layer,
delta, and the diffusion coefficient, D, resulting from current-driven
anomalous resistivity were derived. The basis of the estimate is a
drift velocity of ions and electrons above the instability threshold
and a maximum possible merging rate. 1.2 km < delta < 20 km and
0.9 X 10 to the 12th power sq cm/sec < D < 1.5 X 10 to the 13th
power sq cm/sec were found. Specific processes which may apply are
ion acoustic and electron-cyclotron turbulence. Nonlinear saturation
levels of these processes yield D approximately 10 to the 12th power sq
cm/sec, in agreement with the first estimate, and predict narrow current
sheets with widths only slightly above the electron inertial length
c/omegape. The role of MHD instabilities in this context
is briefly touched. In the second part, evidence for eddy convection
in the polar cusp region and its possible consequences for the mass
transport into the magnetosphere and for merging are discussed. It is
suggested that reconnection is not a laminar flow process occurring
mainly at the nose of the magnetosphere as in the classical picture,
but that it is rather a by-product of eddy convection in the polar
cusps. The eddy diffusion coefficient derived from observations was
estimated to be Deddy approximately 5 X 10 to the 14th
power sq cm/sec. Several microscopic processes that could account
for viscous dissipation of the eddies and reconnection are briefly
discussed. The latter process would have spatial scales of several
1000 km and would be highly fluctuating in time with a typical period
of a few tens of seconds.
Title: Evidence for a Rayleigh-Taylor type instability and upwelling
of depleted density regions during equatorial spread F
Authors: Kelley, M. C.; Haerendel, G.; Kappler, H.; Valenzuela,
A.; Balsley, B. B.; Carter, D. A.; Ecklund, W. L.; Carlson, C. W.;
Haeusler, B.; Torbert, R.
Bibcode: 1976GeoRL...3..448K
Altcode:
Recent rocket probe, barium cloud and radar measurements conducted
during equatorial spread F conditions are interpreted in terms of a
Rayleigh-Taylor gravitational instability operating on the bottomside
of the F peak. The persistent theoretical problems associated with
strong radar echoes typically observed in patch-like structures at
high altitudes are explained in terms of regions of depleted plasma
density which bouyantly rise against the gravitational field.
Title: Chairman's Report
Authors: Haerendel, G.
Bibcode: 1976ESASP.115..202H
Altcode: 1976epsr.conf..202H
No abstract at ADS
Title: Co-Ordinated Measurements with EISCAT, Sounding Rockets and
Balloons Aimed at Plasma Physical Studies
Authors: Haerendel, G.
Bibcode: 1976ESASP.115..253H
Altcode: 1976epsr.conf..253H
No abstract at ADS
Title: Plasma and Magnetic Field Characteristics of the Distant
Polar Cusp near Local Noon: The Entry Layer
Authors: Paschmann, G.; Haerendel, G.; Sckopke, N.; Rosenbauer, H.;
Hedgecock, P. C.
Bibcode: 1976JGR....81.2883P
Altcode:
Heos 2 plasma and magnetic field measurements in the distant polar
cusp region reveal the existence of a plasma layer on day side field
lines just inside the magnetopause. Density and temperature in this
layer are nearly the same as they are in the adjacent magnetosheath,
but the flow lacks the order existing both in the magnetosheath and
in the plasma mantle. Flow directions toward and away from the sun
but, in general, parallel to the field lines have been found. The
magnetopause (as defined by a sudden rotation of the magnetic field
vector) mostly coincides with the transition to ordered magnetosheath
flow. The inner boundary of the layer is located just within the outer
boundary of the hot ring current plasma. In the region of overlap the
hot electrons have the signature of trapped particles, though often
at reduced intensity. The magnetic field is strongly fluctuating in
magnitude, while its orientation is more stable, consistent with a
connection to the earth, but is systematically distorted out of the
meridian plane. The layer is thought to be a consequence of the entry
of magnetosheath plasma, which does not appear to be unobstructed,
as has been claimed in the concept of a magnetospheric cleft. The
magnetopause has a cusplike indentation which is elongated in local
time. The existence of field-aligned currents (total strength ≈
106 A) and their location of flow in the inner part of the
‘entry layer’ (into the ionosphere before noon and out of it after
noon) are inferred from the systematic bending of field lines. It is
proposed that the dynamo of the related current system is provided by
the transfer of perpendicular momentum resulting from the plasma entry
into the layer. The essential features of the entry layer might be
compatible with the model of plasma flow through the magnetopause of
Levy et al. (1964) if a ‘dam’ effect caused by the cusp geometry
were added.
