Author(s) Patterson, John Woodward III.; Olsen, Richard C. Title Observations of a hydromagnetic wave in the earth's magnetosphere. Publisher Issue Date 1987 URL http://hdl.handle.net/10945/22836 This document was downloaded on May 04, 2015 at 21:39:00 1;JDLBT T3 hSTA'L 5 . .:00B NAVAL POSTGRADUATE SCHOOL Monterey , California THESIS OBSERVATIONS OF A HYDROMAGNETIC WAVE IN THE EARTH'S MAGNETOSPHERE by John Woodward Patterson III December 1987 Thesis Advisor: Richard C. Olsen Approved for public release; distribution is unlimited T239127 JNCLASSIFIED OF THIS PAGE ITY CLASSIFICATION REPORT DOCUMENTATION PAGE PORT SECURITY CLASSIFICATION RESTRICTIVE lb j MARKINGS JNCLASSIFIED CURITY CLASSIFICATION AUTHORITY CLASSIFICATION / 3. DISTRIBUTION /AVAILABILITY Approved for public release; distribution is unlimited DOWNGRADING SCHEDULE FORMING ORGANIZATION REPORT NUMBER(S) kME OF PERFORMING ORGANIZATION OFFICE 6b. and ADDRESS 8b. OFFICE (If (City, State, and ZIP Code) Monterey California 93943-5000 93943-5000 GANIZATION and Naval Postgraduate School 7b. kME OF FUNDING/SPONSORING State, NAME OF MONITORING ORGANIZATION 7a. ZIP Code) Monterey, California DRESS (Oty, SYMBOL applicable) Code 61 Naval Postgraduate School (City. State, MONITORING ORGANIZATION REPORT NUMBER(S) 5. (If DRESS OF REPORT SYMBOL PROCUREMENT INSTRUMENT IDENTIFICATION NUMBER 9. applicable) ZIP Code) SOURCE 0= FUNDING NUMBERS 10. PROGRAM PROJECT NO. ELEMENT NO. TASK WORK NO ACCESSION NO. UNIT LE (Include Security Classification) OBSERVATIONS OF A HYDROMAGNETIC WAVE IN THE EARTH'S MAGNETOSPHERE RSONAL AUTHOR(S) Patterson, John W. Ill YPE OF REPORT COVERED 13b TIME aster's Thesis FROM 1 4 DATE OF REPORT (Year, Month. Day) 15 PAGE COUNT 1 " 1987, December TO 1 PPLEMENTARY NOTATION COSATI COOES GROUP ELD 18 SUBJECT TERMS (Continue on reverse if necessary and identify by block number) SUB-GROUP Alfven Wave, Hydromagnetic Wave, Pc5, SCATHA STRACT (Continue on reverse if necessary and identify by block number) Measurements of a continuous hydromagnetic micropulsation event, which occurred in the pre-dawn magnetosphere on July 29, 1979, are reported as observed by wave and particle instruments onboard the P78-2 (SCATHA) spacecraft. Calculations of the Poynting vector make it clear that the wave is a traveling Alfven wave guided by the earth's magnetic field line. Plasma densities are calculated at L = 7. The phase relationship between the plasma flux and the electromagnetic fields is investigated. A selfconsistent set of particle density and particle velocity data is determined, in order Current magnetospheric models to verify the measurement of the electric field. predicting Alfven wave speeds, Alfven wave periods and plasma densities are supported by the study. JTRIBUTION/ AVAILABILITY OF ABSTRACT JNCLASSIFIED/UNLIMITED D SAME AS Q OTIC USERS C. 22b. Olsen >RM 1473, 84 MAR TELEPHONE (408) 83 APR edition All may be 1 UNCLASSIFIED AME OF RESPONSIBLE INDIVIDUAL . ABSTRACT SECURITY CLASSIFICATION 21. RPT. used until exhausted. other editions are obsolete 1 (Include | Area Code) 646-2109 ^2c. OFFICE SYMBOL 1 61-Os 1 SECURITY CLASSIFICATION OF THIS PAGE t> U.S. Gav*rnni«nt Prlntln« Office UNCLASSIFIED 1986—«06-24. Approved for public release; distribution is unlimited Observations of a Hydromagnetic Wave in the Earth's Magnetosphere by JOHN WOODWARD PATTERSON III Lieutenant, United States Navy B.S., PURDUE UNIVERSITY, 1979 Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN PHYSICS from the NAVAL POSTGRADUATE SCHOOL December 1987 ABSTRACT Measurements pulsation of which event, wave and particle instruments Calculations clear that the wave is earth's magnetic calculated at plasma flux A L = a field 7 . onboard P7 8-2 the (SCATHA) Poynting vector make it of the traveling Alfven wave guided by the densities Plasma line. are relationship between the The phase data is set of predicting particle determined, measurement of the electric models pre-dawn the in and the electromagnetic fields is investigated. self-consistent velocity occurred micro- July 29, 1979, are reported as observed by magnetosphere on spacecraft. hydromagnetic continuous a Alfven in field. density order to and particle verify the Current magnetospheric wave speeds, Alfven wave periods and plasma densities are supported by the study. < :'•-. TABLE OF CONTENTS I. II. INTRODUCTION 7 • A. GEOMAGNETIC MICROPULSATIONS 7 B. CONTINUOUS PCS OSCILLATIONS 7 1. Previous Observations 2. Theory 8 11 C. COORDINATE SYSTEMS 12 D. SCATHA SATELLITE 14 1. SCATHA Orbit Parameters 14 2. Instruments 22 OBSERVATIONS A. B. ' 25 PARTICLE AND FIELD DATA 25 1. Magnetic Field Data 25 2. Electric Field Data 29 3. Low Energy Ions 35 A CLOSER LOOK, THE D PACKET 36 1. Field Relationships 36 2. Particle and Field Relationships 40 3. Plasma Parameters 43 4. Electron Density 52 5. Self Consistency of the Data 55 6. The Alfven Velocity 57 7. The Poynting Vector 57 8. Dependence of the Period on L 60 4 III. IV. C. SOLAR AND MAGNETIC FIELD CONDITIONS 6 3 D. OTHER OBSERVERS 63 DISCUSSION 65 A. THE CHARACTER OF THE PCS 65 B. SPATIAL EXTENT OF THE PC5 66 C. UNRESOLVED ISSUES 67 D. RECOMMENDATIONS 67 CONCLUSIONS 69 LIST OF REFERENCES 71 INITIAL DISTRIBUTION LIST 74 ACKNOWLEDGEMENT The author expresses R.C. Olsen, whose unwavering led him his appreciation to Professor scholarly advice patience and through the obstacles of research, and to Dr. T. L. NASA Goddard Aggson, of theoretical and Center, who provided Space Flight technical guidance and support throughout the research. The author is also grateful NASA Goddard Space Flight to Dr. Ledley, of who was the principal Center, investigator for the magnetometer Brian data. Dr. Jack Quinn, of Lockheed Palo Alto Research Laboratory, who provided the ion mass spectrometer data and Dr. Richard Johnson, who principal investigator assistance of who provided Dr. Carl the UCSD for the particle spectrometer. mass Mcllwain and was the The Dr. Sherman DeForest, is also greatly Johnson, also of NASA data, appreciated. A special thanks to Goddard Space Ms. Judy Flight Center, who provided data and state of the art plots which were vital to the of this study. successful completion I. A. INTRODUCTION GEOMAGNETIC MICROPULSATIONS micropulsations Geomagnetic perturbations of which internal of are be generated by solar forces. The gamma, defined as. [Ref. to extremely these gammas of tens 1] ranging and into two main classes. used when magnetic small fields. fractions of from periods approximately 0.1 second to 10 minutes. be divided geomagnetic origin, 10"^ Tesla, is commonly Micropulsations have amplitudes gammas main field. well as magnetic storms, are thought to micropulsations, as measuring They are to long term variations of the Earth's magnetic In contrast field field. the Earth's magnitude of -when compared to the frequency whose amplitude is small variations short-lived generally magnetic Earth's the low are ranging from Micropulsations may Those with regular or continuous patterns are called Pc's and those with irregular patterns The Pi's. system used in this paper categorizing continuous pulsations is described in [Ref. B. 1. 