Theory of imperfect magnetosphere-ionosphere coupling

International Nuclear Information System (INIS)

Kan, J.R.; Lee, L.C.

1980-01-01

Atheory of magnetosphere-ionosphere coupling in the presence of field-aligned potential drops is formulated within the framework of magnetohydrodynamic equations. Our formulation allows the magnetosphere as well as the ionosphere to respond self-consistently to the parallel potential drop along auroral field lines. Equipotential contours are distorted into a V-shaped structure near the convection reversal boundary and S-shaped on the equatorward side, each gives rise to an inverted V precipitation band. The loading effect of the imperfect coupling results in a valley in the electric field profile which occurs equatorward of the convection reversal boundary

Modeling the ionosphere-thermosphere response to a geomagnetic storm using physics-based magnetospheric energy input: OpenGGCM-CTIM results

Directory of Open Access Journals (Sweden)

Connor Hyunju Kim

2016-01-01

Full Text Available The magnetosphere is a major source of energy for the Earth’s ionosphere and thermosphere (IT system. Current IT models drive the upper atmosphere using empirically calculated magnetospheric energy input. Thus, they do not sufficiently capture the storm-time dynamics, particularly at high latitudes. To improve the prediction capability of IT models, a physics-based magnetospheric input is necessary. Here, we use the Open Global General Circulation Model (OpenGGCM coupled with the Coupled Thermosphere Ionosphere Model (CTIM. OpenGGCM calculates a three-dimensional global magnetosphere and a two-dimensional high-latitude ionosphere by solving resistive magnetohydrodynamic (MHD equations with solar wind input. CTIM calculates a global thermosphere and a high-latitude ionosphere in three dimensions using realistic magnetospheric inputs from the OpenGGCM. We investigate whether the coupled model improves the storm-time IT responses by simulating a geomagnetic storm that is preceded by a strong solar wind pressure front on August 24, 2005. We compare the OpenGGCM-CTIM results with low-earth-orbit satellite observations and with the model results of Coupled Thermosphere-Ionosphere-Plasmasphere electrodynamics (CTIPe. CTIPe is an up-to-date version of CTIM that incorporates more IT dynamics such as a low-latitude ionosphere and a plasmasphere, but uses empirical magnetospheric input. OpenGGCM-CTIM reproduces localized neutral density peaks at ~ 400 km altitude in the high-latitude dayside regions in agreement with in situ observations during the pressure shock and the early phase of the storm. Although CTIPe is in some sense a much superior model than CTIM, it misses these localized enhancements. Unlike the CTIPe empirical input models, OpenGGCM-CTIM more faithfully produces localized increases of both auroral precipitation and ionospheric electric fields near the high-latitude dayside region after the pressure shock and after the storm onset

A statistical approach for identifying the ionospheric footprint of magnetospheric boundaries from SuperDARN observations

Directory of Open Access Journals (Sweden)

G. Lointier

2008-02-01

Full Text Available Identifying and tracking the projection of magnetospheric regions on the high-latitude ionosphere is of primary importance for studying the Solar Wind-Magnetosphere-Ionosphere system and for space weather applications. By its unique spatial coverage and temporal resolution, the Super Dual Auroral Radar Network (SuperDARN provides key parameters, such as the Doppler spectral width, which allows the monitoring of the ionospheric footprint of some magnetospheric boundaries in near real-time. In this study, we present the first results of a statistical approach for monitoring these magnetospheric boundaries. The singular value decomposition is used as a data reduction tool to describe the backscattered echoes with a small set of parameters. One of these is strongly correlated with the Doppler spectral width, and can thus be used as a proxy for it. Based on this, we propose a Bayesian classifier for identifying the spectral width boundary, which is classically associated with the Polar Cap boundary. The results are in good agreement with previous studies. Two advantages of the method are: the possibility to apply it in near real-time, and its capacity to select the appropriate threshold level for the boundary detection.

Effects of a solar wind dynamic pressure increase in the magnetosphere and in the ionosphere

Directory of Open Access Journals (Sweden)

L. Juusola

2010-10-01

Full Text Available On 17 July 2005, an earthward bound north-south oriented magnetic cloud and its sheath were observed by the ACE, SoHO, and Wind solar wind monitors. A steplike increase of the solar wind dynamic pressure during northward interplanetary magnetic field conditions was related to the leading edge of the sheath. A timing analysis between the three spacecraft revealed that this front was not aligned with the GSE y-axis, but had a normal (−0.58,0.82,0. Hence, the first contact with the magnetosphere occurred on the dawnside rather than at the subsolar point. Fortunately, Cluster, Double Star 1, and Geotail happened to be distributed close to the magnetopause in this region, which made it possible to closely monitor the motion of the magnetopause. After the pressure front had impacted the magnetosphere, the magnetopause was perceived first to move inward and then immediately to correct the overshoot by slightly expanding again such that it ended up between the Cluster constellation with Double Star 1 inside the magnetosphere and Geotail in the magnetosheath. Coinciding with the inward and subsequent outward motion, the ground-based magnetic field at low latitudes was observed to first strengthen and then weaken. As the magnetopause position stabilised, so did the ground-based magnetic field intensity, settling at a level slightly higher than before the pressure increase. Altogether the magnetopause was moving for about 15 min after its first contact with the front. The high latitude ionospheric signature consisted of two parts: a shorter (few minutes and less intense preliminary part comprised a decrease of AL and a negative variation of PC. A longer (about ten minutes and more intense main part of the signature comprised an increase of AU and a positive variation of PC. Measurements from several ground-based magnetometer networks (210 MM CPMN, CANMOS, CARISMA, GIMA, IMAGE, MACCS, SuperMAG, THEMIS, TGO were used to obtain information on the

Mission Concept to Connect Magnetospheric Physical Processes to Ionospheric Phenomena

Science.gov (United States)

Dors, E. E.; MacDonald, E.; Kepko, L.; Borovsky, J.; Reeves, G. D.; Delzanno, G. L.; Thomsen, M. F.; Sanchez, E. R.; Henderson, M. G.; Nguyen, D. C.; Vaith, H.; Gilchrist, B. E.; Spanswick, E.; Marshall, R. A.; Donovan, E.; Neilson, J.; Carlsten, B. E.

2017-12-01

On the Earth's nightside the magnetic connections between the ionosphere and the dynamic magnetosphere have a great deal of uncertainty: this uncertainty prevents us from scientifically understanding what physical processes in the magnetosphere are driving the various phenomena in the ionosphere. Since the 1990s, the space plasma physics group at Los Alamos National Laboratory has been working on a concept to connect magnetospheric physical processes to auroral phenomena in the ionosphere by firing an electron beam from a magnetospheric spacecraft and optically imaging the beam spot in the ionosphere. The magnetospheric spacecraft will carry a steerable electron accelerator, a power-storage system, a plasma contactor, and instruments to measure magnetic and electric fields, plasma, and energetic particles. The spacecraft orbit will be coordinated with a ground-based network of cameras to (a) locate the electron beam spot in the upper atmosphere and (b) monitor the aurora. An overview of the mission concept will be presented, including recent enabling advancements based on (1) a new understanding of the dynamic spacecraft charging of the accelerator and plasma-contactor system in the tenuous magnetosphere based on ion emission rather than electron collection, (2) a new understanding of the propagation properties of pulsed MeV-class beams in the magnetosphere, and (3) the design of a compact high-power 1-MeV electron accelerator and power-storage system. This strategy to (a) determine the magnetosphere-to-ionosphere connections and (b) reduce accelerator- platform charging responds to one of the six emerging-technology needs called out in the most-recent National Academies Decadal Survey for Solar and Space Physics. [LA-UR-17-23614

Solar wind and seasonal influence on ionospheric currents from Swarm and CHAMP measurements

DEFF Research Database (Denmark)

Laundal, K. M.; Finlay, C. C.; Olsen, N.

2018-01-01

the ionosphere with the magnetosphere. The model provides ionospheric current values at any location as continuous functions of solar wind speed, interplanetary magnetic field (IMF), dipole tilt angle, and the F10.7 index of solar flux. Geometric distortions due to variations in the Earth's main magnetic field...

Dayside magnetospheric and ionospheric responses to a foreshock transient on June 25, 2008: 2. 2-D evolution based on dayside auroral imaging

OpenAIRE

Wang, Boyi; Nishimura, Yukitoshi; Hietala, Heli; Shen, Xiao-Chen; Shi, Quanqi; Zhang, Hui; Lyons, Larry; Zou, Ying; Angelopoulos, Vassilis; Ebihara, Yusuke; Weatherwax, Allan

2018-01-01

The foreshock region involves localized and transient structures such as foreshock cavities and hot flow anomalies due to solar wind-bow shock interactions, and foreshock transients have been shown to lead to magnetospheric and ionospheric responses. In this paper, the interaction between a foreshock transient and the magnetosphere-ionosphere system is investigated using dayside aurora imagers revealing structures and propagation in greater detail than previously possible. A foreshock transie...

System of ionospheric currents excited by a magnetospheric generator in the boundary layer

International Nuclear Information System (INIS)

Denisenko, V.V.; Zamaj, S.S.; Kitaev, A.V.; Matveenkov, I.T.; Pivovarov, V.G.

1992-01-01

A model of ionospheric electric fields and currents in the vicinity of the daytime cusp is proposed; the fields and currents occur due to diffusion mechanism of electric field generation at the boundary of Earth's magnetosphere. The results of calculating electric fields and currents are presented for various values of magnetic field components in the solar wind

Different magnetospheric modes: solar wind driving and coupling efficiency

Directory of Open Access Journals (Sweden)

N. Partamies

2009-11-01

Full Text Available This study describes a systematic statistical comparison of isolated non-storm substorms, steady magnetospheric convection (SMC intervals and sawtooth events. The number of events is approximately the same in each group and the data are taken from about the same years to avoid biasing by different solar cycle phase. The very same superposed epoch analysis is performed for each event group to show the characteristics of ground-based indices (AL, PCN, PC potential, particle injection at the geostationary orbit and the solar wind and IMF parameters. We show that the monthly occurrence of sawtooth events and isolated non-stormtime substorms closely follows maxima of the geomagnetic activity at (or close to the equinoxes. The most strongly solar wind driven event type, sawtooth events, is the least efficient in coupling the solar wind energy to the auroral ionosphere, while SMC periods are associated with the highest coupling ratio (AL/EY. Furthermore, solar wind speed seems to play a key role in determining the type of activity in the magnetosphere. Slow solar wind is capable of maintaining steady convection. During fast solar wind streams the magnetosphere responds with loading–unloading cycles, represented by substorms during moderately active conditions and sawtooth events (or other storm-time activations during geomagnetically active conditions.

Solar wind dynamic pressure variations and transient magnetospheric signatures

International Nuclear Information System (INIS)

Sibeck, D.G.; Baumjohann, W.

1989-01-01

Contrary to the prevailing popular view, we find some transient ground events with bipolar north-south signatures are related to variations in solar wind dynamic pressure and not necessarily to magnetic merging. We present simultaneous solar wind plasma observations for two previously reported transient ground events observed at dayside auroral latitudes. During the first event, originally reported by Lanzerotti et al. [1987], conjugate ground magnetometers recorded north-south magetic field deflections in the east-west and vertical directions. The second event was reported by Todd et al. [1986], we noted ground rader observations indicating strong northward then southward ionospheric flows. The events were associated with the postulated signatures of patchy, sporadic, merging of magnetosheath and magnetospheric magnetic field lines at the dayside magnetospause, known as flux transfer events. Conversely, we demonstrate that the event reported by Lanzerotti et al. was accompanied by a sharp increase in solar wind dynamic pressure, a magnetospheric compression, and a consequent ringing of the magnetospheric magnetic field. The event reported by Todd et al. was associated with a brief but sharp increase in the solar wind dynamic pressure. copyright American Geophysical Union 1989

The Response of the Thermosphere and Ionosphere to Magnetospheric Forcing

Science.gov (United States)

Rees, D.; Fuller-Rowell, T. J.

1989-06-01

During the past six years, rapid advances in three observational techniques (ground-based radars, optical interferometers and satellite-borne instruments) have provided a means of observing a wide range of spectacular interactions between the coupled magnetosphere, ionosphere and thermosphere system. Perhaps the most fundamental gain has come from the combined data-sets from the NASA Dynamics Explorer (DE) Satellites. These have unambiguously described the global nature of thermospheric flows, and their response to magnetospheric forcing. The DE spacecraft have also described, at the same time, the magnetospheric particle precipitation and convective electric fields which force the polar thermosphere and ionosphere. The response of the thermosphere to magnetospheric forcing is far more complex than merely the rare excitation of 1 km s-1 wind speeds and strong heating; the heating causes large-scale convection and advection within the thermosphere. These large winds grossly change the compositional structure of the upper thermosphere at high and middle latitudes during major geomagnetic disturbances. Some of the major seasonal and geomagnetic storm-related anomalies of the ionosphere are directly attributable to the gross wind-induced changes of thermospheric composition; the mid-latitude ionospheric storm `negative phase', however, is yet to be fully understood. The combination of very strong polar wind velocities and rapid plasma convection forced by magnetospheric electric fields strongly and rapidly modify F-region plasma distributions generated by the combination of local solar and auroral ionization sources. Until recently, however, it has been difficult to interpret the observed complex spatial and time-dependent structures and motions of the thermosphere and ionosphere because of their strong and nonlinear coupling. It has recently been possible to complete a numerical and computational merging of the University College London (UCL) global thermospheric

Wave--particle interactions in the magnetosphere and ionosphere

International Nuclear Information System (INIS)

Thorne, R.M.

1975-01-01

Two distinct aspects of the interaction between waves and particles in the earth's magnetosphere and ionosphere were discussed at the Yosemite Conference on Magnetosphere-Ionosphere Coupling; these will be briefly reviewed. Intense field-aligned currents flow between the ionosphere and magnetosphere at auroral latitudes. Under certain conditions these currents can become unstable, permitting potential drops to be established along the field lines. The present status of experimental evidence favoring such parallel electric fields is somewhat controversial. Theoretical models for their origin invoke regions of anomalous resistivity or electrostatic double layers. To date it is impossible to distinguish between these alternatives on the basis of experimental data. The nonadiabatic behavior of magnetospheric ring current particles during geomagnetic storms is largely controlled by wave-particle processes. During the storm main phase, intense fluctuating convection electric fields are responsible for injecting trapped particles into the outer radiation zone. The outer radiation zone also moves in closer to the earth following the storm time compression of the plasmapause. Simultaneous pitch angle scattering by higher-frequency plasma turbulence causes precipitation loss near the strong diffusion limit throughout the outer magnetosphere. During the storm recov []ry phase the plasmapause slowly moves out toward its prestorm location; energetic particle loss at such times appears to be dominated by cyclotron resonant scattering from electromagnetic turbulence. (auth)

Magnetosphere-ionosphere coupling currents in Jupiter's middle magnetosphere: effect of magnetosphere-ionosphere decoupling by field-aligned auroral voltages

Directory of Open Access Journals (Sweden)

J. D. Nichols

2005-03-01

Full Text Available We consider the effect of field-aligned voltages on the magnetosphere-ionosphere coupling current system associated with the breakdown of rigid corotation of equatorial plasma in Jupiter's middle magnetosphere. Previous analyses have assumed perfect mapping of the electric field and flow along equipotential field lines between the equatorial plane and the ionosphere, whereas it has been shown that substantial field-aligned voltages must exist to drive the field-aligned currents associated with the main auroral oval. The effect of these field-aligned voltages is to decouple the flow of the equatorial and ionospheric plasma, such that their angular velocities are in general different from each other. In this paper we self-consistently include the field-aligned voltages in computing the plasma flows and currents in the system. A third order differential equation is derived for the ionospheric plasma angular velocity, and a power series solution obtained which reduces to previous solutions in the limit that the field-aligned voltage is small. Results are obtained to second order in the power series, and are compared to the original zeroth order results with no parallel voltage. We find that for system parameters appropriate to Jupiter the effect of the field-aligned voltages on the solutions is small, thus validating the results of previously-published analyses.

Enhanced ionosphere-magnetosphere data from the DMSP satellites

International Nuclear Information System (INIS)

Rich, F.J.; Hardy, D.A.; Gussenhoven, M.S.

1985-01-01

The satellites of the Defense Meteorological Satellite Program (DMSP) represent a series of low-altitude (835 km) polar-orbiting satellites. Their primary objective is related to the observation of the tropospheric weather with a high-resolution white light and infrared imaging system. It is also possible to make images of auroras. On a daily basis, information about auroras is used to assist various communication systems which are affected by the ionospheric disturbances associated with auroras. In the past few years, there have been several improvements in the ionospheric monitoring instrumentation. Since the high-latitude ionosphere is connected to the magnetosphere, the DMSP data are used to monitor magnetospheric processes. The instrumentation of the DMSP satellites is discussed, taking into account the data provided by them. 7 references

UK review of radio science, 1984-1986. Ionosphere and magnetosphere

International Nuclear Information System (INIS)

Rishbeth, H.; Jones, D.

1986-12-01

The paper contains the United Kingdom (U.K.) review of Radio Science, 1984-1986, covering ionospheric and magnetospheric science. This is the current UK contribution towards an international review published by the International Union of Radio Science (URSI). The UK review is divided into topics prescribed by URSI and covers work that is actually published within the period October 1983 - Sept. 1986, also as prescribed by URSI. The topics discussed in the review include: incoherent and coherent scatter, probing the magnetosphere, plasma instabilities, ionospheric modification, composition, ionization and chemistry and ionospheric dynamics. (U.K.)

Observations of Heavy Ions in the Magnetosphere

Science.gov (United States)

Kistler, L. M.

2017-12-01

There are two sources for the hot ions in the magnetosphere: the solar wind and the ionosphere. The solar wind is predominantly protons, with about 4% He++ and less than 1% other high charge state heavy ions. The ionospheric outflow is also predominantly H+, but can contain a significant fraction of heavy ions including O+, N+, He+, O++, and molecular ions (NO+, N2+, O2+). The ionospheric outflow composition varies significantly both with geomagnetic activity and with solar EUV. The variability in the contribution of the two sources, the variability in the ionospheric source itself, and the transport paths of the different species are all important in determining the ion composition at a given location in the magnetosphere. In addition to the source variations, loss processes within the magnetosphere can be mass dependent, changing the composition. In particular, charge exchange is strongly species dependent, and can lead to heavy ion dominance at some energies in the inner magnetosphere. In this talk we will review the current state of our understanding of the composition of the magnetosphere and the processes that determine it.

An Ionosphere/Magnetosphere Coupling Current System Located in the Gap Between Saturn and its Rings

Science.gov (United States)

Khurana, K. K.; Dougherty, M. K.; Cao, H.; Hunt, G. J.; Provan, G.

2017-12-01

The Grand Finale Orbits of the Cassini spacecraft traversed through Saturn's D ring and brought the spacecraft to within 3000 km of Saturn's cloud tops. The closest approaches (CA) were near the equatorial plane of Saturn and were distributed narrowly around the local noon. The difference field (observations - internal field - magnetospheric ring current field) obtained from the Grand Finale orbits show persistent residual fields centered around the CA which diminish at higher latitudes on field lines that connect to the ring. Modeling of this perturbation in terms of internal harmonics shows that the perturbation is not of internal origin but is produced by external currents that couple the ionosphere to the magnetosphere. The sense of the current system suggests that the southern feet of the field lines in the ionosphere lead their northern footprints. We show that the observed field perturbations are consistent with a meridional Pedersen current whose strength is 1 MA/radian, i.e. comparable in strength to the Planetary-period-oscillation related current systems observed in the auroral zone. We show that the implied Lorentz force in the ionosphere extracts momentum from the faster moving southern ionosphere and passes it on to the northern ionosphere. We discuss several ideas for generating this current system. In particular, we highlight a mechanism that involves shears in the neutral winds in the thermospheric region to generate the observed magnetic field.

Ionosphere-Magnetosphere Energy Interplay in the Regions of Diffuse Aurora

Science.gov (United States)

Khazanov, G. V.; Glocer, A.; Sibeck, D. G.; Tripathi, A. K.; Detweiler, L.G.; Avanov, L. A.; Singhal, R. P.

2016-01-01

Both electron cyclotron harmonic (ECH) waves and whistler mode chorus waves resonate with electrons of the Earths plasma sheet in the energy range from tens of eV to several keV and produce the electron diffuse aurora at ionospheric altitudes. Interaction of these superthermal electrons with the neutral atmosphere leads to the production of secondary electrons (E500600 eV) and, as a result, leads to the activation of lower energy superthermal electron spectra that can escape back to the magnetosphere and contribute to the thermal electron energy deposition processes in the magnetospheric plasma. The ECH and whistler mode chorus waves, however, can also interact with the secondary electrons that are coming from both of the magnetically conjugated ionospheres after they have been produced by initially precipitated high-energy electrons that came from the plasma sheet. After their degradation and subsequent reflection in magnetically conjugate atmospheric regions, both the secondary electrons and the precipitating electrons with high (E600 eV) initial energies will travel back through the loss cone, become trapped in the magnetosphere, and redistribute the energy content of the magnetosphere-ionosphere system. Thus, scattering of the secondary electrons by ECH and whistler mode chorus waves leads to an increase of the fraction of superthermal electron energy deposited into the core magnetospheric plasma.

Electrodynamics of the magnetosphere-ionosphere coupling in the nightside subauroral zone

International Nuclear Information System (INIS)

Streltsov, A.V.; Foster, J.C.

2004-01-01

Results from a numerical study of the oscillations of the electric field measured by the Millstone Hill incoherent scatter radar in the E-layer of the nightside subauroral ionosphere during the geomagnetic storm of May 25, 2000 are presented. The frequencies of these oscillations correspond to the discrete frequencies of geomagnetic pulsations usually attributed to the field line resonances or global cavity modes at a high-latitude auroral zone, but they are well below the fundamental eigenfrequency of the subauroral magnetosphere. It is shown that these oscillations can be interpreted as an ionospheric footprint of the surface Alfven waves generated at the equatorial magnetosphere on a steep transverse gradient in the background plasma density associated with the inner edge of the plasmapause developed during strong geomagnetic storms/substorms. This density gradient together with the ionospheric Pedersen conductivity defines the location and amplitude of the electric field in the E-layer: the amplitude of the field is proportional to the amplitude of the density inhomogeneity and inversely proportional to its scale-size and the ionospheric conductivity. Interaction of the large amplitude perpendicular electric field with the low-conducting ionosphere can cause the ionospheric feedback instability, which leads to the formation of small-scale, intense structures in the electric field and the parallel current density in the subauroral magnetosphere

Modeling magnetospheric plasma; Proceedings of the First Huntsville Workshop on Magnetosphere/Ionosphere Plasma Models, Guntersville, AL, Oct. 14-16, 1987

International Nuclear Information System (INIS)

Moore, T.E.; Waite, J.H. Jr.

1988-01-01

The conference presents papers on the global modeling of magnetospheric plasma processes, the modeling of the midlatitude ionosphere and plasmasphere, the modeling of the auroral zone and boundary layer, the modeling of the polar magnetosphere and ionosphere, and the modeling of the plasma sheet and ring current. Particular attention is given to the kinetic approach in magnetospheric plasma transport modeling, self-consistent neutral point current and fields from single particle dynamics, preliminary statistical survey of plasmaspheric ion properties from observations by DE 1/RIMS, and a model of auroral potential structures based on dynamics explorer plasma data. Other topics include internal shear layers in auroral dynamics, quantitative parameterization of energetic ionospheric ion outflow, and open flux merging in an expanding polarcap model

Spontaneous generation of auroral arcs in a three dimensionally coupled magnetosphere-ionosphere system

International Nuclear Information System (INIS)

Watanabe, Kunihiko; Sato, Tetsuya.

1988-01-01

This paper presents the first full three-dimensional dynamic simulation of auroral arc formation. The magnetospheric and ionospheric dynamics are represented by one-fluid magnetohydrodynamic equations and two-fluid weakly ionized plasma equations, respectively. The feedback coupling between magnetospheric Alfven waves and ionospheric density waves are self-consistently and three-dimensionally solved. Obtained is a spontaneous generation of longitudinally elongated striations of field-aligned currents and ionospheric electron densities, which compare very well with many features of quiet auroral arcs. (author)

Interpretation of observed relations between solar wind characteristics and effects at ionospheric altitudes

International Nuclear Information System (INIS)

Cowley, S.W.H.

1983-01-01

This chapter discusses recent developments and remaining questions concerning the behavior of high latitude ionospheric flows and how they depend on solar wind conditions via magnetospheric coupling to the latter. The magnitude and direction of the interplanetary magnetic field (IMF) is found to be the primary factor. The relationships which have been found between the strength of high-latitude flows and solar wind and IMF conditions, and the inferences which can be drawn therefrom concerning the solar wind-magnetosphere coupling processes which result in convection are examined. The east-west asymmetries in highlatitude flows which are found to be associated with the B /SUB y/ (dawn-dusk) component of the IMF are investigated. Related asymmetries are shown to occur in the magnetosphere at large, and the unity of these effects as arising from one straightforward cause is stressed. Recent work on the ''reversed'' sunward flows which occur at high latitudes in association with strong B /SUB z/ in the IMF is described

Challenges Handling Magnetospheric and Ionospheric Signals in Internal Geomagnetic Field Modelling

DEFF Research Database (Denmark)

Finlay, Chris; Lesur, V.; Thébault, E.

2017-01-01

systems in the ionosphere and magnetosphere. In order to fully exploit magnetic data to probe the physical properties and dynamics of the Earth’s interior, field models with suitable treatments of external sources, and their associated induced signals, are essential. Here we review the methods presently......-by-track analysis to characterize magnetospheric field fluctuations, differences in internal field models that result from alternative treatments of the quiet-time ionospheric field, and challenges associated with rapidly changing, but spatially correlated, magnetic signatures of polar cap current systems. Possible...

MESSENGER: Exploring Mercury's Magnetosphere

Science.gov (United States)

Slavin, James A.

2008-01-01

The MESSENGER mission to Mercury offers our first opportunity to explore this planet's miniature magnetosphere since Mariner 10's brief fly-bys in 1974-5. Mercury's magnetosphere is unique in many respects. The magnetosphere of Mercury is the smallest in the solar system with its magnetic field typically standing off the solar wind only - 1000 to 2000 km above the surface. For this reason there are no closed dri-fi paths for energetic particles and, hence, no radiation belts; the characteristic time scales for wave propagation and convective transport are short possibly coupling kinetic and fluid modes; magnetic reconnection at the dayside magnetopause may erode the subsolar magnetosphere allowing solar wind ions to directly impact the dayside regolith; inductive currents in Mercury's interior should act to modify the solar In addition, Mercury's magnetosphere is the only one with its defining magnetic flux tubes rooted in a planetary regolith as opposed to an atmosphere with a conductive ionosphere. This lack of an ionosphere is thought to be the underlying reason for the brevity of the very intense, but short lived, approx. 1-2 min, substorm-like energetic particle events observed by Mariner 10 in Mercury's magnetic tail. In this seminar, we review what we think we know about Mercury's magnetosphere and describe the MESSENGER science team's strategy for obtaining answers to the outstanding science questions surrounding the interaction of the solar wind with Mercury and its small, but dynamic magnetosphere.

Investigation of the radiation properties of magnetospheric ELF waves induced by modulated ionospheric heating

Science.gov (United States)

Wang, Feng; Ni, Binbin; Zhao, Zhengyu; Zhao, Shufan; Zhao, Guangxin; Wang, Min

2017-05-01

Electromagnetic extremely low frequency (ELF) waves play an important role in modulating the Earth's radiation belt electron dynamics. High-frequency (HF) modulated heating of the ionosphere acts as a viable means to generate artificial ELF waves. The artificial ELF waves can reside in two different plasma regions in geo-space by propagating in the ionosphere and penetrating into the magnetosphere. As a consequence, the entire trajectory of ELF wave propagation should be considered to carefully analyze the wave radiation properties resulting from modulated ionospheric heating. We adopt a model of full wave solution to evaluate the Poynting vector of the ELF radiation field in the ionosphere, which can reflect the propagation characteristics of the radiated ELF waves along the background magnetic field and provide the initial condition of waves for ray tracing in the magnetosphere. The results indicate that the induced ELF wave energy forms a collimated beam and the center of the ELF radiation shifts obviously with respect to the ambient magnetic field with the radiation power inversely proportional to the wave frequency. The intensity of ELF wave radiation also shows a weak correlation with the size of the radiation source or its geographical location. Furthermore, the combination of ELF propagation in the ionosphere and magnetosphere is proposed on basis of the characteristics of the ELF radiation field from the upper ionospheric boundary and ray tracing simulations are implemented to reasonably calculate magnetospheric ray paths of ELF waves induced by modulated ionospheric heating.

A study of the ionospheric signature of ion supply from the ionosphere to the magnetosphere

International Nuclear Information System (INIS)

Loranc, M.A.P.

1988-01-01

Recent studies have demonstrated the importance of the ionosphere as a source of magnetospheric plasma; in particular, the observations of upwelling ions (UWI) by the DE-1 Retarding Ion Mass Spectrometer have illustrated the significance of low-energy ion supply to the magnetosphere. The composition of the UWI implies an ionospheric source, and the Dynamics Explorer dual satellite mission provides an opportunity to search for the ionospheric signature of UWI. Magnetometer data from both satellites are used to determine magnetic conjunctions of the satellites; these conjunctions are searched for correlated observations of UWI and upward flowing thermal ion (UFI) events. Four cases of correlated observations are presented as proof of that the UFI are indeed the ionospheric signature of UWI; it is found from these examples that the event are associated with intense field-aligned currents at both satellites and with anti-sunward convection, enhanced fluxes of low-energy precipitating electrons from the boundary plasma sheet, and upward thermal ion fluxes in excess of 10 9 cm -2 s -1 at DE-2. While USI are primarily a dayside phenomena, UFI are found in all local time sectors sampled by DE-2

Magnetospheric plasma physics

International Nuclear Information System (INIS)

Bingham, R.

1989-09-01

The discovery of the earth's radiation belts in 1957 by Van Allen marked the beginning of what is now known as magnetospheric physics. In this study of plasma physics in the magnetosphere, we shall take the magnetosphere to be that part of the earth's ionized atmosphere which is formed by the interaction of the solar wind with the earth's dipole-like magnetic field. It extends from approximately 100km above the earth's surface where the proton-neutral atom collision frequency is equal to the proton gyrofrequency to about ten earth radii (R E ∼ 6380km) in the sunward direction and to several hundred earth radii in the anti-sunward direction. The collision dominated region is called the ionosphere and is sometimes considered separate from the collisionless plasma region. In the ionosphere ion-neutral collisions are dominant and one may think of the ionosphere as a frictional boundary layer ∼ 1000km thick. Other planets are also considered. (author)

The role of the ionosphere in coupling upstream ULF wave power into the dayside magnetosphere

International Nuclear Information System (INIS)

Engebretson, M.J.; Cahill, L.J. Jr.; Arnoldy, R.L.; Anderson, B.J.; Rosenberg, T.J.; Carpenter, D.L.; Inan, U.S.; Eather, R.H.

1991-01-01

A series of recent studies of Pc 3 magnetic pulsations in the dayside outer magnetosphere has given new insights into the possible mechanisms of entry of ULF wave power into the magnetosphere from a bow shock related upstream source. In this paper, the authors first review many of these new observational results by presenting a comparison of data from two 10-hour intervals on successive days in April 1986 and then present a possible model for transmission of pulsation signals from the magnetosheath into the dayside magnetosphere. Simultaneous multi-instrument observations at South Pole Station, located below the cusp/cleft ionosphere near local noon, magnetic field observations by the AMPTE CCE satellite in the dayside outer magnetosphere, and upstream magnetic field observations by the IMP 8 satellite show clear interplanetary magnetic field field magnitude control of dayside resonant harmonic pulsations and band-limited very high latitude pulsations, as well as pulsation-modulated precipitation of what appear to be magnetosheath/boundary layer electrons. They believe that this modulated precipitation may be responsible for the propagation of upstream wave power in the Pc 3 frequency band into the high-latitude ionosphere, from whence it may be transported throughout the dayside outer magnetosphere by means of an ionospheric transistor. In this model, modulations in ionospheric conductivity caused by cusp/cleft precipitation cause varying ionospheric currents with frequency spectra determined by the upstream waves; these modulations will be superimposed on the Birkeland currents, which close via these ionospheric currents. Modulated region 2 Birkeland currents will in turn provide a narrow-band source of wave energy to a wide range of dayside local times in the outer magnetosphere

Coupling of the Magnetosphere-Ionosphere/Thermosphere and Oxygen Outflow-- MIT Mission

Science.gov (United States)

Fu, S.

2017-12-01

The goal of the MIT mission is to understand the coupling of the magnetosphere and ionosphere from the prospective of particles. It will focus on the outflow of the ionosphere particles (mainly oxygen ions) from the Earth, including the acceleration mechanisms of oxygen ions and their relative importance in different regions, the importance of these ions while transferred into the magnetosphere and the roles they played in magnetosphere activities. A constellation of four satellites orbiting at three elliptical orbits will provide the unique opportunities to observed there ions at three different altitude with temporal changes of the flux of these particles and the magnetic field environments. The conceptual design of the spacecraft and a summary of the payload will be presented. The MIT mission was selected as one of the five candidates for the upcoming mission plan in China.

Open and partially closed models of the solar wind interaction with outer planet magnetospheres. The case of Saturn

Energy Technology Data Exchange (ETDEWEB)

Belenkaya, Elena S.; Alexeev, Igor I.; Kalegaev, Vladimir V.; Pensionerov, Ivan A.; Blokhina, Marina S.; Parunakian, David A. [Federal State Budget Educational Institution of Higher Education M.V. Lomonosov Moscow State Univ., Moscow (Russian Federation). Skobeltsyn Inst. of Nuclear Physics (SINP MSU); Cowley, Stanley W. H. [Leicester Univ. (United Kingdom). Dept. of Physics and Astronomy

2017-07-01

A wide variety of interactions take place between the magnetized solar wind plasma outflow from the Sun and celestial bodies within the solar system. Magnetized planets form magnetospheres in the solar wind, with the planetary field creating an obstacle in the flow. The reconnection efficiency of the solar-wind-magnetized planet interaction depends on the conditions in the magnetized plasma flow passing the planet. When the reconnection efficiency is very low, the interplanetary magnetic field (IMF) does not penetrate the magnetosphere, a condition that has been widely discussed in the recent literature for the case of Saturn. In the present paper, we study this issue for Saturn using Cassini magnetometer data, images of Saturn's ultraviolet aurora obtained by the HST, and the paraboloid model of Saturn's magnetospheric magnetic field. Two models are considered: first, an open model in which the IMF penetrates the magnetosphere, and second, a partially closed model in which field lines from the ionosphere go to the distant tail and interact with the solar wind at its end. We conclude that the open model is preferable, which is more obvious for southward IMF. For northward IMF, the model calculations do not allow us to reach definite conclusions. However, analysis of the observations available in the literature provides evidence in favor of the open model in this case too. The difference in magnetospheric structure for these two IMF orientations is due to the fact that the reconnection topology and location depend on the relative orientation of the IMF vector and the planetary dipole magnetic moment. When these vectors are parallel, two-dimensional reconnection occurs at the low-latitude neutral line. When they are antiparallel, three-dimensional reconnection takes place in the cusp regions. Different magnetospheric topologies determine different mapping of the open-closed boundary in the ionosphere, which can be considered as a proxy for the poleward edge

Hydromagnetic Waves in the Magnetosphere and the Ionosphere

CERN Document Server

Alperovich, Leonid S

2007-01-01

The book deals with Ultra-Low-Frequency (ULF)-electromagnetic waves observed on Earth and in Space. These are so-called geomagnetic variations or pulsations. Alfvén's discovery related to the influence of the strong magnetic field on the conducting fluids (magnetohydrodynamics) led to development of the concept that the ULF-waves are magnetospheric magnetohydrodynamic (MHD)-waves. MHD-waves at their propagation gather information about the magnetosphere, ionosphere, and the ground. There are two applied aspects based on using the ULF electromagnetic oscillations. The first one is the ground-based diagnostics of the magnetosphere. This is an attempt to monitor in the real time the magnetosphere size, distance to the last closed field-lines, distribution of the cold plasma, etc. The second one is the deep electromagnetic sounding of the Earth. The basis for these studies is the capability of any electromagnetic wave to penetrate a conductor to a finite depth. The ULF-waves can reach the depth of a few hundred ...

Thermosphere as a sink of magnetospheric energy - a review of recent observations of dynamics

International Nuclear Information System (INIS)

Killeen, T.L.

1985-01-01

It is pointed out that the past few years have seen an unprecedented influx of new experimental information on the dynamics of the neutral upper atmosphere of the earth. Vector wind measurements provide new information for studies of the thermospheric response to magnetospheric forcing. This response occurs through the medium of convecting ionospheric ions set into motion by electric fields of magnetospheric origin. The ultimate sink for much of the energy and momentum coming from the magnetosphere is the neutral thermosphere whose dynamics have, in the past, received far less attention than their ionospheric counterpart because of basic experimental limitations. In this paper, a review is provided of the progress made in the last few years on the basis of the Dynamics Explorer neutral wind observations, taking into account the coupling between the magnetosphere and the thermosphere via the ionosphere. 26 references

Structure of the polar ionosphere and convection of magnetospheric plasma outside the plazmapause

International Nuclear Information System (INIS)

Mozhaev, A.M.; Osipov, N.K.; AN SSSR, Moscow. Inst. Zemnogo Magnetizma, Ionosfery i Rasprostraneniya Radiovoln)

1977-01-01

The effect of large-scale magnetospheric convection on the space structure of high-latitude ionosphere was investigated. Simple analytical models were used. The continuity equation for the electron concentration at a given rate of transfer is solved. It has been found that the formation of the principal structural forms in the ionosphere is associated with the horizontal convective transfer of ionospheric plasma

Artificial electron beams in the magnetosphere and ionosphere

International Nuclear Information System (INIS)

Winckler, J.R.

1990-01-01

The Plasma Diagnostics Payload of the Echo 7 satellite carried TV cameras and photometers by means of which the luminosity around an electron beam in the polar ionosphere could be studied. It was found that, while the beam Larmor spiral could be clearly seen near 100 km, above this only a column due to suprathermal electrons was observable. At high altitudes, the emission of neutral gas both generated powerful luminosity and substantially reduced accelerator potentials. An analysis of conjugate echoes indicates that inferred magnetospheric electric fields do not map well into the ionosphere, as well as the presence of strong pitch-angle scattering. 11 refs

Discovery of Suprathermal Fe+ in and near Earth's Magnetosphere

Science.gov (United States)

Christon, S. P.; Hamilton, D. C.; Plane, J. M. C.; Mitchell, D. G.; Grebowsky, J. M.; Spjeldvik, W. N.; Nylund, S. R.

2017-12-01

Suprathermal (87-212 keV/e) singly charged iron, Fe+, has been observed in and near Earth's equatorial magnetosphere using long-term ( 21 years) Geotail/STICS ion composition data. Fe+ is rare compared to dominant suprathermal solar wind and ionospheric origin heavy ions. Earth's suprathermal Fe+ appears to be positively associated with both geomagnetic and solar activity. Three candidate lower-energy sources are examined for relevance: ionospheric outflow of Fe+ escaped from ion layers altitude, charge exchange of nominal solar wind Fe+≥7, and/or solar wind transported inner source pickup Fe+ (likely formed by solar wind Fe+≥7 interaction with near sun interplanetary dust particles, IDPs). Semi-permanent ionospheric Fe+ layers form near 100 km altitude from the tons of IDPs entering Earth's atmosphere daily. Fe+ scattered from these layers is observed up to 1000 km altitude, likely escaping in strong ionospheric outflows. Using 26% of STICS's magnetosphere-dominated data at low-to-moderate geomagnetic activity levels, we demonstrate that solar wind Fe charge exchange secondaries are not an obvious Fe+ source then. Earth flyby and cruise data from Cassini/CHEMS, a nearly identical instrument, show that inner source pickup Fe+ is likely not important at suprathermal energies. Therefore, lacking any other candidate sources, it appears that ionospheric Fe+ constitutes at least an important portion of Earth's suprathermal Fe+, comparable to observations at Saturn where ionospheric origin suprathermal Fe+ has also been observed.

The effect of nonlinear ionospheric conductivity enhancement on magnetospheric substorms

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E. Spencer

2013-06-01

Full Text Available We introduce the effect of enhanced ionospheric conductivity into a low-order, physics-based nonlinear model of the nightside magnetosphere called WINDMI. The model uses solar wind and interplanetary magnetic field (IMF parameters from the ACE satellite located at the L1 point to predict substorm growth, onset, expansion and recovery measured by the AL index roughly 50–60 min in advance. The dynamics introduced by the conductivity enhancement into the model behavior is described, and illustrated through using synthetically constructed solar wind parameters as input. We use the new model to analyze two well-documented isolated substorms: one that occurred on 31 July 1997 from Aksnes et al. (2002, and another on 13 April 2000 from Huang et al. (2004. These two substorms have a common feature in that the solar wind driver sharply decreases in the early part of the recovery phase, and that neither of them are triggered by northward turning of the IMF Bz. By controlling the model parameters such that the onset time of the substorm is closely adhered to, the westward auroral electrojet peaks during substorm expansion are qualitatively reproduced. Furthermore, the electrojet recovers more slowly with enhanced conductivity playing a role, which explains the data more accurately.

Magnetosphere - Ionosphere - Thermosphere (MIT) Coupling at Jupiter

Science.gov (United States)

Yates, J. N.; Ray, L. C.; Achilleos, N.

2017-12-01

Jupiter's upper atmospheric temperature is considerably higher than that predicted by Solar Extreme Ultraviolet (EUV) heating alone. Simulations incorporating magnetosphere-ionosphere coupling effects into general circulation models have, to date, struggled to reproduce the observed atmospheric temperatures under simplifying assumptions such as azimuthal symmetry and a spin-aligned dipole magnetic field. Here we present the development of a full three-dimensional thermosphere model coupled in both hemispheres to an axisymmetric magnetosphere model. This new coupled model is based on the two-dimensional MIT model presented in Yates et al., 2014. This coupled model is a critical step towards to the development of a fully coupled 3D MIT model. We discuss and compare the resulting thermospheric flows, energy balance and MI coupling currents to those presented in previous 2D MIT models.

A three-dimensional, iterative mapping procedure for the implementation of an ionosphere-magnetosphere anisotropic Ohm's law boundary condition in global magnetohydrodynamic simulations

Directory of Open Access Journals (Sweden)

M. L. Goodman

1995-08-01

Full Text Available The mathematical formulation of an iterative procedure for the numerical implementation of an ionosphere-magnetosphere (IM anisotropic Ohm's law boundary condition is presented. The procedure may be used in global magnetohydrodynamic (MHD simulations of the magnetosphere. The basic form of the boundary condition is well known, but a well-defined, simple, explicit method for implementing it in an MHD code has not been presented previously. The boundary condition relates the ionospheric electric field to the magnetic field-aligned current density driven through the ionosphere by the magnetospheric convection electric field, which is orthogonal to the magnetic field B, and maps down into the ionosphere along equipotential magnetic field lines. The source of this electric field is the flow of the solar wind orthogonal to B. The electric field and current density in the ionosphere are connected through an anisotropic conductivity tensor which involves the Hall, Pedersen, and parallel conductivities. Only the height-integrated Hall and Pedersen conductivities (conductances appear in the final form of the boundary condition, and are assumed to be known functions of position on the spherical surface R=R1 representing the boundary between the ionosphere and magnetosphere. The implementation presented consists of an iterative mapping of the electrostatic potential ψ the gradient of which gives the electric field, and the field-aligned current density between the IM boundary at R=R1 and the inner boundary of an MHD code which is taken to be at R2>R1. Given the field-aligned current density on R=R2, as computed by the MHD simulation, it is mapped down to R=R1 where it is used to compute ψ by solving the equation that is the IM Ohm's law boundary condition. Then ψ is mapped out to R=R2, where it is used to update the electric field and the component of velocity perpendicular to B. The updated electric field and perpendicular velocity serve as new boundary

Multifluid Block-Adaptive-Tree Solar Wind Roe-Type Upwind Scheme: Magnetospheric Composition and Dynamics During Geomagnetic Storms-Initial Results

Science.gov (United States)

Glocer, A.; Toth, G.; Ma, Y.; Gombosi, T.; Zhang, J.-C.; Kistler, L. M.

2009-01-01

The magnetosphere contains a significant amount of ionospheric O+, particularly during geomagnetically active times. The presence of ionospheric plasma in the magnetosphere has a notable impact on magnetospheric composition and processes. We present a new multifluid MHD version of the Block-Adaptive-Tree Solar wind Roe-type Upwind Scheme model of the magnetosphere to track the fate and consequences of ionospheric outflow. The multifluid MHD equations are presented as are the novel techniques for overcoming the formidable challenges associated with solving them. Our new model is then applied to the May 4, 1998 and March 31, 2001 geomagnetic storms. The results are juxtaposed with traditional single-fluid MHD and multispecies MHD simulations from a previous study, thereby allowing us to assess the benefits of using a more complex model with additional physics. We find that our multifluid MHD model (with outflow) gives comparable results to the multispecies MHD model (with outflow), including a more strongly negative Dst, reduced CPCP, and a drastically improved magnetic field at geosynchronous orbit, as compared to single-fluid MHD with no outflow. Significant differences in composition and magnetic field are found between the multispecies and multifluid approach further away from the Earth. We further demonstrate the ability to explore pressure and bulk velocity differences between H+ and O+, which is not possible when utilizing the other techniques considered

Observations of polar patches generated by solar wind Alfvén wave coupling to the dayside magnetosphere

Directory of Open Access Journals (Sweden)

P. Prikryl

1999-04-01

observed by the ground magnetometers, riometers and radars. It is concluded that the FLRs and FCEs that produced patches were driven by solar wind Alfvén waves coupling to the dayside magnetosphere. During a period of southward IMF the dawn-dusk electric field associated with the Alfvén waves modulated the subsolar magnetic reconnection into pulses that resulted in convection flow bursts mapping to the ionospheric footprint of the cusp.Key words. Ionosphere (polar ionosphere. Magneto- spheric physics (magnetosphere-ionosphere interactions; polar wind-magnetosphere interactions.

The Role of Ionospheric Outflow Preconditioning in Determining Storm Geoeffectiveness

Science.gov (United States)

Welling, D. T.; Liemohn, M. W.; Ridley, A. J.

2012-12-01

It is now well accepted that ionospheric outflow plays an important role in the development of the plasma sheet and ring current during geomagnetic storms. Furthermore, even during quiet times, ionospheric plasma populates the magnetospheric lobes, producing a reservoir of hydrogen and oxygen ions. When the Interplanetary Magnetic Field (IMF) turns southward, this reservoir is connected to the plasma sheet and ring current through magnetospheric convection. Hence, the conditions of the ionosphere and magnetospheric lobes leading up to magnetospheric storm onset have important implications for storm development. Despite this, there has been little research on this preconditioning; most global simulations begin just before storm onset, neglecting preconditioning altogether. This work explores the role of preconditioning in determining the geoeffectiveness of storms using a coupled global model system. A model of ionospheric outflow (the Polar Wind Outflow Model, PWOM) is two-way coupled to a global magnetohydrodynamic model (the Block-Adaptive Tree Solar wind Roe-type Upwind Scheme, BATS-R-US), which in turn drives a ring current model (the Ring current Atmosphere interactions Model, RAM). This unique setup is used to simulate an idealized storm. The model is started at many different times, from 1 hour before storm onset to 12 hours before. The effects of storm preconditioning are examined by investigating the total ionospheric plasma content in the lobes just before onset, the total ionospheric contribution in the ring current just after onset, and the effects on Dst, magnetic elevation angle at geosynchronous, and total ring current energy density. This experiment is repeated for different solar activity levels as set by F10.7 flux. Finally, a synthetic double-dip storm is constructed to see how two closely spaced storms affect each other by changing the preconditioning environment. It is found that preconditioning of the magnetospheric lobes via ionospheric

From the Sun to the Earth: impact of the 27-28 May 2003 solar events on the magnetosphere, ionosphere and thermosphere

Directory of Open Access Journals (Sweden)

C. Hanuise

2006-03-01

Full Text Available During the last week of May 2003, the solar active region AR 10365 produced a large number of flares, several of which were accompanied by Coronal Mass Ejections (CME. Specifically on 27 and 28 May three halo CMEs were observed which had a significant impact on geospace. On 29 May, upon their arrival at the L1 point, in front of the Earth's magnetosphere, two interplanetary shocks and two additional solar wind pressure pulses were recorded by the ACE spacecraft. The interplanetary magnetic field data showed the clear signature of a magnetic cloud passing ACE. In the wake of the successive increases in solar wind pressure, the magnetosphere became strongly compressed and the sub-solar magnetopause moved inside five Earth radii. At low altitudes the increased energy input to the magnetosphere was responsible for a substantial enhancement of Region-1 field-aligned currents. The ionospheric Hall currents also intensified and the entire high-latitude current system moved equatorward by about 10°. Several substorms occurred during this period, some of them - but not all - apparently triggered by the solar wind pressure pulses. The storm's most notable consequences on geospace, including space weather effects, were (1 the expansion of the auroral oval, and aurorae seen at mid latitudes, (2 the significant modification of the total electron content in the sunlight high-latitude ionosphere, (3 the perturbation of radio-wave propagation manifested by HF blackouts and increased GPS signal scintillation, and (4 the heating of the thermosphere, causing increased satellite drag. We discuss the reasons why the May 2003 storm is less intense than the October-November 2003 storms, although several indicators reach similar intensities.

The Comprehensive Inner Magnetosphere-Ionosphere Model

Science.gov (United States)

Fok, M.-C.; Buzulukova, N. Y.; Chen, S.-H.; Glocer, A.; Nagai, T.; Valek, P.; Perez, J. D.

2014-01-01

Simulation studies of the Earth's radiation belts and ring current are very useful in understanding the acceleration, transport, and loss of energetic particles. Recently, the Comprehensive Ring Current Model (CRCM) and the Radiation Belt Environment (RBE) model were merged to form a Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model. CIMI solves for many essential quantities in the inner magnetosphere, including ion and electron distributions in the ring current and radiation belts, plasmaspheric density, Region 2 currents, convection potential, and precipitation in the ionosphere. It incorporates whistler mode chorus and hiss wave diffusion of energetic electrons in energy, pitch angle, and cross terms. CIMI thus represents a comprehensive model that considers the effects of the ring current and plasmasphere on the radiation belts. We have performed a CIMI simulation for the storm on 5-9 April 2010 and then compared our results with data from the Two Wide-angle Imaging Neutral-atom Spectrometers and Akebono satellites. We identify the dominant energization and loss processes for the ring current and radiation belts. We find that the interactions with the whistler mode chorus waves are the main cause of the flux increase of MeV electrons during the recovery phase of this particular storm. When a self-consistent electric field from the CRCM is used, the enhancement of MeV electrons is higher than when an empirical convection model is applied. We also demonstrate how CIMI can be a powerful tool for analyzing and interpreting data from the new Van Allen Probes mission.

On magnetospheric electron impact ionisation and dynamics in Titan's ram-side and polar ionosphere – a Cassini case study

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G. R. Lewis

2007-11-01

Full Text Available We present data from the sixth Cassini flyby of Titan (T5, showing that the magnetosphere of Saturn strongly interacts with the moon's ionosphere and exo-ionosphere. A simple electron ionisation model provides a reasonable agreement with the altitude structure of the ionosphere. Furthermore, we suggest that the dense and cold exo-ionosphere (from the exobase at 1430 km and outward to several Titan radii from the surface can be explained by magnetospheric forcing and other transport processes whereas exospheric ionisation by impacting low energy electrons seems to play a minor role.

The magnetosphere under weak solar wind forcing

Directory of Open Access Journals (Sweden)

C. J. Farrugia

2007-02-01

Full Text Available The Earth's magnetosphere was very strongly disturbed during the passage of the strong shock and the following interacting ejecta on 21–25 October 2001. These disturbances included two intense storms (Dst*≈−250 and −180 nT, respectively. The cessation of this activity at the start of 24 October ushered in a peculiar state of the magnetosphere which lasted for about 28 h and which we discuss in this paper. The interplanetary field was dominated by the sunward component [B=(4.29±0.77, −0.30±0.71, 0.49±0.45 nT]. We analyze global indicators of geomagnetic disturbances, polar cap precipitation, ground magnetometer records, and ionospheric convection as obtained from SuperDARN radars. The state of the magnetosphere is characterized by the following features: (i generally weak and patchy (in time low-latitude dayside reconnection or reconnection poleward of the cusps; (ii absence of substorms; (iii a monotonic recovery from the previous storm activity (Dst corrected for magnetopause currents decreasing from ~−65 to ~−35 nT, giving an unforced decreased of ~1.1 nT/h; (iv the probable absence of viscous-type interaction originating from the Kelvin-Helmholtz (KH instability; (v a cross-polar cap potential of just 20–30 kV; (vi a persistent, polar cap region containing (vii very weak, and sometimes absent, electron precipitation and no systematic inter-hemisphere asymmetry. Whereas we therefore infer the presence of a moderate amount of open flux, the convection is generally weak and patchy, which we ascribe to the lack of solar wind driver. This magnetospheric state approaches that predicted by Cowley and Lockwood (1992 but has never yet been observed.

O+ trough zones in the polar cap ionosphere-magnetosphere coupling region

Science.gov (United States)

Horwitz, James; Zeng, Wen; Jaafari, Fajer

Regions of low-density troughs in O+ have been observed at 1 RE altitude in the polar cap ionosphere-magnetosphere region by the Thermal Ion Dynamics Experiment(TIDE) on the POLAR spacecraft. In this presentation, the UT Arlington Dynamic Fluid-Kinetic (DyFK) code is employed to investigate the formation of such O+ density troughs. We utilize convection paths of flux tubes in the high-latitude region as prescribed by an empirical convection model with solar wind inputs to track the evolution of ionospheric plasma transport and in particular O+ densities along these tubes with time/space. The flux tubes are subjected to auroral processes of precipitation and wave-driven ion heating when they pass through the auroral oval, which tends to elevate the plasma densities in these tubes. When the F-regions of such tubes traverse locations where the F-region is in darkness, recombination there causes the higher-altitude regions to drain and the densities to decline throughout. Owing to the varying effects of these processes, significant and low trough-like densities at higher altitudes developed along these flux tubes. The modeled densities near 6000 km altitudes will be compared with multiple POLAR passes featuring POLAR/TIDE-measured O+ densities for inside and outside of such trough regions.

Hybrid Alfvén resonant mode generation in the magnetosphere-ionosphere coupling system

International Nuclear Information System (INIS)

Hiraki, Yasutaka; Watanabe, Tomo-Hiko

2012-01-01

Feedback unstable Alfvén waves involving global field-line oscillations and the ionospheric Alfvén resonator (IAR) were comprehensively studied to clarify their properties of frequency dispersion, growth rate, and eigenfunctions. It is discovered that a new mode called here the hybrid Alfvén resonant (HAR) mode can be destabilized in the magnetosphere-ionosphere coupling system with a realistic Alfvén velocity profile. The HAR mode found in a high frequency range over 0.3 Hz is caused by coupling of IAR modes with strong dispersion and magnetospheric cavity resonances. The harmonic relation of HAR eigenfrequencies is characterized by a constant frequency shift from those of IAR modes. The three modes are robustly found even if effects of two-fluid process and ionospheric collision are taken into account and thus are anticipated to be detected by magnetic field observations in a frequency range of 0.3–1 Hz in auroral and polar-cap regions.

From the Sun to the Earth: impact of the 27-28 May 2003 solar events on the magnetosphere, ionosphere and thermosphere

Directory of Open Access Journals (Sweden)

C. Hanuise

2006-03-01

Full Text Available During the last week of May 2003, the solar active region AR 10365 produced a large number of flares, several of which were accompanied by Coronal Mass Ejections (CME. Specifically on 27 and 28 May three halo CMEs were observed which had a significant impact on geospace. On 29 May, upon their arrival at the L1 point, in front of the Earth's magnetosphere, two interplanetary shocks and two additional solar wind pressure pulses were recorded by the ACE spacecraft. The interplanetary magnetic field data showed the clear signature of a magnetic cloud passing ACE. In the wake of the successive increases in solar wind pressure, the magnetosphere became strongly compressed and the sub-solar magnetopause moved inside five Earth radii. At low altitudes the increased energy input to the magnetosphere was responsible for a substantial enhancement of Region-1 field-aligned currents. The ionospheric Hall currents also intensified and the entire high-latitude current system moved equatorward by about 10°. Several substorms occurred during this period, some of them - but not all - apparently triggered by the solar wind pressure pulses. The storm's most notable consequences on geospace, including space weather effects, were (1 the expansion of the auroral oval, and aurorae seen at mid latitudes, (2 the significant modification of the total electron content in the sunlight high-latitude ionosphere, (3 the perturbation of radio-wave propagation manifested by HF blackouts and increased GPS signal scintillation, and (4 the heating of the thermosphere, causing increased satellite drag. We discuss the reasons why the May 2003 storm is less intense than the October-November 2003 storms, although several indicators reach similar intensities.

Auroral vortex street formed by the magnetosphere-ionosphere coupling instability

Science.gov (United States)

Hiraki, Y.

2015-02-01

By performing three-dimensional magnetohydrodynamic simulations including Alfvén eigenmode perturbations most unstable to the ionospheric feedback effects, we examined the auroral vortex street that often appears just before substorm onset. We found that an initially placed arc splits, intensifies, and rapidly deforms into a vortex street. We also found that there is a critical convection electric field for growth of the Alfvén eigenmodes. The vortex street is shown to be a consequence of coupling between the magnetospheric Alfvén waves carrying field-aligned currents and the ionospheric density waves driven by Pedersen/Hall currents.

Solar wind and its interaction with the Earth magnetosphere

International Nuclear Information System (INIS)

Grib, S.A.

1978-01-01

A critical review is given regarding the research of the stationary and non-stationary interaction of the solar wind with the Earth magnetosphere. Highlighted is the significance of the interplanetary magnetic field in the non-stationary movement of the solar wind flux. The problem of the solar wind shock waves interaction with the ''bow wave-Earth's magnetosphere'' system is being solved. Considered are the secondary phenomena, as a result of which the depression-type wave occurs, that lowers the pressure on the Earth's maanetosphere. The law, governing the movement of the magnetosphere subsolar point during the abrupt start of a geomagnetic storm has been discovered. Stationary circumvention of the magnetosphere by the solar wind flux is well described by the gas dynamic theory of the hypersonic flux. Non-stationary interaction of the solar wind shock waves with the magnetosphere is magnetohydrodynamic. It is pointed out, that the problems under consideration are important for the forecasting of strong geomagnetic perturbations on the basis of cosmic observations

Characterizing the Meso-scale Plasma Flows in Earth's Coupled Magnetosphere-Ionosphere-Thermosphere System

Science.gov (United States)

Gabrielse, C.; Nishimura, T.; Lyons, L. R.; Gallardo-Lacourt, B.; Deng, Y.; McWilliams, K. A.; Ruohoniemi, J. M.