Title: Status and results of the altitude rocket program
Authors: Haerendel, G.
Bibcode: 1975dglr.meetR....H
Altcode:
Two significant advantages of a use of altitude rockets are related to
comparatively low costs for an individual project and short development
times. The altitude rocket program in West Germany for the period
from 1973 to 1977 is discussed. A number of results of the research
program are considered, taking into account the X-ray emission of the
Crab Nebula, mass spectrometry studies of the D layer, and barium-ion
experiments in the polar cusp. Attention is also given to the present
status of development of the Aries rocket and a proposal for Aries
rocket applications.
Title: Electric field measurements in a major magnetospheric substorm
Authors: Kelley, M. C.; Haerendel, G.; Kappler, H.; Mozer, F. S.;
Fahleson, U. V.
Bibcode: 1975JGR....80.3181K
Altcode:
A Black Brant VB sounding rocket was launched at 03h 56m 05s UT on
August 17, 1970, into the expansion phase of a major magnetospheric
substorm during which the perturbation magnetic field was in excess of
2000 γ at ground level. Measurements of the electric field component
perpendicular to the earth's magnetic field made by double-probe
detectors on board the rocket and by observation of the motion of two
barium ion clouds released from the same rocket were in excellent
agreement. The rocket remained within a region of intense particle
precipitation where the field was 15°-45° south of geomagnetic
west with a magnitude between 60 mV/m and 90 mV/m. The barium clouds
drifted southeast into a region of weak aurora and smaller electric
field. These measurements show that the electric field is not always
smallest inside auroral arcs and that the poleward auroral expansion
phase is not accompanied by poleward ionospheric plasma motion
and suggest a divergence of the northward perpendicular ionospheric
current and hence that a downward field-aligned current was present in
the equatorward portion of the arc structure. During a portion of the
flight the double-probe detectors also measured a parallel component of
electric field between 10 and 24 mV/m which pointed downward toward the
earth. The total electric field detected on board the rocket was deduced
by two techniques: one technique which does not involve assumptions
involving dc offsets of the detector but relies on the precessional
motion of the rocket to separate E⊥ and E∥
and one high time resolution technique which involves an assumption that
these offsets approach a constant value in the flight. The same basic
conclusions were deduced from both techniques. When the possibility of
current-driven anomalous resistivity due to ion acoustic waves is taken
into account, the measurements are in agreement with a slow parallel
motion of ambient plasma ions (<10 m/s). However, when the theory is
applied to a two-component plasma, the heavier, lower-density species
should be accelerated to speeds much in excess of the observed values
for the barium ions. Thus the low parallel barium ion velocity which was
observed is not in agreement with an ion acoustic wave explanation for
the observed parallel electric field. Although the evidence is strong
that a parallel component of electric field was detected, one cannot
rule out the possibility that this field-aligned potential difference
was created by the motion of the vehicle through the medium.
Title: Entry of Solar Wind Plasma into the Magnetosphere
Authors: Haerendel, G.; Paschmann, G.
Bibcode: 1975phpm.symp...23H
Altcode: 1975phpm.proc...23H
Measurements conducted by the Heos satellite in the distant polar cusp
region are considered, taking into account instrumentation, a plasma
layer inside the dayside magnetopause, the magnetic field and plasma
flow at the magnetopause, and the shape of the magnetopause. Attention
is given to the formation of the entry layer and the currents and
convection in the polar cusp region.
Title: Eine Möglichkeit der Trennung von ionosphärischem und
magnetosphärischem Anteil an den Magnetfeldstörungen in Südindien
Authors: Papamastorakis, J.; Haerendel, G.
Bibcode: 1974MitAG..35R.225P
Altcode:
No abstract at ADS
Title: Eine Plasmainstabilität von Scherströmungen als Ursache
von Nordlichtstrahlen
Authors: Haerendel, G.
Bibcode: 1974MitAG..35..217H
Altcode:
No abstract at ADS
Title: Die Spur der Magnetopause in der Magnetosphäre
Authors: Haerendel, G.
Bibcode: 1974MitAG..35..165H
Altcode:
No abstract at ADS
Title: Project `PORCUPINE': a Step Towards Understanding the Aurora
Authors: Haerendel, G.; Klett, R.