1] CONTINUOUS PCS OSCILLATIONS Micropulsations with have amplitudes near 100 have Table for amplitudes of the the longest gamma, but order 7 periods, PcS's, may generally are seen to of ten to twenty gamma. A group of Pc5's may noted been have Pc5's activity magnetic generally occur 10 minutes last from They days. disturbed very on and absent on days of very low be to to several hours. during the recovery periods of several days which follow moderate magnetic disturbances. [Ref. 1] TABLE 1 CONTINUOUS PULSATION CLASSIFICATION 1 Type Period (sec. Pel Pc2 PC 3 PC4 PC5 0.2 -- 5 5 -- 10 45 150 -- 10 45 -- 150 600 Previous Observations . ground stations Stewart observed disturbance thousands at of micropulsations. what he described Observatory Kew papers have Ground 19th the since been observed have micropulsations Magnetic field from -- ) Century. as [Ref. a great magnetic Since 2]. published been In 1861 concerning station characteristics of Pc5 were summarized by Barfield and McPherron [Ref. 3]. stations report Pc5 ' most s frequently These data indicate that it is common for degrees of longitude. conjugate ground then ' Ground at dawn and dusk. PCS ' s to span 60 Simultaneous observations by magnetic stations suggested a generation mechanism located near the equator. With the advent of satellite exploration in the late 1960 's the understanding of long period micropulsations was 8 geosynchronous by were correlations example, For orbit. magnetometers. satellite of data taken by spacecraft in made were studies Several taken data with furthered established between micropulsation observations in 1967 from Applied Technology Satellite data [Refs. and 3 magnetospheric of (ATS-1) ground station and This analysis showed that the onset 4]. the expansion occurred during the events of 85 percent of phase 1 suggesting that Pc5 substorms, ' could be generated by storm enhanced ring currents. the early data made In correlate energy plasma showed of magnetosphere at Pc5 scientists multiple by magnetic resonance high altitudes [Ref. 5]. mirror instability. A is given by Chen [Ref. on and high with ground station regions that these resonance regions could be began to sensors data field Explorer 45, data, from that plasma available Comparison spacecraft. data 1970 's existed in the It was suggested perturbed by a drift good review of plasma instabilities 6]. ATS-6 provided an early example of combined magnetic field and plasma flow measurements in 1974 [Ref. 7]. multiple sensors it was vector using fields. possible to Using calculate the Poynting measured magnetic fields and inferred electric This case study showed the existence of a standing Alfven wave. Multi-sensor observations have become more common in the past decade. The addition of mass spectrometers brought A recent example to magnetospheric research. new dimension 1982 [Ref. is a Pc5 observed by Dynamics Explorer I in July Using a mass spectrometer, electric field and magnetic 8]. compare simultaneous field measurements, it was possible to measurements the of E B drift velocities and particle X derived plasma drift velocities during plasma shown was perpendicular rotating be to The event. Pc5 a to the Complete analysis of the plasma data showed magnetic field. that significant quantities of singly ionized helium, oxygen and nitrogen, as plasma, which well in the plasma theory and in matching was important present were hydrogen, as observations. GEOS-2 data from experiment have been reported for Pc5 [Ref. 9]. plasma ' s observed during 1979 Observed correlations between density were data electric field probe double the wave amplitude and to support current hydro- used magnetic wave period models. Multi-satellite observations can be the spatial structure of data from the SCATHA, GOES were used to examine Pc5 s ' 2, GOES Combined magnetic field . 3 the structure observed in November 1979 [Ref. 10]. the wave had an and GEOS 2 satellites of a field aligned Pc5 The study showed that antisymmetric standing structure along the field line, and that the field line. used to address the wavelength was much shorter than These are characteristics that have not yet been explained by existing theories. 10 Analysis determination wave of leading observations, these of enhance propagation characteristics, characteristics and growth modes, the to understanding of the basic plasma physics and those processes which determine the dynamics and structure of the magnetosphere. Theory 2. H. Alfven showed, in propagate electromagnetic waves conductivity in the presence [Ref. can low that 1942, fluids in high of constant magnetic field of a 11]. These waves are difficult to observe on scale. to frequency S. occur Lunquist determined that for between a laboratory strong interaction a electromagnetic and hydrodynamic systems the criterion which must be met is BLo(y/p)l/2 where B is the magnetic field, >> (1.1) 1 the dimension L is conducting fluid, o is the conductivity and of the fluid magnetosphere [Ref. Since 12]. are large, this is the density dimensions the type p of of the of the interaction is possible. In a Newtonian fluid, density p, of perfect conductivity and small perturbations of the magnetic field, Bq, will propagate magnetic field line with velocity along the given by Va = co/]c = Bq 11 / (yoP)^^^ (1-2) which is called the Alfven velocity [Ref. 6]. to the In 1952, Alfven compared hydromagnetic waves vibrations of its' ends fixed at with string elastic an of the Wilson [Ref. 14]. Sugiura and given by analogy is good summary A magnetic field conjugate points [Ref. 13]. The derivation of this analogy is described showing that the plasma acts as the The calculation of mass of the string. perturbation modes of these string vibrations, as applied to the earth's magnetic field, is presented. Hasegawa and Chen separate the theory of long period micropulsations into two categories for each type [Ref. One type 15]. resonant Alfven wave excited at Kelvin-Helmholtz a forth and set can be explained as a local the second type is interpreted as an excitation Kinetic Alfven Wave, by a magnetopause. at a line field instability eigenmode, theory a of a The surface excited by an impulse energized ring current. exhibits Its paper this In some source is a event Pc5 characteristics believed to is described which of a classical Alfven wave. be the current ring which generates a traveling wave along the magnetic field line. C. COORDINATE SYSTEMS The coordinate systems pertinent to this analysis of the Pc5 data are shown in Figure 1. The magnetic field com- ponents (Bx,By,B2) are described in topographic coordinates. X is defined as North, Y points East, 12 and Z points down, SOLAR ECLIPTIC SYSTEM DUSK DAWN SATELLITE SYSTEM Figure 1. Coordinate Systems 13 toward the center of the earth, in the radial direction. The electric are despun into two components field data The X (Ex and E2) of the solar ecliptic coordinate system. this system direction in is parallel to the earth-sun line The Y axis and points in the sunward direction. is perpen- The dicular to the earth-sun line and points toward dusk. Z axis is right-hand perpendicular to the X-Y plane. The satellite coordinate system is a rotating coordinate system with X pointing in the direction of the satellite spin axis, which is essentially held constant throughout the orbit. The spin axis is nearly anti-parallel to Y (SE) Y and Z axis rotate through . The perpendicular to the the plane spin axis. D. SCATHA SATELLITE The U. S. Air Force P78-2 satellite was launched into a near-geosynchronous orbit in January 1979 as part of a joint NASA/Department of Defense program to Charging At High Altitudes (SCATHA). SCATHA vehicle is shown in Figure 1. A study Spacecraft schematic of the 2 SCATHA Orbit Parameters The SCATHA orbit is elliptical with a perigee of 5.5 Re and an apogee of 7.7 Re. 7.5 degrees and the The inclination of the orbit is period is spin period is 59.5 seconds, with 23.5 hours. a spin axis in plane and perpendicular to the earth-sun line. 17] 14 The satellite the orbit [Refs. 16 and UCSO PLASMA DETECTOR HSRWARO END GSFC MAGNETOMETER SCATHA SPACE VEHICLE(P78-21 Figure 2. Schematic of the SCATHA Satellite 15 Figure the earth's center in earth radii, Figures 4 and show the 5 SCATHA's in inclination orbit is a hours 7 and longitude latitude is result of the 7.5" a variation The The constant. nearly remain in longitude fact that the orbit is not geosynchronous The result continuous of the apogee, to 3.74 km/s, slightly elliptical wide sector of the but change in the satellite's geographic velocity SCATHA's , slighly inclined elliptical longitude as well as it's velocity and radial the earth. to 4 During the Pc5 event the geographic orbit. the in reflects the elliptical. 