2017-12-01

NASA's Heliophysics Decadal Survey put forth several imperative, Key Science Goals. The second goal communicates the urgent need to "Determine the dynamics and coupling of Earth's magnetosphere, ionosphere, and atmosphere and their response to solar and terrestrial inputs...over a range of spatial and temporal scales." Sun-Earth connections (called Space Weather) have strong societal impacts because extreme events can disturb radio communications and satellite operations. The field's current modeling capabilities of such Space Weather phenomena include large-scale, global responses of the Earth's upper atmosphere to various inputs from the Sun, but the meso-scale ( 50-500 km) structures that are much more dynamic and powerful in the coupled system remain uncharacterized. Their influences are thus far poorly understood. We aim to quantify such structures, particularly auroral flows and streamers, in order to create an empirical model of their size, location, speed, and orientation based on activity level (AL index), season, solar cycle (F10.7), interplanetary magnetic field (IMF) inputs, etc. We present a statistical study of meso-scale flow channels in the nightside auroral oval and polar cap using SuperDARN. These results are used to inform global models such as the Global Ionosphere Thermosphere Model (GITM) in order to evaluate the role of meso-scale disturbances on the fully coupled magnetosphere-ionosphere-thermosphere system. Measuring the ionospheric footpoint of magnetospheric fast flows, our analysis technique from the ground also provides a 2D picture of flows and their characteristics during different activity levels that spacecraft alone cannot.

Observations of polar patches generated by solar wind Alfvén wave coupling to the dayside magnetosphere

Directory of Open Access Journals (Sweden)

P. Prikryl

wind, IMP 8 observed large amplitude Alfvén waves that were correlated with Pc5 pulsations observed by the ground magnetometers, riometers and radars. It is concluded that the FLRs and FCEs that produced patches were driven by solar wind Alfvén waves coupling to the dayside magnetosphere. During a period of southward IMF the dawn-dusk electric field associated with the Alfvén waves modulated the subsolar magnetic reconnection into pulses that resulted in convection flow bursts mapping to the ionospheric footprint of the cusp.

Key words. Ionosphere (polar ionosphere. Magneto- spheric physics (magnetosphere-ionosphere interactions; polar wind-magnetosphere interactions.

Pulsar Magnetospheres and Pulsar Winds

OpenAIRE

Beskin, Vasily S.

2016-01-01

Surprisingly, the chronology of nearly 50 years of the pulsar magnetosphere and pulsar wind research is quite similar to the history of our civilization. Using this analogy, I have tried to outline the main results obtained in this field. In addition to my talk, the possibility of particle acceleration due to different processes in the pulsar magnetosphere is discussed in more detail.

A very bright SAR arc: implications for extreme magnetosphere-ionosphere coupling

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J. Baumgardner

2007-01-01

Full Text Available In contrast to the polar aurora visible during geomagnetic storms, stable auroral red (SAR arcs offer a sub-visual manifestation of direct magnetosphere-ionosphere (M-I coupling at midlatitudes. The SAR arc emission at 6300 Å is driven by field-aligned magnetospheric energy transport from ring current/plasmapause locations into the ionosphere-thermosphere system. The first SAR arc was observed at the dawn of the space age (1956, and the typical brightness levels and occurrence patterns obtained from subsequent decades of observations appear to be consistent with the downward heat conduction theory, i.e., heated ambient F-layer electrons excite oxygen atoms to produce a spectrally pure emission. On very rare occasions, a SAR arc has been reported to be at brightness levels visible to the naked eye. Here we report on the first case of a very bright SAR arc (~13 kilo-Rayleighs observed by four diagnostic systems that sampled various aspects of the sub-auroral domain near Millstone Hill, MA, on the night of 29 October 1991: an imaging spectrograph, an all-sky camera, an incoherent scatter radar (ISR, and a DMSP satellite. Simulations of emission using the ISR and DMSP data with the MSIS neutral atmosphere succeed in reproducing the brightness levels observed. This provides a robust confirmation of M-I coupling theory in its most extreme aeronomic form within the innermost magnetosphere (L~2 during a rare superstorm event. The unusually high brightness value appears to be due to the rare occurrence of the heating of dense ionospheric plasma just equatorward of the trough/plasmapause location, in contrast to the more typical heating of the less dense F-layer within the trough.

Report of the magnetospheric physics panel

International Nuclear Information System (INIS)

Burch, J.L.; Potemra, T.A.; Ashourabdalla, M.; Baker, D.N.; Cattell, C.A.; Chang, A.F.; Frank, L.A.; Goertz, C.K.; Kivelson, M.G.; Lee, Lou-Chuang

1991-01-01

Magnetospheric research is a relatively new area in the study of the Earth's environment. The present report attempts to overview past and future research on this topic. The goals of magnetospheric research are numerous, and include: understanding large scale magnetospheres of the Earth and other planets; understanding the plasma physical processes operating within the various magnetospheres; to understand how mass, energy and momentum are transmitted from the solar wind; to understand quantitatively the coupling between magnetospheres and their ionospheres; and to understand the magnetospheric mechanisms which accelerate particles to high energies, as well as the ultimate fate of these particles. The report continues on to summarize a number of proposed space missions aimed at data acquisition. Finally, there is a brief discussion of the theory and modeling of magnetospheres

Particle precipitation influence in the conductivity of the auroral ionosphere during magnetic storms

International Nuclear Information System (INIS)

Monreal M, R.; Llop, C.

2002-01-01

The study of the energy transfer between the different regions of the solar wind - magnetosphere - ionosphere system is probably the main goal in Solar-Terrestrial Physics. In the magnetosphere - ionosphere coupling, the ionosphere power dissipation is highly sensitive to the conductivity in such a way that a detailed knowledge of this property in the auroral and polar ionosphere is of great interest because it is important not only to determine Joule heat, but also for electric fields and currents models including the field aligned currents coupling the magnetosphere and ionosphere. The main sources of ionization and subsequent conductivity in the ionosphere are due to the emission of electromagnetic radiation and charged energetic particles from the sun. In this work it is analysed the influence of the precipitating electrons on the auroral ionosphere conductivity during magnetic storms. It is shown that the conductance values appear sub estimated for high levels of activity due to the saturation produced during very intense magnetic storms. (Author)

Introduction to the thematic series "Coupling of the magnetosphere-ionosphere system"

Science.gov (United States)

Yao, Z. H.; Murphy, K. R.; Rae, I. J.; Balan, N.

2017-12-01

This thematic series contains 4 papers mostly presented at the 2016 AOGS meeting in Beijing. The four papers investigate four key regions in the magnetosphere-ionosphere coupling process: mid-tail magnetosphere, near-Earth magnetosphere, inner magnetosphere, and the polar ground region. Guo et al. (Geosci Lett 4:18, 2017) study the current system in reconnection region using 2.5D particle-in-cell simulations. Yao et al. (Geosci Lett 4:8, 2017) use conjugate measurements from ground auroral imagers and in situ THEMIS spacecraft to reveal the mechanism for the wave-like auroral structures prior to substorm onset. Zhang et al. (Geosci Lett 4:20, 2017) investigate the profiles of resonance zone and resonant frequency in the Landau resonance between radiation belt electrons and magnetosonic waves and between protons and cyclotron waves. Rae et al. (Geosci Lett 4:23, 2017) determine the relative timing between sudden increases in amplitude, or onsets, of different ultra-low-frequency wave bands during substorms.

Stormtime and Interplanetary Magnetic Field Drivers of Wave and Particle Acceleration Processes in the Magnetosphere-Ionosphere Transition Region

Science.gov (United States)

Hatch, Spencer Mark

The magnetosphere-ionosphere (M-I) transition region is the several thousand-kilometer stretch between the cold, dense and variably resistive region of ionized atmospheric gases beginning tens of kilometers above the terrestrial surface, and the hot, tenuous, and conductive plasmas that interface with the solar wind at higher altitudes. The M-I transition region is therefore the site through which magnetospheric conditions, which are strongly susceptible to solar wind dynamics, are communicated to ionospheric plasmas, and vice versa. We systematically study the influence of geomagnetic storms on energy input, electron precipitation, and ion outflow in the M-I transition region, emphasizing the role of inertial Alfven waves both as a preferred mechanism for dynamic (instead of static) energy transfer and particle acceleration, and as a low-altitude manifestation of high-altitude interaction between the solar wind and the magnetosphere, as observed by the FAST satellite. Via superposed epoch analysis and high-latitude distributions derived as a function of storm phase, we show that storm main and recovery phase correspond to strong modulations of measures of Alfvenic activity in the vicinity of the cusp as well as premidnight. We demonstrate that storm main and recovery phases occur during 30% of the four-year period studied, but together account for more than 65% of global Alfvenic energy deposition and electron precipitation, and more than 70% of the coincident ion outflow. We compare observed interplanetary magnetic field (IMF) control of inertial Alfven wave activity with Lyon-Fedder-Mobarry global MHD simulations predicting that southward IMF conditions lead to generation of Alfvenic power in the magnetotail, and that duskward IMF conditions lead to enhanced prenoon Alfvenic power in the Northern Hemisphere. Observed and predicted prenoon Alfvenic power enhancements contrast with direct-entry precipitation, which is instead enhanced postnoon. This situation

A very bright SAR arc: implications for extreme magnetosphere-ionosphere coupling

Directory of Open Access Journals (Sweden)

J. Baumgardner

2008-01-01

Full Text Available In contrast to the polar aurora visible during geomagnetic storms, stable auroral red (SAR arcs offer a sub-visual manifestation of direct magnetosphere-ionosphere (M-I coupling at midlatitudes. The SAR arc emission at 6300 Å is driven by field-aligned magnetospheric energy transport from ring current/plasmapause locations into the ionosphere-thermosphere system. The first SAR arc was observed at the dawn of the space age (1956, and the typical brightness levels and occurrence patterns obtained from subsequent decades of observations appear to be consistent with the downward heat conduction theory, i.e., heated ambient F-layer electrons excite oxygen atoms to produce a spectrally pure emission. On very rare occasions, a SAR arc has been reported to be at brightness levels visible to the naked eye. Here we report on the first case of a very bright SAR arc (~13 kilo-Rayleighs observed by four diagnostic systems that sampled various aspects of the sub-auroral domain near Millstone Hill, MA, on the night of 29 October 1991: an imaging spectrograph, an all-sky camera, an incoherent scatter radar (ISR, and a DMSP satellite. Simulations of emission using the ISR and DMSP data with the MSIS neutral atmosphere succeed in reproducing the brightness levels observed. This provides a robust confirmation of M-I coupling theory in its most extreme aeronomic form within the innermost magnetosphere (L~2 during a rare superstorm event. The unusually high brightness value appears to be due to the rare occurrence of the heating of dense ionospheric plasma just equatorward of the trough/plasmapause location, in contrast to the more typical heating of the less dense F-layer within the trough.

Perturbations of ionosphere-magnetosphere coupling by powerful VLF emissions from ground-based transmitters

International Nuclear Information System (INIS)

Belov, A. S.; Markov, G. A.; Ryabov, A. O.; Parrot, M.

2012-01-01

The characteristics of the plasma-wave disturbances stimulated in the near-Earth plasma by powerful VLF radiation from ground-based transmitters are investigated. Radio communication VLF transmitters of about 1 MW in power are shown to produce artificial plasma-wave channels (density ducts) in the near-Earth space that originate in the lower ionosphere above the disturbing emission source and extend through the entire ionosphere and magnetosphere of the Earth along the magnetic field lines. Measurements with the onboard equipment of the DEMETER satellite have revealed that under the action of emission from the NWC transmitter, which is one of the most powerful VLF radio transmitters, the generation of quasi-electrostatic (plasma) waves is observed on most of the satellite trajectory along the disturbed magnetic flux tube. This may probably be indicative of stimulated emission of a magnetospheric maser.

The use of iron charge state changes as a tracer for solar wind entry and energization within the magnetosphere

Directory of Open Access Journals (Sweden)

T. A. Fritz

Full Text Available The variation of the charge state of iron [Fe] ions is used to trace volume elements of plasma in the solar wind into the magnetosphere and to determine the time scales associated with the entry into and the action of the magnetospheric energization process working on these plasmas. On 2–3 May 1998 the Advanced Composition Explorer (ACE spacecraft located at the L1 libration point observed a series of changes to the average charge state of the element Fe in the solar wind plasma reflecting variation in the coronal temperature of their original source. Over the period of these two days the average Fe charge state was observed to vary from + 15 to + 6 both at the Polar satellite in the high latitude dayside magnetosphere and at ACE. During a period of southward IMF the observations at Polar inside the magnetosphere of the same Fe charge state were simultaneous with those at ACE delayed by the measured convection speed of the solar wind to the subsolar magnetopause. Comparing the phase space density as a function of energy at both ACE and Polar has indicated that significant energization of the plasma occurred on very rapid time scales. Energization at constant phase space density by a factor of 5 to 10 was observed over a range of energy from a few keV to about 1 MeV. For a detector with a fixed energy threshold in the range from 10 keV to a few hundred keV this observed energization will appear as a factor of ~10³ increase in its counting rate. Polar observations of very energetic O⁺ ions at the same time indicate that this energization process must be occurring in the high latitude cusp region inside the magnetosphere and that it is capable of energizing ionospheric ions at the same time.

Key words. Magnetospheric physics (magnetopause, cusp, and boundary layers; magnetospheric configuration and dynamics; solar wind-magnetosphere interactions

Ionospheric effect of the magnetospheric substorms at middle latitudes

International Nuclear Information System (INIS)

Cander, Lj.R.; Dominici, P.; Zolesi, B.

1988-01-01

A study is made of the F2-layer effect of magnetospheric substorms over the Mediterranean area using data from several ionospheric stations for selected events in the current sunspot cycle 21. The night-time enhancements in the critical frequency of the F2-layer (f 0 F2) and the total electron content (TEC) have been found with both premidnight and postmidnight f 0 F2 peaks and a subsequent decrease in the minimum virtual height of the F region (h'F). It is found that the enhancements occur through the nights under steady geomagnetic conditions and that the time at which it is seen at Rome and Grocka ionospheric stations is progressively earlier as geomagnetic activity increases. It has been further shown that this type of the f 0 F2 night-time increases is not always accompanied by an increase in TEC, although the reverse holds true during the nights of increased substorm activity. The fact that the considerable variability in f 0 F2, TEC and h'F at the onset of the substorm expansion are preceded by the ionospheric dynamics associated with these observations can be very useful in the identification of precursor indicative of short-term variations of ionospheric propagation conditions

Pulsar magnetosphere-wind or wave

International Nuclear Information System (INIS)

Kennel, C.F.

1979-01-01

The structure of both the interior and exterior pulsar magnetosphere depends upon the strength of its plasma source near the surface of the star. We review wave models of exterior pulsar magnetospheres in the light of a vacuum pair-production source model proposed by Sturrock, and Ruderman and Sutherland. This model predicts the existence of a cutoff, determined by the neutron star's spin rate and magnetic field strenght, beyond which coherent radio emission is no longer possible. Since the observed distribution of pulsar spin periods and period derivatives, and the distribution of pulsars with missing radio pulses, is consistent with the pair production threshold, those neutron stars observed as radio pulsars can have relativistic magnetohydrodynamic wind exterior magnetospheres, and cannot have relativistic plasma wave exterior magnetospheres. On the other hand, most erstwhile pulsars in the galaxy are probably halo objects that emit weak fluxes of energetic photons that can have relativistic wave exterior magnetospheres. Extinct pulsars have not been yet observed

Space weather and the Earth ionosphere from auroral zone to equator

Science.gov (United States)

Biktash, L.

2007-08-01

Space weather conditions, geomagnetic variations, virtual ionospheric height and the critical frequency foF2 data during the geomagnetic storms are studied to demonstrate relationships between these phenomena. We examine the solar wind conditions and the auroral equatorial ionosphere response to illustrate what kind of solar wind parameters during the geomagnetic storms leads to short-term variations of the critical frequency foF2 and virtual height at the Earth ionosphere from the auroral zone to the equator. Model simulations as disturbed ionospheric wind dynamo do not allow explaining a significant part of the experimental data. Additional investigations of the ionospheric characteristics are required to clear up the origin of the short-term equatorial ionospheric variations. The critical frequency foF2 and virtual heights observed by the ionosondes are good indicators of the true layer heights and electron concentration and may provide information about the equatorial ionosphere dynamics. Intensive magnetospheric and ionospheric currents during geomagnetic storms disturb the quiet ionosphere and cause the observed short-term variations of the ionospheric characteristics. The ionosheric wind dynamo is considered as an important and the main mechanism in generation of ionospheric electric currents and fields. The disturbed ionospheric wind dynamo can be the generator of the equatorial ionospheric electric currents during geomagnetic storms in the aftermath of strong auroral heating. The magnetospheric electric field directly penetrating into the low-latitude ionosphere can be another source of electric field. During disturbed space weather conditions magnetospheric electric fields disturb the auroral ionosphere forming auroral electrojets and by the high-latitude electric field and termospheric disturbances can penetrate to the equatorial ionosphere. That is the reason the equatorial ionospheric electric field variations like geomagnetic variations are complex

High latitude ionospheric structure

International Nuclear Information System (INIS)

1984-06-01

The Earth's ionosphere is an important element in solar-terrestrial energy transfer processes. As a major terrestrial sink for many solar and magnetospheric events, the ionosphere has characteristic features that are traced to such seemingly remote phenomena as solar flares, radiation belt wave-particle interactions and magnetospheric substorms. In considering the multiple of solar-terrestrial plasma interactions, it is important to recognize that the high-latitude ionosphere is not altogether a simple receptor of various energy deposition processes. The high-altitude ionosphere plays an active feedback role by controlling the conductivity at the base of far-reaching magnetic field lines and by providing a plasma source for the magnetosphere. Indeed, the role of the ionosphere during magnetospheric substorms is emerging as a topic for meaningful study in the overall picture of magnetospheric-ionospheric coupling

Ensemble downscaling in coupled solar wind-magnetosphere modeling for space weather forecasting.

Science.gov (United States)

Owens, M J; Horbury, T S; Wicks, R T; McGregor, S L; Savani, N P; Xiong, M

2014-06-01

Advanced forecasting of space weather requires simulation of the whole Sun-to-Earth system, which necessitates driving magnetospheric models with the outputs from solar wind models. This presents a fundamental difficulty, as the magnetosphere is sensitive to both large-scale solar wind structures, which can be captured by solar wind models, and small-scale solar wind "noise," which is far below typical solar wind model resolution and results primarily from stochastic processes. Following similar approaches in terrestrial climate modeling, we propose statistical "downscaling" of solar wind model results prior to their use as input to a magnetospheric model. As magnetospheric response can be highly nonlinear, this is preferable to downscaling the results of magnetospheric modeling. To demonstrate the benefit of this approach, we first approximate solar wind model output by smoothing solar wind observations with an 8 h filter, then add small-scale structure back in through the addition of random noise with the observed spectral characteristics. Here we use a very simple parameterization of noise based upon the observed probability distribution functions of solar wind parameters, but more sophisticated methods will be developed in the future. An ensemble of results from the simple downscaling scheme are tested using a model-independent method and shown to add value to the magnetospheric forecast, both improving the best estimate and quantifying the uncertainty. We suggest a number of features desirable in an operational solar wind downscaling scheme. Solar wind models must be downscaled in order to drive magnetospheric models Ensemble downscaling is more effective than deterministic downscaling The magnetosphere responds nonlinearly to small-scale solar wind fluctuations.

A three-dimensional, iterative mapping procedure for the implementation of an ionosphere-magnetosphere anisotropic Ohm's law boundary condition in global magnetohydrodynamic simulations

Directory of Open Access Journals (Sweden)

M. L. Goodman

Full Text Available The mathematical formulation of an iterative procedure for the numerical implementation of an ionosphere-magnetosphere (IM anisotropic Ohm's law boundary condition is presented. The procedure may be used in global magnetohydrodynamic (MHD simulations of the magnetosphere. The basic form of the boundary condition is well known, but a well-defined, simple, explicit method for implementing it in an MHD code has not been presented previously. The boundary condition relates the ionospheric electric field to the magnetic field-aligned current density driven through the ionosphere by the magnetospheric convection electric field, which is orthogonal to the magnetic field B, and maps down into the ionosphere along equipotential magnetic field lines. The source of this electric field is the flow of the solar wind orthogonal to B. The electric field and current density in the ionosphere are connected through an anisotropic conductivity tensor which involves the Hall, Pedersen, and parallel conductivities. Only the height-integrated Hall and Pedersen conductivities (conductances appear in the final form of the boundary condition, and are assumed to be known functions of position on the spherical surface R=R₁ representing the boundary between the ionosphere and magnetosphere. The implementation presented consists of an iterative mapping of the electrostatic potential ψ the gradient of which gives the electric field, and the field-aligned current density between the IM boundary at R=R₁ and the inner boundary of an MHD code which is taken to be at R₂>R₁. Given the field-aligned current density on R=R₂, as computed by the MHD simulation, it is mapped down to R=R₁ where it is used to compute ψ by solving the equation that is the IM Ohm's law boundary condition. Then ψ is mapped out

Low-energy ion outflow modulated by the solar wind energy input

Science.gov (United States)

Li, Kun; Wei, Yong; Andre, Mats; Eriksson, Anders; Haaland, Stein; Kronberg, Elena; Nilsson, Hans; Maes, Lukas

2017-04-01

Due to the spacecraft charging issue, it has been difficult to measure low-energy ions of ionospheric origin in the magnetosphere. A recent study taking advantage of the spacecraft electric potential has found that the previously 'hidden' low-energy ions is dominant in the magnetosphere. This comprehensive dataset of low-energy ions allows us to study the relationship between the ionospheric outflow and energy input from the solar wind (ɛ). In this study, we discuss the ratios of the solar wind energy input to the energy of the ionospheric outflow. We show that the ɛ controls the ionospheric outflow when the ɛ is high, while the ionospheric outflow does not systematically change with the ɛ when the ɛ is low.

The influence of solar wind variability on magnetospheric ULF wave power

International Nuclear Information System (INIS)

Pokhotelov, D.; Rae, I.J.; Mann, I.R.

2015-01-01

Magnetospheric ultra-low frequency (ULF) oscillations in the Pc 4-5 frequency range play an important role in the dynamics of Earth's radiation belts, both by enhancing the radial diffusion through incoherent interactions and through the coherent drift-resonant interactions with trapped radiation belt electrons. The statistical distributions of magnetospheric ULF wave power are known to be strongly dependent on solar wind parameters such as solar wind speed and interplanetary magnetic field (IMF) orientation. Statistical characterisation of ULF wave power in the magnetosphere traditionally relies on average solar wind-IMF conditions over a specific time period. In this brief report, we perform an alternative characterisation of the solar wind influence on magnetospheric ULF wave activity through the characterisation of the solar wind driver by its variability using the standard deviation of solar wind parameters rather than a simple time average. We present a statistical study of nearly one solar cycle (1996-2004) of geosynchronous observations of magnetic ULF wave power and find that there is significant variation in ULF wave powers as a function of the dynamic properties of the solar wind. In particular, we find that the variability in IMF vector, rather than variabilities in other parameters (solar wind density, bulk velocity and ion temperature), plays the strongest role in controlling geosynchronous ULF power. We conclude that, although time-averaged bulk properties of the solar wind are a key factor in driving ULF powers in the magnetosphere, the solar wind variability can be an important contributor as well. This highlights the potential importance of including solar wind variability especially in studies of ULF wave dynamics in order to assess the efficiency of solar wind-magnetosphere coupling.

CUTLASS HF radar observations of high-latitude azimuthally propagating vortical currents in the nightside ionosphere during magnetospheric substorms

Directory of Open Access Journals (Sweden)

J. A. Wild

Full Text Available High-time resolution CUTLASS observations and ground-based magnetometers have been employed to study the occurrence of vortical flow structures propagating through the high-latitude ionosphere during magnetospheric substorms. Fast-moving flow vortices (~800 m s^-1 associated with Hall currents flowing around upward directed field-aligned currents are frequently observed propagating at high speed (~1 km s^-1 azimuthally away from the region of the ionosphere associated with the location of the substorm expansion phase onset. Furthermore, a statistical analysis drawn from over 1000 h of high-time resolution, nightside radar data has enabled the characterisation of the bulk properties of these vortical flow systems. Their occurrence with respect to substorm phase has been investigated and a possible generation mechanism has been suggested.

Key words: Ionosphere (auroral ionosphere; electric fields and currents · Magnetospheric physics (storms and substorms

Preliminary Observations of Ionospheric Response to an Auroral Driver from the MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) Sounding Rocket Campaign

Science.gov (United States)

Fernandes, P. A.; Lynch, K. A.; Hysell, D. L.; Powell, S.; Miceli, R.; Hampton, D. L.; Ahrns, J.; Lessard, M.; Cohen, I. J.; Moen, J. I.; Bekkeng, T.

2012-12-01

The nightside sounding rocket MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) launched from Poker Flat, AK, on February 19, 2012, and reached an apogee of 325km. MICA was launched into several discrete, localized arcs in the wake of a westward traveling surge. The MICA instrumentation included both in situ and ground based instruments, and was designed to measure the response of the ionosphere to an auroral driver. More specifically, the science goal was to measure response of the ionosphere to a feedback instability in the ionospheric Alfvén resonator. The MICA payload included in situ particle, electric and magnetic field, and GPS instruments. The ground-based array consisted of a multitude of imagers, coherent and incoherent scatter radars, and a Fabry-Perot interferometer. We present observational characteristics of the response of the ionospheric plasma to the auroral drivers inferred from inverting camera data. We compare the measured precipitating electron population to inversions of camera images, which use a transport model to infer a 2D map of the precipitation. Comparisons show that as the payload passes through what appears to be an Alfvénic auroral arc, the in situ electron instrument shows dispersions indicative of Alfvénic activity. We then introduce measurements of the thermal ion distribution, to examine how the auroral arcs drive a response in the ionosphere. The thermal ion data show that the payload potential strengthens as the payload passes through the arc. When including electron density, temperature, and electric field data, we observe times in which the ionospheric environment changes as the precipitation changes, and times during which there is no measured response by the ionosphere. Future work will compare how the ion bulk flow as measured by the thermal ion instrument compares to the ExB drift as measured by the electric field instrument and to the neutral wind measurements from the Fabry-Perot interferometer

What Might We Learn About Magnetospheric Substorms at the Earth from the MESSENGER Measurements at Mercury?

Science.gov (United States)

Slavin, James A.

2008-01-01

Satellite observations at the Earth, supported by theory and modeling, have established a close connection between the episodes of intense magnetospheric convection termed substorms and the occurrence of magnetic reconnection. Magnetic reconnection at the dayside magnetopause results in strong energy input to the magnetosphere. This energy can either be stored or used immediately to power the magnetospheric convection that produces the phenomena that collectively define the 'substorm.' However, many aspects of magnetic reconnection and the dynamic response of the coupled solar wind - magnetosphere - ionosphere system at the Earth during substorms remain poorly understood. For example, the rate of magnetic reconnection is thought to be proportional to the local Alfven speed, but the limited range of changes in this solar wind parameter at 1 AU have made it difficult to detect its influence over energy input to the Earth's magnetosphere. In addition, the electrical conductance of the ionosphere and how it changes in response to auroral charged particle precipitation are hypothesized to play a critical role in the development of substorms, but the nature of this electrodynamic interaction remain difficult to deduce from Earth observations alone. The amount of energy the terrestrial magnetosphere can store in its tail, the duration of the storage, and the trigger(s) for its dissipation are all thought to be determined by not only the microphysics of the cross-tail current layer, but also the properties of the coupled magnetosphere - ionosphere system. Again, the separation of microphysics effects from system response has proved very difficult using measurements taken only at the Earth. If MESSENGER'S charged particle and magnetic field measurements confirm the occurrence of terrestrial-style substorms in Mercury's miniature magnetosphere, then it may be possible to determine how magnetospheric convection, field-aligned currents, charged particle acceleration

The Effect of Neutral Winds on Simulated Inner Magnetospheric Electric Fields During the 17 March 2013 Storm

Science.gov (United States)

Chen, M.; Lemon, C.; Walterscheid, R. L.; Hecht, J. H.; Sazykin, S. Y.; Wolf, R.

2017-12-01

We investigate how neutral winds and particle precipitation affect the simulated development of electric fields including Sub-Auroral Polarization Streams (SAPS) during the 17 March 2013 storm. Our approach is to use the magnetically and electrically self-consistent Rice Convection Model - Equilibrium (RCM-E) to simulate the inner magnetospheric electric field. We use parameterized rates of whistler-generated electron pitch-angle scattering from Orlova and Shprits [JGR, 2014] that depend on equatorial radial distance, magnetic activity (Kp), and magnetic local time (MLT) outside the simulated plasmasphere. Inside the plasmasphere, parameterized scattering rates due to hiss [Orlova et al., GRL, 2014] are used. Ions are scattered at a fraction of strong pitch-angle scattering where the fraction is scaled by epsilon, the ratio of the gyroradius to the field-line radius of curvature, when epsilon is greater than 0.1. The electron and proton contributions to the auroral conductance in the RCM-E are calculated using the empirical Robinson et al. [JGR, 1987] and Galand and Richmond [JGR, 2001] equations, respectively. The "background" ionospheric conductance is based on parameters from the International Reference Ionosphere [Bilitza and Reinisch, JASR, 2008] but modified to include the effect of specified ionospheric troughs. Neutral winds are modeled by the empirical Horizontal Wind Model (HWM07) in the RCM-E. We compare simulated precipitating particle energy flux, E x B velocities with DMSP observations during the 17 March 2013 storm with and without the inclusion of neutral winds. Discrepancies between the simulations and observations will aid us in assessing needed improvements in the model.

Substorm topology in the ionosphere and magnetosphere during a flux rope event in the magnetotail

Directory of Open Access Journals (Sweden)

O. Amm

2006-03-01

Full Text Available On 13 August 2002, at ~23:00 UT, about 10 min after a substorm intensification, Cluster observes a flux rope in the central magnetotail, followed by a localised fast flow event about oneminute later. Associated with the flux rope event, a traveling compression region (TCR is seen by those Cluster spacecraft which reside in the lobe. In the conjugate ionospheric region in Northern Scandinavia, the MIRACLE network observes the ionospheric equivalent currents, and the electron densities and electric fields are measured by the EISCAT radar along a meridional scanning profile. Further, the auroral evolution is observed with the Wideband Imaging Camera (WIC on the IMAGE satellite. We compare in detail the substorm evolution as observed in the ionosphere and in the magnetosphere, and examine whether topological correspondences to the flux rope event exist in the ionospheric signatures. The large-scale mapping of both the location and the direction of the flux rope to the ionosphere shows an excellent correspondence to a lens-shaped region of an auroral emission minimum. This region is bracketed by an auroral region equatorward of it which was preexisting to the substorm intensification, and a substorm-related auroral region poleward of it. It is characterised by reduced ionospheric conductances with respect to its environment, and downward field-aligned current (FAC observed both in the magnetosphere and in the ionosphere. As determined from the ionospheric data, this downward FAC area is moving eastward with a speed of ~2 km s-1, in good agreement with the mapped plasma bulk velocity measured at the Cluster satellite closest to that area. Further southwestward to this leading downward FAC area, a trailing upward FAC area is observed that moves eastward with the same speed. The direction of the ionospheric electric field permits a current closure between these two FAC areas through the ionosphere. We speculate that these FAC areas may correspond to

The Earth's magnetosphere is 165 R(sub E) long: Self-consistent currents, convection, magnetospheric structure, and processes for northward interplanetary magnetic field

Science.gov (United States)

Fedder, J. A.; Lyon, J. G.

1995-01-01

The subject of this paper is a self-consistent, magnetohydrodynamic numerical realization for the Earth's magnetosphere which is in a quasi-steady dynamic equilibrium for a due northward interplanetary magnetic field (IMF). Although a few hours of steady northward IMF are required for this asymptotic state to be set up, it should still be of considerable theoretical interest because it constitutes a 'ground state' for the solar wind-magnetosphere interaction. Moreover, particular features of this ground state magnetosphere should be observable even under less extreme solar wind conditions. Certain characteristics of this magnetosphere, namely, NBZ Birkeland currents, four-cell ionospheric convection, a relatively weak cross-polar potential, and a prominent flow boundary layer, are widely expected. Other characteristics, such as no open tail lobes, no Earth-connected magnetic flux beyond 155 R(sub E) downstream, magnetic merging in a closed topology at the cusps, and a 'tadpole' shaped magnetospheric boundary, might not be expected. In this paper, we will present the evidence for this unusual but interesting magnetospheric equilibrium. We will also discuss our present understanding of this singular state.

The influence of solar wind variability on magnetospheric ULF wave power

Directory of Open Access Journals (Sweden)

D. Pokhotelov

2015-06-01

Full Text Available Magnetospheric ultra-low frequency (ULF oscillations in the Pc 4–5 frequency range play an important role in the dynamics of Earth's radiation belts, both by enhancing the radial diffusion through incoherent interactions and through the coherent drift-resonant interactions with trapped radiation belt electrons. The statistical distributions of magnetospheric ULF wave power are known to be strongly dependent on solar wind parameters such as solar wind speed and interplanetary magnetic field (IMF orientation. Statistical characterisation of ULF wave power in the magnetosphere traditionally relies on average solar wind–IMF conditions over a specific time period. In this brief report, we perform an alternative characterisation of the solar wind influence on magnetospheric ULF wave activity through the characterisation of the solar wind driver by its variability using the standard deviation of solar wind parameters rather than a simple time average. We present a statistical study of nearly one solar cycle (1996–2004 of geosynchronous observations of magnetic ULF wave power and find that there is significant variation in ULF wave powers as a function of the dynamic properties of the solar wind. In particular, we find that the variability in IMF vector, rather than variabilities in other parameters (solar wind density, bulk velocity and ion temperature, plays the strongest role in controlling geosynchronous ULF power. We conclude that, although time-averaged bulk properties of the solar wind are a key factor in driving ULF powers in the magnetosphere, the solar wind variability can be an important contributor as well. This highlights the potential importance of including solar wind variability especially in studies of ULF wave dynamics in order to assess the efficiency of solar wind–magnetosphere coupling.

Density Variations in the Earth's Magnetospheric Cusps

Science.gov (United States)

Walsh, B. M.; Niehof, J.; Collier, M. R.; Welling, D. T.; Sibeck, D. G.; Mozer, F. S.; Fritz, T. A.; Kuntz, K. D.

2016-01-01

Seven years of measurements from the Polar spacecraft are surveyed to monitor the variations of plasma density within the magnetospheric cusps. The spacecraft's orbital precession from 1998 through 2005 allows for coverage of both the northern and southern cusps from low altitude out to the magnetopause. In the mid- and high- altitude cusps, plasma density scales well with the solar wind density (n(sub cusp)/n(sub sw) approximately 0.8). This trend is fairly steady for radial distances greater then 4 R(sub E). At low altitudes (r less than 4R(sub E)) the density increases with decreasing altitude and even exceeds the solar wind density due to contributions from the ionosphere. The density of high charge state oxygen (O(greater +2) also displays a positive trend with solar wind density within the cusp. A multifluid simulation with the Block-Adaptive-Tree Solar Wind Roe-Type Upwind Scheme MHD model was run to monitor the relative contributions of the ionosphere and solar wind plasma within the cusp. The simulation provides similar results to the statistical measurements from Polar and confirms the presence of ionospheric plasma at low altitudes.

Application of a global magnetospheric-ionospheric current model for dayside and terminator Pi2 pulsations

Science.gov (United States)

Imajo, S.; Yoshikawa, A.; Uozumi, T.; Ohtani, S.; Nakamizo, A.; Chi, P. J.

2017-12-01

Pi2 magnetic oscillations on the dayside are considered to be produced by the ionospheric current that is driven by Pi2-associated electric fields from the high-latitude region, but this idea has not been quantitatively tested. The present study numerically tested the magnetospheric-ionospheric current system for Pi2 consisting of field-aligned currents (FACs) localized in the nightside auroral region, the perpendicular magnetospheric current flowing in the azimuthal direction, and horizontal ionospheric currents driven by the FACs. We calculated the spatial distribution of the ground magnetic field produced by these currents using the Biot-Savart law in a stationary state. The calculated magnetic field reproduced the observational features reported by previous studies; (1) the sense of the H component does not change a wide range of local time sectors at low latitudes; (2) the amplitude of the H component on the dayside is enhanced at the equator; (3) The D component reverses its phase near the dawn and dusk terminators; (4) the meridian of the D-component phase reversal near the dusk terminator is shifted more sunward than that near the dawn terminator; (5) the amplitude of the D component in the morning is larger than that in the early evening. We also derived the global distributions of observed equivalent currents for two Pi2 events. The spatial patterns of dayside equivalent currents were similar to the spatial pattern of numerically derived equivalent currents. The results indicate that the oscillation of the magnetospheric-ionospheric current system is a plausible explanation of Pi2s on the dayside and near the terminator. These results are included in an accepted paper by Imajo et al. [2017JGR, DOI: 10.1002/2017JA024246].

Observations & modeling of solar-wind/magnetospheric interactions

Science.gov (United States)

Hoilijoki, Sanni; Von Alfthan, Sebastian; Pfau-Kempf, Yann; Palmroth, Minna; Ganse, Urs

2016-07-01

The majority of the global magnetospheric dynamics is driven by magnetic reconnection, indicating the need to understand and predict reconnection processes and their global consequences. So far, global magnetospheric dynamics has been simulated using mainly magnetohydrodynamic (MHD) models, which are approximate but fast enough to be executed in real time or near-real time. Due to their fast computation times, MHD models are currently the only possible frameworks for space weather predictions. However, in MHD models reconnection is not treated kinetically. In this presentation we will compare the results from global kinetic (hybrid-Vlasov) and global MHD simulations. Both simulations are compared with in-situ measurements. We will show that the kinetic processes at the bow shock, in the magnetosheath and at the magnetopause affect global dynamics even during steady solar wind conditions. Foreshock processes cause an asymmetry in the magnetosheath plasma, indicating that the plasma entering the magnetosphere is not symmetrical on different sides of the magnetosphere. Behind the bow shock in the magnetosheath kinetic wave modes appear. Some of these waves propagate to the magnetopause and have an effect on the magnetopause reconnection. Therefore we find that kinetic phenomena have a significant role in the interaction between the solar wind and the magnetosphere. While kinetic models cannot be executed in real time currently, they could be used to extract heuristics to be added in the faster MHD models.

Superstorms of November 2003 and 2004: the role of solar wind driving in the ionosphere-thermosphere dynamics

Science.gov (United States)

Verkhoglyadova, O. P.; Komjathy, A.; Mannucci, A. J.; Mlynczak, M. G.; Hunt, L. A.; Paxton, L. J.

2017-12-01

We revisit three complex superstorms of 19-20 November 2003, 7-8 November 2004 and 9-11 November 2004 to analyze ionosphere-thermosphere (IT) effects driven by different solar wind structures. We distinguish structures associated with ICMEs and their upstream sheaths. The efficiencies of the solar wind-magnetosphere connection throughout the storms are estimated by coupling functions. The daytime IT responses to the complex driving are characterized by combining measurements of characteristic IT parameters. We focus on low- and middle-latitude TEC, global thermospheric infrared nitric oxide emission, composition ratio and locations of the auroral boundary obtained from multiple satellite platforms and ground-based measurements (GPS, TIMED/SABER, TIMED/GUVI, DMSP/SSUSI). A variety of metrics are utilized to examine IT phenomena at 1 hour time scales. It is well-known that the November storm periods featured TEC responses that did not fit a typical pattern. The role of direct driving of IT dynamics by solar wind structures and the role of IT pre-conditioning in these storms are examined to explain the complex unusual ionospheric responses. We identify IT feedback effects that can be important for long-lasting strong storms.

Magnetospheric substorm

International Nuclear Information System (INIS)

Ondoh, Tadanori

1974-01-01

The results of observation of electric field, magnetic field, high energy particles, plasma and aurora on the ground and with artificial satellites during magnetospheric substorm are reviewed, and the problems are mentioned. A new image of magnetospheric substorm is described. The whole description is divided into eight parts. The first part describes the ionospheric electric current and plasma convection accompanying magnetospheric substorm. The variation of geomagnetism during the magnetospheric substorm, the ionospheric equivalent current during the growth and expansion period of substorm, and the relationship between the high energy proton flux of equatorial zone current and peripheral plasma density are illustrated. The second part describes auroral storm. The time variation of aurora observed with a whole sky camera is illustrated. The third part describes the structure of magnetosphere tail. The variation of electron spectrum parameters when the inner edge of plasma sheet passes is illustrated. The fourth part describes the auroral zone of the plasma sheet. The fifth part describes the magnetospheric substorm in magnetosphere tail. The sixth part describes the electric connection of magnetosphere with high latitudinal ionosphere. The seventh part describes interplanet magnetic field and magnetospheric substorm. The eighth part is summary. The ''SC- triggered bay'' accompanied by rapid decrease of X- or H-component occurred frequently immediately after SC in the night side of auroral zone when the rapidstart type magnetic storm at mid- and low-latitudes occurred. The correlation between the Dsub(st) at low latitude and the DS at high latitude during magnetic storm should be reexamined. (Iwakiri, K.)

Vortex, ULF wave and Aurora Observation after Solar Wind Dynamic Pressure Change

Science.gov (United States)

Shi, Q.

2017-12-01

Here we will summarize our recent study and show some new results on the Magnetosphere and Ionosphere Response to Dynamic Pressure Change/disturbances in the Solar Wind and foreshock regions. We study the step function type solar wind dynamic pressure change (increase/decrease) interaction with the magnetosphere using THEMIS satellites at both dayside and nightside in different geocentric distances. Vortices generated by the dynamic pressure change passing along the magnetopause are found and compared with model predictions. ULF waves and vortices are excited in the dayside and nightside plasma sheet when dynamic pressure change hit the magnetotail. The related ionospheric responses, such as aurora and TCVs, are also investigated. We compare Global MHD simulations with the observations. We will also show some new results that dayside magnetospheric FLRs might be caused by foreshock structures.Shi, Q. Q. et al. (2013), THEMIS observations of ULF wave excitation in the nightside plasma sheet during sudden impulse events, J. Geophys. Res. Space Physics, 118, doi:10.1029/2012JA017984. Shi, Q. Q. et al. (2014), Solar wind pressure pulse-driven magnetospheric vortices and their global consequences, J. Geophys. Res. Space Physics, 119, doi:10.1002/2013JA019551. Tian, A.M. et al.(2016), Dayside magnetospheric and ionospheric responses to solar wind pressure increase: Multispacecraft and ground observations, J. Geophys. Res., 121, doi:10.1002/2016JA022459. Shen, X.C. et al.(2015), Magnetospheric ULF waves with increasing amplitude related to solar wind dynamic pressure changes: THEMIS observations, J. Geophys. Res., 120, doi:10.1002/2014JA020913Zhao, H. Y. et al. (2016), Magnetospheric vortices and their global effect after a solar wind dynamic pressure decrease, J. Geophys. Res. Space Physics, 121, doi:10.1002/2015JA021646. Shen, X. C., et al. (2017), Dayside magnetospheric ULF wave frequency modulated by a solar wind dynamic pressure negative impulse, J. Geophys. Res

MAVEN Observations of Magnetic Reconnection on the Dayside Martian Magnetosphere

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DiBraccio, Gina A.; Espley, Jared R.; Connerney, John E. P.; Brain, David A.; Halekas, Jasper S.; Mitchell, David L.; Harada, Yuki; Hara, Takuya

2015-04-01

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission offers a unique opportunity to investigate the complex solar wind-planetary interaction at Mars. The Martian magnetosphere is formed as the interplanetary magnetic field (IMF) drapes around the planet's ionosphere and localized crustal magnetic fields. As the solar wind interacts with this induced magnetosphere, magnetic reconnection can occur at any location where a magnetic shear is present. Reconnection between the IMF and the induced and crustal fields facilitates a direct plasma exchange between the solar wind and the Martian ionosphere. Here we address the occurrence of magnetic reconnection on the dayside magnetosphere of Mars using MAVEN magnetic field and plasma data. When reconnection occurs on the dayside, a non-zero magnetic field component normal to the obstacle, B_N, will result. Using minimum variance analysis, we measure BN by transforming Magnetometer data into boundary-normal coordinates. Selected events are then further examined to identify plasma heating and energization, in the form of Alfvénic outflow jets, using Solar Wind Ion Analyzer measurements. Additionally, the topology of the crustal fields is validated from electron pitch angle distributions provided by the Solar Wind Electron Analyzer. To understand which parameters are responsible for the onset of reconnection, we test the dependency of the dimensionless reconnection rate, calculated from BN measurements, on magnetic field shear angle and plasma beta (the ratio of plasma pressure to magnetic pressure). We assess the global impact of reconnection on Mars' induced magnetosphere by combining analytical models with MAVEN observations to predict the regions where reconnection may occur. Using this approach we examine how IMF orientation and magnetosheath parameters affect reconnection on a global scale. With the aid of analytical models we are able to assess the role of reconnection on a global scale to better understand which

High-latitude observations of impulse-driven ULF pulsations in the ionosphere and on the ground

Directory of Open Access Journals (Sweden)

F. W. Menk

2003-02-01

Full Text Available We report the simultaneous observation of 1.6–1.7 mHz pulsations in the ionospheric F-region with the CUTLASS bistatic HF radar and an HF Doppler sounder, on the ground with the IMAGE and SAMNET magnetometer arrays, and in the upstream solar wind. CUTLASS was at the time being operated in a special mode optimized for high resolution studies of ULF waves. A novel use is made of the ground returns to detect the ionospheric signature of ULF waves. The pulsations were initiated by a strong, sharp decrease in solar wind dynamic pressure near 09:28 UT on 23 February 1996, and persisted for some hours. They were observed with the magnetometers over 20° in latitude, coupling to a field line resonance near 72° magnetic latitude. The magnetic pulsations had azimuthal m numbers ~ -2, consistent with propagation away from the noon sector. The radars show transient high velocity flows in the cusp and auroral zones, poleward of the field line resonance, and small amplitude 1.6–1.7 mHz F-region oscillations across widely spaced regions at lower latitudes. The latter were detected in the radar ground scatter returns and also with the vertical incidence Doppler sounder. Their amplitude is of the order of ± 10 ms-1. A similar perturbation frequency was present in the solar wind pressure recorded by the WIND spacecraft. The initial solar wind pressure decrease was also associated with a decrease in cosmic noise absorption on an imaging riometer near 66° magnetic latitude. The observations suggest that perturbations in the solar wind pressure or IMF result in fast compressional mode waves that propagate through the magnetosphere and drive forced and resonant oscillations of geomagnetic field lines. The compressional wave field may also stimulate ionospheric perturbations. The observations demonstrate that HF radar ground scatter may contain important information on small-amplitude features, extending the scope and capability of these radars to track

A statistical survey of dayside pulsed ionospheric flows as seen by the CUTLASS Finland HF radar

Directory of Open Access Journals (Sweden)

K. A. McWilliams

2000-04-01

Full Text Available Nearly two years of 2-min resolution data and 7- to 21-s resolution data from the CUTLASS Finland HF radar have undergone Fourier analysis in order to study statistically the occurrence rates and repetition frequencies of pulsed ionospheric flows in the noon-sector high-latitude ionosphere. Pulsed ionospheric flow bursts are believed to be the ionospheric footprint of newly reconnected geomagnetic field lines, which occur during episodes of magnetic flux transfer to the terrestrial magnetosphere - flux transfer events or FTEs. The distribution of pulsed ionospheric flows were found to be well grouped in the radar field of view, and to be in the vicinity of the radar signature of the cusp footprint. Two thirds of the pulsed ionospheric flow intervals included in the statistical study occurred when the interplanetary magnetic field had a southward component, supporting the hypothesis that pulsed ionospheric flows are a reconnection-related phenomenon. The occurrence rate of the pulsed ionospheric flow fluctuation period was independent of the radar scan mode. The statistical results obtained from the radar data are compared to occurrence rates and repetition frequencies of FTEs derived from spacecraft data near the magnetopause reconnection region, and to ground-based optical measurements of poleward moving auroral forms. The distributions obtained by the various instruments in different regions of the magnetosphere were remarkably similar. The radar, therefore, appears to give an unbiased sample of magnetopause activity in its routine observations of the cusp footprint.Key words: Magnetospheric physics (magnetosphere-ionosphere interactions; plasma convection; solar wind-magnetosphere interactions

Magnetospheric structure and atmospheric Joule heating of habitable planets orbiting M-dwarf stars

Energy Technology Data Exchange (ETDEWEB)

Cohen, O.; Drake, J. J.; Garraffo, C.; Poppenhaeger, K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Glocer, A. [NASA/GSFC, Code 673, Greenbelt, MD 20771 (United States); Bell, J. M. [Center for Planetary Atmospheres and Flight Sciences, National Institute of Aerospace, Hampton, VA 23666 (United States); Ridley, A. J.; Gombosi, T. I. [Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 (United States)

2014-07-20

We study the magnetospheric structure and the ionospheric Joule Heating of planets orbiting M-dwarf stars in the habitable zone using a set of magnetohydrodynamic models. The stellar wind solution is used to drive a model for the planetary magnetosphere, which is coupled with a model for the planetary ionosphere. Our simulations reveal that the space environment around close-in habitable planets is extreme, and the stellar wind plasma conditions change from sub- to super-Alfvénic along the planetary orbit. As a result, the magnetospheric structure changes dramatically with a bow shock forming in the super-Alfvénic sectors, while no bow shock forms in the sub-Alfvénic sectors. The planets reside most of the time in the sub-Alfvénic sectors with poor atmospheric protection. A significant amount of Joule Heating is provided at the top of the atmosphere as a result of the intense stellar wind. For the steady-state solution, the heating is about 0.1%-3% of the total incoming stellar irradiation, and it is enhanced by 50% for the time-dependent case. The significant Joule Heating obtained here should be considered in models for the atmospheres of habitable planets in terms of the thickness of the atmosphere, the top-side temperature and density, the boundary conditions for the atmospheric pressure, and particle radiation and transport. Here we assume constant ionospheric Pedersen conductance similar to that of the Earth. The conductance could be greater due to the intense EUV radiation leading to smaller heating rates. We plan to quantify the ionospheric conductance in future study.

Plasma sources of solar system magnetospheres

CERN Document Server

Blanc, Michel; Chappell, Charles; Krupp, Norbert

2016-01-01

This volume reviews what we know of the corresponding plasma source for each intrinsically magnetized planet. Plasma sources fall essentially in three categories: the solar wind, the ionosphere (both prevalent on Earth), and the satellite-related sources. Throughout the text, the case of each planet is described, including the characteristics, chemical composition and intensity of each source. The authors also describe how the plasma generated at the source regions is transported to populate the magnetosphere, and how it is later lost. To summarize, the dominant sources are found to be the solar wind and sputtered surface ions at Mercury, the solar wind and ionosphere at Earth (the relative importance of the two being discussed in a specific introductory chapter), Io at Jupiter and – a big surprise of the Cassini findings – Enceladus at Saturn. The situation for Uranus and Neptune, which were investigated by only one fly-by each, is still open and requires further studies and exploration. In the final cha...

Coupled rotational dynamics of Jupiter's thermosphere and magnetosphere

Directory of Open Access Journals (Sweden)

C. G. A. Smith

2009-01-01

Full Text Available We describe an axisymmetric model of the coupled rotational dynamics of the thermosphere and magnetosphere of Jupiter that incorporates self-consistent physical descriptions of angular momentum transfer in both systems. The thermospheric component of the model is a numerical general circulation model. The middle magnetosphere is described by a simple physical model of angular momentum transfer that incorporates self-consistently the effects of variations in the ionospheric conductivity. The outer magnetosphere is described by a model that assumes the existence of a Dungey cycle type interaction with the solar wind, producing at the planet a largely stagnant plasma flow poleward of the main auroral oval. We neglect any decoupling between the plasma flows in the magnetosphere and ionosphere due to the formation of parallel electric fields in the magnetosphere. The model shows that the principle mechanism by which angular momentum is supplied to the polar thermosphere is meridional advection and that mean-field Joule heating and ion drag at high latitudes are not responsible for the high thermospheric temperatures at low latitudes on Jupiter. The rotational dynamics of the magnetosphere at radial distances beyond ~30 RJ in the equatorial plane are qualitatively unaffected by including the detailed dynamics of the thermosphere, but within this radial distance the rotation of the magnetosphere is very sensitive to the rotation velocity of the thermosphere and the value of the Pedersen conductivity. In particular, the thermosphere connected to the inner magnetosphere is found to super-corotate, such that true Pedersen conductivities smaller than previously predicted are required to enforce the observed rotation of the magnetosphere within ~30 RJ. We find that increasing the Joule heating at high latitudes by adding a component due to rapidly fluctuating electric fields is unable to explain the high equatorial temperatures. Adding a component of Joule

Duality of the magnetic flux tube and electric current descriptions magnetospheric plasma and energy flow

International Nuclear Information System (INIS)

Atkinson, G.

1981-01-01

The duality between electric current and magnetic flux tubes is outlined for the magnetosphere. Magnetic flux tubes are regarded as fluid elements subjected to various stresses. Current closure then becomes the dual of stress balance, and Poynting vector energy flow a dual of J x E dissipation. The stresses acting on a flux tube are magnetic stresses, which correspond to currents at a distance, and plasma stresses, which correspond to local currents. The duality between current and stress is traced for ionospheric ion drag forces, solar wind stresses at the magnetopause, inertial effects, and the effects of energetic plasma on flux tubes. The stress balance and dual current systems are outlined for idealized magnetospheres of increasing complexity. For a simple magnetosphere with no convective flow, the balance stresses are solar wind pressure and neutral sheet plasma pressure. The corresponding current systems are the Chapman-Ferraro magnetopause currents and the magetotail current system. The introduction of convective flow introduces further stresses: ionospheric ion drag. Alfven layer shielding, and an imbalance in day-night magnetic stresses due to transport of flux tubes to the nightside by the solar wind. These stresses balance, and hence the corresponding additional currents (the ionospheric Pedersen current and the electrojets, the partial ring current, and two other current systems from the magnetopause and tail) must form a closed current system and do so by the region I and II field-aligned currents of Iijima and Potemra. The energy flow in the above models is described in terms of both Poynting vectors and the above current systems. Temporal variations examined are (1) an increase in dayside merging and/or nightside reconnection, (2) an increase in the energy density of plasma in the plasma sheet, (3) an increase in ionospheric conductivity, and (4) an increase in solar wind pressure

Interhemispheric differences in ionospheric convection: Cluster EDI observations revisited

Science.gov (United States)

Förster, M.; Haaland, S.

2015-07-01

The interaction between the interplanetary magnetic field and the geomagnetic field sets up a large-scale circulation in the magnetosphere. This circulation is also reflected in the magnetically connected ionosphere. In this paper, we present a study of ionospheric convection based on Cluster Electron Drift Instrument (EDI) satellite measurements covering both hemispheres and obtained over a full solar cycle. The results from this study show that average flow patterns and polar cap potentials for a given orientation of the interplanetary magnetic field can be very different in the two hemispheres. In particular during southward directed interplanetary magnetic field conditions, and thus enhanced energy input from the solar wind, the measurements show that the southern polar cap has a higher cross polar cap potential. There are persistent north-south asymmetries, which cannot easily be explained by the influence of external drivers. These persistent asymmetries are primarily a result of the significant differences in the strength and configuration of the geomagnetic field between the Northern and Southern Hemispheres. Since the ionosphere is magnetically connected to the magnetosphere, this difference will also be reflected in the magnetosphere in the form of different feedback from the two hemispheres. Consequently, local ionospheric conditions and the geomagnetic field configuration are important for north-south asymmetries in large regions of geospace.

Ionospheric contribution to the plasma environment in near-earth space

International Nuclear Information System (INIS)

Sharp, R.D.; Lennartsson, W.; Strangeway, R.J.; California Univ., Los Angeles)

1985-01-01

SCATHA and ISEE 1 satellite ion mass spectrometer data on ion composition near GEO are reviewed. The data were gathered during and close to magnetic storm activity to assess the characteristics of ion composition variations in order to predict the effects of hot GEO plasma on spacecraft instruments. Attention is given to both substorms and storms, the former being associated, at high latitudes, with auroral activity, the latter with ring currents. The ionosphere was found to supply hot H(+), O(+) and He(+) ions to the GEO magnetosphere, while the solar wind carried H(+) and He(+) ions. The ionosphere was the dominant source in both quiet and storm conditions in the inner magnetosphere. 11 references

estimation of ionospheric energy dissipation for the year 2012 using

African Journals Online (AJOL)

userpc

energy dissipation is the dominant channel of energy transfer in that year from the solar wind. This is consistent with many results found by other researchers. Keywords: Østgaard's Empirical Relation, Ionospheric Energy Dissipation, Electron. Precipitation, Joule Heating. INTRODUCTION. In the Earth's magnetosphere, the ...

A flux transfer event observed at the magnetopause by the Equator-S spacecraft and in the ionosphere by the CUTLASS HF radar

Directory of Open Access Journals (Sweden)

D. A. Neudegg

1999-06-01

Full Text Available 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.Key words. Interplanetary physics (ionosphere-magnetosphere interaction · Magnetospheric physics (magnetopause · cusp · and boundary layers; solar wind-magnetosphere interactions

ULF Wave Activity in the Magnetosphere: Resolving Solar Wind Interdependencies to Identify Driving Mechanisms

Science.gov (United States)

Bentley, S. N.; Watt, C. E. J.; Owens, M. J.; Rae, I. J.

2018-04-01

Ultralow frequency (ULF) waves in the magnetosphere are involved in the energization and transport of radiation belt particles and are strongly driven by the external solar wind. However, the interdependency of solar wind parameters and the variety of solar wind-magnetosphere coupling processes make it difficult to distinguish the effect of individual processes and to predict magnetospheric wave power using solar wind properties. We examine 15 years of dayside ground-based measurements at a single representative frequency (2.5 mHz) and a single magnetic latitude (corresponding to L ˜ 6.6RE). We determine the relative contribution to ULF wave power from instantaneous nonderived solar wind parameters, accounting for their interdependencies. The most influential parameters for ground-based ULF wave power are solar wind speed vsw, southward interplanetary magnetic field component Bzstill account for significant amounts of power. We suggest that these three parameters correspond to driving by the Kelvin-Helmholtz instability, formation, and/or propagation of flux transfer events and density perturbations from solar wind structures sweeping past the Earth. We anticipate that this new parameter reduction will aid comparisons of ULF generation mechanisms between magnetospheric sectors and will enable more sophisticated empirical models predicting magnetospheric ULF power using external solar wind driving parameters.

On the penetration of solar wind inhomogeneities into the magnetosphere

International Nuclear Information System (INIS)

Maksimov, V.P.; Senatorov, V.N.

