Evaluation of a method to derive ionospheric conductivities using two auroral emissions (428 and 630 nm) measured with a photometer at Tromsø (69.6°N)

This paper mainly aims at evaluating capabilities of derivation of ionospheric conductivities using two principal auroral emissions (427.8 and 630 nm). We have evaluated a photometric method of derivation of ionospheric conductivities based on simultaneous observations of a photometer (feld of view = ~1.2°), a digital camera, and the EISCAT UHF radar (feld of view = ~0.7°) operated at Tromsø, Norway (69.6°N, 19.2°E), for two nights on October 10 and 11, 2002. We have compared height-integrated Pedersen and Hall conductivities with a post-integration time of 10 s derived from EISCAT UHF radar observations and photometer observations with wavelengths of 427.8 and 630.0 nm. Sky images taken with the digital camera are utilized for distinguishing types of auroras in the views of the EISCAT UHF radar and the photometer. In general, a good agreement of temporal variations of the height-integrated Pedersen and Hall conductivities was found between EISCAT and photometer values. In cases of auroral arcs passing by in the feld of view, however, diferences in derived values between the two methods were found. Possible causes of the differences are discussed. We conclude that (1) the photometric method using 427.8 and 630 nm can capture temporal variations of the conductivities well, but unavoidable underestimations of the Pedersen (about 30–40%) and the Hall (about 50–60%) conductivities are involved, and (2) care is necessary for using photometric observational data when auroral arcs appear in the feld of view

Altitude of pulsating arcs as inferred from tomographic measurements

Abstract Data from three all-sky cameras in Kiruna and Tjautjas (Sweden) were used to estimate the altitude of pulsating arc-like forms using optical tomography. The event under consideration occurred during the substorm recovery phase and comprised both periodic luminosity variation of the on/off type with repetition periods of 3–6 s (main pulsations) and faster scintillation (approximately 2 Hz) during the “on” phase of the main pulsations. It is found that (1) the altitudes of the pulsating auroral arcs decrease during “on” intervals from ~ 95 km to ~ 92 km and (2) for two closely spaced arcs, internal modulation took place only in the lowest arc. The results may be interpreted in the frame of the traditional mechanism assuming electron scattering via VLF-wave/particle interaction in the equatorial magnetosphere, while the internal modulation may also be alternatively interpreted in the frame of the less-often inferred mechanism of field-aligned acceleration somewhere between the equatorial plane and ionosphere

CAN-bus system for vehicle actuation and data logging with Arrowhead Framework

The use of micro controllers in automotive application have exploded during the last half century. What was initially a set of mechanical systems that formed a vehicle have now become a collection of computers on wheels. The reason is quite obvious: micro controllers use several inputs to optimize the performance of systems; for example an engine control or an active safety system.The different inputs and outputs to these electronic units (electronic control unit, ECU) are of interest to other such units thereby justifying the need of inter-ECU communications. The Controller Area Network (CAN) bus has been developed to facilitate this communication. It is a message based protocol and is very resilient. It is however relatively slow and limited in terms of security. Security is assured only by trying to keep the message identification tags confidential and the bus physically separated to other network. A couple of decades ago our society embraced the Information Technology (IT) revolution. It allowed people to have extensive access to information. From a technology point of view, IT is based on the use of the Internet, which has been initially designed by the US military for robust applications. It is fast and its security is sufficiently high that we use it to communicate with our banks where we keep all our life savings.The aim of this thesis has been to combine these technologies such that a vehicle with a CAN bus could offer services (just like a bank does) over the Internet. The goal then is to transform a CAN bus to become a service provider over the Internet. The services are the broadcasted CAN messages made available to authorized interested parties and can post information and actuations to the ECUs connected to the CAN bus. A vehicle in that case becomes a cyber physical system. To make this transformation possible, we use the open source Arrowhead Framework, which is based on a Service Oriented Architecture (SOA). The available services are made known via a Service Registry and Orchestration service prosumers. Concretely, the work in this thesis project has been to develop (i.e., to design and implement) a CAN service prosumer that is Arrowhead Framework compliant. It has been successfully tested with another service prosumer, which is an Arrowhead Framework compliant data logger. The driving motivation for the thesis project are construction equipment machines, such as wheel loaders and excavators, which are vehicles with booms or arms. The aspiration is that they not only drive autonomously but also dig autonomously. This ambition shall require large amount of data to be exchanged, something that a CAN bus cannot handle