Hannes Karl Leinweber

University of California, Los Angeles | UCLA · ESS\IGPP

We present a statistical study of coherent structures at kinetic scales, using data from the Magnetospheric Multiscale mission in the Earth's magnetosheath. We implemented the multi-spacecraft partial variance of increments (PVI) technique to detect these structures, which are associated with intermittency at kinetic scales. We examine the properti...

We report the observations of an electron vortex magnetic hole corresponding to a new type of coherent structures in the magnetosheath turbulent plasma using the Magnetospheric Multiscale (MMS) mission data. The magnetic hole is characterized by a magnetic depression, a density peak, a total electron temperature increase (with a parallel temperatur...

In this letter, first observations of ion-scale magnetic island from the Magnetospheric Multiscale mission in the magnetosheath turbulent plasma are presented. The magnetic island is characterized by bipolar variation of magnetic fields with magnetic field compression, strong core field, density depletion, and strong currents dominated by the paral...

Dipolarization fronts (DFs), embedded in bursty bulk flows (BBFs), play a crucial role in Earth's plasmasheet dynamics because the energy input from the solar wind is partly dissipated in their vicinity. This dissipation is in the form of strong low-frequency waves that can heat and accelerate energetic electrons up to the high latitude plasmasheet...

Surface waves at the magnetopause flanks typically feature steeper, i.e., more inclined leading (antisunward facing) than trailing (sunward facing) edges. This is expected for Kelvin-Helmholtz instability (KHI) amplified waves. Very rarely, during northward interplanetary magnetic field (IMF) conditions, anomalous/inverse steepening has been observ...

We present Magnetospheric Multiscale (MMS) mission measurements during a full magnetopause crossing associated with an enhanced southward ion flow. A quasi-steady magnetospheric whistler mode wave emission propagating toward the reconnection region with quasi-parallel and oblique wave angles is detected just before the opening of the magnetic field...

We present a statistical study of dipolarization fronts (DFs), using magnetic field data from MMS and Cluster, at radial distances below 12 R E and 20 R E , respectively. Assuming that the DFs have a semicircular cross section and are propelled by the magnetic tension force, we used multispacecraft observations to determine the DF velocities. About...

Supporting Information S1

Data Set S1

We report on field-aligned current observations by the four Magnetospheric Multiscale (MMS) spacecraft near the plasma sheet boundary layer (PSBL) during two major substorms on 23 June 2015. Small-scale field-aligned currents were found embedded in fluctuating PSBL flux tubes near the separatrix region. We resolve, for the first time, short-lived e...

Supporting Information S1

Multipoint measurements are a powerful method in studying wavefields in space plasmas. The wave telescope technique is tested against magnetic field fluctuations in the terrestrial magnetosheath measured by the four Magnetospheric Multiscale (MMS) spacecraft on a spatial scale of about 20 km. The dispersion relation diagram and the wave vector dist...

We present multi-mission observations of field-aligned currents, auroral oval, and magnetopause crossings during the March 17, 2015 magnetic storm. Dayside reconnection is expected to transport magnetic flux, strengthen field-aligned currents, lead to polar cap expansion and magnetopause erosion. Our multi-mission observations assemble evidence for...

The FIELDS instrumentation suite on the Magnetospheric Multiscale (MMS) mission provides comprehensive measurements of the full vector magnetic and electric fields in the reconnection regions investigated by MMS, including the dayside magnetopause and the night-side magnetotail acceleration regions out to 25 Re. Six sensors on each of the four MMS...

Spin-stabilization of spacecraft immensely supports the in-flight calibration of on-board flux-gate magnetometers (FGMs). From 12 calibration parameters in total, 8 can be easily obtained by spectral analysis. From the remaining 4, the spin axis offset is known to be particularly variable. It is usually determined by analysis of Alfvénic fluctuatio...

The success of the Magnetospheric Multiscale mission depends on the accurate measurement of the magnetic field on all four spacecraft. To ensure this success, two independently designed and built fluxgate magnetometers were developed, avoiding single-point failures. The magnetometers were dubbed the digital fluxgate (DFG), which uses an ASIC implem...

Ion cyclotron waves (ICWs) are generated during the interaction between the solar wind and the Martian exosphere in a process called ion pick-up. Mars Global Surveyor (MGS) detected waves near the proton gyro-frequency, indicating pickup of the exospheric hydrogen. To analyze these waves, we first improve the zero levels of the MGS magnetic field d...

