Outer Magnetospheric Boundaries

by Paschmann, G.; Schwartz, S. J.; Escoubet, C. P.; Haaland, S.

• ISBN13: 9781402034886
• ISBN10: 1402034881
• eBook ISBN(s): 9781402045820
• Format: Hardcover
• Copyright: 2005-12-07
• Publisher: Kluwer Academic Pub
• More Book Details
• Purchase Benefits

Summary

When the stream of plasma emitted from the Sun (the solar wind) encounters Earth's magnetic field, it slows down and flows around it, leaving behind a cavity, the magnetosphere. The magnetopause is the surface that separates the solar wind on the outside from the Earth's magnetic field on the inside. Because the solar wind moves at supersonic speed, a bow shock must form ahead of the magnetopause that acts to slow the solar wind to subsonic speeds. Magnetopause, bow shock and their environs are rich in exciting processes in collisionless plasmas, such as shock formation, magnetic reconnection, particle acceleration and wave-particle interactions. They are interesting in their own right, as part of Earth's environment, but also because they are prototypes of similar structures and phenomena that are ubiquitous in the universe, having the unique advantage that they are accessible to in situ measurements. The boundaries of the magnetosphere have been the target of direct in-situ measurements since the beginning of the space age. But because they are constantly moving, changing their orientation, and undergoing evolution, the interpretation of single-spacecraft measurements has been plagued by the fundamental inability of a single observer to unambiguously distinguish spatial from temporal changes. The boundaries are thus a prime target for the study by a closely spaced fleet of spacecraft. Thus the Cluster mission, with its four spacecraft in a three-dimensional configuration at variable separation distances, represents a giant step forward. This 20th volume of the ISSI Space Science Series represents the first synthesis of the exciting new results obtained in the first few years of the Cluster mission.