Bibcode: 1974esrs.conf..295H
Altcode:
No abstract at ADS
Title: Thermospheric observations combining chemical seeding and
ground-based techniques - II. Ionospheric drifts and the Sq current
system
Authors: Rees, D.; Haerendel, G.; Felgate, D. G.; Lloyd, K. H.; Low,
C. H.
Bibcode: 1973P&SS...21.1237R
Altcode:
Two Skylark sounding rockets carrying chemical seeding payloads were
launched from Woomera, South Australia in October 1969. In conjunction
with these firings, the F-region drifts were determined with the
Buckland Park aerial array and the results compared with the observed
motion of the barium ion clouds. The local ionospheric Sq current
system was calculated both from the observed ionospheric parameters
and from ground-based magnetograms and the differences between the
two results are discussed.
Title: Numerical modeling of the drift and deformation of ionospheric
plasma clouds and of their interaction with other layers of the
ionosphere
Authors: Lloyd, K. H.; Haerendel, G.
Bibcode: 1973JGR....78.7389L
Altcode:
The equations of ion motion and of the electric potential, which
describe the behavior of a plasma cloud in the ionosphere, are solved by
numerical methods, the real ionosphere being approximated by a layered
model. It is found that the dominant physical processes depend on the
ionospheric region into which the cloud is released. In the E layer
the main process is a continuous exchange of the ions constituting
the perturbation, which results in the original cloud ions becoming
imbedded in the ionosphere and drifting with it. The perturbation
thereby moves like a wave through the ionosphere. In the F region
the exchange process is very slow, and distortion of the cloud by
self-generated electric polarization fields becomes the dominant
effect. A comparison of the computed distortion with observations on
barium plasma clouds suggests that electrostatic coupling between the
E and F layers, over the scale size of the ion clouds, is usually not
very efficient. The effects of an altitude dependent neutral gas wind
and of ionospheric recombination processes have been examined. The
altitude dependent neutral gas wind produces profound distortion in the
cloud, but the ionospheric recombination processes appear to have no
important quantitative effect. If small perturbations are introduced
into the initial cloud distribution, they develop into fingers that
closely resemble the observed striations in barium ion clouds. In
the E region the perturbations are shed from the ion cloud into the
ionospheric positive image cloud.
Title: Results from barium cloud release in the ionosphere and
magnetosphere.
Authors: Haerendel, G.
Bibcode: 1973spre.conf..601H
Altcode: 1973spre....2..601H
No abstract at ADS
Title: Investigation of mid-latitude ionospheric currents by combined
rocket techniques.
Authors: Rees, D.; Aggson, T. L.; Burrows, K.; Haerendel, G.; Rieger,
E.; Lloyd, K. H.; Wilson, J. W. G.; Dorling, E. B.; Wrenn, G. L.
Bibcode: 1973spre.conf..449R
Altcode: 1973spre....1..449R
No abstract at ADS
Title: Coordinated observations of the magnetosphere: The development
of a substorm
Authors: Mende, S. B.; Sharp, R. D.; Shelley, E. G.; Haerendel, G.;
Hones, E. W.
Bibcode: 1972JGR....77.4682M
Altcode:
Coordinated observations of a substorm are reported by using data from
all-sky camera (ASCA) stations near the northern conjugate of the ATS 5
geostationary satellite, plasma and magnetic-field experiments on the
ATS 5 satellite, Vela 5B at 18 RE in the magnetotail, the
Heos 1 interplanetary probe, and ground-based magnetograms. The substorm
event occurred after a very quiet day and was preceded by a development
period during which the interplanetary field turned southward and the
plasma energy density increased near the earth (6.6 RE)
on the nightside. This period was also evidenced by a depression of
the midlatitude H component of the geomagnetic field at the earth's
surface. The auroral breakup was preceded by the appearance of quiet
arcs, the leveling off of the plasma energy density increase at ATS, and
the disappearance of the tail plasma at 18 RE. The onset of
the expansive phase was evidenced by brightening and subsequent breakup
of the auroral arcs, the development of a westward-traveling surge,
an increase in the fluxes of energetic electrons, and the increase of
the magnetic field at ATS 5. The ground-based magnetograms show the
sudden intensification of the westward electrojet and the appearance
of field-aligned currents.
Title: Electric fields and their effects in the ionosphere (Summary
of observations).
Authors: Haerendel, G.
Bibcode: 1972upat.conf...87H
Altcode:
No abstract at ADS
Title: Plasma Drifts in the Auroral Ionosphere Derived from Barium
Releases
Authors: Haerendel, G.
Bibcode: 1972ASSL...32..246H
Altcode: 1972emp..conf..246H
No abstract at ADS
Title: Ambipolar diffusion along magnetic field lines in the presence
of an electric current
Authors: Scholer, M.; Haerendel, G.
