Density and temperature of energetic electrons in the Earth's magnetotail derived from high-latitude GPS observations during the declining phase of the solar cycle

Single relativistic-Maxwellian fits are made to high-latitude GPS-satellite observations of energetic electrons for the period January 2006-November 2010; a constellation of 12 GPS space vehicles provides the observations. The derived fit parameters (for energies similar to 0.1-1.0 MeV), in combination with field-line mapping on the nightside of the magnetosphere, provide a survey of the energetic electron density and temperature distribution in the magnetotail between McIlwain L-values of L = 6 and L = 22. Analysis reveals the characteristics of the density-temperature distribution of energetic electrons and its variation as a function of solar wind speed and the Kp index. The density-temperature characteristics of the magnetotail energetic electrons are very similar to those found in the outer electron radiation belt as measured at geosynchronous orbit. The energetic electron density in the magnetotail is much greater during increased geomagnetic activity and during fast solar wind. The total electron density in the magnetotail is found to be strongly correlated with solar wind speed and is at least a factor of two greater for high-speed solar wind (V-SW = 500-1000 km s(-1)) compared to low-speed solar wind (V-SW = 100-400 km s(-1)). These results have important implications for understanding (a) how the solar wind may modulate entry into the magnetosphere during fast and slow solar wind, and (b) if the magnetotail is a source or a sink for the outer electron radiation belt

Electron loss rates from the outer radiation belt caused by the filling of the outer plasmasphere: The calm before the storm

Measurements from seven spacecraft in geosynchronous orbit are analyzed to determine the decay rate of the number density of the outer electron radiation belt prior to the onset of high-speed-stream-driven geomagnetic storms. Superposed-data analysis is used with a collection of 124 storms. When there is a calm before the storm, the electron number density decays exponentially before the storm with a 3.4-day e-folding time: beginning about 4 days before storm onset, the density decreases from ∼4 × 10−4 cm−3 to ∼1 × 10−4 cm−3. When there is not a calm before the storm, the number density decay is very small. The decay in the number density of radiation belt electrons is believed to be caused by pitch angle scattering of electrons into the atmospheric loss cone as the outer plasmasphere fills during the calms. This is confirmed by separately measuring the density decay rate for times when the outer plasmasphere is present or absent. While the radiation belt electron density decreases, the temperature of the electron radiation belt holds approximately constant, indicating that the electron precipitation occurs equally at all energies. Along with the number density decay, the pressure of the outer electron radiation belt decays, and the specific entropy increases. From the measured decay rates, the electron flux to the atmosphere is calculated, and that flux is 3 orders of magnitude less than thermal fluxes in the magnetosphere, indicating that the radiation belt pitch angle scattering is 3 orders weaker than strong diffusion. Energy fluxes into the atmosphere are calculated and found to be insufficient to produce visible airglow

Thermochemical stability of low-iron, manganese-enriched olivine in astrophysical environments

Low-iron, manganese-enriched (LIME) olivine grains are found in cometary samples returned by the Stardust mission from comet 81P/Wild 2. Similar grains are found in primitive meteoritic clasts and unequilibrated meteorite matrix. LIME olivine is thermodynamically stable in a vapor of solar composition at high temperature at total pressures of a millibar to a microbar, but enrichment of solar composition vapor in a dust of chondritic composition causes the FeO/MnO ratio of olivine to increase. The compositions of LIME olivines in primitive materials indicate oxygen fugacities close to those of a very reducing vapor of solar composition. The compositional zoning of LIME olivines in amoeboid olivine aggregates is consistent with equilibration with nebular vapor in the stability field of olivine, without re-equilibration at lower temperatures. A similar history is likely for LIME olivines found in comet samples and in interplanetary dust particles. LIME olivine is not likely to persist in nebular conditions in which silicate liquids are stable

Third Conference on Artificial Intelligence for Space Applications, part 2

Topics relative to the application of artificial intelligence to space operations are discussed. New technologies for space station automation, design data capture, computer vision, neural nets, automatic programming, and real time applications are discussed

Electron number density, temperature and energy density at GEO and links to the solar wind:a simple predictive capability

Many authors have studied the outer radiation belts response to different solar wind drivers, with the majority investigating electron flux variations. Using partial moments (electron number density, temperature and energy density) from GOES-13 during 2011 allows for changes in the number of electrons and the temperature of the electrons to be distinguished, which is not possible with the outputs of individual instrument channels. This study aims to produce a coarse predictive capability of the partial moments from GOES-13 by determining which solar wind conditions exhibit the strongest relationship with electron variations at GEO. Investigating how the electron distribution at GEO is affected by fluctuations in this primary driver, both instantaneous and time delayed, allows for this to be achieved. These predictive functions are then tested against data from 2012. It is found that using solely the solar wind velocity as a driver results in predicted values that accurately follow the general trend of the observed moments. This study is intended to make further progress in quantifying the relationship between the solar wind and electron number density, temperature and energy density at GEO. Our results provide a coarse predictive capability of these quantities that can be expanded upon in future studies to incorporate other solar wind drivers to improve accuracy

Exploring the cross correlations and autocorrelations of the ULF indices and incorporating the ULF indices into the systems science of the solar wind‐driven magnetosphere

