AUTHOREA
Log in Sign Up Browse Preprints
LOG IN SIGN UP

711 solar system physics Preprints

Related keywords
solar system physics planetology geophysics aurora ionosphere climatology (global change) magnetospheric particles numerical modelling precipitation physics solar physics radioastronomy the sun space plasma physics planetary magnetic fields interplanetary physics geodesy paleontology solar wind planetary physics geography informatics atmospheric sciences
FOLLOW
  • Email alerts
  • RSS feed
Please note: These are preprints and have not been peer reviewed. Data may be preliminary.
Outer Radiation Belt Flux and Phase Space Density Response to Sheath Regions: Van All...
Milla M. H. Kalliokoski
Michael G. Henderson

Milla M. H. Kalliokoski

and 11 more

June 07, 2022
Turbulent and compressed sheath regions preceding interplanetary coronal mass ejections (ICMEs) strongly impact electron dynamics in the outer radiation belt. Changes in electron flux can occur on timescales of tens of minutes, which is difficult to capture by a two-satellite mission such as the Van Allen Probes (RBSP). The recently released Global Positioning System (GPS) data set has higher data density owing to the large number of satellites in the constellation equipped with energetic particle detectors. Investigating electron fluxes in a wide range of energies and sheaths observed from 2012 to 2018, we show that the flux response to sheaths on a timescale of 6 hours, previously reported from RBSP data, is reproduced by GPS measurements. Furthermore, GPS data enables derivation of the response on a shorter timescale of 30 minutes, which further confirms that the energy and L-shell dependent changes in electron flux are due to the impact of the sheath. Sheath-driven loss is underestimated over longer timescales as the electrons recover during the ejecta. We additionally show the response of electron phase space density (PSD), which is a key quantity in identifying true loss from the system and electron energization through wave-particle interactions. The PSD response is calculated from both RBSP and GPS data for the 6-hour timescale, as well as from GPS data for the 30-minute timescale. The response is divided based on the geoeffectiveness of the sheaths revealing that electrons are effectively accelerated only during geoeffective sheaths, while loss is commonly caused by all sheaths.
Rapid Auroral Wandering During the Laschamps Event
Agnit Mukhopadhyay
Sanja Panovska

Agnit Mukhopadhyay

and 6 more

December 09, 2021
41 thousand years ago, the Laschamps geomagnetic excursion caused Earth’s geomagnetic field to drastically diminish to ~4% of modern values and modified the geomagnetic dipole axis. While the impact of this geomagnetic event on environmental factors and human lifestyle has been contemplated to be linked with modifications in the geospace environment, no concerted investigation has been conducted to study this until recently. We present an initial investigation of the global space environment and related plasma environments during the several phases of the Lachamps event using an advanced multi-model approach. We use recent paleomagnetic field models of this event to study the paleomagnetosphere with help of the global magnetohydrodynamic model BATS-R-US. Here we go beyond a simple dipole approximation but consider a realistic geomagnetic field configuration. The field is used within BATS-R-US to generate the magnetosphere during discrete epochs spanning the peak of the event. Since solar conditions have remained fairly constant over the last ~100k years, modern estimates of the solar wind were used to drive the model. Finally, plasma pressure and currents generated by BATS-R-US at their inner boundary are used to compute auroral fluxes using a stand-alone version of the MAGNIT model, an adiabatic kinetic model of the aurora. Our results show that changes in the geomagnetic field, both in strength and the dipole tilt angle, have profound effects on the space environment and the ensuing auroral pattern. Magnetopause distances during the deepest phase of the excursion match previous predictions by studies like Cooper et al. (2021), while high-resolution mapping of magnetic fields allow close examination of magnetospheric structure for non-dipolar configurations. Temporal progression of the event also exhibits rapid locomotion of the auroral region over ~250 years along with the movement of the geomagnetic poles. Our estimates suggest that the aurora extended further down, with the center of the oval located at near-equatorial latitudes during the peak of the event. While the study does not find evidence of any link between geomagnetic variability and habitability conditions, geographic locations of the auroral oval coincide with early human activity in the Iberian peninsula and South China Sea.
From the top of Martian Olympus to Deep Craters and Beneath: Mars Radiation Environme...
Jingnan Guo
Jian Zhang

