A Study of the Morphology of Magnetic Storms: Moderate Magnetic Storms

Some average characteristics are determined for 136 moderate magnetic storms with sudden commencements that occurred during the interval 1902-1945. The average storm field is resolved for different epochs of storm time st into Dst, independent of local time, that is, of longitude X , relative to the sun, and into DS, that depends on X , Part DS is expressed in terms of harmonic components with respect to X , and like Dst, the amplitudes and phases of these components, are functions of st and of geomagnetic latitude. They are determined, for each of the three magnetic elements, declination, horizontal force, and vertical force, at eight geomagnetic latitudes ranging from 80*N to 1°S. In the first, and main harmonic component of DS, its variations with respect to storm time differs notably from that of Dst: its maximum is attained earlier and its decay is more rapid. The storm -time changes of the smaller harmonic components of DS have been less fully determined. The average characteristics of moderate storms are compared with those of weak storms.The research reported in the document has been sponsored by the Air Force Cambridge Research Center, Air Research and Development Command, under Contract No, AF 19(604)-1732. AF 19(604)-1732 AFCRC-TR-57-295 AD 117-256LIST OF TABLES -- LIST OF FIGURES -- ABSTRACT -- 1. INTRODUCTION -- 2. THE OBSERVATORIES -- 3. THE STORM-TIME VARIATIONS : 3.1 Dst in the Geomagnetic-North Component, Hgm ; 3.2 Dst in the Geomagnetic-East Component, Egm ; 3.3 Dst in the Vertical Force -- 4. THE DISTURBANCE DAILY VARIATIONS -- 5. THE FIRST COMPONENT OF DS -- 6 „ THE HIGHER HARMONIC COMPONENTS OF DS AND SD -- 7. COMPARISON OF Dst AND DS -- 8 „ CONCLUSION : 8.1 The Intensity Index of Magnetic Storms ; 8.2 The Dst Variations ; 8.3 The DS and SD Variations ; 8.4 Future Plans -- 9. ACKNOWLEDGEMENTS -- REFERENCESYe

A Study of the Morphology of Magnetic Storms Great Magnetic Storms

Average characteristics are determined for 74 great magnetic storms with sudden commencements that occurred in 1902-1945. The storm field is resolved for different epochs of storm time into tv;o parts: (i) Dst, which is independent of local time, that is, of longitude A, relative to the sun, and (ii) DS, which depends on A . They are obtained, for each of the three magnetic elements, declination, horizontal force, and vertical force, at eight geomagnetic latitudes ranging from 80°N to 1°S. DS is harmonically analyzed; the first harmonic component is shown to be the main component of DS. The storm-time course of this component is compared with that of Dst; DS attains its maximum earlier and decays more rapidly. The results of the analysis of great storms are compared with those for weak and moderate storms that were reported previously. Some characteristics of Dst change with intensity. Except in magnitude, main characteristics of DS are independent of intensity.The research reported in the document has been sponsored by the Air Force Cambridge Research Center, Air Research and Development Command, under Contract No. AF 19(604)-2163.LIST OF TABLES -- LIST OF FIGURES -- ABSTRACT -- 1. INTRODUCTION -- 2. OBSERVATORIES -- 3. STORM-TIME VARIATIONS : 3.1 Dst in the geomagnetic-north component, Hgm ; 3.2 Dst in the geomagnetic-east component, Egm ; 3.3 Dst in the vertical force Z -- 4. DISTURBANCE DAILY VARIATIONS -- 5. FIRST HARMONIC COMPONENT OF DS -- 6 . HIGHER HARMONIC COMPONENTS OF DS AND SD -- 7. COMPARISON OF Dst AND DS -- 8 . SEASONAL VARIATIONS IN Dst : 8.1 Seasonal variation in Dst(H); season d and season j ; 8.2 Seasonal variation in Dst(H); season e and season s -- 9. SEASONAL VARIATIONS IN DS -- 10. CONCLUSION -- 11. ACKNOWLEDGEMENTS -- REFERENCESYe