6378 km), for the = geographic latitude longitude and variation Re continuous decline in SCATHA's radial distance. a during the same period. latitude (1 The Pc5 is observed from 24 hours of Day 210. UT during distance from shows the satellite's radial 3 at varies from perigee. distance from 2.55 km/s, at virtue The of this orbit is that the satellite can sweep a earth's magnetosphere while introducing only small errors in the raw magnetospheric data. analysis of In the lite's location important in magnetospheric data, the satel- relative to the earth's the classification first approximation of magnetic field is of observed the shape of the phenomena. A earth's magnetic field is that of a dipole given by R = r sin^e where r is the distance from 16 (1.3) the earth's center to the SCATHA DAY 210 7.8 7 - W 6.8 - < 6.6 H PERIOD OF INTEREST Eh Q 6.2 H H 6 H S 5.8 H Q 5.6 H 5.4 5.2 O 4. -r 8 — —r- T 12 16 20 HOURS UT Figure 3. Radial Location of SCATHA on July 29, 1979 17 24 SCATHA LATITUDE ^ 8 7 - 6 - 5 - W 4 - Da cc 3 - w Q 2 - ^ 1 - -1 - E-« O C/2 o PERIOD OF INTEREST ca Q Z3 E-t M -2 < -3 U -4 M X -5 < -6 u -7 o w u -8 - E-t - - 1^ I 4 8 12 16 20 HOURS UT Figure 4. Geographic Latitude of SCATHA on July 29, 1979 18 24 SCATHA LONGITUDE < 375 - 370 - w O 365 W P - 360 - W P 355 - c/3 ^ ^-—^ / \ / / E- S 350O •J 345 - 340 - U H ffi \ \ < g 335O w O 330 - \ \ T \ PERIOD OF / INTEREST / ,/ r 'I ! ' r- T 12 B T- 1 , 16 r- 20 i - 24 HOURS UT Figure 5. Geographic Longitude of SCATHA on July 29, 1979 19 the dipole intersection of plane. are R and field line. the polar coordinates of the magnetic The parameter used to define the location number of earth radii at which to the is equal of the the L magnetic field, dipole approximation for the of a Using the line is the Mcllwain L [Ref. 18]. magnetic field field line with the equatorial field line value of L the field line crosses the equatorial plane. The at other latitudes is given by L = Re / (1.4) cos^ej^ where 6^ is the magnetic latitude. A view of the magnetic field dipole approximation is shown in Figure are plotted. 6 where field lines for L 5, 6, 7, and 8 Scatha's dipole magnetic position between 0400 At UT and 0700 UT is plotted. 8.03 and = descended to L = 0400 UT 6.59 at SCATHA was 0700 UT. at L = It is during this period that the Pc5 was observed. The dipole approximation field is most exact the earth's magnetic at dawn and dusk. The approximation is fairly inexact at noon (where the poor at for midnight (where field is compressed) and the field is extremely elongated). The distortion of the earth's magnetic field is to the solar wind. largely due A more exact description of the shape of the magnetic field is given by Hess [Ref. 19]. 20 I O I t I t B 2 RE Figure 6. A SCATHA POSITION AT 0700 UT O SCATHA POSITION AT 0^00 UT Mcllwain L and Geomagnetic Latitude of the Pc5 21 2 Instruments . spacecraft The meters in approximately 1.75 cylinder a length and diameter. The instruments used in this Goddard Space Flight Center mag- NASA the monitor, Center electric Flight Space Goddard NASA study are the field is netometer and the University of California, San Diego (UCSD) instruments are shown in Figure consists of two antennas The antenna that measurable field 50 detector field meters in length are used as floating wire is composed of beryllium copper. electric ambient is 0.05 for the last 20 meters, Differential signals between the the active part. antennas give the are these of 17] electric Each antenna is insulated except which is [Ref. plane which projecting into the spin probes. 2. Goddard NASA The a. locations The experiment. particle charged fields The minimum . time resolution of the mV/m. The electric field measurements is limited by the satellite spin period (59.5 seconds). SCATHA data are despun into the X and components of the solar ecliptic (SE) coordinate system. this field method (Ejj the two components and E^), which are the satellite spin axis Z By of the measured electric in the plane perpendicular to are known. It will be shown that the E2 component of the field data reflects the component of the Pc5 electric field which is perpendicular to the earth's magnetic field when the satellite is 22 near local dawn. The transformation from measured the fields sunward field to fields requires the addition of a 0.3 mV/m account for satellite motion. The b. meter a 4 [Refs. form and despun in raw 16 and 17] The c. particle charged UCSD electrostatic analyzer are Data per second. vector measurements with four three vectors listed of the topographic coordinate into the flux. The resolution is boom. from the GSFC magnetometer are used system. 16 and 17] is a triaxial flux gate magnetometer GSFC magnetometer mounted on 0.3 gamma [Refs. the ambient to experiment is an both ion and electron that measures Particle data from the electrostatic analyzers (ESAs) used to functions and the ion electron distribution and particle density, temperature and deduce the The UCSD particle detectors consist of velocity. arranged measure rotating two in detectors, and pairs of electron All ion detector. one fixed five ESAs and ion three of the sensors of this instrument are contained in a single pac]cage mounted on the forward end of the satellite. [Refs. 16 and 17] One pairs of rotating detectors covers the of the energy range from 1 The other E/W detectors) cover the pair (the 1 eV to 81 keV (the and the fixed detector eV to 1800 eV energy range. energy resolution of 20% one 64 step energy scan. (6E/E) [Refs. 23 N/S detectors). The analyzers have and require 16 seconds for 16 and 17] A more complete description of contained in the IMS the satellite Source Book Technical Report [Ref. 21]. 24 and [Ref. instrumentation 20] is and the P78-2 II. A. OBSERVATIONS PARTICLE AND FIELD DATA During the morning hours 210 SCATHA recorded a of Day disturbance in the earth's magnetic field, beginning at the spacecraft 7.96, as of its orbit, micropulsation, a approached the maximum inclination Pc5, strong A degrees. 