Jingnan Guo

and 4 more

December 16, 2021
In preparation for future human habitats on Mars, it is important to understand the Martian radiation environment. Mars does not have an intrinsic magnetic field and Galactic cosmic ray (GCR) particles may directly propagate through and interact with its atmosphere before reaching the surface and subsurface of Mars. However, Mars has many high mountains and low-altitude craters where the atmospheric thickness can be more than 10 times different from one another. We thus consider the influence of the atmospheric depths on the Martian radiation levels including the absorbed dose, dose equivalent and body effective dose rates induced by GCRs at varying heights above and below the Martian surface. The state-of-the-art Atmospheric Radiation Interaction Simulator (AtRIS) based on GEometry And Tracking (GEANT4) Monte Carlo method has been employed for simulating particle interactions with the Martian atmosphere and terrain. We find that higher surface pressures can effectively reduce the heavy ion contribution to the radiation, especially the biologically weighted radiation quantity. However, enhanced shielding (both by the atmosphere and the subsurface material) can considerably enhance the production of secondary neutrons which contribute significantly to the effective dose. In fact, both neutron flux and effective dose peak at around 30 cm below the surface. This is a critical concern when using the Martian surface material to mitigate radiation risks. Based on the calculated effective dose, we finally estimate some optimized shielding depths, under different surface pressures (corresponding to different altitudes) and various heliospheric modulation conditions. This may serve for designing future Martian habitats.
Quantifying the effect of ICME removal and observation age for in situ solar wind dat...
Harriet Turner
Mathew J Owens

Harriet Turner

and 4 more

March 31, 2022
Accurate space weather forecasting requires advanced knowledge of the solar wind conditions in near-Earth space. Data assimilation (DA) combines model output and observations to find an optimum estimation of reality and has led to large advances in terrestrial weather forecasting. It is now being applied to space weather forecasting. Here, we use solar wind DA with in-situ observations to reconstruct solar wind speed in the ecliptic plane between 30 solar radii and Earth’s orbital radius. This is used to provide solar wind speed hindcasts. Here, we assimilate observations from the Solar Terrestrial Relations Observatory (STEREO) and the near-Earth dataset, OMNI. Analysis of two periods of time, one in solar minimum and one in solar maximum, reveals that assimilating observations from multiple spacecraft provides a more accurate forecast than using any one spacecraft individually. The age of the observations also has a significant impact on forecast error, whereby the mean absolute error (MAE) sharply increases by up to 23% when the forecast lead time first exceeds the corotation time associated with the longitudinal separation between the observing spacecraft and the forecast location. It was also found that removing coronal mass ejections from the DA input and verification time series reduces the forecast MAE by up to 10% as it removes false streams from the forecast time series. This work highlights the importance of an L5 space weather monitoring mission for near-Earth solar wind forecasting and suggests that an additional mission to L4 would further improve future solar wind DA forecasting capabilities.
Sources of Auroral Conductance - Balance and Impacts
Agnit Mukhopadhyay
Daniel Welling

Agnit Mukhopadhyay

and 8 more

December 09, 2021
Despite significant developments in global modeling, the determination of ionospheric conductance in the auroral region remains a challenge in the space science community. With advances in adiabatic kinetic theory and numerical couplings between global magnetohydrodynamic models and ring current models, the dynamic prediction of individual sources of auroral conductance have improved significantly. However, the individual impact of these sources on the total conductance and ionospheric electrodynamics remains understudied. In this study, we have investigated individual contributions from four types of auroral precipitation - electron & ion diffuse, monoenergetic & Alfven wave-driven - on ionospheric electrodynamics using a novel modeling setup. The setup encompasses recent developments within the University of Michigan’s Space Weather Modeling Framework (SWMF), specifically through the use of the MAGNetosphere - Ionosphere - Thermosphere auroral precipitation model and dynamic two-way coupling with the Global Ionosphere-Thermosphere Model. This modeling setup replaces the empirical idealizations traditionally used to estimate conductance in SWMF, with a physics-based approach capable of resolving 3-D high-resolution mesoscale features in the ionosphere-thermosphere system. Using this setup, we have simulated an idealized case of southward Bz 5nT & the April 5-7 “Galaxy15” Event. Contributions from each source of precipitation are compared against the OVATION Prime Model, while auroral patterns and hemispheric power during Galaxy15 are compared against observations from DMSP SSUSI and the AE-based FTA model. Additionally, comparison of field aligned currents (FACs) and potential patterns are also conducted against AMPERE, SuperDARN & AMIE estimations. Progressively applying conductance sources, we find that diffuse contributions from ions and electrons provide ~75% of the total energy flux and Hall conductance in the auroral region. Despite this, we find that Region 2 FACs increase by ~11% & cross-polar potential reduces by ~8.5% with the addition of monoenergetic and broadband sources, compared to <1% change in potential for diffuse additions to the conductance. Results also indicate a dominant impact of ring current on the strength and morphology of the precipitation pattern.
Solar Cycle Variation of Suprathermal Heavy Ion Composition and Spectra during Quiet...
Benjamin Alterman
Mihir Desai

