scholarly journals <i>Letter to the Editor</i>A statistical study of the location and motion of the HF radar cusp

2002 ◽  
Vol 20 (2) ◽  
pp. 275-280 ◽  
Author(s):  
T. K. Yeoman ◽  
P. G. Hanlon ◽  
K. A. McWilliams
Keyword(s):  
Solar Wind ◽  
Continuous Monitoring ◽  
Large Scale ◽  
Statistical Study ◽  
Hf Radar ◽  
Auroral Ionosphere ◽  
Cusp Region ◽  
The North ◽  
Low Altitude ◽  
Spacecraft Data

Abstract. The large-scale and continuous monitoring of the ionospheric cusp region offered by HF radars has been exploited in order to examine the statistical location and motion of the equatorward edge of the HF radar cusp as a function of the upstream IMF BZ component. Although a considerable scatter is seen, both parameters have a clear influence from the north-south component of the IMF. Excellent agreement is achieved with previous observations from low altitude spacecraft data. The HF radar cusp region is seen to migrate equatorward at a rate of 0.02° min-1 nT-1 under IMF BZ south conditions, but remains static for IMF BZ north. The motion of the cusp implies an addition of magnetic flux of ~ 2 × 104 Wbs-1 nT-1 under IMF BZ south conditions, equivalent to a reconnection voltage of 20 kV nT-1, which is consistent with previous estimates from case studies on both the dayside and nightside regions.Key words. Ionosphere (auroral ionosphere) – Magnetospheric physics (magnetosphere-ionosphere interaction; solar wind magnetosphere interactions)

scholarly journals Influence of magnetospheric processes on winter HF radar spectra characteristics

2002 ◽  
Vol 20 (11) ◽  
pp. 1783-1793 ◽  
Author(s):  
R. André ◽  
M. Pinnock ◽  
J.-P. Villain ◽  
C. Hanuise
Keyword(s):  
Statistical Study ◽  
Classification Scheme ◽  
Spectral Width ◽  
Hf Radar ◽  
Auroral Ionosphere ◽  
Plasma Convection ◽  
Ulf Wave ◽  
Cusp Region ◽  
Magnetospheric Cusp ◽  
The Relationship

Abstract. This study investigates further the relationship between regions of the magnetosphere and the characteristics of HF radar Doppler spectra recorded in the ionospheric projection of those regions. It builds on earlier work, which has reported a relationship between the Doppler spectral width and the ionospheric projection of the magnetospheric cusp region, by introducing novel techniques for classifying the Doppler spectra recorded by the SuperDARN radars. We first review the geophysical factors that can condition the characteristics of the autocorrelation function (ACF) data produced by the radars. This leads to a classification scheme of the ACF data which is then applied to a large database compiled from winter data taken by the Northern Hemisphere Super-DARN radars. This statistical study shows that the ACF characteristics are not randomly distributed in space, but rather are spatially organized in the ionosphere. This paper suggests that these regions are ordered primarily by the low energy (<approx> 1 keV) electron precipitation region and the presence of intense ULF wave activity.Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions; plasma convection)

Large-scale electron solar wind parameters of the inner heliosphere with Parker Solar Probe/FIELDS

2020 ◽  
Author(s):  
Karine Issautier ◽  
Mingzhe Liu ◽  
Michel Moncuquet ◽  
Nicole Meyer-Vernet ◽  
Milan Maksimovic ◽  
...  
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Statistical Study ◽  
Solar Wind Speed ◽  
The Sun ◽  
Solar Wind Parameters ◽  
Power Law Index ◽  
Probe Mission ◽  
Inner Heliosphere

&lt;p&gt;We present in situ properties of electron density and temperature in the inner heliosphere obtained during the three first solar encounters at 35 solar radii of the Parker Solar Probe mission. These preliminary results, recently shown by Moncuquet et al., ApJS, 2020, are obtained from the analysis of the plasma quasi-thermal noise (QTN) spectrum measured by the radio RFS/FIELDS instrument along the trajectories extending between 0.5 and 0.17 UA from the Sun, revealing different states of the emerging solar wind, five months apart. The temperature of the weakly collisional core population varies radially with a power law index of about -0.8, much slower than adiabatic, whereas the temperature of the supra-thermal population exhibits a much flatter radial variation, as expected from its nearly collisionless state. These measured temperatures are close to extrapolations towards the Sun of Helios measurements.&lt;/p&gt;&lt;p&gt;We also present a statistical study from these in situ electron solar wind parameters, deduced by QTN spectroscopy, and compare the data to other onboard measurements. In addition, we focus on the large-scale solar wind properties. In particular, from the invariance of the energy flux, a direct relation between the solar wind speed and its density can be deduced, as we have already obtained based on Wind continuous in situ measurements (Le Chat et al., Solar Phys., 2012). We study this anti-correlation during the three first solar encounters of PSP.&lt;/p&gt;

