The Neupert effect and new RHESSI measures of thetotal energy in electrons accelerated in solar flares

It is believed that a large fraction of the total energy released in a solar flare goes initially into acceleratedelectrons. These electrons generate the observed hard X-ray bremsstrahlung as they lose most of their energy by coulomb collisions in the lower corona and chromosphere. Results from the Solar Maximum Mission showed that there may be even more energy in accelerated electrons with energies above 25 keV than in the soft X-ray emitting thermal plasma. If this is the case, it is difficult to understand why the Neupert Effect — the empirical result that for many flares the time integral of the hard X-ray emission closely matches the temporal variation of the soft X-ray emission — is not more clearly observed in many flares. From recent studies, it appears that the fraction of the released energy going into accelerated electrons is lower, on average, for smaller flares than for larger flares. Also, from relative timing differences, about 25% of all flares are inconsistent with the Neupert Effect. The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) is uniquely capable of investigating the Neupert Effec since it covers soft X-rays down to 3 keV (when both attenuators are out of the field of view) and hard X-rays with keV energy resolution, arcsecond-class angular resolution, and sub-second time resolution. When combined with the anticipated observations from the Soft X-ray Imager on the next GOES satellite, these observations will provide us with the ability to track the Neupert Effect in space and time and learn more about the relation between plasma heating and particle acceleration. The early results from RHESSI show that the electron spectrum extends down to as low as 10 keV in many flares, thus increasing the total energy estimates of the accelerated electrons by an order of magnitude or more compared with the SMM values. This combined with the possible effects of filling factors smaller than unity for the soft X-ray plasma suggest that there is significantly more energy in nonthermal electrons than in the soft X-ray emitting plasma in many flares.     

Distinct EUV minimum of the solar irradiance (16–40 nm) observed by SolACES spectrometers onboard the International Space Station (ISS) in August/September 2009

In the field of terrestrial climatology the continuous monitoring of the solar irradiance with highest possible accuracy is an important goal. SolACES as a part of the ESA mission SOLAR on the ISS is measuring the short-wavelength solar EUV irradiance from 16–150 nm. This data will be made available to the scientific community to investigate the impact of the solar irradiance variability on the Earth’s climate as well as the thermospheric/ionospheric interactions that are pursued in the TIGER program. Since the successful launch with the shuttle mission STS-122 on February 7th, 2008, SolACES initially recorded the low EUV irradiance during the extended solar activity minimum. Thereafter it has been observing the EUV irradiance during the increasing solar activity with enhanced intensity and changing spectral composition. SolACES consists of three grazing incidence planar grating spectrometers. In addition there are two three-signal ionisation chambers, each with exchangeable band-pass filters to determine the absolute EUV fluxes repeatedly during the mission. One important problem of space-borne instrumentation recording the solar EUV irradiance is the degradation of the spectrometer sensitivity. The two double ionisation chambers of SolACES, which could be re-filled with three different gases for each recording, allow the recalibration of the efficiencies of the three SolACES spectrometers from time to time.     

The Balloon Array for RBSP Relativistic Electron Losses (BARREL)

BARREL is a multiple-balloon investigation designed to study electron losses from Earth’s Radiation Belts. Selected as a NASA Living with a Star Mission of Opportunity, BARREL augments the Radiation Belt Storm Probes mission by providing measurements of relativistic electron precipitation with a pair of Antarctic balloon campaigns that will be conducted during the Austral summers (January-February) of 2013 and 2014. During each campaign, a total of 20 small (～20 kg) stratospheric balloons will be successively launched to maintain an array of ～5 payloads spread across ～6 hours of magnetic local time in the region that magnetically maps to the radiation belts. Each balloon carries an X-ray spectrometer to measure the bremsstrahlung X-rays produced by precipitating relativistic electrons as they collide with neutrals in the atmosphere, and a DC magnetometer to measure ULF-timescale variations of the magnetic field. BARREL will provide the first balloon measurements of relativistic electron precipitation while comprehensive in situ measurements of both plasma waves and energetic particles are available, and will characterize the spatial scale of precipitation at relativistic energies. All data and analysis software will be made freely available to the scientific community.     

The extreme ultraviolet spectrum of the sun

The present state of knowledge of the spectrum of the sun from 3000 Å to 170 Å is critically reviewed. The characteristics of the different photographic and photoelectric spectroscopic instruments and the results are summarized and compared. Topics covered are line identifications, intensities, the continuum and its origin, the sun's surface in Lyman alpha, the profiles of H and K of Mg II, Lyman alpha and beta, and monitoring work conducted from rockets and satellites, including OSO-I.     