Benjamin Alterman

and 4 more

December 09, 2021
We report on the annual variation of quiet-time suprathermal ion composition and spectral properties for C-Fe using Advanced Composition Explorer (ACE)/Ultra-Low Energy Ion Spectrometer (ULEIS) over the energy range 0.3 MeV/nuc to 1.28 MeV/nuc from 1998 through 2020. This extends the work of Desai et al. (2006) and Dayeh et al. (2009, 2017) to cover Solar Cycle 23’s rising phase through Solar Cycle 24’s declining phase. With 5 additional years of data, we show that the number of quiet-time hours strongly anti-correlates with the Sunspot Number (SSN) at better than the -0.9 level. We also show (1) a clear ordering of the cross correlation between abundance (normalized to O) and SSN as a function of solar wind M/Q; (2) the slope of X/O’s abundance as a function of Fe/C decreases with increasing M/Q; and (3) discuss the trend of annual spectral indicies with respect to Oxygen’s spectral index as a function of solar cycle and M/Q. The contrast between our abundance and spectral index results suggests that the source from which suprathermal ions are drawn or accelerated varies with solar activity and is tied to each element’s chemistry, but he acceleration mechanism that governs the spectral shape does not.
Identifying Exoplanets’ Potentiality for Life in Habitable Zones: Giving New Dimensio...
Koena Maji
Anuj Soni

Koena Maji

and 1 more

May 31, 2022
The discovery of exoplanets has altered our understanding of the universe. But, for the planets to show the possibility to harbour life in it or have biosignatures, it must have optimum physical, biological, geological and chemical conditions. There are two types of indicators of habitability: direct and indirect. The former indication is the presence of water and its stability on the surface of the planet. Thus, the reflection from the waterbody will lead to ‘glint’. Polarization of light is another alternative method to find water. The reflection, emission of radiation help us to characterize habitable zones. Indirect methods include the presence of CO2 and water vapour in the atmosphere, size of the planet and extent of axial tilt. The presence of magnetic fields and satellites revolving around the planet also play an important role. In this review article, we aim to provide a comprehensive explanation to the researches done till date to characterize habitable zones for exoplanets. The methods devised to retrieve results will also be discussed. Future prospects, the voids which could be amended are also elaborated. This could give cosmological research a new dimension, demonstrating that life is not limited to our planet.
The influence of magnetic field topology and orientation on the 1 distribution of the...
Murti Nauth
Christopher Fowler

Murti Nauth

and 6 more

September 04, 2020
Thermal (<1 eV) electron density measurements, derived from the Mars Atmosphere and Volatile Evolution’s (MAVEN) Langmuir Probe and Waves (LPW) instrument, are analyzed to produce the first statistical study of the thermal electron population in the Martian magnetotail. Coincident measurements of the local magnetic field are used to demonstrate that close to Mars, the thermal electron population is most likely to be observed at a cylindrical distance of ~1.1 Mars radii (Rm) from the central tail region during times when the magnetic field flares inward toward the central tail, compared to ~1.3 Rm during times when the magnetic field flares outward away from the central tail. Similar patterns are observed further down the magnetotail with greater variability. Thermal electron densities are highly variable throughout the magnetotail; average densities are typically ~20-50 /cc within the optical shadow of Mars and can peak at ~100 /cc just outside of the optical shadow. Standard deviations of 100% are observed for average densities measured throughout the tail. Analysis of the local magnetic field topology suggests that thermal electrons observed within the optical shadow of Mars are likely sourced from the nightside ionosphere, whereas electrons observed just outside of the optical shadow are likely sourced from the dayside ionosphere. Finally, thermal electrons within the optical shadow of Mars are up to 20% more likely to be observed when the strongest crustal magnetic fields point sunward than when they point tailward.
Charge State Calculation for Global Solar Wind Modeling
Judit Szente
Enrico Landi