Table of Contents

Foreword	ix
Introduction	1	(6)
Part I SOLAR WIND, FORESHOCK, MAGNETOSHEATH
1. THE NEAR-EARTH SOLAR WIND	7	(34)
1.1 The Solar Wind at 1 AU	7	(8)
1.1.1 Waves and turbulence	9	(4)
1.1.2 Studies using Cluster	13	(2)
1.2 Solar Wind Structures	15	(14)
1.2.1 The heliospheric current sheet	15	(4)
1.2.2 CMEs and magnetic clouds	19	(7)
1.2.3 Solar wind discontinuities	26	(3)
1.3 Solar Wind Microstructures	29	(5)
1.3.1 Isolated magnetic holes	29	(2)
1.3.2 Weak double layers	31	(3)
1.4 Outlook	34	(1)
References	34	(7)
2. THE FORESHOCK	41	(54)
2.1 Introduction	41	(7)
2.2 Foreshock Boundaries	48	(9)
2.2.1 Electron foreshock boundary	48	(2)
2.2.2 Internal boundaries in the ion foreshock: Particle observations	50	(4)
2.2.3 Internal boundaries in the ion foreshock: Wave observations	54	(3)
2.3 Upstream Waves and Particles	57	(23)
2.3.1 Low-frequency waves	58	(14)
2.3.2 Origin of gyrophase bunched ions	72	(8)
2.4 Hot Flow Anomalies	80	(5)
2.4.1 Origin	80	(1)
2.4.2 Cluster observations	81	(4)
2.5 Summary	85	(3)
References	88	(7)
3. THE MAGNETOSHEATH	95	(60)
3.1 Introduction	95	(3)
3.1.1 Average magnet osheath properties	95	(1)
3.1.2 Sources of low frequency waves and turbulence	96	(1)
3.1.3 Cluster achievements	97	(1)
3.2 Low Frequency Wave Mode Identification	98	(17)
3.2.1 Introduction	98	(4)
3.2.2 Magnetic wave field energy distribution from k-filtering	102	(3)
3.2.3 Application of the phase difference method	105	(4)
3.2.4 Comparison of k-filtering and phase difference results	109	(6)
3.3 Waves Behind the Quasi-Perpendicular Bow Shock	115	(6)
3.3.1 Observations	115	(1)
3.3.2 Alfven ion cyclotron waves	116	(2)
3.3.3 Filamentary current tubes	118	(1)
3.3.4 Conclusions	119	(2)
3.4 Mirror Mode Theory and Modelling	121	(10)
3.4.1 Brief review of mirror mode theory	122	(1)
3.4.2 Nonlinear static bottle model of mirror modes	123	(2)
3.4.3 Fitting model to data	125	(2)
3.4.4 Case study	127	(4)
3.5 Observations of High-Frequency Waves	131	(8)
3.5.1 Electromagnetic waves: Lion roars	131	(3)
3.5.2 Electrostatic waves: Broadband structures	134	(5)
3.6 Observations of Dispersed Ion Signatures	139	(3)
3.7 Summary and Outlook	142	(4)
References	146	(9)
Part II THE BOW SHOCK
4. CLUSTER AT THE BOW SHOCK: INTRODUCTION	155	(6)
References	159	(2)
5. Q SHOCK STRUCTURE AND PROCESSES	161	(44)
5.1 Introduction	161	(1)
5.2 Structure and Thermalization	162	(23)
5.2.1 Bow shock orientation and global structure	162	(4)
5.2.2 Large- and meso-scale shock structure	166	(4)
5.2.3 Fine-scale features in the electric field	170	(5)
5.2.4 Shock variability and non-stationarity	175	(10)
5.3 On the formation and origin of field-aligned ion beams	185	(12)
5.3.1 Ion distributions at the quasi-perpendicular bow shock	185	(3)
5.3.2 Source and generation of field-aligned beams	188	(7)
5.3.3 Composition of field-aligned ion beams	195	(1)
5.3.4 Discussion on the nature of field-aligned beams	196	(1)
5.4 Summary	197	(1)
References	198	(7)
6. Q SHOCK STRUCTURE AND PROCESSES	205	(18)
6.1 Introduction	205	(2)
6.2 Structure	207	(6)
6.2.1 Overview	207	(2)
6.2.2 Pulsations: Structure and scales	209	(3)
6.2.3 Pulsations: Fields and particles	212	(1)
6.3 Diffuse Ion Acceleration	213	(7)
6.4 Summary	220	(1)
References	220	(3)
7. CLUSTER AT THE BOW SHOCK: STATUS AND OUTLOOK	223	(8)
References	227	(4)
Part III MAGNETOPAUSE AND CUSP
8. MAGNETOPAUSE AND BOUNDARY LAYER	231	(90)
8.1 Introduction	231	(7)
8.1.1 Orientation, motion, and thickness	233	(3)
8.1.2 Magnetopause substructure	236	(1)
8.1.3 Physical properties	237	(1)
8.1.4 Meso-scale phenomena	238	(1)
8.2 Magnetopause Orientation, Motion, and Thickness	238	(14)
8.2.1 Case Studies	239	(12)
8.2.2 Statistical study	251	(1)
8.2.3 Summary and conclusions	251	(1)
8.3 Magnetopause Currents	252	(11)
8.3.1 Measuring the current with the curlometer	253	(3)
8.3.2 Variance analysis of the current density vector	256	(4)
8.3.3 Comparison with average currents	260	(2)
8.3.4 Summary and conclusions	262	(1)
8.4 Structures within the Magnetopause	263	(8)
8.4.1 The magnetopause as an MHD discontinuity	263	(2)
8.4.2 Examples of two-dimensional structure	265	(6)
8.4.3 Summary	271	(1)
8.5 Electromagnetic Fields in the Magnetopause	271	(10)
8.5.1 Background	271	(2)
8.5.2 The intrinsic electric field in a thin magnetopause	273	(2)
8.5.3 Narrow layers inside a thick magnetopause	275	(2)
8.5.4 Electromagnetic waves	277	(3)
8.5.5 Summary	280	(1)
8.6 Flux Transfer Events	281	(13)
8.6.1 Background	281	(2)
8.6.2 Simultaneous multi-point FTE observations	283	(8)
8.6.3 Coordination with ground-based observations	291	(3)
8.6.4 Summary	294	(1)
8.7 Surface Waves	294	(11)
8.7.1 Brief history	294	(2)
8.7.2 Tracking the undulating boundary	296	(3)
8.7.3 Periodic surface waves	299	(5)
8.7.4 Summary	304	(1)
8.8 Boundary Layer Structure and Detached Plasma	305	(5)
8.8.1 Background	305	(1)
8.8.2 Structure inside the boundary layer	306	(2)
8.8.3 Observation of detached plasma	308	(1)
8.8.4 Summary	309	(1)
8.9 Summary and Conclusions	310	(2)
References	312	(9)
9. CLUSTER AT THE MAGNETOSPHERIC CUSPS	321	(46)
9.1 Introduction	321	(5)
9.1.1 Previous work	323	(2)
9.1.2 How Cluster investigates the cusp	325	(1)
9.2 The High-Altitude Cusp	326	(26)
9.2.1 March 17, 2001	328	(4)
9.2.2 February 4, 2001	332	(5)
9.2.3 February 13, 2001	337	(3)
9.2.4 Statistical survey	340	(3)
9.2.5 Waves and turbulence	343	(9)
9.3 The Mid-Altitude Cusp	352	(7)
9.3.1 Structure: Case study	352	(2)
9.3.2 Structure: Statistical survey	354	(1)
9.3.3 Ionospheric ions	354	(3)
9.3.4 Mid-altitude signatures of the LLBL	357	(2)
9.4 Discussion	359	(1)
References	360	(7)
10. MAGNETOPAUSE PROCESSES	367	(58)
10.1 Magnetopause Reconnection	368	(23)
10.1.1 Intermittent vs. quasi-steady reconnection	368	(14)
10.1.2 Component vs. anti-parallel reconnection	382	(3)
10.1.3 Tailward-of-the-cusp reconnection	385	(3)
10.1.4 Quantitative tests of reconnection occurrence	388	(3)
10.1.5 Summary	391	(1)
10.2 Kelvin-Helmholtz Instability at the Flank Magnetopause	391	(5)
10.3 Microphysics of Magnetopause Processes	396	(20)
10.3.1 Collisionless generalised Ohm's law	397	(1)
10.3.2 Ion diffusion region observations	398	(4)
10.3.3 High-frequency waves	402	(3)
10.3.4 Lower-hybrid waves	405	(4)
10.3.5 Low-frequency waves	409	(3)
10.3.6 Anomalous diffusion: Estimates	412	(3)
10.3.7 Conclusions	415	(1)
References	416	(9)
Abbreviations and Acronyms	425	(2)
Author Affiliations and Addresses	427