7.5 L = field on each of SCATHA 's recorded was magnetic sensors Figure is an equatorial plane 7 orbit are The sector line. shown with . of the orbit, in which the Pc5 event was recorded from 8 shows 0300 UT the SCATHA to 0800 UT. magnetic field, Bq, and the three the field (Bjj,By,B2). magnetic field data Included are the total topographic components of The significant rise in the magnitude of Bq, the total field, and earth's 7. Magnetic Field Data Figure due to the earth sun respect to observed, is also indicated in Figure 1 SCATHA 's orbit The location of the extremes of on July 29, 1979 (Day 210). the SCATHA plot of Bj^, the northerly component, is the continuous descent of the spacecraft through the magnetic field for that period of it's orbit. During that time period, SCATHA 's radial distance diminishes from 7.3 Re to 5.3 Re, and L decreases from 8.28 to 6.16. 25 SCATHA DAY 210 ORBIT Z O O z Z^ = FIRST OBSERVATION OF THE PCS e+ = MAXIMUM INCLINATION OF THE ORBIT Z7 = LAST OBSERVATION OF THE PC5 = s e- = s Q € w Figure 7. ORBIT CROSSES EQUATOR PERIGEE MINIMUM INCLINATION OF THE ORBIT APOGEE Equatorial Plane Plot of SCATHA Orbit 26 DAY 210 MAGNETIC FIELDS 220 HOURS UT Figure 8. Magnetic Field Data from 27 300 to 0800 UT EAST-WEST MAGNETIC 5.2 FIELD ( 5.6 HOURS UT Figure 9 . The Pc5 in the East-West Component of the Magnetic Field 28 By 6.8 ) amplitude The magnetic field, B^, varies from to 4 1 the largely due to of the earth's main magnetic field vector in the the tilt The perturbations in B^ are a result of direction. component of the east-west plot of small the field. By, 4:16 UT and continuing until just before dawn, beginning at Since the perturbations in 06:56 UT. a Z The Pc5 is observed component of the Pc5 in that direction. in the of gamma during this component is The magnitude of this period. component radial the of are small, and B^ Bj^ the Pc5 event is largely contained in By. The By Figure expanded in data are 9 for the time A charac- period 0400 to 0700 UT (2:14 to 5:21 local time). teristic of which makes it fairly unique, is the this Pc5, packetized nature pulsations. of the These packets imply different regions of hydromagnetic resonance in the magnetosphere. The packets labelled are A through venience in follows. The period of the pulsations decreases It will comparison be shown the to E for con- electric field data which with time. that the period is a function of L and of the particle density. 2. Electric Field Data Figure 10 is measured by SCATHA a plot from of the electric 300 to 0800 UT. earlier, the electric field data is despun ponents of Ej5 the solar component points in field data As mentioned into two com- ecliptic (SE) coordinate system. the sunward 29 direction The and remains DAY 210 ELECTRIC FIELDS HOURS UT Figure 10. Electric Field Data from 0300 to 0800 UT 30 almost constant at 1.5 mV/m throughout the event value of been added to the from E^). separate E^ through motion SCATHA's relative component is This in order to Figure 10, in E^, a result of the- plasma, the mV/m has (2 the static convective electric field, the sunward electric field caused partial projection by photoemission [Ref. 17] and a of the Pc5 electric field perturbation vector in the X direction. The component E2 to the solar This component is nearly equal to the total ecliptic plane. electric field perpendicular is component of the Pc5 A -0.4 3 mV/m offset . seen in the data is attributed to error fields and a steady state convective field. Figure 11a is an expanded plot of E^ from 0400 UT to The packetized nature 0700 UT. pulsation is venience, the reflected the in electric field the magnetic field seen in electric field. data is resonance packets as listed in Table For con- seperated into named 2. TABLE 2 HYDROMAGNETIC RESONANCE PACKETS Packet t begin t end (hours UT) A 4.41 5.03 5.65 6.10 6.63 B C D E The component of the results from a perturbation in By 31 4.90 5.46 6.02 6.40 6.95 electric field, Ep, which (topographic coordinates). ELECTRIC FIELD FIG. 2 o _ 1 -4 ( Ez ) 11a B n E-« O ^-wV/l/VvVi, > H I ii ir\Arv lA f-VV^i '^; »i H -2 - -^ T T r T ^ r T r 39.7 eV IONS Q - FIG. S -1 7 - lib CO Pm O O •J 5 HOURS UT Figure 11 Measured Electric Field and Low Energy Ion Distribution Function Showing Modulation of Ion Flux by the Field 32 should perpendicular be both to coordinates) is believed to be electric that there can component no be projection of a E^ Bq. (SE Ep onto the This is based on the assumption antenna. field and By electric field the of sustained in the direction of Bq. 6E The electrons magnetic in plasma a line field Bq = • (2.1) free are quickly and move along the to reduce potential any difference which might be impressed along that direction. shows the geometry for extracting Ep from Figure 12 E^. Here a is the angle between the B-^ from geographic latitude solar the ecliptic also the Bq and and the radial direction and Ep. satellite's inclination angle between and is the sum of (3 the satellite's plane. The angle ^ between E^ and Ep is given by Table factors, UT. z, The 3 5 = 90 - (a + p) (2.2) Ep - E2 cos (2.3) / these lists 35 angles and the correction for calculating Ep for the hours of 0400 to 0700 worst value case correction factor in Table E = |Ep| - 1 / IE2I 33 60 percent. The is used as follows: z, 3, only is cos ^ • Z (2.4) a ANGLE BETWEEN MAGNETIC FIELD LINE AND Bx S INCLINATION OF EARTH AXIS ON DAY ElO (IB.^o) e GEOGRAPHIC LATITUDE OF SCATHA SPACECRAFT a INCLINATION OF SATELLITE FROM SOLAR ECLIPTIC a (e + S) © 90 - (a Ep Figure 12. AT LOCAL MIDNIGHT AT LOCAL DAWN a) Ez/cos $ Calculation of 34 E. TABLE 3 CORRECTION FACTORS FIELD DATA ELECTRIC t a (UT) ^ p (degrees The factor which most affects the magnitude of this correction is the shape of different locations projected onto a, the E^ antenna. extremely elongated giving perpendicular field is Near midnight the field is large angle between Bq a and thus a small angle between E and the Z field, During is small. with this a Bj^, At dawn dipole and so the analysis of the electric correction small and antenna. the magnetic field most closely approaches this angle field at It can be seen in Figure of the less magnetic earth's the in the orbit. for small 12 that, 1.04 1.08 1.11 1.20 1.29 1.43 1.63 16.4 21.9 25.5 33.5 39.0 45.6 52.1 19.2 18.0 16.7 15.2 13.4 11.5 9.2 54.4 50.1 47.8 41.3 37.6 32.9 28.7 0400 0430 0500 0530 0600 0630 0700 mind, in the actual electric field data will be assumed to represent the perpen- dicular electric field (E2 3 . • Ep) Low Energy Ions Figure lib shows a plot of the log (base 10) of the distribution function of the 39.7 ev ions measured from 7 hours UT. The Pc5 can be seen in the ion flux. 4 to A comparison of this plot with the electric field shows that the ion is 39.7 ev flux modulated 35 in phase with the This reflects the the electric field, SE^- perturbation of electric field. convective drift induced in the ions by the Higher are also modulated, as electrons and ions energy the of shown in the expanded presentation packet which D follows B. A CLOSER LOOK, THE D PACKET Since the at 6 this time SCATHA is the region is hours UT and ends at 6.4 hours UT. 1 a =6.97 and average The D packet is orbit. the period of 17.23 minutes. at L time SCATHA 's of was During this After km/sec. 3.25 taking into account the decrease in SCATHA* s radial position appears to span resonance packet through this period, this of this The center at 4:21 local time. velocity At recently passed North, having at 7.3° inclination maximum observed for . This closer analysis. amplitude fields, it was chosen for packet begins largest the exhibits packet resonance D an arc of 3300 kilometers. 