Judit Szente

and 2 more

November 09, 2021
The charge state composition of the solar wind carries information about the electron temperature, density, and velocity of plasma in the solar corona that cannot always be measured with remote sensing techniques, due to limitations in instrumental sensitivity and field of view as well as line of sight integration issues. However, in-situ measurements of the wind charge state distribution only provides the end result of the solar wind evolution from the source region to the freeze-in point. By using 3D global modeling it is possible to follow solar wind plasma parcels of different origin along the path of their journey and study the evolution of their charge states as well as the driving physical processes. For this purpose, we implemented non-equilibrium ionization calculations within the Space Weather Modeling Framework’s Solar Corona and Inner Heliosphere modules, to the Alfvén Wave Solar Model (SWMF/AWSoM). The charge state calculations are carried out parallel to the AWSoM calculations, including all the elements and ions whose ionization-recombination rates are included in the CHIANTI database, namely from H to Zn. In this work, we describe the implementation of the charge state calculation, and compare simulation results to in-situ measurements from the ACE and Ulysses spacecraft, and study charge state evolution of plasma parcels along different wind trajectories and wind types.
The gravity signal of Mercury's inner core
Mathieu Dumberry

Mathieu Dumberry

February 28, 2022
In a reference frame rotating with Mercury’s mantle and crust, the inner core and fluid core precess in a retrograde sense with a period of 58.646 days. The precession of a triaxial inner core with a different density than the fluid core induces a periodic gravity variation of degree 2, order 1. Elastic deformations from the pressure that the precessing fluid core exerts on the core mantle boundary also contribute to this gravity signal. We show that the periodic change in Stokes coefficients ΔC21 and ΔS21 for this signal of internal origin is of the order of 10^{-10}, similar in magnitude to the signal from solar tides. The relative contribution from the inner core increases with inner core radius and with the amplitude of its tilt angle with respect to the mantle. The latter depends on the strength of electromagnetic coupling at the inner core boundary which in turn depends on the radial magnetic field B_r; a larger B_r generates a larger tilt. The inner core signal features a contrast between ΔC21 and ΔS21 due to its triaxial shape, discernible for an inner core radius >500 km if B_r>0.1 mT, or for an inner core radius >1100 km if B_r<0.01 mT. A detection of this contrast would confirm the presence of an inner core and place constraints on its size and the strength of the internal magnetic field. These would provide key constraints for the thermal evolution of Mercury and for its dynamo mechanism.
Bremsstrahlung in High Density Mediums
Yucemoz Mert

Mert Yucemoz

February 28, 2022
Previously the radiation patterns of combined parallel and perpendicular motions from the accelerated relativistic particle at low and high frequencies of the bremsstrahlung process with an external lightning electric field were explained. The primary outcome was that radiation patterns have four relative maxima with two forward peaking and two backward peaking lobes. The asymmetry of the radiation pattern, i.e., the different intensities of forwarding and backward peaking lobes, is caused by the Doppler effect. A novel outcome is that bremsstrahlung has an asymmetry of the four maxima around the velocity vector caused by the curvature of the particle's trajectory as it emits radiation. This extended work reports another novel asymmetry in the overall radiation pattern. Previously stated bremsstrahlung asymmetry, R was an asymmetry in the radiation lobe pairs about particles velocity vector. Bremsstrahlung asymmetry used to occur at the same level in both forward radiation lobe pairs and backward radiation lobe pairs. However, in high-density mediums where the emitted wave can lag behind the speed of the particle, symmetry of the magnitude of bremsstrahlung asymmetry, R differs between forward peaking radiation lobe pairs relative to backward peaking radiation lobe pairs. This is another novel asymmetry and it causes bremsstrahlung asymmetry, R to be larger in the forward peaking compared to backward peaking radiation. The outcome is the shrink in radiation length that occurs in the backward peaking lobes. This extended mathematical modeling of the bremsstrahlung process into different high-density mediums helps to better understand the physical processes of a single particle's radiation pattern, which might assist the interpretation of observations with networks of radio receivers and arrays of gamma-ray detectors.
Field Line Resonances in Jupiter's Magnetosphere
Robert L. Lysak
Yan Song