Bibcode: 1971P&SS...19..915S
Altcode:
The one-dimensional ambipolar diffusion parallel to the magnetic field
is treated for the case of a plasma cloud imbedded in a weakly ionized
gas with a homogeneous magnetic field. We distinguish between cloud ions
and background ions. A constant electric current is allowed to flow from
infinity through the cloud. The resulting coupled diffusion equations
for cloud and background ions are solved numerically. The initial
phase is characterized by distortions of the density distributions
of the ions owing to electric polarization fields which are the more
pronounced the higher the contribution from the test ions is. The peak
of the test ion distribution will finally move in the direction of the
electric current. Situations in the F-region of the ionosphere where
these effects become appreciable are liable to be affected by plasma
turbulence and anomalous resistivity.
Title: Physical Processes Involving Striation Formation in Barium
Clouds
Authors: Völk, H.; Haerendel, G.
Bibcode: 1971ASSL...24..394V
Altcode: 1971raat.conf..394V
No abstract at ADS
Title: Striations in ionospheric ion clouds, 1
Authors: Völk, Heinrich J.; Haerendel, Gerhard
Bibcode: 1971JGR....76.4541V
Altcode:
We discuss the occurrence of striated irregularities in ionospheric ion
clouds. Striations can either be impressed on the cloud from the ambient
medium or generated by the cloud itself. If they are impressed on the
cloud, the Striations are simply tracers of small-scale electric fields
in their environment. To ascertain whether this is indeed the case,
we investigate the stability of the cloud. It is pointed out that the
cloud cannot be considered an isolated object and that its interaction
with the ionosphere is essential if we consider striation formation
by the cloud itself. In this part 1, the short-circuiting effect on
cloud-generated polarization fields is considered in detail. The effect
of the simultaneously generated image Striations is discussed for a
homogeneous ionosphere. This effect is very strong, but for its final
evaluation one needs a more realistic model of the ionosphere. This
treatment will be the subject of part 2.
Title: On the Balance Between Radial and Pitch Angle Diffusion
Authors: Haerendel, Gerhard
Bibcode: 1970ASSL...17..416H
Altcode: 1970pfm..conf..416H
No abstract at ADS
Title: Electric Fields in the Ionosphere and Magnetosphere
Authors: Haerendel, G.; Lüst, R.
Bibcode: 1970ASSL...17..213H
Altcode: 1970pfm..conf..213H
No abstract at ADS
Title: Striations in ionospheric ion clouds. Part I.
Authors: Völk, H. J.; Haerendel, G.
Bibcode: 1970MPIM...50.....V
Altcode:
No abstract at ADS
Title: High altitude releases of barium vapour using a rubis rocket.
Authors: Rieger, E.; Neuss, H.; Lüst, R.; Meyer, B.; Haser, L.;
Loidl, H.; Stöcker, J.; Haerendel, G.
Bibcode: 1970AnG....26..845R
Altcode:
No abstract at ADS
Title: Magnetospheric Electric Fields
Authors: Völk, H.; Haerendel, G.
Bibcode: 1970iso..conf..280V
Altcode:
No abstract at ADS
Title: Messung elektrischer Felder in der Ionosphäre mit künstlichen
Plasmawolken
Authors: Haerendel, Gerhard
Bibcode: 1969NW.....56..545H
Altcode:
No abstract at ADS
Title: Highly irregular artificial plasma clouds in the auroral zone.
Authors: Haerendel, G.; Lüst, R.; Rieger, E.; Völk, H.
Bibcode: 1969MPIM...21.....H
Altcode:
No abstract at ADS
Title: Electric Fields in the Upper Atmosphere
Authors: Haerendel, G.; Lüst, R.
Bibcode: 1968epf..conf..271H
Altcode:
No abstract at ADS
Title: Diffusion Theory of Trapped Particles and the Observed Proton
Distribution
Authors: Haerendel, G.
Bibcode: 1968epf..conf..171H
Altcode:
No abstract at ADS
Title: Artificial strontium and barium clouds in the upper atmosphere
Authors: Föppl, H.; Haerendel, G.; Haser, L.; Loidl, J.; Lütjens,
P.; Lüst, R.; Melzner, F.; Meyer, B.; Neuss, H.; Rieger, E.