Rare observation of daytime whistlers at very low latitude (L = 1.08)

The source region and propagation mechanism of low latitude whistlers (Geomag. lat. <30°) have puzzled scientific community for last many decades. In view of recent reports, there is consensus on the source region of low latitude whistlers in the vicinity of the conjugate point. But the plausible conditions of ionospheric medium through which they travel are still uncertain. In addition to that, the whistlers in daytime are never observed at geomagnetic latitudes less than 20°. Here, for the first time, we present a rare observations of whistlers during sunlit hours from a very low-latitude station Allahabad (Geomag. Lat: 16.79°N, L = 1.08) in India on 04 February 2011. More than 90 whistlers are recorded during 1200–1300 UT during which the whole propagation path from lightning source region to whistler observation site is under sunlit. The favorable factors that facilitated the whistlers prior to the sunset are investigated in terms of source lightning characteristics, geomagnetic and background ionospheric medium conditions. The whistler activity period was found to be geomagnetically quiet. However, a significant suppression in ionospheric total electron content (TEC) compared to its quiet day average is found. This shows that background ionospheric conditions may play a key role in low latitude whistler propagation. This study reveals that whistlers can occur under sunlit hours at latitudes as low as L = 1.08 when the source lightning and ionospheric medium characteristics are optimally favorable.     

Surface, Subsurface and Atmosphere Exchanges on the Satellites of the Outer Solar System

The surface morphology of icy moons is affected by several processes implicating exchanges between their subsurfaces and atmospheres (if any). The possible exchange of material between the subsurface and the surface is mainly determined by the mechanical properties of the lithosphere, which isolates the deep, warm and ductile ice material from the cold surface conditions. Exchanges through this layer occur only if it is sufficiently thin and/or if it is fractured owing to tectonic stresses, melt intrusion or impact cratering. If such conditions are met, cryomagma can be released, erupting fresh volatile-rich materials onto the surface. For a very few icy moons (Titan, Triton, Enceladus), the emission of gas associated with cryovolcanic activity is sufficiently large to generate an atmosphere, either long-lived or transient. For those moons, atmosphere-driven processes such as cryovolcanic plume deposition, phase transitions of condensable materials and wind interactions continuously re-shape their surfaces, and are able to transport cryovolcanically generated materials on a global scale. In this chapter, we discuss the physics of these different exchange processes and how they affect the evolution of the satellites’ surfaces.     

Multi-Target Tracking in Clutter without Measurement Assignment

When tracking targets using radars and sonars, the number of targets and the origin of data is uncertain. Data may be false measurements or clutter, or they may be detections from an unknown number of targets whose possible trajectories and detection processes can only be described in a statistical manner. Optimal all-neighbor multi-target tracking (MTT) in clutter enumerates all possible joint measurement-to-track assignments and calculates the a posteriori probabilities of each of these joint assignments. The numerical complexity of this process is combinatorial in the number of tracks and the number of measurements. One of the key differences between most MTT algorithms is the manner in which they reduce the computational complexity of the joint measurement-to-track assignment process. We propose an alternative approach, using a form of soft assignment, that enables us to bypass this step entirely. Specifically, our approach treats possible detections of targets followed by other tracks as additional clutter measurements. It starts by approximating the a~priori probabilities of measurement origin. These probabilities are then used to modify the clutter spatial density at the location of the measurements. A suitable single target tracking (STT) filter then uses the modified clutter intensity for updating the track state. In effect, the STT filter is transformed into an MTT filter with a numerical complexity that is linear in the number of tracks and the number of measurements. Simulations show the effectiveness of this approach in a number of different multi-target scenarios.     

Observations of ion cyclotron waves near synchronous orbit and on the ground

Ion cyclotron waves (hereafter ICW's) generated in the magnetosphere by the ion cyclotron instability of 10–100 keV protons are now known to be the origin of short-period (0.1–5 Hz) electromagnetic field oscillations observed by synchronous spacecraft and on the earth's surface. Observations of the various wave characteristics, including spectral and polarization properties that lead to the identification of generation and propagation mechanisms and regions in the magnetosphere are described with reference to ATS-6, GEOS and ground-based wave data and interpreted using cold plasma propagation theory. The presence of heavy ions (O⁺, He⁺) dramatically modifies ICW magnetospheric propagation characteristics giving rise to spectral slots and polarization reversals. These properties may be used in plasma diagnostics. Finally satellite-ground correlations and techniques for determining the magnetospheric source position of ICW's not seen at synchronous orbit but observed on the ground as structured Pc1 pulsations are considered.     

A system of flight data acquisition,processing, and recording

A system for recording and analysis of flight information including the technical condition of a control object and the state of its controller’s health in real time aboard a flight vehicle and in ground-based air traffic control centers is described.