Robert L. Lysak

and 1 more

June 26, 2020
The arrival of the Juno satellite at Jupiter has led to an increased interest in the dynamics of the Jovian magnetosphere. Jupiter’s auroral emissions often exhibit quasi-periodic oscillations with periods of tens of minutes. Magnetic observations indicate that ultra-low-frequency (ULF) waves with similar periods are often seen in data from Galileo and other satellites traversing the Jovian magnetosphere. Such waves can be associated with field line resonances, which are standing shear Alfvén waves on the field lines. Using model magnetic fields and plasma distributions, the frequencies of field line resonances and their harmonics on field lines connecting to the main auroral oval have been determined. Time domain simulations of Alfvén wave propagation have illustrated the evolution of such resonances. These studies indicate that harmonics of the field line resonances are common in the 10-40 minute band.
Quantifying the size and duration of a microburst-producing chorus region on 5 Decemb...
Sadie Suzanne Elliott
Aaron Breneman

Sadie Suzanne Elliott

and 19 more

June 03, 2022
Microbursts are impulsive (<1s) injections of electrons (few keV to >MeV) from the outer radiation belt into the atmosphere, primarily caused by nonlinear scattering by chorus waves. Although attempts have been made to quantify their contribution to outer belt electron loss, the uncertainty in the overall size and duration of the microburst region is typically large, so that their contribution to outer belt loss is uncertain. We combine datasets that measure chorus waves (Van Allen Probes (RBSP), Arase, ground-based VLF stations) and microburst (>30 keV) precipitation (FIREBIRD II and AC6 CubeSats, POES/MetOp) to determine the size of the microburst-producing chorus source region beginning on 5 December 2017. We show that the lower/upper limits on the long-lasting (~30 hours) microburst precipitation region is 4 to 8 MLT and 2 to 8.5 L. We conclude that microbursts likely represent a major loss source of outer radiation belt electrons for this event.
On Constructing a Realistic Truth Model Using Ionosonde Data for Observation System S...
Joseph Hughes
Victoriya V Forsythe

Joseph Hughes

and 8 more

June 03, 2022
The ionosphere contains many small-scale electron density variations that are under represented in smooth physics-based or climatological models. This can negatively impact the results of Observation System Simulation Experiments, which use a truth model to simulate data. This paper addresses this problem by using ionosonde data to study ionospheric variability and build a new truth model with empirically-driven variations. The variations are studied for their amplitude, horizontal and vertical size, and temporal extent. Results are presented for different local times, seasons, and at two different points in the solar cycle. We find that these departures from a smooth background are often as large as 25\% and are most prevalent near 250 km in altitude. They have horizontal spatial extents that vary from a few hundred to a few thousand kilometers, and typically have the largest horizontal extent at high altitudes. Their vertical extents follow the same pattern of being larger at high altitudes, but they only vary from 10s of km up to 200 km in vertical size. Temporally, these variations can last for a few hours. The procedure for using these spatial and temporal distributions to add empirically-driven variance to a smooth truth model is outlined. This process is used to make a truth model with representative variations, which is compared to ionosonde data as well as GPS Total Electron Content (TEC) data that was not used to inform the model. The new model resembles the data much better than the smooth models traditionally used.
2024 Decadal Survey for Space and Solar Physics: Space Weather Inputs
Noé Lugaz
Jennifer Gannon

Noé Lugaz

and 5 more

June 07, 2022
The next decadal survey process for space and solar physics will start soon with white papers due during the second half of 2022 and the committees and panels working over all of 2023. Space weather science and operations will play an essential role in this survey. Therefore, the community is invited to prepare white papers and get involved in advancing space weather research and capabilities in the upcoming decades. A summary of the recommendations related to space weather from the last two decadal surveys is also provided.
Electron Microburst Size Distribution Derived with AeroCube-6
Mykhaylo Shumko
Arlo Johnson