Evolution of Turbulence in the Kelvin–Helmholtz Instability mediated by the Magnetopause and its Boundary Layer

2020 ◽  
Author(s):  
Francesca Di Mare ◽  
Luca Sorriso-Valvo ◽  
Alessandro Retino' ◽  
Francesco Malara ◽  
Hiroshi Hasegawa
Keyword(s):  
Boundary Layer ◽  
Solar Wind ◽  
Large Scale ◽  
Velocity Shear ◽  
Helmholtz Instability ◽  
Intermittent Turbulence ◽  
Large Scale Structures ◽  
Developed Turbulence ◽  
Spacecraft Data ◽  
Efficient Transfer

&lt;p&gt;The turbulence at the interface between the solar wind and the Earth&amp;#8217;s magnetosphere, mediated by the magnetopause and its boundary layer are investigated by using Geotail and THEMIS spacecraft data during ongoing Kelvin-Helmholtz instability (KHI). The efficient transfer of energy across scales for which the turbulence is responsible, achieves the connection between the macroscopic flow and the microscopic dissipation of this energy. This boundary layer is thought to be the result of the observed plasma transfer, driven by the development of the KHI, originating from the velocity shear between the solar wind and the almost static near-Earth plasma. A collection of 20 events spatially located on the tail-flank magnetopause, selected from previously studied by Hasegawa et al. 2006 and Lin et al. 2014, have been tested against standard diagnostics for intermittent turbulence. In light of the results obtained, we have investigated the behaviour of several parameters as a function of the progressive departure along the Geocentric Solar Magnetosphere coordinates, which roughly represent the direction in which we expect the KHI vortices to evolve towards fully developed turbulence. It appears that a fluctuating behaviour of the parameters exist, visible as a decreasing, quasi-periodic modulation with an associated periodicity, estimated to correspond to approximately 6.4 Earth Radii. Such observed wavelength is consistent with the estimated vortices roll-up wavelength reported in the literature for these events. If the turbulence is pre-existent, it is possible that the KHI modulates its properties along the magnetosheath, as we observed. On the other hand, if we assume that the KHI has been initiated near the magnetospheric nose and develops along the flanks, then the different intervals we study may be sampling the plasma at different stages of evolution of the KH-generated turbulence, after the instability has injected energy in a cascading process as large-scale structures.&lt;/p&gt;

scholarly journals A statistical study of the low‐altitude ionospheric magnetic fields over the north pole of Venus

2015 ◽  
Vol 120 (8) ◽  
pp. 6218-6229 ◽  
Author(s):  
T. L. Zhang ◽  
W. Baumjohann ◽  
C. T. Russell ◽  
M. N. Villarreal ◽  
J. G. Luhmann ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Statistical Study ◽  
North Pole ◽  
The North ◽  
Low Altitude

scholarly journals Nature of Large-Scale Solar Magnetic Field and Complexity of HCS as Observed in Interplanetary Plasma

1990 ◽  
Vol 142 ◽  
pp. 343-344
Author(s):  
T E Girish ◽  
S R Prabhakaran Nayar
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Large Scale ◽  
Solar Magnetic Field ◽  
Solar Rotation ◽  
Solar Wind Plasma ◽  
Heliospheric Current Sheet ◽  
The North ◽  
Interplanetary Plasma ◽  
South Asymmetry

The properties of the interplanetary plasma and magnetic field near 1 AU is determined by the nature of large-scale solar magnetic field and the associated structure of the heliospheric current sheet (HCS). Magnetic multipoles often present near the solar equator affect the solar wind plasma and magnetic field (IMF) near earth's orbit. The observation of four or more IMF sectors per solar rotation and the north-south asymmetry in the HCS are observational manifestations of the influence of solar magnetic multipoles, especially the quadrupole on the interplanetary medium (Schultz, 1973; Girish and Nayar, 1988). The solar wind plasma is known to be organised around the HCS. In this work, we have investigated the possibility of inferring i) the relative dipolar and quadrupolar heliomagnetic contributions to the HCS geometry from the observation of four sector IMF structure near earth and ii) the properties of the north-south asymmetry in HCS geometry about the heliographic equator from IMF and solar wind observations near 1 AU.