Hannes K. Leinweber , Christopher T. Russell , and Klaus Torkar In certain regions of the Earth's magnetosphere the divergence and the curl of the magnetic field are vanishingly small. Four spacecraft that fly across such a region in a tetrahedron configuration may not observe vanishingly small divergence and curl of the magnetic field. This can be...

Electrical activity in a planetary atmosphere enables chemical reactions that are not possible under con-ditions of local thermodynamic equilibrium. In both the Venus and terrestrial atmospheres, lightning forms nitric oxide. Despite the existence of an inventory of NO at Venus like the Earth's, and despite observations of the signals expected from...

Terrestrial lightning generates a broad spectrum of electromagnetic energy from near 1 Hz (ULF) to MHz (Radio Frequencies). Recently we have been able to clean the spacecraft noise from the Venus Express magnetometer and extend the bandwidth of signal detected down to below 1 Hz. We find that on Venus also, the noise spectrum of electrical activity...

ULF waves below 10 Hz in Venus' ionosphere allow the rate of lightning to be measured.

We show that the spin axis offset of a fluxgate magnetometer can be calibrated with an electron drift instrument (EDI) and that the required input time interval is relatively short. For missions such as Cluster or the upcoming Magnetospheric Multiscale (MMS) mission the spin axis offset of a fluxgate magnetometer could be determined on an orbital b...

The observations of electromagnetic signals from 0 to 64 Hz using the two fluxgate magnetometers on Venus Express have been enabled by new, improved cleaning algorithms. These data reveal two types of signals that are associated with electrical activity in Venus' atmosphere. The first signals occur below about 20 Hz, where signals can propagate per...

The magnetometer on the Venus Express mission can sample at 128 Hz allowing the detection of whistler mode signals in the Venus ionosphere. Strong signals (~1 nT peak-to-peak) are observed at the lowest altitudes. These signals are right-handed and nearly circularly polarized as expected from lightning. Their occurrence is controlled by the directi...

The magnetometer on the Venus Express mission can sample at 128 Hz allowing the detection of whistler mode signals in the Venus ionosphere. Strong signals (~1 nT peak-to-peak) are observed at the lowest altitudes. These signals are right-handed and nearly circularly polarized as expected from lightning. Their occurrence is controlled by the directi...

Whistler mode signals produced by lightning have a distinct falling tone at the Earth. Venus whistler mode signals in the ionosphere has a similar "dispersion" consistent with their shorter travel path.

Jupiter's outer magnetospheric current sheet has been shown to have a local time asymmetry where the sheet is thin on the dawn side and thick at dusk. Specifically, magnetic field observations from Galileo in the rotational equator show that the spacecraft clearly moved from a lobe with strong magnetic field, through the thin sheet, where the field...

moment during the Galileo epoch was 4.334 ± 0.010 Gauss RJ 3 or 1.584 ± 0.004 × 10 20 Tm 3 . The tilt angle of the dipole was 9.71° ± 0.05°. We examine both the change in the magnetic field during the period in which Galileo operated in Jovian orbit and the change in the field between the initial observations with Pioneer 11 and the Galileo epoch....

Previously unmodeled Galileo magnetic measurements, obtained interior to Io, are examined to determine their suitability for extending the modeled field to higher orders and to compare with Pioneer 11 measurements to constrain the secular variation.

The jovian magnetic field has been probed by five flyby missions (Pioneer 10 and 11, Voyager 1 and 2, and Ulysses), and from 1995 - 2003 by the Galileo orbiter. We invert these data using the same technique to obtain a uniform-quality, robust estimate of seven coefficients of the jovian field over a quarter century. We use two Earth-flybys to valid...

The in-flight determination of magnetometer zero levels is an important step of the overall calibration procedure, especially if the field to be measured is weak. In low- field regions within a magnetosphere the precision of magnetic field models is insufficient for calibration purposes. If a magnetometer has erroneous zero levels a pure change of...

The THEMIS Fluxgate Magnetometer (FGM) measures the background magnetic field and its low frequency fluctuations (up to 64 Hz) in the near-Earth space. The FGM is capable of detecting variations of the magnetic field with amplitudes of 0.01 nT, and it is particularly designed to study abrupt reconfigurations of the Earth’s magnetosphere during the...

1] The magnetotails of Jupiter and Earth are known to be hinged so that their orientation is controlled by the magnetic field of the planet at small distances and asymptotically approach the direction of the flow of the solar wind at large distances. In this paper we present Cassini observations showing that Saturn's magnetosphere is also similarly...

For a magnetometer that measures weak interplanetary fields, the in-flight determination of zero levels is a crucial step of the overall calibration procedure. This task is more difficult when a time-varying magnetic field of the spacecraft interferes with the surrounding natural magnetic field or when the spacecraft spends only short periods of ti...