Mykhaylo Shumko

and 8 more

November 20, 2019
Microbursts are an impulsive increase of electrons from the radiation belts into the atmosphere and have been directly observed in low Earth orbit and the upper atmosphere. Prior work has estimated that microbursts are capable of rapidly depleting the radiation belt electrons on the order of a day, hence their role to radiation belt electron losses must be considered. Losses due to microbursts are not well constrained, and more work is necessary to accurately quantify their contribution as a loss process. To address this question we present a statistical study of > 35 keV microburst sizes using the pair of AeroCube-6 CubeSats. The microburst size distribution in low Earth orbit and the magnetic equator was derived using both spacecraft. In low Earth orbit, the majority of microbursts were observed while the AeroCube-6 separation was less than a few tens of km, mostly in latitude. To account for the statistical effects of random microburst locations and sizes, Monte Carlo and analytic models were developed to test hypothesized microburst size distributions. A family of microburst size distributions were tested and a Markov Chain Monte Carlo sampler was used to estimate the optimal distribution of model parameters. Finally, a majority of observed microbursts map to sizes less then 200 km at the magnetic equator. Since microbursts are widely believed to be generated by scattering of radiation belt electrons by whistler mode waves, the observed microburst size distribution was compared to whistler mode chorus size distributions derived in prior literature.
Auroral structure and dynamics from GOLD
Robert G Michell

Robert G Michell

November 20, 2019
The Global-scale Observations of the Limb and Disk (GOLD) mission data contain significant quantitative information about the aurora on a global scale. Here we present techniques for quantifying such information, including the temporal development of the structure within the auroral oval using the GOLD images. These techniques are applied to auroral observations in the GOLD data, in particular showing an example of how the longitudinal structure within the aurora varies over the course of six consecutive days with differing levels of geomagnetic activity. A simple model of the solar-induced airglow is presented that is used to remove the sunlight contamination from the dayside auroral observations. Comparisons to ground-based auroral imaging are used for the overall auroral context and to make estimates of the proportionality between the intensities of the green-line (557.7 nm) emission in the visible and the 135.6 nm emissions in the GOLD data. These observations are consistent with the intensity of the 135.6 nm auroral emission being on the same order as the intensity of the 557.7 nm auroral emission. They were both found to be around 1 kR for a stable auroral arc on a day with low geomagnetic activity (03 November 2018) and around 10 kR for an active auroral display on a day with higher levels of geomagnetic activity (05 November 2018). This could have important implications for making direct comparisons between space-based UV auroral imaging and ground-based visible-light auroral imaging and the total energy input estimates that are derived from them.
Retrieval of Global Dust Particle Mineral Abundances from Spectroscopy
Mohammad Reza Sadrian
Wendy Calvin

Mohammad Reza Sadrian

and 1 more

January 07, 2021
Direct radiative forcing is a major impact of atmospheric dust aerosols. Mineral dust is an important aerosol component that interacts with both incoming and outgoing radiation, modulating radiative fluxes on Earth and its atmosphere. Dust radiative impact directly depends on the particles physico-chemical characteristics (e.g. mineralogy, shape, size) which are the main source of uncertainties. Spectral signatures of dust particles in the visible/short-wave infrared (V/SWIR) and long-wave infrared (LWIR) are linked to mineral composition and variability. Obtaining the precise spectral signature and size distribution of dust particles can result in accurate derivation of refractive indices which are used as inputs to model radiative forcing. In this work, V/SWIR and LWIR reflectance spectra of heterogeneous dust samples from the United States, East Asia, and Middle East were analyzed for their mineral abundances. For this study we used global well-characterized soil samples with comparable mineral compositions to windblown dust. The soil samples cover a wide range of mineral compositions and represent both arid and semi-arid regions [J P Engelbrecht et al., 2016]. Our preliminary analysis used linear spectral mixing for both V/SWIR and LWIR reflectance spectra. This approach is the simplest method to determine mineral abundances from reflectance spectra. While this resulted in a very low RMSE for the fit between the sample and modeled spectra, modeled spectra did not match band centers and strengths for all features. We also converted reflectance spectra to continuum removed (CR) and mean optical path (MOPL) which have the potential to eliminate nonlinear effects (e.g. multiple scattering) in spectral mixing. These approaches, which modify the reflectance hull, significantly weakened or removed the calcite absorption features at 2375 nm. Because these samples are very fine grained (< 38 µm [J P Engelbrecht et al., 2016]) multiple scattering effects are expected to be important for both V/SWIR and LWIR spectral ranges and as our initial results show linear mixing is insufficient to produce reasonable mineral abundances. Our next efforts will include full radiative transfer models of the measured spectra which we will present at the meeting.
Time Dependence of the Solar Rotation Rate
Roger Ulrich
John Boyden