1 . Field Relationships Figure 13 shows versus time for the D packet. E leads B by an average of spline fitted plots Within of 130° average period of the pulsations is are used since the periods changing, as if the fields are or non-harmonic force. from 0.62 to 1.8 mV/m. and E^; and By the resonance region, ±10°, (- 3tt/4), 224 seconds. and the Averages phases are continuously driven by a multi-frequency The electric field amplitude varies The magnetic 36 field amplitude varies ?3 ^8 3NndS Figure 13. 3NndS Pc5 Electric and Magnetic Fields (D Packet) 37 from gamma 6 to The large amplitudes at the gamma. 12 resonance in center of the packet distinguish the center of this region. The perpendicular to vector of the Pc5 lie in a plane magnetic the earth toward and away from radial direction and the were in difference of -tt would If east-west direction. wave would be propagating in phase the will exhibit The magnetic direction. +Z (SE) tt/2 line). magnetic field the -X direction (south along the standing wave direction between the in a field vector pulsates in a nearly the fields the main The electric field vector pulsates line. field and the magnetic field vector field electric difference. phase indicate wave the A A phase is propagating northward. The average fields in phase of This implies that the wave is not a Figure 13 is 37t/4. pure propagating wave. The continuously changing phase of the fields and the motion through of th? spacecraft different of resonance regions make the phase interpretation somewhat ambiguous The complexity of the phase relationship is born out by a phase hodogram plot of 6E2 versus 6By in Figure 14. In a hodogram a the D packet. propagating wave would give a diagonal line, and a standing wave a circle (if E plotted in that the nearly Volts/meter and wave is linear. Tesla). propagating at At other times 38 and B are This hodogram implies times, where the plot is it shows the phase of a Figure 14. Phase Plot of the Pc5 Electromagnetic Wave (D Packet) 39 average phase of 3it/4 more circular. plot becomes standing wave, where the The is reflected in the overall elliptical nature of the plot. Hence, the slope of E and B are related by E = ^^B. a line, V(t). or the inclination of an ellipse, in Figure 14 gives The slope of the major ellipse (mv/m) is 0.15 3 / (gamma) which gives a phase velocity of 153 km/sec. 2. Particle and Field Relationships analyzers electrostatic obtained for ' measured were the and by distribution energy energy levels every 16 seconds. 63 versus time Figure 15 contains plots of the log^g ^ for low the UCSD and electron fluxes are Ion calculated. were functions rates count Particle energy ions, high energy electrons, and two sets of high energy ions measured between 6.1 UT and 6.4 UT. The data sets chosen were from energy levels which exhibited the highest particle count rates. This was done in order to minimize the statistical error. A plot of log F versus time shows the fluctuations in the energy of the ions with time. The main cause of the change in the kinetic energy of the low energy ions is the E X B force, which is generated by the Pc5 wave. packet region the magnetic mately 140 gamma. field strength, Bq, In the D is approxi- Hence, a 2.6 mV/m electric field should give the plasma an E X B drift velocity equal to V£) = 6E2 X Bq / |Bo^ 40 I 18.6 km/sec (2.5) HOURS UT 6. 6.^ 1 FIG. 15b 9.3 keV IONS 0.^ Cm O O 0.0 FIG. 15c ^.7 keV ELECTRONS E.O Figure 15. Ion and Electron Distribution Functions 41 Table 3 electric field of the Here the upper limit values is used (6E corrected with z) • If the plasma flow is perturbed by a change in the fields, then the kinetic energy is given by U = 1/2 m (V - Vd)2 = where V 1/2 m (V2 - particle and is the V 2 (2.6) Vi5 cos e + Vq^) If V >> v^ the E X B flow. Vj^ (which is true for 40 ev ions) and, if 9 = 0, then Equation (2.7) can be expanded U = 1/2 m (V - Vd)2 - 1/2 the If mv2 particle - (2.7) (m V v^) distributions energy were Maxwellian, they could be represented by F = n (m/27TkT)3/2 exp -(U/kT) (2.8) and by Equation (2.7) log F = constant + (log e) Hence, the plot of log F for 40 tional to V£). (mV/kT) out plotted). of v^ is propor- ev ions Comparision of 39.7 ev ions with the electric field in Figure 15a shows this to be the case. is • phase with the electric The phase difference with field by the electric due to the unidirectional counting of the ESA's. 42 The ion flux tt (-E^ is field is Since they the positive are looking in the direction of the count induced the by E X change in force. B B force, Thus, the maximum when 6E2 is negative. rate is low energy ion flux is modulated by the energy E X the flow The higher energy particles respond primarily to B [Ref. 22]. Figure 15b shows that modulated higher energy in Hence, the changes in of course, velocity the 9 . 3 ions are effectively magnetic field data. the particles are, change small' with phase in 9.3 kev These unaffected by the caused by the E X B force. kev ion flux reflect the effective motion of the different magnetic field lines with respect to the satellite. like Figure 15c shows 4.7 kev electrons which, in show manner, flux modulations in with phase the magnetic field. At higher begins to energies the lag the magnetic field. 15d where the flux of the an average field by modulation of of 47.4 kev tt/2. the ion flux This is shown in Figure ions lags the magnetic This difference reflects the large gyroradius (225 km) of these high energy particles. These plasma is comparisons moving with illustrate the point that the the magnetic field lines of force. Hence, the plasma and the field lines oscillate together as if the particles are frozen to the field lines [Ref. 6]. 3. Plasma Parameters The can be plasma determined density, by temperature and flow velocity assuming 43 that ion distribution functions Maxwellian nearly are Maxwellian fitting and distributions to the data. Analysis of the ion population due a multi-species The distribution masses. various the to requires data function becomes = F S Fi = S n^ (mi/2TTkT)3/2 exp -(Ui/kT^) (2.9) and log F for each population is = log F log ( = f(p,T) - (log e = f(p,T) + f(T) U the begin To function of n (m/2TTkT)3/2 (u/kT) log e _ process distribution the data is calculated and a plot of log F the ion As Figure 16 an example. This time was flux recorded by the N/S detector at 6:12 UT. selected because electric field. velocities can it It is is be expected near here that and the satellite potential shadowing the amplitude large a shows a calculated from ion distribution function the ion (2.10) kT) U fitting versus energy is made. plot of / -j in the highest the drift effect of the positive lowest energy ions (H"^) the smallest. In this contain H"^, He"*" assumed, there fitting process and O"*" ions only. are three the plasma was assumed to Once the ion species are unknowns for each species in the distribution function. The temperature, kT, the 44 density, n, o 0t I I H I I M » it t t I t t I I > a m + o o o m > — o o o . + — o o o + 1 150.0 ° 1 1 o + .0 ^ >^ + << o o /^^ -S^ 100.0 t~^ T i ( Figure 16. " ^^ 1 1 gWM / £S ) I J 001 UCSD Ion Distribution Function (0 - 500) eV 45 0) flow velocity, and the is required. A self consistent set of values v. In particular, consistent flow velocities are all ions move together. One additional free required since parameter is the satellite potential. The temperature, approximated to kT, is be 10 ev. In a more distinctly separated