Venus has no significant internal magnetic field, which allows the solar wind to interact directly with its atmosphere. A field is induced in this interaction, which partially shields the atmosphere, but we have no knowledge of how effective that shield is at solar minimum. (Our current knowledge of the solar wind interaction with Venus is derived...

For a magnetometer that measures weak interplanetary fields, the in-flight determination of zero levels is a crucial step of the overall calibration procedure. This task is more difficult when a time varying magnetic field of the spacecraft interferes with the surrounding natural magnetic field or when the spacecraft only spends short periods of ti...

1] Solar wind magnetometer and plasma data and magnetometer data acquired by Cluster in the magnetospheric plasma sheet are employed to construct probability distribution functions (PDFs) of magnetic field fluctuations over various temporal and spatial scales. This technique, often used in analysis of laboratory plasmas, is used to look for intermi...

Cassini continues to provide exciting new observations from the magnetosphere of Saturn. These observations are helping us understand the structure and dynamics of Saturn's magnetosphere. The observations are also helping us construct a versatile new model of Saturn's magnetospheric field for use in future data analysis. Our model consists of modul...

We have developed a new and highly automated technique for determining the thickness of Jupiter's current sheet from magnetic field data over all local times and radial distances. The technique determines current sheet thickness by fitting a Harris neutral sheet description to the observations. The four parameters required for the fits are the lobe...

In order to estimate the dissipation time-scale in magnetic turbulence in the plasma sheet a novel method is introduced for classification of velocity dependent patterns of two-point probability density functions' shapes near their maxima. For the first time, we provide evidence for Reynolds number (velocity) dependent widening of the inertial rang...

1] Jupiter's magnetosphere contains a gigantic sheet-like structure located near its dipole magnetic equator that contains most of the plasma and energetic particles swirling in Jupiter's magnetosphere. Called the ''current sheet,'' it behaves like a rigid structure inside a radial distance of $50 R J where the periodic reversals of the B r compone...

1] Cluster fluxgate magnetometer (FGM) and ion spectrometer (CIS) data are employed to analyze magnetic field fluctuations within the plasma sheet during passages through the magnetotail region in the summers of 2001 and 2002 and, in particular, to look for characteristics of magnetohydrodynamic (MHD) turbulence. Power spectral indices determined f...

Mirror modes waves are commonly observed in planetary magnetosheaths, cometary sheaths, and other plasmas with anisotropic pressure distributions. In this paper we present results derived from observations from many spacecraft that have sampled the Jovian magnetosheath over a wide range of radial distances and local times (Pioneer 10 & 11, Voyager...

Solar wind magnetometer and plasma data and magnetometer data acquired by Cluster in the magnetospheric plasma sheet are employed to construct probability distribution functions (PDFs) of velocity fluctuations and magnetic field fluctuations over various temporal and spatial scales. This technique, often used in analysis of laboratory plasmas, is u...

The six spacecraft that have traveled through the magnetosphere of Jupiter have encountered Jupiter's current sheet over all local times and varying solar wind ram directions. We use magnetic field data from these spacecraft and new techniques to determine the prime longitude (the system III direction in which the current sheet has its highest elev...

Cluster fluxgate magnetometer data and ion spectroscopic data are employed to construct and interpret scaling exponential functions and intermittency coefficients for magnetic field fluctuations. This technique, often used in analysis of space and laboratory plasmas, is used to look for intermittent plasma turbulence. Our results show non-self simi...

The calculation of spatial magnetic field gradients requires the determination of orientations, zero levels and scale factors (calibration parameters) of all four CLUSTER magnetometers with very high accuracy (48 parameters, overall). This daunting task is made easier by natural constraints imposed on geophysical signals by nature. For example by o...

Global magnetic field models are required to interpret field and plasma observations collected by Galileo in Jupiter's magnetosphere. Accurate models would also be needed to define the changing magnetic field in the rest frames of the icy satellites for the JIMO mission. Previous models have been inadequate because of simplifying assumptions or ina...

Cluster fluxgate magnetometer (FGM) data are employed to examine the turbulent nature of magnetic field fluctuations within the plasma sheet during Cluster's passages through the magnetotail region in the summers of 2001 and 2002. Power spectral indices determined from power spectral density functions are on average larger than the Kolmogorov theor...

In this work we present observations of geomagnetic micropulsations recorded on the Earth's surface using fluxgate magnetometers designed by the University of California, Los Angeles. The pulsations were measured during the passage of 17 solar wind structures related to interplanetary coronal mass ejections. We searched for micropulsations before t...