Roger Ulrich

and 3 more

January 14, 2021
The sun is a plasma threaded variously by magnetic fields that stretch from the deep interior to the heliosphere. These fields can couple various layers together and transfer momentum between different parts of the solar interior. The sun is not a rigid body and there is no requirement from conservation of angular momentum that the overall solar rotation rate as measured at the photosphere need remain constant. At the 150-foot solar tower telescope on Mt. Wilson the Doppler shift, magnetic fields and line intensity of the solar photosphere have been measured as often as possible beginning in 1965 (1965 and 1966 were lost in a data handling mistake). The overall rotation rate is determined for each observation by fitting the observed photospheric velocities to the function ωsid(φ) =A+Bsin2(φ) +Csin4(φ) where φ is latitude, to determine what is known as the A coefficient. We are currently re-reducing all the data from the 150-foot tower system. Differential rotation is described by the B and C coefficients which we are holding constant with average values. The velocities come from Doppler shifts which with a Babcock magnetograph come mostly from the displacement of the moving sampling stage which balances the intensity in the wings of the spectral line. Line shape calibration uncertainties do not influence this shift. We find variations in the global rotation rate which are larger than the shifts known as the torsional oscillations. If the B and C coefficients are fitted to each Dopplergram the torsional oscillations become evident. Instrument changes of the exit slit system and spectrograph grating do not introduce jumps in the A coefficient. Restriction of observations to those when the sun is within 40 degrees of local noon leaves the result essentially unchanged. There may be a solar cycle influence but, the resulting pattern shown in the attached figure is more complex than that. Data from before 1983 has a scatter about 3 times larger than what is shown here with an average consistent with these results. However, the larger scatter prevents the variability from being evident.
Kinetic interaction of cold and hot protons with an oblique EMIC wave near the daysid...
Sergio Toledo-Redondo
Justin Hao Lee

Sergio Toledo-Redondo

and 23 more

January 07, 2021
We report observations of the ion dynamics inside an Alfven branch wave that propagates near the reconnecting dayside magnetopause. The measured frequency, wave normal angle and polarization are within 1% with the predictions of a dispersion solver, and indicate that the wave is an electromagnetic ion cyclotron wave with very oblique wave vector. The magnetospheric plasma contains hot protons (keV), cold protons (eV), plus some heavy ions. The cold protons follow the magnetic field fluctuations and remain frozen-in, while the hot protons are at the limit of magnetization. The cold proton velocity fluctuations contribute to balance the Hall term in Ohm’s law, allowing the wave polarization to be highly-elliptical and right-handed, a necessary condition for propagation at oblique wave normal angles. The dispersion solver indicates that increasing the cold proton density facilitates generation and propagation of these waves at oblique angles, as it occurs for the observed wave.
A Data-driven Model of the Solar Wind, Interstellar Pickup Ions, and Turbulence throu...
Tae Kim
Igor Kryukov

Tae Kim

and 4 more

April 04, 2018
The outer heliosphere is an interesting region characterized by the interaction between the solar wind and the interstellar neutral atoms. Having accomplished the mission to Pluto in 2015 and currently on the way to the Kuiper Belt, the New Horizons spacecraft is following the footsteps of the two Voyager spacecraft that previously explored this region lying roughly beyond 30 AU from the Sun. We model the three-dimensional, time-dependent solar wind plasma flow to the outer heliosphere using our own software Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS), which, in addition to the thermal solar wind plasma, takes into account charge exchange of the solar wind protons with interstellar neutral atoms and treats nonthermal ions (i.e., pickup ions) born during this process as a separate fluid. Additionally, MS-FLUKSS allows us to model turbulence generated by pickup ions. We use MS-FLUKSS to investigate the evolution of plasma and turbulent fluctuations along the trajectory of the New Horizons spacecraft using plasma and turbulence parameters from OMNI data as time-dependent boundary conditions at 1 AU for the Reynolds-averaged MHD equations. We compare the model with in situ plasma observations by New Horizons, Voyager 2, and Ulysses. We also compare the model pickup proton parameters with those derived from the Ulysses-SWICS data.
Application of TRUST Principles in LISIRD
Hunter Leise
Tom Baltzer