Development of a Thermal Management System for Electrified Aircraft

This paper describes the development and optimization of a conceptual thermal management system for electrified aircraft. Here, a vertical takeoff and landing (VTOL) vehicle is analyzed with the following electrically sourced heat loads considered: motors, generators, rectifiers, and inverters. The vehicle will employ liquid-cooling techniques in order to acquire, transport, and reject waste heat from the vehicle. The purpose of this paper is to threefold: 1) Present a potential modeling framework for system level thermal management system simulation, 2) Analyze typical system characteristics, and 3) Perform optimization on a system developed for a specific vehicle to minimize weight gain, power utilization, and drag. Additionally, the paper will study the design process, specifically investigating the differences between steady state and transient sizing, comparing simulation techniques with a lower fidelity option and quantifying expected error

Motion of Small Suspended Particles in Nonuniform Gases

The motion of small suspended particles in a gas or gas mixture containing gradients of temperature, pressure, or composition is derived as a special case of the Chapman‐Enskog kinetic theory of gases, by formally treating the suspended particles as large molecules. Gas molecules colliding with the suspended particles are considered to rebound elastically, but a fraction f rebound in random directions and the remainder rebound specularly. The results check, in an indirect way, the calculations of Waldmann by a momentum transfer method on a slightly different model, in which the randomly rebounding molecules also have a random distribution of speeds. Significantly different results are predicted by the two models only in the presence of a temperature gradient (thermal diffusion), which has interesting implications concerning thermal diffusion in polyatomic gases.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70625/2/JCPSA6-36-3-627-1.pd