The ULF magnetospheric indices S gr , S geo , T gr , and T geo are examined and correlated with solar wind variables, geomagnetic indices, and the multispacecraft‐averaged relativistic‐electron flux F in the magnetosphere. The ULF indices are detrended by subtracting off sine waves with 24 h periods to form S grd , S geod , T grd , and T geod . The detrending improves correlations. Autocorrelation‐function analysis indicates that there are still strong 24 h period nonsinusoidal signals in the indices which should be removed in future. Indications are that the ground‐based indices S grd and T grd are more predictable than the geosynchronous indices S geod and T geod . In the analysis, a difference index ∆ S mag  ≈  S grd − 0.693 S geod is derived: the time integral of ∆ S mag has the highest ULF index correlation with the relativistic‐electron flux F . In systems‐science fashion, canonical correlation analysis (CCA) is used to correlate the relativistic‐electron flux simultaneously with the time integrals of (a) the solar wind velocity, (b) the solar wind number density, (c) the level of geomagnetic activity, (d) the ULF indices, and (e) the type of solar wind plasma (coronal hole versus streamer belt): The time integrals of the solar wind density and the type of plasma have the highest correlations with F . To create a solar wind‐Earth system of variables, the two indices S grd and S geod are combined with seven geomagnetic indices; from this, CCA produces a canonical Earth variable that is matched with a canonical solar wind variable. Very high correlations ( r corr  = 0.926) between the two canonical variables are obtained. Key Points ULF indices contain nonsinusoidal periodic signals in universal time ULF indices are not the strongest correlator with radiation belt electron fluxes ULF indices were integrated into a mathematical system science of magnetospherePeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108067/1/jgra51050.pd

Compressional perturbations of the dayside magnetosphere during high‐speed‐stream‐driven geomagnetic storms

The quasi‐DC compressions of the Earth’s dayside magnetic field by ram‐pressure fluctuations in the solar wind are characterized by using multiple GOES spacecraft in geosynchronous orbit, multiple Los Alamos spacecraft in geosynchronous orbit, global MHD simulations, and ACE and Wind solar wind measurements. Owing to the inward‐outward advection of plasma as the dayside magnetic field is compressed, magnetic field compressions experienced by the plasma in the dayside magnetosphere are greater than the magnetic field compressions measured by a spacecraft. Theoretical calculations indicate that the plasma compression can be a factor of 2 higher than the observed magnetic field compression. The solar wind ram‐pressure changes causing the quasi‐DC magnetospheric compressions are mostly owed to rapid changes in the solar wind number density associated with the crossing of plasma boundaries; an Earth crossing of a plasma boundary produces a sudden change in the dayside magnetic field strength accompanied by a sudden inward or outward motion of the plasma in the dayside magnetosphere. Superposed epoch analysis of high‐speed‐stream‐driven storms was used to explore solar wind compressions and storm time geosynchronous magnetic field compressions, which are of particular interest for the possible contribution to the energization of the outer electron radiation belt. The occurrence distributions of dayside magnetic field compressions, solar wind ram‐pressure changes, and dayside radial plasma flow velocities were investigated: all three quantities approximately obey power law statistics for large values. The approximate power law indices for the distributions of magnetic compressions and ram‐pressure changes were both −3.Key PointsQuasi‐DC compressions of the dayside magnetosphere are responses to solar wind ram‐pressure changesThe plasma compression in the dayside is greater than the field compression measured by a satelliteField compressions, ram‐pressure changes, and flow velocities obey large‐value power law statisticsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146460/1/jgra52633.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146460/2/jgra52633_am.pd

A density-temperature description of the outer electron radiation belt during geomagnetic storms

Bi-Maxwellian fits are made to energetic-electron flux measurements from seven satellites in geosynchronous orbit, yielding a number density (n) and temperature (T) description of the outer electron radiation belt. For 54.5 spacecraft years of measurements the median value of n is 3.7 × 10−4 cm−3, and the median value of T is 148 keV. General statistical properties of n, T, and the 1.1–1.5 MeV flux F are investigated, including local-time and solar-cycle dependencies. Using superposed-epoch analysis where the zero epoch is convection onset, the evolution of the outer electron radiation belt through high-speed-stream-driven storms is investigated. The number-density decay during the calm before the storm, relativistic-electron dropouts and recoveries, and the heating of the outer electron radiation belt during storms are analyzed. Using four different “triggers” (sudden storm commencement (SSC), southward interplanetary magnetic field (IMF) portions of coronal mass ejection (CME) sheaths, southward-IMF portions of magnetic clouds, and minimum Dst) a selection of CME-driven storms are analyzed with superposed-epoch techniques. For CME-driven storms, only a very modest density decay prior to storm onset is found. In addition, the compression of the outer electron radiation belt at the time of SSC is analyzed, the number-density increase and temperature decrease during storm main phase are characterized, and the increase in density and temperature during storm recovery phase is determined. During the different phases of storms, changes in the flux are sometimes in response to changes in the temperature, sometimes to changes in the number density, and sometimes to changes in both. Differences are found between the density-temperature and flux descriptions, and it is concluded that more information is available using the density-temperature description