1980-01-01

Laboratory experiments were used as a basis to study the process of interaction between solar wind inhomogeneities and the Earth's magnetosphere. The given inhomogeneity represents a lump of plasma characterized by an increased concentration of particles (nsub(e) approximately 20-30 cm -3 ), a discrete form (characteristic dimensions of the lump are inferior to the magnetosphere diameter) and the velocity v approximately 350 km/s. It is shown that there is the possibility of penetration of solar wind inhomogeneities inside the Earth's magnetosphere because of the appearance in the inhomogeneity of an electric field of transverse polarization. The said process is a possible mechanism of the formation of the magnetopshere entrance layer

Dynamics of the Solar Wind Electromagnetic Energy Transmission Into Magnetosphere during Large Geomagnetic Storms

Science.gov (United States)

Kuznetsova, Tamara; Laptukhov, Alexej; Petrov, Valery

Causes of the geomagnetic activity (GA) in the report are divided into temporal changes of the solar wind parameters and the changes of the geomagnetic moment orientation relative directions of the solar wind electric and magnetic fields. Based on our previous study we concluded that a reconnection based on determining role of mutual orientation of the solar wind electric field and geomagnetic moment taking into account effects of the Earth's orbital and daily motions is the most effective compared with existing mechanisms. At present a reconnection as paradigma that has applications in broad fields of physics needs analysis of experimental facts to be developed. In terms of reconnection it is important not only mutual orientation of vectors describing physics of interaction region but and reconnection rate which depends from rate of energy flux to those regions where the reconnection is permitted. Applied to magnetosphere these regions first of all are dayside magnetopause and polar caps. Influence of rate of the energy flux to the lobe magnetopause (based on calculations of the Poyting electromagnetic flux component controlling the reconnection rate along the solar wind velocity Pv) on planetary GA (Dst, Kp indices) is investigated at different phases of geomagnetic storms. We study also the rate of energy flux to the polar caps during storms (based on calculations of the Poyting flux vector component along the geomagnetic moment Pm) and its influence on magnetic activity in the polar ionosphere: at the auroral zone (AU,AL indices). Results allow to evaluate contributions of high and low latitude sources of electromagnetic energy to the storm development and also to clear mechanism of the electromagnetic energy transmission from the solar wind to the magnetosphere. We evaluate too power of the solar wind electromagnetic energy during well-known large storms and compare result with power of the energy sources of other geophysical processes (atmosphere, ocean

The ionospheric contribution to the plasma environment in near-earth space

Science.gov (United States)

Sharp, R. D.; Lennartsson, W.; Strangeway, R. J.

1985-01-01

SCATHA and ISEE 1 satellite ion mass spectrometer data on ion composition near GEO are reviewed. The data were gathered during and close to magnetic storm activity to assess the characteristics of ion composition variations in order to predict the effects of hot GEO plasma on spacecraft instruments. Attention is given to both substorms and storms, the former being associated, at high latitudes, with auroral activity, the latter with ring currents. The ionosphere was found to supply hot H(+), O(+) and He(+) ions to the GEO magnetosphere, while the solar wind carried H(+) and He(+) ions. The ionosphere was the dominant source in both quiet and storm conditions in the inner magnetosphere.

Two-dimensional electric field measurements in the ionospheric footprint of a flux transfer event

Directory of Open Access Journals (Sweden)

K. A. McWilliams

2000-12-01

Full Text Available Line-of-sight Doppler velocities from the SuperDARN CUTLASS HF radar pair have been combined to produce the first two-dimensional vector measurements of the convection pattern throughout the ionospheric footprint of a flux transfer event (a pulsed ionospheric flow, or PIF. Very stable and moderate interplanetary magnetic field conditions, along with a preceding prolonged period of northward interplanetary magnetic field, allow a detailed study of the spatial and the temporal evolution of the ionospheric response to magnetic reconnection. The flux tube footprint is tracked for half an hour across six hours of local time in the auroral zone, from magnetic local noon to dusk. The motion of the footprint of the newly reconnected flux tube is compared with the ionospheric convection velocity. Two primary intervals in the PIF's evolution have been determined. For the first half of its lifetime in the radar field of view the phase speed of the PIF is highly variable and the mean speed is nearly twice the ionospheric convection speed. For the final half of its lifetime the phase velocity becomes much less variable and slows down to the ionospheric convection velocity. The evolution of the flux tube in the magnetosphere has been studied using magnetic field, magnetopause and magnetosheath models. The data are consistent with an interval of azimuthally propagating magnetopause reconnection, in a manner consonant with a peeling of magnetic flux from the magnetopause, followed by an interval of anti-sunward convection of reconnected flux tubes.Key words: Magnetospheric physics (magnetosphere · ionosphere interactions; plasma convection; solar wind · magnetosphere interactions

Modeling of Mutiscale Electromagnetic Magnetosphere-Ionosphere Interactions near Discrete Auroral Arcs Observed by the MICA Sounding Rocket

Science.gov (United States)

Streltsov, A. V.; Lynch, K. A.; Fernandes, P. A.; Miceli, R.; Hampton, D. L.; Michell, R. G.; Samara, M.

2012-12-01

The MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) sounding rocket was launched from Poker Flat on February 19, 2012. The rocket was aimed into the system of discrete auroral arcs and during its flight it detected small-scale electromagnetic disturbances with characteristic features of dispersive Alfvén waves. We report results from numerical modeling of these observations. Our simulations are based on a two-fluid MHD model describing multi-scale interactions between magnetic field-aligned currents carried by shear Alfven waves and the ionosphere. The results from our simulations suggest that the small-scale electromagnetic structures measured by MICA indeed can be interpreted as dispersive Alfvén waves generated by the active ionospheric response (ionopspheric feedback instability) inside the large-scale downward magnetic field-aligned current interacting with the ionosphere.

Rayleigh-Taylor and wind-driven instabilities of the nighttime equatorial ionosphere

International Nuclear Information System (INIS)

Chiu, Y.T.; Straus, J.M.

1979-01-01

We have made a thorough re-examination of the Rayleigh-Taylor instability in the nighttime equatorial ionosphere from approx.100 km to the bottomside F region. We have taken into account explicitly the following effects which have been ignored by other workers in various combinations: (1) The eastward drift of the ionosphere caused by the nighttime polarization electric field, (2) the eastward nighttime neutral wind, and (3) recombination in the F and E regions. We found that, well below the bottomside F region, the Rayleigh-Taylor mode can be unstable and is driven by an eastward neutral wind rather than by gravitational drift. Formation of ionospheric bubbles below the bottomside F region is consistent with the observation of lower ionospheric ions in F region ionospheric holes; furthermore, seasonal and shorter term variations in spread-F occurrence may be associated with variations in the neutral wind and polarization electric field

Magnetospheric storm dynamics in terms of energy output rate

International Nuclear Information System (INIS)

Prigancova, A.; Feldstein, Ya.I.

1992-01-01

Using hourly values of both the global magnetospheric disturbance characteristic DR, and AE index of auroral ionospheric currents during magnetic storm intervals, the energy output rate dynamics is evaluated for a magnetic storm main/recovery phase and a whole storm interval. The magnetospheric response to the solar wind energy input rate under varying interplanetary and magnetospheric conditions is considered from the temporal variability point of view. The peculiarities of the response are traced separately. As far as quantitative characteristics of energy output rate are concerned, the time dependence pattern of the ring current decay parameter is emphasized to be fairly important. It is pointed out that more insight into the plasma processes, especially at L = 3 - 5, is needed for adequate evidence of the dependence. (Author)

Axi-symmetric models of auroral current systems in Jupiter's magnetosphere with predictions for the Juno mission

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S. W. H. Cowley

2008-12-01

Full Text Available We develop two related models of magnetosphere-ionosphere coupling in the jovian system by combining previous models defined at ionospheric heights with magnetospheric magnetic models that allow system parameters to be extended appropriately into the magnetosphere. The key feature of the combined models is thus that they allow direct connection to be made between observations in the magnetosphere, particularly of the azimuthal field produced by the magnetosphere-ionosphere coupling currents and the plasma angular velocity, and the auroral response in the ionosphere. The two models are intended to reflect typical steady-state sub-corotation conditions in the jovian magnetosphere, and transient super-corotation produced by sudden major solar wind-induced compressions, respectively. The key simplification of the models is that of axi-symmetry of the field, flow, and currents about the magnetic axis, limiting their validity to radial distances within ~30 R_J of the planet, though the magnetic axis is appropriately tilted relative to the planetary spin axis and rotates with the planet. The first exploration of the jovian polar magnetosphere is planned to be undertaken in 2016–2017 during the NASA New Frontiers Juno mission, with observations of the polar field, plasma, and UV emissions as a major goal. Evaluation of the models along Juno planning orbits thus produces predictive results that may aid in science mission planning. It is shown in particular that the low-altitude near-periapsis polar passes will generally occur underneath the corresponding auroral acceleration regions, thus allowing brief examination of the auroral primaries over intervals of ~1–3 min for the main oval and ~10 s for narrower polar arc structures, while the "lagging" field deflections produced by the auroral current systems on these passes will be ~0.1°, associated with azimuthal fields above the ionosphere of a few hundred nT.

Interplanetary magnetic field rotations followed from L1 to the ground: the response of the Earth's magnetosphere as seen by multi-spacecraft and ground-based observations

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M. Volwerk

2011-09-01

Full Text Available A study of the interaction of solar wind magnetic field rotations with the Earth's magnetosphere is performed. For this event there is, for the first time, a full coverage over the dayside magnetosphere with multiple (multispacecraft missions from dawn to dusk, combined with ground magnetometers, radar and an auroral camera, this gives a unique coverage of the response of the Earth's magnetosphere. After a long period of southward IMF Bz and high dynamic pressure of the solar wind, the Earth's magnetosphere is eroded and compressed and reacts quickly to the turning of the magnetic field. We use data from the solar wind monitors ACE and Wind and from magnetospheric missions Cluster, THEMIS, DoubleStar and Geotail to investigate the behaviour of the magnetic rotations as they move through the bow shock and magnetosheath. The response of the magnetosphere is investigated through ground magnetometers and auroral keograms. It is found that the solar wind magnetic field drapes over the magnetopause, while still co-moving with the plasma flow at the flanks. The magnetopause reacts quickly to IMF Bz changes, setting up field aligned currents, poleward moving aurorae and strong ionospheric convection. Timing of the structures between the solar wind, magnetosheath and the ground shows that the advection time of the structures, using the solar wind velocity, correlates well with the timing differences between the spacecraft. The reaction time of the magnetopause and the ionospheric current systems to changes in the magnetosheath Bz seem to be almost immediate, allowing for the advection of the structure measured by the spacecraft closest to the magnetopause.

Two-dimensional electric field measurements in the ionospheric footprint of a flux transfer event

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K. A. McWilliams

Full Text Available Line-of-sight Doppler velocities from the SuperDARN CUTLASS HF radar pair have been combined to produce the first two-dimensional vector measurements of the convection pattern throughout the ionospheric footprint of a flux transfer event (a pulsed ionospheric flow, or PIF. Very stable and moderate interplanetary magnetic field conditions, along with a preceding prolonged period of northward interplanetary magnetic field, allow a detailed study of the spatial and the temporal evolution of the ionospheric response to magnetic reconnection. The flux tube footprint is tracked for half an hour across six hours of local time in the auroral zone, from magnetic local noon to dusk. The motion of the footprint of the newly reconnected flux tube is compared with the ionospheric convection velocity. Two primary intervals in the PIF's evolution have been determined. For the first half of its lifetime in the radar field of view the phase speed of the PIF is highly variable and the mean speed is nearly twice the ionospheric convection speed. For the final half of its lifetime the phase velocity becomes much less variable and slows down to the ionospheric convection velocity. The evolution of the flux tube in the magnetosphere has been studied using magnetic field, magnetopause and magnetosheath models. The data are consistent with an interval of azimuthally propagating magnetopause reconnection, in a manner consonant with a peeling of magnetic flux from the magnetopause, followed by an interval of anti-sunward convection of reconnected flux tubes.

Key words: Magnetospheric physics (magnetosphere · ionosphere interactions; plasma convection; solar wind · magnetosphere interactions

Solar wind modulation of the Martian ionosphere observed by Mars Global Surveyor

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J.-S. Wang

2004-06-01

Full Text Available Electron density profiles in the Martian ionosphere observed by the radio occultation experiment on board Mars Global Surveyor have been analyzed to determine if the densities are influenced by the solar wind. Evidence is presented that the altitude of the maximum ionospheric electron density shows a positive correlation to the energetic proton flux in the solar wind. The solar wind modulation of the Martian ionosphere can be attributed to heating of the neutral atmosphere by the solar wind energetic proton precipitation. The modulation is observed to be most prominent at high solar zenith angles. It is argued that this is consistent with the proposed modulation mechanism.

Improving Discoverability Between the Magnetosphere and Ionosphere/Thermosphere Domains

Science.gov (United States)

Schaefer, R. K.; Morrison, D.; Potter, M.; Barnes, R. J.; Talaat, E. R.; Sarris, T.

2016-12-01

With the advent of the NASA Magnetospheric Multiscale Mission and the Van Allen Probes we have space missions that probe the Earth's magnetosphere and radiation belts. These missions fly at far distances from the Earth in contrast to the larger number of near-Earth satellites. Both of the satellites make in situ measurements. Energetic particles flow along magnetic field lines from these measurement locations down to the ionosphere/thermosphere region. Discovering other data that may be used with these satellites is a difficult and complicated process. To solve this problem we have developed a series of light-weight web services that can provide a new data search capability for the Virtual Ionosphere Thermosphere Mesosphere Observatory (VITMO). The services consist of a database of spacecraft ephemerides and instrument fields of view; an overlap calculator to find times when the fields of view of different instruments intersect; and a magnetic field line tracing service that maps in situ and ground based measurements for a number of magnetic field models and geophysical conditions. These services run in real-time when the user queries for data and allow the non-specialist user to select data that they were previously unable to locate, opening up analysis opportunities beyond the instrument teams and specialists. Each service on their own provides a useful new capability for virtual observatories; operating together they will provide a powerful new search tool. The ephemerides service is being built using the Navigation and Ancillary Information Facility (NAIF) SPICE toolkit (http://naif.jpl.nasa.gov) allowing them to be extended to support any Earth orbiting satellite with the addition of the appropriate SPICE kernels. The overlap calculator uses techniques borrowed from computer graphics to identify overlapping measurements in space and time. The calculator will allow a user defined uncertainty to be selected to allow "near misses" to be found. The magnetic field

Phenomena in the ionosphere-magnetosphere system induced by injection of powerful HF radio waves into nightside auroral ionosphere

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N. F. Blagoveshchenskaya

2005-01-01

Full Text Available Experimental results from three ionospheric HF pumping experiments in overdense E or F regions are summarized. The experiments were conducted by the use of the EISCAT HF Heating facility located near Tromsø, Norway, allowing HF pumping the ionosphere in a near geomagnetic field-aligned direction. Distinctive features related to auroral activations in the course of the experiments are identified. Typical features observed in all experiments are the following: generation of scattered components in dynamic HF radio scatter Doppler spectra; strong increase of ion temperatures T_i and local ionospheric electric field E₀; modification of the auroral arc and local spiral-like formation. However, some effects were observed only when the HF pump wave was reflected from the F2 layer. Among them are the generation of intense field-aligned ion outflows, and a strong increase in the electron temperature T_e with altitude. A possible scenario for the substorm triggering due to HF pumping into an auroral ionosphere is discussed. The authors present their interpretation of the data as follows. It is suggested that two populations of charged particles are at play. One of them is the runaway population of electrons and ions from the ionosphere caused by the effects of the powerful HF radio wave. The other is the population of electrons that precipitate from the magnetosphere. It is shown that the hydrodynamical equilibrium was disrupted due to the effects of the HF pumping. We estimate that the parallel electric field can reach values of the order of 30mV/m during substorm triggering.

Interhemispheric differences and solar cycle effects of the high-latitude ionospheric convection patterns deduced from Cluster EDI observations

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Förster, Matthias; Haaland, Stein

2015-04-01

Here, we present a study of ionospheric convection at high latitudes that is based on satellite measurements of the Electron Drift Instrument (EDI) on-board the Cluster satellites, which were obtained over a full solar cycle (2001-2013). The mapped drift measurements are covering both hemispheres and a variety of different solar wind and interplanetary magnetic field (IMF) conditions. The large amount of data allows us to perform more detailed statistical studies. We show that flow patterns and polar cap potentials can differ between the two hemispheres on statistical average for a given IMF orientation. In particular, during southward directed IMF conditions, and thus enhanced energy input from the solar wind, we find that the southern polar cap has a higher cross polar cap potential. We also find persistent north-south asymmetries which cannot be explained by external drivers alone. Much of these asymmetries can probably be explained by significant differences in the strength and configuration of the geomagnetic field between the Northern and Southern Hemisphere. Since the ionosphere is magnetically connected to the magnetosphere, this difference will also be reflected in the magnetosphere in the form of different feedback from the two hemispheres. Consequently, local ionospheric conditions and the geomagnetic field configuration are important for north-south asymmetries in large regions of geospace. The average convection is higher during periods with high solar activity. Although local ionospheric conditions may play a role, we mainly attribute this to higher geomagnetic activity due to enhanced solar wind - magnetosphere interactions.

Global magnetospheric perturbations stimulated by the plasma wave discharge in the lower ionosphere

International Nuclear Information System (INIS)

Markov, G.A.; Chugunov, Yu.V.

1994-01-01

In this paper we discuss a new method of controlled stimulation of global perturbations and the diagnostics of plasma physical processes in the ionosphere and the magnetosphere of the Earth. The method was realized with a series of rocket experiments by means of excitation of the radio frequency plasma wave discharge in the near field of the dipole antenna. We focus considerable attention on the results obtained in these experiments testifying to the wide choice and diversity of potentialities of this new method

Statistical analyses in the study of solar wind-magnetosphere coupling

International Nuclear Information System (INIS)

Baker, D.N.

1985-01-01

Statistical analyses provide a valuable method for establishing initially the existence (or lack of existence) of a relationship between diverse data sets. Statistical methods also allow one to make quantitative assessments of the strengths of observed relationships. This paper reviews the essential techniques and underlying statistical bases for the use of correlative methods in solar wind-magnetosphere coupling studies. Techniques of visual correlation and time-lagged linear cross-correlation analysis are emphasized, but methods of multiple regression, superposed epoch analysis, and linear prediction filtering are also described briefly. The long history of correlation analysis in the area of solar wind-magnetosphere coupling is reviewed with the assessments organized according to data averaging time scales (minutes to years). It is concluded that these statistical methods can be very useful first steps, but that case studies and various advanced analysis methods should be employed to understand fully the average response of the magnetosphere to solar wind input. It is clear that many workers have not always recognized underlying assumptions of statistical methods and thus the significance of correlation results can be in doubt. Long-term averages (greater than or equal to 1 hour) can reveal gross relationships, but only when dealing with high-resolution data (1 to 10 min) can one reach conclusions pertinent to magnetospheric response time scales and substorm onset mechanisms

Magnetospheric signature of some F layer positive storms

International Nuclear Information System (INIS)

Miller, N.J.; Mayr, H.G.; Grebowsky, J.M.; Harris, I.; Tulunay, Y.K.

1981-01-01

Calculations using a self-consistent model of the global thermosphere-ionosphere system perturbed by high-latitude thermospheric heating show that the resultant electron density disturbances within the mid-latitude F layer can propagate upward along magnetic field lines to the equator. The F layer disturbances described by the model calculations correspond to the evolution of enhancements or reductions in electron density that is called the positive or negative phase of an F layer storm. We deduce that the positive phase of dayside F layer storms is initiated when high-latitude thermospheric heating generates equatorward winds. These winds raise the mid-latitude F layer along the geomagnetic field B through momentum transfer from neutral atoms to F layer ons that pull electrons with them. For Lapprox.3 or less the upward movement of ionospheric plasma results in ionization increases at all altitudes along B from the F2 maximum to the equator. An increase in the average magnitude of the equatorial dawn-dusk magnetospheric electric field retards the dayside development of a positive storm phase by drifting plasma away from mid-latitude field lines along which the electron density is increasing. During an F layer storm in June 1972, instruments on Explorer 45 and Ariel 4 detected dayside electron density enhancements simultaneously at 550 km over mid-latitudes and near the equatorial plane in the magnetosphere. These in situ measurements support the model prediction that disturbances in the magnetospheric plasma near the equator can arise through interactions occuring at lower altitudes along a magnetic field line. Our study demonstrates that some storm time enhancements of dayside magnetospheric plasma near Lapprox.2--3 may be signatures of the positive phase of an F layer storm

Ionospheric storms at geophysically-equivalent sites – Part 1: Storm-time patterns for sub-auroral ionospheres

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M. Mendillo

2009-04-01

Full Text Available The systematic study of ionospheric storms has been conducted primarily with groundbased data from the Northern Hemisphere. Significant progress has been made in defining typical morphology patterns at all latitudes; mechanisms have been identified and tested via modeling. At higher mid-latitudes (sites that are typically sub-auroral during non-storm conditions, the processes that change significantly during storms can be of comparable magnitudes, but with different time constants. These include ionospheric plasma dynamics from the penetration of magnetospheric electric fields, enhancements to thermospheric winds due to auroral and Joule heating inputs, disturbance dynamo electrodynamics driven by such winds, and thermospheric composition changes due to the changed circulation patterns. The ~12° tilt of the geomagnetic field axis causes significant longitude effects in all of these processes in the Northern Hemisphere. A complementary series of longitude effects would be expected to occur in the Southern Hemisphere. In this paper we begin a series of studies to investigate the longitudinal-hemispheric similarities and differences in the response of the ionosphere's peak electron density to geomagnetic storms. The ionosonde stations at Wallops Island (VA and Hobart (Tasmania have comparable geographic and geomagnetic latitudes for sub-auroral locations, are situated at longitudes close to that of the dipole tilt, and thus serve as our candidate station-pair choice for studies of ionospheric storms at geophysically-comparable locations. They have an excellent record of observations of the ionospheric penetration frequency (foF2 spanning several solar cycles, and thus are suitable for long-term studies. During solar cycle #20 (1964–1976, 206 geomagnetic storms occurred that had Ap≥30 or Kp≥5 for at least one day of the storm. Our analysis of average storm-time perturbations (percent deviations from the monthly means showed a remarkable

Wind effect on the motion of medium-scale travelling ionospheric disturbances in the E region of the ionosphere

International Nuclear Information System (INIS)

Kikvilashvili, G.B.; Sharadze, Z.S.; Mosashvili, N.V.

1988-01-01

Madium-scale travelling ionospheric disturbances (MSTID) in the ionosphere E region in Tbilisi area are investigated by means of spectral analysis of f 0 E s and f b E s variations, synchronously recorded in the three scattered points. The winds at the E s layers formation heights were measured simultaneously by D1 method in one of these points. It is established, that the MSTID motion direction in summer-time E region is controlled by the background thermospheric winds: disturbances mostly more across and against the wind. Tidal winds make the main contribution into the MSTID rate day variations

IMF By associated interhemispheric asymmetries in ionospheric convection and field-aligned currents

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Kunduri, B.; Baker, J.; Ruohoniemi, J. M.; Clausen, L.; Ribeiro, A.

2012-12-01

The solar wind-magnetosphere interaction plays an important role in controlling the dynamics of ionospheric convection. It is widely known that the By component of IMF generates asymmetries in ionospheric convection between the northern and southern polar caps. Some studies show that IMF By-generated electric field penetrates into the closed magnetosphere producing differences in the high latitude ionospheric convection between hemispheres. The differences in convection were attributed to field-aligned potential drop between hemispheres resulting in flow of interhemispheric field aligned currents. In the current paper we present interhemispheric observations of high latitude ionospheric convection on closed field lines in the noon-dusk sector. The observations reveal that the convection is stronger in the northern (southern) hemisphere when IMF By is positive (negative) irrespective of season. The inter-hemispheric differences can be attributed to the flow of interhemispheric field aligned currents which support the existence of oppositely-directed zonal plasma flows in the closed field line regions, suppressing the convection in one hemisphere and aiding it in the other. We estimate the strength of these currents, analyze their characteristics and identify the various factors such as magnetic local time, magnetic latitude and ionospheric conductivity that impact them.

Dependence of Substorm Evolution on Solar Wind Condition: Simulation Study

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Kamiyoshikawa, N.; Ebihara, Y.; Tanaka, T.

2017-12-01

A substorm is one of the remarkable disturbances occurring in the magnetosphere. It is known that the substorm occurs frequently when IMF is southward and solar wind speed is high. However, the physical process to determine substorm scale is not well understood. We reproduced substorms by using global MHD simulation, calculated auroral electrojet (ionospheric Hall current) flowing in the ionosphere to investigate the dependence of substorm evolution on solar wind condition. Solar wind speed of 372.4 km/s and IMF Bz of 5.0 nT were imposed to, obtain the quasi-stationary state of the magnetosphere. Then the solar wind parameters were changed as a step function. For the solar wind speed, we assumed 300 km/s, 500 km/s and 700 km/s. For IMF, we assumed -1.0 nT, -3.0 nT, -5.0 nT, -7.0 nT and -9.0 nT. In total, 15 simulation runs were performed. In order to objectively evaluate the substorm, the onset was identified with the method based on the one proposed by Newell et al. (2011). This method uses the SME index that is an extension of the AE index. In this study, the geomagnetic variation induced by the ionospheric Hall current was obtained every 1 degree from the magnetic latitude 40 degrees to 80 degrees and in every 0.5 hours in the magnetic region direction. The upper and the lower envelopes of the geomagnetic variation are regarded as SMU index and SML index, respectively. The larger the solar wind speed, the larger the southward IMF, the more the onset tends to be faster. This tendency is consistent with the onset occurrence probability indicated by Newell et al. (2016). Moreover, the minimum value of the SML index within 30 minutes from the beginning of the onset tends to decrease with the solar wind speed and the magnitude of the southward IMF. A rapid decrease of the SML index can be explained by a rapid increase in the field-aligned currents flowing in and out of the nightside ionosphere. This means that electromagnetic energies flowing into the ionosphere

The solar wind plasma density control of night-time auroral particle precipitation

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V. G. Vorobjev

2004-03-01

Full Text Available DMSP F6 and F7 spacecraft observations of the average electron and ion energy, and energy fluxes in different night-time precipitation regions for the whole of 1986 were used to examine the precipitation features associated with solar wind density changes. It was found that during magnetic quietness |AL|<100nT, the enhancement of average ion fluxes was observed at least two times, along with the solar wind plasma density increase from 2 to 24cm–3. More pronounced was the ion flux enhancement that occurred in the b2i–b4s and b4s–b5 regions, which are approximately corresponding to the statistical auroral oval and map to the magnetospheric plasma sheet tailward of the isotropy boundary. The average ion energy decrease of about 2–4kev was registered simultaneously with this ion flux enhancement. The results verify the occurrence of effective penetration of the solar wind plasma into the magnetospheric tail plasma sheet. Key words. Ionosphere (auroral ionosphere, particle precipitation – Magnetospheric physics (solar windmagnetosphere interaction

Solar wind conditions for a quiet magnetosphere

International Nuclear Information System (INIS)

Kerns, K.J.; Gussenhoven, M.S.

1990-01-01

The conditions of the solar wind that lead to a quiet magnetosphere are determined under the assumption that the quiet or baseline magnetosphere can be identified by prolonged periods of low values of the am index. The authors analyzed solar wind data from 1978 to 1984 (7 years) during periods in which am ≤ 3 nT to identify those solar wind parameters that deviate significantly from average values. Parallel studies were also performed for prolonged periods of Kp = 0, 0+ and AE z ) show distinctive variations from average values. They independently varied these solar wind parameters and the length of time the conditions must persist to minimize am. This was done with the additional requirement that the conditions yield a reasonable number of occurrences (5% of the data set). The resulting baseline conditions are V ≤ 390 km/s; 180 degree - arctan |B y /B z | ≤ 101 degree, when b z ≤ 0 (no restriction on B z positive); B ≤ 6.5 nT; and persistence of these conditions for at least 5 hours. Minimizing the am index does not require a clear upper limit on the value of B z as might be anticipated from the work of Gussenhoven (1988) and Berthelier (1980). Apparently, this is a result of the requirement that the conditions must occur 5% of the time. When the requirement is lowered to 1% occurrence, an upper limit to B z emerges

Effects in atmospheric electricity daily variation controlled by solar wind

International Nuclear Information System (INIS)

Ptitsyna, N.G.; Tyasto, M.I.; Levitin, A.E.; Gromova, L.A.; Tuomi, T.; AN SSSR, Moscow

1995-01-01

An analysis of fair weather atmospheric electricity, one of the environmental factors which affects the biosphere, is conducted. A distinct difference in the diurnal variation of atmospheric electric field at Helsinki is found between disturbed and extremely quiet conditions in the magnetosphere in winter before midnight. The comparison with the numerical model of the ionospheric electric field based on the solar wind parameters reveals that the maximum contribution of the magnetospheric-ionospheric generator to atmospheric electric field is about 100-150 v/m which assumes values of about 30% of the surface field. 8 refs.; 2 figs

Energy coupling function and solar wind-magnetosphere dynamo

International Nuclear Information System (INIS)

Kan, J.R.; Lee, L.C.

1979-01-01

The power delivered by the solar wind dynamo to the open magnetosphere is calculated based on the concept of field line reconnection, independent of the MHD steady reconnection theories. By recognizing a previously overlooked geometrical relationship between the reconnection electric field and the magnetic field, the calculated power is shown to be approximately proportional to the Akasofu-Perreault energy coupling function for the magnetospheric substorm. In addition to the polar cap potential, field line reconnection also gives rise to parallel electric fields on open field lines in the high-latitude cusp and the polar cap reions

Solar wind energy transfer through the magnetopause of an open magnetosphere

International Nuclear Information System (INIS)

Lee, L.C.; Roederer, J.G.

1982-01-01

An expression for the total power P/sub T/ transferred from the solar wind to an ''open'' magnetopause with a nonzero normal component of the magnetic field, which is identified as a rotational discontinuity. The total power P/sub T/ consists of (1) the power P/sub EM/ representing the electromagnetic energy transfer and (2) the power P/sub KE/ representing the rate of kinetic energy carried by particles penetrating into the magnetosphere. It is found that P/sub EM/approx. =V/sub SW/ B/sub SW/psi, P/sub KE/approx. =(1/2 M/sub A/-1) P/sub EM/ and P/sub T/approx. =1/2M/sub A/P/sub EM/, where V/sub SW/, B/sub SW/, and M/sub A/ are the velocity, magnetic field, and the Alfven--Mach number in the solar wind, respectively, and Psi is the open magnetic flux in the magnetosphere. The Alfven--Mach number of flow at the magnetopause determines the nature of the local energy transfer; the power per unit area transferred from the solar wind to the magnetosphere consists mainly of kinetic energy. The electromagnetic energy rate P/sub EM/ controls the near-earth magnetospheric activity, whereas the kinetic energy rate P/sub KE/(approx. =3--4 P/sub EM/) should dominate the dynamics of the distant magnetotail

MESSENGER observations of magnetic reconnection in Mercury's magnetosphere.

Science.gov (United States)

Slavin, James A; Acuña, Mario H; Anderson, Brian J; Baker, Daniel N; Benna, Mehdi; Boardsen, Scott A; Gloeckler, George; Gold, Robert E; Ho, George C; Korth, Haje; Krimigis, Stamatios M; McNutt, Ralph L; Raines, Jim M; Sarantos, Menelaos; Schriver, David; Solomon, Sean C; Trávnícek, Pavel; Zurbuchen, Thomas H

2009-05-01

Solar wind energy transfer to planetary magnetospheres and ionospheres is controlled by magnetic reconnection, a process that determines the degree of connectivity between the interplanetary magnetic field (IMF) and a planet's magnetic field. During MESSENGER's second flyby of Mercury, a steady southward IMF was observed and the magnetopause was threaded by a strong magnetic field, indicating a reconnection rate ~10 times that typical at Earth. Moreover, a large flux transfer event was observed in the magnetosheath, and a plasmoid and multiple traveling compression regions were observed in Mercury's magnetotail, all products of reconnection. These observations indicate that Mercury's magnetosphere is much more responsive to IMF direction and dominated by the effects of reconnection than that of Earth or the other magnetized planets.

Superthermal Electron Magnetosphere-Ionosphere Coupling in the Diffuse Aurora in the Presence of ECH Waves

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Khazanov, G. V.; Tripathi, A. K.; Singhal, R. P.; Himwich, Elizabeth; Glocer, A.; Sibeck, D. G.

2015-01-01

There are two main theories for the origin of the diffuse auroral electron precipitation: first, pitch angle scattering by electrostatic electron cyclotron harmonic (ECH) waves, and second, by whistler mode waves. Precipitating electrons initially injected from the plasma sheet to the loss cone via wave-particle interaction processes degrade in the atmosphere toward lower energies and produce secondary electrons via impact ionization of the neutral atmosphere. These secondary electrons can escape back to the magnetosphere, become trapped on closed magnetic field lines, and deposit their energy back to the inner magnetosphere. ECH and whistler mode waves can also move electrons in the opposite direction, from the loss cone into the trap zone, if the source of such electrons exists in conjugate ionospheres located at the same field lines as the trapped magnetospheric electron population. Such a situation exists in the simulation scenario of superthermal electron energy interplay in the region of diffuse aurora presented and discussed by Khazanov et al. (2014) and will be quantified in this paper by taking into account the interaction of secondary electrons with ECH waves.

Multi-Fluid Block-Adaptive-Tree Solar Wind Roe-Type Upwind Scheme: Magnetospheric Composition and Dynamics During Geomagnetic Storms, Initial Results

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Gkocer, A.; Toth, G.; Ma, Y.; Gombosi, T.; Zhang, J. C.; Kistler, L. M.

2010-01-01

The magnetosphere contains a significant amount of ionospheric O{+}, particularly during geomagnetically active times. The presence of ionospheric plasma in the magnetosphere has a notable impact on magnetospheric composition and processes. We present a new multifluid MHD version of the BATS-R-US model of the magnetosphere to track the fate and consequences of ionospheric outflow. The multi-fluid MHD equations are presented as are the novel techniques for overcoming the formidable challenges associated with solving them. Our new model is then applied to the May 4, 1998 and March 31, 2001 geomagnetic storms. The results are juxtaposed with traditional single- fluid MHD and multispecies MHD simulations from a previous study, thereby allowing us to assess the benefits of using a more complex model with additional physics. We find that our multi-fluid MHD model (with outflow) gives comparable results to the multi-species MHD model (with outflow), including a more strongly negative Dst, reduced CPCP, and a drastically improved magnetic field at geosynchronous orbit, as compared to single-fluid MHD with no outflow. Significant differences in composition and magnetic field are found between the multi-species and multi-fluid approach further away from the Earth. We further demonstrate the ability to explore pressure and bulk velocity differences between H{+} and O(+}, which is not possible when utilizing the other techniques considered.

Dawn-dusk asymmetry in particles of solar wind origin within the magnetosphere

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T. J. Stubbs

2001-01-01

Full Text Available Solar wind/magnetosheath plasma in the magnetosphere can be identified using a component that has a higher charge state, lower density and, at least soon after their entry into the magnetosphere, lower energy than plasma from a terrestrial source. We survey here observations taken over 3 years of He2+ ions made by the Magnetospheric Ion Composition Sensor (MICS of the Charge and Mass Magnetospheric Ion Composition Experiment (CAMMICE instrument aboard POLAR. The occurrence probability of these solar wind ions is then plotted as a function of Magnetic Local Time (MLT and invariant latitude (7 for various energy ranges. For all energies observed by MICS (1.8–21.4 keV and all solar wind conditions, the occurrence probabilities peaked around the cusp region and along the dawn flank. The solar wind conditions were filtered to see if this dawnward asymmetry is controlled by the Svalgaard-Mansurov effect (and so depends on the BY component of the interplanetary magnetic field, IMF or by Fermi acceleration of He2+ at the bow shock (and so depends on the IMF ratio BX /BY . It is shown that the asymmetry remained persistently on the dawn flank, suggesting it was not due to effects associated with direct entry into the magnetosphere. This asymmetry, with enhanced fluxes on the dawn flank, persisted for lower energy ions (below a "cross-over" energy of about 23 keV but reversed sense to give higher fluxes on the dusk flank at higher energies. This can be explained by the competing effects of gradient/curvature drifts and the convection electric field on ions that are convecting sunward on re-closed field lines. The lower-energy He2+ ions E × B drift dawnwards as they move earthward, whereas the higher energy ions curvature/ gradient drift towards dusk. The convection electric field in the tail is weaker for northward IMF. Ions then need less energy to drift to the dusk flank, so that the cross-over energy, at which the asymmetry changes sense, is reduced

Inner Magnetospheric Physics

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Gallagher, Dennis

2018-01-01

Outline - Inner Magnetosphere Effects: Historical Background; Main regions and transport processes: Ionosphere, Plasmasphere, Plasma sheet, Ring current, Radiation belt; Geomagnetic Activity: Storms, Substorm; Models.

Modeling Study of the Geospace System Response to the Solar Wind Dynamic Pressure Enhancement on 17 March 2015

Science.gov (United States)

Ozturk, D. S.; Zou, S.; Ridley, A. J.; Slavin, J. A.

2018-04-01

The global magnetosphere-ionosphere-thermosphere system is intrinsically coupled and susceptible to external drivers such as solar wind dynamic pressure enhancements. In order to understand the large-scale dynamic processes in the magnetosphere-ionosphere-thermosphere system due to the compression from the solar wind, the 17 March 2015 sudden commencement was studied in detail using global numerical models. This storm was one of the most geoeffective events of the solar cycle 24 with a minimum Dst of -222 nT. The Wind spacecraft recorded a 10-nPa increment in the solar wind dynamic pressure, while the interplanetary magnetic field BZ became further northward. The University of Michigan Block-Adaptive-Tree Solar wind Roe-type Upwind Scheme global magnetohydrodynamic code was utilized to study the generation and propagation of perturbations associated with the compression of the magnetosphere system. In addition, the high-resolution electric potential and auroral power output from the magnetohydrodynamic model was used to drive the global ionosphere-thermosphere model to investigate the ionosphere-thermosphere system response to pressure enhancement. During the compression, the electric potentials and convection patterns in the polar ionosphere were significantly altered when the preliminary impulse and main impulse field-aligned currents moved from dayside to nightside. As a result of enhanced frictional heating, plasma and neutral temperatures increased at the locations where the flow speeds were enhanced, whereas the electron density dropped at these locations. In particular, the region between the preliminary impulse and main impulse field-aligned currents experienced the most significant heating with 1000-K ion temperature increase and 20-K neutral temperature increase within 2 min. Comparison of the simulation results with the Poker Flat Incoherent Scatter Radar observations showed reasonable agreements despite underestimated magnitudes.

The excitation of plasma convection in the high-latitude ionosphere

International Nuclear Information System (INIS)

Lockwood, M.; Cowley, S.W.H.; Freeman, M.P.

1990-01-01

Recent observations of ionospheric flows by ground-based radars, in particular by the European Incoherent Scatter (EISCAT) facility using the Polar experiment, together with previous analyses of the response of geomagnetic disturbance to variations of the interplanetary magnetic field (IMF), suggest that convection in the high-latitude ionosphere should be considered to be the sum of two intrinsically time-dependent patterns, one driven by solar wind-magnetosphere coupling at the dayside magnetopause, the other by the release of energy in the geomagnetic tail (mainly by dayside and nightside reconnection, respectively). The flows driven by dayside coupling are largest on the dayside, where they usually dominate, are associated with an expanding polar cap area, and are excited and decay on ∼ 10-min time scales following southward and northward turnings of the IMF, respectively. The latter finding indicates that the production of new open flux at the dayside magnetopause excites magnetospheric and ionospheric flow only for a short interval, ∼ 10 min, such that the flow driven by this source subsequently decays on this time scale unless maintained by the production of more open flux tubes. Correspondingly, the flows excited by the release of energy in the tail, mainly during substorms, are largest on the nightside, are associated with a contracting polar cap boundary, and are excited on ∼ 1-hour time scales following a southward turn of the IMF. In general, the total ionospheric flow will be the sum of the flows produced by these two sources, such that due to their different response times to changes in the IMF, considerable variations in the flow pattern can occur for a given direction and strength ofthe IMF. Consequently, the ionospheric electric field cannot generally be regarded as arising from a simple mapping of the solar wind electric field along open flux tubes

Planetary magnetospheres

International Nuclear Information System (INIS)

Hill, T.W.; Michel, F.C.

1975-01-01

Recent planetary probes have resulted in the realization of the generality of magnetospheric interactions between the solar wind and the planets. The three categories of planetary magnetospheres are discussed: intrinsic slowly rotating magnetospheres, intrinsic rapidly rotating magnetospheres, and induced magnetospheres. (BJG)

Solar Illumination Control of the Polar Wind

Science.gov (United States)

Maes, L.; Maggiolo, R.; De Keyser, J.; André, M.; Eriksson, A. I.; Haaland, S.; Li, K.; Poedts, S.

2017-11-01

Polar wind outflow is an important process through which the ionosphere supplies plasma to the magnetosphere. The main source of energy driving the polar wind is solar illumination of the ionosphere. As a result, many studies have found a relation between polar wind flux densities and solar EUV intensity, but less is known about their relation to the solar zenith angle at the ionospheric origin, certainly at higher altitudes. The low energy of the outflowing particles and spacecraft charging means it is very difficult to measure the polar wind at high altitudes. We take advantage of an alternative method that allows estimations of the polar wind flux densities far in the lobes. We analyze measurements made by the Cluster spacecraft at altitudes from 4 up to 20 RE. We observe a strong dependence on the solar zenith angle in the ion flux density and see that both the ion velocity and density exhibit a solar zenith angle dependence as well. We also find a seasonal variation of the flux density.

Electric field effects on ionospheric and thermospheric parameters above the EISCAT station for summer conditions

Directory of Open Access Journals (Sweden)

V. V. Klimenko

1998-10-01

Full Text Available Numerical calculations of the thermospheric and ionospheric parameters above EISCAT are presented for quiet geomagnetic conditions in summer. The Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP was used. The numerical results were obtained both with a self-consistent calculation of the electric fields of magnetospheric and dynamo-action origin and with the magnetospheric electric fields only. It was found that the dynamo-electric field has some effect on the ionospheric convection pattern during quiet geomagnetic conditions. It has a marked effect mainly on the zonal neutral wind component above EISCAT (±20 m/s at 140 km altitude. We have studied the effects of various field-aligned current (FAC distributions on thermosphere/ionosphere parameters and we show that a qualitative agreement can be obtained with region-I and -II FAC zones at 75° and 65° geomagnetic latitude, respectively. The maximum FAC intensities have been assumed at 03–21 MLT for both regions with peak values of 2.5×10–7 A m–2 (region I and 1.25×10–7 A m–2 (region II. These results are in agreement with statistical potential distribution and FAC models constructed by use of EISCAT data. The lack of decreased electron density in the night-time sector as observed by the EISCAT radar was found to be due to the spatial distribution of ionospheric convection resulting from electric fields of magnetospheric origin.Key words. Electric fields and currents · Ionosphere- atmosphere interactions · Modelling and forecasting

Closed model of the earth's magnetosphere

International Nuclear Information System (INIS)

Piddington, J.H.

1979-01-01

The existence of large-scale motions within the earth's magnetosphere and that of a long magnetotail were predicted in 1960 as results of a hypothetical frictional interaction between the solar wind and the geomagnetic field. The boundary layer model of this interaction involves the flow of magnetosheath plasma in a magnetospheric boundary layer. The flow is across magnetic field lines, and so the layer must be polarized, with a space charge field nearly balancing the induction field V x B. The space charge tends to discharge through the ionosphere, thus providing some magnetic and related activity as well as the Lorentz frictional force. This closed magnetosphere model has been largely neglected in favor of the reconnection model but is now strongly supported by observational results and their interpretation as follows. (1) The evidence for the reconnection model, increasing activity with a southward interplanetary field and invasion of the polar caps by flare particles, is shown to be equally compatible with the closed field model. (2) The magnetotail grows by the motions of closed flux tubes through the dawn and dusk meridians, a process which depends on the nature of the boundary between magnetosphere and magnetosheath plasmas and perhaps also on the solar wind dynamo. Both of these features depend, in turn, on the direction of the interplanetary magnetic field. (3) Closed field lines entering the tail may be stretched to a few tens of earth radii and then contract back to the corotating magnetosphere. Others enter the long tail and are stretched to hundreds of earth radii and so are pervious to fast solar particles. (4) A new model of the magnetospheric substorm involves the entry of closed field lines into the tail and their rapid return to the corotating magnetosphere. The return is due, first, to the release of their trapped plasma as it becomes electrically polarized and, second, to mounting magnetic and plasma stresses in the inflated magnetotail

The dependence of magnetosphere-ionosphere system on the Earth's magnetic dipole moment

Science.gov (United States)

Ngwira, C. M.; Pulkkinen, A. A.; Sibeck, D. G.; Rastaetter, L.

2017-12-01

Space weather is increasingly recognized as an international problem affecting several different man-made technologies. The ability to understand, monitor and forecast Earth-directed space weather is of paramount importance for our highly technology-dependent society and for the current rapid developments in awareness and exploration within the heliosphere. It is well known that the strength of the Earth's magnetic field changes over long time scales. We use physics-based simulations with the University of Michigan Space Weather Modeling Framework (SWMF) to examine how the magnetosphere, ionosphere, and ground geomagnetic field perturbations respond as the geomagnetic dipole moment changes. We discuss the implication of these results for our community and the end-users of space weather information.

Recent investigation at INPE in magnetospheric physics and geomagnetism

International Nuclear Information System (INIS)

Gonzales, W.D.; Trivedi, N.B.

1984-01-01

During recent years the following research activities related to the earth's magnetosphere have been intensified: a) studies on electric field and energy transfer from the solar wind to the magnetosphere; b) studies on high latitude magnetospheric electric fields and on their penetration into the plasmasphere; c) measurements of atmospheric-large scale-electric fields, related to the low latitude magnetospheric-ionospheric coupling and to the local atmospheric electrodynamics, using detectors on board stratospheric balloons; and d) measurements of atmospheric X-rays, related to the process of energetic particle precipitation at the South Atlantic Magnetic Anomaly, using detectors also on board stratospheric balloons. Similarly, the following research activities related to geomagnetism are being pursued: a) studies on the variability of the geomagnetic field and on the dynamics of the equatorial electrojet from local geomagnetic field measurements; b) studies on terrestrial electromagnetic induction through local measurements of the geo-electromagnetic field; and c) studies on the influence of geomagnetic activity on particle precipitation at the South Atlantic Magnetic Anomaly. (Author) [pt

Polar ionospheric responses to solar wind IMF changes

Directory of Open Access Journals (Sweden)

Y. Zhang

2000-06-01

Full Text Available Auroral and airglow emissions over Eureka (89° CGM during the 1997-98 winter show striking variations in relation to solar wind IMF changes. The period January 19 to 22, 1998, was chosen for detailed study, as the IMF was particularly strong and variable. During most of the period, Bz was northward and polar arcs were observed. Several overpasses by DMSP satellites during the four day period provided a clear picture of the particle precipitation producing the polar arcs. The spectral character of these events indicated excitation by electrons of average energy 300 to 500 eV. Only occasionally were electrons of average energy up to ~1 keV observed and these appeared transitory from the ground optical data. It is noted that polar arcs appear after sudden changes in IMF By, suggesting IMF control over arc initiation. When By is positive there is arc motion from dawn to dusk, while By is negative the motion is consistently dusk to dawn. F-region (anti-sunward convections were monitored through the period from 630.0 nm emissions. The convection speed was low (100-150 m/s when Bz was northward but increased to 500 m/s after Bz turned southward on January 20.Key words: Atmospheric composition and structure (airglow and aurora - Ionosphere (particle precipitation - Magnetospheric Physics (polar cap phenomena

Interaction of Titan's atmosphere with Saturn's magnetosphere

International Nuclear Information System (INIS)

Hartle, R.E.

1985-01-01

The Voyager 1 measurements made during the Titan flyby reveal that Saturn's rotating magnetospheric plasma interacts directly with Titan's neutral atmosphere and ionosphere. This results from the lack of an intrinsic magnetic field at Titan. The interaction induces a magnetosphere which deflects the flowing plasma around Titan and forms a plasma wake downstream. Within the tail of the induced magnetosphere, ions of ionospheric origin flow away from Titan. Just outside Titan's magnetosphere, a substantial ion-exosphere forms from an extensive hydrogen-nitrogen exosphere. The exospheric ions are picked up and carried downstream into the wake by the plasma flowing around Titan. Mass loading produced by the addition of exospheric ions slows the wake plasma down considerably in the vicinity of the magnetopause. 36 references

Magnetotail processes and their ionospheric signatures

Science.gov (United States)

Ferdousi, B.; Raeder, J.; Zesta, E.; Murphy, K. R.; Cramer, W. D.

2017-12-01

In-situ observations in the magnetotail are sparse and limited to single point measurements. In the ionosphere, on the other hand, there is a broad range of observations, including magnetometers, auroral imagers, and various radars. Since the ionosphere is to some extent a mirror of plasmasheet processes it can be used as a monitor of magnetotail dynamics. Thus, it is of great importance to understand the coupling between the ionosphere and the magnetosphere in order to properly interpret the ionosphere and ground observations in terms of magnetotail dynamics. For this purpose, the global magnetohydrodynamic model OpenGGCM is used to investigate magnetosphere-ionosphere coupling. One of the key processes in magnetotail dynamics are bursty bulk flows (BBFs) which are the major means by which momentum and energy get transferred through the magnetotail and down to the ionosphere. BBFs often manifested in the ionosphere as auroral streamers. This study focuses on mapping such flow bursts from the magnetotail to the ionosphere along the magnetic field lines for three states of the magnetotail: pre-substorm onset through substorm expansion and during steady magnetospheric convection (SMC) following the substorm. We find that the orientation of streamers in the ionosphere differes for different local times, and that, for both tail and ionospheric signatures, activity increases during the SCM configutation compared to the pre-onset and quiet times. We also find that the background convection in the tail impacts the direction and deflection of the BBFs and the subsequent orientation of the auroral streamers in the ionosphere.

Optical observations of Magnetosphere-Ionosphere coupling: Inter-hemispheric electron reflections within pulsating aurora

Science.gov (United States)

Samara, M.; Michell, R.; Khazanov, G. V.; Grubbs, G. A., II

2017-12-01

Magnetosphere-Ionosphere coupling is exhibited in reflected primary and secondary electrons which constitute the second step in the formation of the total precipitating electron distribution. While they have largely been missing from the current theoretical studies of particle precipitation, ground based observations point to the existence of a reflected electron population. We present evidence that pulsating aurora is caused by electrons bouncing back and forth between the two hemispheres. This means that these electrons are responsible for some of the total light in the aurora, a possibility that has largely been ignored in theoretical models. Pulsating auroral events imaged optically at high time resolution present direct observational evidence in agreement with the inter-hemispheric electron bouncing predicted by the SuperThermal Electron Trans-port (STET) model. Immediately following each of the `pulsation-on' times are equally spaced, and subsequently fainter pulsations, which can be explained by the primary precipitating electrons reflecting upwards from the ionosphere, traveling to the opposite hemisphere, and reflecting upwards again. The high time-resolution of these data, combined with the short duration of the `pulsation-on' time ( 1 s) and the relatively long spacing between pulsations ( 6 to 9 s) made it possible to observe the faint optical pulses caused by the reflected electrons coming from the opposite hemisphere. These results are significant and have broad implications because they highlight that the formation of the auroral electron distributions within regions of diffuse and pulsating aurora contain contributions from reflected primary and secondary electrons. These processes can ultimately lead to larger fluxes than expected when considering only the primary injection of magnetospheric electrons.

Dawn-dusk asymmetry in particles of solar wind origin within the magnetosphere

Directory of Open Access Journals (Sweden)

T. J. Stubbs

Full Text Available Solar wind/magnetosheath plasma in the magnetosphere can be identified using a component that has a higher charge state, lower density and, at least soon after their entry into the magnetosphere, lower energy than plasma from a terrestrial source. We survey here observations taken over 3 years of He²⁺ ions made by the Magnetospheric Ion Composition Sensor (MICS of the Charge and Mass Magnetospheric Ion Composition Experiment (CAMMICE instrument aboard POLAR. The occurrence probability of these solar wind ions is then plotted as a function of Magnetic Local Time (MLT and invariant latitude (7 for various energy ranges. For all energies observed by MICS (1.8–21.4 keV and all solar wind conditions, the occurrence probabilities peaked around the cusp region and along the dawn flank. The solar wind conditions were filtered to see if this dawnward asymmetry is controlled by the Svalgaard-Mansurov effect (and so depends on the B_Y component of the interplanetary magnetic field, IMF or by Fermi acceleration of He²⁺ at the bow shock (and so depends on the IMF ratio B_X /B_Y . It is shown that the asymmetry remained persistently on the dawn flank, suggesting it was not due to effects associated with direct entry into the magnetosphere. This asymmetry, with enhanced fluxes on the dawn flank, persisted for lower energy ions (below a "cross-over" energy of about 23 keV but reversed sense to give higher fluxes on the dusk flank at higher energies. This can be explained by the competing effects of gradient/curvature drifts and the convection electric field on ions that are convecting sunward on re-closed field lines. The lower-energy He²⁺ ions E × B drift dawnwards as they move earthward, whereas the higher energy ions curvature/ gradient drift towards dusk. The convection electric field in the tail is weaker for

Modeling and analysis of solar wind generated contributions to the near-Earth magnetic field

DEFF Research Database (Denmark)

Vennerstrøm, Susanne; Moretto, T.; Rastatter, L.

2006-01-01

Solar wind generated magnetic disturbances are currently one of the major obstacles for improving the accuracy in the determination of the magnetic field due to sources internal to the Earth. In the present study a global MHD model of solar wind magnetosphere interaction is used to obtain...... a physically consistent, divergence-free model of ionospheric, field-aligned and magnetospheric currents in a realistic magnetospheric geometry. The magnetic field near the Earth due to these currents is analyzed by estimating and comparing the contributions from the various parts of the system, with the aim...... of identifying the most important aspects of the solar wind disturbances in an internal field modeling context. The contribution from the distant magnetospheric currents is found to consist of two, mainly opposing, contributions from respectively the dayside magnetopause currents and the cross-tail current...

Shear Alfven Wave Injection in the Magnetosphere by Ionospheric Modifications in the Absence of Electrojet Currents

Science.gov (United States)

Papadopoulos, K.; Eliasson, B.; Shao, X.; Labenski, J.; Chang, C.

2011-12-01

A new concept of generating ionospheric currents in the ULF/ELF range with modulated HF heating using ground-based transmitters even in the absence of electrojet currents is presented. The new concept relies on using HF heating of the F-region to modulate the electron temperature and has been given the name Ionospheric Current Drive (ICD). In ICD, the pressure gradient associated with anomalous or collisional F-region electron heating drives a local diamagnetic current that acts as an antenna to inject mainly Magneto-Sonic (MS) waves in the ionospheric plasma. The electric field associated with the MS wave drives Hall currents when it reaches the E region of the ionosphere. The Hall currents act as a secondary antenna that inject waves in the Earth-Ionosphere Waveguide (EIW) below and shear Alfven waves or EMIC waves upwards towards the conjugate regions. The paper presents: (i) Theoretical results using a cold Hall MHD model to study ICD and the generation of ULF/ELF waves by the modulation of the electron pressure at the F2-region with an intense HF electromagnetic wave. The model solves equations governing the dynamics of the shear Alfven and magnetosonic modes, of the damped modes in the diffusive Pedersen layer, and of the weakly damped helicon wave mode in the Hall-dominated E-region. The model incorporates realistic profile of the ionospheric conductivities and magnetic field configuration. We use the model to simulate propagation and dynamics of the low-frequency waves and their injection into the magnetosphere from the HAARP and Arecibo ionospheric heaters. (ii) Proof of principle experiments using the HAARP ionospheric heater in conjunction with measurements by the DEMETER satellite This work is supported by ONR MURI grant and DARPA BRIOCHE Program

Polar cap arcs from the magnetosphere to the ionosphere: kinetic modelling and observations by Cluster and TIMED

Directory of Open Access Journals (Sweden)

R. Maggiolo

2012-02-01

Full Text Available On 1 April 2004 the GUVI imager onboard the TIMED spacecraft spots an isolated and elongated polar cap arc. About 20 min later, the Cluster satellites detect an isolated upflowing ion beam above the polar cap. Cluster observations show that the ions are accelerated upward by a quasi-stationary electric field. The field-aligned potential drop is estimated to about 700 V and the upflowing ions are accompanied by a tenuous population of isotropic protons with a temperature of about 500 eV. The magnetic footpoints of the ion outflows observed by Cluster are situated in the prolongation of the polar cap arc observed by TIMED GUVI. The upflowing ion beam and the polar cap arc may be different signatures of the same phenomenon, as suggested by a recent statistical study of polar cap ion beams using Cluster data. We use Cluster observations at high altitude as input to a quasi-stationary magnetosphere-ionosphere (MI coupling model. Using a Knight-type current-voltage relationship and the current continuity at the topside ionosphere, the model computes the energy spectrum of precipitating electrons at the top of the ionosphere corresponding to the generator electric field observed by Cluster. The MI coupling model provides a field-aligned potential drop in agreement with Cluster observations of upflowing ions and a spatial scale of the polar cap arc consistent with the optical observations by TIMED. The computed energy spectrum of the precipitating electrons is used as input to the Trans4 ionospheric transport code. This 1-D model, based on Boltzmann's kinetic formalism, takes into account ionospheric processes such as photoionization and electron/proton precipitation, and computes the optical and UV emissions due to precipitating electrons. The emission rates provided by the Trans4 code are compared to the optical observations by TIMED. They are similar in size and intensity. Data and modelling results are consistent with the scenario of quasi

Venus magnetosphere

International Nuclear Information System (INIS)

Podgornyj, I.M.

1983-01-01

Some peculiarities of the structure of the Venus magnetosphere are considered. A Swedish scientist H. Alfven supposes that nebular bodies with ionospheric shelles of the type of Venus atmosphere possess induced magnetospheres with dragged magnetic tails. In the Institute of Space Research of the USSR Academy of Sciences experiments on the modelling of such magnetosphere are performed. The possibility of formation of the shock wave in the body with plasma shell in the absence of the proper magnetic shell is proved. The cosmic ''Pioneer-Venus'' equipment is used to obtain such a distribution of the magnetic field depending on the distance to Venus as it was predicted by the laboratory model

The novel programmable riometer for in-depth ionospheric and magnetospheric observations (PRIAMOS) using direct sampling DSP techniques

OpenAIRE

Dekoulis, G.; Honary, F.

2005-01-01

This paper describes the feasibility study and simulation results for the unique multi-frequency, multi-bandwidth, Programmable Riometer for in-depth Ionospheric And Magnetospheric ObservationS (PRIAMOS) based on direct sampling digital signal processing (DSP) techniques. This novel architecture is based on sampling the cosmic noise wavefront at the antenna. It eliminates the usage of any intermediate frequency (IF) mixer stages (-6 dB) and the noise balancing technique (-3 dB), providing a m...

The Structure of Martian Magnetosphere at the Dayside Terminator Region as Observed on MAVEN Spacecraft

Science.gov (United States)

Vaisberg, O. L.; Ermakov, V. N.; Shuvalov, S. D.; Zelenyi, L. M.; Halekas, J.; DiBraccio, G. A.; McFadden, J.; Dubinin, E. M.

