Kinetic aspects of reconnection at the magnetopause

Observations presented here support the kinetic (or single particle) description of reconnection where ions interacting with the magnetopause conserve their pitch angles or change them by equal amounts as in adiabatic motion. These observations include ion reflection and transmission at the magnetopause and time of flight effects associated with the magnetopause layers, with an emphasis here on ion reflection. Velocities of the reflected distributions predicted from this kinetic description are in good agreement with observed velocities. However, predicted velocities for the transmitted distributions are often higher than observed ones. Reflected distributions are also heated at the magnetopause; however, this heating is less important than the large scale ion motion. Reflection coefficients at the magnetopause are high (averaging 30%), appear to be the same on either side of the magnetopause, and have little or no dependence on ion mass. Time of flight effects result from the finite extent of the reconnection layers and are best observed at the edges of the layers

Measurement of precipitation induced FUV emission and Geocoronal Lyman Alpha from the IMI mission

This final report describes the activities of the Lockheed Martin Palo Alto Research Laboratory in studying the measurement of ion and electron precipitation induced Far Ultra-Violet (FUV) emissions and Geocoronal Lyman Alpha for the NASA Inner Magnetospheric Imager (IMI) mission. this study examined promising techniques that may allow combining several FUV instruments that would separately measure proton aurora, electron aurora, and geocoronal Lyman alpha into a single instrument operated on a spinning spacecraft. The study consisted of two parts. First, the geocoronal Lyman alpha, proton aurora, and electron aurora emissions were modeled to determine instrument requirements. Second, several promising techniques were investigated to determine if they were suitable for use in an IMI-type mission. Among the techniques investigated were the Hydrogen gas cell for eliminating cold geocoronal Lyman alpha emissions, and a coded aperture spectrometer with sufficient resolution to separate Doppler shifted Lyman alpha components

First MMS Observation of Energetic Particles Trapped in High-Latitude Magnetic Field Depressions

We present a case study of the Magnetospheric Multiscale (MMS) observations of the Southern Hemispheric dayside magnetospheric boundaries under southward interplanetary magnetic field direction with strong By component. During this event MMS encountered several magnetic field depressions characterized by enhanced plasma beta and high fluxes of high‐energy electrons and ions at the dusk sector of the southern cusp region that resemble previous Cluster and Polar observations of cusp diamagnetic cavities. Based on the expected maximum magnetic shear model and magnetohydrodynamic simulations, we show that for the present event the diamagnetic cavity‐like structures were formed in an unusual location. Analysis of the composition measurements of ion velocity distribution functions and magnetohydrodynamics simulations show clear evidence of the creation of a new kind of magnetic bottle structures by component reconnection occurring at lower latitudes. We propose that the high‐energy particles trapped in these cavities can sometimes end up in the loss cone and leak out, providing a likely explanation for recent high‐energy particle leakage events observed in the magnetosheath

Interstellar neutral helium in the heliosphere from IBEX observations. V. Observations in IBEX-Lo ESA steps 1, 2, & 3

Direct-sampling observations of interstellar neutral (ISN) He by Interstellar Boundary Explorer (IBEX) provide valuable insight into the physical state of and processes operating in the interstellar medium ahead of the heliosphere. The ISN He atom signals are observed at the four lowest ESA steps of the IBEX-Lo sensor. The observed signal is a mixture of the primary and secondary components of ISN He and H. Previously, only data from one of the ESA steps have been used. Here, we extended the analysis to data collected in the three lowest ESA steps with the strongest ISN He signal, for the observation seasons 2009-2015. The instrument sensitivity is modeled as a linear function of the atom impact speed onto the sensor's conversion surface separately for each ESA step of the instrument. We found that the sensitivity increases from lower to higher ESA steps, but within each of the ESA steps it is a decreasing function of the atom impact speed. This result may be influenced by the hydrogen contribution, which was not included in the adopted model, but seems to exist in the signal. We conclude that the currently accepted temperature of ISN He and velocity of the Sun through the interstellar medium do not need a revision, and we sketch a plan of further data analysis aiming at investigating ISN H and a better understanding of the population of ISN He originating in the outer heliosheath.Comment: 20 pages, 5 figures, 5 tables, accepted for publication in the The Astrophysical Journa

Event Studies of O+ Density Variability Within Quietâ Time Plasma Sheet

To understand the variations of the O+ ions in the quietâ time plasma sheet between the regions of coldâ dense plasma sheet (CDPS) and hot plasma sheet (HPS), we conduct three event studies. These studies investigate the O+ densities in the two regions and how they are correlated with the strength of two magnetospheric sources important to ion outflows: the soft electron flux and Poynting flux toward the ionosphere. The CDPS is characterized by twoâ component ions (one hot component mixed with one cold component), while the HPS ions consist of only one single hot component. Comparing the O+ density between the CDPS and HPS of the same event, the average CDPS O+ density was higher by a factor of ~2â 5. Compared to the HPS, the soft electron flux source within the CDPS was higher, consistent with the fact that the soft electron precipitation and O+ upward number fluxes observed in the ionosphere were also higher within the CDPS. In the plasma sheet, broadband ultralowâ frequency electric and magnetic field waves with the characteristics of kinetic Alfvén waves were often more intense within the CDPS, providing a stronger Poynting flux source. In addition, electron resonant interaction with kinetic Alfvén waves results in acceleration along the magnetic fields and, thus, may drive the observed soft electron precipitation. These correlations suggest that the higher soft electron precipitation and Poynting flux coming from the magnetospheric CDPS likely produce larger ionospheric O+ outflows back to the magnetosphere, thus resulting in the higher O+ density within the CDPS.Key PointsO+ densities in coldâ dense plasma sheet in the three quietâ time events were higher than those in hot plasma sheet by a factor of ~2â 5Higher soft electron fluxes in the magnetosphere and soft electron precipitation in the ionosphere in coldâ dense than hot plasma sheetMore intense kinetic Alfven waves within the CDPS, providing stronger Poynting flux downward to the ionospherePeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150564/1/jgra54977_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150564/2/jgra54977.pd