energy distribution, each ion species would show a well defined peak and the width of the In the present case, the peak would define the temperature. curvature of the distribution function is of both result a temperature and velocity. Since the be assumed to be looking detector cannot in a direction exactly parallel to 4), must the flow, a look angle, The choice of this angle affects the be included. calculated density and velocity. flow In case 10 this degrees was chosen. A peak in distribution function determines a the velocity, Vp, given by vp where Vq is the introduced selection of in = (2U/m)l/2 = Vq cos plasma drift the calculated the view angle is velocity. velocity 46 Hence, the error by an erroneous proportional to cos error of 15° in the approximation of in Vp of less than 10 percent. (2.11) (t> <t>, will cause <t>. An an error Olsen discusses this process and shows that the error, the calculation introduced in E, , of n is more severe [Ref. 23]. E, exp -(Vd^ «x _ vq^ (2.12) cos2(t)) In Figure 16, the peaks occur at approximately 35 ev and 100 ev. The lower due middle to the H""", ,0"*". energy peak An energy peak. He"*", approximation, Vp, each population velocity of is assumed energy peak 8 ev, to be and the highest the drift for made from the measured can be energy peak. Since V = (2U/m)^/2 Vp H "39 Vp - jjp km/s 41 km/s •35 Vp (2.13) km/s In the example. Figure 16, the data are a Maxwellian 0"^. distribution function for H"*", for He"*" Consistency requires that the Maxwellian plots density ratio. velocity, a The 10 ev values used for this temperature, a fit are He"*" for all and 0"^. The results using UCSD data over the D 35 km/s look angle equal to 10 degrees, and ion number densities 1.0, 0.5, and H"*", and for have the same drift velocity and a reasonable three species for fitted with 0.3 of this fitting process packet are listed in Table 47 (cm"-^) 4. TABLE 4 PLASMA ION NUMBER DENSITY (1-500 ev ( induced by 1.27 ± .67 0.38 + .05 0.30 ± .10 35 ± 5 35 ± 5 35 ± 5 Total 1.95 ± .73 - of The such a flow - the flow convective flow is It is 1 - 10 state electric field responsible for steady (0.2 both steady background flow. and the the PCS 35 contains km/sec 35 estimated that the background km/sec. (km/sec) cm" 3 H+ He+ 0+ velocity The flow V n Ion mV/m) is 2.0 electric field instrument. poorly measured by the The remaining, pulsation induced flow, is approximately 25 km/sec. From Equation calculated to (2.6), be 18.6 the km/sec. flow velocity near 16.4 km/sec. 140 gamma, is velocity was Bq X This implies a steady state Since 6E = v^ • Bq and Bo = convective electric field as large as 2.3 mV/m a implied 6E2 from throughout the the D packet electric field is consistent Analysis data. with this interpre- tation. An alternative interpretation is the value measured by that the floating probe. 6E is twice Experience with the electric field data by the principal investigator, T. L. Aggson, has suggested problems 48 with the amplitude of the measured fields. An aggreement within this considered point, is of two, at factor a to be supportive of the direct measurements of E. The complete ion distribution is needed to determine total the The density. ion high energy UCSD data were from the combined with the high energy ion composition data Composition Experiment Energy Ion SC8 High determined average ion densities in the for the H"*" density was (1.974 cm~^}, the (0.089 cm~3} and the a - 500 eV) the total O"*" (0 - 80 kev) ions are part of The average density was He"*" cm~^). The SC8 The line plot in Figure 17 is population. The low energy ions are the same population inferred in Figure by the fitting process of the UCSD data UCSD SC8 21]. 32 kev range to density was (0.398 O"*" shown in Figure 17. plot of log F for (100 eV 1 period from 0600 to 0700 UT. one hour data are . [Ref. ions are shown in Figure 18. the bulk of the The 16. The 10 keV plasma sheet population, while the 47 keV ions are from the tail of the distribution function. The SC8 data with combined are the parameters obtained from the UCSD experiment and reported in Table TABLE 5 PLASMA ION DENSITIES (.01 Ion - 32 KEV) n (cm" 3) H+ He+ 0+ TOTAL 3.24 0.47 0.40 4.1 49 ± ± ± ± .68 .15 .17 1.0 5 HIGH ENERGY IONS 32 ENERGY (KEV) X Figure 17. [HE+] F (PLASMA) SC8 Ion Distribution Function (0.1 - 32.0) keV 50 LOG F ( S^ / KM^ ) » I > ^ o > Q) o •« II I I I *ilitlHI o o m Figure 18. UCSD Ion Distribution Function 51 4. Electron Density The calculation on the distribution function large error the of population being ion An error in the look angle can introduce nearly Maxwellian. a ion density depends largely of the in Since n. density number the of the electrons should be equal to the number- density of the ions in a plasma, the value of check of a good Rq is the ion density calculations. All the members of the electron population have the same mass, and that unknowns that mass hindered the useful characteristic of sections of Hence, ion calculation magnetospheric distribution the defined slopes known. is is removed electrons . A is that plot have clearly function which identify of the one different energy populations of electrons. In a plot electron distribution function the of versus energy log Fq = log (ng (me/2TTkTe) 3/2^ = c + b Uq _ log e (1/kTe) Uq (2.14) where b is the slope of each section of the distribution function and c is the y intercept. kTe = -log no = 10^ e / / b (me / 52 From Equation (2.14) (2.15) 2tt kTe)3/2 plot Figure 19 is a calculated from electron distribution the of taken at UCSD data Figure 17 are (sec^/km^) versus (keV) The units of 6:12 UT. Correcting for units . (2.16) ng (10^ X 10-24} = / energy sets In Figure 19 two slope intercept By the shown to have density of (9.05 X 10-13 method, the )3/2 kT (ev) of electrons number density a / are identified. 17.5 kev electrons are of 0.007 The number cm'^. the 1.65 kev electrons is shown to be 1.77 cm--^. By expanding the lower energy section of this data two other electron groups were identified. The number densities which were calculated for each set electrons Table of reported in is 6 TABLE 6 ELECTRON NUMBER DENSITY Energy Range Temperature (kev) (kev) 17.50 1.65 0.71 0.12 15 - 80 1.0 - 15 0.2 - 1.0 0.0 - 0.2 TOTAL Hence, the is consistent n with ( cm- 3 0.007 1.77 1.46 0.67 ± ± ± ± .001 3.9 ± .2 .09 .09 .04 calculated ion number density (4.1 cm" 3) the independently density. 53 determined electron LOG F (S^ / Km6 ) e > O < a Figure 19. UCSD Electron Distribution Function (0 - 80) keV 54 5. Self Consistency of the Data It is now to determine whether these important relationship between n, numbers represent a self -consistent B, Since the plasma acts as and v. E circuit on the electric field antenna, a a parallel resistive major concern is to verify the amplitude measurements of E^. equation to deduce the the following Cummings used density of the ambient plasma from field and particle data measured by the ATS-6 spacecraft in geosynchronous orbit n = 6b2 where <m> is / Pq <m> average the relationship is used to (2.17) V£)2 particle investigate the mass [Ref. 7]. This consistency of the ion density calculations. Assuming that 0"*", the plasma is made up of and using the values from Table 6, the ion H"^, He"^ and mass density is given by p = S = p = and where = m^ (2.18) (3.24(1) + .47(4) + .40(16)} mp (11.52 mp) kg/cm^ <m> = p mp n-j^ / n = 2.81 mp 1.672 x 10"^^ kg. 55 Equation (2.17) is then rewritten, v2 = 5b2 V Since |v <m> n iJq 6B / = (Po P)^^^ |6E / Bq = | / | 6E = 6B Bq (6B Bq) mV/m units of 6B and Bq are gamma. In the D packet Bq 6 Therefore (2.19) (Po P)-^^^ 6.4 X 10"3 = where the / 140 gamma = 6By < 12 gamma < (2.20) the magnitude of the electic field inferred by mass density is 5.4 6E < mV/m (2.21) ^1.8 mV/m (2.22) 10.8 < The measured values of 6E2 were 0.62 ^ 6E2 Taking into account the electric field correction factor of 1.43, from Table 4, the magnitude of the perturbed electric field is calculated to be 0.9 These values are Equation (2.21). a < 6Ep < factor A factor of 56 2.6 mV/m of 2 3 (2.23) lower than predicted by could be accounted for if the impedance of the plasma was comparable to the internal (this is roughly impedance of the electric field experiment the case). A small error, not larger than a factor of 2, in the electric field data is implied by the comparison. 