2018-04-01

We analyzed 44 passes of the Mars Atmosphere and Volatile EvolutioN mission (MAVEN) spacecraft through the magnetosphere, arranged by the angle between electric field vector and the projection of spacecraft position radius vector in the plane perpendicular to the Mars-Sun line (θE). All passes were divided into three angular sectors near 0°, 90°, and 180° θE angles in order to estimate the role of the interplanetary magnetic field direction in plasma and magnetic properties of dayside Martian magnetosphere. The time interval chosen was from 17 January to 4 February 2016 when MAVEN was crossing the dayside magnetosphere at solar zenith angle 70°. Magnetosphere as the region with prevailing energetic planetary ions is always found between the magnetosheath and the ionosphere. The analysis of dayside interaction region showed that for each angular sector with different orientation of the solar wind electric field vector E = -1/c V × B one can find specific profiles of the magnetosheath, the magnetic barrier (Michel, 1971, https://doi.org/10.1029/RG009i002p00427; Zhang et al., 1991, https://doi.org/10.1029/91JA00088), and the magnetosphere. Magnetic barrier forms in front of the magnetosphere, and relative magnetic field magnitudes in these two domains vary. The average height of the boundary with ionosphere is 530 km, and the average height of the magnetopause is 730 km. We discuss the implications of the observed magnetosphere structure to the planetary ions loss mechanism.

Electric field effects on ionospheric and thermospheric parameters above the EISCAT station for summer conditions

Directory of Open Access Journals (Sweden)

V. V. Klimenko

Full Text Available Numerical calculations of the thermospheric and ionospheric parameters above EISCAT are presented for quiet geomagnetic conditions in summer. The Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP was used. The numerical results were obtained both with a self-consistent calculation of the electric fields of magnetospheric and dynamo-action origin and with the magnetospheric electric fields only. It was found that the dynamo-electric field has some effect on the ionospheric convection pattern during quiet geomagnetic conditions. It has a marked effect mainly on the zonal neutral wind component above EISCAT (±20 m/s at 140 km altitude. We have studied the effects of various field-aligned current (FAC distributions on thermosphere/ionosphere parameters and we show that a qualitative agreement can be obtained with region-I and -II FAC zones at 75^° and 65° geomagnetic latitude, respectively. The maximum FAC intensities have been assumed at 03–21 MLT for both regions with peak values of 2.5×10^–7 A m^–2 (region I and 1.25×10^–7 A m^–2 (region II. These results are in agreement with statistical potential distribution and FAC models constructed by use of EISCAT data. The lack of decreased electron density in the night-time sector as observed by the EISCAT radar was found to be due to the spatial distribution of ionospheric convection resulting from electric fields of magnetospheric origin.

Key words. Electric fields and currents · Ionosphere- atmosphere interactions · Modelling and forecasting

A Study of the Solar Wind-Magnetosphere Coupling Using Neural Networks

Science.gov (United States)

Wu, Jian-Guo; Lundstedt, Henrik

1996-12-01

The interaction between solar wind plasma and interplanetary magnetic field (IMF) and Earth's magnetosphere induces geomagnetic activity. Geomagnetic storms can cause many adverse effects on technical systems in space and on the Earth. It is therefore of great significance to accurately predict geomagnetic activity so as to minimize the amount of disruption to these operational systems and to allow them to work as efficiently as possible. Dynamic neural networks are powerful in modeling the dynamics encoded in time series of data. In this study, we use partially recurrent neural networks to study the solar wind-magnetosphere coupling by predicting geomagnetic storms (as measured by the Dstindex) from solar wind measurements. The solar wind, the IMF and the geomagnetic index Dst data are hourly averaged and read from the National Space Science Data Center's OMNI database. We selected these data from the period 1963 to 1992, which cover 10552h and contain storm time periods 9552h and quiet time periods 1000h. The data are then categorized into three data sets: a training set (6634h), across-validation set (1962h), and a test set (1956h). The validation set is used to determine where the training should be stopped whereas the test set is used for neural networks to get the generalization capability (the out-of-sample performance). Based on the correlation analysis between the Dst index and various solar wind parameters (including various combinations of solar wind parameters), the best coupling functions can be found from the out-of-sample performance of trained neural networks. The coupling functions found are then used to forecast geomagnetic storms one to several hours in advance. The comparisons are made on iterating the single-step prediction several times and on making a non iterated, direct prediction. Thus, we will present the best solar wind-magnetosphere coupling functions and the corresponding prediction results. Interesting Links: Lund Space Weather and AI

Magnetospheric Response Associated With Multiple Atmospheric Reflections of Precipitated Electrons in Aurora.

Science.gov (United States)

Khazanov, G. V.; Merkin, V. G.; Zesta, E.; Sibeck, D. G.; Grubbs, G. A., II; Chu, M.; Wiltberger, M. J.

2017-12-01

The magnetosphere and ionosphere are strongly coupled by precipitating electrons during storm times. Therefore, first principle simulations of precipitating electron fluxes are required to understand storm time variations of ionospheric conductances and related electric fields. As has been discussed by Khazanov et al. [2015 - 2017], the first step in such simulations is initiation of electron precipitation from the Earth's plasma sheet via wave particle interaction processes into both magnetically conjugate points, and the step 2 is the follow up of multiple atmospheric reflections of electron fluxes formed at the boundary between the ionosphere and magnetosphere of two magnetically conjugate points. To demonstrate this effect on the global magnetospheric response the Lyon-Fedder-Mobarry global magnetosphere model coupled with the Rice Convection Model of the inner magnetosphere has been used and run for the geomagnetic storm of 17 March 2013.

Application of dimensional analysis to the problem of solar wind-magnetosphere energy coupling

International Nuclear Information System (INIS)

Bargatze, L.F.; McPherron, R.L.; Baker, D.N.; Hones, E.W. Jr.

1984-01-01

The constraints imposed by dimensional analyses are used to find how the solar wind-magnetosphere energy transfer rate depends upon interplanetary parameters. The analyses reported here assume that only magnetohydrodynamic processes are important in controlling the rate of energy transfer. The study utilizes ISEE-3 solar wind observations, the AE index, and U/sub T/ from three 10-day intervals during the IMS: Simple linear regression and histogram techniques are used to find the value of the MHD coupling exponent, α, which is consistent with observations of magnetospheric response. Once α is estimated, the form of the solar wind energy transfer rate is obtained by substitution into an equation of the interplanetary variables whose exponents depend upon α. 7 references, 6 figures, 1 table

Azimuthal magnetic fields in Saturn’s magnetosphere: effects associated with plasma sub-corotation and the magnetopause-tail current system

Directory of Open Access Journals (Sweden)

E. J. Bunce

Full Text Available We calculate the azimuthal magnetic fields expected to be present in Saturn’s magnetosphere associated with two physical effects, and compare them with the fields observed during the flybys of the two Voyager spacecraft. The first effect is associated with the magnetosphere-ionosphere coupling currents which result from the sub-corotation of the magnetospheric plasma. This is calculated from empirical models of the plasma flow and magnetic field based on Voyager data, with the effective Pedersen conductivity of Saturn’s ionosphere being treated as an essentially free parameter. This mechanism results in a ‘lagging’ field configuration at all local times. The second effect is due to the day-night asymmetric confinement of the magnetosphere by the solar wind (i.e. the magnetopause and tail current system, which we have estimated empirically by scaling a model of the Earth’s magnetosphere to Saturn. This effect produces ‘leading’ fields in the dusk magnetosphere, and ‘lagging’ fields at dawn. Our results show that the azimuthal fields observed in the inner regions can be reasonably well accounted for by plasma sub-corotation, given a value of the effective ionospheric Pedersen conductivity of ~ 1–2 mho. This statement applies to field lines mapping to the equator within ~ 8 R_S (1 R_S is taken to be 60 330 km of the planet on the dayside inbound passes, where the plasma distribution is dominated by a thin equatorial heavy-ion plasma sheet, and to field lines mapping to the equator within ~ 15 R_S on the dawn side outbound passes. The contributions of the magnetopause-tail currents are estimated to be much smaller than the observed fields in these regions. If, however, we assume that the azimuthal fields observed in these regions are not due to sub-corotation but to some other process, then the above effective conductivities define an upper limit, such that values above ~ 2 mho can definitely be

Electric fields in the magnetosphere

International Nuclear Information System (INIS)

Faelthammar, C.G.

1989-12-01

The electric field plays an important role in the complex plasma system called the magnetosphere. In spite of this, direct measurement of this quantity are still scarce except in its lowest-altitude part, i.e. the ionosphere. The large scale ionospheric electric field has been determined from measurement on the ground and in low satellite orbit. For most of the magnetosphere, our concepts of the electric field have mostly been based on theoretical considerations and extrapolations of the ionspheric electric field. Direct, in situ, electric field measurements in the outer parts of the magnetosphere have been made only relatively recently. A few satellite missions. most recently the Viking mission, have extended the direct empirical knowledge so as to include major parts of the magnetosphere. These measurements have revealed a number of unexpected features. The actual electric field has been found to have unexpectedly strong space and time variations, which reflect the dynamic nature of the system. Examples are give of measured electric fields in the plasmasphere, the plasmasheet, the neutral sheet, the magnetotail, the flanks of the magnetosphere, the dayside magnetopause and the auroral acceleration region. (author)

Parallel electric fields from ionospheric winds

International Nuclear Information System (INIS)

Nakada, M.P.

1987-01-01

The possible production of electric fields parallel to the magnetic field by dynamo winds in the E region is examined, using a jet stream wind model. Current return paths through the F region above the stream are examined as well as return paths through the conjugate ionosphere. The Wulf geometry with horizontal winds moving in opposite directions one above the other is also examined. Parallel electric fields are found to depend strongly on the width of current sheets at the edges of the jet stream. If these are narrow enough, appreciable parallel electric fields are produced. These appear to be sufficient to heat the electrons which reduces the conductivity and produces further increases in parallel electric fields and temperatures. Calculations indicate that high enough temperatures for optical emission can be produced in less than 0.3 s. Some properties of auroras that might be produced by dynamo winds are examined; one property is a time delay in brightening at higher and lower altitudes

Influence of the solar wind and IMF on Jupiter's magnetosphere: Results from global MHD simulations

Science.gov (United States)

Sarkango, Y.; Jia, X.; Toth, G.; Hansen, K. C.

2017-12-01

Due to its large size, rapid rotation and presence of substantial internal plasma sources, Jupiter's magnetosphere is fundamentally different from that of the Earth. How and to what extent do the external factors, such as the solar wind and interplanetary magnetic field (IMF), influence the internally-driven magnetosphere is an open question. In this work, we solve the 3D semi-relativistic magnetohydrodynamic (MHD) equations using a well-established code, BATSRUS, to model the Jovian magnetosphere and study its interaction with the solar wind. Our global model adopts a non-uniform mesh covering the region from 200 RJ upstream to 1800 RJ downstream with the inner boundary placed at a radial distance of 2.5 RJ. The Io plasma torus centered around 6 RJ is generated in our model through appropriate mass-loading terms added to the set of MHD equations. We perform systematic numerical experiments in which we vary the upstream solar wind properties to investigate the impact of solar wind events, such as interplanetary shock and IMF rotation, on the global magnetosphere. From our simulations, we extract the location of the magnetopause boundary, the bow shock and the open-closed field line boundary (OCB), and determine their dependence on the solar wind properties and the IMF orientation. For validation, we compare our simulation results, such as density, temperature and magnetic field, to published empirical models based on in-situ measurements.

Transient plasma injections in the dayside magnetosphere: one-to-one correlated observations by Cluster and SuperDARN

Directory of Open Access Journals (Sweden)

A. Marchaudon

2004-01-01

Full Text Available Conjunctions in the cusp between the four Cluster spacecraft and SuperDARN ground-based radars offer unique opportunities to compare the signatures of transient plasma injections simultaneously in the high-altitude dayside magnetosphere and in the ionosphere. We report here on such observations on 17 March 2001, when the IMF initially northward and duskward, turns southward and dawnward for a short period. The changes in the convection direction at Cluster are well correlated with the interplanetary magnetic field (IMF By variations. Moreover, the changes in the ionosphere follow those in the magnetosphere, with a 2–3min delay. When mapped into the ionosphere, the convection velocity at Cluster is about 1.5 times larger than measured by SuperDARN. In the high-altitude cusp, field and particle observations by Cluster display the characteristic signatures of plasma injections into the magnetosphere suggestive of Flux Transfer Events (FTEs. Simultaneous impulsive and localized convection plasma flows are observed in the ionospheric cusp by the HF radars. A clear one-to-one correlation is observed for three successive injections, with a 2–3min delay between the magnetospheric and ionospheric observations. For each event, the drift velocity of reconnected flux tubes (phase velocity has been compared in the magnetosphere and in the ionosphere. The drift velocity measured at Cluster is of the order of 400–600ms–1 when mapped into the ionosphere, in qualitative agreement with SuperDARN observations. Finally, the reconnected flux tubes are elongated in the north-south direction, with an east-west dimension of 30–60km in the ionosphere from mapped Cluster observations, which is consistent with SuperDARN observations, although slightly smaller. Key words. Ionosphere (plasma convection – Magnetospheric physics (magnetopause, cusp, and boundary layers; magnetosphere-ionosphere interactions

The importance of ground magnetic data in specifying the state of magnetosphere-ionosphere coupling: a personal view

Science.gov (United States)

Kamide, Y.; Balan, Nanan

2016-12-01

In the history of geomagnetism, geoelectricity and space science including solar terrestrial physics, ground magnetic records have been demonstrated to be a powerful tool for monitoring the levels of overall geomagnetic activity. For example, the Kp and ap indices having perhaps the long-history geomagnetic indices have and are being used as space weather parameters, where "p" stands for "planetary" implying that these indices express average geomagnetic disturbances on the entire Earth in a planetary scale. To quantify the intensity level of geomagnetic storms, however, it is common to rely on the Dst index, which is supposed to show the magnitude of the storm-time ring current. Efforts were also made to inter-calibrate various activity indices. Different indices were proposed to express different aspects of a phenomenon in the near-Earth space. In the early 1980s, several research groups in Japan, Russia, Europe and the US developed the so-called magnetogram-inversion techniques, which were proposed all independently. Subsequent improvements of the magnetogram-inversion algorithms allowed their technology to be applied to a number of different datasets for magnetospheric convection and substorms. In the present review, we demonstrate how important it was to make full use of ground magnetic data covering a large extent in both latitudinal and longitudinal directions. It is now possible to map a number of electrodynamic parameters in the polar ionosphere on an instantaneous basis. By applying these new inverse methods to a number of ground-based geomagnetic observations, it was found that two basic elements in spatial patterns can be viewed as two physical processes for solar wind-magnetosphere energy coupling.

Computer-simulation movie of ionospheric electric fields and currents for a magnetospheric substorm life cycle. Technical note

International Nuclear Information System (INIS)

Kamide, Y.; Matsushita, S.

1980-07-01

Numerical solution of the current conservation equation gives the distributions of electric fields and currents in the global ionosphere produced by the field-aligned currents. By altering ionospheric conductivity distributions as well as the field-aligned current densities and configurations to simulate a magnetospheric substorm life cycle, which is assumed to last for five hours, various patterns of electric fields and currents are computed for every 30-second interval in the life cycle. The simulated results are compiled in the form of a color movie, where variations of electric equi-potential curves are the first sequence, electric current-vector changes are the second, and fluctuations of the electric current system are the third. The movie compresses real time by a factor of 1/180, taking 1.7 minutes of running time for one sequence. One of the most striking features of this simulation is the clear demonstration of rapid and large scale interactions between the auroral zone and middle-low latitudes during the substorm sequences. This technical note provides an outline of the numerical scheme and world-wide contour maps of the electric potential, ionospheric current vectors, and the equivalent ionospheric current system at 5-minute intervals as an aid in viewing the movie and to further detailed study of the 'model' substorms

3-D Force-balanced Magnetospheric Configurations

International Nuclear Information System (INIS)

Sorin Zaharia; Cheng, C.Z.; Maezawa, K.

2003-01-01

The knowledge of plasma pressure is essential for many physics applications in the magnetosphere, such as computing magnetospheric currents and deriving magnetosphere-ionosphere coupling. A thorough knowledge of the 3-D pressure distribution has however eluded the community, as most in-situ pressure observations are either in the ionosphere or the equatorial region of the magnetosphere. With the assumption of pressure isotropy there have been attempts to obtain the pressure at different locations by either (a) mapping observed data (e.g., in the ionosphere) along the field lines of an empirical magnetospheric field model or (b) computing a pressure profile in the equatorial plane (in 2-D) or along the Sun-Earth axis (in 1-D) that is in force balance with the magnetic stresses of an empirical model. However, the pressure distributions obtained through these methods are not in force balance with the empirical magnetic field at all locations. In order to find a global 3-D plasma pressure distribution in force balance with the magnetospheric magnetic field, we have developed the MAG-3D code, that solves the 3-D force balance equation J x B = (upside-down delta) P computationally. Our calculation is performed in a flux coordinate system in which the magnetic field is expressed in terms of Euler potentials as B = (upside-down delta) psi x (upside-down delta) alpha. The pressure distribution, P = P(psi,alpha), is prescribed in the equatorial plane and is based on satellite measurements. In addition, computational boundary conditions for y surfaces are imposed using empirical field models. Our results provide 3-D distributions of magnetic field and plasma pressure as well as parallel and transverse currents for both quiet-time and disturbed magnetospheric conditions

Effects of electric field methods on modeling the midlatitude ionospheric electrodynamics and inner magnetosphere dynamics

Science.gov (United States)

Yu, Yiqun; Jordanova, Vania K.; Ridley, Aaron J.; Toth, Gabor; Heelis, Roderick

2017-05-01

We report a self-consistent electric field coupling between the midlatitude ionospheric electrodynamics and inner magnetosphere dynamics represented in a kinetic ring current model. This implementation in the model features another self-consistency in addition to its already existing self-consistent magnetic field coupling with plasma. The model is therefore named as Ring current-Atmosphere interaction Model with Self-Consistent magnetic (B) and electric (E) fields, or RAM-SCB-E. With this new model, we explore, by comparing with previously employed empirical Weimer potential, the impact of using self-consistent electric fields on the modeling of storm time global electric potential distribution, plasma sheet particle injection, and the subauroral polarization streams (SAPS) which heavily rely on the coupled interplay between the inner magnetosphere and midlatitude ionosphere. We find the following phenomena in the self-consistent model: (1) The spatially localized enhancement of electric field is produced within 2.5 penetration as found in statistical observations. (2) The electric potential contours show more substantial skewing toward the postmidnight than the Weimer potential, suggesting the resistance on the particles from directly injecting toward the low-L region. (3) The proton flux indeed indicates that the plasma sheet inner boundary at the dusk-premidnight sector is located further away from the Earth than in the Weimer potential, and a "tongue" of low-energy protons extends eastward toward the dawn, leading to the Harang reversal. (4) SAPS are reproduced in the subauroral region, and their magnitude and latitudinal width are in reasonable agreement with data.

The Influence of Magnetosheath Beta and Ionospheric Conductivity in the Structure of the Lobes Near Solstice

Science.gov (United States)

Wilder, F. D.; Eriksson, S.; Wiltberger, M. J.

2017-12-01

The saturation of the cross-polar cap potential (CPCP) is an unexplained phenomenon in magnetosphere-ionosphere system science. In the present study, we expand upon the Alfvén Wing model of CPCP saturation by investigating its impact on the magnetosphere-ionosphere current system, particularly the cusp-mantle dynamo associated with lobe field lines. In this expansion of the Alfven wing model, the ability of open flux tubes to deform in response to the fluid stress from the magnetosheath is governed by the magnetosheath plasma beta, which in turn reduces the Maxwell stress imposed on the ionospheric plasma to accelerate it against ion-neutral collisional drag. We perform 32 simulations using the Lyon-Fedder-Mobarry (LFM) Magnetohydrodynamic (MHD) model with varying solar wind density and IMF strength, as well as a dipole tilt of 25 degrees to investigate the relative importance of both magnetosheath plasma beta and ionospheric conductivity in the formation of Alfvén wing-like structures and the saturation of the CPCP. We find that the plasma beta in the magnetosheath is different in each hemisphere and dependent on the stagnation point location. We also show that the lobes become more bent in the summer hemisphere with higher ionospheric conductivity. We find that higher ionospheric conductivity also makes the summer hemisphere lobes more sensitive to changes in the magnetosheath beta.

Solar wind parameters responsible for the plasma injection into the magnetospheric ring current region

International Nuclear Information System (INIS)

Bobrov, M.S.

1977-01-01

Solar wind effect on the magnetospheric ring-current region has been considered. The correlations with solar wind parameters of the magnitude qsub(o) proportional to the total energy of particles being injected into the magnetospheric ring-current region per one hour are studied statistically and by comparison of time variations. The data on 8 sporadic geomagnetic storms of various intensity, from moderate to very severe one, are used. It is found that qsub(o) correlates not only with the magnitude and the direction of the solar-wind magnetic field component normal to the ecliptic plane, Bsub(z), but also with the variability, sigmasub(B), of the total magnetic-field strength vector. The solar-wind flux velocity ν influences the average storm intensity but the time variations of ν during any individual storm do not correlate with those of qsub(o)

On the influence of the magnetization of a model solar wind on a laboratory magnetosphere

International Nuclear Information System (INIS)

Rahman, H.U.; Yur, G.; White, R.S.; Birn, J.; Wessel, F.J.

1991-01-01

The interaction of a magnetized plasma beam with a stationary dipole field, analogous to the interaction of the solar wind with the Earth's magnetosphere, is explored in a laboratory experiment. Experimental parameters are chosen to scale qualitatively similar to the parameters in the Earth's magnetosphere. The authors find that the magnetization of the laboratory solar wind, generated by injecting a plasma across a preexisting magnetic field, requires a certain minimum magnetic field strength. Differences between the resulting magnetospheres for northward and southward solar wind or interplanetary magnetic fields (IMF) are demonstrated by global pictures and by magnetic field measurements above the north polar region. These measurements show patterns of the variation of the transverse field component which are similar to those found by satellite measurements above the Earth. This indicates the presence of similar field-aligned current systems. They demonstrate particularly the presence (for northward IMF) and absence (for southward IMF) of the pattern attributed to the NBZ (northward B z ) current system

Computer simulation of inner magnetospheric dynamics for the magnetic storm of July 29, 1977

International Nuclear Information System (INIS)

Wolf, R.A.; Harel, M.; Spiro, R.W.; Voigt, G.; Reiff, P.H.; Chen, C.

1982-01-01

We present preliminary results of applying the Rice convection model to the early main phase of the magnetic storm of July 29, 1977. The computer model self-consistently computes electric fields and currents, as well as plasma distributions and velocities, in the inner-magnetosphere/ionosphere system. In the equatorial plane, the region modeled includes geocentric distances less than about the magnetopause standoff distance. Particle loss, parallel electric fields, and neutral winds are neglected. On the basis of solar wind parameters and the AL index as input, the model predicts the injection of plasma-sheet plasma to form a substantial storm time ring current. The total strength of the model-predicted ring current agrees accurately with the observed Dst index. Comparison of the model results with electric fields and Birkeland currents measured by S3-3 shows qualitative agreement but interesting quantitative discrepancies. During this event, region 1 currents, which in standard convection theory would connect to the outer magnetosphere, are observed as low as 60 0 invariant latitude at dawn and dusk. We examine the possibility that the magnetic field might be so highly inflated that 60 0 field lines extend to the outer magnetosphere. In the model, distortion of the inner edge of the plasma sheet by the magnetospheric compression associated with the sudden commencement temporarily disturbs the normal Birkeland-current pattern. The normal tendency for the plasma sheet's inner edge to shield low L alues from the convection electric field is also temporarily disrupted. Normal Birkeland currents and shielding reassert themselves after about an hour. Time-integrated Joule heating in the model ionosphere over the first 5.5 hours of the storm main phase is about half the increase in model ring-current energy

Upstream pressure variations associated with the bow shock and their effects on the magnetosphere

International Nuclear Information System (INIS)

Fairfield, D.H.; Baumjohann, W.; Paschmann, G.; Luehr, H.; Sibeck, D.G.

1990-01-01

Magnetic field enhancements and depressions on the time scales of minutes were frequently observed simultaneously by the AMPTE CCE, GOES 5, and GOES 6 spacecraft in the subsolar magnetosphere. The source of these perturbations has been detected in the high time resolution AMPTE IRM measurements of the kinetic pressure of the solar wind upstream of the bow shock. It is argued that these upstream pressure variations are not inherent in the solar wind but rather are associated with the bow shock. This conclusion follows from the facts that (1) the upstream field strength and the density associated with the perturbations are highly correlated with each other whereas these quantities tend to be anticorrelated in the undisturbed solar wind, and (2) the upstream perturbations occur within the foreshock or at its boundary. The results imply a mode of interaction between the solar wind and the magnetosphere whereby density changes produced in the foreshock subsequently convect through the bow shock and impinge on the magnetosphere. Also velocity decreases deep within the foreshock sometimes reach many tens of kilometers per second and may be associated with further pressure variations as a changing interplanetary field direction changes the foreshock geometry. Upstream pressure perturbations should create significant effects on the magnetopause and at the foot of nearby field lines that lead to the polar cusp ionosphere

Sub-corotating region of Saturn's magnetosphere: Cassini observations of the azimuthal field and implications for the ionospheric Pederesen Current (Invited)

Science.gov (United States)

Smith, E. J.; Dougherty, M. K.; Zhou, X.

2010-12-01

A consensus model of Saturn’s magnetosphere that has broad acceptance consists of four regions in which the plasma and field are corotating, sub-corotating or undergoing Vasyliunas or Dungey convection. In this model, the sub-corotating magnetosphere contains a large scale circuital current system comprised of radial, field-aligned and ionospheric currents. A quantitative rendering of this system developed by S. Cowley and E. Bunch relates the azimuthal field component, B phi, that causes the field to spiral to the ionospheric Pedersen current , Ip. Cassini measurements of B phi over the four year interval between 2005 and 2008 that are widely distributed in radial distance, latitude and local time have been used to compute Ip from a Bunce-Cowley formula. A striking north-south asymmetry of the global magnetosphere has been found. In the southern hemisphere, the magnitude and variation of Ip with invariant colatitude, θ, agree qualitatively with the model but Ip (θ) is shifted poleward by about 10°. In the northern hemisphere, however, the data fail to reproduce the profile of Ip (θ) predicted by the model but are dominated by two high latitude currents having the wrong polarities. Possible causes of this asymmetry are seasonal variations (summer in the southern hemisphere) and/or asymmetric plasma outflow from the inner magnetosphere such as the plumes extending southward from Enceladus. Another finding is a significant local time dependence of Ip(θ) rather than the axisymmetry assumed in the model. There is a close correspondence with the model in the noon sector. The currents in the midnight and dawn sectors are significantly larger than in the noon sector and the current in the dusk sector is dramatically weaker.

Influence of Magnetic Topology on Mars' Ionospheric Structure

Science.gov (United States)

Adams, D.; Xu, S.; Mitchell, D. L.; Fillingim, M. O.; Lillis, R. J.; Andersson, L.; Fowler, C. M.; Benna, M.; Connerney, J. E. P.; Elrod, M. K.; Girazian, Z.; Vogt, M.

2017-12-01

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has been in Mars' orbit since September 2014 (>1 Mars year), and has collected particle and field data within the ionosphere over wide ranges of altitudes, latitudes, and local times. This study uses MAVEN data to (1) analyze the influence of magnetic topology on the day-side ionosphere and (2) identify the sources of the night-side ionosphere. On the day side, magnetic strength and elevation angle are commonly used as proxies for magnetic topology. In this study, we use pitch-angle-resolved suprathermal electron measurements by the Solar Wind Electron Analyzer (SWEA) to directly deduce the magnetic topology instead of using a proxy. On the night side, the main sources of ionospheric plasma are bulk transport and plasma pressure gradient flow from the day side, as well as in situ production by electron impact ionization (EII). Plasma transport at Mars is complicated by the presence of intense crustal magnetic fields. Closed crustal magnetic fields form isolated plasma environments ("miniature magnetospheres") that inhibit external sources of cold ionospheric plasma as well as suprathermal (ionizing) electrons. Inside these closed magnetic loops, we study how the plasma evolves with bulk flow transport as the only source. By comparing closed and non-closed magnetic configurations, the effects of pressure gradient flow and EII can be distinguished. Finally, the densities of O2+, O+, and NO+, as measured by the Neutral Gas and Ion Mass Spectrometer (NGIMS), are examined. Inside miniature magnetospheres on the night side, the abundances of these species are found to be primarily controlled by the different recombination rates, as there is little plasma created within these regions by EII or transported from the neighboring regions by plasma pressure gradient flow.

Outstanding Issues and Future Directions of Inner Magnetospheric Research (Invited)

Science.gov (United States)

Brandt, P. C.

2009-12-01

Several research areas of the inner magnetosphere and ionosphere (MI) system have reached a state, where the coupling mechanisms can no longer be treated as boundary conditions or ad-hoc assumptions in our physical models. It is nothing new that our community has become increasingly aware of the necessity to use global measurements from multiple observation platforms and missions, in order to understand both the system as a whole as well as its individual subsystems. In this presentation we briefly review the current status and outstanding issues of inner MI research. We attempt to establish a working definition of the term "Systems Approach", then present observational tools and techniques that enable such an approach. Physical modeling plays a central role not only in understanding the mechanisms at work, but also in determining the key quantities to be measured. We conclude by discussing questions relevant to future directions. Are there new techniques that need more attention? Should multi-platform observations be included as a default component already at the mission-level in the future? Is solar minimum uninteresting from an MI perspective? Should we actively compare to magnetospheres of other planets? Examples of outstanding issues in inner MI research include the circulation of ionospheric plasma from low to high latitudes and its escape to the magnetosphere, where it is energized by magnetospheric processes and becomes a part of the plasma pressure that in turn affects the ionospheric and magnetospheric electric field. The electric field, in turn, plays a controlling role in the transport of both magnetospheric and ionospheric plasma, which is intimately linked with ionospheric conductance. The conductance, in turn, is controlled by thermospheric chemistry coupled with plasma flow and heating and magnetospheric precipitation and Joule heating. Several techniques have emerged as important tools: auroral imaging, inversions of ENA images to retrieve the

Compression of Jupiter's magnetosphere by the solar wind: Reexamination via MHD simulation of evolving corotating interaction regions

International Nuclear Information System (INIS)

Smith, Z.K.; Dryer, M.; Fillius, R.W.; Smith, E.J.; Wolfe, J.H.

1981-01-01

We examine the major changes in the solar wind before, during, and after the Pioneer 10 and 11 encounters with the Jovian magnetosphere during 1973 and 1974, respectively. In an earlier study, Smith et al. (1978) concluded that the Jovian magnetosphere was subjected to large-scale compression during at least three or four intervals during which it appeared that the spacecraft had reentered the solar wind or magnetosheath near 50 R/sub J/ after having first entered the magnetosphere near 100 R/sub J/. They based this suggestion on the observations of the sister spacecraft, which indicated--on the basis of a kinematic translation of corotating interaction regions (CIR's)--that these structures would be expected to arrive at Jupiter at the appropriate beginning of these three intervals. Our reexamination of this suggestion involved the numerical simulation of the multiple CIR evolutions from one spacecraft to the sister spacecraft. This approach, considered to be a major improvement, confirms the suggestion by Smith et al. (1978) that Jupiter's magnetosphere was compressed by interplanetary CIR's during three or four of these events. Our MHD simulation also suggests that Jupiter's magnetosphere reacts to solar wind rarefactions in the opposite way--by expanding. A previously unexplained pair of magnetopause crossings on the Pioneer 11 outbound pass may simply be due to a delayed reexpansion of Jupiter's magnetosphere from a compression that occurred during the inbound pass

Distribution of ionospheric currents induced by the solar wind interaction with Venus

International Nuclear Information System (INIS)

Daniell, R.E. Jr.; Cloutier, P.A.

1977-01-01

The electric currents induced in the atmosphere of a non-magnetic planet such as Venus by the interaction of the solar wind satisfy a generalized Ohm's Law relationship with tensor conductivity. The distribution of these currents within the planetary ionosphere may be calculated by a variational technique which minimizes the Joule heating over the ionospheric volume. In this paper, we present the development of the variational technique, and apply it to a model of the solar wind interaction with Venus. Potential and current distributions are shown, and the use of these distributions in determining convective transport patterns of planetary ions is discussed. (author)

Magnetospheric processes preceding the onset of an isolated substorm: A case study of the March 31, 1978, substorm

International Nuclear Information System (INIS)

Nishida, A.; Kamide, Y.

1983-01-01

We examined in detail the effect of a southward turning of the interplanetary magnetic field (IMF) on the state of the magnetosphere, taking advantage of the availability of the data from IMS magnetometer meridian chains and from several spacecraft. A clear onset substorm occurred on March 31, 1978, when the magnetometer stations were located in the midnight to morning sector and the spacecraft were near the equatorial plane of the nightside magnetosphere. The onset time of the substorm expansion phase could be determined unambiguously in terms of both ground-based magnetic and auroral signatures, and there was an interval lasting about 1 hour between the IMF southward turning and this onset. In this intervening interval the ionospheric current system of the DP 2 type developed. This enhancement of the ionospheric current was driven directly by the solar wind-magnetosphere coupling. The onset of the expansion phase was then associated with the decrease in the magnetic field energy density in the tail, providing evidence that the substorm energy was supplied by the release (unloading) of energy from the tail. It is most likely that substorm energy dissipated in the auroral ionosphere throughout this relatively isolated and simple event was supplied by two components, 'directly driven' and 'loading-unloading,' the relative importance of which varied depending on the different substorm phases

The response of the day side magnetosphere--ionosphere system to time-varying field line reconnection at the magnetopause. II. Erosion event of March 27, 1968

International Nuclear Information System (INIS)

Reid, G.C.; Holzer, T.E.

1975-01-01

The circuit analogy for the response of the coupled magnetosphere-ionosphere system to changes in day side field line reconnection rate is applied to real conditions and is used to calculate the expected variation in magnetopause position during the erosion event described by Aubry et al. (1970). Generally good agreement between observation and theory is found. The role of the dawn-dusk electric field responsible for magnetospheric convection is examined in some detail and is treated in the circuit analogy as the field due to an external generator connected across the circuit. It is found that the erosion process requires two distinct time constants for a proper description: (1) the time needed for magnetosheath plamsa to travel down the freshly reconnected field lines to the ionosphere and (2) roughly, the time required for the foot of a reconnected field line to travel one quarter of the total noon-midnight dimension of the polar cap. The second time constant is the dominant one and is not related to the ionospheric conductivity, as has been suggested previously. Examination of high-latitude magnetograms obtained during the erosion event discussed shows that the electric field oscillations predicted by the theory and observed by the spacecraft in terms of oscillations in the magnetopause position are also reflected in osci []lations in ionospheric current flow

Saturn's polar ionospheric flows and their relation to the main auroral oval

Directory of Open Access Journals (Sweden)

S. W. H. Cowley

2004-04-01

Full Text Available We consider the flows and currents in Saturn's polar ionosphere which are implied by a three-component picture of large-scale magnetospheric flow driven both by planetary rotation and the solar wind interaction. With increasing radial distance in the equatorial plane, these components consist of a region dominated by planetary rotation where planetary plasma sub-corotates on closed field lines, a surrounding region where planetary plasma is lost down the dusk tail by the stretching out of closed field lines followed by plasmoid formation and pinch-off, as first described for Jupiter by Vasyliunas, and an outer region driven by the interaction with the solar wind, specifically by reconnection at the dayside magnetopause and in the dawn tail, first discussed for Earth by Dungey. The sub-corotating flow on closed field lines in the dayside magnetosphere is constrained by Voyager plasma observations, showing that the plasma angular velocity falls to around half of rigid corotation in the outer magnetosphere, possibly increasing somewhat near the dayside magnetopause, while here we provide theoretical arguments which indicate that the flow should drop to considerably smaller values on open field lines in the polar cap. The implied ionospheric current system requires a four-ring pattern of field-aligned currents, with distributed downward currents on open field lines in the polar cap, a narrow ring of upward current near the boundary of open and closed field lines, and regions of distributed downward and upward current on closed field lines at lower latitudes associated with the transfer of angular momentum from the planetary atmosphere to the sub-corotating planetary magnetospheric plasma. Recent work has shown that the upward current associated with sub-corotation is not sufficiently intense to produce significant auroral acceleration and emission. Here we suggest that the observed auroral oval at Saturn instead corresponds to the ring of upward

Flux and transformation of the solar wind energy in the magnetosheath of the magnetosphere

International Nuclear Information System (INIS)

Pudovkin, M.I.; Semenov, V.S.

1986-01-01

Energy flux, incoming from the solar wind to the Earth magnetosphere is calculated. It is shown that Poynting vector flux, incoming to the reconnection area is generated mainly in the transitional area between the departed shock wave front and magnetopause in the result of the retardation of the solar wind and partial transformation of its kinetic energy into magnetic one. In this case the energy transformation coefficient depends on the interplanetary magnetic field intensity. Solar wind energy gets into the area of magnetic field reconnection at the magnetopause mainly in two forms: electromagnetic and thermal energy. In the course of reconnection process magnetic energy converts into kinetic energy of the accelerated plasma mass movement and subsequently turns (in a high-latitude boundary layer) into electromagnetic energy, incoming directly to magnetosphere tail

Polar ionospheric responses to solar wind IMF changes

Directory of Open Access Journals (Sweden)

Y. Zhang

Full Text Available Auroral and airglow emissions over Eureka (89^° CGM during the 1997-98 winter show striking variations in relation to solar wind IMF changes. The period January 19 to 22, 1998, was chosen for detailed study, as the IMF was particularly strong and variable. During most of the period, B_z was northward and polar arcs were observed. Several overpasses by DMSP satellites during the four day period provided a clear picture of the particle precipitation producing the polar arcs. The spectral character of these events indicated excitation by electrons of average energy 300 to 500 eV. Only occasionally were electrons of average energy up to ~1 keV observed and these appeared transitory from the ground optical data. It is noted that polar arcs appear after sudden changes in IMF B_y, suggesting IMF control over arc initiation. When B_y is positive there is arc motion from dawn to dusk, while B_y is negative the motion is consistently dusk to dawn. F-region (anti-sunward convections were monitored through the period from 630.0 nm emissions. The convection speed was low (100-150 m/s when B_z was northward but increased to 500 m/s after B_z turned southward on January 20.

Key words: Atmospheric composition and structure (airglow and aurora - Ionosphere (particle precipitation - Magnetospheric Physics (polar cap phenomena

New forecasting methods of the intensity and time development of geomagnetic and ionospheric storms

International Nuclear Information System (INIS)

Akasofu, S.I.

1981-01-01

The main phase of a geomagnetic storm develops differently from one storm to another. A description is given of the solar wind quantity which controls directly the development of the main phase of geomagnetic storms. The parameters involved include the solar wind speed, the magnetic field intensity, and the polar angle of the solar wind magnetic field projected onto the dawn-dusk plane. A redefinition of geomagnetic storm and auroral activity is given. It is pointed out that geomagnetic disturbances are caused by the magnetic fields of electric currents which are generated by the solar wind-magnetosphere dynamo. Attention is given to approaches for forecasting the occurrence and intensity of geomagnetic storms and ionospheric disturbances

Recent successes and emerging challenges for coordinated satellite/ground-based magnetospheric exploration and modeling.

Science.gov (United States)

Angelopoulos, Vassilis

With the availability of a distributed constellation of spacecraft (THEMIS, Geotail, Cluster) and increased capability ground based arrays (SuperDARN, THEMIS/GBOs), it is now pos-sible to infer simply from timing significant information regarding mapping of magnetospheric phenomena. Optical, magnetometer and radar data can pinpoint the location and nature of onset signatures. On the other hand, magnetic field modeling constrained by physical bound-aries (such as the isotropy boundary) the measured magnetic field and total pressure values at a distibuted network of satellites has proven to do a much better job at correlating ionospheric precipitation and diffuse auroral boundaries to magnetospheric phenomena, such as the inward boundary of the dipolarization fronts. It is now possible to routinely compare in-situ measured phase space densities of ion and electron distributions during ionosphere -magnetosphere con-junctions, in the absense of potential drops. It is also possible to not only infer equivalent current systems from the ground, but use reconstruction of the ionospheric current system from space to determine the full electrodynamics evolution of the ionosphere and compare with radars. Assimilation of this emerging ground based and global magnetospheric panoply into a self consistent magnetospheric model will likely be one of the most fruitful endeavors in magnetospheric exploration during the next few years.

Global Coupled Model Studies of The Jovian Upper Atmosphere In Response To Electron Precipitation and Ionospheric Convection Within The Auroral Region.

Science.gov (United States)

Millward, G. H.; Miller, S.; Aylward, A. D.

The Jovian Ionospheric Model (JIM) is a global three-dimensional model of Jupiter's coupled ionosphere and thermosphere, developed at University College London. Re- cently, the model has been used to investigate the atmospheric response to electron precipitation within the high-latitude auroral region. A series of simulations have been performed in which the model atmosphere is subjected to monochromatic precipitat- ing electrons of varying number flux and initial energy and, in addition, to various degrees of ionospheric convection. The auroral ionospheric conductivity which re- sults is shown to be strongly non-linear with respect to the incoming electron energy, with a maximum observed for incident particles of initial energy 60 KeV. Electrons with higher energies penetrate the thermospheric region completely, whilst electrons of lower energy (say 10 keV) produce ionisation at higher levels in the atmosphere which are less less condusive to the creation of ionospheric conductivity. Studies of the thermospheric winds with the auroral region show that zonal winds (around the auroral oval) can attain values of around 70% of the driving zonal ion velocity. Also the results show that these large neutral winds are limited in vertical extent to the region of large ionospheric conductivity, tailing off markedly at altitudes above this. The latest results from this work will be presented, and the implications for Jovian magnetospheric-ionospheric coupling will be discussed.

Self-Consistent Model of Magnetospheric Electric Field, Ring Current, Plasmasphere, and Electromagnetic Ion Cyclotron Waves: Initial Results

Science.gov (United States)

Gamayunov, K. V.; Khazanov, G. V.; Liemohn, M. W.; Fok, M.-C.; Ridley, A. J.

2009-01-01

Further development of our self-consistent model of interacting ring current (RC) ions and electromagnetic ion cyclotron (EMIC) waves is presented. This model incorporates large scale magnetosphere-ionosphere coupling and treats self-consistently not only EMIC waves and RC ions, but also the magnetospheric electric field, RC, and plasmasphere. Initial simulations indicate that the region beyond geostationary orbit should be included in the simulation of the magnetosphere-ionosphere coupling. Additionally, a self-consistent description, based on first principles, of the ionospheric conductance is required. These initial simulations further show that in order to model the EMIC wave distribution and wave spectral properties accurately, the plasmasphere should also be simulated self-consistently, since its fine structure requires as much care as that of the RC. Finally, an effect of the finite time needed to reestablish a new potential pattern throughout the ionosphere and to communicate between the ionosphere and the equatorial magnetosphere cannot be ignored.

The ionospheric footprint of antiparallel merging regions on the dayside magnetopause

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I. J. Coleman

2000-05-01

Full Text Available The antiparallel merging hypothesis states that reconnection takes place on the dayside magnetopause where the solar and geomagnetic fields are oppositely directed. With this criterion, we have mapped the predicted merging regions to the ionosphere using the Tsyganenko 96 magnetic field model, distinguishing between regions of sub-Alfvénic and super-Alfvénic magnetosheath flow, and identifying the day-night terminator. We present the resulting shape, width and latitude of the ionospheric dayside merging regions in both hemispheres, showing their dependence on the Earth's dipole tilt. The resulting seasonal variation of the longitudinal width is consistent with the conjugate electric fields in the northern and southern cusps, as measured by the SuperDARN HF radars, for example. We also find a seasonal shift in latitude similar to that observed in satellite cusp data.Key words: Ionosphere (ionosphere-magnetosphere interactions · Magnetospheric physics (magnetopause · cusp and boundary layers; magnetosphere-ionosphere interactions

Solar wind dependence of ion parameters in the Earth's magnetospheric region calculated from CLUSTER observations

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M. H. Denton

2008-03-01

Full Text Available Moments calculated from the ion distributions (~0–40 keV measured by the Cluster Ion Spectrometry (CIS instrument are combined with data from the Cluster Flux Gate Magnetometer (FGM instrument and used to characterise the bulk properties of the plasma in the near-Earth magnetosphere over five years (2001–2005. Results are presented in the form of 2-D xy, xz and yz GSM cuts through the magnetosphere using data obtained from the Cluster Science Data System (CSDS and the Cluster Active Archive (CAA. Analysis reveals the distribution of ~0–40 keV ions in the inner magnetosphere is highly ordered and highly responsive to changes in solar wind velocity. Specifically, elevations in temperature are found to occur across the entire nightside plasma sheet region during times of fast solar wind. We demonstrate that the nightside plasma sheet ion temperature at a downtail distance of ~12 to 19 Earth radii increases by a factor of ~2 during periods of fast solar wind (500–1000 km s⁻¹ compared to periods of slow solar wind (100–400 km s⁻¹. The spatial extent of these increases are shown in the xy, xz and yz GSM planes. The results from the study have implications for modelling studies and simulations of solar-wind/magnetosphere coupling, which ultimately rely on in situ observations of the plasma sheet properties for input/boundary conditions.

Space weather: Modeling and forecasting ionospheric

International Nuclear Information System (INIS)

Calzadilla Mendez, A.

2008-01-01

Full text: Space weather is the set of phenomena and interactions that take place in the interplanetary medium. It is regulated primarily by the activity originating in the Sun and affects both the artificial satellites that are outside of the protective cover of the Earth's atmosphere as the rest of the planets in the solar system. Among the phenomena that are of great relevance and impact on Earth are the auroras and geomagnetic storms , these are a direct result of irregularities in the flow of the solar wind and the interplanetary magnetic field . Given the high complexity of the physical phenomena involved (magnetic reconnection , particle inlet and ionizing radiation to the atmosphere) one of the great scientific challenges today is to forecast the state of plasmatic means either the interplanetary medium , the magnetosphere and ionosphere , for their importance to the development of various human activities such as radio , global positioning , navigation, etc. . It briefly address some of the international ionospheric modeling methods and contributions and participation that currently has the space group of the Institute of Geophysics Geophysics and Astronomy (IGA) in these activities of modeling and forecasting ionospheric. (author)

Formation of field-twisting flux tubes on the magnetopause and solar wind particle entry into the magnetosphere

International Nuclear Information System (INIS)

Sato, T.; Shimada, T.; Tanaka, M.; Hayashi, T.; Watanabe, K.

1986-01-01

A global interaction between the solar wind with a southward interplanetary magnetic field (IMF) and the magnetosphere is studied using a semi-global simulation model. A magnetic flux tube in which field lines are twisted is created as a result of repeated reconnection between the IMF and the outermost earth-rooted magnetic field near the equatorial plane and propagates to higher latitudes. When crossing the polar cusp, the flux tube penetrates into the magnetosphere reiterating reconnection with the earth-rooted higher latitude magnetic field, whereby solar wind particles are freely brought inside the magnetosphere. The flux tube structure has similarities in many aspects to the flux transfer events (FTEs) observed near the dayside magnetopause

Evolution of Eigenmodes of the Mhd-Waveguide in the Outer Magnetosphere

Science.gov (United States)

Chuiko, Daniil

EVOLUTION OF EIGENMODES OF THE MHD-WAVEGUIDE IN THE OUTER MAGNETOSPHERE Mazur V.A., Chuiko D.A. Institute of Solar-Terrestrial Physics, Irkutsk, Russia. Geomagnetic field and plasma inhomogeneties in the outer equatorial part of the magnetosphere al-lows for existence of a channel with low Alfven speeds, which spans from the nose to the far flanks of the magnetosphere, in the morning as well as in the evening sectors. This channel plays a role of a waveguide for fast magnetosonic waves. When an eigenmode travels along the waveguide (i.e. in the azimuthal direction) it undergoes certain evolution. The parameters of the waveguide are changing along the way of wave’s propagation and the eigenmode “adapts” to these parameters. Conditions of the Kelvin-Helmholtz instability are changing due to the increment in the solar wind speed along the magnetopause. The conditions of the solar wind hydromagnetic waves penetration to the magnetosphere are changing due to the same increment. As such, the process of the penetration turns to overreflection regime, which abruptly increases the pump level of the magnetospheric waveguide. There is an Alfven resonance deep within the magnetosphere, which corresponds to the propagation of the fast mode along the waveguide. Oscillation energy dissipation takes place in the vicinity of the Alfven resonance. Alfven resonance is a standing Alfven wave along the magnetic field lines, so it reaches the ionosphere and the Earth surface, when the fast modes of the waveguide, localized in the low Alfven speed channel cannot be observed on Earth. The evolution of the waveguide oscillation propagating from the nose to the far tail is theoretically investigated in this work with consideration of all aforementioned effects. The spatial structure var-iation character, spectral composition and amplitude along the waveguide are found.

A comparison between ion characteristics observed by the POLAR and DMSP spacecraft in the high-latitude magnetosphere

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T. J. Stubbs

2004-03-01

Full Text Available We study here the injection and transport of ions in the convection-dominated region of the Earth's magnetosphere. The total ion counts from the CAMMICE MICS instrument aboard the POLAR spacecraft are used to generate occurrence probability distributions of magnetospheric ion populations. MICS ion spectra are characterised by both the peak in the differential energy flux, and the average energy of ions striking the detector. The former permits a comparison with the Stubbs et al. (2001 survey of He2+ ions of solar wind origin within the magnetosphere. The latter can address the occurrences of various classifications of precipitating particle fluxes observed in the topside ionosphere by DMSP satellites (Newell and Meng, 1992. The peak energy occurrences are consistent with our earlier work, including the dawn-dusk asymmetry with enhanced occurrences on the dawn flank at low energies, switching to the dusk flank at higher energies. The differences in the ion energies observed in these two studies can be explained by drift orbit effects and acceleration processes at the magnetopause, and in the tail current sheet. Near noon at average ion energies of ≈1keV, the cusp and open LLBL occur further poleward here than in the Newell and Meng survey, probably due to convection- related time-of-flight effects. An important new result is that the pre-noon bias previously observed in the LLBL is most likely due to the component of this population on closed field lines, formed largely by low energy ions drifting earthward from the tail. There is no evidence here of mass and momentum transfer from the solar wind to the LLBL by non-reconnection coupling. At higher energies ≈2–20keV, we observe ions mapping to the auroral oval and can distinguish between the boundary and central plasma sheets. We show that ions at these energies relate to a transition from dawnward to duskward dominated flow, this is evidence of how ion drift orbits in the tail influence

A comparison between ion characteristics observed by the POLAR and DMSP spacecraft in the high-latitude magnetosphere

Directory of Open Access Journals (Sweden)

T. J. Stubbs

2004-03-01

Full Text Available We study here the injection and transport of ions in the convection-dominated region of the Earth's magnetosphere. The total ion counts from the CAMMICE MICS instrument aboard the POLAR spacecraft are used to generate occurrence probability distributions of magnetospheric ion populations. MICS ion spectra are characterised by both the peak in the differential energy flux, and the average energy of ions striking the detector. The former permits a comparison with the Stubbs et al. (2001 survey of He²⁺ ions of solar wind origin within the magnetosphere. The latter can address the occurrences of various classifications of precipitating particle fluxes observed in the topside ionosphere by DMSP satellites (Newell and Meng, 1992. The peak energy occurrences are consistent with our earlier work, including the dawn-dusk asymmetry with enhanced occurrences on the dawn flank at low energies, switching to the dusk flank at higher energies. The differences in the ion energies observed in these two studies can be explained by drift orbit effects and acceleration processes at the magnetopause, and in the tail current sheet. Near noon at average ion energies of ≈1keV, the cusp and open LLBL occur further poleward here than in the Newell and Meng survey, probably due to convection- related time-of-flight effects. An important new result is that the pre-noon bias previously observed in the LLBL is most likely due to the component of this population on closed field lines, formed largely by low energy ions drifting earthward from the tail. There is no evidence here of mass and momentum transfer from the solar wind to the LLBL by non-reconnection coupling. At higher energies ≈2–20keV, we observe ions mapping to the auroral oval and can distinguish between the boundary and central plasma sheets. We show that ions at these energies relate to a transition from dawnward to duskward dominated flow, this is evidence of how ion drift orbits in the

Ionospheric research at INPE

International Nuclear Information System (INIS)

Abdu, M.A.

1984-01-01

Ionosphere investigations at INPE are mainly concerned with the problems of equatorial and tropical ionospheres and their electrodynamic coupling with the high latitude ionosphere. Present research objectives include investigations in the following specific areas: equatorial ionospheric plasma dynamics; plasma irregularity generation and morphology, and effects on space borne radar operations; ionospheric response to disturbance dynamo and magnetospheric electric fields; aeronomic effcts of charged particle precipitation in the magnetic anomaly, etc. These problems are being investigated using experimental datacollected from ionospheric diagnostic instruments being operated at different locations in Brazil. These instruments are: ionosondes, VHF electronic polarimeters, L-band scintillation receivers, airglow photometers, riometers and VLF receivers. A brief summary of the research activities and some recnet results will be presented. (Author) [pt

A case study testing the cavity mode model of the magnetosphere

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D. V. Sarafopoulos

2005-07-01

Full Text Available Based on a case study we test the cavity mode model of the magnetosphere, looking for eigenfrequencies via multi-satellite and multi-instrument measurements. Geotail and ACE provide information on the interplanetary medium that dictates the input parameters of the system; the four Cluster satellites monitor the magnetopause surface waves; the POLAR (L=9.4 and LANL 97A (L=6.6 satellites reveal two in-situ monochromatic field line resonances (FLRs with T=6 and 2.5 min, respectively; and the IMAGE ground magnetometers demonstrate latitude dependent delays in signature arrival times, as inferred by Sarafopoulos (2004b. Similar dispersive structures showing systematic delays are also extensively scrutinized by Sarafopoulos (2005 and interpreted as tightly associated with the so-called pseudo-FLRs, which show almost the same observational characteristics with an authentic FLR. In particular for this episode, successive solar wind pressure pulses produce recurring ionosphere twin vortex Hall currents which are identified on the ground as pseudo-FLRs. The BJN ground magnetometer records the pseudo-FLR (alike with the other IMAGE station responses associated with an intense power spectral density ranging from 8 to 12 min and, in addition, two discrete resonant lines with T=3.5 and 7 min. In this case study, even though the magnetosphere is evidently affected by a broad-band compressional wave originated upstream of the bow shock, nevertheless, we do not identify any cavity mode oscillation within the magnetosphere. We fail, also, to identify any of the cavity mode frequencies proposed by Samson (1992.

Keywords. Magnetospheric physics (Magnetosphereionosphere interactions; Solar wind-magnetosphere interactions; MHD waves and instabilities

Magnetosonic resonance in a dipole-like magnetosphere

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A. S. Leonovich

2006-09-01

Full Text Available A theory of resonant conversion of fast magnetosonic (FMS waves into slow magnetosonic (SMS oscillations in a magnetosphere with dipole-like magnetic field has been constructed. Monochromatic FMS waves are shown to drive standing (along magnetic field lines SMS oscillations, narrowly localized across magnetic shells. The longitudinal and transverse structures, as well as spectrum of resonant SMS waves are determined. Frequencies of fundamental harmonics of standing SMS waves lie in the range of 0.1–1 mHz, and are about two orders of magnitude lower than frequencies of similar Alfvén field line resonance harmonics. This difference makes an effective interaction between these MHD modes impossible. The amplitude of SMS oscillations rapidly decreases along the field lines from the magnetospheric equator towards the ionosphere. In this context, magnetospheric SMS oscillations cannot be observed on the ground, and the ionosphere does not play any role either in their generation or dissipation. The theory developed can be used to interpret the occurrence of compressional Pc5 waves in a quiet magnetosphere with a weak ring current.

Cluster and THEMIS observations of the magnetosphere dayside boundaries in preparation for the SMILE mission

Science.gov (United States)

Escoubet, C. P.; Dimmock, A. P.; Walsh, B.; Sibeck, D. G.; Berchem, J.; Nykyri, K.; Turc, L.; Read, A.; Branduardi-Raymont, G.; Wang, C.; Sembay, S.; Kuntz, K. D.; Dai, L.; Li, L.; Donovan, E.; Spanswick, E.; Laakso, H. E.; Zheng, J.; Rebuffat, D.

2016-12-01

Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) is a novel self-standing mission, in collaboration between ESA and Chinese Academy of Science. Its objective is to observe the solar wind-magnetosphere coupling via simultaneous in situ solar wind/magnetosheath plasma and magnetic field measurements, soft X-Ray images of the magnetosheath and polar cusps, and UV images of global auroral distributions. The observations of the cusps and magnetosheath with the X-ray imager are possible through the relatively recent discovery of solar wind charge exchange (SWCX) X-ray emission, first observed at comets, and subsequently found to occur in the vicinity of the Earth's magnetosphere. In preparation for the mission, we need to determine the cusp's morphology, motion and in situ properties (density, velocity, temperature) that are expected to be observed by the spacecraft. To do so, we have selected a series of cusp crossings by the Cluster spacecraft that can be used to simulate X-ray emissions across the width of the cusp for different IMF orientations. In view of the well-known cusp ion dispersions, we expect that X ray emissions peak near the equatorial boundary of the cusp for southward IMF Bz, but near the poleward boundary of the cusp for northward IMF Bz. We also employ Cluster cusp observations during storms to predict X-ray emissions to be expected for periods of high solar wind fluxes. In addition, we use THEMIS observations from January 2008 to July 2015 for moderate (nsw*vsw 4.9x10^8 /cm^2s) solar wind fluxes to investigate X-rays emitted by the magnetosheath and to determine their variation as a function of distance from the subsolar point along the Sun-Earth line and along the flanks of the magnetosphere. We will show that high solar wind fluxes greatly enhance soft X-ray emissions, not only because solar wind fluxes increases but also because the emission region moves deeper within the Earth's exosphere.

Solar wind-magnetosphere coupling during intense magnetic storms (1978-1979)

Science.gov (United States)

Gonzalez, Walter D.; Gonzalez, Alicia L. C.; Tsurutani, Bruce T.; Smith, Edward J.; Tang, Frances

1989-01-01

The solar wind-magnetosphere coupling problem during intense magnetic storms was investigated for ten intense magnetic storm events occurring between August 16, 1978 to December 28, 1979. Particular attention was given to the dependence of the ring current energization on the ISEE-measured solar-wind parameters and the evolution of the ring current during the main phase of the intense storms. Several coupling functions were tested as energy input, and several sets of the ring current decay time-constant were searched for the best correlation with the Dst response. Results indicate that a large-scale magnetopause reconnection operates during an intense storm event and that the solar wind ram pressure plays an important role in the energization of the ring current.