A study of magnetic storms and auroras

New notations for magnetic disturbance fields are proposed, based on the theoretical consideration of the electric current systems by which they are produced. A typical magnetic storm begins suddenly when the onrush of the front of the solar gas is halted by the earth's magnetic field. This effect (DCF field) is most markedly observed as a sudden increase of the horizontal component of the earth's field (the storm sudden commencement, abbreviated to ssc)— like a step function. In many cases, however, the change of the field during the ssc is more complicated, and different at different places. Such a complexity superposed on the simple increase (DCF) is ascribed to a complicated current system generated in the polar ionosphere (DP current). It is found that the changes of electromagnetic conditions in the polar regions are communicated, without delay, to lower latitudes, even down to the equatorial regions. It is inferred that the equatorial jet is affected by such a change and produces the abnormal enhancement of ssc along the magnetic dip equator. From the extensive analysis of several magnetic storms that occurred during the IGY and IGC, it is suggested that the capture of the solar particles in the outer geomagnetic field occurs when irregularities (containing tangled magnetic fields and high energy protons) embedded in the solar stream, impinge on the earth.. Thus the development of a magnetic storm depends on the distribution of such irregularities in the stream. The motions and resulting currents and magnetic fields of such "trapped" solar particles are studied in detail for a special model. It is inferred that a large decrease (DR field) must follow the initial increase; it is ascribed to the ring current produced by such motion of solar protons oi energy of order 500 Kev. It is proposed that during the storm there appears a transient 'storm-time1 belt well outside the outer radiation belt. It is predicted that the earth's magnetic field is reversed in limited regions when the ring current is appreciably enhanced. This involves the formation of neutral lines there. These may be of two kinds, called X lines or 0 lines according as they are crossed or encircled by magnetic lines of force. These may be entirely separated or may be joined to form a loop, called an OX loop. It is shown that one of them, the X line, which is connected with the auroral ionosphere by the lines of force, could be the proximate source of th<e particles that produce the aurora polaris. By postulating the existence of such X-type neutral lines at about 6 earth radii, an explanation is obtained of the detailed morphology of the aurora. This includes the auroral zones and their changes, the nighttime peak occurrence of auroras, their thin ribbon-like structure and their multiplicity, their diffuse and active forms and the transition between them (break-up) the required electron and proton flux, and the ray and wavy structures. Among the most important phenomena associated with the sudden change of the aurora from the diffuse to the active form are the simultaneous appearance of the auroral electrojet and the resulting polar magnetic disturbances (DP sub-storms). Several typical DP sub-storms are studied in detail. It is concluded that a westward auroral jet is produced by a southward electric field. It is shown that an instability of the sheetbeam issuing from along the X-type neutral line can produce a southward electric field of the required intensity. The southward electric field produces an eastward motion of the electrons in the ionosphere. This may be identified with the eastward motion of an active aurora and with the westward auroral electrojet. Besides such large changes- of the field, there often appear various quasi-sinusoidal changes of the field, much less intense. They are supposed to be hydromagnetic waves, some of which are generated in the outer atmosphere and propagated through the ionosphere, where a certain amount of their energy is dissipated. It is concluded however that Such a dissipation is not sufficient to produce any appreciable heating of the ionosphere.Chapter I The electromagnetic environment of the earth : The solar system in the Galaxy ; The sun and the interplanetary space ; The outer atmosphere, the Van Allen radiation belts and the ionosphere ; The earth’s permanent magnetic field ; Introduction to geomagnetic storms and auroras ; The analysis of the earth’s magnetic field – Chapter II The sudden commencement of magnetic storms : Introduction ; The studies of Sc and Si at individual observations ; A theory of the Sc of magnetic storms ; Transmission of the Sc from the inner boundary of the solar steam to the earth’s surface ; The sudden commencement DP currents – Chapter III The ring current and the van allen radiation belts : Introduction ; The motion of charged particles in the earth’s dipole magnetic field ; Electric currents in an ionized gas (general formulae) ; The steady ring current in a dipole field ; The magnetic field produced by the ring current ; The main phase of magnetic storms ; The ring current belt ; Discussion – Chapter IV A neural line discharge theory of the aurora Polaris : Introduction ; The formation of a neutral line ; The motions of charged particles close to a neutral line ; The auroral zones ; Particle injection associated with arcs ; Rayed arcs ; Instabilities of auroras – Chapter V Polar magnetic disturbances : Introduction ; The polar magnetic disturbances of 5 to 6 December 1958 (College, Alaska) ; The polar magnetic disturbances of 29 September 1957 (Worldwide) ; The polar magnetic disturbances of 23 September 1957 ; The eastward motion of auroras and the electric field of polar magnetic disturbances ; The origin of the electric field of polarmagnetic disturbances – Chapter VI Hydromagnetic waves in the ionosphere : Introduction ; Ionospheric heating by hydromagnetic waves connected with geomagnetic micropulsations – Acknowledgements -- ReferencesYe

New Theory of the Aurora Polaris

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77559/1/AIAA-5630-904.pd

Note on a supposed determination of the lunar diurnal tide in the ionosphere

Since Newton founded and Laplace developed the gravitational theory of the tides, the somewhat concealed tidal influence on the atmosphere, as well as the obvious oceanic tide, has been much studied [2]. Later these studies were extended to the ionosphere, first by Appleton and Weekes [3]. Hitherto only the semidiurnal lunar tide has been found in the atmosphere; the diurnal tide predicted by theory, reversed fortnightly when the moon crosses the equator, has never yet been detected in meteorological data; all claims to have done so have proved fallacious. In the ionosphere the semidiurnal tide is far larger than the oceanic or lower-atmospheric tides; hence the hope of detecting the lunar diurnal tide is brighter there than elsewhere. The purpose of this note is to show, however, that a recent announcement by Jones and Jones [4] of its detection in the F layer at College, Alaska, is not well-founded; this does not imply that it may not exist there and be determinable