scholarly journals Statistical study of the substorm onset: its dependence on solar wind parameters and solar illumination

2005 ◽  
Vol 23 (6) ◽  
pp. 2069-2079 ◽  
Author(s):  
H. Wang ◽  
H. Lühr ◽  
S. Y. Ma ◽  
P. Ritter
Keyword(s):  
Solar Wind ◽  
Local Time ◽  
Large Scale ◽  
Statistical Study ◽  
Energetic Electron ◽  
Substorm Onset ◽  
Solar Wind Parameter ◽  
Ionospheric Conductivity ◽  
Coupling Parameters ◽  
Substorm Onsets

Abstract. Based on 1829 well-defined substorm onsets in the Northern Hemisphere, observed during a 2-year period by the FUV Imager on board the IMAGE spacecraft, a statistical study is performed. From the combination of solar wind parameter observations by ACE and magnetic field observations by the low altitude satellite CHAMP, the location of auroral breakups in response to solar illumination and solar coupling parameters are studied. Furthermore, the correspondence of the onset location with prominent large-scale field-aligned currents and electrojets are investigated. Solar illumination and the related ionospheric conductivity have significant effects on the most probable substorm onset latitude and local time. In sunlight, substorm onsets tend to occur 1h earlier in local time and 1.5° more poleward than in darkness. The solar wind input, represented by the merging electric field, integrated over 1h prior to the substorm, correlates well with the latitude of the breakup. Most poleward latitudes of the onsets are found to range around 73° magnetic latitude during very quiet times. Field-aligned and Hall currents observed concurrently with the onset are consistent with the signature of a westward travelling surge evolving out of the Harang discontinuity. The observations suggest that the ionospheric conductivity has an influence on the location of the precipitating energetic electron which causes the auroral break-up signature. Keywords. Ionosphere (Auroral ionosphere) – Magnetospheric Physics (Current systems; Magnetosphereionosphere interactions)

scholarly journals Variations of flow direction in solar wind streams of different types

2021 ◽  
Vol 7 (4) ◽  
pp. 10-18
Author(s):  
Anastasiya Moskaleva ◽  
Mariya Ryazanceva ◽  
Yuriy Ermolaev ◽  
Irina Lodkina
Keyword(s):  
Solar Wind ◽  
High Speed ◽  
Large Scale ◽  
Weather Forecasting ◽  
Flow Direction ◽  
Coronal Holes ◽  
Wind Flow ◽  
Different Types ◽  
Solar Wind Flow ◽  
Spacecraft Data

Studying the direction of the solar wind flow is a topical problem of space weather forecasting. As a rule, the quiet and uniform solar wind propagates radially, but significant changes in the solar wind flow direction can be observed, for example, in compression regions before the interplanetary coronal mass ejections (Sheath) and Corotating Interaction Regions (CIR) that precede high-speed streams from coronal holes. In this study, we perform a statistical analysis of the longitude (φ) and latitude (θ) flow direction angles and their variations on different time scales (30 s and 3600 s) in solar wind large-scale streams of different types, using WIND spacecraft data. We also examine the relationships of the value and standard deviations SD of the flow direction angles with various solar wind parameters, regardless of the solar wind type. We have established that maximum values of longitude and latitude angle modulus, as well as their variations, are observed for Sheath, CIR, and Rare, with the probability of large deviations from the radial direction (>5°) increasing. The dependence on the solar wind type is shown to decrease with scale. We have also found that the probability of large values of SD(θ) and SD(φ) increases with increasing proton temperature (Tp) in the range 5–10 eV and with increasing proton velocity (Vp) in the range 400–500 km/s.

scholarly journals Cluster survey of the mid-altitude cusp – Part 2: Large-scale morphology

2009 ◽  
Vol 27 (5) ◽  
pp. 1875-1886 ◽  
Author(s):  
F. Pitout ◽  
C. P. Escoubet ◽  
B. Klecker ◽  
I. Dandouras
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Time Delay ◽  
Large Scale ◽  
Statistical Study ◽  
Proper Time ◽  
A Priori ◽  
Scale Morphology ◽  
External Conditions ◽  
Cluster Ion