Saturn's polar ionospheric flows and their relation to the main auroral oval

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S. W. H. Cowley

2004-04-01

Full Text Available We consider the flows and currents in Saturn's polar ionosphere which are implied by a three-component picture of large-scale magnetospheric flow driven both by planetary rotation and the solar wind interaction. With increasing radial distance in the equatorial plane, these components consist of a region dominated by planetary rotation where planetary plasma sub-corotates on closed field lines, a surrounding region where planetary plasma is lost down the dusk tail by the stretching out of closed field lines followed by plasmoid formation and pinch-off, as first described for Jupiter by Vasyliunas, and an outer region driven by the interaction with the solar wind, specifically by reconnection at the dayside magnetopause and in the dawn tail, first discussed for Earth by Dungey. The sub-corotating flow on closed field lines in the dayside magnetosphere is constrained by Voyager plasma observations, showing that the plasma angular velocity falls to around half of rigid corotation in the outer magnetosphere, possibly increasing somewhat near the dayside magnetopause, while here we provide theoretical arguments which indicate that the flow should drop to considerably smaller values on open field lines in the polar cap. The implied ionospheric current system requires a four-ring pattern of field-aligned currents, with distributed downward currents on open field lines in the polar cap, a narrow ring of upward current near the boundary of open and closed field lines, and regions of distributed downward and upward current on closed field lines at lower latitudes associated with the transfer of angular momentum from the planetary atmosphere to the sub-corotating planetary magnetospheric plasma. Recent work has shown that the upward current associated with sub-corotation is not sufficiently intense to produce significant auroral acceleration and emission. Here we suggest that the observed auroral oval at Saturn instead corresponds to the ring of

PC index as a proxy of the solar wind energy that entered into the magnetosphere and energy accumulated in the magnetosphere

Science.gov (United States)

Troshichev, Oleg; Sormakov, Dmitry

The PC index has been approved by the International Association of Geomagnetism and Aeronomy (Merida, Mexico, 2013) as a new international index of magnetic activity. Application of the PC index as a proxy of a solar wind energy that entered into the magnetosphere determines a principal distinction of the PC index from AL and Dst indices, which are regarded as characteristics of the energy that realized in magnetosphere in form of substorms and magnetic storms. This conclusion is based on results of analysis of relationships between the polar cap magnetic activity (PC-index) and parameters of the solar wind, on the one hand, relationships between changes of PC and development of magnetospheric substorms (AL-index) and magnetic storms (Dst-index), on the other hand. In this study the relationships between the PC and Dst indices in course of more than 200 magnetic storms observed in epoch of solar maximum (1998-2004) have been examined for different classes of storms separated by their kind and intensity. Results of statistical analysis demonstrate that depression of geomagnetic field starts to develop as soon as PC index steadily excess the threshold level ~1.5 mV/m; the storm intensity (DstMIN) follows, with delay ~ 1 hour, the maximum of PC in course of the storm. Main features of magnetic storms are determined, irrespective of their class and intensity, by the accumulated-mean PC value (PCAM): storm is developed as long as PCAM increases, comes to maximal intensity when PCAM attains the maximum, and starts to decay as soon as PCAM value displays decline. The run of “anomalous” magnetic storm on January 21-22, 2005, lasting many hours (with intensity of ≈ -100 nT) under conditions of northward or close to zero BZ component, is perfectly governed by behavior of the accumulated-mean PCAM index and, therefore, this storm should be regarded as an ordinary phenomenon. The conclusion is made that the PC index provides the unique on-line information on solar wind

Does an Intrinsic Magnetic Field Inhibit or Enhance Planetary Ionosphere Outflow and Loss?

Science.gov (United States)

Strangeway, R. J.; Russell, C. T.; Luhmann, J. G.; Moore, T. E.; Foster, J. C.; Barabash, S. V.; Nilsson, H.

2017-12-01

A characteristic feature of the planets Earth, Venus and Mars is the observation of the outflow of ionospheric ions, most notably oxygen. The oxygen ion outflow is frequently assumed to be a proxy for the loss of water from the planetary atmosphere. In terms of global outflow rates for the Earth the rate varies from 1025 to 1026 s-1, depending on geomagnetic activity. For both Venus and Mars global rates of the order 5x1024 s-1 have been reported. Venus and Mars do not have a large-scale intrinsic magnetic field, and there are several pathways for atmospheric and ionospheric loss. At Mars, because of its low gravity, neutral oxygen can escape through dissociative recombination. At Venus only processes related to the solar wind interaction with the planet such as sputtering and direct scavenging of the ionosphere by the solar wind can result in oxygen escape. At the Earth the intrinsic magnetic field forms a barrier to the solar wind, but reconnection of the Earth's magnetic field with the Interplanetary Magnetic Field allows solar wind energy and momentum to be transferred into the magnetosphere, resulting in ionospheric outflows. Observations of oxygen ions at the dayside magnetopause suggest that at least some of these ions escape. In terms of the evolution of planetary atmospheres how the solar-wind driven escape rates vary for magnetized versus umagnetized planets is also not clear. An enhanced solar wind dynamic pressure will increase escape from the unmagnetized planets, but it may also result in enhanced reconnection at the Earth, increasing outflow and loss rates for the Earth as well. Continued improvement in our understanding of the different pathways for ionospheric and atmospheric loss will allow us to determine how effective an intrinsic planetary field is in preserving a planetary atmosphere, or if we have to look for other explanations as to why the atmospheres of Venus and Mars have evolved to their desiccated state.

Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model

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A. A. Namgaladze

2000-04-01

Full Text Available Current theories of F-layer storms are discussed using numerical simulations with the Upper Atmosphere Model, a global self-consistent, time dependent numerical model of the thermosphere-ionosphere-plasmasphere-magnetosphere system including electrodynamical coupling effects. A case study of a moderate geomagnetic storm at low solar activity during the northern winter solstice exemplifies the complex storm phenomena. The study focuses on positive ionospheric storm effects in relation to thermospheric disturbances in general and thermospheric composition changes in particular. It investigates the dynamical effects of both neutral meridional winds and electric fields caused by the disturbance dynamo effect. The penetration of short-time electric fields of magnetospheric origin during storm intensification phases is shown for the first time in this model study. Comparisons of the calculated thermospheric composition changes with satellite observations of AE-C and ESRO-4 during storm time show a good agreement. The empirical MSISE90 model, however, is less consistent with the simulations. It does not show the equatorward propagation of the disturbances and predicts that they have a gentler latitudinal gradient. Both theoretical and experimental data reveal that although the ratio of [O]/[N2] at high latitudes decreases significantly during the magnetic storm compared with the quiet time level, at mid to low latitudes it does not increase (at fixed altitudes above the quiet reference level. Meanwhile, the ionospheric storm is positive there. We conclude that the positive phase of the ionospheric storm is mainly due to uplifting of ionospheric F2-region plasma at mid latitudes and its equatorward movement at low latitudes along geomagnetic field lines caused by large-scale neutral wind circulation and the passage of travelling atmospheric disturbances (TADs. The calculated zonal electric field disturbances also help to create the positive ionospheric

Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model

Directory of Open Access Journals (Sweden)

A. A. Namgaladze

Full Text Available Current theories of F-layer storms are discussed using numerical simulations with the Upper Atmosphere Model, a global self-consistent, time dependent numerical model of the thermosphere-ionosphere-plasmasphere-magnetosphere system including electrodynamical coupling effects. A case study of a moderate geomagnetic storm at low solar activity during the northern winter solstice exemplifies the complex storm phenomena. The study focuses on positive ionospheric storm effects in relation to thermospheric disturbances in general and thermospheric composition changes in particular. It investigates the dynamical effects of both neutral meridional winds and electric fields caused by the disturbance dynamo effect. The penetration of short-time electric fields of magnetospheric origin during storm intensification phases is shown for the first time in this model study. Comparisons of the calculated thermospheric composition changes with satellite observations of AE-C and ESRO-4 during storm time show a good agreement. The empirical MSISE90 model, however, is less consistent with the simulations. It does not show the equatorward propagation of the disturbances and predicts that they have a gentler latitudinal gradient. Both theoretical and experimental data reveal that although the ratio of [O]/[N₂] at high latitudes decreases significantly during the magnetic storm compared with the quiet time level, at mid to low latitudes it does not increase (at fixed altitudes above the quiet reference level. Meanwhile, the ionospheric storm is positive there. We conclude that the positive phase of the ionospheric storm is mainly due to uplifting of ionospheric F₂-region plasma at mid latitudes and its equatorward movement at low latitudes along geomagnetic field lines caused by large-scale neutral wind circulation and the passage of travelling atmospheric disturbances (TADs. The calculated zonal electric field disturbances also help

Fast Flows in the Magnetotail and Energetic Particle Transport: Multiscale Coupling in the Magnetosphere

Science.gov (United States)

Lin, Y.; Wang, X.; Fok, M. C. H.; Buzulukova, N.; Perez, J. D.; Chen, L. J.

2017-12-01

The interaction between the Earth's inner and outer magnetospheric regions associated with the tail fast flows is calculated by coupling the Auburn 3-D global hybrid simulation code (ANGIE3D) to the Comprehensive Inner Magnetosphere/Ionosphere (CIMI) model. The global hybrid code solves fully kinetic equations governing the ions and a fluid model for electrons in the self-consistent electromagnetic field of the dayside and night side outer magnetosphere. In the integrated computation model, the hybrid simulation provides the CIMI model with field data in the CIMI 3-D domain and particle data at its boundary, and the transport in the inner magnetosphere is calculated by the CIMI model. By joining the two existing codes, effects of the solar wind on particle transport through the outer magnetosphere into the inner magnetosphere are investigated. Our simulation shows that fast flows and flux ropes are localized transients in the magnetotail plasma sheet and their overall structures have a dawn-dusk asymmetry. Strong perpendicular ion heating is found at the fast flow braking, which affects the earthward transport of entropy-depleted bubbles. We report on the impacts from the temperature anisotropy and non-Maxwellian ion distributions associated with the fast flows on the ring current and the convection electric field.

Low frequency wave sources in the outer magnetosphere, magnetosheath, and near Earth solar wind

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O. D. Constantinescu

2007-11-01

Full Text Available The interaction of the solar wind with the Earth magnetosphere generates a broad variety of plasma waves through different mechanisms. The four Cluster spacecraft allow one to determine the regions where these waves are generated and their propagation directions. One of the tools which takes full advantage of the multi-point capabilities of the Cluster mission is the wave telescope technique which provides the wave vector using a plane wave representation. In order to determine the distance to the wave sources, the source locator – a generalization of the wave telescope to spherical waves – has been recently developed. We are applying the source locator to magnetic field data from a typical traversal of Cluster from the cusp region and the outer magnetosphere into the magnetosheath and the near Earth solar wind. We find a high concentration of low frequency wave sources in the electron foreshock and in the cusp region. To a lower extent, low frequency wave sources are also found in other magnetospheric regions.

Heavy Ion Formation in Titan's Ionosphere: Magnetospheric Introduction of Free Oxygen and a Source of Titan's Aerosols?

Science.gov (United States)

Sittler, E. C., Jr.; Ali, A.; Cooper, J. F.; Hartle, R. E.; Johnson, R. E.; Coates, A. J.; Young, D. T.

2009-01-01

Discovery by Cassini's plasma instrument of heavy positive and negative ions within Titan's upper atmosphere and ionosphere has advanced our understanding of ion neutral chemistry within Titan's upper atmosphere, primarily composed of molecular nitrogen, with approx.2.5% methane. The external energy flux transforms Titan's upper atmosphere and ionosphere into a medium rich in complex hydrocarbons, nitriles and haze particles extending from the surface to 1200 km altitudes. The energy sources are solar UV, solar X-rays, Saturn's magnetospheric ions and electrons, solar wind and shocked magnetosheath ions and electrons, galactic cosmic rays (CCR) and the ablation of incident meteoritic dust from Enceladus' E-ring and interplanetary medium. Here it is proposed that the heavy atmospheric ions detected in situ by Cassini for heights >950 km, are the likely seed particles for aerosols detected by the Huygens probe for altitudes <100km. These seed particles may be in the form of polycyclic aromatic hydrocarbons (PAH) containing both carbon and hydrogen atoms CnHx. There could also be hollow shells of carbon atoms, such as C60, called fullerenes which contain no hydrogen. The fullerenes may compose a significant fraction of the seed particles with PAHs contributing the rest. As shown by Cassini, the upper atmosphere is bombarded by magnetospheric plasma composed of protons, H(2+) and water group ions. The latter provide keV oxygen, hydroxyl and water ions to Titan's upper atmosphere and can become trapped within the fullerene molecules and ions. Pickup keV N(2+), N(+) and CH(4+) can also be implanted inside of fullerenes. Attachment of oxygen ions to PAH molecules is uncertain, but following thermalization O(+) can interact with abundant CH4 contributing to the CO and CO2 observed in Titan's atmosphere. If an exogenic keV O(+) ion is implanted into the haze particles, it could become free oxygen within those aerosols that eventually fall onto Titan's surface. The process

Quantitative modelling of the closure of meso-scale parallel currents in the nightside ionosphere

Directory of Open Access Journals (Sweden)

A. Marchaudon

2004-01-01

Full Text Available On 12 January 2000, during a northward IMF period, two successive conjunctions occur between the CUTLASS SuperDARN radar pair and the two satellites Ørsted and FAST. This situation is used to describe and model the electrodynamic of a nightside meso-scale arc associated with a convection shear. Three field-aligned current sheets, one upward and two downward on both sides, are observed. Based on the measurements of the parallel currents and either the conductance or the electric field profile, a model of the ionospheric current closure is developed along each satellite orbit. This model is one-dimensional, in a first attempt and a two-dimensional model is tested for the Ørsted case. These models allow one to quantify the balance between electric field gradients and ionospheric conductance gradients in the closure of the field-aligned currents. These radar and satellite data are also combined with images from Polar-UVI, allowing for a description of the time evolution of the arc between the two satellite passes. The arc is very dynamic, in spite of quiet solar wind conditions. Periodic enhancements of the convection and of electron precipitation associated with the arc are observed, probably associated with quasi-periodic injections of particles due to reconnection in the magnetotail. Also, a northward shift and a reorganisation of the precipitation pattern are observed, together with a southward shift of the convection shear. Key words. Ionosphere (auroral ionosphere; electric fields and currents; particle precipitation – Magnetospheric physics (magnetosphere-ionosphere interactions

A survey of solar wind conditions at 5 AU: a tool for interpreting solar wind-magnetosphere interactions at Jupiter

Energy Technology Data Exchange (ETDEWEB)

Ebert, Robert W. [Space Science and Engineering Division, Southwest Research Institute, San Antonio, TX (United States); Bagenal, Fran [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO (United States); McComas, David J. [Space Science and Engineering Division, Southwest Research Institute, San Antonio, TX (United States); Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX (United States); Fowler, Christopher M., E-mail: rebert@swri.edu [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO (United States)

2014-09-19

We examine Ulysses solar wind and interplanetary magnetic field (IMF) observations at 5 AU for two ~13 month intervals during the rising and declining phases of solar cycle 23 and the predicted response of the Jovian magnetosphere during these times. The declining phase solar wind, composed primarily of corotating interaction regions and high-speed streams, was, on average, faster, hotter, less dense, and more Alfvénic relative to the rising phase solar wind, composed mainly of slow wind and interplanetary coronal mass ejections. Interestingly, none of solar wind and IMF distributions reported here were bimodal, a feature used to explain the bimodal distribution of bow shock and magnetopause standoff distances observed at Jupiter. Instead, many of these distributions had extended, non-Gaussian tails that resulted in large standard deviations and much larger mean over median values. The distribution of predicted Jupiter bow shock and magnetopause standoff distances during these intervals were also not bimodal, the mean/median values being larger during the declining phase by ~1–4%. These results provide data-derived solar wind and IMF boundary conditions at 5 AU for models aimed at studying solar wind-magnetosphere interactions at Jupiter and can support the science investigations of upcoming Jupiter system missions. Here, we provide expectations for Juno, which is scheduled to arrive at Jupiter in July 2016. Accounting for the long-term decline in solar wind dynamic pressure reported by McComas et al. (2013a), Jupiter's bow shock and magnetopause is expected to be at least 8–12% further from Jupiter, if these trends continue.

Transport of transient solar wind particles in Earth's cusps

International Nuclear Information System (INIS)

Parks, G. K.; Lee, E.; Teste, A.; Wilber, M.; Lin, N.; Canu, P.; Dandouras, I.; Reme, H.; Fu, S. Y.; Goldstein, M. L.

2008-01-01

An important problem in space physics still not understood well is how the solar wind enters the Earth's magnetosphere. Evidence is presented that transient solar wind particles produced by solar disturbances can appear in the Earth's mid-altitude (∼5 R E geocentric) cusps with densities nearly equal to those in the magnetosheath. That these are magnetosheath particles is established by showing they have the same ''flattop'' electron distributions as magnetosheath electrons behind the bow shock. The transient ions are moving parallel to the magnetic field (B) toward Earth and often coexist with ionospheric particles that are flowing out. The accompanying waves include electromagnetic and broadband electrostatic noise emissions and Bernstein mode waves. Phase-space distributions show a mixture of hot and cold electrons and multiple ion species including field-aligned ionospheric O + beams

Radar observations of high-latitude lower-thermospheric and upper-mesospheric winds and their response to geomagnetic activity

International Nuclear Information System (INIS)

Johnson, R.M.

1987-01-01

Observations made by the Chatanika, Alaska, incoherent scatter radar during the summer months of 1976 to 1081 are analyzed to obtain high resolution lower-thermospheric neutral winds. Average winds and their tidal components are presented and compared to previous observational and model results. Upper-mesospheric neutral-wind observations obtained by the Poke Flat, Alaska Mesosphere-Stratosphere-Troposphere (MST) radar during the summer months of 1980 to 1982 are investigated statistically for evidence of variations due to geomagnetic activity. Observation of upper-mesospheric neutral winds made during two energetic Solar Proton Events (SPEs) by the Poker Flat, MST radar are presented. These results allow the low-altitude limits of magnetospheric coupling to the neutral atmosphere to be determined. Lower-thermospheric neutral winds are coupled to the ion convection driven by typical magnetospheric forcing above about 100 km. Coupling to lower atmospheric levels does not occur except during intervals of extreme disturbance of the magnetosphere-ionosphere-thermosphere system which are also accompanied by dramatically increased ionization in the high-latitude mesosphere, such as SPEs

The effect of longitudinal conductance variations on the ionospheric prompt penetration electric fields

Science.gov (United States)

Sazykin, S.; Wolf, R.; Spiro, R.; Fejer, B.

Ionospheric prompt penetration electric fields of magnetospheric origin, together with the atmospheric disturbance dynamo, represent the most important parameters controlling the storm-time dynamics of the low and mid-latitude ionosphere. These prompt penetration fields result from the disruption of region-2 field-aligned shielding currents during geomagnetically disturbed conditions. Penetration electric fields con- trol, to a large extent, the generation and development of equatorial spread-F plasma instabilities as well as other dynamic space weather phenomena in the ionosphere equatorward of the auroral zone. While modeling studies typically agree with average patterns of prompt penetration fields, experimental results suggest that longitudinal variations of the ionospheric con- ductivities play a non-negligible role in controlling spread-F phenomena, an effect that has not previously been modeled. We present first results of modeling prompt pene- tration electric fields using a version of the Rice Convection Model (RCM) that allows for longitudinal variations in the ionospheric conductance tensor. The RCM is a first- principles numerical ionosphere-magnetosphere coupling model that solves for the electric fields, field-aligned currents, and particle distributions in the ionosphere and inner/middle magnetosphere. We compare these new theoretical results with electric field observations.

Ionospheric flow during extended intervals of northward but By -dominated IMF

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J. B. Sigwarth

Full Text Available We present SuperDARN radar observations of the nightside high-latitude ionospheric flow during two 6-hour intervals of quasi-steady northward interplanetary magnetic field (IMF. During both intervals (01:30–07:30 UT on 2 December and 21:00–03:00 UT on 14/15 December 1999, the solar wind and IMF remained relatively steady with Bz positive and By negative, such that the IMF clock angle was ~ - 50° to - 60°. Throughout both intervals the radar data clearly indicate the presence of a highly distorted By-dominated twin cell flow pattern, indicative of an open magnetosphere, which is confirmed by DMSP and auroral data. Estimates of the changes in open flux present during each interval indicate approximately balanced dayside and nightside reconnection at rates of ~ 30–35 kV over the full 6 h. However, strong bursts of flow with speeds of over ~ 1000 ms-1 are observed near magnetic midnight on time scales of ~ 1 h, which are associated with increases in the transpolar voltage. These are indicative of the net closure of open flux by recon-nection in the tail. During one large flow burst, the night-side reconnection rate is estimated to have been ~ 1.5 times the dayside rate, i.e. ~ 45–60 kV compared with ~ 30–40 kV. Magnetic bays, which would indicate the formation of a sub-storm current wedge, are not observed in association with these bursts. In addition, no low-latitude Pi2s or geostationary particle injections were observed, although some local, small amplitude Pi2-band (5–50 mHz activity does accompany the bursts. Coincident measurements of the flow and of the low amplitude magnetic perturbations reveal nightside ionospheric conductances of no more than a few mho, indicative of little associated precipitation. Therefore, we suggest that the flow bursts are the ionospheric manifestation of bursty reconnection events occurring in the more distant geomagnetic tail. The main implication of these findings is that, under the circumstances

Extreme ion heating in the dayside ionosphere in response to the arrival of a coronal mass ejection on 12 March 2012

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H. Fujiwara

2014-07-01

Full Text Available Simultaneous measurements of the polar ionosphere with the European Incoherent Scatter (EISCAT ultra high frequency (UHF radar at Tromsø and the EISCAT Svalbard radar (ESR at Longyearbyen were made during 07:00–12:00 UT on 12 March 2012. During the period, the Advanced Composition Explorer (ACE spacecraft observed changes in the solar wind which were due to the arrival of coronal mass ejection (CME effects associated with the 10 March M8.4 X-ray event. The solar wind showed two-step variations which caused strong ionospheric heating. First, the arrival of shock structures in the solar wind with enhancements of density and velocity, and a negative interplanetary magnetic field (IMF-Bz component caused strong ionospheric heating around Longyearbyen; the ion temperature at about 300 km increased from about 1100 to 3400 K over Longyearbyen while that over Tromsø increased from about 1050 to 1200 K. After the passage of the shock structures, the IMF-Bz component showed positive values and the solar wind speed and density also decreased. The second strong ionospheric heating occurred after the IMF-Bz component showed negative values again; the negative values lasted for more than 1.5 h. This solar wind variation caused stronger heating of the ionosphere in the lower latitudes than higher latitudes, suggesting expansion of the auroral oval/heating region to the lower latitude region. This study shows an example of the CME-induced dayside ionospheric heating: a short-duration and very large rise in the ion temperature which was closely related to the polar cap size and polar cap potential variations as a result of interaction between the solar wind and the magnetosphere.

Does the Magnetosphere go to Sleep?

Science.gov (United States)

Hesse, M.; Moretto, T.; Friis-Christensen, E. A.; Kuznetsova, M.; Østgaard, N.; Tenfjord, P.; Opgenoorth, H. J.

2017-12-01

An interesting question in magnetospheric research is related to the transition between magnetospheric configurations under substantial solar wind driving, and a putative relaxed state after the driving ceases. While it is conceivable that the latter state may be unique and only dependent on residual solar wind driving, a more likely scenario has magnetospheric memory playing a key role. Memory processes may be manifold: constraints from conservation of flux tube entropy to neutral wind inertia in the upper atmosphere may all contribute. In this presentation, we use high-resolution, global, MHD simulations to begin to shed light on this transition, as well as on the concept of a quiet state of the magnetosphere. We will discuss key elements of magnetospheric memory, and demonstrate their influence, as well as the actual memory time scale, through simulations and analytical estimates. Finally, we will point out processes with the potential to effect magnetospheric memory loss.

Data-Based Mapping of Our Dynamical Magnetosphere (Julius Bartels Medal Lecture)

Science.gov (United States)

Tsyganenko, Nikolai A.

2013-04-01

The geomagnetic field is a principal agent connecting our planet's ionosphere with thehighly variable interplanetary medium, incessantly disturbed by dynamical processesat the Sun. The Earth's magnetosphere serves as a giant storage reservoir of energy pumped in from the solar wind and intermittently spilled into the upperatmosphere during space storms. As the humankindgets more and more dependent on space technologies, it becomes increasingly important to be able to accurately map the distant geomagnetic field and predict its dynamicsusing data of upstream solar wind monitors. Two approaches to the problem have beensuccessfully pursued over last decades. The first one is to treat the solar wind asa flow of magnetized conducting fluid and to numerically solve first-principle equations,governing its interaction with the terrestrial magnetic dipole. Based on pure theory, that approachaddresses the question: "What the magnetosphere would look like and behaveunder assumption thatthe underlying approximations and techniques were universally accurate?" This lecturewill focus on the other, completely different approach, based on direct observations. Its essence is to develop an empirical description of the global geomagnetic field and its response to the solar wind driving by fitting model parameters to large multi-year sets of spacecraft data. Models of that kind seek to answer the question: "What can in situ measurements tell us about the global magnetospheric configuration and its storm-time dynamics, provided our approximations are realistic, flexible, and the data coverage is sufficiently dense and broad?" Five decades of spaceflight produced enormous amount of archived data anda number of empirical models have already been developed on that basis. Recent and ongoing multi-spacecraft missions keep pouring in new data and further expandthe huge and yet largely untapped resource of valuable information. The main goal of the data-based modeling is to extract the largest

Excitation of a magnetospheric maser through modification of the Earth’s ionosphere by high-power HF radio emission from a ground-based transmitter

International Nuclear Information System (INIS)

Markov, G. A.; Belov, A. S.; Frolov, V. L.; Rapoport, V. O.; Parrot, M.

2010-01-01

A method for controlled excitation of a magnetospheric maser through the production of artificial density ducts by high-power HF radio emission from the Earth’s surface has been proposed and implemented in an in-situ experiment. Artificial density ducts allow one to affect the maser resonator system and the excitation and propagation of low-frequency electromagnetic waves in a disturbed magnetic flux tube. The experimental data presented here were obtained at the mid-latitude Sura heating facility. The characteristics of electromagnetic and plasma disturbances at outer-ionosphere altitudes were measured using the onboard equipment of the DEMETER satellite as it passed through the magnetic flux tube rested on the region of intense generation of artificial ionospheric turbulence.

A survey of solar wind conditions at 5 AU: A tool for interpreting solar wind-magnetosphere interactions at Jupiter

Directory of Open Access Journals (Sweden)

Robert Wilkes Ebert

2014-09-01

Full Text Available We examine Ulysses solar wind and interplanetary magnetic field (IMF observations at 5 AU for two ~13 month intervals during the rising and declining phases of solar cycle 23 and the predicted response of the Jovian magnetosphere during these times. The declining phase solar wind, composed primarily of corotating interaction regions and high-speed streams, was, on average, faster, hotter, less dense, and more Alfvénic relative to the rising phase solar wind, composed mainly of slow wind and interplanetary coronal mass ejections. Interestingly, none of solar wind and IMF distributions reported here were bimodal, a feature used to explain the bimodal distribution of bow shock and magnetopause standoff distances observed at Jupiter. Instead, many of these distributions had extended, non-Gaussian tails that resulted in large standard deviations and much larger mean over median values. The distribution of predicted Jupiter bow shock and magnetopause standoff distances during these intervals were also not bimodal, the mean/median values being larger during the declining phase by ~1 – 4%. These results provide data-derived solar wind and IMF boundary conditions at 5 AU for models aimed at studying solar wind-magnetosphere interactions at Jupiter and can support the science investigations of upcoming Jupiter system missions. Here, we provide expectations for Juno, which is scheduled to arrive at Jupiter in July 2016. Accounting for the long-term decline in solar wind dynamic pressure reported by McComas et al. (2013, Jupiter’s bow shock and magnetopause is expected to be at least 8 – 12% further from Jupiter, if these trends continue.

Terrestrial VLF transmitter injection into the magnetosphere

Science.gov (United States)

Cohen, M. B.; Inan, U. S.

2012-08-01

Very Low Frequency (VLF, 3-30 kHz) radio waves emitted from ground sources (transmitters and lightning) strongly impact the radiation belts, driving electron precipitation via whistler-electron gyroresonance, and contributing to the formation of the slot region. However, calculations of the global impacts of VLF waves are based on models of trans-ionospheric propagation to calculate the VLF energy reaching the magnetosphere. Limited comparisons of these models to individual satellite passes have found that the models may significantly (by >20 dB) overestimate amplitudes of ground based VLF transmitters in the magnetosphere. To form a much more complete empirical picture of VLF transmitter energy reaching the magnetosphere, we present observations of the radiation pattern from a number of ground-based VLF transmitters by averaging six years of data from the DEMETER satellite. We divide the slice at ˜700 km altitude above a transmitter into pixels and calculate the average field for all satellite passes through each pixel. There are enough data to see 25 km features in the radiation pattern, including the modal interference of the subionospheric signal mapped upwards. Using these data, we deduce the first empirical measure of the radiated power into the magnetosphere from these transmitters, for both daytime and nighttime, and at both the overhead and geomagnetically conjugate region. We find no detectable variation of signal intensity with geomagnetic conditions at low and mid latitudes (L ionospheric heating by one VLF transmitter which modifies the trans-ionospheric absorption of signals from other transmitters passing through the heated region.

Supersonic plasma flow between high latitude conjugate ionospheres

International Nuclear Information System (INIS)

Roesler, G.

1975-01-01

The polar wind problem has been investigated for closed field lines in situations where one of the two conjugate ionospheric regions is fully illuminated by the sun and the other darkness (solstices at high latitudes). A supersonic flow between hemispheres is possible; the magnetospheric part of this flow must be symmetric with respect to the equator. The daytime fluxes are proportional to the neutral hydrogen density. Fluxes of the order of 10 8 cm -2 sec -1 are only possible with density considerably higher than given by CIRA models. For stationary solutions higher flow speeds are needed on the dark side than provided from the illuminated side. It is concluded that shock waves with upward velocities of about 5 km/sec would form above the dark ionosphere. This implies a reduction by a factor of 3 to 5 of the plasma influx into the dark hemisphere, whereby F-layer densities of only up to 2 x 10 4 cm -3 can be maintained. (orig.) [de

Mini-magnetospheric plasma propulsion (M2P2): High speed propulsion sailing the solar wind

International Nuclear Information System (INIS)

Winglee, Robert; Slough, John; Ziemba, Tim; Goodson, Anthony

2000-01-01

Mini-Magnetospheric Plasma Propulsion (M2P2) seeks the creation of a magnetic wall or bubble (i.e. a magnetosphere) that will intercept the supersonic solar wind which is moving at 300-800 km/s. In so doing, a force of about 1 N will be exerted on the spacecraft by the spacecraft while only requiring a few mN of force to sustain the mini-magnetosphere. Equivalently, the incident solar wind power is about 1 MW while about 1 kW electrical power is required to sustain the system, with about 0.25-0.5 kg being expended per day. This nominal configuration utilizing only solar electric cells for power, the M2P2 will produce a magnetic barrier approximately 15-20 km in radius, which would accelerate a 70-140 kg payload to speeds of about 50-80 km/s. At this speed, missions to the heliopause and beyond can be achieved in under 10 yrs. Design characteristics for a prototype are also described

A dynamic system to forecast ionospheric storm disturbances based on solar wind conditions

Directory of Open Access Journals (Sweden)

L. R. Cander

2005-06-01

Full Text Available For the reliable performance of technologically advanced radio communications systems under geomagnetically disturbed conditions, the forecast and modelling of the ionospheric response during storms is a high priority. The ionospheric storm forecasting models that are currently in operation have shown a high degree of reliability during quiet conditions, but they have proved inadequate during storm events. To improve their prediction accuracy, we have to take advantage of the deeper understanding in ionospheric storm dynamics that is currently available, indicating a correlation between the Interplanetary Magnetic Field (IMF disturbances and the qualitative signature of ionospheric storm disturbances at middle latitude stations. In this paper we analyse observations of the foF2 critical frequency parameter from one mid-latitude European ionospheric station (Chilton in conjunction with observations of IMF parameters (total magnitude, Bt and Bz-IMF component from the ACE spacecraft mission for eight storm events. The determination of the time delay in the ionospheric response to the interplanetary medium disturbances leads to significant results concerning the forecast of the ionospheric storms onset and their development during the first 24 h. In this way the real-time ACE observations of the solar wind parameters may be used in the development of a real-time dynamic ionospheric storm model with adequate accuracy.

Coordinated Cluster, ground-based instrumentation and low-altitude satellite observations of transient poleward-moving events in the ionosphere and in the tail lobe

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M. Lockwood

2001-09-01

Full Text Available During the interval between 8:00–9:30 on 14 January 2001, the four Cluster spacecraft were moving from the central magnetospheric lobe, through the dusk sector mantle, on their way towards intersecting the magnetopause near 15:00 MLT and 15:00 UT. Throughout this interval, the EISCAT Svalbard Radar (ESR at Longyearbyen observed a series of poleward-moving transient events of enhanced F-region plasma concentration ("polar cap patches", with a repetition period of the order of 10 min. Allowing for the estimated solar wind propagation delay of 75 ( ± 5 min, the interplanetary magnetic field (IMF had a southward component during most of the interval. The magnetic footprint of the Cluster spacecraft, mapped to the ionosphere using the Tsyganenko T96 model (with input conditions prevailing during this event, was to the east of the ESR beams. Around 09:05 UT, the DMSP-F12 satellite flew over the ESR and showed a sawtooth cusp ion dispersion signature that also extended into the electrons on the equatorward edge of the cusp, revealing a pulsed magnetopause reconnection. The consequent enhanced ionospheric flow events were imaged by the SuperDARN HF backscatter radars. The average convection patterns (derived using the AMIE technique on data from the magnetometers, the EISCAT and SuperDARN radars, and the DMSP satellites show that the associated poleward-moving events also convected over the predicted footprint of the Cluster spacecraft. Cluster observed enhancements in the fluxes of both electrons and ions. These events were found to be essentially identical at all four spacecraft, indicating that they had a much larger spatial scale than the satellite separation of the order of 600 km. Some of the events show a correspondence between the lowest energy magnetosheath electrons detected by the PEACE instrument on Cluster (10–20 eV and the topside ionospheric enhancements seen by the ESR (at 400–700 km. We suggest that a potential barrier at the

Coordinated Cluster, ground-based instrumentation and low-altitude satellite observations of transient poleward-moving events in the ionosphere and in the tail lobe

Directory of Open Access Journals (Sweden)

M. Lockwood

Full Text Available During the interval between 8:00–9:30 on 14 January 2001, the four Cluster spacecraft were moving from the central magnetospheric lobe, through the dusk sector mantle, on their way towards intersecting the magnetopause near 15:00 MLT and 15:00 UT. Throughout this interval, the EISCAT Svalbard Radar (ESR at Longyearbyen observed a series of poleward-moving transient events of enhanced F-region plasma concentration ("polar cap patches", with a repetition period of the order of 10 min. Allowing for the estimated solar wind propagation delay of 75 ( ± 5 min, the interplanetary magnetic field (IMF had a southward component during most of the interval. The magnetic footprint of the Cluster spacecraft, mapped to the ionosphere using the Tsyganenko T96 model (with input conditions prevailing during this event, was to the east of the ESR beams. Around 09:05 UT, the DMSP-F12 satellite flew over the ESR and showed a sawtooth cusp ion dispersion signature that also extended into the electrons on the equatorward edge of the cusp, revealing a pulsed magnetopause reconnection. The consequent enhanced ionospheric flow events were imaged by the SuperDARN HF backscatter radars. The average convection patterns (derived using the AMIE technique on data from the magnetometers, the EISCAT and SuperDARN radars, and the DMSP satellites show that the associated poleward-moving events also convected over the predicted footprint of the Cluster spacecraft. Cluster observed enhancements in the fluxes of both electrons and ions. These events were found to be essentially identical at all four spacecraft, indicating that they had a much larger spatial scale than the satellite separation of the order of 600 km. Some of the events show a correspondence between the lowest energy magnetosheath electrons detected by the PEACE instrument on Cluster (10–20 eV and the topside ionospheric enhancements seen by the ESR (at 400–700 km. We suggest that a potential barrier at the

Identification of the different magnetic field contributions during a geomagnetic storm in magnetospheric and ground observations

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T. Alberti

2016-11-01

Full Text Available We used the empirical mode decomposition (EMD to investigate the time variation of the magnetospheric and ground-based observations of the Earth's magnetic field during both quiet and disturbed periods. We found two timescale variations in magnetospheric data which are associated with different magnetospheric current systems and the characteristic diurnal orbital variation, respectively. On the ground we identified three timescale variations related to the solar-wind–magnetosphere high-frequency interactions, the ionospheric processes, and the internal dynamics of the magnetosphere. This approach is able to identify the different physical processes involved in solar-wind–magnetosphere–ionosphere coupling. In addition, the large-timescale contribution can be used as a local index for the identification of the intensity of a geomagnetic storm on the ground.

Pressure Balance at Mars and Solar Wind Interaction with the Martian Atmosphere

Science.gov (United States)

Krymskii, A. M.; Ness, N. F.; Crider, D. H.; Breus, T. K.; Acuna, M. H.; Hinson, D.

2003-01-01

The strongest crustal fields are located in certain regions in the Southern hemisphere. In the Northern hemisphere, the crustal fields are rather weak and usually do not prevent direct interaction between the SW and the Martian ionosphere/atmosphere. Exceptions occur in the isolated mini-magnetospheres formed by the crustal anomalies. Electron density profiles of the ionosphere of Mars derived from radio occultation data obtained by the Radio Science Mars Global Surveyor (MGS) experiment have been compared with the crustal magnetic fields measured by the MGS Magnetometer/Electron Reflectometer (MAG/ER) experiment. A study of 523 electron density profiles obtained at latitudes from +67 deg. to +77 deg. has been conducted. The effective scale-height of the electron density for two altitude ranges, 145-165 km and 165-185 km, and the effective scale-height of the neutral atmosphere density in the vicinity of the ionization peak have been derived for each of the profiles studied. For the regions outside of the potential mini-magnetospheres, the thermal pressure of the ionospheric plasma for the altitude range 145-185 km has been estimated. In the high latitude ionosphere at Mars, the total pressure at altitudes 160 and 180 km has been mapped. The solar wind interaction with the ionosphere of Mars and origin of the sharp drop of the electron density at the altitudes 200-210 km will be discussed.

VITMO - A Powerful Tool to Improve Discovery in the Magnetospheric and Ionosphere-Thermosphere Domains

Science.gov (United States)

Schaefer, R. K.; Morrison, D.; Potter, M.; Stephens, G.; Barnes, R. J.; Talaat, E. R.; Sarris, T.

2017-12-01

With the advent of the NASA Magnetospheric Multiscale Mission and the Van Allen Probes we have space missions that probe the Earth's magnetosphere and radiation belts. These missions fly at far distances from the Earth in contrast to the larger number of near-Earth satellites. Both of the satellites make in situ measurements. Energetic particles flow along magnetic field lines from these measurement locations down to the ionosphere/thermosphere region. Discovering other data that may be used with these satellites is a difficult and complicated process. To solve this problem, we have developed a series of light-weight web services that can provide a new data search capability for the Virtual Ionosphere Thermosphere Mesosphere Observatory (VITMO). The services consist of a database of spacecraft ephemerides and instrument fields of view; an overlap calculator to find times when the fields of view of different instruments intersect; and a magnetic field line tracing service that maps in situ and ground based measurements for a number of magnetic field models and geophysical conditions. These services run in real-time when the user queries for data and allow the non-specialist user to select data that they were previously unable to locate, opening up analysis opportunities beyond the instrument teams and specialists, making it easier for future students who come into the field. Each service on their own provides a useful new capability for virtual observatories; operating together they provide a powerful new search tool. The ephemerides service was built using the Navigation and Ancillary Information Facility (NAIF) SPICE toolkit (http://naif.jpl.nasa.gov/naif/index.html) allowing them to be extended to support any Earth orbiting satellite with the addition of the appropriate SPICE kernels. The overlap calculator uses techniques borrowed from computer graphics to identify overlapping measurements in space and time. The calculator will allow a user defined uncertainty

Longitudinal effects of ionospheric responses to substorms at middle and lower latitudes: a case study

Directory of Open Access Journals (Sweden)

X. Pi

1995-08-01

Full Text Available An ionospheric model is used to simulate total electron content (TEC disturbance events observed at middle and lower latitude sites near 75°W and 7°E longitudes. Within this longitudinal range, daytime TEC disturbances show patterns that are correlated with substrom activity seen in both auroral electrojet and ring current behavior. In modeling studies of the observed ionospheric effects, both electric field and neutral wind perturbations are examined as possible mechanisms. The morphological features of the required electric field perturbations near drawn and dusk are compared with those at other times to examine the local time characteristics of magnetospheric influence. Large-scale traveling atmospheric disturbances (TADs, an alternative candidate for the disturbance source, are also characterized and compared with known thermospheric behavior.

Localized fast flow disturbance observed in the plasma sheet and in the ionosphere

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R. Nakamura

2005-02-01

Full Text Available An isolated plasma sheet flow burst took place at 22:02 UT, 1 September 2002, when the Cluster footpoint was located within the area covered by the Magnetometers-Ionospheric Radars-All-sky Cameras Large Experiment (MIRACLE. The event was associated with a clear but weak ionospheric disturbance and took place during a steady southward IMF interval, about 1h preceding a major substorm onset. Multipoint observations, both in space and from the ground, allow us to discuss the temporal and spatial scale of the disturbance both in the magnetosphere and ionosphere. Based on measurements from four Cluster spacecraft it is inferred that Cluster observed the dusk side part of a localized flow channel in the plasma sheet with a flow shear at the front, suggesting a field-aligned current out from the ionosphere. In the ionosphere the equivalent current pattern and possible field-aligned current location show a pattern similar to the auroral streamers previously obtained during an active period, except for its spatial scale and amplitude. It is inferred that the footpoint of Cluster was located in the region of an upward field-aligned current, consistent with the magnetospheric observations. The entire disturbance in the ionosphere lasted about 10min, consistent with the time scale of the current sheet disturbance in the magnetosphere. The plasma sheet bulk flow, on the other hand, had a time scale of about 2min, corresponding to the time scale of an equatorward excursion of the enhanced electrojet. These observations confirm that localized enhanced convection in the magnetosphere and associated changes in the current sheet structure produce a signature with consistent temporal and spatial scale at the conjugate ionosphere.

Interaction of plasma cloud with external electric field in lower ionosphere

Directory of Open Access Journals (Sweden)

Y. S. Dimant

2010-03-01

Full Text Available In the auroral lower-E and upper-D region of the ionosphere, plasma clouds, such as sporadic-E layers and meteor plasma trails, occur daily. Large-scale electric fields, created by the magnetospheric dynamo, will polarize these highly conducting clouds, redistributing the electrostatic potential and generating anisotropic currents both within and around the cloud. Using a simplified model of the cloud and the background ionosphere, we develop the first self-consistent three-dimensional analytical theory of these phenomena. For dense clouds, this theory predicts highly amplified electric fields around the cloud, along with strong currents collected from the ionosphere and circulated through the cloud. This has implications for the generation of plasma instabilities, electron heating, and global MHD modeling of magnetosphere-ionosphere coupling via modifications of conductances induced by sporadic-E clouds.

Incoherent-scatter radar measurements of electric field and plasma in the auroral ionosphere

International Nuclear Information System (INIS)

Vondrak, R.

1983-01-01

This chapter summarizes Chatanika radar measurements of electric fields and currents, and their relation to E-region ionization and conductivity. Electric-field coupling between the ionosphere and magnetosphere and the relationship between field-aligned currents and meridional ionospheric currents are examined. Topics considered include the diurnal pattern of the ionization and electric field; electrical coupling between the ionosphere and magnetosphere; and the relationship between meridional currents and field-aligned currents. It is concluded that the incoherent-scatter radar technique has been developed into a powerful method for remotely measuring the electrical and thermal properties of the auroral ionospheric plasma, and that the usefulness of the radar measurements is greatly enhanced when combined with simultaneous satellite measurements

The mid-latitude ionosphere under quiet geomagnetic conditions: propagation analysis of SuperDARN radar observations from large ionospheric perturbations

OpenAIRE

De Larquier, Sebastien

2013-01-01

The Earth's ionosphere is a dynamic environment strongly coupled to the neutral atmosphere, magnetosphere and solar activity. In the context of this research, we restrict our interest to the mid-latitude (a.k.a., sub-auroral) ionosphere during quiet geomagnetic conditions. The Super Dual Auroral Radar Network (SuperDARN) is composed of more than 30 low-power High Frequency (HF, from 8-18 MHz) Doppler radars covering the sub-auroral, auroral and polar ionosphere in both hemispheres. SuperDARN ...

Solar wind-magnetosphere coupling during intense magnetic storms (1978--1979)

International Nuclear Information System (INIS)

Gonzalez, W.D.; Tsurutani, B.T.; Gonzalez, A.L.C.; Smith, E.J.; Tang, F.; Akasofu, S.

1989-01-01

The solar wind-magnetosphere coupling problem is investigated for the ten intense magnetic storms (Dst <-100 nT) that occurred during the 500 days (August 16, 1978 to December 28, 1979) studied by Gonzalez and Tsurutani [1987]. This investigation concentrates on the ring current energization in terms of solar wind parameters, in order to explain the | -Dst | growth observed during these storms. Thus several coupling functions are tested as energy input and several sets of the ring current decay time-constant τ are searched to find best correlations with the Dst response. From the fairly large correlation coefficients found in this study, there is strong evidence that large scale magnetopause reconnection operates during such intense storm events and that the solar wind ram pressure plays an important role in the ring current energization. Thus a ram pressure correction factor is suggested for expressions concerning the reconnection power during time intervals with large ram pressure variations

Role of the magnetospheric convection and inertial forces informing the planetary structure of the ionosphere-protonosphere system

International Nuclear Information System (INIS)

Saenko, Yu.S.; Natsvalyan, N.S.; Tepenitsyna, N.Yu.; Shagimuratov, I.I.

1991-01-01

Mechanisms of forming the planetary distribution of concentrations and fluxes of basic O + and H + ions are investigated on the base of a three-dimensional nonstationary model of ionosphere-protonosphere system. The leading role of diffusion, drifts and inertia in the formation of such structural features as equatorial anomaly, mid-latitudinal gap, polar tail in F2-layer and plasmosphere, plasmosphere, plasma gap and polar wind in protonosphere, as well as regions with increased concentrations of heavy O + ions in the polar wind and plasmosphere, is demonstrated

Momentum flux of the solar wind near planetary magnetospheres: a comparative study

International Nuclear Information System (INIS)

Perez de Tejada, H.

1985-01-01

A study of the velocity profiles of the shocked solar wind exterior to the magnetospheres of the Earth, Mars and Venus is presented. A characteristic difference exists between the conditions present in planets with and without a strong intrinsic magnetic field. In a strongly magnetized planet (as it is the case in the earth), the velocity of the solar wind near the magnetopause remains nearly constant along directions normal to that boundary. In weakly magnetized planets (Venus, Mars), on the other hand, the velocity profile near the magnetopause/ionopause exhibits a transverse gradient which implies decreased values of the momentum flux of the solar wind in those regions. The implications of the different behavior of the shocked solar wind are discussed in connection with the nature of the interaction process that takes place in each case. (author)

An electrodynamic model of the solar wind interaction with the ionospheres of Mars and Venus

International Nuclear Information System (INIS)

Cloutier, P.A.; Daniell, R.E. Jr.

1979-01-01

the electrodynamic model for the solar wind interaction with non-magnetic planets (Cloutier and Daniell, Planet. Space Sci. 21, 463, 1973; Daniell and Cloutier, Planet. Space Sci. 25, 621, 1977) is modified to include the effects of non-ohmic currents in the upper ionosphere. The model is then used to calculate convection patterns induced by the solar wind in the ionospheres of Mars and Venus. For Mars the observations of the neutral mass spectrometer or Vikings 1 and 2 provided the neutral atmosphere. Model calculations reproduced the retarding potential analyzer data and indicate that the ionosphere above about 200 km is probably controlled by convection rather than chemistry or diffusion. For Venus a model atmosphere based on Dickenson and Ridley, J. Atmos. Sci. 32, 1219 (1975) and Mayr et al., J. Geophys. Res. 83, 4411 (1978) was used. The resulting model calculations were compared to radio occultation data from Mariners 5 and 10 and Venera 9 which represent extremes in the variability of the upper Cytherean ionosphere. The model calculations are shown to fall within this variation. These results represent the state of the theory immediately prior to the Pioneer-Venus encounter. (author)

Terrestrial magnetosphere and comparison with Jupiter's

International Nuclear Information System (INIS)

Michel, F.C.

1974-01-01

A review of the characteristics of Jupiter's magnetosphere, with comparisons to the earth's is given. Radio observations of Jupiter indicate that energetic electrons are trapped in its magnetic field. The interaction of the trapped radiation with the satellite Io and the centrifugal instability of Jupiter's magnetosphere are discussed. Jupiter's outer magnetosphere is constantly accreting plasma at an uncertain rate. Various mechanisms for supplying ions to the outer magnetosphere are discussed, including: gravitational and centrifugal forces acting on corotating particles; field-line diffusion; photoelectron injection; excitation by Io or other satellites; and viscous interaction with the solar wind. The over-all morphology of the Jovian magnetosphere seems to be highly distorted by centrifugal forces and is easily compressed or deflected by the solar wind

Pulsar magnetospheres

International Nuclear Information System (INIS)

Kennel, C.F.; Fujimura, F.S.; Pellat, R.

1979-01-01

The structure of both the interior and exterior pulsar magnetospehere depends upon the strength of its plasma source near the surface of the star. We review magnetospheric models in the light of a vacuum pair-production source model proposed by Sturrock, and Ruderman and Sutherland. This model predicts the existence of a cutoff, determined by the neutron star's spin rate and magnetic field strength, beyond which coherent radio emission is no longer possible. The observed distribution of pulsar spin periods and period derivates, and the distribution of pulsars with missing radio pulses, is quantitatively consistent with the pair production threshold, when its variation of neutron star radius and moment of interia with mass is taken into account. All neutron stars observed as pulsars can have relativistic magneto-hydrodynamic wind exterior magnetospheres. The properties of the wind can be directly related to those of the pair production source. Radio pulsars cannot have relativistic plasma wave exterior magnetospheres. On the other hand, most erstwhile pulsars in the galaxy are probably halo objects that emit weak fluxes of energetic photons that can have relativistic wave exterior magnetospheres. Extinct pulsars have not been yet observed. (orig.)

Physical Processes for Driving Ionospheric Outflows in Global Simulations

Science.gov (United States)

Moore, Thomas Earle; Strangeway, Robert J.

2009-01-01

We review and assess the importance of processes thought to drive ionospheric outflows, linking them as appropriate to the solar wind and interplanetary magnetic field, and to the spatial and temporal distribution of their magnetospheric internal responses. These begin with the diffuse effects of photoionization and thermal equilibrium of the ionospheric topside, enhancing Jeans' escape, with ambipolar diffusion and acceleration. Auroral outflows begin with dayside reconnexion and resultant field-aligned currents and driven convection. These produce plasmaspheric plumes, collisional heating and wave-particle interactions, centrifugal acceleration, and auroral acceleration by parallel electric fields, including enhanced ambipolar fields from electron heating by precipitating particles. Observations and simulations show that solar wind energy dissipation into the atmosphere is concentrated by the geomagnetic field into auroral regions with an amplification factor of 10-100, enhancing heavy species plasma and gas escape from gravity, and providing more current carrying capacity. Internal plasmas thus enable electromagnetic driving via coupling to the plasma, neutral gas and by extension, the entire body " We assess the Importance of each of these processes in terms of local escape flux production as well as global outflow, and suggest methods for their implementation within multispecies global simulation codes. We complete 'he survey with an assessment of outstanding obstacles to this objective.

The Equatorial Scintillations and Space Weather Effects on its Generation during Geomagnetic Storms

Science.gov (United States)

Biktash, Lilia

Great diversity of the ionospheric phenomena leads to a variety of irregularity types with spatial size from many thousands of kilometers to few centimeters and lifetimes from days to fractions of second. Since the ionosphere strongly influences the propagation of radio waves, signal distortions caused by these irregularities affect short-wave transmissions on Earth, transiono-spheric satellite communications and navigation. In this work the solar wind and the equatorial ionosphere parameters, Kp, Dst, AU, AL indices characterized contribution of different mag-netospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the space weather effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict scintil-lations from Aarons' criteria using the Dst index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of elec-tron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind -magnetosphere -ionosphere during magnetic storms have progressed greatly. We have examined scintillation relation to magnetospheric and ionospheric currents and show that the factor, which presents during magnetic storms to fully inhibit scin-tillation, is the positive Bz-component of the IMF. During the positive Bz IMF F layer cannot raise altitude where scintillations are formed. The auroral indices and Kp do better for the prediction of the ionospheric scintillations at the equator. The interplanetary magnetic field data and models can be used to explain the relationship between the equatorial ionospheric parameters, h'F, foF2, and the equatorial geomagnetic variations with the polar ionosphere cur-rents and

Tropospheric weather influenced by solar wind through atmospheric vertical coupling downward control

Science.gov (United States)

Prikryl, Paul; Bruntz, Robert; Tsukijihara, Takumi; Iwao, Koki; Muldrew, Donald B.; Rušin, Vojto; Rybanský, Milan; Turňa, Maroš; Šťastný, Pavel

2018-06-01

Occurrence of severe weather in the context of solar wind coupling to the magnetosphere-ionosphere-atmosphere (MIA) system is investigated. It is observed that significant snowfall, wind and heavy rain, particularly if caused by low pressure systems in winter, tend to follow arrivals of high-speed solar wind. Previously published statistical evidence that explosive extratropical cyclones in the northern hemisphere tend to occur within a few days after arrivals of high-speed solar wind streams from coronal holes (Prikryl et al., 2009, 2016) is corroborated for the southern hemisphere. Cases of severe weather events are examined in the context of the magnetosphere-ionosphere-atmosphere (MIA) coupling. Physical mechanism to explain these observations is proposed. The leading edge of high-speed solar wind streams is a locus of large-amplitude magneto-hydrodynamic waves that modulate Joule heating and/or Lorentz forcing of the high-latitude lower thermosphere generating medium-scale atmospheric gravity waves that propagate upward and downward through the atmosphere. Simulations of gravity wave propagation in a model atmosphere using the Transfer Function Model (Mayr et al., 1990) reveal that propagating waves originating in the lower thermosphere can excite a spectrum of gravity waves in the lower atmosphere. In spite of significantly reduced amplitudes but subject to amplification upon reflection in the upper troposphere, these gravity waves can provide a lift of unstable air to release instabilities in the troposphere and initiate convection to form cloud/precipitation bands. It is primarily the energy provided by release of latent heat that leads to intensification of storms. These results indicate that vertical coupling in the atmosphere exerts downward control from solar wind to the lower atmospheric levels influencing tropospheric weather development.

The Warm Plasma Composition in the Inner Magnetosphere during 2012-2015

Science.gov (United States)

Jahn, J. M.; Goldstein, J.; Reeves, G. D.; Fernandes, P. A.; Skoug, R. M.; Larsen, B.; Spence, H. E.

2017-12-01

Ionospheric heavy ions play an important role in the dynamics of Earth's magnetosphere. The greater mass and gyro radius of ionospheric oxygen differentiates its behavior from protons at the same energies. Oxygen may have an impact on tail reconnection processes, and it can at least temporarily dominate the energy content of the ring current during geomagnetic storms. At sub-keV energies, multi-species ion populations in the inner magnetosphere form the warm plasma cloak, occupying the energy range between the plasmasphere and the ring current. Lastly, cold lighter ions from the mid-latitude ionosphere create the co-rotating plasmasphere whose outer regions can interact with the plasma cloak, plasma sheet, ring current, and outer electron belt. In this paper we present a statistical view of warm, cloak-like ion populations in the inner magnetosphere, contrasting in particular the warm plasma composition during quiet and active times. We study the relative abundances and absolute densities of warm plasma measured by the Van Allen Probes, whose two spacecraft cover the inner magnetosphere from plasmaspheric altitudes close to Earth to just inside geostationary orbit. We observe that warm (> 30 eV) oxygen is most abundant closer to the plasmasphere boundary whereas warm hydrogen dominates closer to geostationary orbit. Warm helium is usually a minor constituent, but shows a noticeable enhancement in the near-Earth dusk sector.

Analysis of ULF Waves During Substorms Observed in the Ionosphere from the Dayside Ground Magnetometer and in the Solar Wind from the Satellite

Science.gov (United States)

Streltsov, A. V.; Alimaganbetov, M.

2017-12-01

Magnetospheric substorm is one of the most interesting and complicated phenomena of solar-terrestrial interactions. Despite numerous theoretical and experimental studies conducted during last 50 years, its several important phenomena are not completely understood yet. One of them are intense, ultra-low-frequency (from 0.5 mHz to 100 mHz), electromagnetic pulsations which are always observed during the substorms with the ground-based magnetometers and radars at high latitudes. These waves have the largest amplitudes in the power spectral densities during substorms. Hence, they are the most effective drivers of such mechanisms as high-latitude ionosphere energization, ion outflow production, formation of plasma density cavities, etc. In our study, we focus on the waves with frequencies 0.5-1.0 mHz, which is the lowest part of the frequency spectra observed during the substorm. The questions of what phenomena cause these oscillations and what are their spatiotemporal properties are among the most important ones about the physics of the substorm. To answer these questions, we analyzed disturbances of the magnetic field obtained from the two sources for the period from October 2015 to November 2016 during several substorms. One source is the fluxgate magnetometer in Poker Flat, Alaska. Another is the NASA Advanced Composite Explorer satellite in the Lagrangian L1 point that detects most of the solar wind from the Sun. The goal of our project is to find correlations between the disturbances observed from these sources, which will be a strong argument that the solar wind has a strong influence on the electromagnetic coupling between the ionosphere and magnetosphere of the Earth during the substorms. We observed 48 substorms during the abovementioned period. Our findings show that 1) the dominant frequency of the large-amplitude ULF waves observed during the substorms is 1 mHz or less; and 2) the same frequencies are frequently observed in the waves detected from the both

Terrestrial magnetosphere

International Nuclear Information System (INIS)

Pande, D.C.; Agarwal, D.C.

1982-01-01

This paper presents a review about terrestrial magnetosphere. During the last few years considerable investigation have been carried out about the properties of Solar Wind and its interaction with planetary magnetic fields. It is therefore of high importance to accumulate all the investigations in a comprehensive form. The paper reviews the property of earth's magnetosphere, magnetosheath, magneto pause, polar cusps, bow shook and plasma sheath. (author)

Substorms - Future of magnetospheric substorm-storm research

International Nuclear Information System (INIS)

Akasofu, S.I.

1989-01-01

Seven approaches and/or areas of magnetospheric substorm and storm science which should be emphasized in future research are briefly discussed. They are: the combining of groups of researchers who study magnetic storms and substorms in terms of magnetic reconnection with those that do not, the possible use of a magnetosphere-ionosphere coupling model to merge the groups, the development of improved input-output relationships, the complementing of satellite and ground-based observations, the need for global imaging of the magnetosphere, the complementing of observations with computer simulations, and the need to study the causes of changes in the north-south component of the IMF. 36 refs

The use of electron beams as probes of the distant magnetosphere

International Nuclear Information System (INIS)

Winckler, J.R.

1982-01-01

This chapter reports on experiments in which electron beams have been injected into the magnetosphere in order to diagnose plasma processes at a great distance by measurements made in the ionosphere. Topics considered include the beam injecting rocket system in the ionosphere; beam detection and analysis; echo detection by particle counters; echo analysis; the structure of echoes; the atmosphere as a detector; radio and radar methods; perturbation of the distant magnetosphere by beam injection; changes in the injected beam in the near-rocket region; some observations of the distant magnetosphere by beams; the comparison of distant and local electric fields; electron diffusion; the distant magnetic field; and future possibilities. Conjugate locations, field line lengths, electric and magnetic drifts, field fluctuations, and electron scattering and diffusion are analyzed. Echo detection by particle counters on some of the ECHO rocket series is discussed in detail

Inhibition of the electron cyclotron maser instability in the dense magnetosphere of a hot Jupiter

Science.gov (United States)

Daley-Yates, S.; Stevens, I. R.

