Investigation of MAGSAT and TRIAD magnetometer data to provide corrective information on high-lattitude external fields

Disturbances in the MAGSAT magnetometer data set due to high latitude phenomena were evaluated. Much of the categorization of disturbances due to Birkeland currents, ionospheric Hall currents, fine structure and wave phenomena was done with the MAGSAT data catalog. A color graphics technique was developed for the display of disturbances from multiple orbits, from which one can infer a 'global-image' of the current systems of the auroral zone. The MAGSAT 4/81 magnetic field model appears to represent the Earth's main field at high latitudes very well for the epoch 1980. MAGSAT's low altitude allows analysis of disturbances in the magnetometer data due to ionospheric electrojet currents. These current distributions were modeled properly for single events as a precursor to the inference of the Birkeland current system. MAGSAT's orbit was approximately shared with that of the Navy/APL TRIAD satellite. This allowed space-time studies of the magnetic disturbance signatures to be performed, the result being an approximately 75% agreement in, as well as high frequency of, signatures due to Birkeland currents. Thus the field-aligned currents are a steady-state participant in the Earth's magnetospheric current system

Blurring Boundaries: Negotiating Researchers’ Positionality and Identities in Digital Qualitative Research

This contribution discusses a series of methodological, ethical, and ontological challenges encountered by the authors during a series of recent socio-criminological studies based on digital ethnography and investigating sensitive and emotive issues. Particularly, we will discuss the practical difficulties we encountered in navigating several increasingly blurred boundaries, such as those among: (1) the researchers’ private and public academic/personal selves online; (2) the shifting of the traditional power imbalances between the researcher and research participants; (3) concerns over impartiality in research; and (4) elements of ethnography and autoethnography becoming obfuscated. We consider these dilemmas in the context of the pervasiveness of digital technologies within contemporary social life, such that we as researchers are always simultaneously on and offline, with our studies at risk of becoming all-consuming and encroaching on all areas of our lives. We will see how these blurred boundaries entail an inescapable continuous negotiation of researcher identity and positionality, and some of their practical consequences. We aim to encourage further discussion about these novel challenges faced whilst undertaking online research, and re-examination of the related ethical principles regarding these contexts

Direct contacts with potential interviewees when carrying out online ethnography on controversial and polarized topics: a loophole in ethics guidelines.

Direct contacts with research participants in online ethnography are an important tool to better understand complex social dynamics in cyberspace. The current ethical approaches guiding academic research, however, can be problematic in this regard, creating unintended tensions leading to potential research biases as well as safety and wellbeing issues for researchers working on controversial and polarized topics. The onus, we argue, ends up being on academics to protect and separate the personal information available about them online from the professional, trying to overcome what seems to be an inevitable blurring of boundaries. In this research note, we present two case studies to highlight what we perceive as a loophole in current ethics guidelines

Magnetic field observations in high beta regions of the magnetosphere

OGO for magnetic field observations in high beta regions of magnetospher

Iterative soft-detection of space-time-frequency shift keying

Inspired by the concept of Space-Time Shift Keying (STSK), the further evolved philosophy of Space-Time-Frequency Shift Keying (STFSK) was proposed for Multiple-Input-Multiple-Output (MIMO) wireless communications, where a beneficial diversity gain may be gleaned from three different domains, namely the space-, time- and frequency-domain. In this paper we proposed soft-detected STFSK in order to conceive its iterative decoding aided version combined with channel codes. Our results showed that the STFSK soft demodulator, which iteratively exchanges extrinsic information with channel codes, may decrease the required transmit power by approximately 3 dB at the Eb/N0 of 10-5, compared to hard-decision STFSK. Furthermore, the detection complexity of both the hard- and the soft-decision STFSK demodulator is quantified in terms of the number of multiplications and additions required for each detection iteration

Random Hamiltonian in thermal equilibrium

A framework for the investigation of disordered quantum systems in thermal equilibrium is proposed. The approach is based on a dynamical model--which consists of a combination of a double-bracket gradient flow and a uniform Brownian fluctuation--that `equilibrates' the Hamiltonian into a canonical distribution. The resulting equilibrium state is used to calculate quenched and annealed averages of quantum observables.Comment: 8 pages, 4 figures. To appear in DICE 2008 conference proceeding

Power of sequential protocols in hidden quantum channel discrimination

In many natural and engineered systems, unknown quantum channels act on a subsystem that cannot be directly controlled and measured, but is instead learned through a controllable subsystem that weakly interacts with it. We study quantum channel discrimination (QCD) under these restrictions, which we call hidden system QCD (HQCD). We find that sequential protocols achieve perfect discrimination and saturate the Heisenberg limit. In contrast, depth-1 parallel and multi-shot protocols cannot solve HQCD. This suggests that sequential protocols are superior in experimentally realistic situations.Comment: 18pages, 10figure

The origin of short-lived radionuclides and the astrophysical environment of solar system formation

Based on early solar system abundances of short-lived radionuclides (SRs), such as $^{26}$Al (T$_{1/2} = 0.74$ Myr) and $^{60}$Fe (T$_{1/2} = 1.5$ Myr), it is often asserted that the Sun was born in a large stellar cluster, where a massive star contaminated the protoplanetary disk with freshly nucleosynthesized isotopes from its supernova (SN) explosion. To account for the inferred initial solar system abundances of short-lived radionuclides, this supernova had to be close ($\sim$ 0.3 pc) to the young ($\leqslant$ 1 Myr) protoplanetary disk. Here we show that massive star evolution timescales are too long, compared to typical timescales of star formation in embedded clusters, for them to explode as supernovae within the lifetimes of nearby disks. This is especially true in an Orion Nebular Cluster (ONC)-type of setting, where the most massive star will explode as a supernova $\sim$ 5 Myr after the onset of star formation, when nearby disks will have already suffered substantial photoevaporation and/or formed large planetesimals. We quantify the probability for {\it any} protoplanetary disk to receive SRs from a nearby supernova at the level observed in the early solar system. Key constraints on our estimate are: (1) SRs have to be injected into a newly formed ($\leqslant$ 1 Myr) disk, (2) the disk has to survive UV photoevaporation, and (3) the protoplanetary disk must be situated in an enrichment zone permitting SR injection at the solar system level without disk disruption. The probability of protoplanetary disk contamination by a supernova ejecta is, in the most favorable case, 3 $\times$ 10$^{-3}$