Bibcode: 1967P&SS...15..357F
Altcode:
Experiments with strontium and barium vapour releases in the upper
atmosphere, carried out in the Sahara and in Sardinia in 1964,
are discussed. (1) The yield of evaporated metal was tested for
different chemical reactions. Sr proved to have efficiencies up to 40
per cent. For Ba a mixture of CuO and Ba gave the best results with
a yield of nearly 7 per cent. (2) No Sr ions were observed in the
experiments. Barium, however, is strongly ionized. The ionization
proceeds in two different steps: during the initial phase with a
characteristic time of about 5 sec and by a slower photoionization
process with a characteristic time of about 100 sec. (3) The diameter of
the neutral clouds increased as one would expect for purely molecular
diffusion. (4) The rate of increase in the central intensity of the
clouds at sunrise was greater than the rate of decrease at sunset. (5)
Atmospheric wind velocities of 50-130 msec-1 were determined
from the motion of the neutral clouds. The motion of the ion clouds
perpendicular to the Earth's magnetic field in- dicated the presence
of electric fields. (6) The initial expansion velocity for explosive
mixtures was greater by about a factor of four than the mean thermal
velocity of the atoms at a temperature of about 3000°K.
Title: Motion of artificial ion clouds in the upper atmosphere
Authors: Haerendel, G.; Lüst, R.; Rieger, E.
Bibcode: 1967P&SS...15....1H
Altcode:
The paper sets out to solve the equations of motion for an ionized
irregularity of finite length, and to apply it to the behaviour of a
Ba + cloud. After a number of simplifying assumptions, an
expression for the ionospheric electric field is derived in terms of
(1) the magnetic field, (2) the velocities of the neutral and ionized
clouds, (3) λ* (the ratio of the integrated Pedersen conductivities
in the cloud and in the atmosphere), (4) ki (= gyrofrequency
for Ba +/collision frequency). The magnitude and orientation
of the electric field is evaluated from the observation of six barium
and strontium clouds. λ* is assumed to be unity. The derived field
strengths lie between 1 and 3. 10 -3 V/in. In the evening
the fields are pointing southward and in the early morning release
northward.
Title: Preliminary experiments for the study of the interplanetary
medium by the release of metal vapour in the upper atmosphere
Authors: Föppl, H.; Haerendel, G.; Loidl, J.; Lüst, R.; Melzner,
F.; Meyer, B.; Neuss, H.; Rieger, E.
Bibcode: 1965P&SS...13...95F
Altcode:
It has been proposed to create an artificial ion cloud in interplanetary
space for studying the state of the interplanetary medium. New
data concerning excitation and ionization by sunlight are given in
section 2 for the alkali-earth metals Ca, Sr, Ba and for the rare
earth Eu which could be used for such an ion cloud. In section
3 the expansion of the artificial cloud in interplanetary space,
the interaction of the ion cloud with the interplanetary medium and
the minimum masses required are estimated. The results are stated
in Table 3. In section 4 the methods used for the vaporization of
the metals are discussed. Different chemical reactions which might
have occurred, are summarized in Table 4. So far seven different
experiments have been carried out with sounding rockets in the Sahara
and in Sardinia. In these experiments metal vapour was released in
the upper atmosphere. These experiments are listed in Table 5. In
section 5 the results of the sounding rocket experiments of May 1963
are discussed since the data for the later experiments are not yet
reduced. The main results for the physical properties of the observed
clouds and of the upper atmosphere at a height of about 125 km are:
(1) The initial radius of the cloud was 0.25 km. (2) The velocity
of the wind changed during the period of observation (15 min) from
55 msec -1 to 90 msec -1. (3) A wind shear
of about 1 msec -1/km apparently exists there. (4) The
diameter of the cloud increased faster than one would expect from
purely molecular diffusion. (5) The neutral Sr-cloud changed from
the optically thick to the optically thin case. (6) About 4 per cent
of the Sr which was present only as impurity came out in the form of
free atoms, as compared with 0.01 per cent of the Ba. (7) The released
material is removed by reactions with the atmosphere in a time scale
of the order of 10 3 sec. In the experiments carried out in
February 1964 the Al used in the chemical reactions had been replaced
by Mg. This led to the production of Sr-clouds which were optically
thick during the entire period of observation and about 30 per cent
or more Sr came out in the form of free atoms.
Title: Corrigendum
Authors: Haerendel, G.
Bibcode: 1962JGR....67.1697H
Altcode:
No abstract at ADS
Title: A Possible Correction to the Spectrum of Geomagnetically
Trapped Protons
Authors: Haerendel, G.
Bibcode: 1962JGR....67.1173H
Altcode:
No abstract at ADS