2018-06-01

Hot Jupiter (HJ) type exoplanets are expected to produce strong radio emission in the MHz range via the Electron Cyclotron Maser Instability (ECMI). To date, no repeatable detections have been made. To explain the absence of observational results, we conduct 3D adaptive mess refinement (AMR) magnetohydrodynamic (MHD) simulations of the magnetic interactions between a solar type star and HJ using the publicly available code PLUTO. The results are used to calculate the efficiency of the ECMI at producing detectable radio emission from the planets magnetosphere. We also calculate the frequency of the ECMI emission, providing an upper and lower bounds, placing it at the limits of detectability due to Earth's ionospheric cutoff of ˜10 MHz. The incident kinetic and magnetic power available to the ECMI is also determined and a flux of 0.075 mJy for an observer at 10 pc is calculated. The magnetosphere is also characterized and an analysis of the bow shock which forms upstream of the planet is conducted. This shock corresponds to the thin shell model for a colliding wind system. A result consistent with a colliding wind system. The simulation results show that the ECMI process is completely inhibited by the planets expanding atmosphere, due to absorption of UV radiation form the host star. The density, velocity, temperature and magnetic field of the planetary wind are found to result in a magnetosphere where the plasma frequency is raised above that due to the ECMI process making the planet undetectable at radio MHz frequencies.

Main Ionospheric Trough and Equatorial Ionization Anomaly During Substorms With the Different UT Onset Moments

Science.gov (United States)

Klimenko, M. V.; Klimenko, V. V.; Bryukhanov, V. V.

2007-05-01

In the given work the numerical calculation results of ionospheric effects of four modeling substorms which have begun in 00, 06, 12 and 18 UT are presented. Calculations are executed on the basis of Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP), developed in WD IZMIRAN, added by the new block of calculation of electric fields in the ionosphere of the Earth for vernal equinox conditions in the minimum of solar activity. In calculations we considered superposition of magnetospheric convection electric field (at set potential differences through polar caps and field aligned currents of the second zone with taking into account of particle precipitation) and dynamo field generated by thermospheric winds without taking into account the tides. It is shown, that in the given statement of problem the substorms cause strong positive disturbances in F-region of ionosphere in night sector. Negative disturbances are much less and arise, mainly, at night in the middle and low latitudes. During substorms longitudinal extent of main ionospheric trough increases. The substorm beginning in 18 UT, causes negative disturbances in high latitudes except for a southern polar cap. Besides there is "stratification" of the main ionospheric trough. As a result in southern hemisphere the additional high-latitude trough which is absent in quiet conditions is formed. "Stratification" of the main ionospheric trough occurs in northern hemisphere at 6 hours after the beginning of the substorm. These "stratifications" are consequence non-stationary magnetospheric convection. Distinction between these events consists that "stratification" in a southern hemisphere occurs in active phase of substorm, and in northern hemisphere in recovery phase. During a substorm beginning in 00 UT, foF2 increases in all northern polar cap. Positive disturbances of foF2 in the equatorial anomaly region cause all presented substorms, except for a substorm beginning in 18 UT

A Full-wave Model for Wave Propagation and Dissipation in the Inner Magnetosphere Using the Finite Element Method

International Nuclear Information System (INIS)

Valeo, Ernest; Johnson, Jay R.; Kim, Eun-Hwa; Phillips, Cynthia

2012-01-01

A wide variety of plasma waves play an important role in the energization and loss of particles in the inner magnetosphere. Our ability to understand and model wave-particle interactions in this region requires improved knowledge of the spatial distribution and properties of these waves as well as improved understanding of how the waves depend on changes in solar wind forcing and/or geomagnetic activity. To this end, we have developed a two-dimensional, finite element code that solves the full wave equations in global magnetospheric geometry. The code describes three-dimensional wave structure including mode conversion when ULF, EMIC, and whistler waves are launched in a two-dimensional axisymmetric background plasma with general magnetic field topology. We illustrate the capabilities of the code by examining the role of plasmaspheric plumes on magnetosonic wave propagation; mode conversion at the ion-ion and Alfven resonances resulting from external, solar wind compressions; and wave structure and mode conversion of electromagnetic ion cyclotron waves launched in the equatorial magnetosphere, which propagate along the magnetic field lines toward the ionosphere. We also discuss advantages of the finite element method for resolving resonant structures, and how the model may be adapted to include nonlocal kinetic effects.

Parabolic heavy ion flow in the polar magnetosphere

International Nuclear Information System (INIS)

Horwitz, J.L.

1987-01-01

Recent observations by the Dynamics Explorer 1 satellite over the dayside polar cap magnetosphere have indicated downward flows of heavy ions (O + , O ++ , N + , N ++ ) with flow velocities of the order 1 km/s (Lockwood et al., 1985b). These downward flows were interpreted as the result of parabolic flow of these heavy ionospheric ions from a source region associated with the polar cleft topside ionosphere. Here the author utilizes a two-dimensional kinetic model to elicit features of the transport of very low energy O + ions from the cleft ionosphere. Bulk parameter (density, flux, thermal energies, etc.) distributions in the noon-midnight meridian plane illustrate the effects of varying convection electric fields and source energies. The results illustrate that particularly under conditions of weak convection electric fields and weak ion heating in the cleft region, much of the intermediate altitude polar cap magnetosphere may be populated by downward flowing heavy ions. It is further shown how two-dimensional transport effects may alter the characteristic vertical profiles of densities and fluxes from ordinary profiles computed in one-dimensional steady state models

Ring current energy injection rate and solar wind-magnetosphere energy coupling

International Nuclear Information System (INIS)

Lee, L.C.; Kan, J.R.; Akasofu, S.-I.

1982-01-01

The purpose of this paper is to (i) formulate the ring current injection rate Usub(R) in terms of phisub(CT) (cross-tail potential drop) by assuming that the ring current formation is a direct consequence of an enhanced convection, (ii) examine the relationship between the injection rate Usub(R) and the power transferred from the solar wind to the magnetosphere and (iii) demonstrate that an enhanced convection indeed leads to the formation of the ring current. (author)

Role of heavy ionospheric ions in the localization of substorm disturbances on March 22, 1979: CDAW 6

International Nuclear Information System (INIS)

Baker, D.N.; Fritz, T.A.; Lennartsson, W.; Wilken, B.; Kroehl, H.W.; Birn, J.

1985-01-01

Extensive ground-based arrays of magnetometers and numerous satellite platforms in the outer magnetosphere have established that two separate substorm expansion onsets occurred on March 22, 1979. The first of these occurred at 1055 UT and is demonstrated to be localized in the 0200--0300 LT sector. Concurrent plasma sheet ion composition measurements are used to show that the growth and expansion phase of this substorm occurred while the outer magnetosphere was composed dominantly of solar wind (H + and He ++ ) plasmas. The 1055 UT substorm greatly perturbed and altered the ion composition of the plasma in the outer magnetosphere such that the second substorm expansion onset (1436 UT) occurred while the outer magnetospheric plasmas were dominantly of ionospheric (O + ) origin. The 1436 UT substorm is shown to have a component of the westward electrojet localized further westward in local time relative to the first substorm. These results are a consistent, well-documented example of the possible important role of heavy ions in the localization and initiation of plasma sheet instabilities during substorms

Tracking a Solar Wind Dynamic Pressure Pulses' Impact Through the Magnetosphere Using the Heliophysics System Observatory

Science.gov (United States)

Vidal-Luengo, S.; Moldwin, M.

2017-12-01

During northward Interplanetary Magnetic Field (IMF) Bz conditions, the magnetosphere acts as a closed "cavity" and reacts to solar wind dynamic pressure pulses more simply than during southward IMF conditions. Effects of solar wind dynamic pressure have been observed as geomagnetic lobe compressions depending on the characteristics of the pressure pulse and the spacecraft location. One of the most important aspects of this study is the incorporation of simultaneous observations by different missions, such as WIND, CLUSTER, THEMIS, MMS, Van Allen Probes and GOES as well as magnetometer ground stations that allow us to map the magnetosphere response at different locations during the propagation of a pressure pulse. In this study we used the SYM-H as an indicator of dynamic pressure pulses occurrence from 2007 to 2016. The selection criteria for events are: (1) the increase in the index must be bigger than 10 [nT] and (2) the rise time must be in less than 5 minutes. Additionally, the events must occur under northward IMF and at the same time at least one spacecraft has to be located in the magnetosphere nightside. Using this methodology we found 66 pressure pulse events for analysis. Most of them can be classified as step function pressure pulses or as sudden impulses (increase followed immediately by a decrease of the dynamic pressure). Under these two categories the results show some systematic signatures depending of the location of the spacecraft. For both kind of pressure pulse signatures, compressions are observed on the dayside. However, on the nightside compressions and/or South-then-North magnetic signatures can be observed for step function like pressure pulses, meanwhile for the sudden impulse kind of pressure pulses the magnetospheric response seems to be less global and more dependent on the local conditions.

The roles of direct input of energy from the solar wind and unloading of stored magnetotail energy in driving magnetospheric substorms

Science.gov (United States)

Rostoker, G.; Akasofu, S. I.; Baumjohann, W.; Kamide, Y.; Mcpherron, R. L.

1987-01-01

The contributions to the substorm expansive phase of direct energy input from the solar wind and from energy stored in the magnetotail which is released in an unpredictable manner are considered. Two physical processes for the dispensation of the energy input from the solar wind are identified: (1) a driven process in which energy supplied from the solar wind is directly dissipated in the ionosphere; and (2) a loading-unloading process in which energy from the solar wind is first stored in the magnetotail and then is suddenly released to be deposited in the ionosphere. The pattern of substorm development in response to changes in the interplanetary medium has been elucidated for a canonical isolated substorm.

Mercury's Solar Wind Interaction as Characterized by Magnetospheric Plasma Mantle Observations With MESSENGER

Science.gov (United States)

Jasinski, Jamie M.; Slavin, James A.; Raines, Jim M.; DiBraccio, Gina A.

2017-12-01

We analyze 94 traversals of Mercury's southern magnetospheric plasma mantle using data from the MESSENGER spacecraft. The mean and median proton number densities in the mantle are 1.5 and 1.3 cm-3, respectively. For sodium number density these values are 0.004 and 0.002 cm-3. Moderately higher densities are observed on the magnetospheric dusk side. The mantle supplies up to 1.5 × 108 cm-2 s-1 and 0.8 × 108 cm-2 s-1 of proton and sodium flux to the plasma sheet, respectively. We estimate the cross-electric magnetospheric potential from each observation and find a mean of 19 kV (standard deviation of 16 kV) and a median of 13 kV. This is an important result as it is lower than previous estimations and shows that Mercury's magnetosphere is at times not as highly driven by the solar wind as previously thought. Our values are comparable to the estimations for the ice giant planets, Uranus and Neptune, but lower than Earth. The estimated potentials do have a very large range of values (1-74 kV), showing that Mercury's magnetosphere is highly dynamic. A correlation of the potential is found to the interplanetary magnetic field (IMF) magnitude, supporting evidence that dayside magnetic reconnection can occur at all shear angles at Mercury. But we also see that Mercury has an Earth-like magnetospheric response, favoring -BZ IMF orientation. We find evidence that -BX orientations in the IMF favor the southern cusp and southern mantle. This is in agreement with telescopic observations of exospheric emission, but in disagreement with modeling.

Comparison between SuperDARN flow vectors and equivalent ionospheric currents from ground magnetometer arrays

DEFF Research Database (Denmark)

Weygand, J. M.; Amm, O.; Angelopoulos, V.

2012-01-01

seasons. This comparison is done over a range of spatial separations, magnetic latitudes, magnetic local times, and auroral electrojet activity to investigate under what conditions the vectors are anti-parallel to one another. Our results show that in general the equivalent ionospheric currents are anti...... that may influence the alignment include ionospheric conductivity gradients and quiet time backgrounds. Our results can be used to approximate the macroscopic (similar to 1000 km) ionospheric convection patterns. The SECS maps represent a value-added product from the raw magnetometer database and can...... be used for contextual interpretation; they can help with our understanding of magnetosphere-ionosphere coupling mechanisms using ground arrays and the magnetospheric spacecraft data, and they can be used as input for other techniques....

A method to derive maps of ionospheric conductances, currents, and convection from the Swarm multisatellite mission

DEFF Research Database (Denmark)

Amm, O.; Vanhamäki, H.; Kauristie, K.

2015-01-01

The European Space Agency (ESA) Swarm spacecraft mission is the first multisatellite ionospheric mission with two low-orbiting spacecraft that are flying in parallel at a distance of ~100–140 km, thus allowing derivation of spatial gradients of ionospheric parameters not only along the orbits...... pattern of FAC is recovered, and the magnitudes are valid in an integrated sense. Finally, using an MHD model run, we show how our technique allows estimation of the ionosphere-magnetosphere coupling parameter K, if conjugate observations of the magnetospheric magnetic and electric field are available...

ULF Waves in the Ionospheric Alfven Resonator: Modeling of MICA Observations

Science.gov (United States)

Streltsov, A. V.; Tulegenov, B.

2017-12-01

We present results from a numerical study of physical processes responsible for the generation of small-scale, intense electromagnetic structures in the ultra-low-frequency range frequently observed in the close vicinity of bright discrete auroral arcs. In particular, our research is focused on the role of the ionosphere in generating these structures. A significant body of observations demonstrate that small-scale electromagnetic waves with frequencies below 1 Hz are detected at high latitudes where the large-scale, downward magnetic field-aligned current (FAC) interact with the ionosphere. Some theoretical studies suggest that these waves can be generated by the ionospheric feedback instability (IFI) inside the ionospheric Alfven resonator (IAR). The IAR is the region in the low-altitude magnetosphere bounded by the strong gradient in the Alfven speed at high altitude and the conducting bottom of the ionosphere (ionospheric E-region) at low altitude. To study ULF waves in this region we use a numerical model developed from reduced two fluid MHD equations describing shear Alfven waves in the ionosphere and magnetosphere of the earth. The active ionospheric feedback on structure and amplitude of magnetic FACs that interact with the ionosphere is implemented through the ionospheric boundary conditions that link the parallel current density with the plasma density and the perpendicular electric field in the ionosphere. Our numerical results are compared with the in situ measurements performed by the Magnetosphere-Ionosphere Coupling in the Alfven Resonator (MICA) sounding rocket, launched on February 19, 2012 from Poker Flat Research Range in Alaska to measure fields and particles during a passage through a discreet auroral arc. Parameters of the simulations are chosen to match actual MICA parameters, allowing the comparison in the most precise and rigorous way. Waves generated in the numerical model have frequencies between 0.30 and 0.45 Hz, while MICA measured

Ionospheric feedback effects on the quasi-stationary coupling between LLBL and postnoon/evening discrete auroral arcs

Directory of Open Access Journals (Sweden)

M. M. Echim

2008-05-01

Full Text Available We discuss a model for the quasi-stationary coupling between magnetospheric sheared flows in the dusk sector and discrete auroral arcs, previously analyzed for the case of a uniform height-integrated Pedersen conductivity (ΣP. Here we introduce an ionospheric feedback as the variation of ΣP with the energy flux of precipitating magnetospheric electrons (εem. One key-component of the model is the kinetic description of the interface between the duskward LLBL and the plasma sheet that gives the profile of Φm, the magnetospheric electrostatic potential. The velocity shear in the dusk LLBL plays the role of a generator for the auroral circuit closing through Pedersen currents in the auroral ionosphere. The field-aligned current density, j||, and the energy flux of precipitating electrons are given by analytic functions of the field-aligned potential drop, ΔΦ, derived from standard kinetic models of the adiabatic motion of particles. The ionospheric electrostatic potential, Φi (and implicitely ΔΦ is determined from the current continuity equation in the ionosphere. We obtain values of ΔΦ of the order of kilovolt and of j|| of the order of tens of μA/m2 in thin regions of the order of several kilometers at 200 km altitude. The spatial scale is significantly smaller and the peak values of ΔΦ, j|| and εem are higher than in the case of a uniform ΣP. Effects on the postnoon/evening auroral arc electrodynamics due to variations of dusk LLBL and solar wind dynamic and kinetic pressure are discussed. In thin regions (of the order of kilometer embedding the maximum of ΔΦ we evidence a non-linear regime of the current-voltage relationship. The model predicts also that visible arcs form when the velocity shear in LLBL is above a threshold value depending on the generator and ionospheric plasma properties. Brighter arcs are obtained for increased velocity shear in the LLBL; their spatial scale remains virtually unmodified. The field

Relative drift between black aurora and the ionospheric plasma

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E. M. Blixt

2005-07-01

Full Text Available Black auroras are recognized as spatially well-defined regions within uniform diffuse aurora where the optical emission is significantly reduced. Although a well studied phenomenon, there is no generally accepted theory for black auroras. One theory suggests that black regions are formed when energetic magnetospheric electrons no longer have access to the loss cone. If this blocking mechanism drifts with the source electron population in the magnetosphere, black auroras in the ionosphere should drift eastward with a velocity that increases with the energy of the precipitating electrons in the surrounding aurora, since the gradient-B curvature drift is energy dependent. It is the purpose of this paper to test this hypothesis. To do so we have used simultaneous measurements by the European Incoherent Scatter (EISCAT radar and an auroral TV camera at Tromsø, Norway. We have analyzed 8 periods in which a black aurora occurred frequently to determine their relative drift with respect to the ionospheric plasma. The black aurora was found to drift eastward with a velocity of 1.5–4km/s, which is in accordance with earlier observations. However, one case was found where a black patch was moving westward, this being the first report of such behaviour in the literature. In general, the drift was parallel to the ionospheric flow but at a much higher velocity. This suggests that the generating mechanism is not of ionospheric origin. The characteristic energy of the precipitating electron population was estimated through inversion of E-region plasma density profiles. We show that the drift speed of the black patches increased with the energy of the precipitating electrons in a way consistent with the gradient-B curvature drift, suggesting a magnetospheric mechanism for the black aurora. As expected, a comparison of the drift speeds with a rudimentary dipole field model of the gradient-B curvature drift speed only yields order-of-magnitude agreement, which

High-Latitude Space Plasma Physics

International Nuclear Information System (INIS)

Hultqvist, B.; Hagfors, T.

1983-01-01

This book constitutes the proceedings of the Nobel Symposium No. 54 on High Latitude Magnetospheric/Ionospheric Plasma Physics. The main purpose of the symposium was to prepare for the European research effort in space plasma physics in the mid-1980's, in which two major constituents are the European Incoherent Scatter Association (EISCAT) facilities and the Swedish satellite Viking. The physics of the high-latitude ionosphere and how this part of near space is affected by the properties of the solar wind and the interplanetary magnetic field are explored. A detailed discussion is provided on high-latitude magnetospheric physics at altitudes of 1-2 earth radii, the main focus of the Viking project. Specific topics considered include the role of the auroral ionosphere in magnetospheric substorms, the low altitude cleft, ionospheric modification and stimulated emissions, plasma physics on auroral field lines, solar wind-magnetosphere energy coupling, cold plasma distribution above a few thousand kilometers at high latitudes, hot electrons in and above the auroral ionosphere, the correlation of auroral kilometric radiation with visual auroras and with Birkeland currents, electrostatic waves in the topside ionosphere, solitary waves and double layers, and an Alfven wave model of auroral arcs

How does the predicted geomagnetic main field variation alter the thermosphere-ionosphere storm-time response?

Science.gov (United States)

Maute, A. I.; Lu, G.; Richmond, A. D.

2017-12-01

Earth's magnetic main field plays an important role in the thermosphere-ionosphere (TI) system, as well as its coupling to Earth's magnetosphere. The ionosphere consists of a weakly ionized plasma strongly influenced by the main field and embedded in the thermosphere. Therefore, ion-neutral coupling and ionospheric electrodynamics can influence the plasma distribution and neutral dynamics. There are strong longitude variations of the TI storm response. At high latitude magnetosphere-ionosphere coupling is organized by the geomagnetic main field, leading in general to stronger northern middle latitude storm time response in the American sector due to the geomagnetic dipole location. In addition, the weak geomagnetic main field in the American sector leads to larger local ExB drift and can alter the plasma densities. During geomagnetic storms the intense energy input into the high latitude region is redistributed globally, leading to thermospheric heating, wind circulation changes and alterations of the ionospheric electrodynamics. The storm time changes are measurable in the plasma density, ion drift, temperature, neutral composition, and other parameters. All these changes depend, to some degree, on the geomagnetic main field which changes on decadal time scales. In this study, we employ a forecast model of the geomagnetic main field based on data assimilation and geodynamo modeling [Aubert et al., 2015]. The main field model predicts that in 50 years the South Atlantic Anomaly is further weakened by 2 mT and drifts westward by approximately 10o. The dipole axis moves northward and westward by 2o and 6o, respectively. Simulating the March 2015 geomagnetic storm with the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIE-GCM) driven by the Assimilative Mapping of Ionospheric Electrodynamics (AMIE), we evaluate the thermosphere-ionosphere response using the geomagnetic main field of 2015, 2065, and 2115. We compare the TI response for 2015 with

Control of particle precipitation by energy transfer from solar wind

Science.gov (United States)

Bremer, J.; Gernandt, H.

1985-12-01

The energy transfer function (epsilon), introduced by Perreault and Akasofu (1978), appears to be well suited for the description of the long-term control of the particle precipitation by interplanetary parameters. An investigation was conducted with the objective to test this control in more detail. This investigation included the calculation of hourly epsilon values on the basis of satellite-measured solar wind and IMF (interplanetary magnetic field) data. The results were compared with corresponding geomagnetic and ionospheric data. The ionospheric data had been obtained by three GDR (German Democratic Republic) teams during the 21st, 22nd, and 23rd Soviet Antarctic Expeditions in the time period from 1976 to 1979. It was found that, in high latitudes, the properties of the solar wind exercise a pronounced degree of control on the precipitation of energetic particles into the atmosphere, taking into account a time delay of about one hour due to the occurrence of magnetospheric storage processes.

Quasi-static electric fields, turbulence and VLF waves in the ionosphere and magnetosphere

International Nuclear Information System (INIS)

Temerin, M.A.

1978-01-01

Two rocket payloads launched from Greenland in December 1974 and January 1975 into the dayside auroral oval measured large scale electric fields. Sunward convection in regions of polar cusp type particle precipitation argues for the existence of a turbulent entry region at the magnetopause. Smaller scale changes in the electric field and energetic electron precipitation require field-aligned currents predominately at the boundaries of auroral arcs. Measurements of electric fields parallel to the magnetic field place upper limits to the parallel electric field. An analysis of the effect of zero-frequency electric field turbulence on the output of an electric field double probe detector is applied to data from two satellites, OVI-17 and S3-3. It is found that the electric field of high latitude low frequency turbulence is polarized perpendicular to the magnetic field and that the frequency is measured by the satellites is due to the Doppler shift of near zero frequency turbulence both in the ionosphere and magnetosphere. In addition, rocket measurements of low frequency turbulence in the dayside auroral oval reveal characteristics similar to those of the large electric field regions recently seen on S3-3 indicating that the turbulence from those regions extends into the ionosphere. VLF waves were also observed during the two rocket flights into the dayside auroral oval. The correlation of the VLF hiss intensity with the fluxes of precipitating electrons above 500 eV on a short spatial and time scale is often poor, even when a positive slope exists in the electron phase space density. The frequency of the lower hybrid waves were used to measure the ratio of NO + and O 2 + to O + . Electrostatic waves were observed during a barium release

Effects of Abrupt Variations of Solar Wind Dynamic Pressure on the High-Latitude Ionosphere

Directory of Open Access Journals (Sweden)

Igino Coco

2011-01-01

Full Text Available We show the results of a statistical study on the effects in the high-latitude ionosphere of abrupt variations of solar wind dynamic pressure, using Super Dual Auroral Radar Network (SuperDARN data in both hemispheres. We find that, during periods of quiet ionospheric conditions, the amount of radar backscatter increases when a variation in the dynamic pressure occurs, both positive (increase of the pressure and negative (decrease of the pressure. We also investigate the behaviour of the Cross-Polar Cap Potential (CPCP during pressure variations and show preliminary results.

Conductance Effects on Inner Magnetospheric Plasma Morphology: Model Comparisons with IMAGE EUV, MENA, and HENA Data

Science.gov (United States)

Liemohn, M.; Ridley, A. J.; Kozyra, J. U.; Gallagher, D. L.; Brandt, P. C.; Henderson, M. G.; Denton, M. H.; Jahn, J. M.; Roelof, E. C.; DeMajistre, R. M.

2004-01-01

Modeling results of the inner magnetosphere showing the influence of the ionospheric conductance on the inner magnetospheric electric fields during the April 17, 2002 magnetic storm are presented. Kinetic plasma transport code results are analyzed in combination with observations of the inner magnetospheric plasma populations, in particular those from the IMAGE satellite. Qualitative and quantitative comparisons are made with the observations from EW, MENA, and HENA, covering the entire energy range simulated by the model (0 to 300 keV). The electric field description, and in particular the ionospheric conductance, is the only variable between the simulations. Results from the data-model comparisons are discussed, detailing the strengths and weaknesses of each conductance choice for each energy channel.

On the Origins of the Intercorrelations Between Solar Wind Variables

Science.gov (United States)

Borovsky, Joseph E.

2018-01-01

It is well known that the time variations of the diverse solar wind variables at 1 AU (e.g., solar wind speed, density, proton temperature, electron temperature, magnetic field strength, specific entropy, heavy-ion charge-state densities, and electron strahl intensity) are highly intercorrelated with each other. In correlation studies of the driving of the Earth's magnetosphere-ionosphere-thermosphere system by the solar wind, these solar wind intercorrelations make determining cause and effect very difficult. In this report analyses of solar wind spacecraft measurements and compressible-fluid computer simulations are used to study the origins of the solar wind intercorrelations. Two causes are found: (1) synchronized changes in the values of the solar wind variables as the plasma types of the solar wind are switched by solar rotation and (2) dynamic interactions (compressions and rarefactions) in the solar wind between the Sun and the Earth. These findings provide an incremental increase in the understanding of how the Sun-Earth system operates.

Nonlinear dynamics of the magnetosphere and space weather

Science.gov (United States)

Sharma, A. Surjalal

1996-01-01

The solar wind-magnetosphere system exhibits coherence on the global scale and such behavior can arise from nonlinearity on the dynamics. The observational time series data were used together with phase space reconstruction techniques to analyze the magnetospheric dynamics. Analysis of the solar wind, auroral electrojet and Dst indices showed low dimensionality of the dynamics and accurate prediction can be made with an input/output model. The predictability of the magnetosphere in spite of the apparent complexity arises from its dynamical synchronism with the solar wind. The electrodynamic coupling between different regions of the magnetosphere yields its coherent, low dimensional behavior. The data from multiple satellites and ground stations can be used to develop a spatio-temporal model that identifies the coupling between different regions. These nonlinear dynamical models provide space weather forecasting capabilities.

ULF fluctuations of the geomagnetic field and ionospheric sounding measurements at low latitudes during the first CAWSES campaign

Directory of Open Access Journals (Sweden)

U. Villante

2006-07-01

Full Text Available We present an analysis of ULF geomagnetic field fluctuations at low latitudes during the first CAWSES campaign (29 March-3 April 2004. During the whole campaign, mainly in the prenoon sector, a moderate Pc3-4 pulsation activity is observed, clearly related to interplanetary upstream waves. On 3 April, in correspondence to the Earth's arrival of a coronal mass ejection, two SIs are observed whose waveforms are indicative of a contribution of the high-latitude ionospheric currents to the low-latitude ground field. During the following geomagnetic storm, low frequency (Pc5 waves are observed at discrete frequencies. Their correspondence with the same frequencies detected in the radial components of the interplanetary magnetic field and solar wind speed suggests that Alfvénic solar wind fluctuations may act as direct drivers of magnetospheric fluctuations. A cross-phase analysis, using different pairs of stations, is also presented for identifying field line resonant frequencies and monitoring changes in plasmaspheric mass density. Lastly, an analysis of ionospheric vertical soundings, measured at the Rome ionosonde station (41.8° N, 12.5° E, and vertical TEC measurements deduced from GPS signals within an European network shows the relation between the ULF resonances in the inner magnetosphere and thermal plasma density variations during geomagnetically quiet conditions, in contrast to various storm phases at the end of the CAWSES campaign.

Operation of a quadripole probe on magnetospheric satellite (GEOS experiment). Contribution to cold plasma behaviour study near equatorial plasma pause

International Nuclear Information System (INIS)

Decreau-Prior, P.

1983-06-01

This thesis is concerned with the exploitation of GEOS Satellite RF quadripole probe measurements, GEOS satellites have explored magnetosphere on the geostationary orbit and around it. Results a low to qualify the instrument in magnetospheric plasma (previously, it had been used only in ionosphere). Furthermore existence, outside the outer plasmasphere, of a cold population (from 0,4 to 8 eV) with medium density (from 2 to 50 particles cm -3 ) is shown. This population had been ignored until then, by in situ particle measure experiment. So, new perspectives on coupling nature of the explored region with ionosphere, and with plasma sheet, more particularly because the temperature measured at the equator is on an average, clearly higher than in high ionosphere the principal source of magnetospheric cold plasma [fr

Variations of the electron concentration in the polar ionosphere

International Nuclear Information System (INIS)

Chasovitin, Yu.K.; Shushkova, V.B.

1980-01-01

The possibility of constructing an empirical model of electron concentration in the polar ionosphere is considered. The results of rocket measurements carried out at Fort Churchill and on the Hays island at 70-210 km heights are used to analyse the distribution of electron concentration in the non-illuminated sector of the auroral oval, in the subauroral ionosphere and in the polar cap. Taking account of magnetospheric-ionospheric relationships and the geomagnetic environment, certain regularities in the distribution of electron concentration in the polar field, which may serve as a basis for constructing an empirical model of the polar ionosphere have been identified

Electric fields and field-aligned current generation in the magnetosphere

International Nuclear Information System (INIS)

Alexeev, I.I.; Belenkaya, E.S.; Kalegaev, V.V.; Lyutov, Yu.G.

1993-01-01

The authors present a calculation of the electric potential, field-aligned currents, and plasma convection caused by the penetration of the solar wind electric field into the magnetosphere. Ohm's law and the continuity equation of ionospheric currents are used. It is shown that the large-scale convection system is reversed in the plasma sheet flanks. In this region the plasma flow is antisunward earthward of the neutral line and sunward tailward of it. The interplanetary magnetic field (IMF) B z dependences on the dimension of the magnetopause open-quotes windowsclose quotes which are intersected by open field lines, on the potential drop across the polar cap, and on the distance to the neutral line are determined. Because of the IMF effect and the effect of seasonal or daily variations of the geomagnetic field which violate its symmetry relative to the equatorial plane, there may arise a potential drop along field lines which causes field-aligned currents. The values and directions of these currents, the field-aligned potential drop, and a self-consistent solution for the potential at the ionosphere level for high field-aligned conductivity have been determined. 41 refs., 7 figs

Neutral wind measurements by Fabry-Perot interferometry in Antarctica

International Nuclear Information System (INIS)

Stewart, K.D.; Dudeney, J.R.; Rodger, A.S.; Smith, R.W.; Rees, D.

1986-01-01

A large-aperture (150 mm), spatially scanned Fabry-Perot Interferometer (FPI) has been deployed at Halley (75.5 o S, 26.8 o W; L=4.2), Antarctica. Thermospheric neutral wind measurements were made by finding the Doppler shift of the OI( 3 P 2 - 1 D 2 ) 630.0 nm emission. This has allowed the first comparison to be made between southern hemisphere ground-based thermospheric wind measurements and the predictions of a three-dimensional, time-dependent thermospheric global circulation model. Geomagnetic and geographic latitude are well separated at Halley, so we may expect a distinct contrast to the dynamic behaviour observed in the more frequently studied northern polar thermosphere. Although the initial results from the experiment are in general agreement with the model, some consistent and significant differences between the observed wind field and that predicted are evident in the morning sector. These may be related to uncertainties in mapping magnetospheric boundaries to ionospheric heights in the southern hemisphere. The intensity of the 630 nm emission has been examined with respect to the maximum plasma frequency of the Es layer using data from the Advanced Ionospheric Sounder at Halley

Quasi-biennial oscillations in the geomagnetic field: Their global characteristics and origin

DEFF Research Database (Denmark)

Ou, Jiaming; Du, Aimin; Finlay, Chris

2017-01-01

Quasi-biennial oscillations (QBOs), with periods in the range 1–3 years, have been persistently observed in the geomagnetic field. They provide unique information on the mechanisms by which magnetospheric and ionospheric current systems are modulated on interannual timescales and are also of cruc...... primarily originates from the current systems due to the solar wind-magnetosphere-ionosphere coupling process....... postmidnight sectors, and the results from spherical harmonic analysis, verify that the majority of geomagnetic QBO is of external origin. We furthermore find a very high correlation between the geomagnetic QBO and the QBOs in solar wind speed and solar wind dynamic pressure. This suggests the geomagnetic QBO......Quasi-biennial oscillations (QBOs), with periods in the range 1–3 years, have been persistently observed in the geomagnetic field. They provide unique information on the mechanisms by which magnetospheric and ionospheric current systems are modulated on interannual timescales and are also...

Southern Hemisphere Upper Thermospheric Wind Climatology

Science.gov (United States)

Dhadly, M. S.; Emmert, J. T.; Drob, D. P.

2017-12-01

This study is focused on the poorly understood large-scale upper thermospheric wind dynamics in the southern polar cap, auroral, and mid latitudes. The gaps in our understanding of the dynamic high-latitude thermosphere are largely due to the sparseness of thermospheric wind measurements. Using data from current observational facilities, it is unfeasible to construct a synoptic picture of the Southern Hemisphere upper thermospheric winds. However, enough data with wide spatial and temporal coverage have accumulated to construct a meaningful statistical analysis of winds as function of season, magnetic latitude, and magnetic local time. We use long-term data from nine ground-based stations located at different southern high latitudes and three space-based instruments. These diverse data sets possess different geometries and different spatial and solar coverage. The major challenge of the effort is to combine these disparate sources of data into a coherent picture while overcoming the sampling limitations and biases among the datasets. Our preliminary analyses show mutual biases present among some of them. We first address the biases among various data sets and then combine them in a coherent way to construct maps of neutral winds for various seasons. We then validate the fitted climatology against the observational data and compare with corresponding fits of 25 years of simulated winds from the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model. This study provides critical insight into magnetosphere-ionosphere-thermosphere coupling and sets a necessary benchmark for validating new observations and tuning first-principles models.

The Role of Hydromagnetic Waves in the Magnetosphere and the Ionosphere

Science.gov (United States)

1988-05-01

ionospheric heating ex- ( MINIX ) was carried out recently by the Kyoto Uni- periments [Stubbe and Kopka, 198! Stubbe et al., versity group in Japan to...ionospheric irregularities and other predicted netosphere with growth times of a few minutes. Our phenomena could not be produced in MINIX be- work...ionosphere: Project- HF produced electron density irregularities in the polar iono- MINIX for future solar power satellite, paper presented at 21st

Electric fields in the ionosphere

International Nuclear Information System (INIS)

Kirchhoff, V.W.J.H.

1975-01-01

F-region drift velocities, measured by incoherent-scatter radar, were analyzed in terms of diurnal, seasonal, magnetic-activity, and solar-cycle effects. A comprehensive electric field model was developed that includes the effects of the E and F-region dynamos, magnetospheric sources, and ionospheric conductivities, for both the local and conjugate regions. The E-region dynamo dominates during the day, but at night the F-region and convection are more important. This model provides much better agreement with observations of the F-region drifts than previous models. Results indicate that larger magnitudes occur at night, and that daily variation is dominated by the diurnal mode. Seasonal variations in conductivities and thermospheric winds indicate a reversal in direction in the early morning during winter from south to northward. On magnetic perturbed days the drifts deviate rather strongly from the quiet days average, especially around 13 L.T. for the northward and 18 L.T. for the westward component

Simulating Sources of Superstorm Plasmas

Science.gov (United States)

Fok, Mei-Ching

2008-01-01

We evaluated the contributions to magnetospheric pressure (ring current) of the solar wind, polar wind, auroral wind, and plasmaspheric wind, with the surprising result that the main phase pressure is dominated by plasmaspheric protons. We used global simulation fields from the LFM single fluid ideal MHD model. We embedded the Comprehensive Ring Current Model within it, driven by the LFM transpolar potential, and supplied with plasmas at its boundary including solar wind protons, polar wind protons, auroral wind O+, and plasmaspheric protons. We included auroral outflows and acceleration driven by the LFM ionospheric boundary condition, including parallel ion acceleration driven by upward currents. Our plasmasphere model runs within the CRCM and is driven by it. Ionospheric sources were treated using our Global Ion Kinetics code based on full equations of motion. This treatment neglects inertial loading and pressure exerted by the ionospheric plasmas, and will be superceded by multifluid simulations that include those effects. However, these simulations provide new insights into the respective role of ionospheric sources in storm-time magnetospheric dynamics.

Wide Field-of-View Soft X-Ray Imaging for Solar Wind-Magnetosphere Interactions

Science.gov (United States)

Walsh, B. M.; Collier, M. R.; Kuntz, K. D.; Porter, F. S.; Sibeck, D. G.; Snowden, S. L.; Carter, J. A.; Collado-Vega, Y.; Connor, H. K.; Cravens, T. E.;

A comprehensive view of solar-terrestrial relationships in terms of a chain of four dynamo-powered plasma acceleration processes

International Nuclear Information System (INIS)

Akasofu, S.-I.

1983-01-01

This paper emphasizes an effort to link processes which relate solar activity and magnetospheric disturbances in terms of energy transfer through a chain of four elements. In this view, each element is explicitly thought to be powered by a dynamo, namely the solar wind generation dynamo, the solar flare dynamo, the solar wind-magnetosphere dynamo and the aurora dynamo, respectively. Each dynamo powers a plasma acceleration process by the Lorentz force and the plasma flows thus generated are the solar wind, the flare-generated solar wind disturbance, the magnetospheric plasma convection and the ionospheric convection, respectively. Each plasma flow conveys the energy from one element to the next in the chain. Some of the kinetic energy of the photospheric plasma is eventually deposited in the polar ionosphere as heat energy. (author)

Field-aligned current density versus electric potential characteristics for magnetospheric flux tubes

International Nuclear Information System (INIS)

Lemaire, J.; Scherer, M.

1983-01-01

The field-aligned current density (Jsub(tot)) is a non-linear function of the applied potential difference (phi) between the ionosphere and the magnetosphere. This nonlinear function has been calculated for plasma boundary conditions typical in a dayside cusp magnetic flux tube. The J-characteristic of such a flux tube changes when the temperatures of the warm magnetospheric electrons and of the cold ionospheric electrons are modified; it changes also when the relative density of the warm plasma is modified; the presence of trapped secondary electrons changes also the J-characteristic. The partial currents contributed by the warm and cold electrons, and by warm and cold ions are illustrated. The dynamic characteristic of an electric circuit depends on the static characteristic of each component of the sytem: i.e. the resistive ionosphere, the return current region, and the region of particle precipitation whose field-aligned current/voltage characteristics have been studied in this article

Conditions for double layers in the Earth's magnetosphere and perhaps in other astrophysical objects

International Nuclear Information System (INIS)

Lyons, L.R.

1987-01-01

Double layers (i.e., electric fields parallel to B) form along auroral field lines in the Earth's magnetosphere. They form in order to maintain current continuity in the ionosphere in the presence of a magnetospheric electric field E with DEL.E not= O. Features which govern the formation of the double layers are: 1) the divergence of E; 2) the conductivity of the ionosphere; and 3) the current-voltage characteristics of auroral magnetic field lines. Astrophysical situations where DEL.E not= O is applied to a conducting plasma similar to the Earth's ionosphere are potential candidates for the formation of double layers. The region with DEL.E not= O can be generated within, or along field lines connected to, the conducting plasma. In addition to DEL.E, shear neutral flow in the conducting plasma can also form double layers. (author)

Dawn–dusk asymmetries in the coupled solar wind–magnetosphere–ionosphere system: a review

Czech Academy of Sciences Publication Activity Database

Walsh, A. P.; Haaland, S.; Forsyth, C.; Keesee, A. M.; Kissinger, J.; Li, K.; Runov, A.; Souček, Jan; Walsh, B. M.; Wing, S.; Taylor, M. G. G. T.

2014-01-01

Roč. 32, č. 7 (2014), s. 705-737 ISSN 0992-7689 R&D Projects: GA ČR(CZ) GAP209/12/2394 Institutional support: RVO:68378289 Keywords : magnetospheric physics * magnetosphere–ionosphere interactions * magnetospheric configuration and dynamics * solar-wind–magnetosphere interactions Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.709, year: 2014 http://www.ann-geophys.net/32/705/2014/angeo-32-705-2014.html

High-time resolution conjugate SuperDARN radar observations of the dayside convection response to changes in IMF By

Directory of Open Access Journals (Sweden)

G. Chisham

2000-02-01

Full Text Available We present data from conjugate SuperDARN radars describing the high-latitude ionosphere's response to changes in the direction of IMF By during a period of steady IMF Bz southward and Bx positive. During this interval, the radars were operating in a special mode which gave high-time resolution data (30 s sampling period on three adjacent beams with a full scan every 3 min. The location of the radars around magnetic local noon at the time of the event allowed detailed observations of the variations in the ionospheric convection patterns close to the cusp region as IMF By varied. A significant time delay was observed in the ionospheric response to the IMF By changes between the two hemispheres. This is explained as being partially a consequence of the location of the dominant merging region on the magnetopause, which is ~8-12RE closer to the northern ionosphere than to the southern ionosphere (along the magnetic field line due to the dipole tilt of the magnetosphere and the orientation of the IMF. This interpretation supports the anti-parallel merging hypothesis and highlights the importance of the IMF Bx component in solar wind-magnetosphere coupling.Key words: Ionosphere (plasma convection - Magnetospheric physics (magnetopause, cusp, and boundary layers; solar wind - magnetosphere interactions

Possibility of detecting magnetospheric radio bursts from Uranus and Neptune

International Nuclear Information System (INIS)

Kennel, C.F.; Maggs, J.E.

1976-01-01

It is known that Earth, Jupiter and Saturn are sources of intense sporadic bursts of electromagnetic radiation, known as magnetospheric radio bursts. These bursts are here described. It is thought that the similarities in the power flux spectra, together with the burst occurrence patterns, suggest a common physical origin for these bursts in all three planets. The common mechanism may be noise amplification by field aligned currents, since it has been shown that the Earth's MRBs are associated with bright auroral arcs that involve intense field aligned currents. Such currents result from the interaction of the solar wind with the magnetosphere and should be a general feature of the interaction between the solar wind and planetary magnetospheres. If MRBs are produced by solar wind-magnetosphere interaction their total radiated power might scale with the solar wind input into the magnetosphere, and it has been suggested that the frequency of emission scales with the polar magnetic field strength of a planet. The intensity of MRBs is here scaled to the solar wind input and the frequency of emission to the polar field strength with a view to estimating the possibility of detecting MRBs from Uranus and Neptune. It is found that scaling of MRB power to the solar wind-magnetosphere dissipation power is probably a reasonable hypothesis. It is suggested that detection of MRB bursts from Uranus and Neptune might be a reasonable radioastronomy objective on future missions to the outer Solar System. (U.K.)

Recent progress in understanding of the ion composition in the magnetosphere and some major question mark

International Nuclear Information System (INIS)

Hultqvist, B.

1981-06-01

The observations of the energetic ion composition in the magnetosphere are reviewed with the emphasis on the recent measurements by means of GEOS-1 and -2, ISEE-1 and 2, PROGNOZ-7 and SCATHA. The observations are compared with the predictions of the open magnetosphere model. One of the major conclusions is that there are processes in the magnetosphere which play a much larger part than the model, as hitherto presented, predicts. Direct ejection of ionospheric ions, in combination with acceleration, along closed as well as open field lines may even be the dominating source process for the ring current/inner plasma sheet in magnetic storms. In very disturbed conditions this ejection mechanism must work over most of the hemispheres poleward of say 50degrees. Circulation of the ionospheric ions through the tail of the magnetosphere is not likely to be of primary importance for the energization of these ions in very disturbed conditions. (author)

Ionospheric disturbance dynamo

International Nuclear Information System (INIS)

Blanc, M.; Richmond, A.D.

1980-01-01

A numerical simulation study of the thermospheric winds produced by auroral heating during magnetic storms, and of their global dynamo effects, establishes the main features of the ionospheric disturbanc dynamo. Driven by auroral heating, a Hadley cell is created with equatorward winds blowing above about 120 km at mid-latitudes. The transport of angular momentum by these winds produces a subrotation of the midlatitude thermosphere, or westward motion with respect to the earth. The westward winds in turn drive equatorward Pedersen currents which accumulate charge toward the equator, resulting in the generation of a poleward electric field, a westward E x B drift, and an eastward current. When realistic local time conductivity variations are simulated, the eastward mid-latitude current is found to close partly via lower latitudes, resulting in an 'anti-Sq' type of current vortex. Both electric field and current at low latitudes thus vary in opposition to their normal quiet-day behavior. This total pattern of distrubance winds, electric fields, and currents is superimposed upon the background quiet-day pattern. When the neutral winds are artificially confined on the nightside, the basic pattern of predominantly westward E x B plasma drifts still prevails on the nightside but no longer extends into the dayside. Considerable observational evidence exists, suggesting that the ionospheric disturbance dynamo has an appreciable influence on storm-time ionospheric electric fields at middle and low latitudes

Magnetosphere-thermosphere coupling: An experiment in interactive modeling

International Nuclear Information System (INIS)

Forbes, J.M.; Harel, M.

1989-01-01

The Rice convection model (RCM) is utilized to investigate the electrodynamic coupling between the inner magnetosphere and the thermosphere including the effects of EUV- and convection-driven neutral winds under quasi-equilibrium conditions. A unique aspect of the study is that the convection-driven winds are included self-consistently and interactively; that is, a steady state wind parameterization is written analytically in terms of the electrostatic potential, which is in turn included in a closed-loop calculation for the electric potential itself. Simulations are performed from 1,400 UT to 1,600 UT during the CDAW-6 interval on March 22, 1979, when the cross-cap electric potential attains values of order 140-180 kV. During the early phases of the disturbance when the normal shielding from high latitudes breaks down, the neutral winds do not modify appreciably the disturbance electric fields at middle and low latitudes. As the system approaches a quasi-equilibrium state, the neutral winds play a much more significant role. The convection driven component of the neutral wind similarly acts to reduce the southward field in the noon sector, but gives rise to an enhancement in the dusk sector field extending to middle latitudes. The parameterized Pedersen effective winds are of order 300 ms -1 and reflect the familiar two-cell pattern with antisunward flow over the polar cap and return flows in the dawn and dusk sectors. These amplitudes and similarity with the ion drift motions reflect the relatively large contributions to the Pedersen effective winds originating in the upper E region and lower F region of the ionosphere. Possibilities for introducing further sophistication into the wind parameterization are discussed, as well as ramifications of the present study on the possible merging of the RCM with the NCAR TGCM to attain a higher degree of self-consistency and reality in modelling efforts

Substorm-related thermospheric density and wind disturbances derived from CHAMP observations

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P. Ritter

2010-06-01

Full Text Available The input of energy and momentum from the magnetosphere is most efficiently coupled into the high latitude ionosphere-thermosphere. The phenomenon we are focusing on here is the magnetospheric substorm. This paper presents substorm related observations of the thermosphere derived from the CHAMP satellite. With its sensitive accelerometer the satellite can measure the air density and zonal winds. Based on a large number of substorm events the average high and low latitude thermospheric response to substorm onsets was deduced. During magnetic substorms the thermospheric density is enhanced first at high latitudes. Then the disturbance travels at an average speed of 650 m/s to lower latitudes, and 3–4 h later the bulge reaches the equator on the night side. Under the influence of the Coriolis force the travelling atmospheric disturbance (TAD is deflected westward. In accordance with present-day atmospheric models the disturbance zonal wind velocities during substorms are close to zero near the equator before midnight and attain moderate westward velocities after midnight. In general, the wind system is only weakly perturbed (Δvy<20 m/s by substorms.

Structure of Mercury's magnetosphere for different pressure of the solar wind: Three dimensional hybrid simulations

Czech Academy of Sciences Publication Activity Database

Trávníček, Pavel; Hellinger, Petr; Schriver, D.

2007-01-01

Roč. 34, č. 5 (2007), L05104/1-L05104/5 ISSN 0094-8276 R&D Projects: GA ČR GA205/05/1011 Institutional research plan: CEZ:AV0Z30420517 Keywords : Global simulations * Mercury's magnetosphere * solar wind * hybrid simulations * ion drift driven rings Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.744, year: 2007

Ionospheric feedback effects on the quasi-stationary coupling between LLBL and postnoon/evening discrete auroral arcs

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M. M. Echim

2008-05-01

Full Text Available We discuss a model for the quasi-stationary coupling between magnetospheric sheared flows in the dusk sector and discrete auroral arcs, previously analyzed for the case of a uniform height-integrated Pedersen conductivity (Σ_P. Here we introduce an ionospheric feedback as the variation of Σ_P with the energy flux of precipitating magnetospheric electrons (ε_em. One key-component of the model is the kinetic description of the interface between the duskward LLBL and the plasma sheet that gives the profile of Φ_m, the magnetospheric electrostatic potential. The velocity shear in the dusk LLBL plays the role of a generator for the auroral circuit closing through Pedersen currents in the auroral ionosphere. The field-aligned current density, j_||, and the energy flux of precipitating electrons are given by analytic functions of the field-aligned potential drop, ΔΦ, derived from standard kinetic models of the adiabatic motion of particles. The ionospheric electrostatic potential, Φ_i (and implicitely ΔΦ is determined from the current continuity equation in the ionosphere. We obtain values of ΔΦ of the order of kilovolt and of j_|| of the order of tens of μA/m² in thin regions of the order of several kilometers at 200 km altitude. The spatial scale is significantly smaller and the peak values of ΔΦ, j_|| and ε_em are higher than in the case of a uniform Σ_P. Effects on the postnoon/evening auroral arc electrodynamics due to variations of dusk LLBL and solar wind dynamic and kinetic pressure are discussed. In thin regions (of the order of kilometer embedding the maximum of ΔΦ we evidence a non-linear regime of the current-voltage relationship. The model predicts also that visible arcs form when the velocity shear in LLBL is above a threshold value depending on the generator and

Conditions for double layers in the Earth's magnetosphere and perhaps in other astrophysical objects

International Nuclear Information System (INIS)

Lyons, L.R.

1987-01-01

Double layers form along auroral field lines in the Earth's magnetosphere. They form in order to maintain current continuity in the ionosphere in the presence of a magnetospheric electric field E with nabla x E is not equal to 0. Features which govern the formation of the double layers are: (1) the divergence of E, (2) the conductivity of the ionosphere, and (3) the current-voltage characteristics of auroral magnetic field lines. Astrophysical situations where nabla x E is not equal to 0 is applied to a conducting plasma similar to the Earth's ionosphere are potential candidates for the formation of double layers. The region with nabla x E is not equal to 0 can be generated within, or along field lines connected to, the conducting plasma. In addition to nabla x E, shear neutral flow in the conducting plasma can also form double layers

A Review of Low Frequency Electromagnetic Wave Phenomena Related to Tropospheric-Ionospheric Coupling Mechanisms

Science.gov (United States)

Simoes, Fernando; Pfaff, Robert; Berthelier, Jean-Jacques; Klenzing, Jeffrey

2012-01-01

Investigation of coupling mechanisms between the troposphere and the ionosphere requires a multidisciplinary approach involving several branches of atmospheric sciences, from meteorology, atmospheric chemistry, and fulminology to aeronomy, plasma physics, and space weather. In this work, we review low frequency electromagnetic wave propagation in the Earth-ionosphere cavity from a troposphere-ionosphere coupling perspective. We discuss electromagnetic wave generation, propagation, and resonance phenomena, considering atmospheric, ionospheric and magnetospheric sources, from lightning and transient luminous events at low altitude to Alfven waves and particle precipitation related to solar and magnetospheric processes. We review in situ ionospheric processes as well as surface and space weather phenomena that drive troposphere-ionosphere dynamics. Effects of aerosols, water vapor distribution, thermodynamic parameters, and cloud charge separation and electrification processes on atmospheric electricity and electromagnetic waves are reviewed. We also briefly revisit ionospheric irregularities such as spread-F and explosive spread-F, sporadic-E, traveling ionospheric disturbances, Trimpi effect, and hiss and plasma turbulence. Regarding the role of the lower boundary of the cavity, we review transient surface phenomena, including seismic activity, earthquakes, volcanic processes and dust electrification. The role of surface and atmospheric gravity waves in ionospheric dynamics is also briefly addressed. We summarize analytical and numerical tools and techniques to model low frequency electromagnetic wave propagation and solving inverse problems and summarize in a final section a few challenging subjects that are important for a better understanding of tropospheric-ionospheric coupling mechanisms.

Auroral kilometric radiation and magnetospheric substorm

International Nuclear Information System (INIS)

Morioka, Akira; Oya, Hiroshi

1980-01-01

The auroral kilometric radiation (AKR) and its relation to the development of the magnetospheric substorm have been studied based on the data obtained by JIKIKEN (EXOS-B) satellite. The occurrence of AKR is closely correlated to the intense UHR emission outside the plasmapause at the satellite position; the evidence clearly suggests that the development of the field aligned current system is associated with AKR generated at the upward current region and with the UHR emission at the downward current region. The drifting plasma due to the electric field that is generated in the magnetosphere at the moment of the magnetospheric substorm is derived from the frequency change of the plasma waves. The enhancement of the westward electric field in the duskside magnetosphere is detected simultaneously with the appearence of AKR. The altitude of the center of the AKR source region varies with intimate relation to the substorm activity suggesting that the generation of AKR is taking place in the region where the polar ionosphere and the magnetosphere are predominantly coupling through the precipitating or up going particles. From the fine structure of the dynamic spectra of AKR, it is suggested that the source of AKR might be closely related to the double layer type electric field along the magnetic field. (author)

Detailed Dayside Auroral Morphology as a Function of Local Time for southeast IMF Orientation: Implications for Solar Wind-Magnetosphere Coupling

National Research Council Canada - National Science Library

Sandholt, P. E; Farrugia, C. J; Denig, W. F

2004-01-01

...:00 magnetic local time (MLT) and discuss the relationship of this structure to solar wind-magnetosphere interconnection topology and the different stages of evolution of open field lines in the Dungey convection cycle...

Geomagnetic response to sudden expansions of the magnetosphere

International Nuclear Information System (INIS)

Araki, Tohru; Nagano, Hiroshi

1988-01-01

The geomagnetic response to five successive sudden expansions of the magnetosphere was examined by the use of magnetic data observed on the ground and by satellites. At the geosynchronous orbit between 0800 and 1100 LT the magnetic field component parallel to Earth's rotation axis decreased successively. The amplitude and the fall time of each decrease were 20-30 nT and 2.5-3.5 min, respectively. The decrease was propagated about 10 min later to the distance of about 31 R E from Earth in the antisunward direction, indicating propagation speed of about 300 km/s. The H component of ground magnetograms from low-latitude stations showed decreases with waveform similar to that at the geosynchronous orbit, but each decrease at the dayside equator was greatly enhanced and preceded by a short small positive impulse. Each of the corresponding geomagnetic variations at high latitude stations consisted of two successive sharp pulses of opposite sense with 2-3 min duration. The dominant component and the sense of these high-latitude pulses were highly dependent upon local time and latitude. The distribution of equivalent ionospheric current arrows for each high-latitude pulse showed clear twin vortices centered at 70-76 degree geomagnetic latitude in the dayside and was approximately symmetric with respect to the noon meridian. The current direction of the vortices was reversed from the first pulse to the second. it suggests successive appearance of a dawn-to-dusk and then a dusk-to-dawn electric field, both of which were transmitted from the magnetosphere to the polar ionosphere. The effect of ionospheric currents due to these polar electric fields was superposed on the simple magnetic decrease produced by an expansion of the whole magnetosphere and produced the complex waveform distribution on the ground

Propagation of ULF waves through the ionosphere: Inductive effect for oblique magnetic fields

Directory of Open Access Journals (Sweden)

M. D. Sciffer

2004-04-01

Full Text Available Solutions for ultra-low frequency (ULF wave fields in the frequency range 1–100mHz that interact with the Earth's ionosphere in the presence of oblique background magnetic fields are described. Analytic expressions for the electric and magnetic wave fields in the magnetosphere, ionosphere and atmosphere are derived within the context of an inductive ionosphere. The inductive shielding effect (ISE arises from the generation of an "inductive" rotational current by the induced part of the divergent electric field in the ionosphere which reduces the wave amplitude detected on the ground. The inductive response of the ionosphere is described by Faraday's law and the ISE depends on the horizontal scale size of the ULF disturbance, its frequency and the ionosphere conductivities. The ISE for ULF waves in a vertical background magnetic field is limited in application to high latitudes. In this paper we examine the ISE within the context of oblique background magnetic fields, extending studies of an inductive ionosphere and the associated shielding of ULF waves to lower latitudes. It is found that the dip angle of the background magnetic field has a significant effect on signals detected at the ground. For incident shear Alfvén mode waves and oblique background magnetic fields, the horizontal component of the field-aligned current contributes to the signal detected at the ground. At low latitudes, the ISE is larger at smaller conductivity values compared with high latitudes.

Key words. Ionosphere (ionosphere-magnetosphere interactions; electric fields and currents; wave propagation

Jupiter's Magnetosphere: Plasma Description from the Ulysses Flyby.

Science.gov (United States)

Bame, S J; Barraclough, B L; Feldman, W C; Gisler, G R; Gosling, J T; McComas, D J; Phillips, J L; Thomsen, M F; Goldstein, B E; Neugebauer, M

1992-09-11

Plasma observations at Jupiter show that the outer regions of the Jovian magnetosphere are remarkably similar to those of Earth. Bow-shock precursor electrons and ions were detected in the upstream solar wind, as at Earth. Plasma changes across the bow shock and properties of the magnetosheath electrons were much like those at Earth, indicating that similar processes are operating. A boundary layer populated by a varying mixture of solar wind and magnetospheric plasmas was found inside the magnetopause, again as at Earth. In the middle magnetosphere, large electron density excursions were detected with a 10-hour periodicity as planetary rotation carried the tilted plasma sheet past Ulysses. Deep in the magnetosphere, Ulysses crossed a region, tentatively described as magnetically connected to the Jovian polar cap on one end and to the interplanetary magnetic field on the other. In the inner magnetosphere and lo torus, where corotation plays a dominant role, measurements could not be made because of extreme background rates from penetrating radiation belt particles.

Magnetospheric energy inputs into the upper atmospheres of the giant planets

Directory of Open Access Journals (Sweden)

C. G. A. Smith

2005-07-01

Full Text Available We revisit the effects of Joule heating upon the upper atmospheres of Jupiter and Saturn. We show that in addition to direct Joule heating there is an additional input of kinetic energy – ion drag energy – which we quantify relative to the Joule heating. We also show that fluctuations about the mean electric field, as observed in the Earth's ionosphere, may significantly increase the Joule heating itself. For physically plausible parameters these effects may increase previous estimates of the upper atmospheric energy input at Saturn from ~10 TW to ~20 TW.