6 The Alfven Velocity The velocities. comparison same be can made in terms of The Alfven velocity is V;^ = w/k Bq = / Since Curl E = -dB/dt then ik Ep - -(-ico) and 6Ep/By - (1-2) (Po P)^^^ By = V;^ co/k (2.24) Using upper and lower bounds of the field amplitudes given by Equations (2.20) and (2.23), the Alfven velocity calculated from measured E is 328 km/sec < ^p, < 378 km/sec (2.25) Using the ion density relationship ^A The electric = ^o / (^o P)^^^ = 900 km/sec field data (2.26) appears to be low by a factor of 3 in this comparison. 7 The Poynting Vector The nature of the propagation of the PCS can be seen by examining the relationship 57 of SE^ and 6By. If the micropulsation was a classical plane Alfven wave, then (1/y) E X B S = - (l/Po) - 1 (l/Po) (SEy 5B2 - 6E2 6By) the Poynting vector components of the other which assumes 5E X 6B 6Ey is not measured, but 5B2 is small, so are small. S - 1 In Figure 20 Px = (1/yo) (-5Ez SBy) (2.27) X 10"12 (2.28) (6E2 6By), so S = -1 (1/yo) (Px) watts/m2 The negative values of Px in Figure 20 indicate that the wave is propagating in the +X direction, northward along the magnetic field line. south of 7° N. The fact positive indicates traveling wave, traveling in standing / The wave must have been generated that is superimposed southward the is, at times, zero or micropulsation is not a simple that the but Px on direction. a smaller wave This is the mixed propagating nature inferred previously in Figure 14. And finally, the magnitude of the Poynting vector is calculated Px = |S| (1.8 = mV/m) (1/yo) (-12 gamma) |Px| X 10~12 =17.2 yWatts/m2 58 (2.29) •A m m lO m T 1 3W /Sil-YM (^T-O"^ ^ ^^Z"!^ ^^ xd Figure 20 The Poynting vector (Calculated in the D Packet) 59 u^«o 04 1 presumes This the that measurement field is possible error in 6E, the magnitude of Given the correct. electric the Poynting vector could be as high as 50 yWatts/m^, 8 Dependence of the Period on L . field line and the of the wave [Ref. 24]. Alfven velocity latitude can be The variation of micropulsation period with expressed density. as function a of and L length of the on the The period of the Pc5 depends n, the plasma number [Ref. 25], L^ Re/Be) (Po <^> n/Q)l/2 X = (2tt Bg = 3.12 X 10"^ Tesla • (2.30) Q is proportional to an Alfven wave eigenvalue which is density gradient, and calculated for different values of L, wave type. In a simpler form this equation corresponds to X The SCATHA data can the period of proportional to this = (m/k)l/2 27T , be used to determine the dependence of Pc5 on L. If the period, x, is L"^ log X = log C + m log L (2.31) where C is a constant. Figure 21 shows the average micropulsation period in each resonance determined by packet, plotted against L. linear regression, is 3.96 ± .07. 60 The slope, Hence, the PCS PERIOD VERSUS L 2.7 2.6 - THE PERIOD OF A PCS WAVE IB PROPORTIONAL TO L'* Q O U 2.5 w CO 2.4. o 2.3 - 2.2 0.79 1 1 o.ai T 1 0.85 0.83 LOG Figure 21. T 1 1 [ L 1 0.87 ] Pc5 Period Versus Mcllwain L 61 1 1 O.S9 SCATHA data the theoretical with agreement close in is relationship Having (2.30) verified the (2.32) L^ « X dependence of the period. Equation L mass density predict a is rewritten and utilized to to compare with the previous measurements. p = n <m> For the values = x (T = Be / L^ Rg )2 x (Q 2-n / \1q) (2.33) 224 sec (in the D packet) L = 7.0 Bg = 3.12 X 10"^ Tesla n <m> = 2.514 mp • Q (cm'^) (2.34) Orr and Matthew calculate Q for a toroidal mode wave in plasma density gradients which obey power laws between R^ and r2 [Ref. 25]. 3.6 At L = (for r4) these values are 7 < Q < 4.2 (for R^ (2.35) ) The mass density inferred by Equation (2.33) is 9.05 mp < The measured mass density theoretical relationship n <m> was < 10.56 mp 11.52 law of (cm~-^). is valid for this Pc5 shown that it is substantively valid the power mp (cm~3) the period), 62 by the (2.36) If the (it has been agreement with then the difference between predicted particle density and measured density implies that the mass a density has been slightly overestimated. However, 10 seconds from the deviation of the wave period of only average used period, predicted density mass Equation (2.34), would bring the in with agreement exact into the measured mass density. Since values the eigenvalue theoretical complete aggreement study is not equation from a wave, toroidal the for However, with both derived were results of this mass density with the demanded. strong agreement Q for comparison shows this variables, L and p. The plasma density gradient is the unknown variable. SOLAR AND MAGNETIC FIELD CONDITIONS C. Geomagnetic and Solar Data, published by Geophysical Research, moderately active substorms day, recorded. indicates Kp Forty event there was a period of which a 12 hour = to 3 eight very high magnetic storm ' generally s occur during 5, Day with 210 was by a no magnetic hours prior to the Pc5 magnetic activity in These occurred [Ref. 26]. conditions support the statement Pc5 that the Journal of Jacobs recovery [Ref. 1] that periods following magnetic disturbances. D. OTHER OBSERVERS SCATHA observed the Pc5 at L = 7. Magnetograms from 3 31 degrees east longitude on the National Institute of Polar 63 Iceland (68.2" 39.6° E) (69.0° S say to These more. invariant latitude for L of this = 0600 to 0700 UT. from station time resolution of the ground enough observed at indicate that this event was simultaneously stations these and at Syowa Base, Antarctica 338.3° E) N at Leirvogur, stations ground Research from the conjugate The 7. located at the are stations not clear was data The simultaneous observation imply that the generation was occuring event would near the equator. There is no indication of this observation at Narssarss' uaq Station, Greenland (61.2° Station (47.6° GOES 2 307.3° E) N and GOES 3 magnetic frequent correlated with geosynchronous . 314.2° E) or at St. Johns N from the NOAA Magnetograms satellites were also scanned. They showed activity, the none These Pc5. orbit but 252° at which satellites East and could be were in 225° East respectively. The lack of Pc5 activity at locations west of the SCATHA sector indicates a limit on the temporal and of the event. degrees of spatial extent The Pc5 appears to have been confined to 45 longitude in the SCATHA. 