Electrical Cable Design for Urban Air Mobility Aircraft

Urban Air Mobility (UAM) describes a new type of aviation focused on efficient flight within urban areas for moving people and goods. There are many different configurations of UAM vehicles, but they generally use an electric motor driving a propeller or ducted fan powered by batteries or a hybrid electric power generation system. Transmission cables are used to move energy from the storage or generation system to the electric motors. Though terrestrial power transmission cables are well established technology, aviation applications bring a whole host of new design challenges that are not typical considerations in terrestrial applications. Aircraft power transmission cable designs must compromise between resistance-per-length, weight-per-length, volume constraints, and other essential qualities. In this paper we use a multidisciplinary design optimization to explore the sensitivity of these qualities to a representative tiltwing turboelectric UAM aircraft concept. This is performed by coupling propulsion and thermal models for a given mission criteria. Results presented indicate that decreasing cable weight at the expense of increasing cable volume or cooling demand is effective at minimizing maximum takeoff weight (MTO). These findings indicate that subsystem designers should update their modeling approach in order to contribute to system-level optimality for highly-coupled novel aircraft. Mobility (UAM) vehicles have the potential to change urban and intra-urban transport in new and interesting ways. In a series of two papers Johnson et al.1 and Silva et al.2 presented four reference vehicle configurations that could service different niches in the UAM aviation category. Of those, this paper focuses on the Vertical Take-off and Landing (VTOL) tiltwing configuration shown in Figure 1. This configuration uses a turboelectric power system, feeding power from a turbo-generator through a system of transmission cables to four motors spinning large propellers on the wings. Previous work on electric cable subsystems leaves much yet to be explored, especially in the realm of subsystem coupling. Several aircraft optimization studies1, 3, 4 only considered aircraft electrical cable weight and ignored thermal effects. Electric and hybrid-electric aircraft studies by Mueller et al.5 and Hoelzen et al.6 selected a cable material but did not investigate alternative materials. Advanced cable materials have been examined by a number of authors: Alvarenga7 examined carbon nanotube (CNT) conductors for low-power applications. De Groh8, 9 examined CNT conductors for motor winding applications. Behabtu et al.,10 and Zhao et al.11 examined CNT conductors for a general applications. There were some studies that examined the thermal effects of cables but they did not allow the cable material to change; El-Kady12 optimized ground-cable insulation and cooling subject constraints. Vratny13 selected cable material based on vehicle power demand, and required resulting cable heat to be dissipated by the Thermal Management System (TMS). None of these previous studies allowed for the selection of the cable material based on a system level optimization goal. Instead, they focused on sub-system optimality such as minimum weight, which comes at the expense of incurring additional costs for other subsystems. Dama14 selected overhead transmission line materials using a weighting function and thermal constraints. However, that work was not coupled with any aircraft subsystems like a TMS. The traditional aircraft design approach, which relies on assembling groups of optimal subsystems, breaks down when considering novel aircraft concepts like the tiltwing vehicle. In a large part, this is because novel concepts have a much higher degree of interaction or coupling between subsystems. For example, when a cable creates heat, this heat needs to be dissipated by the TMS, which needs power supplied by the turbine, and delivering the power creates more heat. The cable, the TMS, and the turbine are all coupled. A change to one subsystem will affect all the other subsystems, much to the consternation of subsystem design experts. Multidisciplinary optimization is the design approach that can address these challenges. However, to fully take advantage of this, we must change the way we think about subsystem design. Specifically, we must move away from point design, and focus on creating solution spaces. The work presented in this paper uses the multidisciplinary optimization approach with aircraft level models to study the system-level sensitivity of cable traits: weight-per-length and resistance-per-length. Additionally, we examined the effects of vehicle imposed volume constraints on these traits. This is useful for three purposes: (1) to demonstrate a framework that can perform a coupled analysis between the aircraft thermal and propulsion systems, (2) to provide a method by which future cable designs can be evaluated against each other given a system-level design goal, (3) to provide insight into what cable properties may be promising for future research. This last element is explored given the caveat that the models contained in this analysis do not represent high-fidelity systems. Thus, while we can demonstrate coupling in between systems, the exact system-level sensitivity to a given parameter may change if a subsystem model or the assumptions governing that model change. The organization of this paper is as follows, in Sec II we outline a method to combine the VTOL vehicle design and cable information in order to produce cables sensitivity studies. Results analysis and discussion are contained in Sec III. Conclusions are presented in Sec IV