Keywords. Ionosphere (Electric fields and currents; Planetary ionosphere – Magnetospheric physics (Auroral phenomena

Identifying Cassini's Magnetospheric Location Using Magnetospheric Imaging Instrument (MIMI) Data and Machine Learning

Science.gov (United States)

Vandegriff, J. D.; Smith, G. L.; Edenbaum, H.; Peachey, J. M.; Mitchell, D. G.

2017-12-01

We analyzed data from Cassini's Magnetospheric Imaging Instrument (MIMI) and Magnetometer (MAG) and attempted to identify the region of Saturn's magnetosphere that Cassini was in at a given time using machine learning. MIMI data are from the Charge-Energy-Mass Spectrometer (CHEMS) instrument and the Low-Energy Magnetospheric Measurement System (LEMMS). We trained on data where the region is known based on a previous analysis of Cassini Plasma Spectrometer (CAPS) plasma data. Three magnetospheric regions are considered: Magnetosphere, Magnetosheath, and Solar Wind. MIMI particle intensities, magnetic field values, and spacecraft position are used as input attributes, and the output is the CAPS-based region, which is available from 2004 to 2012. We then use the trained classifier to identify Cassini's magnetospheric regions for times after 2012, when CAPS data is no longer available. Training accuracy is evaluated by testing the classifier performance on a time range of known regions that the classifier has never seen. Preliminary results indicate a 68% accuracy on such test data. Other techniques are being tested that may increase this performance. We present the data and algorithms used, and will describe the latest results, including the magnetospheric regions post-2012 identified by the algorithm.

Solar Wind Interaction and Impact on the Venus Atmosphere

Science.gov (United States)

Futaana, Yoshifumi; Stenberg Wieser, Gabriella; Barabash, Stas; Luhmann, Janet G.

2017-11-01

Venus has intrigued planetary scientists for decades because of its huge contrasts to Earth, in spite of its nickname of "Earth's Twin". Its invisible upper atmosphere and space environment are also part of the larger story of Venus and its evolution. In 60s to 70s, several missions (Venera and Mariner series) explored Venus-solar wind interaction regions. They identified the basic structure of the near-Venus space environment, for example, existence of the bow shock, magnetotail, ionosphere, as well as the lack of the intrinsic magnetic field. A huge leap in knowledge about the solar wind interaction with Venus was made possible by the 14-year long mission, Pioneer Venus Orbiter (PVO), launched in 1978. More recently, ESA's probe, Venus Express (VEX), was inserted into orbit in 2006, operated for 8 years. Owing to its different orbit from that of PVO, VEX made unique measurements in the polar and terminator regions, and probed the near-Venus tail for the first time. The near-tail hosts dynamic processes that lead to plasma energization. These processes in turn lead to the loss of ionospheric ions to space, slowly eroding the Venusian atmosphere. VEX carried an ion spectrometer with a moderate mass-separation capability and the observed ratio of the escaping hydrogen and oxygen ions in the wake indicates the stoichiometric loss of water from Venus. The structure and dynamics of the induced magnetosphere depends on the prevailing solar wind conditions. VEX studied the response of the magnetospheric system on different time scales. A plethora of waves was identified by the magnetometer on VEX; some of them were not previously observed by PVO. Proton cyclotron waves were seen far upstream of the bow shock, mirror mode waves were observed in magnetosheath and whistler mode waves, possibly generated by lightning discharges were frequently seen. VEX also encouraged renewed numerical modeling efforts, including fluid-type of models and particle-fluid hybrid type of models

Outer Magnetospheric Boundaries Cluster Results

CERN Document Server

Paschmann, Goetz; Schwartz, S J

2006-01-01

When the stream of plasma emitted from the Sun (the solar wind) encounters Earth's magnetic field, it slows down and flows around it, leaving behind a cavity, the magnetosphere. The magnetopause is the surface that separates the solar wind on the outside from the Earth's magnetic field on the inside. Because the solar wind moves at supersonic speed, a bow shock must form ahead of the magnetopause that acts to slow the solar wind to subsonic speeds. Magnetopause, bow shock and their environs are rich in exciting processes in collisionless plasmas, such as shock formation, magnetic reconnection, particle acceleration and wave-particle interactions. They are interesting in their own right, as part of Earth's environment, but also because they are prototypes of similar structures and phenomena that are ubiquitous in the universe, having the unique advantage that they are accessible to in situ measurements. The boundaries of the magnetosphere have been the target of direct in-situ measurements since the beginning ...

Ionospheric Irregularities at Mars Probed by MARSIS Topside Sounding

Science.gov (United States)

Harada, Y.; Gurnett, D. A.; Kopf, A. J.; Halekas, J. S.; Ruhunusiri, S.

2018-01-01

The upper ionosphere of Mars contains a variety of perturbations driven by solar wind forcing from above and upward propagating atmospheric waves from below. Here we explore the global distribution and variability of ionospheric irregularities around the exobase at Mars by analyzing topside sounding data from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument on board Mars Express. As irregular structure gives rise to off-vertical echoes with excess propagation time, the diffuseness of ionospheric echo traces can be used as a diagnostic tool for perturbed reflection surfaces. The observed properties of diffuse echoes above unmagnetized regions suggest that ionospheric irregularities with horizontal wavelengths of tens to hundreds of kilometers are particularly enhanced in the winter hemisphere and at high solar zenith angles. Given the known inverse dependence of neutral gravity wave amplitudes on the background atmospheric temperature, the ionospheric irregularities probed by MARSIS are most likely associated with plasma perturbations driven by atmospheric gravity waves. Though extreme events with unusually diffuse echoes are more frequently observed for high solar wind dynamic pressures during some time intervals, the vast majority of the diffuse echo events are unaffected by varying solar wind conditions, implying limited influence of solar wind forcing on the generation of ionospheric irregularities. Combination of remote and in situ measurements of ionospheric irregularities would offer the opportunity for a better understanding of the ionospheric dynamics at Mars.

Modelling Mercury's magnetosphere and plasma entry through the dayside magnetopause

Science.gov (United States)

Massetti, S.; Orsini, S.; Milillo, A.; Mura, A.

2007-09-01

Owing to the next space mission Messenger (NASA) and BepiColombo (ESA/JAXA), there is a renewed interest in modelling the Mercury's environment. The geometry of the Mercury's magnetosphere, as well as its response to the solar wind conditions, is one of the major issues. The weak magnetic field of the planet and the increasing weight of the IMF BX component at Mercury's orbit, introduce critical differences with respect to the Earth's case, such as a strong north-south asymmetry and a significant solar wind precipitation into the dayside magnetosphere even for non-negative IMF BZ. With the aim of analysing the interaction between the solar wind and Mercury's magnetosphere, we have developed an empirical-analytical magnetospheric model starting from the Toffoletto-Hill TH93 code. Our model has been tuned to reproduce the key features of the Mariner 10 magnetic data, and to mimic the magnetic field topology obtained by the self-consistent hybrid simulation developed by Kallio and Janhunen [Solar wind and magnetospheric ion impact on Mercury's magnetosphere. Geophys. Res. Lett. 30, 1877, doi: 10.1029/2003GL017842]. The new model has then been used to study the effect of the magnetic reconnection on the magnetosheath plasma entry through the open areas of the dayside magnetosphere (cusps), which are expected to be one of the main sources of charged particles circulating inside the magnetosphere. We show that, depending on the Alfvén speeds on both sides of the magnetopause discontinuity, the reconnection process would be able to accelerate solar wind protons up to few tens of keV: part of these ions can hit the surface and then trigger, via ion-sputtering, the refilling of the planetary exosphere. Finally, we show that non-adiabatic effects are expected to develop in the cusp regions as the energy gained by injected particles increases. The extent of these non-adiabatic regions is shown to be also modulated by upstream IMF condition.

Dynamics of the polar ionosphere structure disturbance in the Svalgaard-Mansurov effect

International Nuclear Information System (INIS)

Osipov, N.K.; Mozhaev, A.M.; Larina, T.N.; Ponomarev, Yu.N.

1988-01-01

Nonstationary disturbance model of the ionsphere of polar caps caused by change of B y component sign of interplanetary magnetic field is considered. It is shown that nonstationary convection transfer of ionospheric plasma represents the main and the most fast mechanism regulating reconstruction of ionosphere structure in polar caps during magnetosphere substorms, caused by the change of B y sign. Calculations show that characteristic time of sufficient change of ionosphere structure at ∼1500 km distances is on the order of 10-25 min

Significance of Dungey-cycle flows in Jupiter's and Saturn's magnetospheres, and their identification on closed equatorial field lines

Directory of Open Access Journals (Sweden)

S. V. Badman

2007-05-01

Full Text Available We consider the contribution of the solar wind-driven Dungey-cycle to flux transport in Jupiter's and Saturn's magnetospheres, the associated voltages being based on estimates of the magnetopause reconnection rates recently derived from observations of the interplanetary medium in the vicinity of the corresponding planetary orbits. At Jupiter, the reconnection voltages are estimated to be ~150 kV during several-day weak-field rarefaction regions, increasing to ~1 MV during few-day strong-field compression regions. The corresponding values at Saturn are ~25 kV for rarefaction regions, increasing to ~150 kV for compressions. These values are compared with the voltages associated with the flows driven by planetary rotation. Estimates of the rotational flux transport in the "middle" and "outer" magnetosphere regions are shown to yield voltages of several MV and several hundred kV at Jupiter and Saturn respectively, thus being of the same order as the estimated peak Dungey-cycle voltages. We conclude that under such circumstances the Dungey-cycle "return" flow will make a significant contribution to the flux transport in the outer magnetospheric regions. The "return" Dungey-cycle flows are then expected to form layers which are a few planetary radii wide inside the dawn and morning magnetopause. In the absence of significant cross-field plasma diffusion, these layers will be characterized by the presence of hot light ions originating from either the planetary ionosphere or the solar wind, while the inner layers associated with the Vasyliunas-cycle and middle magnetosphere transport will be dominated by hot heavy ions originating from internal moon/ring plasma sources. The temperature of these ions is estimated to be of the order of a few keV at Saturn and a few tens of keV at Jupiter, in both layers.

Ionospheric and boundary contributions to the Dessler-Parker-Sckopke formula for Dst

Directory of Open Access Journals (Sweden)

V. M. Vasyliūnas

2006-05-01

Full Text Available The Dessler-Parker-Sckopke formula for the disturbance magnetic field averaged over the Earth's surface, universally used to interpret the geomagnetic Dst index, can be generalized, by using the well known method of deriving it from the virial theorem, to include the effects of ionospheric currents. There is an added term proportional to the global integral of the vertical mechanical force that balances the vertical component of the Lorentz force J×B/c in the ionosphere; a downward mechanical force reduces, and an upward increases, the depression of the magnetic field. If the vertical component of the ionospheric Ohm's law holds exactly, the relevant force on the plasma is the collisional friction between the neutral atmosphere and the vertically flowing plasma. An equal and opposite force is exerted on the neutral atmosphere and thus appears in its virial theorem. The ionospheric effect on Dst can then be related to the changes of kinetic and gravitational energy contents of the neutral atmosphere; since these changes are brought about by energy input from the magnetosphere, there is an implied upper limit to the effect on Dst which in general is relatively small in comparison to the contribution of the plasma energy content in the magnetosphere. Hence the Dessler-Parker-Sckopke formula can be applied without major modification, even in the case of strong partial ring currents; the ionospheric closure currents implied by the local time asymmetry have only a relatively small effect on the globally averaged disturbance field, comparable to other sources of uncertainty. When derived from the virial theorem applied to a bounded volume (e.g. the magnetosphere bounded by the magnetopause and a cross-section of the magnetotail, the Dessler-Parker-Sckopke formula contains also several boundary surface terms which can be identified as contributions of the magnetopause (Chapman-Ferraro and of the magnetotail currents.

Ionospheric effects during severe space weather events seen in ionospheric service data products

Science.gov (United States)

Jakowski, Norbert; Danielides, Michael; Mayer, Christoph; Borries, Claudia

Space weather effects are closely related to complex perturbation processes in the magnetosphere-ionosphere-thermosphere systems, initiated by enhanced solar energy input. To understand and model complex space weather processes, different views on the same subject are helpful. One of the ionosphere key parameters is the Total Electron Content (TEC) which provides a first or-der approximation of the ionospheric range error in Global Navigation Satellite System (GNSS) applications. Additionally, horizontal gradients and time rate of change of TEC are important for estimating the perturbation degree of the ionosphere. TEC maps can effectively be gener-ated using ground based GNSS measurements from global receiver networks. Whereas ground based GNSS measurements provide good horizontal resolution, space based radio occultation measurements can complete the view by providing information on the vertical plasma density distribution. The combination of ground based TEC and vertical sounding measurements pro-vide essential information on the shape of the vertical electron density profile by computing the equivalent slab thickness at the ionosonde station site. Since radio beacon measurements at 150/400 MHz are well suited to trace the horizontal structure of Travelling Ionospheric Dis-turbances (TIDs), these data products essentially complete GNSS based TEC mapping results. Radio scintillation data products, characterising small scale irregularities in the ionosphere, are useful to estimate the continuity and availability of transionospheric radio signals. The different data products are addressed while discussing severe space weather events in the ionosphere e.g. events in October/November 2003. The complementary view of different near real time service data products is helpful to better understand the complex dynamics of ionospheric perturbation processes and to forecast the development of parameters customers are interested in.

Relationship of upflowing ion beams and conics around the dayside cusp/cleft region to the interplanetary conditions

Directory of Open Access Journals (Sweden)

W. Miyake

2002-04-01

Full Text Available The dayside cusp/cleft region is known as a major source of upflowing ionospheric ions to the magnetosphere. Since the ions are supposed to be energized by an input of energy from the dayside magnetospheric boundary region, we examined the possible influence of the interplanetary conditions on dayside ion beams and conics observed by the polar-orbiting Exos-D (Akebono satellite. We found that both the solar wind velocity and density, as well as IMF By and Bz , affect the occurrence frequency of ion conics. The energy of ion conics also depends on the solar wind velocity, IMF By and Bz . The ion beams around the local noon are not significantly controlled by the interplanetary conditions. The results reveal that ion convection, as well as the energy source, is important to understand the production of dayside ion conics while that of ion beams basically reflects the intensity of local field-aligned currents.Key words. Ionosphere (particle acceleration – magnetospheric physics (magnetopause, cusp, and boundary layers; magnetosphere ionosphere interaction

Advances in magnetospheric storm and substorm research: 1989-1991

International Nuclear Information System (INIS)

Fairfield, D.H.

1992-01-01

Geomagnetic storms represent the magnetospheric response to fast solar wind and unusually large southward interplanetary magnetic fields that are caused by solar processes and resulting dynamics in the interplanetary medium. The solar wind/magnetosphere interaction is, however, more commonly studied via smaller, more common, magnetospheric substorms. Accumulating evidence suggests that two separate magnetospheric current systems are important during magnetospheric substorms. Currents directly driven by the solar wind/magnetosphere interaction produce magnetic field variations that make important contributions to the AE index but have little relation to the many effects traditionally associated with sudden substorm onsets. Currents driven by energy unloaded from the magnetotail form the nightside current wedge and are associated with onset effects such as auroral breakup, field dipolarization, and particle acceleration. Observations are gradually leading to a coherent picture of the interrelations among these various onset phenomena, but their cause remains a controversial question. The abrupt nature of substorm onsets suggests a magnetospheric instability, but doubt remains as to its nature and place of origin. Measurements increasingly suggest the region of 7-10 R E near midnight as the likely point of origin, but it is not clear that the long-popular tearing mode can go unstable this close to the Earth, where it may be stabilized by a small northward field component. Also the tailward flows that would be expected tailward of a near-Earth neutral line are seldom seen inside of 19 R E . The changing magnetic field configuration during substorms means that existing static models cannot be used to map phenomena between the magnetosphere and the ground at these interesting times

The Electric Wind of Venus: A Global and Persistent Polar Wind -Like Ambipolar Electric Field Sufficient for the Direct Escape of Heavy Ionospheric Ions

Science.gov (United States)

Collinson, Glyn A.; Frahm, Rudy A.; Glocer, Alex; Coates, Andrew J.; Grebowsky, Joseph M.; Barabash, Stas; Domagal-Goldman, Shawn D.; Federov, Andrei; Futaana, Yoshifumi; Gilbert, Lin K.;

Assimilative Modeling of Ionospheric Disturbances with FORMOSAT-3/COSMIC and Ground-Based GPS Measurements

Directory of Open Access Journals (Sweden)

Xiaoqing Pi

2009-01-01

Full Text Available The four-dimensional Global Assimilative Ionospheric Model (GAIM is applied to a study of ionospheric disturbances. The investigation is focused on disturbance features, particularly in the altitude and latitude dimensions, at low latitudes during a geomagnetic storm on 7 August 2006, under solar minimum conditions. The modeling of storm-time ionospheric state (electron density is conducted by assimilating an unprecedented volume of line-of-sight TEC data collected by the Global Positioning System (GPS occultation receivers on board six FORMOSAT-3/COSMIC satellites and geodetic-quality GPS receivers at two hundred globally-distributed ground tracking stations.With a band-limited Kalman filter technique to update the ionospheric state, the assimilative modeling reveals a pronounced enhancement in the equatorial anomaly in the East Asia sector during dusk and evening hours. The disturbance characteristics, obtained by comparing with the quiet conditions prior to the storm also modeled in this study through data assimilation, include lifted F layer and reduced electron density in the equatorial region, enhanced density at the magnetically conjugate anomaly latitudes, and tilted feature of density increase towards higher altitudes at lower latitudes. The characteristics are attributed to the enhanced plasma fountain effect driven by an enhanced eastward zonal electric field. These results enable us to distinguish the storm-time electric field perturbations clearly from other sources during the storm. The possible origins of electric field perturbations are also discussed, including penetration of the magnetospheric electric field and wind dynamo disturbances.

Impulsive ion acceleration in earth's outer magnetosphere

International Nuclear Information System (INIS)

Baker, D.N.; Belian, R.D.

1985-01-01

Considerable observational evidence is found that ions are accelerated to high energies in the outer magnetosphere during geomagnetic disturbances. The acceleration often appears to be quite impulsive causing temporally brief (10's of seconds), very intense bursts of ions in the distant plasma sheet as well as in the near-tail region. These ion bursts extend in energy from 10's of keV to over 1 MeV and are closely associated with substorm expansive phase onsets. Although the very energetic ions are not of dominant importance for magnetotail plasma dynamics, they serve as an important tracer population. Their absolute intensity and brief temporal appearance bespeaks a strong and rapid acceleration process in the near-tail, very probably involving large induced electric fields substantially greater than those associated with cross-tail potential drops. Subsequent to their impulsive acceleration, these ions are injected into the outer trapping regions forming ion ''drift echo'' events, as well as streaming tailward away from their acceleration site in the near-earth plasma sheet. Most auroral ion acceleration processes occur (or are greatly enhanced) during the time that these global magnetospheric events are occurring in the magnetotail. A qualitative model relating energetic ion populations to near-tail magnetic reconnection at substorm onset followed by global redistribution is quite successful in explaining the primary observational features. Recent measurements of the elemental composition and charge-states have proven valuable for showing the source (solar wind or ionosphere) of the original plasma population from which the ions were accelerated

Change in the F region structure of a polar ionosphere at the change of the Y component sighn of the interplanetary magnetic field. Svalgaard-Mansurov effect in the ionosphere

International Nuclear Information System (INIS)

Gal'perin, Yu.I.; Zosimova, A.G.; Larina, T.N.; Mozhaev, A.M.; Osipov, N.K.; Ponomarev, Yu.N.

1980-01-01

Model calculations of the planetary picture of the polar ionosphere characteristics taking into account modern models of magnetospheric convection are carried out. The results of direct measurements of the lateral component of the convection rate in the day polar cusp region obtained by the ''Kosmos-184'' satellite in 1967 indicative of rotation of the zonal convection component direction with tha change of the Bsub(y) component sign of the interplanetary magnetic field (IMF). It is shown that the change of the IMF Bsub(y) sign and the following change of the convection picture in the polar cap must cause a quick (10 3 s) change of the planetary picture of the polar ionosphere characteristics in the F region peak and higher, i.e. ''the Svalgard-Mansurov ionospheric effect''. The amplitude of the variations and their character are defined by the relation of the solar and auroral ionization, and, therefore, they strongly depend on the universal time, season and auroral activity, that hampers comparison of the calculations with the experiment. The experimental data obtained from satellites and indicative of the reality of the described ionospheric Bsub(y) effect are presented. Thus, the data of many years on the ionospheric measurements from the Earth and satellites parallel with the magnetic measurements can be used to specify parameters describing the magnetospheric convection picture [ru

The effects of neutral inertia on ionospheric currents in the high-latitude thermosphere following a geomagnetic storm

International Nuclear Information System (INIS)

Deng, W.; Killeen, T.L.; Burns, A.G.; Roble, R.G.; Slavin, J.A.; Wharton, L.E.

1993-01-01

The authors extend previous work with a National Center for Atmospheric Research (NCAR) thermosphere/ionosphere general circulation model (TIGCM), to study dynamo effects in the high latitude thermosphere. Ionospheric convection can drive neutral currents in much the same pattern by means of ion drag reactions. It has been observed that ion currents established during magnetic storms can induce neutral currents which persist for hours after the end of the storm. Model results have shown that such currents can account for up to 80 percent of the Hall currents in the period immediately following storms. Here this previous work is extended and compared with experimental observations. The authors simulate time dependent Hall currents, field-aligned currents, and electrical power fluxes coupling the magnetosphere and ionosphere. They discuss their results in terms of a loaded magnetosphere, which accounts for the fact that the neutral currents can also induce currents and electric fields in the ionosphere

Electric fields in the magnetosphere

International Nuclear Information System (INIS)

Falthammar, C.G.

1989-01-01

Electric field measurements on the satellites GEOS-1, GEOS-2, ISEE-1, and Viking have extended the empirical knowledge of electric fields in space so as to include the outer regions of the magnetosphere. While the measurements confirm some of the theoretically expected properties of the electric fields, they also reveal unexpected features and a high degree of complexity and variability. The existence of a magnetospheric dawn-to-dusk electric field, as expected on the basis of extrapolation from low altitude measurements, is confirmed in an average sense. However, the actual field exhibits large spatial and temporal variations, including strong fields of inductive origin. At the magnetopause, the average (dawn-to-dusk directed) tangential electric field component is typically obscured by irregular fluctuations of larger amplitude. The magnetic-field aligned component of the electric field, which is of particular importance for ionosphere-magnetosphere coupling and for auroral acceleration, is even now very difficult to measure directly. However, the data from electric field measurements provide further support for the conclusion, based on a variety of evidence, that a non-vanishing magnetic-field aligned electric field exists in the auroral acceleration region

Scalar and Vector Spherical Harmonics for Assimilation of Global Datasets in the Ionosphere and Thermosphere

Science.gov (United States)

Miladinovich, D.; Datta-Barua, S.; Bust, G. S.; Ramirez, U.

2017-12-01

Understanding physical processes during storm time in the ionosphere-thermosphere (IT) system is limited, in part, due to the inability to obtain accurate estimates of IT states on a global scale. One reason for this inability is the sparsity of spatially distributed high quality data sets. Data assimilation is showing promise toward enabling global estimates by blending high quality observational data sets with established climate models. We are continuing development of an algorithm called Estimating Model Parameters for Ionospheric Reverse Engineering (EMPIRE) to enable assimilation of global datasets for storm time estimates of IT drivers. EMPIRE is a data assimilation algorithm that uses a Kalman filtering routine to ingest model and observational data. The EMPIRE algorithm is based on spherical harmonics which provide a spherically symmetric, smooth, continuous, and orthonormal set of basis functions suitable for a spherical domain such as Earth's IT region (200-600 km altitude). Once the basis function coefficients are determined, the newly fitted function represents the disagreement between observational measurements and models. We apply spherical harmonics to study the March 17, 2015 storm. Data sources include Fabry-Perot interferometer neutral wind measurements and global Ionospheric Data Assimilation 4 Dimensional (IDA4D) assimilated total electron content (TEC). Models include Weimer 2000 electric potential, International Geomagnetic Reference Field (IGRF) magnetic field, and Horizontal Wind Model 2014 (HWM14) neutral winds. We present the EMPIRE assimilation results of Earth's electric potential and thermospheric winds. We also compare EMPIRE storm time E cross B ion drift estimates to measured drifts produced from the Super Dual Auroral Radar Network (SuperDARN) and Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) measurement datasets. The analysis from these results will enable the generation of globally assimilated

Global Particle-in-Cell Simulations of Mercury's Magnetosphere

Science.gov (United States)

Schriver, D.; Travnicek, P. M.; Lapenta, G.; Amaya, J.; Gonzalez, D.; Richard, R. L.; Berchem, J.; Hellinger, P.

2017-12-01

Spacecraft observations of Mercury's magnetosphere have shown that kinetic ion and electron particle effects play a major role in the transport, acceleration, and loss of plasma within the magnetospheric system. Kinetic processes include reconnection, the breakdown of particle adiabaticity and wave-particle interactions. Because of the vast range in spatial scales involved in magnetospheric dynamics, from local electron Debye length scales ( meters) to solar wind/planetary magnetic scale lengths (tens to hundreds of planetary radii), fully self-consistent kinetic simulations of a global planetary magnetosphere remain challenging. Most global simulations of Earth's and other planet's magnetosphere are carried out using MHD, enhanced MHD (e.g., Hall MHD), hybrid, or a combination of MHD and particle in cell (PIC) simulations. Here, 3D kinetic self-consistent hybrid (ion particle, electron fluid) and full PIC (ion and electron particle) simulations of the solar wind interaction with Mercury's magnetosphere are carried out. Using the implicit PIC and hybrid simulations, Mercury's relatively small, but highly kinetic magnetosphere will be examined to determine how the self-consistent inclusion of electrons affects magnetic reconnection, particle transport and acceleration of plasma at Mercury. Also the spatial and energy profiles of precipitating magnetospheric ions and electrons onto Mercury's surface, which can strongly affect the regolith in terms of space weathering and particle outflow, will be examined with the PIC and hybrid codes. MESSENGER spacecraft observations are used both to initiate and validate the global kinetic simulations to achieve a deeper understanding of the role kinetic physics play in magnetospheric dynamics.

Magnetosphere-Ionosphere Coupling During a Geomagnetic Substorm on March 1, 2017

Science.gov (United States)

Coster, A. J.; Hampton, D. L.; Sazykin, S. Y.; Wolf, R.; Huba, J.; Varney, R. H.; Reimer, A.; Lynch, K. A.; Samara, M.; Michell, R.

2017-12-01

On March 1, 2017, at approximately 10 UT, magnetometers at Ft Yukon and Poker Flat in Alaska measured the classic signature of an auroral substorm: a rapid decrease in the northward component of the magnetic field. Nearby, a camera at Venetie Alaska captured intensive visual brightening of multiple auroral arcs at approximately the same time. Our data and model analysis focuses on this time period. We are taking advantage of the extensive instrumentation that was in place in Northern Alaska on this date due to the ISINGLASS rocket campaign. Although no rockets were flown on March 1, 2017, this substorm was monitored at Poker by the three-filter all-sky survey and at Venetie by three all-sky cameras running simultaneously with each filtered for a different wavelength. Our analysis includes co-incidental high precision GNSS receiver data providing total electron content (TEC) measurements during the overhead auroral arcs. The receiver at Venetie also monitored L-band scintillation. In addition, the Poker Flat Incoherent Scatter radar captured the rapid ionization enhancement in the 100-200 km region across multiple beams looking to the north of Poker. The timing of these events between the multiple sites is closely monitored, and inferences of the propagation of this event are described. The available SuperDARN data from this time period indicates this substorm happened at about the same time within the Harang discontinuity. This event presented an unprecedented opportunity to observe occurrence and development of a substorm with a combination of ground-based remote sensing instruments. To support our interpretation of the data, we present first simulations of the magnetosphere-ionosphere coupled system during a substorm with the self-consistently coupled SAMI/RCM code.

Interplanetary Magnetic Field Control of the Entry of Solar Energetic Particles into the Magnetosphere

Science.gov (United States)

Richard, R. L.; El-Alaoui, M.; Ashour-Abdalla, M.; Walker, R. J.

2002-01-01

We have investigated the entry of energetic ions of solar origin into the magnetosphere as a function of the interplanetary magnetic field orientation. We have modeled this entry by following high energy particles (protons and 3 He ions) ranging from 0.1 to 50 MeV in electric and magnetic fields from a global magnetohydrodynamic (MHD) model of the magnetosphere and its interaction with the solar wind. For the most part these particles entered the magnetosphere on or near open field lines except for some above 10 MeV that could enter directly by crossing field lines due to their large gyroradii. The MHD simulation was driven by a series of idealized solar wind and interplanetary magnetic field (IMF) conditions. It was found that the flux of particles in the magnetosphere and transport into the inner magnetosphere varied widely according to the IMF orientation for a constant upstream particle source, with the most efficient entry occurring under southward IMF conditions. The flux inside the magnetosphere could approach that in the solar wind implying that SEPs can contribute significantly to the magnetospheric energetic particle population during typical SEP events depending on the state of the magnetosphere.

Determining magnetospheric ULF wave activity from external drivers using the most influential solar wind parameters

Science.gov (United States)

Bentley, S.; Watt, C.; Owens, M. J.

2017-12-01

Ultra-low frequency (ULF) waves in the magnetosphere are involved in the energisation and transport of radiation belt particles and are predominantly driven by the external solar wind. By systematically examining the instantaneous relative contribution of non-derived solar wind parameters and accounting for their interdependencies using fifteen years of ground-based measurements (CANOPUS) at a single frequency and magnetic latitude, we conclude that the dominant causal parameters for ground-based ULF wave power are solar wind speed v, interplanetary magnetic field component Bz and summed power in number density perturbations δNp. We suggest that these correspond to driving by the Kelvin-Helmholtz instability, flux transfer events and direct perturbations from solar wind structures sweeping past. We will also extend our analysis to a stochastic wave model at multiple magnetic latitudes that will be used in future to predict background ULF wave power across the radiation belts in different magnetic local time sectors, and to examine the relative contribution of the parameters v, Bz and var(Np) in these sectors.

The Magnetospheric Cusps Structure and Dynamics

CERN Document Server

Fritz, Theodore A

2005-01-01

This collection of papers will address the question "What is the Magnetospheric Cusp?" and what is its role in the coupling of the solar wind to the magnetosphere as well as its role in the processes of particle transport and energization within the magnetosphere. The cusps have traditionally been described as narrow funnel-shaped regions that provide a focus of the Chapman-Ferraro currents that flow on the magnetopause, a boundary between the cavity dominated by the geomagnetic field (i.e., the magnetosphere) and the external region of the interplanetary medium. Measurements from a number of recent satellite programs have shown that the cusp is not confined to a narrow region near local noon but appears to encompass a large portion of the dayside high-latitude magnetosphere and it appears that the cusp is a major source region for the production of energetic charged particles for the magnetosphere. Audience: This book will be of interest to space science research organizations in governments and industries, ...

Uplift of Ionospheric Oxygen Ions During Extreme Magnetic Storms

Science.gov (United States)

Tsurutani, Bruce T.; Mannucci, Anthony J.; Verkhoglyadova, Olga P.; Huba, Joseph; Lakhina, Gurbax S.

2013-01-01

Research reported earlier in literature was conducted relating to estimation of the ionospheric electrical field, which may have occurred during the September 1859 Carrington geomagnetic storm event, with regard to modern-day consequences. In this research, the NRL SAMI2 ionospheric code has been modified and applied the estimated electric field to the dayside ionosphere. The modeling was done at 15-minute time increments to track the general ionospheric changes. Although it has been known that magnetospheric electric fields get down into the ionosphere, it has been only in the last ten years that scientists have discovered that intense magnetic storm electric fields do also. On the dayside, these dawn-to-dusk directed electric fields lift the plasma (electrons and ions) up to higher altitudes and latitudes. As plasma is removed from lower altitudes, solar UV creates new plasma, so the total plasma in the ionosphere is increased several-fold. Thus, this complex process creates super-dense plasmas at high altitudes (from 700 to 1,000 km and higher).

IMF BY and the seasonal dependences of the electric field in the inner magnetosphere

Directory of Open Access Journals (Sweden)

H. Matsui

2005-10-01

Full Text Available It is known that the electric field pattern at high latitudes depends on the polarity of the Y component of the interplanetary magnetic field (IMF BY and season. In this study, we investigate the seasonal and BY dependences in the inner magnetosphere using the perigee (4magnetosphere. These data are sorted by the polarities of IMF BZ and BY, and by seasons or hemispheres. It is demonstrated from our statistics that the electric fields in the inner magnetosphere depend on these quantities. The following three points are inferred: 1 The electric fields exhibit some differences statistically between Cluster locations at the Northern and Southern Hemispheres with the same dipole L and magnetic local time (MLT values and during the same IMF conditions. These differences in the electric fields might result from hemispherical differences in magnetic field geometry and/or those in field-aligned potential difference. 2 The IMF BY and seasonal dependence of the dawnside and duskside electric fields at 4ionospheric conductivity and the field-aligned current. 3 The nightside electric field in the inner magnetosphere measured by Cluster is often similar to that in the magnetotail lobe. In the future, it will be necessary to incorporate these dependencies on IMF BY and season into a realistic model of the inner magnetospheric convection electric field. Keywords. Magnetospheric physics (Electric fields; Magnetosphere-ionosphere interactions; Solar windmagnetosphere interactions

The location of the open-closed magnetic field line boundary in the dawn sector auroral ionosphere

Directory of Open Access Journals (Sweden)

J. A. Wild

2004-11-01

Full Text Available As a measure of the degree of coupling between the solar wind-magnetosphere-ionosphere systems, the rate at which the size of the polar cap (the region corresponding to ionospheric termini of open magnetic flux tubes varies is of prime importance. However, a reliable technique by which the extent of the polar cap might be routinely monitored has yet to be developed. Current techniques provide particularly ambiguous indications of the polar cap boundary in the dawn sector. We present a case study of space- and ground-based observations of the dawn-sector auroral zone and attempt to determine the location of the polar cap boundary using multi-wavelength observations of the ultraviolet aurora (made by the IMAGE FUV imager, precipitating particle measurements (recorded by the FAST, DMSP, and Cluster 1 and 3 satellites, and SuperDARN HF radar observations of the ionospheric Doppler spectral width boundary. We conclude that in the dawn sector, during the interval presented, neither the poleward edge of the wideband auroral UV emission (140-180nm nor the Doppler spectral width boundary were trustworthy indicators of the polar cap boundary location, while narrow band UV emissions in the range 130-140nm appear to be much more reliable.

First demonstration of HF-driven ionospheric currents

Science.gov (United States)

Papadopoulos, K.; Chang, C.-L.; Labenski, J.; Wallace, T.

2011-10-01

The first experimental demonstration of HF driven currents in the ionosphere at low ELF/ULF frequencies without relying in the presence of electrojets is presented. The effect was predicted by theoretical/computational means in a recent letter and given the name Ionospheric Current Drive (ICD). The effect relies on modulated F-region HF heating to generate Magneto-Sonic (MS) waves that drive Hall currents when they reach the E-region. The Hall currents inject ELF waves into the Earth-Ionosphere waveguide and helicon and Shear Alfven (SA) waves in the magnetosphere. The proof-of-concept experiments were conducted using the HAARP heater in Alaska under the BRIOCHE program. Waves between 0.1-70 Hz were measured at both near and far sites. The letter discusses the differences between ICD generated waves and those relying on modulation of electrojets.

Characteristics of the magnetohydrodynamic waves observed in the earth's magnetosphere and on the ground

International Nuclear Information System (INIS)

Kuwashima, M.; Fujita, S.

1989-01-01

Current research topics on MHD waves in the earth's magnetosphere and on the ground are summarized. Upstream waves in the earth's foreshock region and their transmission into and propagation through the magnetosphere are discussed in the context of relationships of Pc3 magnetic pulsations on the ground. The characteristics of ssc-associated magnetic pulsations are considered, and instabilities with the hot plasma in the ring current in the magnetosphere are addressed in the context of the relationships of compressional Pc 4-5 waves. The characteristics of Pi2 magnetic pulsations are examined, and the role of the ionosphere on the modifications of MHD waves is addressed

Recent Advances in Atmospheric, Solar-Terrestrial Physics and Space Weather From a North-South network of scientists [2006-2016] PART A: TUTORIAL

Science.gov (United States)

Amory-Mazaudier, C.; Menvielle, M.; Curto, J-J.; Le Huy, M.

2017-12-01

This paper reviews scientific advances achieved by a North-South network between 2006 and 2016. These scientific advances concern Solar Terrestrial Physics, Atmospheric Physics and Space Weather. In this part A, we introduce knowledge on the Sun-Earth system. We consider the physical process of the dynamo which is present in the Sun, in the core of the Earth and also in the regions between the Sun and the Earth, the solar wind-magnetosphere and the ionosphere. Equations of plasma physics and Maxwell's equations will be recalled. In the Sun-Earth system there are permanent dynamos (Sun, Earth's core, solar wind - magnetosphere, neutral wind - ionosphere) and non-permanent dynamos that are activated during magnetic storms in the magnetosphere and in the ionosphere. All these dynamos have associated electric currents that affect the variations of the Earth's magnetic field which are easily measurable. That is why a part of the tutorial is also devoted to the magnetic indices which are indicators of the electric currents in the Sun-Earth system. In order to understand some results of the part B, we present some characteristics of the Equatorial region and of the electrodynamics coupling the Auroral and Equatorial regions.

Atmosphere-Ionosphere Electrodynamic Coupling

Science.gov (United States)

Sorokin, V. M.; Chmyrev, V. M.

Numerous phenomena that occur in the mesosphere, ionosphere, and the magnetosphere of the Earth are caused by the sources located in the lower atmosphere and on the ground. We describe the effects produced by lightning activity and by ground-based transmitters operated in high frequency (HF) and very low frequency (VLF) ranges. Among these phenomena are the ionosphere heating and the formation of plasma density inhomogeneities, the excitation of gamma ray bursts and atmospheric emissions in different spectral bands, the generation of ULF/ELF/VLF electromagnetic waves and plasma turbulence in the ionosphere, the stimulation of radiation belt electron precipitations and the acceleration of ions in the upper ionosphere. The most interesting results of experimental and theoretical studies of these phenomena are discussed below. The ionosphere is subject to the action of the conductive electric current flowing in the atmosphere-ionosphere circuit. We present a physical model of DC electric field and current formation in this circuit. The key element of this model is an external current, which is formed with the occurrence of convective upward transport of charged aerosols and their gravitational sedimentation in the atmosphere. An increase in the level of atmospheric radioactivity results in the appearance of additional ionization and change of electrical conductivity. Variation of conductivity and external current in the lower atmosphere leads to perturbation of the electric current flowing in the global atmosphere-ionosphere circuit and to the associated DC electric field perturbation both on the Earth's surface and in the ionosphere. Description of these processes and some results of the electric field and current calculations are presented below. The seismic-induced electric field perturbations produce noticeable effects in the ionosphere by generating the electromagnetic field and plasma disturbances. We describe the generation mechanisms of such experimentally

On the utilization of ionosonde data to analyze the latitudinal penetration of ionospheric storm effects

International Nuclear Information System (INIS)

Forbes, J.M.; Codrescu, M.; Hall, T.J.

1988-01-01

Upper atmosphere science is placing increased emphasis on global coupling between the magnetosphere, ionosphere, and thermosphere systems, particularly with regard to the penetration of dynamic, chemical, and electrodynamic effects from high to low latitudes during magnetically disturbed periods. An emerging potential exists for latitudinal and longitudinal chains of ionosondes to contribute uniquely to this thrust in ways complementary to the capabilities and shortcomings of other groundbased sensors and satellites. Here we illustrate a methodology whereby the fullest potential of such ionosonde data can be realized. Data from a chain of stations close to the -165 0 magnetic meridian and separated by about 5 0 in magnetic latitude are used to study the relationships between magnetic activity, hmF2, foF2, and inferred meridional winds during 17--28 April, 1979. Hourly values are fit in latitude using Legendre polynomials, and variations from quiet-time values are displayed in latitude-U.T. coordinates using a color graphics method which provides an illuminating illustration of the penetration of ionospheric disturbances in latitude and their dependence on Kp, storm time, and local time. Observed effects are interpreted in terms of plausible electric field, neutral wind, and neutral composition changes during the storm period. For instance, net depletions in foF2 occur over the entire disturbed interval down to about 25 0 --30 0 latitude, apparently due to such increased N 2 densities that the resulting enhanced plasma loss rates overcompensate and ''positive'' storm effects whereby southward winds elevate the F-layer peak to altitudes of reduced chemical loss

Magnetospherically reflected chorus waves revealed by ray tracing with CLUSTER data

Czech Academy of Sciences Publication Activity Database

Parrot, M.; Santolík, Ondřej; Cornilleau-Wehrlin, N.; Maksimovic, M.; Harvey, C. C.

2003-01-01

Roč. 21, - (2003), s. 1111-1120 ISSN 0992-7689 R&D Projects: GA ČR GA202/03/0832; GA MŠk ME 650 Institutional research plan: CEZ:AV0Z3042911 Keywords : magnetospheric physics * ionosphere * radio science Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.031, year: 2003

Penetration of magnetosonic waves into the magnetosphere: influence of a transition layer

Directory of Open Access Journals (Sweden)

A. S. Leonovich

Full Text Available We have constructed a theory for the penetration of magnetosonic waves from the solar wind into the magnetosphere through a transition layer in a plane-stratified model for the medium. In this model the boundary layer is treated as a region, inside of which the parameters of the medium vary from values characteristic for the magnetosphere, to values typical of the solar wind. It is shown that if such a layer has sufficiently sharp boundaries, then magnetosonic eigen-oscillations can be excited inside of it. The boundaries of such a layer are partially permeable for magnetosonic waves. Therefore, if the eigen-oscillations are not sustained by an external source, they will be attenuated, because some of the energy is carried away by the oscillations that penetrate the solar wind and the magnetosphere. It is shown that about 40% of the energy flux of the waves incident on the transition layer in the magnetotail region penetrate to the magnetosphere’s interior. This energy flux suffices to sustain the stationary convection of magnetospheric plasma. The total energy input to the magnetosphere during a time interval of the order of the substorm growth phase time is comparable with the energetics of an average substorm.

Key words. Magnetospheric physics (MHD waves and instabilities; solar wind–magnetosphere interactions – Space plasma physics (kinetic and MHD theory

Penetration of magnetosonic waves into the magnetosphere: influence of a transition layer

Directory of Open Access Journals (Sweden)

A. S. Leonovich

2003-05-01

Full Text Available We have constructed a theory for the penetration of magnetosonic waves from the solar wind into the magnetosphere through a transition layer in a plane-stratified model for the medium. In this model the boundary layer is treated as a region, inside of which the parameters of the medium vary from values characteristic for the magnetosphere, to values typical of the solar wind. It is shown that if such a layer has sufficiently sharp boundaries, then magnetosonic eigen-oscillations can be excited inside of it. The boundaries of such a layer are partially permeable for magnetosonic waves. Therefore, if the eigen-oscillations are not sustained by an external source, they will be attenuated, because some of the energy is carried away by the oscillations that penetrate the solar wind and the magnetosphere. It is shown that about 40% of the energy flux of the waves incident on the transition layer in the magnetotail region penetrate to the magnetosphere’s interior. This energy flux suffices to sustain the stationary convection of magnetospheric plasma. The total energy input to the magnetosphere during a time interval of the order of the substorm growth phase time is comparable with the energetics of an average substorm.Key words. Magnetospheric physics (MHD waves and instabilities; solar wind–magnetosphere interactions – Space plasma physics (kinetic and MHD theory

Structure of the subauroral ionosphere during the magnetospheric storm according to the data of the ''Interkosmos-19'' satellite

International Nuclear Information System (INIS)

Deminov, M.G.; Karpachev, A.T.; Kushnerevskij, Yu.V.; Shmilauehr, Ya.

1985-01-01

Variations of electron density and electron temperature in the subauroral ionosphere during the magnetospheric storm on April 3-4, 1979 are analyzed according to the data of the ''Interkosmos-19'' satellite. The sharpest displacement of a middle latitude fall-through to the equator is primarily caused by the turn-over of Bsub(z)-component of the interplanetary magnetic field (IMF) to the South. This displacement has taken place immediately after the turn-over of IMF Bsub(z)-component to the South in the day-time with a approximately 2 h delay in the night-time. and a approximately 40 min delay in around midnight. The general amplitude of fall-trhrough displacement is approximately 18. 20 and 17 deg for the day- and night-time and around midnight. The minimum latitude of the fall-through equals 56, 48 and 43 deg in the day- and night-time and midnight respectively. The saturation in IMF equatorial displacement is observed in the dark time of the day near the maximum of IMF Bsub(z)-component and Ksub(p) index

Seasonal effects in the ionosphere-thermosphere response to the precipitation and field-aligned current variations in the cusp region

Directory of Open Access Journals (Sweden)

A. A. Namgaladze

Full Text Available The seasonal effects in the thermosphere and ionosphere responses to the precipitating electron flux and field-aligned current variations, of the order of an hour in duration, in the summer and winter cusp regions have been investigated using the global numerical model of the Earth's upper atmosphere. Two variants of the calculations have been performed both for the IMF B_y < 0. In the first variant, the model input data for the summer and winter precipitating fluxes and field-aligned currents have been taken as geomagnetically symmetric and equal to those used earlier in the calculations for the equinoctial conditions. It has been found that both ionospheric and thermospheric disturbances are more intensive in the winter cusp region due to the lower conductivity of the winter polar cap ionosphere and correspondingly larger electric field variations leading to the larger Joule heating effects in the ion and neutral gas temperature, ion drag effects in the thermospheric winds and ion drift effects in the F2-region electron concentration. In the second variant, the calculations have been performed for the events of 28–29 January, 1992 when precipitations were weaker but the magnetospheric convection was stronger than in the first variant. Geomagnetically asymmetric input data for the summer and winter precipitating fluxes and field-aligned currents have been taken from the patterns derived by combining data obtained from the satellite, radar and ground magnetometer observations for these events. Calculated patterns of the ionospheric convection and thermospheric circulation have been compared with observations and it has been established that calculated patterns of the ionospheric convection for both winter and summer hemispheres are in a good agreement with the observations. Calculated patterns of the thermospheric circulation are in a good agreement with the average circulation for the Southern (summer Hemisphere obtained

Response of Earth and Venus ionospheres to corotating solar wind stream of 3 July 1979

International Nuclear Information System (INIS)

Taylor, H.A. Jr.

1985-01-01

Corotating solar wind streams emanating from stable coronal structures provide an unique opportunity to compare the response of planetary ionospheres to the energy conveyed in the streams. For recurrent solar conditions the 'signal' propagating outward along spiral paths in interplanetary space can at times exhibit rather similar content at quite different downstream locations in the ecliptic plane. Using solar wind measurements from plasma detectors on ISEE-3, Pioneer Venus Orbiter (PVO) and Helios-A, as well as in-situ ion composition measurements from Bennett Ion Mass Spectrometers on the Atmosphere Explorer-E and PVO spacecraft, corotating stream interactions are examined at Earth and Venus. (Auth.)

Understanding Transient Forcing with Plasma Instability Model, Ionospheric Propagation Model and GNSS Observations

Science.gov (United States)

Deshpande, K.; Zettergren, M. D.; Datta-Barua, S.

2017-12-01

Fluctuations in the Global Navigation Satellite Systems (GNSS) signals observed as amplitude and phase scintillations are produced by plasma density structures in the ionosphere. Phase scintillation events in particular occur due to structures at Fresnel scales, typically about 250 meters at ionospheric heights and GNSS frequency. Likely processes contributing to small-scale density structuring in auroral and polar regions include ionospheric gradient-drift instability (GDI) and Kelvin-Helmholtz instability (KHI), which result, generally, from magnetosphere-ionosphere interactions (e.g. reconnection) associated with cusp and auroral zone regions. Scintillation signals, ostensibly from either GDI or KHI, are frequently observed in the high latitude ionosphere and are potentially useful diagnostics of how energy from the transient forcing in the cusp or polar cap region cascades, via instabilities, to small scales. However, extracting quantitative details of instabilities leading to scintillation using GNSS data drastically benefits from both a model of the irregularities and a model of GNSS signal propagation through irregular media. This work uses a physics-based model of the generation of plasma density irregularities (GEMINI - Geospace Environment Model of Ion-Neutral Interactions) coupled to an ionospheric radio wave propagation model (SIGMA - Satellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere) to explore the cascade of density structures from medium to small (sub-kilometer) scales. Specifically, GEMINI-SIGMA is used to simulate expected scintillation from different instabilities during various stages of evolution to determine features of the scintillation that may be useful to studying ionospheric density structures. Furthermore we relate the instabilities producing GNSS scintillations to the transient space and time-dependent magnetospheric phenomena and further predict characteristics of scintillation in different geophysical

Low-Latitude Ionosphere and Thermosphere: Decadal Observations From the CHAMP Mission

DEFF Research Database (Denmark)

Stolle, Claudia; Liu, Huixin

2014-01-01

Self-consistent physical models of an auroral flux tube are capable of calculating optical emissions and ionospheric state variables for a given set of magnetospheric drivers. The collocation of incoherent scatter radar (ISR) and photometric measurements provides a powerful framework for testing ...

Nonlinear dynamical modeling and prediction of the terrestrial magnetospheric activity

International Nuclear Information System (INIS)

Vassiliadis, D.

1992-01-01

The irregular activity of the magnetosphere results from its complex internal dynamics as well as the external influence of the solar wind. The dominating self-organization of the magnetospheric plasma gives rise to repetitive, large-scale coherent behavior manifested in phenomena such as the magnetic substorm. Based on the nonlinearity of the global dynamics this dissertation examines the magnetosphere as a nonlinear dynamical system using time series analysis techniques. Initially the magnetospheric activity is modeled in terms of an autonomous system. A dimension study shows that its observed time series is self-similar, but the correlation dimension is high. The implication of a large number of degrees of freedom is confirmed by other state space techniques such as Poincare sections and search for unstable periodic orbits. At the same time a stability study of the time series in terms of Lyapunov exponents suggests that the series is not chaotic. The absence of deterministic chaos is supported by the low predictive capability of the autonomous model. Rather than chaos, it is an external input which is largely responsible for the irregularity of the magnetospheric activity. In fact, the external driving is so strong that the above state space techniques give results for magnetospheric and solar wind time series that are at least qualitatively similar. Therefore the solar wind input has to be included in a low-dimensional nonautonomous model. Indeed it is shown that such a model can reproduce the observed magnetospheric behavior up to 80-90 percent. The characteristic coefficients of the model show little variation depending on the external disturbance. The impulse response is consistent with earlier results of linear prediction filters. The model can be easily extended to contain nonlinear features of the magnetospheric activity and in particular the loading-unloading behavior of substorms

Ion Composition and Energization in the Earth's Inner Magnetosphere and the Effects on Ring Current Buildup

Science.gov (United States)

Keika, K.; Kistler, L. M.; Brandt, P. C.

2014-12-01

In-situ observations and modeling work have confirmed that singly-charged oxygen ions, O+, which are of Earth's ionospheric origin, are heated/accelerated up to >100 keV in the magnetosphere. The energetic O+ population makes a significant contribution to the plasma pressure in the Earth's inner magnetosphere during magnetic storms, although under quiet conditions H+ dominates the plasma pressure. The pressure enhancements, which we term energization, are caused by adiabatic heating through earthward transport of source population in the plasma sheet, local acceleration in the inner magnetosphere and near-Earth plasma sheet, and enhanced ion supply from the topside ionosphere. The key issues regarding stronger O+ energization than H+ are non-adiabatic local acceleration, responsible for increase in O+ temperature, and more significant O+ supply than H+, responsible for increase in O+ density. Although several acceleration mechanisms and O+ supply processes have been proposed, it remains an open question what mechanism(s)/process(es) play the dominant role in stronger O+ energization. In this paper we summarize important spacecraft observations including those from Van Allen Probes, introduces the proposed mechanisms/processes that generate O+-rich energetic plasma population, and outlines possible scenarios of O+ pressure abundance in the Earth's inner magnetosphere.

The ionospheric signature of transient dayside reconnection and the associated pulsed convection return flow

Directory of Open Access Journals (Sweden)

S. E. Milan

Full Text Available Three SuperDARN coherent HF radars are employed to investigate the excitation of convection in the dayside high-latitude ionosphere in response to transient reconnection occurring in the cusp region. This study demonstrates the existence of transient antisunward-propagating backscatter features at the expected location of the ionospheric footprint of the cusp region, which have a repetition rate near 10 min. These are interpreted as the ionospheric signature of flux transfer events. Moreover, transient sunward-propagating regions of backscatter are observed in the convection return flow regions of both the pre- and post-noon sectors. These patches are observed to propagate towards the noon sector from at least as far around the auroral zone as 07 MLT in the pre-noon sector and 17 MLT in the post-noon sector, travelling with a velocity of approximately 1.5 to 2 km s^-1. These return flow patches have a repetition rate similar to that of the transient features observed at local noon. While providing supporting evidence for the impulsive nature of convection flow, the observation of sunward-propagating features in the return flow region is not consistent with current conceptual models of the excitation of convection.

Key words. Ionosphere (plasma convection · Magnetospheric physics (magnetopause · cusp · and boundary layers; magnetosphere-ionosphere interactions

Electrodynamics of the Martian Ionosphere

Science.gov (United States)

Ledvina, S. A.; Brecht, S. H.

2017-12-01

The presence of the Martian crustal magnetic fields makes a significant modification to the interaction between the solar wind/IMF and the ionosphere of the planet. This paper presents the results of 3-D hybrid simulations of Martian solar wind interaction containing the Martian crustal fields., self-consistent ionospheric chemistry and planetary rotation. It has already been reported that the addition of the crustal fields and planetary rotation makes a significant modification of the ionospheric loss from Mars, Brecht et al., 2016. This paper focuses on two other aspects of the interaction, the electric fields and the current systems created by the solar wind interaction. The results of several simulations will be analyzed and compared. The electric fields around Mars due to its interaction with the solar wind will be examined. Special attention will be paid to the electric field constituents (∇ X B, ∇Pe, ηJ). Regions where the electric field is parallel to the magnetic field will be found and the implications of these regions will be discussed. Current systems for each ion species will be shown. Finally the effects on the electric fields and the current systems due to the rotation of Mars will be examined.

The interaction of impulsive solar wind discontinuities with the magnetosphere: a multi-satellite case study

Energy Technology Data Exchange (ETDEWEB)

Labelle, J. (Dartmouth Coll., Hanover, NH (USA). Dept. of Physics and Astronomy); Kistler, L.M.; Treumann, R.A.; Baumjohann, W. (Max-Planck-Institut fuer Physik und Astrophysik, Garching (Germany, F.R.). Inst. fuer Extraterrestrische Physik); Sibeck, D.G. (Johns Hopkins Univ., Baltimore, MD (USA). Dept. of Physics); Baker, D.N. (National Aeronautics and Space Administration, Greenbelt, MD (USA). Goddard Space Flight Center); Belian, R.D. (Los Alamos National Lab., NM (USA))

1990-07-01

During the magnetic storm of 4-5 September 1984, the outbound AMPTE/IRM spacecraft stayed just outside the expanding Earth's bow shock for a period of 7.5 h. During this interval the solar wind ram pressure and the interplanetary magnetic field remained approximately constant, except for two distinct impulsive pressure pulses lasting a few minutes each. These pulses coincided with discontinuities in which the IMF changed direction by about 90deg, and the solar wind kinetic pressure decreased slightly. Accompanying these discontinuities, the following magnetospheric signatures were observed: (1) immediately after each discontinuity, the growth phase of a substorm commenced as evidenced by decreases in the flux of energetic ions at geosynchronous orbit on both the dayside and nightside, and these were followed by particle injection events on the nightside 20-35 min after the discontinuities; (2) equatorial magnetograms recorded sudden impulses in the magnetic field; and (3) after a delay of 8-12 min, the IRM detected outward motion of the bow shock, and in each case about an hour passed before the outward-moving satellite caught up again with the shock. Overall, the magnetospheric and ground signatures of the first discontinuity were larger than those of the second. It is speculated that the IMF direction and other factors such as the local time and latitude of the ground stations may be important factors in determining the magnitude of these signatures. (author).

The interaction of impulsive solar wind discontinuities with the magnetosphere: a multi-satellite case study

International Nuclear Information System (INIS)

Labelle, J.

1990-01-01

During the magnetic storm of 4-5 September 1984, the outbound AMPTE/IRM spacecraft stayed just outside the expanding Earth's bow shock for a period of 7.5 h. During this interval the solar wind ram pressure and the interplanetary magnetic field remained approximately constant, except for two distinct impulsive pressure pulses lasting a few minutes each. These pulses coincided with discontinuities in which the IMF changed direction by about 90deg, and the solar wind kinetic pressure decreased slightly. Accompanying these discontinuities, the following magnetospheric signatures were observed: (1) immediately after each discontinuity, the growth phase of a substorm commenced as evidenced by decreases in the flux of energetic ions at geosynchronous orbit on both the dayside and nightside, and these were followed by particle injection events on the nightside 20-35 min after the discontinuities; (2) equatorial magnetograms recorded sudden impulses in the magnetic field; and (3) after a delay of 8-12 min, the IRM detected outward motion of the bow shock, and in each case about an hour passed before the outward-moving satellite caught up again with the shock. Overall, the magnetospheric and ground signatures of the first discontinuity were larger than those of the second. It is speculated that the IMF direction and other factors such as the local time and latitude of the ground stations may be important factors in determining the magnitude of these signatures. (author)

The CuSPED Mission: CubeSat for GNSS Sounding of the Ionosphere-Plasmasphere Electron Density

Science.gov (United States)

Gross, Jason N.; Keesee, Amy M.; Christian, John A.; Gu, Yu; Scime, Earl; Komjathy, Attila; Lightsey, E. Glenn; Pollock, Craig J.

2016-01-01

The CubeSat for GNSS Sounding of Ionosphere-Plasmasphere Electron Density (CuSPED) is a 3U CubeSat mission concept that has been developed in response to the NASA Heliophysics program's decadal science goal of the determining of the dynamics and coupling of the Earth's magnetosphere, ionosphere, and atmosphere and their response to solar and terrestrial inputs. The mission was formulated through a collaboration between West Virginia University, Georgia Tech, NASA GSFC and NASA JPL, and features a 3U CubeSat that hosts both a miniaturized space capable Global Navigation Satellite System (GNSS) receiver for topside atmospheric sounding, along with a Thermal Electron Capped Hemispherical Spectrometer (TECHS) for the purpose of in situ electron precipitation measurements. These two complimentary measurement techniques will provide data for the purpose of constraining ionosphere-magnetosphere coupling models and will also enable studies of the local plasma environment and spacecraft charging; a phenomenon which is known to lead to significant errors in the measurement of low-energy, charged species from instruments aboard spacecraft traversing the ionosphere. This paper will provide an overview of the concept including its science motivation and implementation.