64 morning sector observed by DISCUSSION III. THE CHARACTER OF THE PCS A. II, the observable quantities characterizing In Chapter focusing on this Pc5 event were investigated by at the temporal and was shown to magnetic be of the event. The wave spatial center traveling a data taken Alfven wave by the guided line. The Alfven velocity was nearly 900 kilometers per second. A calculation of the Foynting vector field showed the wave was traveling northward. The electromagnetic occuring in a plane perpendicular The amplitude of the measured The gamma. the measured 2 to 3. and the (cm~^). studies. km/sec is electric reached field electric field was shown to be low by The period of the Pc5, period of The ion This The also is 3tt/4. 2.57 By requiring consistency of the data, at L=7, factor a was 224 seconds the wave was shown to be proportional to The plasma density (gm/cm^). magnetic field the perturbations was near magnetic field millivolts per meter. of the was shown to be magnetic field lagged the electric field by line. The 12 field perturbation estimated was to be 1.9 x 10"^-^ number density was determined to be 4.1 with consistent calculation consistent of with 65 previous magnetospheric the Alfven velocity previous studies. - 900 Most models of average magnetospheric plasma recently, empirical and Fast Mode and field data were developed to study Alfven wave speeds [Ref. densities of and Alfven 3-5 (cm"^), wave speeds models These 27]. predict plasma temperatures of 500 - plasma of 30-100 ev 1000 km/sec at L = 7.0 in the morning sector of the magnetosphere. SPATIAL EXTENT OF THE PCS B. The most interesting factor in packetized nature of the this event Pc5 is the micropulsation resonances through The breadth this sector of the magnetosphere. and location in these regions is presented in Table 7. TABLE 7 RESONANCE PACKET LOCATION AND SIZE Width ID t (UT) (km) A 4.66 5.25 5.84 6.26 6.80 7.46 The (° C D E P factor, in Table L N) 7.38 7.50 7.45 7.29 6.96 6.11 5300 5300 4200 3300 3600 5400 B r Latitude 7 , 7.8 7.5 7.2 6.9 6.7 6.4 Local Time 2:45 3:23 3:54 4:21 4:55 5:42 r 0.45 0.50 0.32 1.00 0.72 0.49 is a normalized resonance strength for each region, which is the ratio of the electric field amplitude packet. in a region to the electric field in the D These resonance regions are seperated by sectors of low resonance which vary in distance from 1200 kilometers to 3600 kilometers. 66 C. UNRESOLVED ISSUES A complete understanding of vector description of this event There are significant data. the would require a aspects of the Pc5 which were neglected by this study. is the One effect that the nutation of the spacecraft spin axis be seen The nutation effect can has on the raw data. as a small pulsation in each component of the magnetic field data Another in Figure 8. smaller component direction, B^. 4 aspect of the the is which Pc5 significance of the the radial is in The B^ component has an average amplitude of This component has a small effect on the amplitude gamma. of the Pc5 magnetic field, but the rotational motion of has a significant effect on the field. A study that included this component would provide a more realistic description of the Pc5 event. A most difficult aspect, who follows this study, is character of such as the separation of the spatial from the temporal description which the event this study provides. which is left for the student Many of the effects seen in variation of the sinusoidal the data, the resonance in each packet, have been described but not explained. D RECOMMEND AT I ONS 1. not be The spatial and temporal determined by SCATHA alone. known if local dawn was a extent of this Pc5 could Specifically, it is not boundary of the Pc5 or that the Pc5 ended at all locations at 6:56 UT. The radial boundaries 67 of the event are also left been a SCATHA passed ended when the Pc5 coincidence, but it could major characteristic available from the European resolution the a satellite that was GEOS-2 satellite) conjugate data may be answer (such provide an SCATHA could of be a This may have 6.6. L = A correlation with of this phenomenon. East of The observation of unresolved. ground station . Better time data would determine the location of the generating mechanism. 2. Approximate densities highest of resonance, information made were calculated in the region the available by wealth The packet. D SCATHA provides of an area for further study into the magnetospheric plasma profile between 5 . 5 Re and 7 3. The theoretical . 5 models presently available describe standing and compressional Alfven Since this event waves. provides extensive data from a traveling wave event, further investigation into this area of micropulsation theory is warranted. 4. Theorists have recently shown great interest in understanding the resonance conditions for Alfven waves. emphasized in this resonance conditions in the sphere is displayed the paper, packetized morning sector vividly by the observations should be used to improve Alfven wave resonance. 68 As nature of the of the magneto- SCATHA data. These the understanding of CONCLUSIONS IV. Observations of 8.0 in L = to Pc5 event occuring between L = . 6 and with kilometers regions spanning resonance Hydromagnetic 5000 6 sector of July 29, 1979, at 7° N, the pre-dawn were reported. 3000 a separated by 2400 centers kilometers were identified. shown to x 10"^-^ be 1.92 resonance region was the highest The plasma density in gm/cm-^ shown to be in phase with the electric at kev, and 9 with the kev 5 magnetic magnetic field by Particle data The The shown to be in phase kev 47 By from the UCSD electrostatic analyzers was checking electric of cross data was electric field comparing was shown to be data this predictions, the amplitude of data lagged the ions assumed to be a projection of the perturbation electric field antenna. Ion fluxes . radians. effective means shown to be an field data. tt/2 field electrons, were field. at 40 ev was Ion flux . a with measured the factor of 2-3 onto SCATPiA's density ion electric field too low to be consistent with the complete set of data (this is considered to be a small error) The periods of the micropulsations, between L = 6.3 and 7.7, were shown to be proportional to the fourth power of L, which supports present models 69 of resonant Alfven wave activity in the magnetosphere. Alfven velocities were shown to be nearly 900 kilometers per second within high resonance regions of the event. electromagnetic The perpendicular to pulsations the magnetic magnetic field lagged field line. electric the were field in a In the Pc5 by plane , the The 3n/4. Poynting vector was shown to be in the direction of the main magnetic field traveling Alfven conjugate ground confirming vector, Simultaneous wave. stations that indicated that the wave was a observations by the generation could be occurring at the equator. The unique packetized resonance regions exhibited by this PCS as well as the non-classical wave character of this event indicates that further data from SCATHA is warranted. 70 theoretical study utilizing LIST OF REFERENCES Springer- 1. Jacobs, J. A., Geomagnetic Micropulsations Verlag Berlin, 1970. 2. Stewart, B., "On the Great Magnetic Distrubance which which extended from August 27 to September 7, 1858," Transcripts of the Royal Society of London v 423, , . , 1861. 3. Barfield, J. N. and R. L. McPherron, "Statistical Characteristics of Storm Associated Pc5 Micropulsations Observed at the Synchronous Equatorial Orbit," Journal of Geophysical Research v. 77, pp. 4720-4733, , 1972. 4. Barfield, J. N. R. L. McPherron, P. J. 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