Hunter Leise

and 9 more

December 04, 2019
The LASP Interactive Solar IRradiance Datacenter (LISIRD), lasp.colorado.edu/lisird, is a website where researchers can discover, visualize, and download solar data from a variety of space missions, instruments, models, and laboratories. LISIRD focuses on making heliophysics research as effortless as possible by making solar data openly available and easy to analyze through an intuitive user interface, detailed metadata, interactive plotting capabilities, and a catalog of over 75 datasets. This poster will discuss how LISIRD currently demonstrates, and aspires to better comply with, the TRUST Principles (Transparency, Responsibility, User Community, Sustainability, and Technology). Topics will include metadata efforts to improve dataset transparency, usability testing to further understand the needs of user communities, and how we designed our current technology stack to make development and maintenance easier and more sustainable.
LISIRD: An Online Resource for Making Solar Data More Accessible
Hunter Leise
Tom Baltzer

Hunter Leise

and 8 more

December 04, 2019
Finding quality solar data can be difficult, if not cumbersome at best, especially for students and early career researchers. The trend of having static files in an obscure format served in a hidden directory on some seemingly random server certainly doesn’t help the situation, not to mention the datasets that are only accessible via a researcher’s hard drive. The LASP Interactive Solar IRradiance Datacenter (LISIRD), lasp.colorado.edu/lisird, seeks to alleviate many of these pains. LISIRD is a website where students and researchers can discover, visualize, and download solar data from a variety of space missions, instruments, models, and laboratories. LISIRD focuses on making heliophysics research as effortless as possible by making solar data openly available and easy to analyze through an intuitive user interface, detailed metadata, interactive plotting capabilities, and a catalog of over 75 datasets. This poster will demonstrate the key features of LISIRD, provide details on the datasets it serves, outline future plans for improvement and growth, and discuss how it can be used as a valuable resource in space physics curricula.
Energized Oxygen in the Magnetotail: Onset and Evolution of Magnetic Reconnection
Don George
Jorg-Micha Jahn

Don E George

and 1 more

June 30, 2020
Oxygen ions are a major constituent of magnetospheric plasma, yet the role of oxygen in processes such as magnetic reconnection is poorly understood. Observations show that significant energized $O^+$ can be present in a magnetotail current sheet. A population of thermal $O^+$ only has a minor effect on magnetic reconnection. Despite this, published studies have so far only concentrated on the role of the low-energy thermal $O^+$. We present a study of magnetic reconnection in a thinning current sheet with energized $O^+$ present. Well-established, three-species, 2.5D Particle-In-Cell (PIC) kinetic simulations are used. Simulations of thermal $H^+$ and thermal $O^+$ validate our setup. We energize a thermal background $O^+$ based on published measurements. We apply a range of energization to the background $O^+$. We discuss the effects of energized $O^+$ on current sheet thinning and the onset and evolution of magnetic reconnection. Energized $O^+$ has a major impact on the onset and evolution of magnetic reconnection. Energized $O^+$ causes a two-regime onset response in a thinning current sheet. As energization increases in the lower-regime, reconnection develops at a single primary {X}-line, increases time-to-onset, and suppresses the rate of evolution. As energization continues to increase in the higher-regimes, reconnection develops at multiple {X}-lines, forming a stochastic plasmoid chain; decreases time-to-onset; and enhances evolution via a plasmoid instability. Energized $O^+$ drives a depletion of the background $H^+$ around the current sheet. As energization increases, the thinning begins to slow and eventually reverses, leading to disruption of the current sheet via a plasmoid instability.
← Previous 1 2 3 4 5 6 7 8 9 10 11 … 29 30 Next →
Back to search
Authorea
  • Home
  • About
  • Product
  • Preprints
  • Pricing
  • Blog
  • Twitter
  • Help
  • Terms of Use
  • Privacy Policy