Abstract. In this second part of our statistical study of the mid-altitude cusp, we compare the cusp morphology, as seen in the Cluster ion spectrometer (CIS), to the interplanetary magnetic field (IMF) orientation. We first recall the method we have used a) to define the cusp properties, b) to sort IMF conditions or behaviour in classes, c) to determine the proper time delay between the solar wind monitors and Cluster. Then, we define a few morphological features of the cusp and we relate these to the prevailing IMF. Our results reveal, among other things, that the occurrence of clearly dispersed ion structures in the cusp is 48%. From these dispersions, we infer the distance to reconnection site, which we relate to external conditions. In all other cases, the cusp exhibits a more disturbed behaviour in terms of ion structures and fall in our "discontinuous" or "irregular" categories. Among these, a few interesting cases of discontinuous cusps occurring under stable IMF conditions have been identified. They all occur when the IMF is dominated by its Y-component, which plays in principle in favour of anti-parallel reconnection but their wide MLT and latitudinal distributions is a priori incompatible with the anti-parallel reconnection hypothesis solely.

Magnetic fields and charged particles around major planets and their satellites

1981 ◽  
Vol 303 (1477) ◽  
pp. 247-260 ◽  
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Small Volume ◽  
Magnetic Moments ◽  
Charged Particles ◽  
The Moon ◽  
Planetary Rotation ◽  
Spacecraft Data ◽  
Insight Into

Jupiter and Saturn have magnetospheres whose large-scale structure can be understood by analogy with Earth, but the ways in which the magnetospheres differ are of great interest. At Earth, large-scale processes are dominated by convective plasma flows driven by the solar wind. At Jupiter, centrifugal effects driven by planetary rotation are critical. Magnetosphere particle sources include not only the ionosphere and the solar wind (as at Earth) but also satellites and rings. The internal planetary magnetic moments that control the scale of the magnetosphere differ by orders of magnitude between Jupiter and Earth. The magnetic moments have been modelled from spacecraft data but the restricted spatial sampling biases the results and limits confidence in details of the models. Because Jupiter is the only accessible protostar, it serves as a laboratory to test how well inferences from ground-based observations accord with in situ measurements. The agreement in some cases examined is reassuringly good but remote observations probe less than 0.1 % of the magnetospheric volume. Within that small volume, strong currents couple the moon lo with Jupiter s ionosphere. Voyager data give new insight into the lo story and suggest that lo may itself be magnetized and surrounded by an entirely unfamiliar type of magnetosphere.

scholarly journals Variations of flow direction in solar wind streams of different types

2021 ◽  
Vol 7 (4) ◽  
pp. 10-17
Author(s):  
Anastasiya Moskaleva ◽  
Mariya Ryazanceva ◽  
Yuriy Ermolaev ◽  
Irina Lodkina
Keyword(s):  
Solar Wind ◽  
High Speed ◽  
Large Scale ◽  
Weather Forecasting ◽  
Flow Direction ◽  
Coronal Holes ◽  
Wind Flow ◽  
Different Types ◽  
Solar Wind Flow ◽  
Spacecraft Data

Studying the direction of the solar wind flow is a topical problem of space weather forecasting. As a rule, the quiet and uniform solar wind propagates radially, but significant changes in the solar wind flow direction can be observed, for example, in compression regions before the interplanetary coronal mass ejections (Sheath) and Corotating Interaction Regions (CIR) that precede high-speed streams from coronal holes. In this study, we perform a statistical analysis of the longitude (φ) and latitude (θ) flow direction angles and their variations on different time scales (30 s and 3600 s) in solar wind large-scale streams of different types, using WIND spacecraft data. We also examine the relationships of the value and standard deviations SD of the flow direction angles with various solar wind parameters, regardless of the solar wind type. We have established that maximum values of longitude and latitude angle modulus, as well as their variations, are observed for Sheath, CIR, and Rare, with the probability of large deviations from the radial direction (>5°) increasing. The dependence on the solar wind type is shown to decrease with scale. We have also found that the probability of large values of SD(θ) and SD(φ) increases with increasing proton temperature (Tp) in the range 5–10 eV and with increasing proton velocity (Vp) in the range 400–500 km/s.

Sign in / Sign up

Export Citation Format

Share Document