On the relation between ionospheric winter anomalies and solar wind

International Nuclear Information System (INIS)

Rumi, G.C.

2001-01-01

There are two different winter anomalies. A small one that appears in connection with ionization at relatively low latitudes in the bottom of the D-region of the ionosphere. There, the electron densities in the winter happen to be less than should be expected. On the other hand, the classic winter anomaly is present when in the winter the upper D-region, again at relatively low latitudes, has more ionization than should be expected. Both these effects are due to the slant compression of the geomagnetic field produced by the solar wind in the wind in the winter season (which is, of course, the summer season when reference is made to events in the other hemisphere). It is shown that the small winter anomaly is a consequence of a hemispheric imbalance in the flux of galactic cosmic rays determined by the obliquely distorted geomagnetic field. It is shown that the standard winter anomaly can be ascribed to the influx of a super solar wind, which penetrates into the Earth's polar atmosphere down to E-region, heights and, duly concentrated through a funneling action at the winter pole of the distorted geomagnetic field, slows down the winter polar vortex. An equatorward motion of the polar air with its content of nitric oxide brings about the excess of ionization in the upper D-region at lower latitudes. The experimentally observed rhythmic recurrence of the upper winter anomaly is correlated to a possible rhythmic recurrence of the super solar wind. The actual detection of the upper winter anomaly could yield some information on the velocity of the basic solar wind. A by-product of the present analysis, the determination of Γ, the coefficient of collisional detachment of the electrons from the O 2 - ions, is presented in the Appendix

On the relation between ionospheric winter anomalies and solar wind

Energy Technology Data Exchange (ETDEWEB)

Rumi, G.C. [Lecco, (Italy)

2001-06-01

There are two different winter anomalies. A small one that appears in connection with ionization at relatively low latitudes in the bottom of the D-region of the ionosphere. There, the electron densities in the winter happen to be less than should be expected. On the other hand, the classic winter anomaly is present when in the winter the upper D-region, again at relatively low latitudes, has more ionization than should be expected. Both these effects are due to the slant compression of the geomagnetic field produced by the solar wind in the wind in the winter season (which is, of course, the summer season when reference is made to events in the other hemisphere). It is shown that the small winter anomaly is a consequence of a hemispheric imbalance in the flux of galactic cosmic rays determined by the obliquely distorted geomagnetic field. It is shown that the standard winter anomaly can be ascribed to the influx of a super solar wind, which penetrates into the Earth's polar atmosphere down to E-region, heights and, duly concentrated through a funneling action at the winter pole of the distorted geomagnetic field, slows down the winter polar vortex. An equatorward motion of the polar air with its content of nitric oxide brings about the excess of ionization in the upper D-region at lower latitudes. The experimentally observed rhythmic recurrence of the upper winter anomaly is correlated to a possible rhythmic recurrence of the super solar wind. The actual detection of the upper winter anomaly could yield some information on the velocity of the basic solar wind. A by-product of the present analysis, the determination of {gamma}, the coefficient of collisional detachment of the electrons from the O{sub 2} {sup -} ions, is presented in the Appendix.

A 3D Multi-fluid MHD Study of the Interaction of the Solar Wind with the Ionosphere/Atmosphere System of Venus.

Science.gov (United States)

Najib, D.; Nagy, A.; Toth, G.; Ma, Y.-J.

2011-10-01

We use the latest version of our four species multifluid model to study the interaction of the solar wind with Venus. The model solves simultaneously the continuity, momentum and energy equations of the different ions. The lower boundary of our model is at 100 km, below the main ionospheric peak, and the radial resolution is about 10 km in the ionosphere, thus the model does a very good job in reproducing the ionosphere and the associated processes. We carry out calculations for high and low solar activity conditions and establish the importance of mass loading by the extended exosphere of Venus. We demonstrate the importance of using the multi-fluid rather than a single fluid model. We also calculate the atmospheric escape of the ionospheric species and compare our model results with the observed parameters from Pioneer Venus and Venus Express.

The spatial distribution of magnetospheric convection electric fields at ionospheric altitudes: a review. 1. Observations

International Nuclear Information System (INIS)

Caudal, G.; Blanc, M.

1983-01-01

The different techniques used for the study of the large-scale pattern of magnetospheric convection in the auroral zone are reviewed, with particular emphasis on incoherent and coherent scatter radars. For each technique, typical results are presented that illustrate its most important contributions to our knowledge of plasma convection at ionospheric altitudes, and its main advantages, limitations, and typical spatial and temporal coverage are described. Based upon the results gathered to date, the main features of the convection pattern are presented, namely: the double cell system and its asymmetry depending in particular on the Bsub(y) component of the IMF, the Harang discontinuity and its latitudinal dependence, the dayside throat, the attenuation of convection toward lower latitudes and its reversal at the polar cap boundary. The most interesting problems still open include the establishment of a quantitative model of the latitudinal variation of the electric field intensity at the planetary scale. Others entail separating universal time and local time effects in the field variations. Longitude variations have not yet been evaluated, and the characteristic signature of substorms has not been clearly separated from mere global modulations of the intensity of convection. Global coordinated campaigns, taking advantage of the best that each measurement technique has to offer to achieve the spatial and temporal coverage needed, are the only possible way to attack these problems

Electromagnetic ion cyclotron waves stimulated by modest magnetospheric compressions

Science.gov (United States)

Anderson, B. J.; Hamilton, D. C.

1993-01-01

AMPTE/CCE magnetic field and particle data are used to test the suggestion that increased hot proton temperature anisotropy resulting from convection during magnetospheric compression is responsible for the enhancement in Pc 1 emission via generation of electromagnetic ion cyclotron (EMIC) waves in the dayside outer equatorial magnetosphere. The relative increase in magnetic field is used to gauge the strength of the compression, and an image dipole model is used to estimate the motion of the plasma during compression. Proton data are used to analyze the evolution of the proton distribution and the corresponding changes in EMIC wave activity expected during the compression. It is suggested that enhancements in dynamic pressure pump the energetic proton distributions in the outer magnetosphere, driving EMIC waves. Waves are expected to be generated most readily close to the magnetopause, and transient pressure pulses may be associated with bursts of EMIC waves, which would be observed on the ground in association with ionospheric transient signatures.

A New Approach to Modeling Jupiter's Magnetosphere

Science.gov (United States)

Fukazawa, K.; Katoh, Y.; Walker, R. J.; Kimura, T.; Tsuchiya, F.; Murakami, G.; Kita, H.; Tao, C.; Murata, K. T.

2017-12-01

The scales in planetary magnetospheres range from 10s of planetary radii to kilometers. For a number of years we have studied the magnetospheres of Jupiter and Saturn by using 3-dimensional magnetohydrodynamic (MHD) simulations. However, we have not been able to reach even the limits of the MHD approximation because of the large amount of computer resources required. Recently thanks to the progress in supercomputer systems, we have obtained the capability to simulate Jupiter's magnetosphere with 1000 times the number of grid points used in our previous simulations. This has allowed us to combine the high resolution global simulation with a micro-scale simulation of the Jovian magnetosphere. In particular we can combine a hybrid (kinetic ions and fluid electrons) simulation with the MHD simulation. In addition, the new capability enables us to run multi-parameter survey simulations of the Jupiter-solar wind system. In this study we performed a high-resolution simulation of Jovian magnetosphere to connect with the hybrid simulation, and lower resolution simulations under the various solar wind conditions to compare with Hisaki and Juno observations. In the high-resolution simulation we used a regular Cartesian gird with 0.15 RJ grid spacing and placed the inner boundary at 7 RJ. From these simulation settings, we provide the magnetic field out to around 20 RJ from Jupiter as a background field for the hybrid simulation. For the first time we have been able to resolve Kelvin Helmholtz waves on the magnetopause. We have investigated solar wind dynamic pressures between 0.01 and 0.09 nPa for a number of IMF values. These simulation data are open for the registered users to download the raw data. We have compared the results of these simulations with Hisaki auroral observations.

The Rocket Investigation of Current Closure in the Ionosphere (RICCI) mission: A novel application of CubeSats from a sounding rocket platform

Science.gov (United States)

Cohen, I. J.; Anderson, B. J.; Lessard, M.; Bonnell, J. W.; Bounds, S. R.; Lysak, R. L.; Erlandson, R. E.

2017-12-01

The transfer of energy and momentum between the terrestrial magnetosphere and ionosphere is substantially mediated by large-scale field-aligned currents (FACs), driven by magnetopause dynamics and magnetospheric pressures and closing through the ionosphere where the dissipation and drag are governed. While significant insight into ionospheric electrodynamics and the nature of magnetosphere-ionosphere (M-I) coupling have been gained by rocket and satellite measurements, in situ measurement of these ionospheric closure currents remains challenging. To date the best estimates of ionospheric current densities are inferred from ground-based radar observations combining electric fields calculated from drifts with conductivities derived from densities. RICCI aims to observe the structure of the ionospheric currents in situ to determine how the altitude structure of these currents is related to precipitation and density cavities, electromagnetic dynamics, and governs energy dissipation in the ionosphere. In situ measurement of the current density using multi-point measurements of the magnetic field requires precise attitude knowledge for which the only demonstrated technique is the use of star camera systems. The low vehicle rotation rates required for miniature commercial off-the-shelf (COTS) star cameras prohibit the use of available rocket sub-payload technologies at Wallops Flight Facility (WFF) which use high rates of spin to stabilize attitude. However, CubeSat attitude systems are already designed to achieve low vehicle rotation rates, so RICCI will use a set of three CubeSat sub-payloads deployed from a main low altitude payload with apogee of 160 km to provide precise current density measurement through the ionospheric closure altitude regime, together with a second rocket with apogee near 320 km to measure the incident input energy flux and convection electric field. The two rocket payloads and CubeSate sub-payloads are all instrumented with star cameras and

On the equivalence of the solar wind coupling parameter ε and the magnetospheric energy output parameter UT during intense geomagnetic storms

International Nuclear Information System (INIS)

Gonzalez, W.D.; Gonzalez, A.L.C.; Tsurutani, B.T.

1990-01-01

For intervals with intense geomagnetic activity it is shown that the solar wind coupling parameter ε and the magnetospheric output parameter U T are equivalent and that ranges of values of ε can be set up in terms of values of the ring current-time constant τ. (author)

A Statistical study of the Doppler spectral width of high-latitude ionospheric F-region echoes recorded with SuperDARN coherent HF radars

Directory of Open Access Journals (Sweden)

J.-P. Villain

2002-11-01

Full Text Available The HF radars of the Super Dual Auroral Radar Network (SuperDARN provide measurements of the E × B drift of ionospheric plasma over extended regions of the high-latitude ionosphere. We have conducted a statistical study of the associated Doppler spectral width of ionospheric F-region echoes. The study has been conducted with all available radars from the Northern Hemisphere for 2 specific periods of time. Period 1 corresponds to the winter months of 1994, while period 2 covers October 1996 to March 1997. The distributions of data points and average spectral width are presented as a function of Magnetic Latitude and Magnetic Local Time. The databases are very consistent and exhibit the same features. The most stringent features are: a region of very high spectral width, collocated with the ionospheric LLBL/cusp/mantle region; an oval shaped region of high spectral width, whose equator-ward boundary matches the poleward limit of the Holzworth and Meng auroral oval. A simulation has been conducted to evaluate the geometrical and instrumental effects on the spectral width. It shows that these effects cannot account for the observed spectral features. It is then concluded that these specific spectral width characteristics are the signature of ionospheric/magnetospheric coupling phenomena.Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions; ionospheric irregularities

A Statistical study of the Doppler spectral width of high-latitude ionospheric F-region echoes recorded with SuperDARN coherent HF radars

Directory of Open Access Journals (Sweden)

J.-P. Villain

Full Text Available The HF radars of the Super Dual Auroral Radar Network (SuperDARN provide measurements of the E × B drift of ionospheric plasma over extended regions of the high-latitude ionosphere. We have conducted a statistical study of the associated Doppler spectral width of ionospheric F-region echoes. The study has been conducted with all available radars from the Northern Hemisphere for 2 specific periods of time. Period 1 corresponds to the winter months of 1994, while period 2 covers October 1996 to March 1997. The distributions of data points and average spectral width are presented as a function of Magnetic Latitude and Magnetic Local Time. The databases are very consistent and exhibit the same features. The most stringent features are: a region of very high spectral width, collocated with the ionospheric LLBL/cusp/mantle region; an oval shaped region of high spectral width, whose equator-ward boundary matches the poleward limit of the Holzworth and Meng auroral oval. A simulation has been conducted to evaluate the geometrical and instrumental effects on the spectral width. It shows that these effects cannot account for the observed spectral features. It is then concluded that these specific spectral width characteristics are the signature of ionospheric/magnetospheric coupling phenomena.

Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions; ionospheric irregularities

Photoelectron reflection and scattering at Venus: an upper limit on the "polar wind" ambipolar electric field, and a new source of top-side ionospheric heating

Science.gov (United States)

Collinson, Glyn; Glocer, Alex; Grebowsky, Joe; Peterson, William; Frahm, Rudy; Moore, Thomas; Gilbert, Lin; Coates, Andrew

2015-04-01

An important mechanism in the generation of Earth's polar wind is the ambipolar potential generated by the outflow along open field lines of superthermal electrons. This ≈20V electric potential assists ions in overcoming the gravitational potential, and is a key mechanism for Terrestrial ionospheric escape. At Venus, except in rare circumstances, every field line is open, and a similar outflow of ionospheric electrons is observed. It is thus hypothesized that a similar electric potential may be present at Venus, contributing to global ionospheric loss. However, a very sensitive electric field instrument would be required to directly measure this potential, and no such instrument has yet been flown to Venus. In this pilot study, we examine photoelectron spectra measured by the ASPERA-ELS instrument on the Venus Express to put an initial upper bound on the total potential drop above 350km of Φ current understanding, a "polar wind" like ambipolar electric field may not be as important a mechanism for atmospheric escape as previously suspected. Additionally, we find our spectra are consistent with the scattering of photoelectrons, the heating from which which we hypothesize may act as a source of top-side ionospheric heating, and may play a role in influencing the scale height of the ionosphere.

Magnetospheric Control of Density and Composition in the Polar Ionosphere

Science.gov (United States)

2015-06-24

verified calculation of three-dimensional plasma continuity at the geomagnetic pole [Dahlgren et al., 2012a; Perry et al., 2015; Semeter et al., 2014...variations in a camera system. This data flow describes a forward model, which may be reversed to reconstruct the magnetospheric drivers, in this case

Identifications of the polar cap boundary and the auroral belt in the high-altitude magnetosphere: a model for field-aligned currents

International Nuclear Information System (INIS)

Sugiura, M.

1975-01-01

By means of the Ogo 5 Goddard Space Flight Center fluxgate magnetometer data the polar cap boundary is identified in the high-altitude magnetosphere by a sudden transition from a dipolar field to a more taillike configuration. It is inferred that there exists a field-aligned-current layer at the polar cap boundary. In the night side magnetosphere the polar cap boundary is identified as the high-latitude boundary of the plasma sheet. The field-aligned current flows downward to the ionosphere on the morning side of the magnetosphere and upward from the ionosphere on the afternoon side. The basic pattern of the magnetic field variations observed during the satellite's traversal of the auroral belt is presented. Currents flow in opposite directions in the two field-aligned-current layers. The current directions in these layers as observed by Ogo 5 in the high-altitude magnetosphere are the same as those observed at low altitudes by the polar-orbiting Triad satellite (Armstrong and Zmuda, 1973). The magnetic field in the region where the lower-latitude field-aligned-current layer is situated is essentially meridional. A model is presented in which two field-aligned-current systems, one at the polar cap boundary and the other on the low-latitude part of the auroral belt, are main []y connected by ionospheric currents flowing across the auroral belt. The existence of field-aligned currents deduced from the Ogo 5 observations is a permanent feature of the magnetosphere. Intensifications of the field-aligned currents and occurrences of multiple pairs of field-aligned-current layers characterize the disturbed conditions of these regions

Magnetosphere Modeling: From Cartoons to Simulations

Science.gov (United States)

Gombosi, T. I.

2017-12-01

Over the last half a century physics-based global computer simulations became a bridge between experiment and basic theory and now it represents the "third pillar" of geospace research. Today, many of our scientific publications utilize large-scale simulations to interpret observations, test new ideas, plan campaigns, or design new instruments. Realistic simulations of the complex Sun-Earth system have been made possible by the dramatically increased power of both computing hardware and numerical algorithms. Early magnetosphere models were based on simple E&M concepts (like the Chapman-Ferraro cavity) and hydrodynamic analogies (bow shock). At the beginning of the space age current system models were developed culminating in the sophisticated Tsyganenko-type description of the magnetic configuration. The first 3D MHD simulations of the magnetosphere were published in the early 1980s. A decade later there were several competing global models that were able to reproduce many fundamental properties of the magnetosphere. The leading models included the impact of the ionosphere by using a height-integrated electric potential description. Dynamic coupling of global and regional models started in the early 2000s by integrating a ring current and a global magnetosphere model. It has been recognized for quite some time that plasma kinetic effects play an important role. Presently, global hybrid simulations of the dynamic magnetosphere are expected to be possible on exascale supercomputers, while fully kinetic simulations with realistic mass ratios are still decades away. In the 2010s several groups started to experiment with PIC simulations embedded in large-scale 3D MHD models. Presently this integrated MHD-PIC approach is at the forefront of magnetosphere simulations and this technique is expected to lead to some important advances in our understanding of magnetosheric physics. This talk will review the evolution of magnetosphere modeling from cartoons to current systems

Global Scale Periodic Responses in Saturn’s Magnetosphere

Science.gov (United States)

Jia, Xianzhe; Kivelson, Margaret G.

2017-10-01

Despite having an axisymmetric internal magnetic field, Saturn’s magnetosphere exhibits periodic modulations in a variety of properties at periods close to the planetary rotation period. While the source of the periodicity remains unidentified, it is evident from Cassini observations that much of Saturn’s magnetospheric structure and dynamics is dominated by global-scale responses to the driving source of the periodicity. We have developed a global MHD model in which a rotating field-aligned current system is introduced by imposing vortical flows in the high-latitude ionosphere in order to simulate the magnetospheric periodicities. The model has been utilized to quantitatively characterize various periodic responses in the magnetosphere, such as the displacement of the magnetopause and bow shock and flapping of the tail plasma sheet, all of which show quantitative agreement with Cassini observations. One of our model predictions is periodic release of plasmoids in the tail that occurs preferentially in the midnight-to-dawn local time sector during each rotation cycle. Here we present detailed analysis of the periodic responses seen in our simulations focusing on the properties of plasmoids predicted by the model, including their spatial distribution, occurrence frequency, and mass loss rate. We will compare these modeled parameters with published Cassini observations, and discuss their implications for interpreting in-situ measurements.

Long term ionospheric electron content variations over Delhi

Directory of Open Access Journals (Sweden)

J. K. Gupta

Full Text Available Ionospheric electron content (IEC observed at Delhi (geographic co-ordinates: 28.63°N, 77.22°E; geomagnetic co-ordinates: 19.08°N, 148.91°E; dip Latitude 24.8°N, India, for the period 1975–80 and 1986–89 belonging to an ascending phase of solar activity during first halves of solar cycles 21 and 22 respectively have been used to study the diurnal, seasonal, solar and magnetic activity variations. The diurnal variation of seasonal mean of IEC on quiet days shows a secondary peak comparable to the daytime peak in equinox and winter in high solar activity. IEC_max (daytime maximum value of IEC, one per day shows winter anomaly only during high solar activity at Delhi. Further, IEC_max shows positive correlation with F_10.7 up to about 200 flux units at equinox and 240 units both in winter and summer; for greater F_10.7 values, IEC_max is substantially constant in all the seasons. IEC_max and magnetic activity (A_p are found to be positively correlated in summer in high solar activity. Winter IEC_max shows positive correlation with A_p in low solar activity and negative correlation in high solar activity in both the solar cycles. In equinox IEC_max is independent of A_p in both solar cycles in low solar activity. A study of day-to-day variations in IEC_max shows single day and alternate day abnormalities, semi-annual and annual variations controlled by the equatorial electrojet strength, and 27-day periodicity attributable to the solar rotation.

Key words: Ionosphere (equatorial ionosphere · Magnetospheric physics (magnetosphere · ionosphere interactions · Radio science (ionospheric physics

Estimation of electric fields and currents from International Magnetospheric Study magnetometer data for the CDAW 6 intervals: Implications for substorm dynamics

International Nuclear Information System (INIS)

Kamide, Y.; Baumjohann, W.

1985-01-01

Using a recently developed numerical scheme combined with International Magnetospheric Study magnetometer data and the Rice University Ionospheric conductivity model as input, the global distribution of the key ionospheric parameters is estimated for the Coordinated Data Analysis Workshop (CDAW) 6 intervals. These outputs include ionospheric electric fields and currents, field-aligned currents and Joule heat production rate at high latitudes, and are compiled in the form of a color movie film, which demonstrates dynamics of substorm changes of the three-dimensional current system as well as of the associated potential pattern. The present paper gives, on the basis of the space-time distribution of the key parameters, the substorm time frame that can be referenced to in terms of the substorm phases when discussing some other magnetospheric and ionospheric records. The distinction between ''substorm expansion'' and ''enhanced convection'' current systems is presented on the basis of the conventional equivalent current and potential patterns and ''true'' ionospheric currents. Although the auroral electrojets flow rather contiguously throughout the dark sector, there are several separate source regions of Joule heating from the electrojet currents. This indicates that the relative importance of the ionospheric conductivity and the electric field in the ionospheric currents varies considerably depending upon latitude and local time. A possible difference in the generation mechanisms of isolated and continuous substorm activity is also discussed to some extent in the light of the two CDAW 6 intervals

The ionosphere of Europa from Galileo radio occultations

Science.gov (United States)

Kliore, A. J.; Hinson, D. P.; Flasar, F. M.; Nagy, A. F.; Cravens, T. E.

1997-01-01

The Galileo spacecraft performed six radio occultation observations of Jupiter's Galilean satellite Europa during its tour of the jovian system. In five of the six instances, these occultations revealed the presence of a tenuous ionosphere on Europa, with an average maximum electron density of nearly 10(4) per cubic centimeter near the surface and a plasma scale height of about 240 +/- 40 kilometers from the surface to 300 kilometers and of 440 +/- 60 kilometers above 300 kilometers. Such an ionosphere could be produced by solar photoionization and jovian magnetospheric particle impact in an atmosphere having a surface density of about 10(8) electrons per cubic centimeter. If this atmosphere is composed primarily of O2, then the principal ion is O2+ and the neutral atmosphere temperature implied by the 240-kilometer scale height is about 600 kelvin. If it is composed of H2O, the principal ion is H3O+ and the neutral temperature is about 340 kelvin. In either case, these temperatures are much higher than those observed on Europa's surface, and an external heating source from the jovian magnetosphere is required.

Multi-event study of high-latitude thermospheric wind variations at substorm onset with a Fabry-Perot interferometer at Tromsoe, Norway

Science.gov (United States)

Xu, H.; Shiokawa, K.; Oyama, S. I.; Otsuka, Y.

2017-12-01

We studied the high-latitude thermospheric wind variations near the onset time of isolated substorms. Substorm-related energy input from the magnetosphere to the polar ionosphere modifies the high-latitude ionosphere and thermosphere. For the first time, this study showed the characteristics of high-latitude thermospheric wind variations at the substorm onset. We also investigated the possibility of these wind variations as a potential trigger of substorm onset by modifying the ionospheric current system (Kan, 1993). A Fabry-Perot interferometer (FPI) at Tromsoe, Norway provided wind measurements estimated from Doppler shift of both red-line (630.0 nm for the F region) and green-line (557.7 nm for the E region) emissions of aurora and airglow. We used seven-year data sets obtained from 2009 to 2015 with a time resolution of 13 min. We first identified the onset times of local isolated substorms using ground-based magnetometer data obtained at the Tromsoe and Bear Island stations, which belongs to the IMAGE magnetometer chain. We obtained 4 red-line events and 5 green-line events taken place at different local times. For all these events, the peak locations of westward ionospheric currents identified by the ground-based magnetometer chain were located at the poleward side of Tromsoe. Then, we calculated two weighted averages of wind velocities for 30 min around the onset time and 30 min after the onset time of substorms. We evaluated differences between these two weighted averages to estimate the strength of wind changes. The observed wind changes at these substorm onsets were less than 49 m/s (26 m/s) for red-line (green-line) events, which are much smaller than the typical plasma convection speed. This indicates that the plasma motion caused by substorm-induced thermospheric winds through ion-neutral collisions is a minor effect as the driver of high-latitude plasma convection, as well as the triggering of substorm onset. We discuss possible causes of these

The non-linear response of the magnetosphere: 30 October 1978

International Nuclear Information System (INIS)

Price, C.P.; Prichard, D.

1993-01-01

The authors address the question of whether the response of the earth magnetosphere to the solar wind can be viewed as a nonlinear phenomena, rather than a linear response. The difficulty in answering this question is that the driving function, namely the solar wind, is very aperiodic, and it is difficult to argue that the system has time to go to any sort of a steady state in response to the driving force, prior to its making another random change. The application of nonlinear analysis methods in the face of this type of system is very limited. The authors pick a particular day, namely October 30, 1978, when the solar wind was very uniform for an extended period of time, and there is the possibility the system could converge to some type of strange attractor state within this period. They look at the auroral electrojet as a measure of the potential nonlinear response of the magnetosphere, and apply both nonlinear and linear analysis procedures to the data to try to determine if the data would support a nonlinear response of the magnetosphere to the solar wind driver, taken as the product of the solar wind speed v, and the southward component of the interplanetary magnetic field B s

The Sun and Earth

Science.gov (United States)

Gopalswamy, Natchimuthuk

2012-01-01

Thus the Sun forms the basis for life on Earth via the black body radiation it emits. The Sun also emits mass in the form of the solar wind and the coronal mass ejections (CMEs). Mass emission also occurs in the form of solar energetic particles (SEPs), which happens during CMEs and solar flares. Both the mass and electromagnetic energy output of the Sun vary over a wide range of time scales, thus introducing disturbances on the space environment that extends from the Sun through the entire heliosphere including the magnetospheres and ionospheres of planets and moons of the solar system. Although our habitat is located in the neutral atmosphere of Earth, we are intimately connected to the non-neutral space environment starting from the ionosphere to the magnetosphere and to the vast interplanetary space. The variability of the solar mass emissions results in the interaction between the solar wind plasma and the magnetospheric plasma leading to huge disturbances in the geospace. The Sun ionizes our atmosphere and creates the ionosphere. The ionosphere can be severely disturbed by the transient energy input from solar flares and the solar wind during geomagnetic storms. The complex interplay between Earth's magnetic field and the solar magnetic field carried by the solar wind presents varying conditions that are both beneficial and hazardous to life on earth. This seminar presents some of the key aspects of this Sun-Earth connection that we have learned since the birth of space science as a scientific discipline some half a century ago.

Eigenmode analysis of coupled magnetohydrodynamic oscillations in the magnetosphere

International Nuclear Information System (INIS)

Fujita, S.; Patel, V.L.

1992-01-01

The authors have performed an eigenmode analysis of the coupled magnetohydrodynamic oscillations in the magnetosphere with a dipole magnetic field. To understand the behavior of the spatial structure of the field perturbations with a great accuracy, they use the finite element method. The azimuthal and radial electric field perturbations are assumed to vanish at the ionosphere, and the azimuthal electric field is assumed to be zero on the outer boundary. The global structures of the electromagnetic field perturbations associated with the coupled magnetohydrodynamic oscillations are presented. In addition, the three-dimensional current system associated with the coupled oscillations is numerically calculated and the following characteristics are found: (1) A strong field-aligned current flows along a resonant field line. The current is particularly strong near the ionosphere. (2) The radial current changes its direction on the opposite sides of the resonant L shell. Unlike the field-aligned current, the radial currents exist in the entire magnetosphere. (3) Although the azimuthal and radial currents are intense on the resonant field line, these currents do not form a loop in the plane perpendicular to the ambient magnetic field. Therefore the field-aligned component of the perturbed magnetic field does not have a maximum at the resonant L shell

Auroral vortex street formed by the magnetosphere–ionosphere coupling instability

Directory of Open Access Journals (Sweden)

Y. Hiraki

2015-02-01

Full Text Available By performing three-dimensional magnetohydrodynamic simulations including Alfvén eigenmode perturbations most unstable to the ionospheric feedback effects, we examined the auroral vortex street that often appears just before substorm onset. We found that an initially placed arc splits, intensifies, and rapidly deforms into a vortex street. We also found that there is a critical convection electric field for growth of the Alfvén eigenmodes. The vortex street is shown to be a consequence of coupling between the magnetospheric Alfvén waves carrying field-aligned currents and the ionospheric density waves driven by Pedersen/Hall currents.

DEMETER observations of manmade waves that propagate in the ionosphere

Science.gov (United States)

Parrot, Michel

2018-01-01

This paper is a review of manmade waves observed by the ionospheric satellite DEMETER. It concerns waves emitted by the ground-based VLF and ELF transmitters, by broadcasting stations, by the power line harmonic radiation, by industrial noise, and by active experiments. Examples are shown including, for the first time, the record of a wave coming from an ELF transmitter. These waves propagate upwards in the magnetosphere and they can be observed in the magnetically conjugated region of emission. Depending on their frequencies, they perturb the ionosphere and the particles in the radiation belts, and additional emissions are triggered. xml:lang="fr"

Geomagnetic storm effects in ionospheric TEC at an euatorial station: contribution of EXB drifts and meridional neutral winds

International Nuclear Information System (INIS)

Dabas, R.S.; Jain, A.R.

1985-01-01

Storm-time variations in TEC measurements at the Indian station Ootacamund with IEC data for four stations in the anomaly region. Variations in Nsub(T)(OOTY) are found to be smaller compared to those observed at anomaly stations. The equatorial electrojet control of Nsub(T)(OOTY) is weaker compared to that of Nsub(m)F2. This result and absence of midday biteout in Nsub(T)(OOTY) are interpreted in terms of plasma exchange between ionosphere and plasmasphere which, to some extent, compensates the loss of plasma in the column due to E x B drifts. The anomaly depth is found to be well correlated with the electrojet strength. It is also noticed that for the same anomaly is weaker on a storm day than for quiet days. This is interpreted in terms of converging equatorward meridional winds. Thus, ionosphere-plasmasphere plasma exchange and, during disturbed period, the converging equatorward meridional winds also have significant effects on the distribution of ionization at these latitudes though the E x B drifts are most important in affecting the ionization distribution at low latitudes. (author)

New Model for Ionospheric Irregularities at Mars

Science.gov (United States)

Keskinen, M. J.

2018-03-01

A new model for ionospheric irregularities at Mars is presented. It is shown that wind-driven currents in the dynamo region of the Martian ionosphere can be unstable to the electromagnetic gradient drift instability. This plasma instability can generate ionospheric density and magnetic field irregularities with scale sizes of approximately 15-20 km down to a few kilometers. We show that the instability-driven magnetic field fluctuation amplitudes relative to background are correlated with the ionospheric density fluctuation amplitudes relative to background. Our results can explain recent observations made by the Mars Atmosphere and Volatile EvolutioN spacecraft in the Martian ionosphere dynamo region.

Ionospheric effects of rocket exhaust products: Skylab and HEAO-C

International Nuclear Information System (INIS)

Zinn, J.; Sutherland, C.D.; Duncan, L.M.; Stone, S.N.

1981-01-01

This paper is about ionospheric F-layer depletions produced by chemical reactions with exhaust gases from large rockets. It describes a 2-dimensional computer model of the ionosphere, and it compares model results with experimental data on the structure and variability of the natural ionosphere, as well as data on ionospheric holes produced by the launches of Skylab (May, 1973) and HEAO-C (September, 1979). It also describes measurements made in conjunction with the HEAO-C launch. The computer model includes an approximate representation of thermospheric tidal winds and E fields in addition to vertical motions associated with diurnal changes in temperature. The computed ionospheric structure is sensitive to all the above. For a small number of cases, results are compared of computations of the normal diurnal variations of ionospheric structure with incoherent scatter and total electron content data. Computations of ionospheric depletions from the Skylab and HEAO-C launches are in satisfactory agreement with the observations. The winds appear to be essential for interpretation of the Skylab results

An ionospheric index suitable for estimating the degree of ionospheric perturbations

Science.gov (United States)

Wilken, Volker; Kriegel, Martin; Jakowski, Norbert; Berdermann, Jens

2018-03-01

Space weather can strongly affect trans-ionospheric radio signals depending on the used frequency. In order to assess the strength of a space weather event from its origin at the sun towards its impact on the ionosphere a number of physical quantities need to be derived from scientific measurements. These are for example the Wolf number sunspot index, the solar flux density F10.7, measurements of the interplanetary magnetic field, the proton density, the solar wind speed, the dynamical pressure, the geomagnetic indices Auroral Electrojet, Kp, Ap and Dst as well as the Total Electron Content (TEC), the Rate of TEC, the scintillation indices S4 and σ(ϕ) and the Along-Arc TEC Rate index index. All these quantities provide in combination with an additional classification an orientation in a physical complex environment. Hence, they are used for brief communication of a simplified but appropriate space situation awareness. However, space weather driven ionospheric phenomena can affect many customers in the communication and navigation domain, which are still served inadequately by the existing indices. We present a new robust index, that is able to properly characterize temporal and spatial ionospheric variations of small to medium scales. The proposed ionospheric disturbance index can overcome several drawbacks of other ionospheric measures and might be suitable as potential driver for an ionospheric space weather scale.

Ionospheric effects of magnetospheric substorms during SUNDIAL and their modelling

International Nuclear Information System (INIS)

Goncharova, E.E.; Kishcha, P.V.; Shashun'kina, V.M.; Telegin, V.A.

1993-01-01

Ionospheric effects of substorms are considered using the networks of the vertical probing stations during SUNDIAL periods. Calculations of electron concentration distribution and comparison of calculation results with experimental data are conducted on the basis of the developed technique of simulation of large-scale internal gravitational wave effects

Ground observations of magnetospheric boundary layer phenomena

International Nuclear Information System (INIS)

McHenry, M.A.; Clauer, C.R.; Friis-Christensen, E.; Newell, P.T.; Kelly, J.D.

1990-01-01

Several classes of traveling vortices in the dayside ionospheric convection have been detected and tracked using the Greenland magnetometer chain (Friis-Christensen et al., 1988, McHenry et al., 1989). One class observed during quiet times consists of a continuous series of vortices moving generally anti-sunward for several hours at a time. The vortices strength is seen to be approximately steady and neighboring vortices rotate in opposite directions. Sondrestrom radar observations show that the vortices are located at the ionospheric convection reversal boundary. Low altitude DMSP observations indicate the vortices are on field lines which map to the inner edge of the low latitude boundary layer. Because the vortices are conjugate to the boundary layer, repeat in a regular fashion and travel antisunward, the authors argue that this class of vortices is caused by the Kelvin-Helmholtz instability of the inner edge of the magnetospheric boundary layer

Ionospheric conductivity dependence of dayside region-0, 1, and 2 field-aligned current systems: statistical study with DMSP-F7

Directory of Open Access Journals (Sweden)

K. Haraguchi

2004-09-01

Full Text Available The present study statistically examines the dependence of the intensities of dayside (MLT=8-12h large-scale field-aligned currents (FACs on the ionospheric conductance using the summary data of DMSP-F7 constructed by the procedure of Higuchi and Ohtani (2000. We have found that, in the dayside region, R1 and R0 have a higher correlation between ionospheric conductivity and FAC intensity than R2, suggesting that R0 and R1 are driven by a more voltage-like source than R2. This result is consistent with the idea that R1 and R0 are driven by the interaction between the solar wind and the open magnetospheric magnetic field. We have also found that dayside FAC intensities are latitudinally well balanced when they have a three sheet structure (R0, R1 and R2; on the other hand, for a two sheet structure (R1 and R2, the intensity of R1 is larger than that of R2, so that the net current has the polarity of R1.

Discontinuities and the magnetospheric phenomena

International Nuclear Information System (INIS)

Rajaram, R.; Kalra, G.L.; Tandon, J.N.

1978-01-01

Wave coupling at contact discontinuities has an important bearing on the transmission of waves from the solar wind into the magnetosphere across the cusp region of the solar wind-magnetosphere boundary and on the propagation of geomagnetic pulsations in the polar exosphere. Keeping this in view, the problems of wave coupling across a contact discontinuity in a collisionless plasma, described by a set of double adiabatic fluid equations, is examined. The magnetic field is taken normal to the interface and it is shown that total reflection is not possible for any angle of incidence. The Alfven and the magneto-acoustic waves are not coupled. The transmission is most efficient for small density discontinuities. Inhibition of the transmission of the Alfven wave by the sharp density gradients above the F2-peak in the polar exosphere appears to account for the decrease in the pulsation amplitude, on the ground, as the poles are approached from the auroral zone. (author)

Satellite and Ground Signatures of Kinetic and Inertial Scale ULF Alfven Waves Propagating in Warm Plasma in Earth's Magnetosphere

Science.gov (United States)

Rankin, R.; Sydorenko, D.

2015-12-01

Results from a 3D global numerical model of Alfven wave propagation in a warm multi-species plasma in Earth's magnetosphere are presented. The model uses spherical coordinates, accounts for a non-dipole magnetic field, vertical structure of the ionosphere, and an air gap below the ionosphere. A realistic density model is used. Below the exobase altitude (2000 km) the densities and the temperatures of electrons, ions, and neutrals are obtained from the IRI and MSIS models. Above the exobase, ballistic (originating from the ionosphere and returning to ionosphere) and trapped (bouncing between two reflection points above the ionosphere) electron populations are considered similar to [Pierrard and Stegen (2008), JGR, v.113, A10209]. Plasma parameters at the exobase provided by the IRI are the boundary conditions for the ballistic electrons while the [Carpenter and Anderson (1992), JGR, v.97, p.1097] model of equatorial electron density defines parameters of the trapped electron population. In the simulations that are presented, Alfven waves with frequencies from 1 Hz to 0.01 Hz and finite azimuthal wavenumbers are excited in the magnetosphere and compared with Van Allen Probes data and ground-based observations from the CARISMA array of ground magnetometers. When short perpendicular scale waves reflect form the ionosphere, compressional Alfven waves are observed to propagate across the geomagnetic field in the ionospheric waveguide [e.g., Lysak (1999), JGR, v.104, p.10017]. Signals produced by the waves on the ground are discussed. The wave model is also applied to interpret recent Van Allen Probes observations of kinetic scale ULF waves that are associated with radiation belt electron dynamics and energetic particle injections.

Simulating the dependence of seismo-ionospheric coupling on the magnetic field inclination

Science.gov (United States)

Mohan Joshi, Lalit; Sripathi, Samireddipelle; Kumar, Muppidi Ravi; Alam Kherani, Esfhan

2018-01-01

Infrasound generated during a seismic event upon reaching the ionospheric heights possesses the ability to perturb the ionosphere. Detailed modelling investigation considering 1-D dissipative linear dynamics, however, indicates that the magnitude of ionospheric perturbation strongly depends on the magnetic field inclination. Physics-based SAMI2 model codes have been utilized to simulate the ionosphere perturbations that are generated due to the action of the vertical wind perturbations associated with the seismic infrasound. The propagation of the seismic energy and the vertical wind perturbations associated with the infrasound in the model has been considered to be symmetric about the epicentre in the north-south directions. Ionospheric response to the infrasound wind, however, has been highly asymmetric in the model simulation in the north-south directions. This strong asymmetry is related to the variation in the inclination of the Earth's magnetic field north and south of the epicentre. Ionospheric monitoring generally provides an efficient tool to infer the crustal propagation of the seismic energy. However, the results presented in this paper indicate that the mapping between the crustal process and the ionospheric response is not a linear one. These results also imply that the lithospheric behaviour during a seismic event over a wide zone in low latitudes can be estimated through ionospheric imaging only after factoring in the magnetic field geometry.

Simulating the dependence of seismo-ionospheric coupling on the magnetic field inclination

Directory of Open Access Journals (Sweden)

L. M. Joshi

2018-01-01

Full Text Available Infrasound generated during a seismic event upon reaching the ionospheric heights possesses the ability to perturb the ionosphere. Detailed modelling investigation considering 1-D dissipative linear dynamics, however, indicates that the magnitude of ionospheric perturbation strongly depends on the magnetic field inclination. Physics-based SAMI2 model codes have been utilized to simulate the ionosphere perturbations that are generated due to the action of the vertical wind perturbations associated with the seismic infrasound. The propagation of the seismic energy and the vertical wind perturbations associated with the infrasound in the model has been considered to be symmetric about the epicentre in the north–south directions. Ionospheric response to the infrasound wind, however, has been highly asymmetric in the model simulation in the north–south directions. This strong asymmetry is related to the variation in the inclination of the Earth's magnetic field north and south of the epicentre. Ionospheric monitoring generally provides an efficient tool to infer the crustal propagation of the seismic energy. However, the results presented in this paper indicate that the mapping between the crustal process and the ionospheric response is not a linear one. These results also imply that the lithospheric behaviour during a seismic event over a wide zone in low latitudes can be estimated through ionospheric imaging only after factoring in the magnetic field geometry.

The Effect of Sub-Auroral Polarization Streams (SAPS) on Ionosphere and Thermosphere during 2015 St. Patrick's Day storm: Global Ionosphere-Thermosphere Model (GITM) Simulations

Science.gov (United States)

Guo, J.; Deng, Y.; Zhang, D.; Lu, Y.; Sheng, C.

2017-12-01

Sub-Auroral Polarization Streams (SAPS) are incorporated into the non-hydrostatic Global Ionosphere-Thermosphere Model (GITM), revealing the complex effects on neutral dynamics and ion-neutral coupling processes. The intense westward ion stream could enhance the neutral zonal wind within the SAPS channel. Through neutral dynamics the neutrals then divide into two streams, one turns poleward and the other turns equatorward, forming a two-cell pattern in the SAPS-changed wind. The significant Joule heating induced by SAPS also leads to traveling atmospheric disturbances (TAD) accompanied by traveling ionospheric disturbances (TID), increasing the total electron content (TEC) by 2-8 TECu in the mid-latitude ionosphere. We investigate the potential causes of the reported poleward wind surge during the St. Patrick's Day storm in 2015. It is confirmed that Coriolis force on the westward zonal wind can contribute the poleward wind during post-SAPS interval. In addition, the simulations imply that the sudden decrease of heating rate within auroral oval could result in a TAD propagating equatorward, which could also be responsible for the sudden poleward wind surge. This study highlights the complicated effects of SAPS on ion-neutral coupling and neutral dynamics.

On the role of neutral flow in field-aligned currents

Science.gov (United States)

Mannucci, Anthony J.; Verkhoglyadova, Olga P.; Meng, Xing; McGranaghan, Ryan

2018-01-01

In this brief note we explore the role of the neutral atmosphere in magnetosphere-ionosphere coupling. We analyze momentum balance in the ion rest frame to form hypotheses regarding the role of neutral momentum in the lower ionosphere during geomagnetic storms. Neutral momentum that appears in the ion rest frame is likely the result of momentum imparted to ionospheric ions by solar wind flow and the resultant magnetospheric dynamics. The resulting ion-neutral collisions lead to the existence of an electric field. Horizontal electron flow balances the momentum supplied by this electric field. We suggest a possible role played by the neutral atmosphere in generating field-aligned currents due to local auroral heating. Our physical interpretation suggests that thermospheric neutral dynamics plays a complementary role to the high-latitude field-aligned currents and electric fields resulting from magnetospheric dynamics.

Space physics strategy-implementation study. Volume 1: Goals, objectives, strategy. A report to the Space Physics Subcommittee of the Space Science and Applications Advisory Committee

Science.gov (United States)

1991-01-01

Space physics is defined as the study of the heliosphere as one system; that is, of the Sun and solar wind, and their interactions with the upper atmospheres, ionospheres, and magnetospheres of the planets and comets, with energetic particles, and with the interstellar medium. This report contains a number of reports by different panels on the major topics in the space physics program including: (1) the cosmic and heliospheric physics program for the years 1995 to 2010; (2) ionosphere, thermosphere, and mesosphere studies; (3) magnetospheric physics; (4) solar physics; and (5) space physics theory.

PNST: half-course colloquium - Hendaye, 14-16 March 2016. Summaries and list of participants

International Nuclear Information System (INIS)

Aboudarham, Jean; Alexandrova, Olga; Amsif, Kader; Andre, Nicolas; Astafyeva, Elvira; Auchere, Frederic; Aunai, Nicolas; Baudin, Frederic; Belmont, Gerard; Benacquista, Remi; Berthomier, Matthieu; Biree, Lionel; Blanc, Michel; Bommier, Veronique; Bourdarie, Sebastien; Breuillard, Hugo; Brun, Allan Sacha; Buchlin, Eric; Canu, Patrick; Cara, Antoine; Carley, Eoin; Cecconi, Baptiste; Celestin, Sebastien; Chane-Yook, Martine; Chaufray, Jean-Yves; Cherniak, Iurii; Chevalier, Christiane; Coisson, Pierdavide; Corbard, Thierry; Cornilleau-Wehrlin, Nicole; Dalmasse, Kevin; Dandouras, Iannis; Dargent, Jeremy; Delcourt, Dominique; Dintrans, Boris; Dubau, Jacques; Dudok De Wit, Thierry; Emeriau-Viard, Constance; Esteban Hernandez, Rosa; Fabbro, Vincent; Farges, Thomas; Faurobert, Marianne; Fontaine, Dominique; Froment, Clara; Fruit, Gabriel; Gabriel, Alan; Galmiche, Aurelien; Galtier, Sebastien; Gelly, Bernard; Genot, Vincent; Gordino, Miguel; Grappin, Roland; Gravet, Romanic; Griton, Lea; Gruet, Marina; Guennou, Chloe; Guillemant, Stanislas; Hassler, Don; Henri, Pierre; Herrera, Damien; Hulot, Gauthier; Hung, Ching Pui; Ihaddadene, Kevin; Janvier, Miho; Jouve, Laurene; Kacem, Issaad; Klein, Karl-Ludwig; Koutroumpa, Dimitra; Krasnosselskikh, Vladimir; Kretzschmar, Matthieu; Lamy, Laurent; Lavraud, Benoit; Lazaro, Didier; Le Chat, Gaetan; Le Contel, Olivier; Leblanc, Francois; Leclercq, Ludivine; Lembege, Bertrand; Lemorton, Joel; Lilensten, Jean; Lion, Sonny; Lopez Ariste, Arturo; Louis, Corentin; Maksimovic, Milan; Marchaudon, Aurelie; Masson, Sophie; Mazelle, Christian; Mirioni, Laurent; Moncuquet, Michel; Montagud, Victor; Morbidelli, Alessandro; Mottez, Fabrice; Musset, Sophie; Nicolas, Loic; Oza, Apurva; Palin, Laurianne; Pariat, Etienne; Perrone, Denise; Pincon, Jean-Louis; Pinto, Rui; Pitout, Frederic; Plotnikov, Illya; Prado, Jean-Yves; Quemerais, Eric; Renaud, Catherine; Retino, Alessandro; Reville, Victor; Roudier, Thierry; Rouillard, Alexis; Rozelot, Jean-Pierre; Sahraoui, Fouad; Salas Matamoros, Carolina; Sanchez-Diaz, Eduardo; Sarria, David; Savoini, Philippe; Schmieder, Brigitte; Sicard-Piet, Angelica; Solomon, Jacques; Steckiewicz, Morgane; Strugarek, Antoine; Turc, Lucile; Varela, Jacobo; Verdini, Andrea; Vernisse, Yoann; Vial, Jean-Claude; Vilmer, Nicole; Zakharenkova, Irina; Zaouar, Naima; Zarka, Philippe; Zucca, Pietro; Zuccarello, Francesco

2016-03-01

This colloquium was organized at the half-course of the French 'Sun-Earth' national programme (PNST); it was intended for all researchers and students in the domain of magnetized plasmas in solar and terrestrial environments. It also concerns solar and stellar magnetism and planetary plasmas which are at the interfaces between PNST, stellar physics and planetology. The colloquium is organized around 7 main themes: simulations and numerical tools; new missions and instrumentation (ground and space); couplings between plasma envelopes (i.e. interior/corona/solar wind, solar wind/magnetosphere, magnetosphere/ionosphere/high atmosphere); multi-scale energy transport and turbulence (i.e. Sun, solar wind, magnetospheres, ion and electronic scales, dynamo); particle acceleration mechanisms and plasma heating (i.e. corona and solar winds, magnetospheres, energetic particles); eruptive or impulsive activity in plasmas (i.e. corona, terrestrial and planetary magnetospheres); Sun-Earth relations and space meteorology (i.e. observation/forecasting of solar activity, space environment, geomagnetic conditions, irradiance variability)

Characteristics of the polar cap at ionospheric levels and present understanding of the physical processes that give rise to these characteristics

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Brekke, A.

1983-01-01

This chapter discusses the relationship between the interplanetary magnetic field (IMF) and various polar cap current systems, such as the DP2-system and the S /SUB q/ P-system. The disagreements concerning these systems are examined. Topics considered include the polar cap (a result of an open magnetosphere); studies of the polar cap magnetic field variations; the DP2-current system and its relation to the IMF; the polar cap current system during a northward IMF; the azimuthal component of IMF and its influence on the polar cap magnetic field variations; the electric potential distribution on the polar cap; rocket observations of the polar cap electric field; the auroral arcs as a visible trace of the ionospheric convection; neutral wind measurements in the polar cap F-region; and further studies of polar cap dynamics. The focus is on the polar region inside the auroral oval. It is suggested that more research is needed of the polar cap current system in order to understand the magnetosphereionosphere coupling, with the polar cap ionospheric conductivity distribution being the most crucial parameter

How to emit a high-power electron beam from a magnetospheric spacecraft?

Science.gov (United States)

Delzanno, G. L.; Lucco Castello, F.; Borovsky, J.; Miars, G.; Leon, O.; Gilchrist, B. E.

2017-12-01

The idea of using a high-power electron beam to actively probe magnetic-field-line connectivity in space has been discussed since the 1970's. It could solve longstanding questions in magnetospheric/ionospheric physics by establishing causality between phenomena occurring in the magnetosphere and their image in the ionosphere. However, this idea has never been realized onboard a magnetospheric spacecraft because the tenuous magnetospheric plasma cannot provide the return current necessary to keep the charging of the spacecraft under control. Recently, Delzanno et al. [1] have proposed a spacecraft-charging mitigation scheme to enable the emission of a high-power electron beam from a magnetospheric spacecraft. It is based on the plasma contactor, i.e. a high-density neutral plasma emitted prior to and with the electron beam. The contactor acts as an ion emitter (not as an electron collector, as previously thought): a high ion current can be emitted off the quasi-spherical contactor surface, without the strong space-charge limitations typical of planar ion beams, and the electron-beam current can be successfully compensated. In this work, we will discuss our theoretical/simulation effort to improve the understanding of contactor-based ion emission. First, we will present a simple mathematical model useful for the interpretation of the results of [1]. The model is in spherical geometry and the contactor dynamics is described by only two surfaces (its quasi-neutral surface and the front of the outermost ions). It captures the results of self-consistent Particle-In-Cell (PIC) simulations with good accuracy and highlights the physics behind the charge-mitigation scheme clearly. PIC simulations connecting the 1D model to the actual geometry of the problem will be presented to obtain the scaling of the spacecraft potential varying contactor emission area. Finally, results for conditions relevant to an actual mission will also be discussed. [1] G. L. Delzanno, J. E. Borovsky

Substorms in the earth's magnetosphere

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Baker, D.N.

1984-01-01

Magnetospheres are plasma regions of large scale in space dominated by magnetic field effects. The earth, and many planets in our solar system, are known to have magnetospheric regions around them. Magnetospheric substorms represent the intense, rapid dissipation of energy that has been extracted from the solar wind and stored temporarily in the terrestrial magnetotail. In this paper a widely, but not universally, accepted model of substorms is described. The energy budgets, time scales, and conversion efficiencies for substorms are presented. The primary forms of substorm energy dissipation are given along with the average levels of the dissipation. Aspects of particle acceleration and precipitation, Joule heating mechanisms, ring current formation, and plasmoid escape are illustrated based on in situ observations taken from the large available data base. A brief description is given of possible analogues of substorm-like behavior in other astrophysical systems. 27 references, 12 figures

PC index as a proxy of the solar wind energy that entered into the magnetosphere: Development of magnetic substorms

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Troshichev, O. A.; Podorozhkina, N. A.; Sormakov, D. A.; Janzhura, A. S.

2014-08-01

The Polar Cap (PC) index has been approved by the International Association of Geomagnetism and Aeronomy (IAGA XXII Assembly, Merida, Mexico, 2013) as a new index of magnetic activity. The PC index can be considered to be a proxy of the solar wind energy that enters the magnetosphere. This distinguishes PC from AL and Dst indices that are more related to the dissipation of energy through auroral currents or storage of energy in the ring current during magnetic substorms or storms. The association of the PC index with the direct coupling of the solar wind energy into the magnetosphere is based upon analysis of the relationship of PC with parameters in the solar wind, on the one hand, and correlation between the time series of PC and the AL index (substorm development), on the other hand. This paper (the first of a series) provides the results of statistical investigations that demonstrate a strong correlation between the behavior of PC and the development of magnetic substorms. Substorms are classified as isolated and expanded. We found that (1) substorms are preceded by growth in the RS index, (2) sudden substorm expansion onsets are related to "leap" or "reverse" signatures in the PC index which are indicative of a sharp increase in the PC growth rate, (3) substorms start to develop when PC exceeds a threshold level 1.5 ± 0.5 mV/m irrespective of the length of the substorm growth phase, and (4) there is a linear relation between the intensity of substorms and PC for all substorm events.

Statistical study of waves distribution in the inner magnetosphere using geomagnetic indices and solar wind parameters

Science.gov (United States)

Aryan, H.; Yearby, K.; Balikhin, M. A.; Krasnoselskikh, V.; Agapitov, O. V.

2013-12-01

The interaction of gyroresonant wave particles with chorus waves largely determine the dynamics of the Earth's radiation belts that effects the acceleration and loss of radiation belt electrons. The common approach is to present model waves distribution in the inner magnetosphere under different values of geomagnetic activity as expressed by the geomagnetic indices. However it is known that solar wind parameters such as bulk velocity (V) and density (n) are more effective in the control of high energy fluxes at the geostationary orbit. Therefore in the present study the set of parameters of the wave distribution is expanded to include the solar wind parameters in addition to the geomagnetic indices. The present study examines almost four years (01, January, 2004 to 29, September, 2007) of Cluster STAFF-SA, Double Star TC1 and OMNI data in order to present a combined model of wave magnetic field intensities for the chorus waves as a function of magnetic local time (MLT), L-shell (L*), geomagnetic activity, and solar wind velocity and density. Generally, the largest wave intensities are observed during average solar wind velocities (3006cm-3. On the other hand the wave intensity is lower and limited between 06:00 to 18:00 MLT for V700kms-1.

How the effects of winds and electric fields in F2-layer storms vary with latitude and longitude - A theoretical study

Science.gov (United States)

Mendillo, M.; He, X.-Q.; Rishbeth, H.

1992-01-01

The effects of thermospheric winds and electric fields on the ionospheric F2-layer are controlled by the geometry of the magnetic field, and so vary with latitude and longitude. A simple model of the daytime F2-layer is adopted and the effects at midlatitudes (25-65 deg geographic) of three processes that accompany geomagnetic storms: (1) thermospheric changes due to auroral heating; (2) equatorward winds that tend to cancel the quiet-day poleward winds; and (3) the penetration of magnetospheric electric fields are studied. At +/- 65 deg, the effects of heating and electric fields are strongest in the longitudes toward which the geomagnetic dipole is tilted, i.e., the North American and the South Indian Ocean sectors. Because of the proximity of the geomagnetic equator to the East Asian and South American sectors, the reverse is true at +/- 25 deg.

Assessment of ionospheric Joule heating by GUMICS-4 MHD simulation, AMIE, and satellite-based statistics: towards a synthesis

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M. Palmroth

2005-09-01

Full Text Available We investigate the Northern Hemisphere Joule heating from several observational and computational sources with the purpose of calibrating a previously identified functional dependence between solar wind parameters and ionospheric total energy consumption computed from a global magnetohydrodynamic (MHD simulation (Grand Unified Magnetosphere Ionosphere Coupling Simulation, GUMICS-4. In this paper, the calibration focuses on determining the amount and temporal characteristics of Northern Hemisphere Joule heating. Joule heating during a substorm is estimated from global observations, including electric fields provided by Super Dual Auroral Network (SuperDARN and Pedersen conductances given by the ultraviolet (UV and X-ray imagers on board the Polar satellite. Furthermore, Joule heating is assessed from several activity index proxies, large statistical surveys, assimilative data methods (AMIE, and the global MHD simulation GUMICS-4. We show that the temporal and spatial variation of the Joule heating computed from the GUMICS-4 simulation is consistent with observational and statistical methods. However, the different observational methods do not give a consistent estimate for the magnitude of the global Joule heating. We suggest that multiplying the GUMICS-4 total Joule heating by a factor of 10 approximates the observed Joule heating reasonably well. The lesser amount of Joule heating in GUMICS-4 is essentially caused by weaker Region 2 currents and polar cap potentials. We also show by theoretical arguments that multiplying independent measurements of averaged electric fields and Pedersen conductances yields an overestimation of Joule heating.

Keywords. Ionosphere (Auroral ionosphere; Modeling and forecasting; Electric fields and currents

Interhemispheric ionospheric coupling at the American sector during low solar activity. 2

International Nuclear Information System (INIS)

Foerster, M.; Jakowski, N.

1986-01-01

A physical-numerical model of the coupled system ionosphere - plasmasphere - magnetically conjugated ionosphere is presented and applied to a co-rotating tube of plasma at L = 1.5 in the American sector (Cuba). Numerical simulations are carried out for low solar activity and quiet geomagnetic conditions. Observational data of Faraday content and ionosonde measurements of both solstices of 1976 (Jakowski et al., paper I) are compared with calculations using different patterns of neutral horizontal winds. Reasonable meridional wind patterns provide an annual effect of plasmapheric tube content. During December solstice the higher tube content and the convenient behaviour of meridional neutral wind in both hemispheres causes more intense nighttime fluxes into the winter ionosphere. (author)

Identification of the propagation mode of a solar wind wave associated with Pc5 pulsations in the magnetosphere

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Walker, A.D.M.; Stephenson, J.A.E. [KwaZulu-Natal Univ., Durban (South Africa). School of Chemistry and Physics

2014-07-01

A case study of a magnetohydrodynamic (MHD) wave in the solar wind that is strongly correlated with a magnetospheric field line resonance observed by the SuperDARN (Super Dual Auroral Radar Network) radar at Sanae, Antarctica is presented. The data from the ACE (Advanced Composition Explorer) satellite at the solar libration point are analysed. The data time series are bandpass filtered at the pulsation frequency and the analytic signal deduced. From these data the partition of energy between the field components is computed. It is shown that energy is equally partitioned between the kinetic energy and transverse magnetic potential energy densities. The energy flux vector is closely aligned with the background magnetic field. The transverse magnetic and velocity components are in antiphase. This is the first identification of the triggering wave as a transverse Alfven wave which originates upstream from the space craft and is propagated to the magnetosphere to trigger the pulsation.